JP2020148460A - Non-destructive inspection measurement system and non-destructive inspection measurement method - Google Patents

Abstract

To provide a non-destructive inspection measurement system capable of measuring dimensions of a subject body.SOLUTION: A non-destructive inspection measurement system 10 includes: an excitation coil 113 that excites a subject body; a detection coil 121 that outputs a magnetic field change produced in the subject body; and a measurement device 3 that applies a sine wave signal or a composite signal of a different frequency to the exciting coil 113, detects a voltage from the detection coil 121, and measures dimensions t2 of the subject body. The measurement device comprises: a calibration gradient calculation unit 310 that measures a voltage from the detection coil 121 for each dimension t2 for a plurality of portions of the subject body whose dimensions t2 are known and different, and calculates a slope of a straight line connecting at least two measurements on an amplitude ratio-phase difference plane from the amplitude ratio and phase difference between the voltage and a reference voltage; a calibration unit that constructs simultaneous equations from the relation with values based on the gradient calculated for the dimension t2 for each of the plurality of dimensions t2; and an estimation unit that estimates the dimension t2 at the time of measuring the dimension t2.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-destructive inspection measurement system and a non-destructive inspection measurement method.

As shown in Patent Documents 1 to 6, in a vortex flaw detector using electromagnetic induction, a sine wave generator, a drive circuit for driving an exciting coil, a sensor composed of an exciting coil and a detection coil, and an amplification for amplifying the output of the detection coil. An apparatus composed of an amplifier circuit including a circuit and a synchronous detection circuit has been proposed and used.

It is widely practiced to measure the dimensions of a member provided inside a subject by a device as described above.
For example, Patent Document 7 discloses the following calibration device for a non-destructive inspection and measurement system. The calibration device of the non-destructive inspection measurement system applies a sine wave signal or a composite signal consisting of a plurality of sine waves having different frequencies to the exciting coil, the detection coil, and the exciting coil to excite the tube body, and detects the sine wave. It includes a computer that detects changes in the voltage output from the coil. The calibration device calibrates the detection result in the computer by incorporating the amplitude and phase difference of the voltage change output from the detection coil into the simultaneous equations as variables at a plurality of calibration points whose thickness is known in the tube body. This calibration device makes a plurality of calibration conditions different at each calibration point, and incorporates the amplitude and phase difference of the voltage change output from the detection coil under each calibration condition into a simultaneous equation to perform calibration.

Table 8 shows, for example, the experimental results of the prior art shown in Patent Document 7 above. The subject in this experiment includes an outer can and an inner can. Both the outer can and the inner can are formed in a kiln shape, the inner can is provided inside the outer can, and the inner can cannot be seen from the outside. In this experiment, the thickness of the inner can is measured.

ここで、係数ａ、ｂ、定数項ｃは、較正として、内缶の厚さｔ２が既知の３点（ｔ２１、ｔ２２、ｔ２３）において、実際に内缶の厚さｔ２を測定し、その各々における、振幅比ｘ、位相差ｙ、内缶の厚さｔ２の測定値の組み合わせ（ｘ１、ｙ１、ｔ２１）、（ｘ２、ｙ２、ｔ２２）、（ｘ３、ｙ３、ｔ２３）を上式に入力した、次の数式７として示される連立方程式を解くことにより、決定することができる。

表８において、「振幅比３３Ｈｚ」、「位相差３３Ｈｚ（ｒａｄ）」、「ｔ２較正値（ｍｍ）」の欄の第１行、第２行、及び第３行の各々は、上記の（ｘ１、ｙ１、ｔ２１）、（ｘ２、ｙ２、ｔ２２）、（ｘ３、ｙ３、ｔ２３）のそれぞれの組み合わせの実際の数値を記載したもので、上記の連立方程式を表形式で表したものである。
この連立方程式を解いて求めた係数ａ、ｂ、定数項ｃの値は、表８中のａ、ｂ、ｃと示されたそれぞれの欄に記載されている。 The estimation formula for estimating the inner can thickness t2 with the amplitude ratio x and the phase difference y can be formulated as the following formula 6 using the coefficients a and b and the constant term c.

Here, the coefficients a, b, and the constant term c actually measure the inner can thickness t2 at three points (t21, t22, t23) where the inner can thickness t2 is known as calibration, and each of them. The combination of the measured values of the amplitude ratio x, the phase difference y, and the thickness t2 of the inner can (x1, y1, t21), (x2, y2, t22), (x3, y3, t23) is input to the above equation. , Can be determined by solving the simultaneous equations shown as the following equation 7.

In Table 8, each of the first row, the second row, and the third row in the columns of "amplitude ratio 33 Hz", "phase difference 33 Hz (rad)", and "t2 calibration value (mm)" is the above (x1). , Y1, t21), (x2, y2, t22), (x3, y3, t23), and the actual numerical values of each combination are described, and the above simultaneous equations are expressed in tabular form.
The values of the coefficients a, b and the constant term c obtained by solving this simultaneous equation are described in the respective columns shown as a, b and c in Table 8.

More specifically, in this experiment, the estimated thickness is calibrated using the three-dimensional simultaneous equations shown as Equation 8. That is, when the ambient temperature is 10.4 ° C., the gap between the inner can and the outer can is 80 mm and the thickness t2 of the inner can is 35 mm and 25 mm, and the gap Gap is 70 mm and the thickness of the inner can. In each of the cases where t2 is 35 mm, the amplitude ratio and the phase difference are calculated, and these calculation results are substituted into the formula 7 and incorporated as the next formula 8.

In the above equation 8, the coefficients a and b and the constant term c are used, and in each result, the value obtained by multiplying the amplitude ratio by the coefficient a, the value obtained by multiplying the phase difference by the coefficient b, and the constant term c. Is added, and the equation is formulated so that this matches the known thickness t2.
By solving these three equations as simultaneous equations, the values of the unknowns a, b, and c can be obtained as shown in Table 8. Using the values of the coefficients a and b and the constant term c, assuming that the amplitude ratio is x and the phase difference is y, the following estimation formula for estimating the thickness t2 of the inner can is formulated.

FIG. 23 is an example in which the thickness t2 of the inner can is estimated and measured based on the above estimation formula, and is a graph showing the measurement result when the ambient temperature is 10.4 ° C. FIG. 24 is a graph in which the measurement results when the ambient temperature is 11.4 ° C. are added with broken lines to FIG. 23.

Japanese Patent No. 3735499 Japanese Patent No. 3266128 Japanese Unexamined Patent Publication No. 2010-48552 Japanese Patent No. 3896489 Japanese Unexamined Patent Publication No. 2010-54352 Japanese Patent No. 4756409 Public relations of JP-A-2018-59804

In FIG. 23, when the thickness t2 of the inner can is 35 mm, an accurate value is shown, but when the value of the interval Gap changes, the value becomes inaccurate. Further, as shown in FIG. 24, the value becomes even more inaccurate when the ambient temperature rises to 11.4 ° C.

As described above, in the conventional apparatus, it is required to reduce the influence of the measurement conditions when measuring the dimensions of the subject body provided in the subject.
Examples of the measurement conditions include the distance and distance of the subject body from the outer surface of the subject or the members constituting the outer surface, and the temperature. That is, as shown in FIGS. 23 and 24, the accuracy of the measurement result may be reduced by changing the interval Gap and the temperature.
Especially with regard to distance, there are many situations in which it is not possible to grasp this when measuring the dimensions of the subject body. In such a case, for example, when the subject is provided with a tubular subject body and an outer body provided outside the subject body and covering the outside of the subject body, the influence of the outer body. It is assumed that the thickness of the subject body is measured except for. Alternatively, when the subject is a double can body composed of an outer can and an inner can as described in the above experiment, the distance between the outer can and the inner can cannot be observed from the outside. It is also assumed that the thickness of the inner can, which is the main body of the subject, is accurately measured. Furthermore, when the subject is reinforced concrete, the thickness of the reinforcing bar that is the main body of the subject can be accurately determined under the condition that the distance between the concrete surface and the reinforcing bar, that is, the amount of "fog" in the industry terminology is unknown. A situation like measuring is assumed.
In this way, even when the measurement conditions, particularly the distance and spacing of the subject body from the outer surface of the subject or the members constituting the outer surface cannot be grasped, the dimensions of the subject body can be accurately grasped. Is desired.

The problem to be solved by the present invention is to provide a non-destructive inspection measurement system and a non-destructive inspection measurement method capable of measuring the dimensions of the subject body provided in the subject with high accuracy by reducing the influence of measurement conditions. It is to be.

The present invention employs the following means in order to solve the above problems. That is, the present invention outputs an exciting coil provided in the subject to excite the subject body and a voltage corresponding to a change in the magnetic field generated in the subject body when the subject body is excited by the excitation coil. A sine wave signal or a composite signal composed of a plurality of sine waves having different frequencies is applied to the detection coil to be performed and the excitation coil in order to excite the subject body, and the voltage output from the detection coil is detected. A non-destructive inspection measurement system including a measuring device for measuring the dimensions of the subject body, wherein the measuring device is used for a plurality of parts of the subject body whose dimensions are known and different. The voltage output from the detection coil is measured under each of a plurality of different measurement conditions for each of the dimensions, and the amplitude ratio and phase difference between this and the reference voltage are calculated, and the amplitude ratio and the phase difference are set to 2. A calibration time gradient calculation unit that obtains a straight line connecting points corresponding to at least two measurement results on an amplitude ratio-phase difference plane as an axis and calculates the gradient of the straight line, and the relevant dimension for each of the plurality of dimensions. Based on the gradient, a simultaneous equation is constructed from the relationship between the dimension and the value calculated for the dimension based on the gradient, and the dimension is estimated at the time of measuring the dimension based on the solution. It is provided with a calibration unit for formulating an estimation formula using the set value as a variable, and a measurement unit for estimating and measuring the dimensions of the part to be measured of the subject body based on the estimation formula. Provides a non-destructive inspection and measurement system.
According to the above configuration, before measuring the dimensions of the part to be measured of the subject body, for a plurality of parts having known and different dimensions, each of the plurality of different measurement conditions for each dimension can be used. The voltage output from the detection coil is measured, the amplitude ratio and phase difference between this and the reference voltage are calculated, and at least two measurement results on the amplitude ratio-phase difference plane with the amplitude ratio and phase difference as the two axes. Find the straight line connecting the points corresponding to, and calculate the slope of the straight line. If the measurement conditions are different when the dimensions are the same, the amplitude ratio and the phase difference are generally in a proportional relationship. Therefore, when the gradient obtained in this way for each dimension, that is, the proportional relationship is shown as a straight line, The slope is a value in which the influence of the measurement conditions is suppressed.
When actually estimating and measuring the dimensions of the part to be measured of the subject body, solve the simultaneous equations constructed from the relationship between the dimensions and the value based on the gradient calculated for the dimensions. Therefore, the estimation formula is formulated, and the dimensions are obtained based on this.
Therefore, it is possible to reduce the influence of the measurement conditions and measure the dimensions of the subject body provided in the subject with high accuracy.

In one aspect of the invention, the calibrator, for each of the plurality of dimensions, represents the relationship between the dimension and a value based on the gradient calculated for the dimension, of multiple elements. By formulating equations and solving them as simultaneous equations, a coefficient representing the relationship between the dimensions and the value based on the gradient is calculated, and the coefficient is applied using the value based on the gradient as the variable. By doing so, the estimation formula is formulated.
According to the above configuration, the above non-destructive inspection and measurement system can be appropriately realized.

In another aspect of the present invention, the measuring unit measures the voltage output from the detection coil as the measurement voltage with respect to the portion to be measured of the subject body, and this and the reference voltage. The measurement amplitude ratio and the measurement phase difference, which are the amplitude ratios and phase differences of, are calculated, and the measurement time gradient, which is the gradient on the amplitude ratio-phase difference plane corresponding to these, is calculated, and the measurement time gradient is calculated. By substituting the value based on the above into the variable of the estimation formula, the dimension is calculated and measured.
According to the above configuration, the above non-destructive inspection and measurement system can be appropriately realized.

In another aspect of the present invention, the calibration time gradient calculation unit further calculates the intersections between the straight lines obtained for each of the plurality of dimensions, and the measurement unit is on the amplitude ratio-phase difference plane. The gradient of the straight line connecting the measurement points and the intersections corresponding to the measurement amplitude ratio and the measurement phase difference in the above is calculated as the measurement gradient.
According to the above configuration, the above non-destructive inspection and measurement system can be appropriately realized.

In another aspect of the present invention, the measurement condition includes the outer surface of the subject or the distance from the member constituting the outer surface to the subject body.
According to the above configuration, the influence of the distance from the outer surface of the subject or the member constituting the outer surface to the subject body is reduced, and the subject body provided in the subject with high accuracy. It is possible to measure the dimensions of.

