JP2002181638A - Residual stress measuring device and method by x-ray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a residual stress measuring device and a method by X-ray causing little measuring errors even if the grain size of a measured material is unknown. SOLUTION: This device or measuring residual stress by X-ray is provided with an X-ray tube 1, an X-ray detector 2, support members 5, 7, motors 6, 8 and a control device 11, and irradiates the measured material 3 with X-rays to measure residual stress. The X-ray detector 2 is installed to be able to scan along the support member 5 by the motor 6, and the X-ray tube 1 is fixed to the support member 5. The support member 5 is formed in circular arc shape around the X-ray incident position 4 on the surface of the measured material 3 as a central point and installed at the support member 7 so as to be able to scan by the motor 8. The support member 7 is also formed in circular arc shape centering on the X-ray incident position 4. The control device 11 is composed of a CPU, a motor driver, a memory and an I/F circuit, and rotates the motors 6, 8 according to pulse signals sent from the moor driver. Signals from the X-ray detector 2 are received by the I/F circuit to compute the signals. The motors 6, 8 are stepping motors or the like driven by pulse every fixed angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray residual stress measuring apparatus and a measuring method therefor, and more particularly, to averaging diffraction angles obtained from diffraction intensity curves or synthesizing diffraction intensity curves to obtain diffraction angles. The present invention relates to an X-ray residual stress measuring device for determining an X-ray residual stress of a coarse-grained material and a measuring method thereof.

[0002]

^2. Description of the Related Art In order to accurately measure the residual stress of a coarse-grained material by the X-ray method (Sin ² ψ method), it is necessary to increase the irradiation area in order to increase the number of crystals contributing to diffraction, or to increase the sample or incident X-ray. It is necessary to swing the wire. Increase the irradiation area,
Alternatively, since the method of rocking the sample has a large restriction on the sample side, a method of rocking incident X-rays is generally used.
When the diffraction angle 2θ is measured and plotted with Sin ²変 数 as a variable, the relationship between 2θ and Sin ²と な り is theoretically a straight line, and the slope of this straight line is proportional to the stress on the material surface.

In a conventional X-ray stress measuring device, this 2θ-
In order to obtain a Sin ² ψ diagram (regression line), the position of the X-ray detector is operated while irradiating one point on the surface of the material to be measured with an X-ray beam, and the peak of the detected intensity is searched. The bending angle 2θ is determined, then the X-ray tube or the measurement material is moved to change the X-ray incident angle ψ, and the diffraction angle 2θ is determined in the same manner as described above. If the material to be measured is coarse, the swing method is used.

Normally, the incident direction of X-rays is set at an angle of 4 to 6 directions within a range of 0 to 45 degrees, and an optimum swing angle range corresponding thereto is to be determined according to the degree of coarse grains. However, this requires that the particle size of the measuring unit be known in advance. However, in many cases where the X-ray method is applied, the measurement is performed as received, and it is difficult to measure the particle size of the measurement unit without any processing. At present, it is determined with reference to the crystal grain size measured separately or separately. Japanese Patent Publication No. 6-54265 discloses an apparatus capable of accurately measuring stress even when a material having a large crystal grain or a texture is used.

[0005]

In the prior art described above, when the swing angle range is insufficient, the effect of the swing cannot be sufficiently obtained, and when the swing angle range is too large, the measurement is not performed. There was a problem that an error became large. further,
The device disclosed in the gazette performs biaxial swing, which leads to an increase in the cost of the device.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a small angle pitch X
From the data collected at the line incident angle, the measured stress value at which the confidence limit is minimized is determined, and the X
It is an object of the present invention to provide an apparatus and a method for measuring a residual stress in a wire.

[0007]

In order to achieve the above object, according to the present invention, an X-ray is applied to a material to be measured.
A X-ray tube, a detector for detecting X-rays diffracted on the material surface,
In an X-ray residual stress measuring apparatus comprising a rotating means for rotating a X-ray tube and a detector around a point of incidence on an X-ray material, and a control means for controlling the rotating means, the control means comprises: Means for detecting a diffracted X-ray by moving the detector to obtain a diffraction angle from a diffraction intensity curve of the obtained diffracted X-ray; means for obtaining a measured stress value at that time and a confidence limit for the measured stress value; Means for sequentially averaging the diffraction angles, means for obtaining a measured stress value at that time and a reliability limit for the measured stress value, and means for obtaining a residual stress value from the relationship between the number of averaged data, the measured stress value, and the reliability limit. It is characterized by having.

