JP2008076387A - Ultrasonic stress measuring method and instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To separate only surface texture acoustic anisotropy from a material mixed with the surface texture acoustic anisotropy and stress anisotropy, and to precisely measure a residual stress. <P>SOLUTION: A probe control means 13 slides a transverse wave ultrasonic probe 3 to the same position where a longitudinal wave ultrasonic probe 1 is located, after the longitudinal wave ultrasonic probe 1 carries out transmission/reception. The transverse wave ultrasonic probe 3 is rotated by every prescribed angle, and is rotated by 180° while carrying out transmission/reception in every rotation position. A measured data analytical means 16 computes a constant of the surface texture acoustic anisotropy in a testing body M, based on echo data when both the probes carry out the respective transmissions and receptions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic stress measurement method and apparatus used for techniques such as material deterioration diagnosis.

  As a preventive maintenance technology for nuclear power plants, the role of material degradation diagnostic equipment has become important. This is because there is a growing need to improve the stress by measuring the residual stress, which is one of these causes, as a measure to prevent fatigue cracks and stress corrosion cracks in furnace structures and piping. .

  The simplest residual stress measuring means is a strain gauge. However, a strain gauge needs to be cut out as a test piece from a structure to be measured, and is difficult to use for on-site residual stress measurement.

  For this reason, it is conceivable to use an X-ray stress measurement apparatus using an X-ray diffraction technique as a residual stress measurement means that does not require cutting out a test piece. This X-ray stress measurement apparatus calculates a residual stress value by using Bragg diffraction on the surface of an object to be inspected. However, since the X-ray stress measurement apparatus uses X-rays, the background noise increases in a radiation environment such as a nuclear power plant, and a signal sufficient for accurate residual stress measurement cannot be obtained. There is a drawback.

  On the other hand, since the ultrasonic stress measuring apparatus can measure the stress only by applying the ultrasonic sensor to the surface of the object to be inspected, it is not necessary to cut out the sample to be inspected from the structure. Even in a radiation environment such as a nuclear power plant, ultrasonic signals are used, so background noise is small and stress measurement is easy.

  For these reasons, many ultrasonic stress measuring devices have been proposed. Here, as the residual stress to be measured in the stress measurement target material, the residual stress on the material surface is more important than the residual stress in the material. This is because one of the causes of stress corrosion cracking is the tensile stress on the material surface.

  Regarding the residual stress measurement on the material surface, Non-Patent Document 1 discloses an acoustoelastic law using a surface acoustic wave. This is as follows.

That is, when the rolling direction of the steel material is the X axis and the direction orthogonal to the rolling direction is the Y axis, the sound velocity V _R (θ) and the stress of the surface acoustic wave propagating in the direction that forms an angle θ (degrees) with the X axis. Is described as follows.

However, in the method according to Non-Patent Document 1, since the constant α _R (0) of the surface tissue acoustic anisotropy is unknown, the residual stress value can be measured even if the rate of change of the surface acoustic wave sound velocity relative to the stress value can be measured. (Σ) itself cannot be measured. Therefore, when the residual stress is to be measured, it is essential to obtain the surface texture acoustic anisotropy constant.

Non-Patent Document 2 (JIS Z 3060: 2002) and a gazette according to Patent Document 1 based thereon describe the determination of a flaw detection angle range in consideration of acoustic anisotropy. That is, the ratio (V / V _STB ) between the sound speed (V) of the test piece and the sound speed (V _STB ) of the JIS standard standard test piece is measured and defined as the STB sound speed ratio. The range of the refraction angle used for flaw detection is determined according to the plate thickness of the test piece and the STB sound velocity ratio.

  However, the non-patent document 2 and the patent document 1 stipulate that the longitudinal wave and the transverse wave are propagated inside the specimen, and the elastic surface necessary for calculating the residual stress value of the material surface. The surface texture acoustic anisotropy of waves is not specified.

  On the other hand, in the field of material manufacturing methods, methods for reducing acoustic anisotropy have been proposed. This is because when oblique ultrasonic flaw detection is performed, the sound velocity of the material changes due to acoustic anisotropy, and a predetermined refraction angle cannot be obtained, so that the defect positioning accuracy is lowered.