In another aspect of the present invention, the calibration gradient calculation unit applies a frequency different from the frequency of the sinusoidal signal or the composite signal applied to the exciting coil when calculating the gradient to the exciting coil. Then, the voltage output from the detection coil is measured, and the different frequency amplitude ratio, which is the amplitude ratio with the reference voltage, or the different frequency phase difference, which is the phase difference with the reference voltage, is calculated. The calibration unit has a relationship between the dimension and the value based on the gradient calculated for the dimension, and the different frequency amplitude ratio or the different frequency phase difference for each of the plurality of dimensions and temperatures. The simultaneous equations are constructed from the above, and the estimation equations are formulated based on the solution.
According to the above configuration, the gradient calculation unit at the time of calibration applies a frequency different from the frequency of the signal applied to the exciting coil to the exciting coil when calculating the gradient, and measures the voltage output from the detection coil. The different frequency amplitude ratio, which is the amplitude ratio between this and the reference voltage, or the different frequency phase difference, which is the phase difference from the reference voltage, is calculated and reflected in the simultaneous equations. At different frequencies, the amplitude or phase difference is affected differently by the eddy current, so by constructing and solving simultaneous equations that reflect the amplitude ratio or phase difference of different frequencies, the effect of temperature can be appropriately applied. It is possible to formulate an estimation formula that takes into consideration.
Therefore, it is possible to reduce the influence of temperature and measure the dimensions of the subject body provided in the subject with high accuracy.

In another aspect of the present invention, the subject body is a plate, the dimensions are the thickness of the plate, and the value based on the gradient is the gradient, in the simultaneous equations. The dimensions and the gradient are in a proportional relationship.
According to the above configuration, when the subject body is a plate formed in a flat plate shape or a kiln shape, the thickness thereof can be measured with high accuracy.

In another aspect of the present invention, the subject body is a rod with a circular cross section, and the dimension is the square of the difference between the diameter of a circle having a reference size and the diameter of the cross section of the rod. Yes, in the simultaneous equations, the dimensions and the values based on the gradient are in a proportional relationship.
When the subject body is a rod with a circular cross section, when the magnetic field lines generated by the exciting coil enter the rod body, a magnetic field is formed in the direction opposite to the direction of the magnetic field formed by the invading magnetic flux. Since the eddy current flows, the magnetic field lines are canceled by the eddy current and do not enter the inside of the rod body, but flow near the surface of the rod body and exit to the side opposite to the intrusion point. Therefore, in the case of a rod with a circular cross section, the slope, that is, the slope when the proportional relationship between the amplitude ratio and the phase difference is shown as a straight line, is not the diameter of the rod, but a circle of some reference size. When specified, the relationship is proportional to the square of the difference between the diameter of this circle and the diameter of the cross section of the rod to be measured.
Therefore, according to the above configuration, when the subject body is a rod having a circular cross section, its diameter can be measured with high accuracy.

In another aspect of the present invention, the subject body is a rod with a quadrangular cross section, and the dimensions are the length of the diagonal of a quadrangle of a reference size and the length of the diagonal of the cross section of the rod. It is the square of the difference, and in the simultaneous equations, the dimension and the value based on the gradient are in a proportional relationship.
When the subject body is a rod with a square cross section, when the magnetic field lines generated by the exciting coil enter the rod, a magnetic field is formed in the direction opposite to the direction of the magnetic field formed by the invading magnetic flux. Since the eddy current flows, the magnetic field lines are canceled by the eddy current and do not enter the inside of the rod body, but flow near the surface of the rod body and exit to the side opposite to the intrusion point. Therefore, in the case of a rod with a quadrilateral cross section, the slope, that is, the slope when the proportional relationship between the amplitude ratio and the phase difference is shown as a straight line, is this quadrangle when a quadrangle of some reference size is defined. The relationship is proportional to the square of the difference between the length of the diagonal line and the length of the diagonal line of the cross section of the rod to be measured.
Therefore, according to the above configuration, when the subject body is a rod having a quadrangular cross section, its thickness can be measured with high accuracy.

In another aspect of the present invention, for a plurality of parts of the subject body whose dimensions are known and different, the length of the rod and the gradient calculation unit at the time of calibration are calculated for each of the plurality of dimensions. A straight line connecting points corresponding to at least two measurement results on a length-gradient plane with the gradient as two axes is obtained, and a quadratic gradient which is the gradient of the straight line is used as a value based on the gradient. A calibrated quadratic gradient calculation unit for calculation is provided, and the calibrating unit constructs a simultaneous equation from the relationship between the dimension and the quadratic gradient calculated for the dimension for each of the plurality of dimensions. , The estimation formula is formulated based on the solution.
When the subject body is a rod and the length of the rod is short, the dimensions are the length-gradient with the length of the rod and the gradient as two axes, rather than the gradient calculated as described above. The relationship is proportional to the quadratic gradient, which is the gradient of the straight line connecting the points, corresponding to at least two correspondences between the length and the gradient on the plane.
According to the above configuration, since the simultaneous equations are constructed from the relationship between the dimension and the quadratic gradient calculated for the dimension for each of the plurality of dimensions, the estimation formula includes the dimension. The relationship of the quadratic gradient is reflected.
Therefore, when the subject body is a rod and the length of the rod is short, the influence of the measurement conditions can be reduced and the dimensions of the subject body provided in the subject can be measured with high accuracy. is there.

Further, the present invention outputs an exciting coil provided in the subject to excite the subject body and a voltage corresponding to a change in the magnetic field generated in the subject body when the subject body is excited by the excitation coil. A sine wave signal or a composite signal composed of a plurality of sine waves having different frequencies is applied to the detection coil to be excited and the excitation coil to excite the subject body, and the voltage output from the detection coil is detected. A non-destructive inspection measuring method for measuring the dimensions of the subject body, wherein the dimensions of the subject body are known and different, and a plurality of different measurement conditions are provided for each of the plurality of dimensions. The voltage output from the detection coil is measured in each of the above, and the amplitude ratio and phase difference between this and the reference voltage are calculated, and the amplitude ratio and the phase difference are on the two axes of the amplitude ratio-phase difference plane. The straight line connecting the points corresponding to at least two measurement results in the above is obtained, the slope of the straight line is calculated, and the slope of the straight line is calculated based on the dimension and the gradient calculated for the dimension. A simultaneous equation is constructed from the relationship with the obtained value, and based on the solution, an estimation formula is formulated with the value based on the gradient as a variable to estimate the dimension when measuring the dimension, and the estimation is performed. Provided is a non-destructive inspection measurement method for estimating and measuring the dimensions of a portion of the subject body to be measured based on the formula.
According to the above configuration, before measuring the dimensions of the part to be measured of the subject body, for a plurality of parts having known and different dimensions, each of the plurality of different measurement conditions for each dimension can be used. The voltage output from the detection coil is measured, the amplitude ratio and phase difference between this and the reference voltage are calculated, and at least two measurement results on the amplitude ratio-phase difference plane with the amplitude ratio and phase difference as the two axes. Find the straight line connecting the points corresponding to, and calculate the slope of the straight line. If the measurement conditions are different when the dimensions are the same, the amplitude ratio and the phase difference are generally in a proportional relationship. Therefore, when the gradient obtained in this way for each dimension, that is, the proportional relationship is shown as a straight line, The slope is a value in which the influence of the measurement conditions is suppressed.
When actually estimating and measuring the dimensions of the part to be measured of the subject body, solve the simultaneous equations constructed from the relationship between the dimensions and the value based on the gradient calculated for the dimensions. Therefore, the estimation formula is formulated, and the dimensions are obtained based on this.
Therefore, it is possible to reduce the influence of the measurement conditions and measure the dimensions of the subject body provided in the subject with high accuracy.

According to the present invention, it is possible to provide a non-destructive inspection measurement system and a non-destructive inspection measurement method capable of measuring the dimensions of a subject body provided in a subject with high accuracy while reducing the influence of measurement conditions. ..

It is a figure which shows the structure of the nondestructive inspection measurement system in embodiment of this invention. It is a schematic plan view of the sensor of the non-destructive inspection measurement system in the said embodiment. 6 is a graph showing the relationship between the amplitude ratio and the phase difference when the frequency is 33 Hz and the temperature is 10.4 ° C. in the example using the non-destructive inspection measurement system in the above embodiment. 6 is a graph showing the relationship between the amplitude ratio and the phase difference when the frequency is 33 Hz and the temperatures are 10.4 ° C. and 11.4 ° C. in the example using the non-destructive inspection measurement system in the above embodiment. 6 is a graph showing the relationship between the amplitude ratio and the phase difference when the frequency is 39 Hz and the temperatures are 10.4 ° C. and 11.4 ° C. in the example using the non-destructive inspection measurement system in the above embodiment. 6 is a graph showing the relationship between the amplitude ratio and the phase difference when the frequency is 57 Hz and the temperatures are 10.4 ° C. and 11.4 ° C. in the example using the non-destructive inspection measurement system in the above embodiment. 6 is a graph showing the relationship between the amplitude ratio and the phase difference when the frequency is 69 Hz and the temperatures are 10.4 ° C. and 11.4 ° C. in the example using the non-destructive inspection measurement system in the above embodiment. 6 is a graph showing the relationship between the amplitude ratio and the phase difference when the frequency is 87 Hz and the temperatures are 10.4 ° C. and 11.4 ° C. in the example using the non-destructive inspection measurement system in the above embodiment. It is a graph which shows the measurement result in the Example using the non-destructive inspection measurement system in the said embodiment. It is a flowchart of the non-destructive inspection measurement method using the non-destructive inspection measurement system in the said embodiment. It is a figure which shows the structure of the nondestructive inspection measurement system in the 1st modification of the said embodiment. It is a graph which shows the measurement result in the Example using the non-destructive inspection measurement system in the 1st modification of the said Embodiment. It is a figure which shows the structure of the nondestructive inspection measurement system in the 2nd modification of the said embodiment. It is a schematic plan view of the sensor of the non-destructive inspection measurement system in the 2nd modification of the said embodiment. It is a graph which shows the relationship between the amplitude ratio and the phase difference in the example using the non-destructive inspection measurement system in the 2nd modification of the said embodiment. It is a partially enlarged view of FIG. It is explanatory drawing of the operation of the non-destructive inspection measurement system in the 2nd modification of the said embodiment. It is a graph which shows the measurement result when the distance between the outer surface of a subject and the body of a subject is 36.5 mm in the example using the non-destructive inspection measurement system in the 2nd modification of the said embodiment. It is a graph which shows the measurement result when the distance between the outer surface of a subject and the body of a subject is 56.5 mm in the example using the non-destructive inspection measurement system in the 2nd modification of the said embodiment. It is a figure which shows the structure of the nondestructive inspection measurement system in the 3rd modification of the said embodiment. It is a graph which shows the relationship between the length and the gradient of the subject body in the example using the non-destructive inspection measurement system in the 3rd modification of the said embodiment. It is a graph which shows the measurement result in the Example using the non-destructive inspection measurement system in the 3rd modification of the said Embodiment. It is a graph which shows the result when the frequency is 33Hz, and the temperature is 10.4 ° C. in the example using the prior art. It is a graph which shows the result when the frequency was 33Hz, and the temperature was 10.4 ° C. and 11.4 ° C. in the example using the prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The non-destructive test measurement system in the present embodiment has an exciting coil for exciting the subject body provided in the subject and a voltage corresponding to a change in the magnetic field generated in the subject body when the subject body is excited by the exciting coil. A sine wave signal or a composite signal consisting of multiple sine waves with different frequencies is applied to the detection coil that outputs the above and the excitation coil to excite the subject body, and the voltage output from the detection coil is detected. , A measuring device for measuring the dimensions of the subject body, and the measuring device includes a plurality of different measurement conditions for each of the plurality of dimensions for a plurality of parts where the dimensions of the subject body are known and different. For each of these, measure the voltage output from the detection coil, calculate the amplitude ratio and phase difference between this and the reference voltage, and at least on the amplitude ratio-phase difference plane with the amplitude ratio and phase difference as the two axes. Based on the calibration time gradient calculation unit that obtains the straight line connecting the points corresponding to the two measurement results and calculates the gradient of the straight line, the relevant dimension for each of a plurality of dimensions, and the gradient calculated for the relevant dimension. A calibration unit that constructs a simultaneous equation from the relationship with the value set to, and estimates the dimension at the time of measuring the dimension based on the solution, and formulates an estimation formula with the value based on the gradient as a variable. Based on the formula, it is provided with a measuring unit that estimates and measures the dimensions of a portion of the subject body to be measured.

FIG. 1 is a diagram showing a configuration of a non-destructive inspection measurement system according to an embodiment of the present invention. FIG. 2 is a schematic plan view of a sensor of the non-destructive inspection measurement system according to the present embodiment.
The non-destructive inspection measurement system 10 in the present embodiment measures the dimensions of the subject body 202 provided in the subject 2.
The subject body 202 is a plate body in the present embodiment. In particular, in the present embodiment, the subject 2 to be inspected has a two-layer structure including an outer can 201 having a thickness t1 and an inner can (subject body) 202 having a thickness t2 separated by a gap Gap. There is. Both the outer can 201 and the inner can 202 are formed in a kiln shape, the inner can 202 is provided inside the outer can 201, and the inner can 202 is invisible from the outside. In the present embodiment, the non-destructive inspection measurement system 10 measures the thickness (dimension) t2 of the inner can 202.
The subject 2 may be any conductive metal body such as stainless steel or general steel, and may have a flat plate or a curved plate in shape.
In addition, in FIG. 1, only a part of the cross-sectional structure of the subject 2 is shown.

The non-destructive inspection measurement system includes a sensor 1 and a measuring device 3.
The sensor 1 includes a detector 12 and six exciters 11.
The detector 12 is provided near the center of the housing 1a forming the sensor 1 when the sensor 1 is viewed in a plan view. The detector 12 includes a detection coil 121. The detection coil 121 is an air-core coil in this embodiment. The sensitivity of the detection coil 121 increases when a magnetic core such as ferrite is used. However, since the magnetic core attracts magnetic field lines, it disturbs the natural magnetic field line distribution and its relative magnetic permeability has temperature characteristics. , The air-core coil has better characteristics.
In the detector 12, when the lower surface 1b of the housing 1a of the sensor 1 is provided along the outer surface 201a of the outer can 201, the central axis C12 of the detection coil 121 is in the normal direction of the outer surface 201a of the subject 2. It is provided in the sensor 1 so as to match.

