JP2009276095A - Non-destructive flaw detecting method and non-destructive flaw detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly perform the measurement of a wide range, for example, a range of ten several meters or above at once at a relatively low cost without stopping the operation of a structure or equipment and to provide a precise crack evaluating result. <P>SOLUTION: An oscillation sensor 120 and a detection sensor 124 are attached to the thickness T-part of a measuring target 104 so as to hold a section 104A to be measured in the measured length direction (X-direction) of the measuring target 104. The frequency F of the single frequency signal of a guide wave 102 is determined so that the wavelength λp of a longitudinal wave P becomes shorter than the width W of the measuring target 104 to be outputted. The outputted single frequency signal is converted in phase to transmit a transmission wave consisting of the longitudinal wave P and a transverse wave S as a false random signal, the guide wave 102 being the synthetic wave of the longitudinal wave P and the transverse wave S propagated through the section 104A to be measured is detected as a detection signal by a detection sensor 120 and the correlation of the false random signal and the signal according to the detection signal is taken to evaluate the crack 104B of the section 104A to be measured. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention combines a longitudinal wave and a transverse wave transmitted from an oscillation sensor, receives a guide wave observed in the vicinity of the surface of the measurement object with a reception sensor, and performs nondestructive flaw detection on the crack of the measurement object. In particular, the present invention relates to a non-destructive flaw detection method and an apparatus thereof capable of measuring a crack of a measurement object (steel material or concrete structure) at once in a wide range.

  If a large structure such as an overhead crane (called a girder crane), a bridge beam, or a rail used in an automobile factory or a steelworks collapses, it may cause significant damage. For this reason, it is extremely important to investigate the cracks in steel and concrete that cause collapse and the like by nondestructive flaw detection technology and evaluate the cracks.

  Among the nondestructive flaw detection techniques, the most common one using ultrasonic waves is a UT method (ultrasonic flaw detection method) for grasping reflected waves when a projected pulse wave is reflected at a crack. However, since the investigation range of the UT method is as narrow as several tens of centimeters, it took time to investigate cracks in structures having a length of more than a few tens of meters. Further, since it is necessary to grind and remove the paint on the surface of the steel material and to investigate in a quiet situation, for example, when working on the crane girder 104 of the girder crane, the operation of the girder crane is stopped (see FIG. 21), and it was necessary to reduce noise by blocking traffic on the bridge. For example, in order to inspect a girder crane that operates in the vicinity of a blast furnace at a steel works, the temperature of the furnace of the blast furnace is lowered and an investigation is performed, and then the investigation is performed, and then the furnace is returned to a high temperature again. It becomes. For this reason, a long period of time is required only by conducting an investigation, and a huge loss of costs is caused.

  In contrast to the above-described method using a pulse wave, a method using the property that a guide wave propagates over a surface of a structure over a long distance has been proposed. Patent Document 1 uses a plurality of sinusoidal burst waves, and Patent Document 2 uses a pulse compression method based on FM waves (continuous waves including a plurality of frequencies) to propagate a long distance by improving the S / N ratio. It describes how to make it happen.

  It is also possible to predict cracks by measuring stress using a strain gauge without using ultrasonic waves. This is a method of measuring stress by attaching a strain gauge to a location where stress is to be measured.

JP 2000-241397 A JP 2007-121092 A

  However, Patent Document 1 discloses the above-described problem that has been a problem in the conventional UT method from the viewpoint of shortening the wavelength of ultrasonic waves to obtain cracking accuracy and investigating extremely small cracks in a narrow range. It did not solve anything.

  In Patent Document 2, measurement is performed at a long distance of 21 m, but the reflected wave is measured using only the “power increase effect” by the pulse compression method. For this reason, although the S / N ratio is improved in the measurement results, sufficient measurement accuracy of cracks cannot be obtained because an appropriate wavelength is not used, and crack evaluation is insufficient.

  In other words, if it is assumed that sufficient measurement accuracy is obtained, the conventional problems of the UT method, such as a girder crane crane girder, a bridge beam, a rail, etc. Neither Patent Document 1 nor 2 solves that it is necessary to stop these operations and operations for a certain amount of time in order for operators to enter and measure the flaws of equipment. It was.

  Furthermore, in the method of attaching the strain gauge, since it is “measurement at a point” that basically measures the stress at the place where the strain gauge is attached, it was impossible to measure the section to be measured continuously. Even if the location where a crack occurs can be identified, the location can be enormous. That is, there is a problem that if a large amount of strain gauge is used, the result is extremely expensive.

  In view of the above circumstances, the present invention can quickly measure a range of more than 10 m at a wide range at a relatively low cost without stopping the operation and operation of structures and facilities, and with high accuracy. The present invention provides a nondestructive flaw detection method and a nondestructive flaw detection device that can provide good results.

  The invention according to claim 1 of the present application combines a longitudinal wave and a transverse wave transmitted from an oscillation sensor, receives a guide wave observed in the vicinity of the surface of the measurement object by the reception sensor, and In the non-destructive flaw detection method for non-destructive flaw detection, the oscillation sensor and the reception sensor are attached to the thickness portion of the measurement object with the measurement area in the length direction of the measurement object being measured. The frequency of the single frequency signal of the guide wave is determined and output so that the wavelength of the longitudinal wave is shorter than the width of the measurement object, and the output single frequency signal is phase-converted. A transmission wave composed of the longitudinal wave and the transverse wave as a pseudo-random signal is transmitted from the oscillation sensor, and a guide wave that is a combined wave of the longitudinal wave and the transverse wave that has propagated from the oscillation sensor to the section to be measured is received by the reception sensor. Received as a received wave at By correlating the signal in accordance with the random signal and the received wave is obtained by evaluating the crack 該被 measurement interval.

  The invention according to claim 2 of the present application uses the relationship between the correlation value obtained in advance and the crack length with respect to the correlation value between the pseudo-random signal and the signal according to the received wave. The length of the crack is determined.

  In the invention according to claim 3 of the present application, when the oscillation sensor and the reception sensor are attached to the measurement object via the attachment member, at least one of the material and thickness of the attachment member is changed. Thus, the frequency characteristics of the reception sensor are changed so as to match the frequency of the transmitted wave.