  Patent Documents 2 to 6 include recent proposals for a method for producing a material for reducing such acoustic anisotropy. The methods for measuring acoustic anisotropy shown in these patent documents are generally as follows.

That is, the main rolling direction of the rolled steel material is the L direction, and the direction perpendicular to the main rolling direction is the C direction. The transverse wave that propagates in the plate thickness direction has two transverse waves depending on the vibration direction. The sound velocity of the transverse wave that vibrates in the L direction is V _L (m / sec), and the sound velocity of the transverse wave that vibrates in the C direction is V V. _C (m / sec).

The acoustic anisotropy constant is defined as V _L / V _{C. When} this constant is 1.02 or less, the acoustic anisotropy is small, while when it exceeds 1.02, the acoustic anisotropy is determined to be large. is doing. However, the acoustic anisotropy constant defined in this method is a transverse wave propagating in the material, and is not related to the surface texture acoustic anisotropy necessary for the measurement of the surface stress.

  In Patent Documents 7 to 9, as a method for measuring acoustic anisotropy, the characteristics of the material before use are measured in advance, and the secular change of the material is estimated by measuring the characteristics of the material after use. A method is disclosed.

That is, in the method according to Patent Document 7, to send and receive shear waves in materials using electromagnetic ultrasonic probe, sound velocity V _L of the two shear wave vibration directions are _orthogonal, the V _C is measured, these The acoustic anisotropy is calculated from the sound speed ratio. The change in the sound speed ratio is evaluated as the secular change of the material.

  The method according to Patent Document 8 measures the principal stress difference using SH surface waves. The deterioration of the material is evaluated by observing the secular change of the main stress difference.

  The method according to Patent Document 9 simply monitors changes in the phase difference and sound speed of the received ultrasonic signal, and evaluates secular change from the amount of change.

  As described above, the methods according to Patent Documents 7 to 9 collect material data before use in advance, collect data again after using for a certain period, and compare both data, thereby deteriorating the material. It is a method to evaluate. In such a method, it is a precondition that the data of the material before use exists, and when such data does not exist, it is not applicable.

  Further, the methods according to Patent Document 7 and Patent Document 9 utilize the sound velocity of the transverse wave propagating through the inside of the test body, and the tissue acoustics of the surface acoustic wave necessary for calculating the residual stress value on the material surface. There is no description about anisotropy. On the other hand, in the method according to Patent Document 8, since the SH surface wave is used, the principal stress difference can be measured without being affected by the texture anisotropy of the material. It is the same that there is no description about sex.

Non-Patent Document 3 discloses a technique for measuring surface texture acoustic anisotropy by applying a surface acoustic wave to a test piece having a small residual stress on the surface. However, this technique is based on the premise that there is no residual stress when evaluating the surface tissue acoustic anisotropy. In other words, when both surface texture acoustic anisotropy and stress anisotropy are mixed, there is no disclosure of a technique for obtaining only the surface texture acoustic anisotropy.
Supervised by Kozo Kawada, "Latest Stress / Strain Measurement Evaluation Technology", pp.316-317, published by General Technology Center Co., Ltd. JIS Z 3060: 2002 Kenichi Okada, “Acoustoelastic Effects of Surface Waves”, Proceedings of the 7th Symposium on Basics and Applications of Ultrasonic Electronics, P10, pp.39-40, 1986 JP 2005-36295 JP JP2005-226158 Japanese Patent Laid-Open No. 2004-300567 JP 2004-225090 JP JP2003-313632A JP 2002-180132 A JP 2005-77298 JP JP 2004-294232 JP JP 2001-249118 A

  As described above, when measuring the residual stress of a material using surface acoustic waves, it is necessary to determine the surface texture acoustic anisotropy of the material. However, there is no technique for separating and obtaining only the surface texture acoustic anisotropy. Therefore, conventionally, the residual stress of the material could not be measured with a certain level of accuracy.

  The present invention has been made in view of the above circumstances, and provides a technique for separating only surface texture acoustic anisotropy from a material in which both surface texture acoustic anisotropy and stress anisotropy are mixed, thereby providing a material. It is an object of the present invention to realize an ultrasonic stress measurement method and apparatus capable of measuring the residual stress of a high accuracy.