The exciter 11 is provided so as to surround the detector 12 when the sensor 1 is viewed in a plane as shown in FIG. The exciter 11 includes an exciting core 111, a feedback coil 112, and an exciting coil 113.
The exciting core 111 is made of a magnetic material such as a laminated silicon steel plate. The exciting core 111 has a shape in which a rod-shaped member is bent at two places, and the first core portion 111a, the second core portion 111b, and the third core portion 111c are formed with the bent portion as a boundary. It is formed. The first core portion 111a and the third core portion 111c are formed so as to be bent so as to be inclined in the same direction with respect to the second core portion 111b located in the middle. In the exciting core 111, the second core portion 111b is substantially parallel to the lower surface 1b of the housing 1a, and the tips of the first core portion 111a and the third core portion 111c approach the lower surface 1b of the housing 1a. It is positioned in the housing 1a so as to do so. The first core portion 111a is provided so as to be located closer to the detector 12 than the third core portion 111c. In this way, a total of six exciters 11 are arranged radially around the detector 12 so that the magnetic flux is concentrated directly under the detector 12.

A feedback coil 112 is wound around the first core portion 111a of the exciter 11.
Each of the exciting coils 113 includes a first exciting coil 113a, a second exciting coil 113b, and a third exciting coil 113c.
The first exciting coil 113a is wound around the feedback coil 112. With the configuration of the first core portion 111a as described above, the central axis C13 of the first exciting coil 113a is provided so as to intersect the central axis C12 of the detection coil 121 on the subject 2 side.
The first exciting coil 113a, the second exciting coil 113b, and the third exciting coil 113c of all the exciters 11 are wound in the same direction and are connected in series with each other. Although each exciting coil 113 has been described as having three exciting coils 113a, 113b, and 113c, these may be integrally formed.
Further, the feedback coils 112 of all the exciters 11 are connected in series with each other. The feedback coil 112 and the exciting coil 113 are not connected.
In this way, the exciting coil 113 and the feedback coil 112 of the six exciters 11 are all additively connected in series in the same direction in terms of magnetic flux to provide a neutral grounded balanced input / output to improve noise resistance. It is configured.

In such a sensor 1, when the exciting coil 113 is excited, the exciting coil 113 excites the exciting core 111, whereby a magnetic flux is generated in the exciting core 111. The feedback coil 112 captures the magnetic flux generated in the exciting core 111. The resulting output captured by the feedback coil 112 is used as a reference voltage.
Further, the exciting coil 113 similarly excites the inner can 202 of the subject 2, thereby generating a magnetic flux in the inner can 202. The detection coil 121 captures the magnetic flux generated in the inner can 202. The output voltage captured by the detection coil 121 is compared with the reference voltage and used to measure the thickness t2 of the inner can 202. The detection coil 121 may be wound in a simple manner and may be grounded at the midpoint, but since the amount of magnetic flux captured differs depending on the winding radius, even if the center of the number of turns is grounded, the output is not completely balanced. Therefore, in the present embodiment, the bifilar winding is used to improve the noise resistance as a perfect balanced output.

In this way, the exciting coil 113 excites the subject body 202 provided in the subject 2. Further, the detection coil 121 outputs a voltage corresponding to the change in the magnetic field generated in the subject body 202 when the subject body 202 is excited by the excitation coil 113.

The measuring device 3 includes a digital-to-analog converter (DAC) 301, an analog-to-digital converter (ADC) 302, a power amplifier 303, a multiplexer 304, a computer 305, and a display / data acquisition unit 306.
The computer 305 digitally generates a composite signal of a single frequency or multiple frequency sinusoidal signal. The DAC 301 generates a computer 305 and converts the digitally synthesized signal into an analog signal. The power amplifier 303 amplifies the analog signal from the DAC 301 and supplies it to the first exciting coil 113a, the second exciting coil 113b, and the third exciting coil 113c of the sensor 1. The exciting coil 113 is excited by the alternating voltage by this analog signal. When the exciting coil 113 is excited, a magnetic field change occurs in the outer can 201 and the inner can 202, which are the subjects. The total magnetic field around the detection coil 121 changes due to the eddy current flowing in response to the change in the magnetic field of the outer can 201 and the inner can 202, and the voltage change including the change due to the eddy current is output from the detection coil 121. As described above, it is extremely difficult to distinguish and detect only the magnetic field change due to the eddy current, but the detection coil 121 detects the magnetic field change including the magnetic field change due to the eddy current.

As described above, when the first exciting coil 113a is excited, the feedback coil 112 captures the magnetic flux generated in the exciting core 111. The signal from the feedback coil 112 is transmitted to the ADC 302 via the multiplexer 304, converted into a digital signal by the ADC 302, and fed back processed by the computer 305 so as to keep the exciting magnetic flux constant.

The voltage generated in the detection coil 121 and the voltage output from the feedback coil 112 are input to the multiplexer 304. The ADC 302 converts the output of the multiplexer 304 into a digital signal and outputs it to the computer 305. Computer 305 performs measurement and analysis processing based on the output from ADC 302.
The computer 305 compares the voltage output from the detection coil 121 with the reference voltage, that is, the voltage output from the feedback coil 112, and calculates their amplitude ratio and phase difference. More specifically, the computer 305 calculates the amplitude ratio with the amplitude value of the output of the feedback coil 112 as the denominator and the amplitude value of the output of the detection coil 121 as the numerator. As a result, the influence of voltage fluctuations in the measurement system is suppressed. Similarly, the computer 305 calculates the difference between the output phase of the feedback coil 112 and the output phase of the detection coil 121 as the phase difference.
The display / data acquisition unit 306 displays and acquires data as a result of measurement and analysis processing in the computer 305.

When measuring the size, that is, the thickness of the subject body, that is, the inner can 202, using such a non-destructive inspection measurement system 10, the sensor 1 is moved along the outer surface 201a of the subject 2. The excitation coil 113 is excited by generating a sine wave signal or a composite signal composed of a plurality of sine waves having different frequencies by a computer 305 at a plurality of portions having a known thickness t2 of the inner can 202. The computer 305 calculates the amplitude ratio and phase difference of the voltage change output from the detection coil 121 in response to the excitation of the exciting coil 113.
It is the thickness t2 of the inner can 202 estimated from this amplitude ratio and phase difference that calculates the amplitude ratio and phase difference of the voltage output from the detection coil 121 with the feedback coil 112 in the portion where the thickness t2 is known. Is the purpose of calibrating the estimation result by comparing with the actual thickness of the measured part. Calibration will be described in detail later.
Here, when measurement is performed by making the frequencies of the sine wave signals different from each other, the plurality of sine wave signals are digitally generated by the computer 305, and the synthesized digital signal is converted into an analog signal by the DAC 301. The exciting coil 113 is excited via the power amplifier 303. The output of the detection coil 121 is substantially sampled by the multiplexer 304, held, converted into a digital signal by the ADC 302, subjected to a fast Fourier transform (FFT) process by the computer 305, and output as amplitude and phase difference for each frequency. Similarly, the output of the feedback coil 112 is also converted into a digital signal via the multiplexer 304 and the ADC 302, fast Fourier transformed by the computer 305, and output as amplitude and phase difference for each frequency. Finally, the amplitude is output as an amplitude ratio for each frequency with the amplitude corresponding to the output of the feedback coil 112 as the denominator and the amplitude corresponding to the output of the detection coil 121 as the numerator. Similarly, the phase difference is output as a phase difference for each frequency by calculating a phase difference corresponding to the output of the detection coil 121 with reference to the phase difference corresponding to the feedback coil 112. In the fast Fourier transform (FFT) of a general signal, it is necessary to insert a window function filter such as a humming window in order to prevent a discontinuity after sampling, but in this embodiment, the above When a plurality of sinusoidal signals are digitally generated by the computer 305, it is not a continuous wave, but a preamble that gradually rises exponentially from zero and a post that gradually falls exponentially to zero. Since it is possible to omit the insertion of the window function by using a burst signal provided with a post-amble, this is omitted.
As described above, by using the fast Fourier transform (FFT), it is possible to simultaneously detect the amplitude ratio and the phase difference of each frequency as a sine wave, so that the measurement efficiency is high.

In general, the waveform of a sine wave signal can be uniquely specified once the three constants of frequency, amplitude, and phase are determined. Therefore, the computer 305 uses a fast Fourier transform (FFT) as a waveform analysis processing method to calculate the amplitude and the phase.
A voltage value is usually taken as the amplitude, but the output of the detection coil 121 often fluctuates due to fluctuation factors such as temperature and voltage fluctuation. Therefore, in order to suppress fluctuations in the measurement system, as described above, by generalizing the amplitude ratio to the output of the detection coil 121 having the amplitude of the output voltage of the feedback coil 112 as the denominator. Highly accurate data acquisition is possible.
As for the phase, the phase difference between the input phase to the feedback coil 112 and the output of the detection coil 121 is represented by a radian.

Here, in the computer 305, the frequency sequence of each frequency of the generated sinusoidal signal is set to a prime number series having 3 as a base in order to prevent the so-called aliasing phenomenon in which the respective harmonics fall into the other frequency domain. In this embodiment, for example, the frequency is 33, 39, 57, 69, 87 Hz. The reason for avoiding around 50 and 60 Hz is to prevent the influence of power supply noise. Further, in the present embodiment, since the data of 8192 points is acquired as the fast Fourier transform (FFT), sampling is performed at a sampling frequency of 3 (Hz) × 8192 = 24,576 (Hz).

Next, the calibration in this embodiment will be described.
Before actually measuring the thickness t2 of the inner can 202 using the non-destructive inspection measurement system 10, it is necessary to calibrate the non-destructive inspection measurement system 10. In the calibration, the thickness t2 of the inner can 202 of the subject 2 and the output voltage of the detection coil 121 are measured by varying the Gap, which is the distance between the outer can 201 and the inner can 202, and the thickness t2 and the gap Gap are detected. This is done by examining the relationship with the output voltage of the coil 121. Therefore, ideally, if the subject 2 has a plurality of portions whose thickness t2 and interval Gap are known and different, calibration can be performed by examining the output voltage of the detection coil 121 at these portions. However, when the subject 2 does not have a portion satisfying such a condition, a simulated body in which the thickness t2 and the interval Gap can be changed is prepared, and calibration is performed using this.
In the present embodiment, the position of the subject body, that is, the inner can 202 in the subject 2, is set from the outer can 201, which is a member constituting the outer surface 201a of the subject 2, as described above. Although it is expressed by the interval Gap which is the distance to 202, it goes without saying that it may be expressed by the distance from the outer surface 201a of the subject 2, that is, the sum of the thickness t1 of the outer can 201 and the interval Gap.

In order to calibrate the non-destructive inspection measurement system 10 and estimate and measure the thickness t2 of the inner can 202 using the calibration result, the computer 305 uses the calibration time gradient calculation unit 310, the calibration unit 311 and the measurement unit. It is equipped with 312.

The calibration time gradient calculation unit 310 measures using the sensor 1 at a specific frequency, at a known first thickness t21 of the inner can 202, and at a known first distance Gap1 between the outer can 201 and the inner can 202. The amplitude ratio and the phase difference are calculated by the above method, and the amplitude ratio is plotted on the amplitude ratio-phase difference plane with the amplitude ratio on the horizontal axis and the phase difference on the vertical axis. Further, the calibration time gradient calculation unit 310 changed the gap Gap between the outer can 201 and the inner can 202 to a second gap Gap2 different from the first gap Gap1, and used the sensor 1 under the same conditions for the others. The amplitude ratio and phase difference are calculated by measurement and plotted on the amplitude ratio-phase difference plane. The calibration gradient calculation unit 310 calculates a first straight line connecting these two points plotted on the amplitude ratio-phase difference plane.
The calibration time gradient calculation unit 310 also has a known second thickness t22 different from the first thickness t21, and is measured by the sensor 1 at the third distance Gap3 between the outer can 201 and the inner can 202. Calculate the amplitude ratio and phase difference, and plot them on the amplitude ratio-phase difference plane. Further, the calibration time gradient calculation unit 310 changed the gap Gap between the outer can 201 and the inner can 202 to a fourth gap Gap4 different from the third gap Gap3, and used the sensor 1 under the same conditions for the others. The amplitude ratio and phase difference are calculated by measurement and plotted on the amplitude ratio-phase difference plane. The calibration gradient calculation unit 310 calculates a second straight line connecting these two points plotted on the amplitude ratio-phase difference plane.
In the above, the first interval Gap1 and the third interval Gap3, and the second interval Gap2 and the fourth interval Gap4 may be the same, but may be different.

Next, the calibration time gradient calculation unit 310 obtains the intersection P0 on the extension line of the first straight line and the second straight line.
Further, the calibration gradient calculation unit 310 calculates the gradient of the first straight line and the gradient of the second straight line on the amplitude ratio-phase difference plane.