  In the invention according to claim 4 of the present application, the measurement object is a part of a girder crane, a bridge, or a rail, and is made of steel or concrete.

  The invention according to claim 5 of the present application also includes an oscillation sensor that transmits a longitudinal wave and a transverse wave as a transmitted wave, and a guide wave that is synthesized from the longitudinal wave and the transverse wave and is observed near the surface of the measurement object. In a nondestructive flaw detection apparatus having a reception sensor that receives a received wave and an analysis device that analyzes a crack of the measurement object based on the reception wave, a section to be measured in the length direction in which the measurement object is measured The oscillation sensor and the reception sensor are attached to the thickness portion of the measurement object with the frequency of the single frequency signal so that the wavelength of the longitudinal wave is shorter than the width of the measurement object. A frequency generator capable of determining and outputting the phase, a phase converter that converts the single frequency signal output from the frequency generator into a pseudo-random signal, and the pseudo-random signal and the received wave To correlate with signals that follow More, the there is provided a nondestructive inspection apparatus characterized by comprising means for evaluating the measured interval crack, a.

  In the invention according to claim 6 of the present application, the frequency generator further includes a wavelength of the longitudinal wave that is the same as a width of a support member that supports the measurement object integrally with the measurement object, or the same. Frequency determining means for determining the single frequency so as to be longer.

  Further, in the invention according to claim 7 of the present application, the analysis device obtains the relationship between the correlation value obtained in advance and the crack length with respect to the correlation value between the pseudo-random signal and the signal according to the received wave. And a calculation means for obtaining the length of the crack in the section to be measured.

  In the invention according to claim 8 of the present application, the oscillation sensor and the reception sensor are attached to the measurement object, and the material and thickness interposed between the measurement object and the oscillation sensor or the reception sensor are the same. By attaching at least one of them, an attachment member capable of changing the frequency characteristics of the reception sensor so as to match the frequency of the transmission wave is provided.

  In the invention according to claim 9 of the present application, the attachment member is an adhesive, clay, high-viscosity gel, or magnet.

  The guide wave is a wave propagating along a waveguide (meaning limited muscle path) formed by a physical boundary, and a longitudinal wave (P wave) and a transverse wave (S wave) that are body waves. Refers to the waves that are apparently obtained as a result of propagating the member (measurement object) so that the boundary condition is satisfied ('Guidelines and prospects of guide waves for nondestructive measurement' Nondestructive Inspection Vol. 52, No. 12, page 654) 2003).

  According to the present invention, the single frequency that is one of the boundary conditions is determined so that the wavelength of the longitudinal wave that synthesizes the guide wave together with the transverse wave is shorter than the width of the measurement object. While it is easy to evaluate the crack, the influence of attenuation by the measurement object is reduced, and measurement at a long distance becomes possible. In the evaluation of cracks, the frequency used is single, and the correlation between the pseudo-random signal and the signal according to the received wave is obtained, so that analysis can be performed with a high S / N ratio and a wide range at a time. It is possible to measure (all measured sections). In addition, the section to be measured is between the oscillation sensor and the reception sensor, and in the evaluation of cracks, basically a transmitted wave is used, so that a higher S / N ratio can be ensured. Furthermore, with the above-described configuration, it is possible to evaluate a crack with almost no influence on the operation state of the structure mounted on or in contact with the measurement object.

  In addition, when the relationship between the correlation value obtained in advance and the crack length is used for the correlation value between the pseudo-random signal and the signal according to the received wave, the crack evaluation, particularly the crack length, is easily obtained. be able to.

  In addition, if at least one of the material and thickness of the mounting member is changed, the frequency characteristics of the receiving sensor can be changed to match the frequency of the transmitted wave. Depending on the situation, it is possible to perform the most suitable measurement.

  Further, when the single frequency is determined so that the wavelength of the longitudinal wave is the same as or longer than the width (joining width) of the member that supports the measurement object integrally with the measurement object Even if there is a support member that integrally supports the measurement object, the analysis can be performed with a high S / N ratio without being affected by them.

  That is, even if the length of a measurement object such as a girder of a girder crane, a girder of a bridge, a beam of a bridge, a rail, or the like is 10 or more meters, the operator does not enter, You can easily grasp the cracks at once without stopping the operation.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing a nondestructive flaw detector according to a first embodiment of the present invention, FIG. 2 is a schematic diagram showing how a waveform output mainly from a frequency generator is phase-converted, and FIG. 3 is a guide. 4 is a schematic diagram showing an example of a wave propagation model, FIG. 4 is a schematic diagram conceptually showing attenuation when the wavelength of the body wave does not match the width of the object to be measured, and FIG. FIG. 6 is a conceptual diagram illustrating attenuation of a guide wave when there is a crack, and FIG. 7 is a non-destructive flaw detection method. FIG. 8 is a perspective view of the crane girder, FIG. 9 is a schematic diagram showing the mounting positions of the oscillation sensor and the reception sensor, and FIG. 10 shows the mounting positions of the oscillation sensor and the reception sensor in detail. Fig. 11 shows the joint width of the gusset plate attached to the crane girder. FIG. 12 is a diagram showing the influence of the function value (sound pressure) on the amplitude, FIG. 12 is a diagram showing the difference in the waveform of the correlation value (sound pressure) depending on the presence or absence of cracks in the crane girder, and FIG. 14 shows how the amplitude of the value (sound pressure) changes, FIG. 14 summarizes the relationship between the change of the correlation value (sound pressure) and the crack length, and FIG. 15 shows the correlation value (in the verification B of FIG. It is a figure which shows the waveform of (sound pressure).

  First, the overall configuration of the nondestructive flaw detection apparatus according to the present embodiment will be described mainly using FIG.