  As a means for solving the above-described problems, an ultrasonic stress measurement method according to the present invention includes a longitudinal wave ultrasonic probe and a transverse wave ultrasonic probe arranged on the surface of a stress measurement target material, and the two probes. After moving or rotating the probe along the surface of the material, causing one of the probes to perform transmission / reception operations of ultrasonic waves to the measurement target portion of the material, The arrangement of the other probe and the other probe is switched, and the other probe is made to perform the transmission / reception operation of the ultrasonic wave with respect to the same measurement target part. The rotation is performed N times for each rotation angle of ° / N (N: an integer of 2 or more), and transmission / reception operations are performed at each rotation position. Of surface texture acoustic anisotropy from sound velocity data of surface acoustic waves Because, it calculates the residual stress of the stress measurement target material based on the determined constants, and wherein the.

  The ultrasonic stress measurement apparatus according to the present invention includes a longitudinal wave ultrasonic probe and a transverse wave ultrasonic probe that can be arranged on the surface of a stress measurement target material, and the two probes on the surface of the material. And a probe driving mechanism that can be moved or rotated along with the probe, and one probe of the two probes is made to perform the transmission / reception operation of the ultrasonic wave to the measurement target portion of the material. Thereafter, the arrangement of one probe and the other probe is switched by controlling the movement with respect to the probe drive mechanism, and the other probe is operated to transmit and receive ultrasonic waves to the same measurement target part. In particular, the transverse ultrasonic probe is rotated N times for each rotation angle of 180 ° / N (N: an integer of 2 or more), and transmission / reception operations are performed at each rotation position. By the probe control means to be performed and the transmission / reception operations of the two probes. A measurement data analysis means for calculating a constant of surface tissue acoustic anisotropy from sound velocity data of the obtained surface acoustic wave, and calculating a residual stress of the stress measurement target material based on the calculated constant; To do.

  According to the present invention, it is possible to separate only the surface tissue acoustic anisotropy from the material in which both the surface tissue acoustic anisotropy and the stress anisotropy are mixed. Therefore, the residual stress of the material can be measured with high accuracy.

  FIG. 1 is a configuration diagram of an apparatus used for carrying out an ultrasonic stress measurement method according to an embodiment of the present invention. An XY coordinate plane having an X axis and a Y axis perpendicular to the X axis is set on the flat surface of the test body M (material for stress measurement) having a thickness D. In the direction perpendicular to the XY coordinate plane, The Z axis is set.

  One end of the longitudinal wave ultrasonic probe 1 is arranged on the surface of the test body M via the longitudinal wave contact medium 2, and the transverse wave is separated from the longitudinal wave ultrasonic probe 1 by a distance d. One end side of the ultrasonic probe 3 is disposed via a transverse wave contact medium 4.

  The longitudinal wave ultrasonic probe 1 and the transverse wave ultrasonic probe 3 are driven by a probe driving mechanism 5. That is, the other end sides of the longitudinal wave ultrasonic probe 1 and the transverse wave ultrasonic probe 3 are supported by a probe holder 6, and a slide drive unit 7 and a rotation drive unit are attached to the probe holder 6. 8 is attached.

  The slide drive unit 7 slides the probe holder 6 based on a control signal from the slide driver 9, and horizontally moves the longitudinal wave ultrasonic probe 1 and the transverse wave ultrasonic probe 3 along the surface of the specimen M. It can be moved in the direction.

  The rotation drive unit 8 rotates the probe holder 6 based on a control signal from the rotation driver 11, and can rotate the transverse wave ultrasonic probe 3 along the surface of the specimen M by a predetermined angle. .

  Such slide positions of the longitudinal wave ultrasonic probe 1 and the transverse wave ultrasonic probe 3 and the rotational position of the transverse wave ultrasonic probe 3 are respectively determined by a slide position detector 10 and a rotational position detector 12. It is output to the probe control means 13. The probe control means 13 outputs the slide position data and the rotation position data to the measurement data analysis means 16.