As described above, the calibration time gradient calculation unit 310 measures the inner can 202 with different measurement conditions Gap1, Gap2, for each of the plurality of thicknesses t21 and t22 for a plurality of parts having a known and different thickness t2. Under each of the conditions Gap3 and Gap4, the voltage output from the detection coil 121 is measured, the amplitude ratio and phase difference between this and the reference voltage are calculated, and the amplitude ratio-phase difference with the amplitude ratio and phase difference as two axes. A straight line connecting points corresponding to at least two measurement results on a plane is obtained, and the gradient of the straight line is calculated.
Further, the calibration time gradient calculation unit 310 calculates the intersection P0 between the straight lines obtained for each of the plurality of thicknesses t21 and t22.
Further, the measurement condition includes the distance from the outer surface 201a of the subject 2 or from the member 201 constituting the outer surface 201a to the subject main body 202. In the present embodiment, this distance is the distance Gap between the outer can 201 and the inner can 202.

As will be described in detail later with reference to Examples such as FIG. 3, there is a proportional relationship between the thickness t2 of the inner can 202 and the gradient calculated with respect to the straight line corresponding to the thickness t2. To establish. That is, assuming that the gradient is x, a is a coefficient applied to the gradient, and b is a constant, the thickness t2 of the inner can 202 can be expressed by, for example, a linear equation of t2 = ax + b.
As described above, the calibration gradient calculation unit 310 calculates the gradient values corresponding to the plurality of thicknesses t21 and t22 of the inner can 202. Therefore, the calibration unit 311 substitutes the thicknesses t21 and t22 of the inner cans 202 and the values of the gradients corresponding to them into the above linear equations, respectively, to obtain a binary simultaneous equation with a and b as variables. To construct. The calibration unit 311 solves this and derives the values of a and b. By substituting the derived values of a and b into the above linear equation, the calibration unit 311 makes the gradient a variable, and when this is input, the thickness t2 of the inner can 202 can be calculated. To formulate.

In this way, the calibration unit 311 sets the gradients (gradients) calculated for the thicknesses t21 and t22 (dimensions) and the thicknesses t21 and t22 for each of the plurality of thicknesses t21 and t22 of the inner can 202. A simultaneous equation is constructed from the relationship with the (based value), and based on the solution, an estimation formula with a gradient as a variable is formulated to estimate the thickness t2 when measuring the thickness t2.
More specifically, the calibration unit 311 represents, for each of the plurality of thicknesses t21, t22 of the inner can 202, the relationship between the thicknesses t21, t22 and the gradient calculated for the thickness. A linear equation is formulated, and by solving these as simultaneous equations, a coefficient representing the relationship between the thickness t2 and the gradient is calculated, and an estimation equation is formulated by applying the coefficient with the gradient as a variable.
In this system of equations, the thickness and the gradient are in a proportional relationship.

When actually estimating and measuring the thickness t2 of the inner can 202, the measuring unit 312 operates and detects an arbitrary portion on the subject 2 whose thickness t2 is unknown. The output voltage from the coil 121 is measured as the measurement voltage, and the measurement amplitude ratio and the measurement phase difference, which are the amplitude ratio and the phase difference of the measurement voltage with the reference voltage, are calculated. The measurement unit 312 plots the measurement amplitude ratio and the measurement phase difference as measurement points on the amplitude ratio-phase difference plane, and the intersection P0 of this measurement point and the extension line of the first straight line and the second straight line. Calculate the measurement gradient, which is the gradient of the measurement straight line connecting the two. The measuring unit 312 calculates and measures the thickness t2 of the inner can 202 in the measured portion on the subject 2 by substituting the measurement gradient into the estimation formula established by the calibration unit 311.
In this case, if the gap Gap between the outer can 201 and the inner can 202 can be changed in the measured portion of the subject 2, the gradient in the amplitude ratio-phase difference plane may be obtained and substituted into the estimation formula. ..

In this way, the measuring unit 312 estimates and measures the thickness t2 of the portion of the inner can 202 to be measured based on the estimation formula.
More specifically, the measuring unit 312 measures the voltage output from the detection coil 121 as the measurement voltage with respect to the measurement target portion of the inner can 202, and measures the amplitude ratio and phase difference between this and the reference voltage. Calculate a certain measurement time amplitude ratio and measurement time phase difference, calculate the measurement time gradient which is the gradient on the amplitude ratio-phase difference plane corresponding to these, and substitute the measurement time gradient into the variable of the estimation formula. Calculate and measure the thickness.
Here, the measuring unit 312 calculates the gradient of the straight line connecting the measurement point and the intersection P0 corresponding to the amplitude ratio at the time of measurement and the phase difference at the time of measurement on the amplitude ratio − phase difference plane as the gradient at the time of measurement.

Next, more detailed behaviors of the calibration time gradient calculation unit 310, the calibration unit 311, and the measurement unit 312 as described above will be described together with an embodiment of the non-destructive inspection measurement system 10.

[Example 1]
As the detection coil 121 shown in FIG. 1, the detector 12 winds a PEW wire having a diameter of 0.20 mmΦ a total of 14,000 times as an air-core bifilar winding to obtain a midpoint ground equilibrium output and noise resistance. It has a strong structure. The reason for using the bifilar winding is that in the case of multi-layer winding, there is a difference in diameter between the start and end of winding, so that the magnetic flux captured differs. This is because the normal simple winding method using a single wire does not produce an equilibrium output even if the center of the number of turns is grounded. This is because the noise resistance performance can be improved because the output can be completely balanced by connecting the windings of the above in series and grounding the midpoint thereof.
The exciting core 111 of the exciter 11 is configured by laminating 100 directional silicon steel plates having a thickness of 100 um and a width of 10 mm, and winding a PEW wire having a diameter of 0.30 mmΦ 130 times as a feedback coil 112. are doing. A PEW wire having a diameter of 1 mmΦ is wound 200 times in total as the exciting coil 113 on the exciting core 111 and the feedback coil 112.
The overall dimensions of the sensor 1 are 160 mm in width, 440 mm in length, and 130 mm in height, and the sensor 1 is configured to be large as a sensor.
As the outer can 201 and the inner can 202 constituting the subject 2, a flat plate of stainless steel SUS304 having a width and a length of 800 mm was used. The thickness t1 of the outer can 201 was fixed at 30 mm. The inner can 202 has a structure in which a flat plate having a thickness of 25, 28, 30, 32, or 35 mm and having a thickness of t2 can be replaced. The gap Gap between the outer can 201 and the inner can 202 is configured to be variable to any of 70, 80, and 90 mm.

The computer 305 of the measuring device 3 is configured to generate a digital signal obtained by synthesizing sine waves having five frequencies of 33, 39, 57, 69, and 87 Hz as frequencies. This signal is converted into an analog signal via the DAC 301, output to the sensor 1 via the power amplifier 303, and used to drive the exciter 11.
The output voltage of the power amplifier 303 is 4V and the output current is about 0.35A, which drives six exciting coils 113 connected in series with each other.
In the measuring device 3, a fast Fourier transform (FFT) is performed. In the fast Fourier transform, it is necessary to sample 2 to the nth power data, so 8,192 points of data are acquired at a sampling frequency of 24,576 Hz and the fast Fourier transform is performed to perform the fast Fourier transform, and 33, 39, 57, 69. , The amplitude ratio and the phase difference were independently acquired at each of the five frequencies of 87 Hz. The reference of the amplitude and the phase is the output of the feedback coil 112, and the amplitude is acquired as the ratio to it, that is, the amplitude ratio, and the phase is acquired as the difference from it, that is, the phase difference. Hereinafter, in the data of the first embodiment, the amplitude ratio is described as, for example, A33 Hz (A: Amplitude, 33 Hz, an unknown number because of the ratio) and the phase difference P33 Hz (P: Phase, 33 Hz, unit: radian).
Both the DAC 301 and the ADC 302 of this embodiment employ a 16-bit system, and both have sufficient accuracy and accuracy.

FIG. 3 is an example of the measurement results, in which the temperature is 10.4 ° C., the frequency is 33 Hz, the thickness t1 of the outer can 201 is fixed to 30 mm, and the thickness t2 of the inner can 202 is 25, 28, 30, 32. The frequency was varied to 35 mm, the output voltage of the detection coil 121 was measured for each interval Gap of 70, 80, and 90 mm, and the amplitude ratio and phase difference between this output voltage and the reference voltage by the feedback coil 112 were calculated. It is plotted on an amplitude ratio-phase difference plane with the amplitude ratio on the horizontal axis and the phase difference on the vertical axis. Here, each of the measurement results having the same thickness t2 of the inner can 202 is located on the same straight line as shown by the alternate long and short dash line in FIG. 3 when connecting points having different intervals Gap. That is, different straight lines are generated correspondingly for each of the different thicknesses t2. These straight lines intersect at the intersection P01.
In FIG. 4, the graph of the temperature of 10.4 ° C. shown in FIG. 3 is shown by a straight line, and the same measurement as that of the temperature of 10.4 ° C. is performed even when the temperature is 11.4 ° C. The results are superimposed and shown by broken lines. It can be seen that even if the difference between the conditions of the straight line and the broken line in FIG. 4, that is, the temperature differs by only 1 ° C., the calculated amplitude ratio and phase difference fluctuate, and as a result, the measurement result of the thickness t2 changes. However, the change is translational. This indicates that the temperature coefficient of volume resistivity of stainless steel SUS304 is extremely large, 1.1 × 10 ^ -3, and is influenced by it. The measurement results when the frequency is changed from FIG. 4 to 39, 57, 69, and 87 Hz are shown in FIGS. 5, 6, 7, and 8. As the frequency rises, the extending direction of the straight line centered on the intersection between the straight lines changes so as to rotate clockwise.
As is clear from FIG. 3, the measured values at the points where the inner can 202 has the same thickness t2 and the interval Gap is different are aligned in a straight line on the amplitude ratio-phase difference plane, and are straight lines when the thickness t2 is different. Crosses at one intersection. The behaviors of the calibration time gradient calculation unit 310, the calibration unit 311 and the measurement unit 312 in this embodiment are based on these experimental facts.

Considering that the distance Gap between the outer can 201 and the inner can 202 cannot be changed or is unknown depending on the subject 2, a simulated body having a variable gap Gap is created, and the measuring device 3 is used. The description will be made on the assumption that the subject 2 is calibrated and the actual subject 2 is measured.
For example, with respect to the simulated body, in a situation where the temperature is 10.4 ° C., the frequency is 33 Hz, and the thickness t1 of the outer can 201 is fixed to 30 mm as shown in FIG. 3, the thickness t2 of the inner can 202 is set to 25 mm. , And the spacing Gap is set to 70 mm. The calibration time gradient calculation unit 310 measures the output voltage of the detection coil 121 in this state, calculates the amplitude ratio and the phase difference, and plots the result as a point PA1 on the amplitude ratio-phase difference plane. Further, the interval Gap of the simulated body is changed to 90 mm, and the calibration gradient calculation unit 310 measures the output voltage of the detection coil 121 in this state, calculates the amplitude ratio and the phase difference, and obtains the result as the amplitude ratio − position. Plot as point PA2 on the phase difference plane. The calibration time gradient calculation unit 310 obtains the first straight line LA1 connecting the two points PA1 and PA2, and calculates the gradient of the first straight line LA1.
Next, the simulated body is in a state in which only the thickness t2 of the inner can 202 is changed to 35 mm from the measurement conditions corresponding to the measurement results shown as the point PA1 as described above. The calibration time gradient calculation unit 310 measures the output voltage of the detection coil 121 in this state, calculates the amplitude ratio and the phase difference, and plots the result as a point PA3 on the amplitude ratio-phase difference plane. Further, the interval Gap of the simulated body is changed to 90 mm, and the calibration gradient calculation unit 310 measures the output voltage of the detection coil 121 in this state, calculates the amplitude ratio and the phase difference, and obtains the result as the amplitude ratio − position. Plot as point PA4 on the phase difference plane. The calibration time gradient calculation unit 310 obtains the second straight line LA2 connecting the two points PA3 and PA4, and calculates the gradient of the second straight line LA2.
The above results are shown in Table 1. In Table 1, as a result corresponding to each of the first and second straight lines LA1 and LA2, the amplitude ratios of the points PA5 and PA6 corresponding to the case where the distance Gap on these straight lines LA1 and LA2 is 80 mm- The coordinate values on the retardation plane, the calculated gradient, etc. are described.

The calibration time gradient calculation unit 310 is the coordinates of the intersection P01 of the two straight lines LA1 and LA2 obtained for each of the cases where the inner can 202 has a plurality of thicknesses t2, that is, when t2 is 25 mm and when t2 is 35 mm. To calculate.

本式、及び以下の説明に使用する各式において、「＊」は、乗算を意味するものとして使用する。
表１において、「勾配」、「ｔ２機械的寸法」の欄の第１行と第２行の各々は、上記の（ｘ１、ｔ２１）、（ｘ２、ｔ２２）のそれぞれの組み合わせの実際の数値を記載したもので、上記の連立方程式を表形式で表したものである。
較正部３１１は、上記数式１を解いて、係数ａと定数ｂの値を導出する。求められた係数ａと定数ｂの値は、表１中のａ、ｂと示されたそれぞれの欄に記載されている。連立方程式の解法としては、逆行列式法、クラメール法等既知の方法を使用すれば良く、本実施形態においては、コンピュータ上の計算において、桁落ちの心配が少ないとされるクラメール法を用いている。後述の各変形例において、連立方程式は、上記の表１と同様の表形式で表示する。
較正部３１１は、この解、すなわち内缶２０２の厚さｔ２と勾配との関係を表す係数を基に、勾配を変数として係数を適用することにより、厚さｔ２の測定時に厚さｔ２を推定する推定式を立式する。より詳細には、導出した係数ａ、定数ｂの値を上記の一次式に代入することで、勾配を変数として、次のような推定式を立式する。

Next, the calibration unit 311 constructs simultaneous equations from the relationship between the thickness t2 and the gradient calculated for the thickness t2 for each of the plurality of thicknesses t2 of the inner can 202.
Assuming that the gradient is x, a is a coefficient applied to the gradient, and b is a constant, the thickness t2 can be expressed by, for example, a linear equation of t2 = ax + b.
Here, as a calibration, the coefficient a and the constant b actually measure the thickness t2 of the inner can at two points (t21, t22) where the thickness t2 of the inner can is known, and the gradient x and the gradient x at each of them. It can be determined by constructing and solving a simultaneous equation shown as the following mathematical formula 1 in which the combination of the measured values of the inner can thickness t2 (x1, t21) and (x2, t22) are input to the above equation. it can.