  As shown in FIG. 1, the nondestructive flaw detection apparatus 100 is composed of an oscillation sensor 120 that transmits a longitudinal wave P and a transverse wave S as transmitted waves, and the longitudinal wave P and the transverse wave S that are combined to generate near the surface of the measurement object 104. A reception sensor 124 that receives the observed guide wave 102 as a reception wave, and an analysis device 132 that analyzes the crack 104B of the measurement object 104 based on the reception wave. The nondestructive flaw detection apparatus 100 is configured such that the oscillation sensor 120 and the reception sensor 124 have a thickness T portion of the measurement object 104 across the measurement area 104A in the length L direction (X direction) of the measurement object 104 measured. And a frequency generator 112 capable of determining and outputting the frequency F of a single frequency signal so that the wavelength λp of the longitudinal wave P is shorter than the width W of the measurement object 104, and a frequency generator A phase converter 114 that converts a single frequency signal output from 112 into a PRBS signal (described later) which is one of pseudo-random signals and obtains a correlation between the PRBS signal and a signal according to the received wave. Means for analyzing the crack 104B of the section to be measured 104A (analyzer 132).

  For this reason, the guide wave 102 synthesized from the longitudinal wave P and the transverse wave S transmitted from the oscillation sensor 120 and observed near the surface of the measurement object 104 is received by the reception sensor 124 as a reception wave, and the measurement object The crack 104B of the object 104 can be detected nondestructively.

  Below, each component is demonstrated in detail.

  As shown in FIG. 1, the measurement object 104 has a shape that can be defined by a thickness T, a width W, and a length L. For example, the measurement object 104 has a length L direction (also referred to as a measurement direction or an X direction). Is a rectangular parallelepiped shape having a length L longer than a thickness T and a width W. When the oscillation sensor 120 and the reception sensor 124 are attached to the measurement object 104, basically, the transmitted wave of the guide wave 102 is used to detect the crack 104B existing in the measured section 104A therebetween. Will be. For this reason, the signal amplitude of the received wave is large, and a high S / N can be secured.

  The measurement object 104 may be attached with a support member 108 (see FIGS. 8 and 11) that supports the measurement object 104 integrally with the measurement object 104, for example, by welding. At this time, it is preferable to determine the single frequency F in consideration of the shape of the support member 108, that is, the bonding width (width) GW.

  The frequency generator 112 can digitally output a carrier signal, which is a continuous sine wave signal having an arbitrary frequency (single frequency F), as a single frequency signal. Further, the frequency generator 112 has a wavelength λp of the longitudinal wave P for synthesizing the guide wave 102 together with the transverse wave shorter than the width W of the measurement object 104 and is integrated with the measurement object 104. Frequency determining means for selecting and determining a single frequency F of the guide wave 102 so as to be equal to or longer than the joining width (width) GW of the support member 108 that supports The frequency determining means can be constituted by a circuit including a CPU, for example.

  In this embodiment, the longitudinal wave P does not propagate unless the junction width (width) GW of the support member 108 is sufficiently large with respect to the wavelength λp of the longitudinal wave P. Even if the (width) GW is twice the wavelength λp, preferably 1.5 times the wavelength λp, it is determined that the wavelength λp is equal to or longer than the junction width (width) GW.

The phase converter 114 is connected to the frequency generator 112, phase-converts a single frequency F digital signal (single frequency signal) output from the frequency generator 112 with a PRBS code, and generates a pseudo-random signal. Is output to the DA converter 116. This output is also made to the analysis device 132. Here, the PRBS code is a pseudo-random binary sequence (Psudo-Random Binary Sequence) code. For example, the period of the code sequence generated by the shift register in the phase converter 114 and feedback is the longest. An M-sequence (longest sequence; Maxmal-Length Sequences) that is a sequence is used. For this reason, the PRBS code is 4095 wave numbers when (2 ⁿ −1), for example, n = 12, and the exclusivity is extremely strong. Therefore, when autocorrelation is taken, coupled with the advantages of the pulse compression technique, the correlation value peak is high and the S / N ratio is very high.

  Specifically, FIG. 2 shows a case where the relationship between the continuous sine wave, the PRBS code, and the PRBS signal, which is the result of phase conversion, is represented by an analog waveform. 2A shows a PRBS code, FIG. 2B shows a continuous sine wave output from the frequency generator 112, and FIG. 2C shows a PRBS signal obtained by phase conversion of the continuous sine wave by the PRBS code. . In the present embodiment, phase conversion is performed by rotating the phase by 180 ° with a value of “1” of the PRBS code and with the phase as it is with a value of “0”. As a result, the waveform shown in FIG. 2B is phase-converted, and the PRBS signal shown in FIG. 2C is output. FIG. 2D shows a waveform when the autocorrelation of the waveform of FIG. Thus, the phase converter 114 phase-converts the single frequency signal of the frequency F input from the frequency generator 112 with the PRBS code generated inside itself. The PRBS code may be introduced from the outside.

  The DA converter 116 is connected to the phase converter 114, converts the signal output from the phase converter 114 from a digital value to an analog value, and outputs the analog value.

  The oscillation amplifier 118 is connected to the DA converter 116 and amplifies the signal output from the DA converter 116 in an analog manner and outputs the amplified signal.

  The oscillation sensor 120 is connected to the oscillation amplifier 118, converts the electrical signal output from the oscillation amplifier 118 into mechanical vibration, and outputs a longitudinal wave P and a transverse wave S that are transmission waves. The receiving sensor 124 receives the guide wave 102 synthesized by the longitudinal wave P and the transverse wave S, which are mechanical vibrations propagating from the oscillation sensor 120 through the measured section 104A, as a received wave, and converts it into an electrical signal. To do. The oscillation sensor 120 and the reception sensor 124 are attached to a thickness T portion of the measurement object 104 with a measurement section 104A in the length L direction (X direction) of the measurement object 104 measured. For example, a piezoelectric element can be used for the oscillation sensor 120 and the reception sensor 124. For this reason, the oscillation sensor 120 can output an accurate output.