  The longitudinal wave ultrasound probe 1 and the transverse wave ultrasound probe 3 are connected to an ultrasound transmission / reception circuit 15 via a probe switch 14. The contact position of the contact 14a of the probe switch 14 is switched by the probe control means 13 with the contact position with the terminals a and b. Then, the ultrasonic transmission / reception circuit 15 performs the transmission operation of the emission pulse Pe to the longitudinal wave ultrasonic probe 1 or the transverse wave ultrasonic probe 3 based on the ultrasonic transmission command from the probe control means 13. At the same time, the receiving operation of the reflected pulse Pr is performed, and the echo data is output to the measurement data analyzing means 16.

  Next, in FIG. 1, the operation of each component until the measurement data analysis means 16 collects various data will be described based on the flowchart of FIG.

  The probe control means 13 outputs a slide command to the slide drive unit 7 via the slide driver 9. Thereby, the slide drive part 7 slides the probe holder 6 so that the longitudinal wave ultrasonic probe 1 is located in the measurement object site | part of the surface of the test body M (step 1). The slide position detector 10 detects the slide position data on the XY coordinate plane at this time and outputs it to the probe control means 13. The probe control means 13 outputs the input slide position data as it is to the measurement data analysis means 16.

Then, the probe control means 13 positions the contact 14a of the probe switch 14 on the terminal a side, and then outputs an ultrasonic transmission / reception command to the ultrasonic transmission / reception circuit 15 (step). 2). As a result, the longitudinal wave ultrasonic probe 1 emits the firing pulse Pe toward the inside of the test body M, and further, the probe switching device transmits the signal of the reflected pulse Pr reflected from the bottom of the test body M. 14 to the ultrasonic transmission / reception circuit 15. The ultrasonic transmission / reception circuit 15 outputs the input reflected pulse Pr signal as echo data to the measurement data analysis means 16. Next, the probe control means 13 is connected to the slide drive unit 7 via the slide driver 9. A slide command is output, and the probe holder 6 is slid horizontally along the surface of the specimen M by a distance d (step 3). That is, the transverse wave ultrasound probe 3 is now positioned at the same measurement target site where the longitudinal wave ultrasound probe 1 emits ultrasound. At this time, the slide position data detected by the slide position detector 10 is output to the measurement data analysis means 16 via the probe control means 13.

  The probe control means 13 further outputs a rotation command to the rotation drive unit 8 via the rotation driver 11. Thereby, the rotation drive unit 8 rotates the probe holder 6 so that the ultrasonic wave traveling direction of the transverse wave ultrasonic probe 3 is the X-axis direction (step 4). At this time, the rotational position data detected by the rotational position detector 12 is output to the measurement data analysis means 16 via the probe control means 13.

  Then, the probe control means 13 switches the contact 14a of the probe switch 14 to the terminal b side, and then outputs an ultrasonic transmission / reception command to the ultrasonic transmission / reception circuit 15 (step 5). ). Thereby, the transverse wave ultrasonic probe 3 emits the emission pulse Pe along the X-axis direction, and further, the signal of the reflected pulse Pr is sent to the ultrasonic wave transmission / reception circuit 15 via the probe switch 14. Output. The ultrasonic transmission / reception circuit 15 outputs the input signal of the reflected pulse Pr as echo data to the measurement data analysis means 16.

  Thus, after the transverse wave ultrasonic probe 3 performs the transmission / reception operation in which the ultrasonic wave traveling direction is the X-axis direction, the probe control means 13 again sends the rotation drive unit via the rotation driver 11. The rotation command is output to 8. As a result, the rotation drive unit 8 rotates the probe holder 6 so that the ultrasonic wave traveling direction of the transverse wave ultrasonic probe 3 is rotated by 180 ° / N from the X-axis direction (step 6). . At this time, the rotational position data detected by the rotational position detector 12 is output to the measurement data analysis means 16 via the probe control means 13. Here, it is assumed that the value of N is an integer of 2 or more. For example, if the transverse ultrasonic probe 3 is rotated by 15 °, N = 12.