In this equation and each equation used in the following description, "*" is used to mean multiplication.
In Table 1, each of the first and second rows in the columns of "gradient" and "t2 mechanical dimensions" is the actual numerical value of each combination of (x1, t21) and (x2, t22) above. It is a tabular representation of the above simultaneous equations.
The calibration unit 311 solves the above equation 1 to derive the values of the coefficient a and the constant b. The values of the obtained coefficient a and the constant b are listed in the respective columns shown as a and b in Table 1. As a method for solving simultaneous equations, a known method such as an inverse determinant method or a Kramer method may be used. In this embodiment, the Kramer method, which is said to be less likely to cause a loss of digits in computer calculations, is used. I am using it. In each modification described later, the simultaneous equations are displayed in the same tabular format as in Table 1 above.
Based on this solution, that is, the coefficient representing the relationship between the thickness t2 of the inner can 202 and the gradient, the calibration unit 311 estimates the thickness t2 when measuring the thickness t2 by applying the coefficient with the gradient as a variable. Formulate the estimation formula to be used. More specifically, by substituting the derived values of the coefficient a and the constant b into the above linear equation, the following estimation equation is formulated with the gradient as a variable.

When actually estimating and measuring the thickness t2 of the inner can 202, the measuring unit 312 operates and detects an arbitrary portion on the subject 2 whose thickness t2 is unknown. The output voltage from the coil 121 is measured as the measurement voltage, and the measurement amplitude ratio and the measurement phase difference, which are the amplitude ratio and the phase difference of the measurement voltage with the reference voltage, are calculated.
The measurement unit 312 plots the measurement points corresponding to the measurement amplitude ratio and the measurement phase difference on the amplitude ratio-phase difference plane, and obtains the gradient of the straight line connecting the measurement points and the intersection P01. The measuring unit 312 calculates the value of t2 at the measurement point by substituting this gradient into the above estimation formula.

FIG. 9 shows the measurement results. In FIG. 9, the solid line shows the case where the temperature is 10.4 ° C., and the broken line shows the case where the temperature is 11.4 ° C. It can be seen that when the temperature is 10.4 ° C., the three lines corresponding to the cases where the gap Gap is 70, 80, and 90 mm are substantially overlapped, and the gap Gap is compensated. The 25, 30 and 35 mm flat plates used as the main body of the subject have the same thickness as the standard products from the blast furnace, but the 28 mm and 32 mm flat plates are created by cutting from the 30 mm and 35 mm flat plates, respectively. It is presumed that the electromagnetic induction physical property value changed due to processing. However, it is clear that the variation in the interval Gap is compensated for as it changes.
In this embodiment, the subject body 202 has been described as a flat plate, but the effect of the present invention does not change even if the plate is a curved plate.

Next, the non-destructive inspection measurement method using the above non-destructive inspection measurement system 10 will be described with reference to FIGS. 1 to 9 and 10. FIG. 10 is a flowchart of the non-destructive inspection measurement method.
This non-destructive inspection measurement method outputs an exciting coil provided in the subject to excite the subject body and a voltage corresponding to a change in the magnetic field generated in the subject body when the subject body is excited by the exciting coil. A sine wave signal or a composite signal consisting of a plurality of sine waves having different frequencies is applied to the detection coil and the excitation coil to excite the subject body, and the voltage output from the detection coil is detected to detect the subject. This is a non-destructive inspection measurement method that measures the dimensions of the main body, and outputs from the detection coil for multiple parts where the dimensions of the main body of the subject are known and different, for each of the multiple dimensions and under different measurement conditions. The voltage to be measured is measured, the amplitude ratio and phase difference between this and the reference voltage are calculated, and the points corresponding to at least two measurement results on the amplitude ratio-phase difference plane with the amplitude ratio and phase difference as the two axes. The straight line connecting the intervals is obtained, the slope of the straight line is calculated, and a simultaneous equation is constructed from the relationship between the dimension and the value calculated for the dimension for each of a plurality of dimensions. Based on the solution, an estimation formula is formulated with the value based on the gradient as a variable to estimate the dimensions when measuring the dimensions, and based on the estimation formula, the dimensions of the part to be measured of the subject body are determined. Estimate and measure.

The calibration time gradient calculation unit 310 measures using the sensor 1 at a specific frequency, at a known first thickness t21 of the inner can 202, and at a known first distance Gap1 between the outer can 201 and the inner can 202. The amplitude ratio and the phase difference are calculated by the above method, and the amplitude ratio is plotted on the amplitude ratio-phase difference plane with the amplitude ratio on the horizontal axis and the phase difference on the vertical axis. Further, the calibration time gradient calculation unit 310 changed the gap Gap between the outer can 201 and the inner can 202 to a second gap Gap2 different from the first gap Gap1, and used the sensor 1 under the same conditions for the others. The amplitude ratio and phase difference are calculated by measurement and plotted on the amplitude ratio-phase difference plane. The calibration gradient calculation unit 310 calculates a first straight line connecting these two points plotted on the amplitude ratio-phase difference plane.
The calibration time gradient calculation unit 310 also has a known second thickness t22 different from the first thickness t21, and is measured by the sensor 1 at the third distance Gap3 between the outer can 201 and the inner can 202. Calculate the amplitude ratio and phase difference, and plot them on the amplitude ratio-phase difference plane. Further, the calibration time gradient calculation unit 310 changed the gap Gap between the outer can 201 and the inner can 202 to a fourth gap Gap4 different from the third gap Gap3, and used the sensor 1 under the same conditions for the others. The amplitude ratio and phase difference are calculated by measurement and plotted on the amplitude ratio-phase difference plane. The calibration gradient calculation unit 310 calculates a second straight line connecting these two points plotted on the amplitude ratio-phase difference plane.
The calibration gradient calculation unit 310 calculates the gradient of the first straight line and the gradient of the second straight line on the amplitude ratio-phase difference plane (step S1).

The calibration time gradient calculation unit 310 obtains the intersection P0 on the extension line of the first straight line and the second straight line (step S3).

The calibration unit 311 constructs a binary simultaneous equation based on the thicknesses t21 and t22 of the inner can 202 and the corresponding gradient values (step S5).
The calibration unit 311 solves this and formulates an estimation formula (step S7).

When actually estimating and measuring the thickness t2 of the inner can 202, the measuring unit 312 operates and detects an arbitrary portion on the subject 2 whose thickness t2 is unknown. The output voltage from the coil 121 is measured as the measurement voltage, and the measurement amplitude ratio and the measurement phase difference, which are the amplitude ratio and the phase difference of the measurement voltage with the reference voltage, are calculated. The measurement unit 312 plots the measurement amplitude ratio and the measurement phase difference as measurement points on the amplitude ratio-phase difference plane, and the intersection P0 of this measurement point and the extension line of the first straight line and the second straight line. The measurement gradient, which is the gradient of the measurement straight line connecting the two, is calculated (step S9).
The measuring unit 312 calculates and measures the thickness t2 of the inner can 202 in the measured portion on the subject 2 by substituting the measurement gradient into the estimation formula established by the calibration unit 311 (step S11). ).

Next, the effects of the non-destructive inspection measurement system 10 and the non-destructive inspection measurement method will be described.

The non-destructive test measurement system 10 of the present embodiment has an exciting coil 113 for exciting the subject body 202 provided in the subject 2 and a subject body 202 when the subject body 202 is excited by the exciting coil 113. A sine wave signal or a composite signal composed of a plurality of sine waves having different frequencies is applied to the detection coil 121 that outputs a voltage corresponding to the generated magnetic field change and the excitation coil 113 to excite the subject body 202. A non-destructive inspection measurement system 10 including a measuring device 3 that detects a voltage output from the detection coil 121 and measures the dimension t2 of the subject body 202. The measuring device 3 is the dimension of the subject body 202. For a plurality of parts where t2 is known and different, the voltage output from the detection coil 121 is measured for each of the plurality of dimensions t2 under different measurement conditions, and the amplitude ratio and phase difference between this and the reference voltage. Is calculated, a straight line connecting points corresponding to at least two measurement results on the amplitude ratio-phase difference plane with the amplitude ratio and the phase difference as two axes is obtained, and the gradient of the straight line is calculated. A simultaneous equation is constructed from the relationship between the part 310, the dimension t2 for each of the plurality of dimensions t2, and the value based on the gradient calculated for the dimension t2, and the dimension t2 is based on the solution. The calibration unit 311 that estimates the dimension t2 at the time of measurement and formulates an estimation formula with a value based on the gradient as a variable, and the dimension t2 of the part to be measured of the subject body 202 based on the estimation formula. It includes a measuring unit 312 for estimating and measuring.
Further, the non-destructive inspection measurement method of the present embodiment includes an exciting coil 113 for exciting the subject main body 202 provided in the subject 2, and a subject main body 202 when the subject main body 202 is excited by the exciting coil 113. A sine wave signal or a composite signal composed of a plurality of sine waves having different frequencies is applied to the detection coil 121 that outputs a voltage corresponding to the change in the magnetic field generated in the above and the excitation coil 113 to excite the subject body 202. , A non-destructive inspection measurement method in which the voltage output from the detection coil 121 is detected and the dimension t2 of the subject body 202 is measured, and the dimension t2 of the subject body 202 is known and different for a plurality of parts. The voltage output from the detection coil 121 is measured for each of the plurality of different measurement conditions for each of the plurality of dimensions t2, the amplitude ratio and phase difference between this and the reference voltage are calculated, and the amplitude ratio and phase difference are set to 2. Amplitude ratio as an axis-A straight line connecting points corresponding to at least two measurement results on the phase difference plane is obtained, the gradient of the straight line is calculated, and the dimension t2 and the dimension t2 for each of the plurality of dimensions t2. A simultaneous equation is constructed from the relationship with the value based on the gradient calculated for t2, and based on the solution, the dimension t2 is estimated when the dimension t2 is measured. The value based on the gradient is used as a variable. Based on the estimation formula, the dimension t2 of the portion of the subject body 202 to be measured is estimated and measured.
According to the above configuration, before measuring the dimension t2 of the portion of the subject body 202 to be measured, a plurality of different measurement conditions for each dimension t2 are obtained for a plurality of portions whose dimensions t2 are known and different. The voltage output from the detection coil 121 is measured in each of the above, and the amplitude ratio and phase difference between this and the reference voltage are calculated, and the amplitude ratio and the phase difference are taken as two axes on the amplitude ratio-phase difference plane. A straight line connecting points corresponding to at least two measurement results is obtained, and the gradient of the straight line is calculated. If the measurement conditions are different when the dimensions t2 are the same, the amplitude ratio and the phase difference are generally in a proportional relationship. Therefore, the gradient obtained in this way for each dimension t2, that is, the proportional relationship is shown as a straight line. The slope of the case is a value in which the influence of the measurement conditions is suppressed.
When actually estimating and measuring the dimension t2 of the part to be measured of the subject body 202, it was constructed from the relationship between the dimension t2 and the value based on the gradient calculated for the dimension t2. By solving the simultaneous equations, an estimation formula is formulated, and the dimension t2 is obtained based on this.
Therefore, the influence of the measurement conditions can be reduced, and the dimension t2 of the subject body 202 provided in the subject 2 can be measured with high accuracy.

Further, the calibration unit 311 formulates a plurality of linear equations representing the relationship between the dimension t2 and the value based on the gradient calculated for the dimension t2 for each of the plurality of dimensions t2. By solving these as simultaneous equations, a coefficient representing the relationship between the dimension t2 and the value based on the gradient is calculated, and the estimation formula is formulated by applying the coefficient using the value based on the gradient as a variable.
Further, the measuring unit 312 measures the voltage output from the detection coil 121 as the measurement voltage with respect to the measurement target portion of the subject body 202, and measures the amplitude ratio and phase difference between this and the reference voltage. Calculate the time amplitude ratio and the measurement time phase difference, calculate the measurement time gradient which is the gradient on the amplitude ratio-phase difference plane corresponding to these, and use the value based on the measurement time gradient as the variable of the estimation formula. Substitute to calculate and measure dimension t2.
Further, the calibration gradient calculation unit 310 further calculates the intersection points between the straight lines obtained for each of the plurality of dimensions t2, and the measurement unit 312 calculates the measurement amplitude ratio and the measurement time on the amplitude ratio-phase difference plane. The slope of the straight line connecting the measurement points and the intersections corresponding to the phase difference is calculated as the measurement time slope.
According to the above configuration, the above nondestructive inspection and measurement system 10 can be appropriately realized.