  The attachment member 122 attaches the oscillation sensor 120 and the reception sensor 124 to the measurement object 104, and is interposed between the oscillation sensor 120 or the reception sensor 124 and the measurement object 104 at that time. By changing the material and thickness of the attachment member 122, the frequency characteristic of the reception sensor 124 is matched to the frequency of the oscillation wave with respect to the frequency of the transmission wave transmitted from the oscillation sensor 120 as a result. Can be changed. For example, when the thickness of the mounting member 122 between the oscillation sensor 120, the reception sensor 124, and the measurement object 104 is small (or a hard material) is increased (or changed to a soft material), the transmitted wave is changed. On the other hand, the frequency of the received wave to be matched can be lowered. The adjustment range can be several tens kHz to 100 kHz. As the attachment member 122, an adhesive, clay, a highly viscous gel, a magnet, or the like can be used. By interposing the mounting member 122, it is possible to perform matching of acoustic impedance, and thus it is possible to analyze the received wave at the optimum frequency.

  In addition, the acoustic impedance Z can be calculated | required by Formula (1).

    Z = ρ * V (1)

  Here, ρ is the density of the substance, and V is the speed of sound in the substance. In addition, when sound propagates between different substances, it can be expressed by Equation (2).

A = 2 * Z1 / (Z1 + Z2) * A0 (2)
Z1 = ρ1 * V1 (3)
Z2 = ρ2 * V2 (4)

  Where A is the amplitude after propagation from substance I to substance II, A0 is the amplitude in substance I, ρ1 is the density of substance I, V1 is the velocity of sound in substance I, ρ2 is the density of substance II, and V2 is The speed of sound in substance II is shown. As is clear from this, since the acoustic impedance obtained from the density ρ and the sound velocity V is closer when clay is used than when the air is passed between the oscillation sensor 120 and the reception sensor 124, Attenuation of amplitude is reduced. Then, by adjusting the material and thickness of the attachment member 122, it is possible to perform measurement that is optimal for the case at the measurement site.

  The reception filter 126 is connected to the reception sensor 124 and removes, for example, noise related to girder crane operation and noise related to road traffic on the bridge from the signal received by the reception sensor 124. For this reason, by selecting an appropriate noise filter, the influence of these operations and operations can be greatly reduced, and the received wave can be analyzed. Note that a variable amplifier may be provided as necessary.

  The AD converter 128 is connected to the reception filter 126 and converts a signal that has passed through the reception filter 126 from an analog value to a digital value.

  The data recorder 130 is connected to the AD converter 128 and records the signal output from the AD converter 128.

  The analyzing device 132 is connected to the phase converter 114 and the data recorder 130, and follows the PRBS signal (pseudorandom signal) related to the transmitted wave output from the phase converter 114 and the received wave recorded in the data recorder 130. Calculate the correlation value with the signal. By taking this correlation, the calculation result can be handled as a pulse wave (see FIG. 2D), and the arrival time of the guide wave 102 and the amplitude of the correlation value can be measured. Here, depending on the length CL of the crack 104B of the measurement object 104, the arrival time of the guide wave 102 and the amplitude of the correlation value change. For this reason, the analysis device 132, as a calculation means, based on the relationship between the amplitude of the correlation value obtained in advance and the length CL of the crack 104B, the length CL of the crack 104B, in particular the measurement, from the amplitude of the obtained correlation value. The length CL of the crack 104B penetrating in the thickness T direction of the object 104 can be obtained. That is, the analysis device 132 can evaluate the crack 104B in the measured section 104A with a high S / N ratio using the pulse compression technique. Alternatively, the analyzer 132 can be said to be a means for evaluating the crack 104B in the measured section 104A by correlating the PRBS signal related to the transmitted wave and the signal following the received wave. Here, the evaluation includes not only obtaining the above-described length CL of the crack 104B but also estimating the position and width of the crack 104B from the change in arrival time, and conversely, attenuation of the amplitude of the correlation value. This may include determining only the presence or absence of the crack 104B from the amount.

  Next, the relationship between the guide wave 102, the single frequency F, and the width W will be described below.

  As described above, the guide wave 102 is a wave propagating along a waveguide formed by a physical boundary (meaning limited muscle path), and the longitudinal wave P and the transverse wave S, which are the body wave 103, are the boundary. A wave that is apparently obtained as a result of propagating a member to satisfy a condition. That is, the guide wave 102 is a wave that is observed in the vicinity of the surface of the measurement object 104 as a result of propagation and synthesis of the longitudinal wave P and the transverse wave S. As shown in FIG. 3A, a transmitted wave transmitted from the oscillation sensor 120 propagates as indicated by a broken line in the body wave 103 contributing to the guide wave 102 in the measurement object 104 around the oscillation sensor 120. As shown in FIG. 3B, the guide wave 102 is observed as a movement indicated by a broken line at each of the points X1, X2, and X3 on the surface of the measurement object 104 when the boundary condition is satisfied.

  That is, as the body wave 103, it is necessary to select and determine an appropriate wavelength (an appropriate single frequency F) with respect to the width W of the measurement object 104. If the body wave has an appropriate wavelength λ1, the body wave 103A propagates long without being attenuated in the X direction while being reflected in the width W direction, as shown on the left side of FIG. Observed at the end face). However, when the body wave has a long wavelength λ2 that is not properly matched with the width W of the measurement object 104, the body wave 103B may propagate without satisfying the boundary condition in the width W direction. Not possible (right side of Fig. 4).

  Here, in general, among the body waves 103, 103A, and 103B, the longitudinal wave P has a higher sound speed than the transverse wave S, and therefore the wavelength λp of the longitudinal wave P is longer than the transverse wave S. Considering the longitudinal wave P, if the longitudinal wave P has an inappropriate wavelength λ2 in FIG. 4, the longitudinal wave P cannot propagate. That is, in this case, even if the transverse wave S propagates, the guide wave 102B synthesized by the longitudinal wave P and the transverse wave S cannot be observed.

  From the above, the following relationship can be obtained for the longitudinal wave P.

    W >> λp (5)

  Since the wavelength λp can be obtained from the value obtained by dividing the sound velocity Vp of the longitudinal wave P by the single frequency F, the equation (5) can be expressed by the following relationship.

    W >> Vp / F (6)

  Here, the sound velocity Vp of the longitudinal wave P is about 5.7 km / s when the measuring object 104 is a steel material.

  That is, when the measurement object 104 is a steel material and its width W is 40 cm, the single frequency F needs to be much larger than 14.25 kHz. In the present embodiment, as a preferable condition, the size is about 30 kHz or more assuming that the size is about twice.