According to the present invention, there is provided an X-ray tube for irradiating an X-ray to a material to be measured, a detector for detecting X-rays diffracted on a material surface, and an X-ray tube. And an X-ray residual stress measuring device comprising: a rotating means for rotating the detector around an X-ray incident point on the material; and a control means for controlling the rotating means. Means for detecting a diffracted X-ray by moving a detector and obtaining a diffraction angle from a diffraction intensity curve of the obtained diffracted X-ray; means for obtaining a measured stress value at that time and a confidence limit for the measured stress value; Means for sequentially synthesizing, means for determining the diffraction angle from the diffraction intensity curve obtained as a result of the means for synthesizing, means for obtaining the measured stress value at that time and the confidence limit for the measured stress value, and the number of synthesized data Residue from the relationship between measured stress value and confidence limit Characterized by comprising means for determining the force values.

In order to achieve the above object, according to the present invention, the diffraction angles obtained from the diffraction intensity curves are sequentially averaged up to [the maximum number of collected data -2], or the diffraction intensity curves are obtained. It is characterized in that diffraction angles are sequentially obtained after synthesis. Thereby, depending on the magnitude of the difference between the diffraction intensities for each X-ray incident angle, whether to perform averaging or combining is selectively used.
Higher precision measurement is possible.

In order to achieve the above object, according to the present invention, the data when the confidence limit is minimized in the measured stress value and the confidence limit obtained from the averaged data number or the combined data number A feature is that a measured stress value corresponding to the number is set as a residual stress value to be obtained. Thereby, since the relationship between the number of data, the measured stress value, and the reliability limit can be plotted, the measured stress value corresponding to the number of data when the reliability limit is minimized can be easily determined.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 1 is a block diagram schematically showing an X-ray residual stress measuring apparatus according to the present invention. X-ray residual stress measurement device
Ray tube 1, X-ray detector 2, support members 5, 7, motor 6,
8. The control device 11 is provided, and the material 3 to be measured is irradiated with X-rays to measure the residual stress. The X-ray detector 2 is installed so as to be scannable along the support member 5 by the motor 6,
The wire tube 1 is fixed to a support member 5. The support member 5 is formed in an arc shape with the X-ray incident position 4 on the surface of the material 3 to be measured as a center point, and is installed on the support member 7 so as to be scannable by a motor 8.

The support member 7 is also formed in an arc shape centering on the X-ray incident position 4. The control device 11 is a CP
U, a motor driver, a memory, an I / F circuit, and the like. The motors 6, 8 are rotated according to a pulse signal sent from the motor driver. In addition, a signal from the X-ray detector 2 is received by an I / F circuit to calculate a signal. The motors 6 and 8 are stepping motors or the like that are driven at regular intervals by pulses.

Next, the operation of FIG. 1 will be described in detail. The X-ray generated by the X-ray tube 1 is formed into a fine beam by a solar slit (not shown), and constantly irradiates the X-ray incident position 4 on the surface of the material 3 during the measurement. An X
In order to obtain the diffraction angle 2θ with respect to the line incident angle ψ, it is necessary to drive the motor 6 by the control device 11 and scan the X-ray detector 2 so that the intensity distribution of the diffracted X-rays 10 is obtained. It is performed stepwise at a constant minute angle from the initial position.

Referring to FIG. 2, the movement of the incident X-ray will be described.
Will be explained. ψ₁~ Ψ_nIs the X-ray incidence setting angle.
In the embodiment, the angle is set from 0 degree to 45 degrees, and 45 degrees is measured when the measurement is completed.
Angle. First, the X-ray detector 2 is driven by the motor 6.
At a small angle from the initial position along the support member 5
Scan to find the intensity distribution of the diffracted X-rays 10
And the measurement of the X-ray incident angle of 0 degree is completed. Next,
The support member 5 is set along the support member 7 by the
Step the fixed angle by 5 degrees. This shows the X-ray tube and
X-ray detectors move while maintaining their relative positions.
You. And ψ ₂ス テ ッ プ steps₁Repeat as above,
The measurement of the X-ray incident angle of 5 degrees is completed. In this way ψ₁
~ Ψ_nMeasure up to ψ_nUntil 45 degrees
You.

[0016]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 shows X of the coarse-grained material of the present invention.
It is a flowchart of the calculation of the lowest Usui stress by the line method. First, an X-ray incident angle range (measurement start angle and end angle) and a pitch are set. Here the measurement start angle [psi ₁ of X-ray incidence angle range is set to 0 °, end angle [psi _n is 45 degrees. The pitch is set to 5 degrees (step S1). Next, the measuring instrument is moved to the measurement start angle. That motor 8, and the X-ray tube 1 to the position of the [psi ₁ 2, the supporting member 5 is set to 0 degree position (step S2). Next, X-ray tube 1
The X-ray detector 2 detects the diffracted X-rays 10 from the surface and irradiates the X-ray detector 10 with the X-rays. At this time, as described with reference to FIG. 2, the X-ray detector 2 is naturally stepped by a small angle (the smaller the better, but usually about 1/20 of the diffraction line width) between and after the X-ray detector 2 is obtained. Is stored in the memory of the control device 11 (step S3).