Further, the measurement condition includes the distance from the outer surface 201a of the subject 2 or the member 201 constituting the outer surface 201a to the subject main body 202.
According to the above configuration, the influence of the distance Gap from the outer surface 201a of the subject 2 or the member 201 constituting the outer surface 201a to the subject body 202 is reduced, and the inside of the subject 2 is highly accurate. The dimension t2 of the subject body 202 provided in the above can be measured.

Further, the subject body 202 is a plate body, the dimension t2 is the thickness t2 of the plate body, the value based on the gradient is the gradient, and in the simultaneous equations, the dimension t2 and the gradient are in a proportional relationship. ..
According to the above configuration, when the subject body 202 is a plate formed in a flat plate shape or a kiln shape, its thickness t2 can be measured with high accuracy.

[First Modified Example of Embodiment]
Next, with reference to FIG. 11, a first modification of the non-destructive inspection measurement system 10 and the non-destructive inspection measurement method shown as the above embodiment will be described. FIG. 11 is a diagram showing the configuration of the non-destructive inspection measurement system 40 in the first modification. The non-destructive inspection measurement system 40 in the first modification is the non-destructive inspection measurement system 10 of the above-described embodiment, in which the computer 405 of the measurement device 403 compensates for fluctuations in the measurement result due to the ambient temperature of the subject 2. The point is different.

The subject 2 to be electromagnetically induced is generally a metal, and the eddy current is affected by the electrical resistance of the metal. On the other hand, the temperature coefficient of electrical resistance of metal is very large, for example, the temperature coefficient of electrical resistance of stainless steel SUS304 is 1.1x10 ^ -3. Therefore, since the measured value is strongly influenced by the temperature, the measurement accuracy can be improved by considering the temperature. However, since the subject body 202 is provided in the subject 2, the temperature cannot be directly detected.
In this modification, we focused on the fact that in general metals, the amplitude of high frequencies is often strongly affected by eddy currents, and the amplitude ratio of high frequencies is incorporated into calibration as an index of temperature for calibration and measurement. By doing so, temperature compensation is performed.
Conceptually, in addition to the configuration of the above embodiment, a higher frequency is used in this modification, which is different from the frequency used by the calibration time gradient calculation unit 310 in the above embodiment, and the measurement is performed at different temperatures. Then, the gradient and the amplitude ratio or the phase difference on the amplitude ratio-phase difference plane due to the fluctuation of the interval Gap are incorporated into the simultaneous equations to calibrate and perform temperature compensation.

More specifically, the calibration time gradient calculation unit 410 in this modification executes the following processing. Here, in the above embodiment, for example, as shown in Table 1, each measurement is performed under the same temperature conditions and by applying the same frequency to the detection coil 121. Let this temperature and frequency be the first temperature and the first frequency.
The calibration time gradient calculation unit 410 first performs the measurement corresponding to the above Table 1 in the same manner as in the above embodiment. That is, the calibration time gradient calculation unit 410 is known for each of the plurality of thicknesses t2 for a plurality of portions where the thickness t2 of the inner can 202 is known and different under the conditions of the first temperature and the first frequency. The voltage output from the detection coil 121 is measured at each of the plurality of intervals Gap, and the amplitude ratio and phase difference between this and the reference voltage are calculated. The amplitude ratio and the phase difference are the two axes. The first and second straight lines connecting the points corresponding to at least two measurement results on the retardation plane are obtained, and the gradients of the first and second straight lines are calculated as the two first temperature time gradients. ..
Next, the calibration time gradient calculation unit 410 applies a signal of the first frequency to the detection coil 121 under a second temperature different from the first temperature, and for at least one kind of thickness t2. , Each of the known and different intervals Gap, measures the voltage output from the detection coil 121 and calculates the amplitude ratio and phase difference between this and the reference voltage, and at least 2 on the amplitude ratio-phase difference plane. A straight line connecting the points corresponding to the two measurement results is obtained, and the gradient of the straight line is calculated as the second temperature gradient.
Further, the calibrated gradient calculation unit 410 detects a signal of a second frequency, which is different from the first frequency and is higher in this modification, under each of the first temperature and the second temperature. The voltage output from the detection coil 121 is measured, and the different frequency amplitude ratio, which is the amplitude ratio between this and the reference voltage, is calculated.
The calibration unit 411 constructs simultaneous equations from the relationship between the thickness t2 and the first temperature gradient, the second temperature gradient, and the different frequency amplitude ratio for each of the plurality of thicknesses t2 and temperature, and based on the solution. Formulate the estimation formula in.
The measuring unit 412 estimates and measures the thickness t2 of the portion of the inner can 202 to be measured based on the estimation formula.

Hereinafter, more detailed behaviors of the calibration time gradient calculation unit 410, the calibration unit 411, and the measurement unit 412 as described above will be described together with an embodiment of the non-destructive inspection measurement system 40.

[Example 2]
As shown in FIG. 9 shown in the above embodiment, when the temperature is 11.4 ° C, it changes and shows a different value from the case where the temperature is 10.4 ° C, and the changes are parallel. It is mobile. Therefore, it is necessary to provide some temperature compensation to reflect this translation. As temperature compensation, there is a method of providing a temperature detection element such as a thermoelectric pair and performing the measurement based on the measurement result. However, even if the temperature detection element can be installed in the outer can 201, it cannot be installed in the inner can 202. In many cases, it is generally difficult. Therefore, if possible, it is desirable to compensate based on the data acquired by the sensor 1. Therefore, we focused on the data in the high frequency domain.
As shown in FIG. 8, when the frequency is 87 Hz, the change in the amplitude ratio is large as compared with the fact that the phase does not change much depending on the temperature. This is because the eddy current increases as the frequency increases, and the eddy current is affected by the electrical resistance of the subject, so that the temperature change of the electrical resistance is greatly affected. Therefore, the measurement result when the frequency is 87 Hz is incorporated into the simultaneous equations as a kind of thermometer.

Specifically, the calibration time gradient calculation unit 410 first sets the temperature to the first temperature, for example 10.4 ° C., and the frequency to the first frequency, for example 33 Hz, and the thickness t2 of the inner can 202. The measurement as shown in Table 1 is performed in the above embodiment, and the gradient corresponding to each of the plurality of straight lines LA1 and LA2 described in the gradient column of Table 1 is defined as the first temperature gradient. calculate.

Next, the calibration time gradient calculation unit 410 changes the temperature to 11.4 ° C., which is the second temperature, and performs the measurement without changing the frequency from the first frequency. Here, the thickness t1 of the outer can 201 was fixed to 30 mm, the thickness t2 of the inner can 202 was fixed to 35 mm, and the interval Gap was changed to 70, 80, 90 mm. As a result, the measurement results shown as points PB1, PB2, and PB3 in FIG. 4 can be obtained. Among them, for example, the third straight line LB3 connecting the points PB1 and the point PB3 is obtained, and the gradient of the third straight line LB3 is calculated as the second temperature gradient.
The above results are shown in Table 2. In Table 2, as a result corresponding to each of the first and second straight lines LA1 and LA2 in the above embodiment and the third straight line LB3 in the present modification, the intervals at LA1, LA2 and LB3 on these straight lines The coordinate values on the amplitude ratio-phase difference plane of each of the points PA5, PA6, and PB2 corresponding to the case where the Gap is 80 mm, the calculated gradient, and the like are described.

Further, the calibration time gradient calculation unit 410 fixes the thickness t2 of the inner can 202 to 35 mm under each measurement condition of each point PA5, PA6, and PB2 as shown as “A87Hz_35_80” in Table 2, and maintains the interval. The measurement is performed when the Gap is 80 mm and the frequency is changed to 87 Hz, which is the second frequency, which is higher than the 33 Hz of the first frequency, and the different frequency amplitude ratio, which is the amplitude ratio in each case, is calculated. The measurement result under this measurement condition corresponds to the case where the frequency is 87 Hz in FIG. 8 shown in the above embodiment. At point PA5 and point PA6, the only difference in measurement conditions is the thickness t2 of the inner can 202, and in the measurement using the second frequency, this thickness t2 was fixed at 35 mm. Therefore, in FIG. 8, FIG. These correspond to the same point PB4, and as a result, the same values are stored in Table 2. Point PB2 corresponds to point PB5 in FIG.

Next, the calibration unit 411 is based on the relationship between the thickness t2 of the inner can 202 and the gradient calculated with respect to the thickness t2 for each temperature, and the different frequency amplitude ratio. Build simultaneous equations.
Assuming that the gradient is x, the different frequency amplitude ratio is y, a is a coefficient related to the gradient, b is a coefficient related to the different frequency amplitude ratio, and c is a constant, the thickness t2 is expressed by, for example, a linear equation of t2 = ax + by + c. be able to. For this equation, the calibration unit 411 constructs and solves a ternary simultaneous equation for the coefficients a, b, and the constant c by substituting each value in Table 2 in the same manner as in the above embodiment. The values described in the respective columns indicated as a, b, and c in 2 are derived.
Based on this solution, that is, the coefficient representing the relationship between the thickness t2 of the inner can 202, the gradient, and the different frequency amplitude ratio, the calibration unit 411 applies the coefficient with the gradient and the different frequency amplitude ratio as variables. An estimation formula for estimating the thickness t2 is established when the thickness t2 is measured. More specifically, by substituting the derived values of the coefficients a, b, and constant c into the above linear equation, the following estimation equation is formulated with the gradient and the different frequency amplitude ratio as variables.

When actually estimating and measuring the thickness t2 of the inner can 202, the measuring unit 412 operates the sensor 1 at an arbitrary portion on the subject 2 to be measured to obtain the output voltage from the detection coil 121. It is measured as the measurement voltage, and the measurement amplitude ratio and the measurement phase difference, which are the amplitude ratio and the phase difference of the measurement voltage with the reference voltage, are calculated.
The measuring unit 412 plots the points corresponding to the amplitude ratio at the time of measurement and the phase difference at the time of measurement on the amplitude ratio-phase difference plane corresponding to the temperature at the time of measurement, and obtains the gradient of the straight line connecting these points and the intersection. .. Further, the measuring unit 412 acquires the value of the different frequency amplitude ratio corresponding to the temperature at the time of measurement from a table or the like stored in the computer 405. The measuring unit 412 calculates the t2 value at the measurement point by substituting the gradient and the different frequency amplitude ratio into the above estimation formula.

FIG. 12 shows the measurement results. When the temperature is 11.4 ° C. and the interval Gap is 90 mm, there is a slight error in the measurement of the thickness t2 of the inner can 202, but under other conditions, a sufficiently accurate result is derived.
Table 3 shows the results of calculating the measured values using the derived coefficients and constants a, b, and c. Table 4 shows two straight lines connecting two points and simultaneous equations for finding the intersection P01 (x0, y0) of the two straight lines. Calculated by the Kramer method using the function for finding the determinant of spreadsheet software. There is. It is configured so that the values of x0 and y0 are automatically calculated when the measured value is input to this macro.

Needless to say, the first modification has the same effect as that of the embodiment described above.
In particular, in this modification, the calibrating gradient calculation unit 410 applies a frequency higher than the frequency of the sinusoidal signal or the combined signal applied to the exciting coil 113 when calculating the gradient to the exciting coil, and from the detection coil 121. The output voltage is measured, and the different frequency amplitude ratio, which is the amplitude ratio between this and the reference voltage, is calculated, and the calibration unit 411 has a plurality of dimensions t2 and the dimension t2 and the dimension t2 for each temperature. A simultaneous equation is constructed from the relationship between the value based on the gradient calculated for the above and the different frequency amplitude ratio, and the estimation formula is formulated based on the solution.
According to the above configuration, a frequency higher than the frequency of the signal applied to the exciting coil 113 when the gradient calculation unit 410 calculates the gradient is applied to the exciting coil 113, and the frequency is output from the detection coil 121. The voltage is measured, the different frequency amplitude ratio, which is the amplitude ratio between this and the reference voltage, is calculated, and this is reflected in the simultaneous equations. Since the amplitude of high frequencies is strongly influenced by eddy currents, it is possible to formulate an estimation formula that appropriately considers the influence of temperature by constructing and solving simultaneous equations that reflect the amplitude ratio of high frequencies.
Therefore, the influence of temperature can be reduced, and the dimensions of the subject body 202 provided in the subject 2 can be measured with high accuracy.

[Second variant of the embodiment]
Next, a second modification of the non-destructive inspection measurement system 10 and the non-destructive inspection measurement method shown as the above-described embodiment will be described with reference to FIGS. 13 and 14. FIG. 13 is a diagram showing the configuration of the non-destructive inspection measurement system 50 in the second modification. FIG. 14 is a schematic plan view of the sensor 1C of the non-destructive inspection measurement system 50 in the second modification. The non-destructive inspection measurement system 50 in the second modification has a different subject from the non-destructive inspection measurement system 10 of the above embodiment, and accordingly, the processing content in the computer 505 is also different.
The diameter of the rod-shaped object, especially the round bar-shaped subject body 202C, embedded in the subject 2C is affected by the distance between the sensor 1C and the subject body 2C, that is, lift-off (abbreviated as LO). There is a great demand for accurate measurement. As an example, there is a demand to accurately measure the diameter of reinforcing bars in reinforced concrete regardless of the depth embedded in the concrete, that is, the amount of "fog" in the industry terminology.
In this modification, the subject body 202C is a rod having a circular cross section in response to such a requirement. The subject 2C to be inspected is, for example, a column or a beam formed of reinforced concrete, especially in this modified example. In the subject 2C, the reinforcing bar 202C is embedded in the concrete 201C at a position separated from the outer surface 201a by LO. In FIG. 13, the reinforcing bar 202C extends in the direction orthogonal to the paper surface. In addition, the LO standard is measured below as the center of the circular cross section. The diameter D of the reinforcing bar 202C is the diameter of this cross section.