  Specifically, FIG. 5 shows the difference in the amplitude of the correlation value obtained by the difference in the single frequency F when the measurement object 104 is a steel material and the width W is 40 cm. As shown in FIG. 5B, when the single frequency F is not matched and is inappropriate (4 KHz), the amplitude waveform of the correlation value collapses, and the distance between the oscillation sensor 120 and the reception sensor 124 increases. The arrival time of the arrow position corresponding to a certain measurement distance cannot be accurately indicated. On the other hand, as shown in FIG. 5A, when the single frequency F is appropriate (31 KHz), when the measurement distance that is the distance between the oscillation sensor 120 and the reception sensor 124 is changed, It can be seen that the analysis device 132 calculates the amplitude of the correlation value that faithfully represents the distance.

  Further, as shown in FIG. 6A, when the crack 104B exists in the measurement object 104, a part 103C of the body wave 103 is reflected by the crack 104B, and the other side of the crack 104B (FIG. 6 ( In A), it does not propagate to the right side). For this reason, if there is a crack 104B, the guide wave 102B attenuates. This amount of attenuation is related to the fact that the width of propagation of the body wave 103 is reduced according to the length CL of the crack 104B. When the crack 104B is a closed crack, as shown in FIG. 6B, the wave energy of the guide wave 102 vibrates the closed surface of the crack 104B to generate friction, and part of the wave energy is heated. Converted into energy. As a result, in the case of a closed crack, the attenuation of the guide wave 102 is larger than that of the open crack.

  Next, a nondestructive flaw detection method according to the present embodiment will be described with reference to FIG. 7 focusing on a method for determining a single frequency F.

  First, the oscillation sensor 120 and the reception sensor 124 are attached to the thickness T portion of the measurement object 104 with the measured section 104A in the length L direction (X direction) to be measured of the measurement object 104 interposed therebetween (step S2). .

  Next, the single frequency F of the guide wave 102 is determined and output so that the wavelength λp of the longitudinal wave P is shorter than the width W of the measurement object 104. This process is broken down as follows.

  First, the frequency Fp1 of the wavelength λp1 of the longitudinal wave P corresponding to the width W of the measurement object 104 is derived from the equation (6) (step S4). At this time, the relationship is indicated by an inequality sign in Equation (6), but it is determined that it is connected by an equal sign.

  Next, when there is the support member 108, the frequency Fp2 of the wavelength λp2 of the longitudinal wave P corresponding to the width GW is derived from the equation (6) (step S6). Again, in Equation (6), the relationship is indicated by an inequality sign, but it is determined that it is connected by an equal sign.

  Next, a single frequency F sufficiently larger than the frequency Fp1 is selected (step S8).

    Fp1 << F (7)

  Here, in the present embodiment, the sufficiently large condition is about twice or more. As described above, in this embodiment, even when the junction width (width) GW is twice the wavelength λp, preferably 1.5 times the wavelength λp, the wavelength λp is the same as the junction width (width) GW. Or longer than that. For this reason, a single frequency F is allowed to be not more than twice, preferably not more than 1.5 times the frequency Fp2. At the time of selection, if the single frequency F is large, the guide wave 102 is easily attenuated, but is sensitive to a smaller crack 104B. On the contrary, if the single frequency F to be selected is small, the guide wave 102 is less sensitive to the small crack 104B, but is not easily attenuated, and can be measured over a longer distance.

  Next, the validity of the single frequency F is verified (step S10). Specifically, confirmation of the actual influence on the guide wave 102 by the support member 108, confirmation of the signal intensity of the reception wave at the reception sensor 124, sensitivity verification for the length CL of the crack 104B to be measured, Reference is made to those experimental data or simulation results. If not valid (No in step S10), a single frequency F is selected again in step S8. Note that this step can be omitted by selecting a single frequency F in consideration of experimental data and actual measurement data in step S8.

  Next, if the verification result is valid (Yes in step S10), the frequency F of the single frequency signal is determined, and the frequency generator 112 outputs the single frequency signal (step S12).

  Until the determination of the single frequency F mentioned above is shown as a specific example below.

  When the measurement object 104 is a steel material, the width W is 40 cm, and the sound speed of the longitudinal wave P of the guide wave 102 is 5.7 km / s, the frequency Fp1 is 14.25 kHz using the equation (6).

  When the width GW of the support member 108 is longer than the length GL and is 20 cm at the maximum, the frequency Fp2 is 28.50 kHz using the equation (6).

  In the present embodiment, the single frequency F can be selected to 31 kHz from two times or more of the frequency Fp1 and 1.5 times or less which is a more preferable condition of the frequency Fp2. Here, since the determination of the single frequency F is based on actually measured data or the like, verification of the validity after this is omitted, and the single frequency F is determined to be 31 kHz.

  Thereafter, returning to the flowchart of FIG. 7, the description of each step is continued.

  Next, the phase converter 114 converts the single frequency F generated by the frequency generator 112 into a PRBS signal (step S14).

  Next, the signal that has been phase-converted into the PRBS signal is transmitted by the oscillation sensor 120 via the DA converter 116 and the oscillation amplifier 118 (step S16).

  Next, the reception sensor 124 receives the guide wave 102, which is a composite wave of the longitudinal wave P and the transverse wave S, propagated from the oscillation sensor 120 through the measured section 104A of the measurement object 104 (step S18).

  Next, the received wave is recorded in the data recorder 130 via the reception filter 126 and the AD converter 128. Then, the signal according to the recorded reception wave is correlated with the PRBS signal related to the transmission wave output from the phase converter 114 in the analysis device 132, and a value is calculated (step S20).

  Next, based on preliminary experiments, past measurement results, simulations, or the like, a correlation value (hereinafter simply referred to as a correlation value) between a PRBS signal related to a transmission wave obtained in advance and a signal according to a reception wave is measured. A table relating the length CL of the crack 104B with the same width W in the object 104 is referred to (step S22).

  Next, as a result of referring to the table, the crack 104B in the measured section 104A is evaluated by obtaining the length CL of the crack 104B.