Thereafter, the X detector 2 is returned to the original position. Next, it is checked whether the X-ray incidence angle has reached the end angle of 45 degrees (step S4). If NO, the X-ray incident angle is moved by one pitch, that is, 5 degrees (step S5), and the step S5 is performed.
Return to 3. If YES, each diffraction angle is obtained from the diffraction intensity curve for each X-ray incidence (step S6).
The method of determining the diffraction angle may be any method such as a half width method, a peak top method, and a center of gravity method. To create a 2θ-Sin ² ψ diagram by plotting the peak position 2 [Theta] relative to Sin ² [psi in each [psi.

Next, the measured stress value at that time and the confidence limit for the measured stress value are determined. The stress value is 2θ−Sin ² ψ
The gradient of the diagram [M = δ (2θ) / δ (Sin ² ψ) (de
g)] and the following equation (1) (Step S)
7).

[0019]

(Equation 1)

The confidence limit for the measured stress value is calculated by the following equation (Step S7).

[0021]

(Equation 2)

The confidence limit is 68.3% as a standard, but another 50% or 90% may be used.
[The Japan Society for Materials Science, X-ray Material Strength Committee]
X-ray stress measurement method standard].

Next, the diffraction angle for each X-ray incidence angle is
Average from three with smaller corners (even with larger corners)
Then, the stress value and the confidence limit at that time are calculated. In addition,
The angle of incidence is the average of the angles of incidence of each diffraction intensity curve.₁,
ψ₂~ Ψ_nAnd Sin ²ψ₁, Sin²ψ₂~ S
in²ψ_n｛Sin with the mean of の mean
^-1(Ψmean)｝ 0.5 is defined as the angle of incidence (step
S8). Next, the averaged number is calculated from (maximum sampling data-2)
It is determined whether it is larger (step S10). If NO
The averaging number is increased by two (step S11), and step S8 is performed.
Return to If YES (7 in this case), the averaged
Plot the relationship between the number of data and the stress value and confidence limit.
Find each regression line (see FIG. 5) (step S1)
2). Finally, the measured stress value that minimizes the confidence limit is determined.
(Step S13).

FIG. 4 shows the diffraction angle with respect to the X-ray incident angle in the case of the average numbers 1, 3, 5, and 7 obtained based on the flowchart of FIG. 3, the measured stress value and the reliability limit of 68.3%. Is a table. However, the side inclination method and the stress constant were -100 MPa / 2θ degrees. FIG. 5 is a diagram in which the relationship between the number of averaged data in the table of FIG. 4, the stress value, and the confidence limit is plotted. From this figure, when the average number is five, the confidence limit of 68.3% is the smallest. In other words, it means that the width of the variation is narrow. The measured stress value at that time is the desired residual stress value.

Next, the second embodiment will be described with reference to FIG. Steps up to step S7 are the same as in the first embodiment, and a description thereof will be omitted. After obtaining the stress value and the reliability limit in the case of the average number 1 (step S7), the diffraction intensity curve for each X-ray incident angle is calculated from the smaller X-ray incident angle (even from the larger one). Each is synthesized, the diffraction angle is obtained from the synthesized diffraction intensity curve, and the stress value and the reliability limit at that time are calculated. The incident angle at that time is as described in the first embodiment. (Step S9).

Next, it is determined whether or not the combined number is larger than (maximum sampling data-2) (step S10). If NO, the averaging number is increased by two (step S11), and
Return to 9. If YES (7 in this case), the relationship between the number of synthesized data, the stress value, and the confidence limit is plotted, and respective regression lines are obtained (step S12). Finally, a measured stress value at which the reliability limit is minimized is set as a residual stress value to be obtained (step S13).

The first embodiment and the second embodiment have been described above. In each case, the method is effective as a method for measuring the residual stress. Then, the diffraction angle is obtained for each diffraction intensity curve measured at each X-ray incident angle, and the diffraction angles are averaged. In the second embodiment, the diffraction angle is obtained after the diffraction intensity curves are combined. The difference is whether or not the influence of the magnitude of the diffraction intensity at each X-ray incident angle is taken into consideration. In the first embodiment, when there is no large change (difference) in the diffraction intensity, the second embodiment uses the diffraction. This is effective when there is a difference in strength.