The configuration of the sensor 1C is different from the above embodiment only in that it is composed of four exciters 11 as shown in FIG. Therefore, detailed description of the sensor 1C will be omitted.

In this modification, since the subject body is different from the above embodiment as described above, the calibration time gradient calculation unit 510, the calibration unit 511, and the measurement unit 512 provided in the measuring device 503, particularly the computer 505, The behavior is different from the above embodiment.
In this modification, the non-destructive inspection measurement system 50 finally measures the diameter D of the reinforcing bar 202C. When measuring the diameter of the reinforcing bar 202C, the measuring device 503 measures the square of the difference between the diameter of the reference circle of a predetermined size stored in the computer 505 and the diameter of the reinforcing bar 202C as dimensions. calculate. Based on the value of this dimension, the computer 505 calculates the diameter D of the reinforcing bar 202C.
Conceptually, in this modification, the amplitude ratio and phase difference of the reinforcing bars 202C having different thicknesses are measured by changing the distance between the sensor 1C and the reinforcing bars 202C, and measured on the amplitude ratio-phase difference plane. Calibration and measurement are performed assuming that the slope of the straight line connecting the points is proportional to the square of the difference in thickness.

Hereinafter, more detailed behaviors of the calibration time gradient calculation unit 510, the calibration unit 511, and the measurement unit 512 as described above will be described together with an example of the non-destructive inspection measurement system 50.

[Example 3]
The sensor 1C is formed so that the housing has a width of 120 mm, a length of 440 mm, and a height of 130 mm.
Reinforcing bars used for general reinforced concrete are deformed reinforcing bars such as D9 and D13, and have knot-like irregularities on the surface to improve adhesion to concrete, which is not suitable for precise comparative measurement. Therefore, in this example, a round steel bar for reinforced concrete was used. However, even with round steel bars of the same standard, there are individual differences in electromagnetic induction physical property values such as electrical resistance and relative permeability, so preliminary measurements were carried out and standard ones were selected. In addition, standard products were used for reinforcing bars with diameters of 9 mmΦ and 13 mmΦ, but since there is no standard product for 11 mmΦ, long reinforcing bars of the same individual with diameters of 13 mmΦ were lathed with 13 mmΦ and 48.3 cm. We made 11mmΦ and 48.3cm ones, and took care to eliminate individual differences.

FIG. 15 is an example of the measurement result. Three types of reinforcing bars 202C having the same length L as 48.3 cm and diameters D of 9, 11, and 13 mm are converted into two types of LO of 36.5 mm and 56.5 mm. In the case of a total of 6 types provided, the output voltage of the detection coil 121 is measured with a frequency of 6 Hz, and the result of calculating the amplitude ratio and the phase difference is plotted on the amplitude ratio-phase difference plane.
The reason why the frequency is set as low as 6 Hz is that the steel material has magnetism, and when there is magnetism, a large eddy current is generated when the frequency is high, and the demagnetizing field caused by this causes magnetic field lines to penetrate into the subject. This is because it becomes difficult to do.

In each case where the diameter D is 9 mmΦ, 11 mmΦ, and 13 mmΦ, the straight lines connecting the points with LO of 36.5 mm and the points with LO of 56.5 mm are defined as straight lines LC1, LC2, and LC3, respectively. Focusing on the gradients of the straight lines LC1, LC2, and LC3, the reinforcing bar 202C having a diameter D of 11 mmΦ has a diameter value of 11 mmΦ at the center of 9 mmΦ and 13 mmΦ, but these gradients. It does not become the center of the above, and shows a tendency close to the gradient when the diameter D is 13 mmΦ.
FIG. 16 is an enlarged view of the lower right portion of FIG. In the above embodiment, for example, as shown with reference to FIG. 3, each straight line intersects at one intersection, but in this modification, the above three straight lines LC1, LC2, and LC3 intersect at one point. do not do. The intersection of each extrapolation line of the straight line LC2 and the straight line LC3 is on the extrapolation line of the straight line LC3, and when the diameter D is smaller, the intersection point of the extrapolation line of the straight line LC3 with the extrapolation line of the straight line LC1. It is presumed that it will move towards. From these experimental facts, when the subject body 202C is a rod with a circular cross section, the change in diameter D is not only the change in the LO direction from the subject body 202C toward the outer surface 201a of the subject 2C, but also the change in the LO direction. It can be seen that the change in the left-right direction in FIG. 13, which is orthogonal to the LO direction and the stretching direction of the subject body 202C, also affects the gradient. That is, it has been found that the gradient changes in proportion to the square of the difference in diameter, not the squared difference in diameter, that is, the difference in cross section, which is usually easily considered.
This is considered to be based on the following events. That is, when the subject body 202C is excited by the exciting coil 113, an eddy current is generated. As shown in FIG. 17, the demagnetic field 202b due to this eddy current makes it difficult for the magnetic flux to enter the inside of the subject body 202C. Therefore, the magnetic flux 202c passes by bypassing the surface layer portion of the subject body 202C. Therefore, the entire cross-sectional area of the cross section of the reinforcing bar 202C, that is, the square of the diameter is not related, but the difference in the surface layer portion, that is, the difference in the surface layer portion = (thickness difference in the surface layer portion × length difference in the surface layer portion). Is also related to the difference in diameter, and can be interpreted as an experimental fact related to the square of the difference in diameter.

In this modification, the definition of the dimensions is different from that of the above embodiment, and the actual processing contents of the calibration time gradient calculation unit 510, the calibration unit 511, and the measurement unit 512 are the same as those of the above embodiment.
Here, the size of the reference predetermined diameter D is 13 mmΦ. Further, the difference between the diameter D of the reinforcing bar 202C to be measured and the reference diameter is represented by δD. For example, when the diameter D of the reinforcing bar 202C to be measured is 13 mmΦ, δD = 0, and when the diameter D is 9 mmΦ, δD = 4. Further, the square of δD is expressed as (δD) ^ 2 due to the font relationship.
The calibration gradient calculation unit 510 calculates the gradient for each of the straight line LC3 and the straight line LC1 as described above, for example. The diameter D of each of the points PC2 and PC1 corresponding to the case where the LO on the straight line LC3 and the straight line LC1 is 36.5 mm, and the amplitude ratio, phase difference, gradient, and reference calculated by the calibration gradient calculation unit 510. The square of the difference from the diameter (δD) ^ 2 is as shown in Table 5 below. The fact that the square (δD) ^ 2 of the difference from the reference diameter is a negative number indicates that the diameter of the reinforcing bar 202C is smaller than the reference diameter.

The calibration unit 511 constructs simultaneous equations based on Table 5 above.
Assuming that the gradient is x, a is the coefficient applied to the gradient, and b is a constant, the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter is, for example, a linear expression of (δD) ^ 2 = ax + b. Can be represented by. For this equation, the calibration unit 511 constructs and solves a binary simultaneous equation for the coefficient a and the constant b by substituting each value in Table 5 in the same manner as in the above embodiment, in Table 5. The values described in the respective columns indicated by a and b in the above are derived.
The calibration unit 511 applies a coefficient with the gradient as a variable based on this solution, that is, a coefficient representing the relationship between the square of the difference between the diameter of the reinforcing bar 202C and the reference diameter (δD) ^ 2 and the gradient. , An estimation formula for estimating this when measuring the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter is established. More specifically, by substituting the derived values of the coefficient a and the constant b into the above linear equation, the following estimation equation is formulated with the gradient as a variable.

When actually estimating and measuring the diameter D of the reinforcing bar 202C, the measuring unit 512 operates the sensor 1C at an arbitrary part on the subject 2C to be measured to measure the output voltage from the detection coil 121. It is measured as a voltage, and the measurement amplitude ratio and the measurement phase difference, which are the amplitude ratio and the phase difference of the measurement voltage with the reference voltage, are calculated.
The measuring unit 512 plots the points corresponding to the amplitude ratio at the time of measurement and the phase difference at the time of measurement on the amplitude ratio-phase difference plane, and obtains the gradient of the straight line connecting the points and the intersections. By substituting this gradient into the above estimation formula, the measuring unit 512 calculates the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter at the measurement point. The measuring unit 512 calculates the square root of this value based on the value of the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter, and adds or subtracts it to the reference diameter value. By doing so, the diameter D is calculated.

18 and 19 show the measurement results. In this case, as shown in FIG. 13, the sensor 1C scans and measures in the left-right direction of the paper surface, and in FIGS. 18 and 19, the position corresponding to the center of the reinforcing bar 202C is displayed as X = 0. There is. FIG. 18 shows a case where LO is 36.5 mm, and (δD) ^ 2 is measured to be approximately -4 for a reinforcing bar having a diameter D of 11 mmΦ. Therefore, δD is -2, the diameter D is 13-2 = 11 (mm), and the diameter D of the 11 mmΦ reinforcing bar 202C is accurately measured. FIG. 19 shows a case where the LO is 56.5 mm. Even if the LO changes, the diameter D is accurately measured in the case of the 11 mmΦ reinforcing bar 202C.

Needless to say, this second modification has the same effect as that of the embodiment described above.
In particular, in this modification, the subject body 202C is a rod body having a circular cross section, and the dimensions are the square of the difference between the diameter of a circle having a reference size and the diameter of the cross section of the rod body, and are simultaneous. In the equation, the values based on dimensions and slopes are proportional.
When the subject body 202C is a rod body having a circular cross section, when the magnetic field lines generated by the exciting coil 113 enter the rod body, a magnetic field is formed in the direction opposite to the direction of the magnetic field formed by the penetrating magnetic flux. Since the eddy current flows in this way, the magnetic field lines are canceled by the eddy current and do not enter the inside of the rod body, but flow near the surface of the rod body and exit to the side opposite to the intrusion point. Therefore, in the case of a rod with a circular cross section, the slope, that is, the slope when the proportional relationship between the amplitude ratio and the phase difference is shown as a straight line, is not the diameter of the rod, but a circle of some reference size. When specified, the relationship is proportional to the square of the difference between the diameter of this circle and the diameter of the cross section of the rod to be measured.
Therefore, according to the above configuration, when the subject body 202C is a rod body having a circular cross section, its diameter can be measured with high accuracy.

[Third variant of the embodiment]
Next, a third modification of the non-destructive inspection measurement system 10 and the non-destructive inspection measurement method shown as the above embodiment will be described with reference to FIG. This modified example is a further modified example of the second modified example. FIG. 20 is a diagram showing the configuration of the non-destructive inspection measurement system 60 in the third modification. The non-destructive inspection measurement system 60 in the third modification is shown in Table 5 with the length of the subject body 202C and the calculation in the second modification with the non-destructive inspection measurement system 50 in the second modification. The difference is that the quadratic gradient is calculated based on the calculated gradient, and the simultaneous equations and estimation equations are formulated based on this.
When actually measuring the diameter of the rod-shaped subject body 202C as shown in the second modification, the length of the subject body 202C affects the measurement accuracy. More specifically, when the subject body 202C has a length of a certain length or more, the influence in the length direction is saturated and becomes constant, but when the length is shortened, the influence appears. In the non-destructive inspection measurement system 60 of this modification, the influence of this length is reduced.

FIG. 21 is a graph showing the relationship between the gradient calculated for each of the straight lines LC1, LC2, and LC3 in the second modification and the length of the reinforcing bar 202C. In FIGS. 15 and 16, since the length of the reinforcing bar 202C is 48.3 cm, the straight line LC1 in FIGS. 15 and 16 corresponds to the point PD1, the straight line LC2 corresponds to the point PD2, and the straight line LC3 corresponds to the point PD3. To do. The straight lines LD1, LD2, and LD3 show changes in the gradient when the lengths of the reinforcing bars 202C having diameters D of 9 mmΦ, 11 mmΦ, and 13 mmΦ are changed, respectively.
When the length of the reinforcing bar 202C is 70 cm or more, the gradient is saturated and becomes almost constant, but when the length is smaller than 70 cm, the gradient decreases, and the extrapolation lines of the straight lines LD1, LD2, and LD3 in FIG. 21 Concentrates on one point P0.
The horizontal axis coordinate L of P0 is about −9.2. Since the horizontal axis is the length of the reinforcing bar 202C, it cannot be a negative value. Therefore, this is an approximate value at a length near this, and if the length is smaller than this, this P0 is L = It is estimated to be near 0. Therefore, based on the gradient value calculated by the gradient calculation unit 510 at the time of calibration, the gradient of the gradient with respect to the length L, that is, δ gradient / δ L is quadratic on the length-gradient plane as shown in FIG. Calculated as a gradient (value based on the gradient).
The computer 605 of the measuring device 603 in this modification includes a calibrated secondary gradient calculation unit 613, and the calibrated secondary gradient calculation unit 613 calculates the secondary gradient as described above. The calibration unit 611 in this modified example constructs simultaneous equations based on this.
Table 6 shows the quadratic gradients with respect to the straight line LC3 and the straight line LC1 of the third modification added to Table 5.