  Next, the present embodiment will be described using a specific application example. In this application example, unless otherwise specified, the width W of the crane girder 106 as the measurement object is 40 cm, and the single frequency F is 31 kHz.

  FIG. 8 shows a crane girder 106 constituting a girder crane, a gusset plate (support member) 108 for fixing and supporting the crane girder 106 to a structure (not shown) such as a building that houses the girder crane, and a crane girder. A support column 107 that supports 106 upward is shown. As shown in FIG. 9, the oscillation sensor 120 and the reception sensor 124 of this embodiment are attached to each end where the crane girder 106 and the crane girder 106 are adjacent to each other, and the wiring is gathered in one place by the cable CA. Yes. As shown in FIG. 10, the crane girder 106 is an I-shaped steel and includes a bottom plate 106X, an intermediate plate 106Y, and an upper plate 106Z. Although these are integrally formed, they are perpendicular to each other, and the bottom plate 106X and the upper plate 106Z are connected to the intermediate plate 106Y in the middle. Therefore, as shown in FIG. 10, by attaching the oscillation sensor 120 and the reception sensor 124 to the thickness T portion of the bottom plate 106X via the attachment member 122, it is possible to accurately measure only the bottom plate 106X as a measurement object. it can.

  As described above, the crane girder 106 is attached with a gusset plate (support member) 108 for fixing and supporting a structure such as a building for housing the girder crane. The gusset plate 108 is a support member that supports the crane girder 106 by being welded and integrated with the crane girder 106 that is the measurement object 104. Therefore, FIG. 11 shows the result of examining the influence of the gusset plate 108 on the correlation value.

  FIG. 11A shows the relationship between the joint width (width) GW of the crane gutter 106 and the gusset plate 108 and the bottom plate 106X of the crane girder 106. And the result obtained by the measurement is shown in FIG. As shown in FIG. 11B, when the single frequency F is 31 KHz, even if the junction width (width) GW changes from 0 to 200 mm, it does not affect the amplitude of the correlation value. .

  More specifically, when the junction width (width) GW is 200 mm and the single frequency is F31 kHz, the wavelength λp is numerically smaller than the junction width (width) GW (λp (184 mm) <GW (200 mm)). However, as described above, it has been confirmed that even the bonding width (width) GW of 200 mm has no influence on the amplitude of the correlation value. That is, it is satisfied that the wavelength λp is 1.5 times or less of the preferable condition with respect to the junction width (width) GW.

  Thus, by considering the junction width (width) GW at the stage of determining the single frequency F, the amplitude of the correlation value is not affected by the gusset plate 108. That is, it is shown that the crack 106B can be easily evaluated even when the crack 106B has occurred in the welded portion of the gusset plate 108.

  Next, FIG. 12 shows the result of examining whether or not there is a difference in the amplitude of the correlation value when the crane girder 106 has and does not have the crack 106B. FIG. 12A shows the arrangement of the oscillation sensor 120 and the reception sensor 124 for the bottom plate 106X without the crack 106B and the top plate 106Z with the large crack 106B, and FIG. 12B shows the correlation values obtained respectively. Is shown. When the distance (measurement section 106A) between the oscillation sensor 120 and the reception sensor 124 is 16.54 m and the single frequency F is 31 KHz, the guide wave 102 is extremely attenuated in the upper plate 106Z having the crack 106B. Thus, it can be seen that the waveform of the correlation value cannot be observed at the time corresponding to the distance of 16.54 m.

  FIG. 13 shows the relationship between the length CL of the crack 106B and the correlation value. FIG. 13A shows the arrangement of the length CL of the crane girder 106 and the crack 106B formed therein, and FIG. 13B shows the change in the correlation value waveform when the length CL of the crack 106B is changed. ing. As can be seen from this figure, when the length CL of the crack 106B increases, the amplitude of the correlation value at the arrow position indicating the distance between the oscillation sensor 120 and the reception sensor 124 decreases, and the length CL of the crack 106B exceeds 50 mm. Then, it becomes impossible to observe the waveform of the correlation value. The circled portion is a waveform that was not observed when there was no crack 106B (0 mm), and is considered to be the influence of reflection of the body wave by the crack 106B. It is possible to analyze the crack 106B by processing this waveform.

  In FIG. 14, four experiments similar to FIG. 13 are performed (cases 1 to 4), and the relationship between the change in the correlation value (sound pressure) and the length CL of the crack 106B is shown. From the four experimental results, it can be seen that there is a substantially constant relationship between the change in the correlation value (sound pressure) and the length CL of the crack 106B. In order to verify these relations, verification experiment results verified in a yard that is not the length CL of the artificially created crack 106B and is not in a laboratory-level environment are shown as verifications A and B in FIG. At the same time. The verification A is a result when only the crane girder 106 exists. Verification B is a result in a state where the crane CR is actually moved. All of these are plotted on data representing the relationship between the change in the correlation value (sound pressure) obtained from the four experimental results and the length CL of the crack 106B. That is, the relationship between the change in the correlation value (sound pressure) and the length CL of the crack 106B proves that it is stable. That is, by using the obtained correlation value (sound pressure) and the relationship between the previously obtained correlation value (sound pressure) and the length CL of the crack 106B in the form of a table, for example, the oscillation sensor 120 and the reception sensor It is possible to easily obtain the length CL of the crack 106 </ b> B in the measured section 106 </ b> A with respect to 124.

  FIG. 15 shows the arrangement of verification B and the correlation value waveform at that time. At this time, the length CL of the crack 106B is confirmed based on the conventional UT method. 15A is a top view showing the positional relationship among the oscillation sensor 120, the reception sensor 124, the crane girder 106, and the crane CR, and FIG. 15B is a correlation value for each crane girder 106 (CG1 to CG4). (Sound pressure) waveform. From the results, the amplitude of the correlation value (sound pressure) in CG1 and CG4 exceeds 110 dB, which is more than three times the amplitude of CG2 (100 dB). CG3 is about 70 dB, which is 1/100 the amplitude of CG1 (CG4). Since the length L of the crane girder 106 (CG1 to CG4) at this time is 18 m, it can be seen that the presence / absence of the crack 106B and the length CL can be easily grasped within that range.