FIG. 6 is a diagram for explaining the difference between the first embodiment and the second embodiment. The first embodiment is a procedure in the case where no large difference is observed between the diffraction intensity curves at the incident angle. That is, since there is no large difference between the peak values of the X-ray incident angles A, B, and C, even if the diffraction angles are sequentially averaged to obtain the diffraction angles, no large error is produced in the result. The calculation procedure of the second embodiment is a procedure in the case where a large difference is observed between the diffraction intensity curves at the incident angle. That is, there is a large difference between the peak values of the X-ray incident angles A, B, and C, and in particular, there is a large difference between the X-ray incident angles A and B. In such a case, simply averaging results in a large error in the result. Then, when the diffraction intensity curves at the respective incident angles are sequentially synthesized, the peak value of the low waveform approaches the larger peak value side due to the characteristics of the waveform synthesis. By combining the waveforms using this characteristic, a diffraction angle with a small error can be obtained.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can be appropriately modified without departing from the gist of the present invention. Things. For example, in the present embodiment, the step angle of the X-ray tube is divided into 5 degrees, but may be larger or may be set as appropriate. Also,
Although the averaging or composite number is an odd number, an even number may be included.

[0030]

As described above, the X-ray residual stress measuring apparatus and the measuring method according to the present invention are obtained by averaging or synthesizing three diffraction angles or diffraction intensity curves for each X-ray incident angle. Therefore, the residual stress of the coarse particles can be measured accurately and with a simple device without swinging the two axes.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an X-ray residual stress measuring device of the present invention.

FIG. 2 is a diagram illustrating the movement of incident X-rays according to the present invention.

FIG. 3 is a flowchart of the calculation of the minimum stress of the coarse-grained material of the present invention by the X-ray method.

FIG. 4 is a table showing a diffraction angle with respect to an X-ray incident angle of the present invention, a measured stress value obtained, and a confidence limit of 68.3%.

FIG. 5 is a diagram for explaining a method of obtaining a minimum residual stress value according to the present invention.

FIG. 6 is a diagram illustrating the difference between the first embodiment and the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray tube 2 X-ray detector 3 Material to be measured 4 X-ray incident position 5 Support member 6 Motor 7 Support member 8 Motor 9 Incident X-ray 10 Diffracted X-ray 11 Controller

Claims (4)

[Claims] 1. An X-ray tube for introducing X-rays into a material to be measured, a detector for detecting X-rays diffracted on a material surface,
An X-ray residual stress measuring apparatus comprising: a rotating unit configured to rotate a X-ray tube and a detector around an X-ray incident point on a material; and an X-ray residual stress measuring device including a control unit configured to control the rotating unit. Means for detecting the diffracted X-rays by moving the detector with respect to the tube, obtaining a diffraction angle from a diffraction intensity curve of the obtained diffracted X-rays, and determining a measured stress value at that time and a confidence limit for the measured stress value. Calculating means, means for sequentially averaging the diffraction angles, means for obtaining a measured stress value at that time and a confidence limit for the measured stress value, and a relationship between the number of averaged data, the measured stress value, and the confidence limit. An X-ray residual stress measurement device comprising means for determining a residual stress value. 2. An X-ray tube for introducing X-rays into a material to be measured, a detector for detecting X-rays diffracted on a material surface,
An X-ray residual stress measuring apparatus comprising: a rotating unit configured to rotate a X-ray tube and a detector around an X-ray incident point on a material; and an X-ray residual stress measuring device including a control unit configured to control the rotating unit. Means for detecting the diffracted X-rays by moving the detector with respect to the tube and obtaining a diffraction angle from the diffraction intensity curve of the obtained diffracted X-rays; Obtaining means, means for sequentially synthesizing the diffraction angles, means for determining the diffraction angle from the diffraction intensity curve obtained as a result of the synthesizing means, and the measured stress value at that time and the confidence limit for the measured stress value Means for obtaining a residual stress value from a relationship between the number of synthesized data, the measured stress value, and the confidence limit. 3. An X-ray, wherein a diffraction angle obtained from a diffraction intensity curve is sequentially averaged up to [the maximum number of collected data−2], or a diffraction angle is obtained after sequentially synthesizing diffraction intensity curves. Residual stress measurement method. 4. The measured stress value and the confidence limit obtained from the averaged data number or the combined data number, wherein the measured stress value corresponding to the data number when the confidence limit is minimized is The X-ray residual stress measuring method according to claim 3, wherein the residual stress value is determined.