The calibration unit 611 constructs simultaneous equations based on Table 6 above.
Assuming that the quadratic gradient is x, a is the coefficient applied to the quadratic gradient, and b is a constant, the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter is, for example, (δD) ^ 2 = It can be expressed by a linear expression of ax + b. With respect to this equation, the calibration unit 611 constructs and solves a binary simultaneous equation for the coefficient a and the constant b by substituting each value in Table 6 in the same manner as in the above embodiment, in Table 6. The values described in the respective columns indicated by a and b in the above are derived.
Based on this solution, that is, the coefficient representing the relationship between the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter and the quadratic gradient, the calibration unit 611 sets the coefficient with the quadratic gradient as a variable. By applying it, an estimation formula for estimating the difference squared (δD) ^ 2 between the diameter of the reinforcing bar 202C and the reference diameter is formulated. More specifically, by substituting the derived values of the coefficient a and the constant b into the above linear equation, the following estimation equation is formulated with the quadratic gradient as a variable.

When actually estimating and measuring the diameter D of the reinforcing bar 202C, the measuring unit 612 operates the sensor 1C at an arbitrary part on the subject 2C to be measured to measure the output voltage from the detection coil 121. It is measured as a voltage, and the measurement amplitude ratio and the measurement phase difference, which are the amplitude ratio and the phase difference of the measurement voltage with the reference voltage, are calculated.
The measuring unit 612 plots the points corresponding to the amplitude ratio at the time of measurement and the phase difference at the time of measurement on the amplitude ratio-phase difference plane, obtains the gradient of the straight line connecting these points and the intersection, and further 2 based on this. Calculate the next gradient. By substituting this quadratic gradient into the above estimation formula, the measuring unit 612 calculates the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter at the measurement point. The measuring unit 612 calculates the square root of this value based on the value of the square (δD) ^ 2 of the difference between the diameter of the reinforcing bar 202C and the reference diameter, and adds or subtracts it to the reference diameter value. By doing so, the diameter D is calculated.

Table 7 is a table showing the results in more detail, and FIG. 22 is a graph of this.
As shown in Table 7 and FIG. 22, even if the LO changes from 36.5 mm to 56.5 mm and the length of the reinforcing bar 202C changes from 48.3 cm to 83 cm, they are not affected by them. The diameter of the 11 mmΦ reinforcing bar 202C was measured accurately as 10.91 mm.

Needless to say, this third modification has the same effect as that of the embodiment described above.
In particular, in this modification, the length of the rod and the gradient calculated by the calibrating gradient calculation unit 510 are set as two axes for each of the plurality of parts whose dimensions of the subject body 202C are known and different. Find the straight line connecting the points corresponding to at least two measurement results on the length-gradient plane, and calculate the quadratic slope that is the slope of the straight line as a value based on the slope. A calculation unit 613 is provided, and the calibration unit 611 constructs a simultaneous equation from the relationship between the dimension and the quadratic gradient calculated for the dimension for each of a plurality of dimensions, and estimates the formula based on the solution. To formulate.
When the subject body 202C is a rod body and the length of the rod body is short, the dimensions have the length and gradient of the rod body as two axes rather than the gradient calculated as in the second modification. The relationship is proportional to the quadratic gradient, which is the gradient of the straight line connecting the points corresponding to the measurement results, corresponding to at least two correspondences between the length and the gradient on the length-gradient plane.
According to the above configuration, since the simultaneous equations are constructed from the relationship between the dimension and the quadratic gradient calculated for the dimension for each of the plurality of dimensions, the estimation formula includes the dimension. The relationship of the quadratic gradient is reflected.
Therefore, when the subject body 202C is a rod and the length of the rod is short, the influence of the measurement conditions is reduced, and the dimensions of the subject body 202C provided in the subject 2C can be measured with high accuracy. It is measurable.

The non-destructive inspection measurement system and the non-destructive inspection measurement method of the present invention are not limited to the above-described embodiments and modifications described with reference to the drawings, and various other methods are used within the technical scope thereof. A modified example can be considered.

For example, in the second and third modifications, the cross section of the subject body is circular, but other shapes such as quadrangular may be used. That is, the subject body may be a rod having a quadrangular cross section.
In this case, assuming that the dimension to be measured is the square of the difference between the diagonal length of the quadrangle of the reference size and the diagonal length of the cross section of the rod, the "2nd and 3rd modified examples" By setting the "diameter" to the "diagonal length", it is possible to construct a non-destructive inspection and measurement system corresponding to this case.

Further, in the first modification, the calibrating gradient calculation unit 410 applies a frequency higher than the frequency of the sinusoidal signal or the combined signal applied to the exciting coil 113 when calculating the gradient to the exciting coil and detects it. The voltage output from the coil 121 is measured to calculate the different frequency amplitude ratio, which is the amplitude ratio between this and the reference voltage, and the calibration unit 411 has a plurality of dimensions t2 and the dimensions t2 and the dimensions for each temperature. A simultaneous equation was constructed from the relationship between the value based on the gradient calculated for t2 and the different frequency amplitude ratio, and the estimation equation was formulated based on the solution. This is because, in a general metal, when the frequency is high, the fluctuation due to temperature has a larger amplitude ratio than a phase difference.
However, for example, when the subject body is formed of an alloy having high electrical resistance, or when the subject body is thin, the fluctuation due to temperature is higher than the amplitude ratio when the frequency is low. The phase difference may be larger. Therefore, the phase difference may be used as an index of temperature.
That is, the calibration gradient calculation unit applies a frequency different from the frequency of the sinusoidal signal or the composite signal applied to the exciting coil when calculating the gradient, and more specifically, a frequency lower than the frequency, and detects it. The voltage output from the coil is measured, and the different frequency phase difference, which is the phase difference between the voltage and the reference voltage, is calculated. A simultaneous equation may be constructed from the relationship between the value based on the gradient calculated in the above and the different frequency phase difference, and the estimation equation may be formulated based on the solution.
According to the above configuration, a frequency different from the frequency of the signal applied to the exciting coil when calculating the gradient in the calibration gradient calculation unit, more specifically, a frequency lower than the frequency is applied to the exciting coil. The voltage output from the detection coil is measured, the different frequency phase difference, which is the phase difference between this and the reference voltage, is calculated, and this is reflected in the simultaneous equations. When the frequencies are different, the phase difference is affected differently by the eddy current. Therefore, by constructing and solving simultaneous equations that reflect the phase differences of different frequencies, an estimation formula that appropriately considers the influence of temperature can be obtained. Can be set up.
Therefore, it is possible to reduce the influence of temperature and measure the dimensions of the subject body provided in the subject with high accuracy.

In addition to this, as long as the gist of the present invention is not deviated, the configurations given in the above-described embodiment and each modification can be selected or changed to other configurations as appropriate.

10, 40, 50, 60 Non-destructive inspection measurement system 1, 1C Sensor 112 Feedback coil 113 Excitation coil 121 Detection coil 3, 403, 503, 603 Measuring device 305, 405, 505, 605 Computer 310, 410, 510 Calibration time gradient Calculation unit 311, 411, 511, 611 Calibration unit 312, 412, 512, 612 Measurement unit 613 Calibration secondary gradient Calculation unit 2, 2C Subject 201 Outer can 201C Concrete 201a Outer surface 202 Inner can (subject body)
202C Reinforcing bar (subject body)
Distance from the Gap subject to the subject body

Claims (11)

An excitation coil provided in the subject to excite the subject body, a detection coil that outputs a voltage corresponding to a change in the magnetic field generated in the subject body when the subject body is excited by the excitation coil, and the above-mentioned In order to excite the subject body, a sine wave signal or a composite signal consisting of a plurality of sine waves having different frequencies is applied to the excitation coil, and the voltage output from the detection coil is detected to detect the subject body. A non-destructive inspection and measurement system including a measuring device for measuring the dimensions of the coil.
The measuring device is
For a plurality of parts of the subject body whose dimensions are known and different, the voltage output from the detection coil is measured under each of the plurality of different measurement conditions for each of the plurality of dimensions, and this and the reference voltage are used. The amplitude ratio and phase difference of the above are calculated, and a straight line connecting the points corresponding to at least two measurement results on the amplitude ratio-phase difference plane with the amplitude ratio and the phase difference as two axes is obtained, and the straight line is obtained. Amplitude gradient calculation unit that calculates the gradient,
A simultaneous equation is constructed from the relationship between the dimension and the value based on the gradient calculated for the dimension for each of the plurality of dimensions, and based on the solution, the dimension is measured at the time of measuring the dimension. And a calibration unit that formulates an estimation formula with a value based on the gradient as a variable.
Based on the estimation formula, a measuring unit that estimates and measures the dimensions of the part to be measured of the subject body,
It is equipped with a non-destructive inspection and measurement system. For each of the plurality of dimensions, the calibration unit formulates a plurality of linear equations representing the relationship between the dimensions and the value based on the gradient calculated for the dimensions. By solving as the simultaneous equations, a coefficient representing the relationship between the dimensions and the value based on the gradient is calculated, and the estimation formula is established by applying the coefficient with the value based on the gradient as the variable. The non-destructive inspection and measurement system according to claim 1, wherein the formula is formulated. The measuring unit measures the voltage output from the detection coil as the measurement voltage with respect to the part to be measured of the subject body, and measures the amplitude ratio and phase difference between this and the reference voltage. The time amplitude ratio and the measurement time phase difference are calculated, the measurement time gradient which is the gradient on the amplitude ratio-phase difference plane corresponding to these is calculated, and the value based on the measurement time gradient is calculated by the estimation formula. The non-destructive inspection measurement system according to claim 1 or 2, wherein the dimensions are calculated and measured by substituting into the variables of the above. The calibration time gradient calculation unit further calculates the intersections between the straight lines obtained for each of the plurality of dimensions.
The measuring unit calculates the gradient of the straight line connecting the measurement point and the intersection corresponding to the measurement amplitude ratio and the measurement phase difference on the amplitude ratio-phase difference plane as the measurement gradient. The non-destructive inspection and measurement system according to claim 3. The non-destructive inspection measurement system according to any one of claims 1 to 4, wherein the measurement condition includes the outer surface of the subject or the distance from the member constituting the outer surface to the subject body. The calibration time gradient calculation unit applies a frequency different from the frequency of the sine wave signal or the composite signal applied to the exciting coil when calculating the gradient to the exciting coil, and outputs the frequency from the detection coil. The voltage is measured, and the different frequency amplitude ratio, which is the amplitude ratio with the reference voltage, or the different frequency phase difference, which is the phase difference with the reference voltage, is calculated.
The calibration unit has a relationship between the dimension, a value based on the gradient calculated for the dimension, and the different frequency amplitude ratio or the different frequency phase difference for each of the plurality of dimensions and temperatures. The non-destructive inspection and measurement system according to any one of claims 1 to 5, wherein the simultaneous equations are constructed from the above and the estimation formula is formulated based on the solution. The subject body is a plate body, and the dimensions are the thickness of the plate body.
The value based on the gradient is the gradient.
The non-destructive inspection measurement system according to any one of claims 1 to 6, wherein in the simultaneous equations, the dimensions and the gradient are in a proportional relationship. The subject body is a rod with a circular cross section.
The dimension is the square of the difference between the diameter of the reference circle and the diameter of the cross section of the rod.
The non-destructive inspection measurement system according to any one of claims 1 to 6, wherein in the simultaneous equations, the dimensions and the value based on the gradient are in a proportional relationship. The subject body is a rod with a quadrangular cross section.
The dimension is the square of the difference between the diagonal length of a quadrangle having a reference size and the diagonal length of the cross section of the bar.
The non-destructive inspection measurement system according to any one of claims 1 to 6, wherein in the simultaneous equations, the dimensions and the value based on the gradient are in a proportional relationship. For a plurality of parts of the subject body whose dimensions are known and different, for each of the plurality of dimensions, the length of the rod and the length of the gradient calculated by the calibrating gradient calculation unit as two axes. -A quadratic gradient calculation unit during calibration that obtains a straight line connecting points corresponding to at least two measurement results on the gradient plane and calculates the quadratic gradient that is the gradient of the straight line as a value based on the gradient. With
The calibration unit constructs simultaneous equations from the relationship between the dimensions and the quadratic gradient calculated for the dimensions for each of the plurality of dimensions, and formulates the estimation formula based on the solution. The non-destructive inspection and measurement system according to claim 8 or 9. An excitation coil provided in the subject to excite the subject body, a detection coil that outputs a voltage corresponding to a change in the magnetic field generated in the subject body when the subject body is excited by the excitation coil, and the above-mentioned In order to excite the subject body, a sine wave signal or a composite signal consisting of a plurality of sine waves having different frequencies is applied to the excitation coil, and the voltage output from the detection coil is detected to detect the subject body. It is a non-destructive inspection measurement method that measures the dimensions of
For a plurality of parts of the subject body whose dimensions are known and different, the voltage output from the detection coil is measured under each of the plurality of different measurement conditions for each of the plurality of dimensions, and this and the reference voltage are used. The amplitude ratio and phase difference of the above are calculated, and a straight line connecting the points corresponding to at least two measurement results on the amplitude ratio-phase difference plane with the amplitude ratio and the phase difference as two axes is obtained, and the straight line of the straight line is obtained. Calculate the gradient,
A simultaneous equation is constructed from the relationship between the dimension and the value based on the gradient calculated for the dimension for each of the plurality of dimensions, and based on the solution, the dimension is measured at the time of measuring the dimension. To estimate, formulate an estimation equation with the value based on the gradient as a variable.
A non-destructive inspection measurement method for estimating and measuring the dimensions of a portion of the subject body to be measured based on the estimation formula.

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