  As is clear from the actual results described above, the measurement object 104 (crane girder 106) has a single frequency F that is one of the boundary conditions, and the wavelength λp of the longitudinal wave P that synthesizes the guide wave 102 together with the transverse wave S. Therefore, the cracks 104B and 106B can be easily evaluated, but the influence of attenuation by the measurement object 104 (crane girder 106) can be reduced and Measurement is possible. In the evaluation of the cracks 104B and 106B, the frequency F to be used is single, and the PRBS signal which is a pseudo-random signal is correlated with the signal according to the received wave, so the analysis is performed with a high S / N ratio. It is possible to measure a wide range (all measured sections 104A and 106A) at a time. In addition, the measured sections 104A and 106A are located between the oscillation sensor 120 and the reception sensor 124, and in the evaluation of the cracks 104B and 106B, basically a transmitted wave is used, so a higher S / N ratio is secured. can do. Furthermore, with the above-described configuration, the cracks 104B and 106B can be evaluated with almost no influence on the operation state of a structure such as a crane mounted on or in contact with the measurement object 104 (crane girder 106).

  Further, since the correlation value obtained in advance and the length CL of the cracks 104B and 106B are used for the correlation value between the PRBS signal which is a pseudo-random signal and the signal according to the received wave, the cracks 104B and 106B Evaluation, in particular, the length CL of the cracks 104B and 106B can be easily obtained.

  In addition, when at least one of the material and thickness of the mounting member 122 is changed, the frequency characteristics of the reception sensor 124 can be changed so as to match the frequency of the transmitted wave. Optimal measurement can be performed flexibly according to the object.

  Further, the wavelength λp of the longitudinal wave P is integrated with the measurement object 104 (crane girder 106) and the joint width (width) GW of the support member (gusset plate) 108 that supports the measurement object 104 (crane girder 106). Since the single frequency F is determined so as to be the same or longer, even if there is a support member (gusset plate) 108 that integrally supports the measurement object 104 (crane girder 106), those frequencies The analysis can be performed with a high S / N ratio without being affected.

  That is, flaw detection of structures and equipment, for example, in a girder crane using the crane girder 106 shown in the specific embodiment, it is easy to grasp cracks at once without entering an operator or stopping operation and operation. can do.

  In this embodiment, as shown in FIG. 9, the oscillation sensor 120, the reception sensor 124, and the like are attached to the end of the crane girder 106, and they are connected by the cable CA and brought to the lower side of the column 107 of the girder crane. Measurement (time required for one measurement is 1 minute or less) can be performed. In other words, the present embodiment enables continuous measurement at short time intervals, and by accurately attaching the distance between the oscillation sensor 120 and the reception sensor 124, accurate measurement using the arrival time and the amplitude of the correlation value is possible. Evaluation of the crack 106B is possible. Such measurement can be performed on, for example, important and aged facilities, and places that cannot be easily approached due to high places such as steel and high heat. In the end, the cable CA can be extended to the monitor room for measurement, and continuous measurement and automatic measurement can be performed.

  However, although the present invention has been described with reference to the first embodiment, the present invention is not limited to the first embodiment. That is, it goes without saying that improvements and design changes can be made without departing from the scope of the present invention.

  For example, as shown in the second embodiment shown in FIG. 16, it is possible to adopt a simple monitoring method in which the oscillation sensor 120 and the reception sensor 124 are fixed to the tip of the rod-shaped jig SS and brought into contact with the measurement object 106. It is. In this case, the distance between the oscillation sensor 120 and the reception sensor 124 may vary slightly, but since there is almost no change in the amplitude of the correlation value due to the variation in distance, the amplitude of the crack 106B is utilized using the amplitude of the correlation value. The length CL can be calculated with high accuracy. This embodiment can target, for example, facilities that are not important but have deteriorated, and specifically, crane facilities in places where people can easily approach, such as warehouses that store products and the like. It is possible to target.

  In the above-described embodiment, the measurement object 104 is the crane girder 106, but the present invention is not limited to this. As described above, since the crack length can be determined only by the result of the amplitude of the correlation value, it is not necessary to strictly measure the distance between the oscillation sensor 120 and the reception sensor 124, so there is an obstacle. When the line of sight is poor, the structure itself is bent (the bridge beam portion as shown in FIG. 20), or when the structure itself cannot be approached, the oscillation sensor 120 and the reception sensor 124 can be accurately positioned. Measurement is possible even when installation is difficult. Furthermore, the measurement object 106 is a part constituting a girder crane, a bridge, a rail, and the like, and may be made of concrete as well as steel.

  In this way, the present invention can be implemented in earnest only by attaching the oscillation sensor 120 and the reception sensor 124 as shown in FIG. 17 without being placed on the upper surface of the measurement object 104 as in the prior art shown in FIG. It is possible to evaluate the crack 104B. At that time, as shown in FIG. 18, when the object to be measured 104 can be approached, the oscillation sensor 120 and the reception sensor 124 can be directly attached with clay or the like. In addition, when the measurement object 104 is at a high place, as shown in FIG. 19, the oscillation sensor 120 and the reception sensor 124 are attached to the tip of the rod-shaped jig SS as described above, and the measurement object 104 is simply obtained. It is possible to inspect the crack 104B by attaching to the.

  In the present invention, the frequency generator 112 of the above embodiment does not necessarily need to include a frequency determination unit. Even if it is provided, the frequency determining means is configured such that the wavelength λp of the longitudinal wave P forming the guide wave 102 is shorter than the width W of the measurement object 104 (crane girder 106) or the measurement object 104 (crane girder). 106) and a guide member under the condition that the joint width (width) GW of the support member (gusset plate) 108 for supporting the measurement object 104 (crane girder 106) is the same as or longer than GW. A single frequency F of the wave 102 may be selected and determined.

  In the above-described embodiment, the independent frequency generator 112, the phase converter 114, and the analysis device 132 are provided in the nondestructive testing device 100, but the present invention is not limited to this. For example, even if the functions of these components are provided in an integrated apparatus, they belong to the present invention.

  In the above embodiment, the pseudo-random signal is a PRBS signal using an M-sequence, but the present invention is not limited to this. For example, even if the pseudo-random signal is a Gold series or a Barker series, phase conversion can be performed as shown in the above embodiment.

Schematic which shows the nondestructive flaw detector based on 1st Embodiment of this invention. Similarly, a schematic diagram showing how the phase of the waveform output from the frequency generator is phase-converted Schematic diagram showing an example of a guided wave propagation model Similarly, a schematic diagram conceptually showing attenuation when the body wave wavelength does not match the width of the object to be measured Similarly, the figure showing the waveform of the correlation value (sound pressure) when the wavelength (single frequency) is different A conceptual diagram explaining the attenuation of the guide wave when there is also a crack The figure which shows an example of the flow chart of the method of flaw detection similarly Similarly perspective view of crane girder Similarly, a schematic diagram showing the mounting position of the oscillation sensor and the reception sensor Similarly, a schematic diagram showing the mounting position of the oscillation sensor and the reception sensor in detail. The figure which shows the influence with respect to the amplitude of the correlation value (sound pressure) of the joint width of the gusset plate similarly attached to the crane girder The figure which similarly shows the difference in the waveform of the correlation value (sound pressure) by the presence or absence of the crack of the crane girder The figure which shows a mode that the amplitude of a correlation value (sound pressure) changes similarly with the crack length of a crane girder. Similarly, a graph summarizing the relationship between changes in correlation value (sound pressure) and crack length Similarly, the waveform of the correlation value (sound pressure) in the verification B of FIG. The conceptual diagram which shows the simple monitoring using the jig which concerns on 2nd Embodiment of this invention. The figure which shows the big concept about the measurement of this invention The figure which shows the concrete concept about the measurement of this invention The figure which shows another concrete concept about the measurement of this invention Schematic diagram showing that the present invention is applied to a bridge Schematic diagram showing the measurement method of a conventional girder crane

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Nondestructive flaw detector 102, 102A, 102B ... Guide wave 103, 103A, 103B ... Body wave
104 ... Measurement object 104A, 106A ... Measured section 104B, 106B ... Crack 105, 107 ... Post 106, CG1 to CG4 ... Crane girder 108 ... Gusset plate (support member)
DESCRIPTION OF SYMBOLS 112 ... Frequency generator 114 ... Phase converter 116 ... DA converter 118 ... Oscillation amplifier 120 ... Oscillation sensor 122 ... Mounting member 124 ... Reception sensor 126 ... Reception filter 128 ... AD converter 130 ... Data recorder 132 ... Analysis apparatus L ... Length of measurement object W ... Width of measurement object T ... Thickness of measurement object CL ... Length of crack GW ... Bonding width (width) of gusset plate

Claims (9)

Non-destructive flaw detection in which a receiving wave receives a guide wave that is synthesized near the surface of a measurement object and is received by a receiving sensor. In the method
Attaching the oscillation sensor and the reception sensor to the thickness portion of the measurement object across the section to be measured in the length direction of the measurement object,
The frequency of the single frequency signal of the guide wave is determined and output so that the wavelength of the longitudinal wave is shorter than the width of the measurement object,
The output single frequency signal is subjected to phase conversion to generate a pseudo-random signal, and a transmission wave composed of the longitudinal wave and the transverse wave is transmitted from the oscillation sensor,
A guide wave that is a composite wave of the longitudinal wave and the transverse wave that has propagated through the measured section from the oscillation sensor is received as a reception wave by a reception sensor,
A nondestructive flaw detection method characterized by evaluating a crack in the section to be measured by taking a correlation between the pseudo-random signal and a signal according to the received wave.   For the correlation value between the pseudo-random signal and the signal according to the received wave, the relationship between the correlation value obtained in advance and the crack length is used to determine the crack length in the measured section. The nondestructive flaw detection method according to claim 1.   When the oscillation sensor and the reception sensor are attached to the measurement object via an attachment member, the frequency and the frequency of the transmission wave are matched by changing at least one of the material and thickness of the attachment member. The nondestructive flaw detection method according to claim 1, wherein the frequency characteristic of the reception sensor is changed so as to do so.   The non-destructive flaw detection method according to claim 1, wherein the measurement object is a part of a girder crane, a bridge, or a rail, and is made of steel or concrete. An oscillation sensor that transmits a longitudinal wave and a transverse wave as a transmitted wave, a reception sensor that receives a guided wave that is synthesized from the longitudinal wave and the transverse wave and is observed near the surface of the measurement object, and the received wave In the non-destructive flaw detection apparatus having an analysis apparatus for analyzing the crack of the measurement object based on
The oscillation sensor and the reception sensor are attached to the thickness portion of the measurement object across the section to be measured in the length direction of the measurement object, and the wavelength of the longitudinal wave is the width of the measurement object. A frequency generator capable of determining and outputting the frequency of the single frequency signal so as to be shorter than
A phase converter that converts the single frequency signal output from the frequency generator into a pseudo-random signal by phase conversion;
Means for evaluating a crack in the measured section by correlating the pseudo-random signal and a signal according to the received wave;
A nondestructive flaw detection device comprising:   The frequency generator further includes the single frequency so that the wavelength of the longitudinal wave is the same as or longer than a width of a support member that supports the measurement object integrally with the measurement object. The nondestructive flaw detection apparatus according to claim 5, further comprising frequency determining means for determining the frequency.   The analysis apparatus uses the relationship between the correlation value obtained in advance and the crack length for the correlation value between the pseudo-random signal and the signal according to the received wave, to determine the length of the crack in the measured section. The nondestructive flaw detection apparatus according to claim 5, further comprising a calculation unit that calculates   By attaching the oscillation sensor and the reception sensor to the measurement object, and changing at least one of the material and thickness interposed between the measurement object and the oscillation sensor or the reception sensor, the transmission wave The nondestructive flaw detection apparatus according to claim 5, further comprising an attachment member capable of changing a frequency characteristic of the reception sensor so as to match the frequency of the reception sensor.   9. The nondestructive flaw detection apparatus according to claim 8, wherein the attachment member is an adhesive, clay, a highly viscous gel, or a magnet.

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