  Then, the probe control means 13 outputs an ultrasonic wave transmission / reception command to the ultrasonic wave transmission / reception circuit 15 with the contact 14a of the probe switch 14 maintained on the terminal b side (step). 7). Thereby, the transverse wave ultrasonic probe 3 emits the emission pulse Pe along the direction rotated by 180 ° / N from the X-axis direction, and further, the signal of the reflected pulse Pr is transmitted via the probe switch 14. And output to the ultrasonic transmission / reception circuit 15. The ultrasonic transmission / reception circuit 15 outputs the input signal of the reflected pulse Pr as echo data to the measurement data analysis means 16.

  After the transverse wave ultrasonic probe 3 performs transmission / reception operations at a position where the ultrasonic wave traveling direction is rotated by 180 ° / N from the X-axis direction, the probe control means 13 performs the transverse wave ultrasonic probe. It is determined whether or not the toucher 3 has completed N times of transmission / reception operations (step 8).

  If N transmission / reception operations have not been completed yet, the process returns to step 6 and the probe control means 13 rotates the transverse wave ultrasonic probe 3 by 180 ° / N further than the previous ultrasonic emission position. The probe holder 6 is rotated so that the ultrasonic wave traveling direction of the transverse wave ultrasonic probe 3 is rotated by (180 ° / N) · 2 from the X-axis direction. (Step 6). Thereafter, the probe control means 13 similarly performs an ultrasonic transmission / reception command to the ultrasonic transmission / reception circuit 15 with the contact 14a of the probe switch 14 maintained on the terminal b side. Is output (step 7).

  On the other hand, if N transmission / reception operations have already been completed, the probe control means 13 ends all processing at that time. In the above description, the case where the transverse wave ultrasonic probe 3 performs the transmission / reception operation after the transmission / reception operation of the longitudinal wave ultrasonic probe 1 has been described. However, the transmission / reception of both probes is performed. The order of operations may be reversed.

  Various measurement data such as echo data, rotational position data, slide position data, etc. are analyzed by the control of the probe control means 13 for the longitudinal wave ultrasonic probe 1 and the transverse wave ultrasonic probe 3 as described above. Collected by means 16. Therefore, the analysis processing of the measurement data analysis means 16 for such measurement data will be described next.

  FIG. 3A is a waveform diagram of echo data from the longitudinal wave ultrasonic probe 1 collected by the measurement data analysis means 16. As shown in this figure, the echo data from the longitudinal wave ultrasonic probe 1 is composed of multiple echoes (L1, L2,..., L6,...) Having a fixed time interval, and this time interval is This is determined by the plate thickness D (m) of the test body M.

Here, if the time interval between the L1 echo and the L2 echo is τ _L (sec), this time interval τ _L is the time for reciprocating the plate thickness D (m) of the specimen M. The sound velocity CL (m / sec) of the wave is calculated by the following equation (3).

Here, various methods have been proposed for measuring τ _L. Examples of methods that can be easily realized with relatively good time measurement accuracy include a single-around method and an echo overlap method. Details on these techniques are disclosed in reference (1) (references are given in the last paragraph).

In the sing-around method, the total time interval T (sec) of N ultrasonic pulses (L1, L2,..., LN) is measured, and the time interval between the L1 echo and the L2 echo is expressed as (4 ) Is a method of calculating by the equation. According to this method, by using many multiple echoes, the measurement accuracy of τ _L can be improved accordingly.

The echo overlap method is a method of measuring a time interval using a delayed sweep function such as an oscilloscope. As a specific procedure, L1 echoes are sequentially delayed, and the delay time is changed so as to overlap the L2 echoes. Reads the delay time when L1 echo and L2 echo overlap exactly and tau _L.

Measured data analyzing means 16 determines the longitudinal wave sound velocity C _L by substituting thus determined and the time interval tau _L in (3), and stored. In the present invention, as a method for measuring the time interval τ _L , a general-purpose method other than the above can be adopted as long as the time measurement method has high measurement accuracy.

FIG. 3 (b) is a waveform diagram of echo data from the transverse wave ultrasonic probe 3 collected by the measurement data analysis means 16 (the waveform obtained based on the command in step 5 of FIG. The ultrasonic traveling direction is the X-axis direction). As shown in this figure, the echo data from the transverse ultrasonic probe 3 is obtained by multiple echoes (S (0) ₁ , S (0) ₂ , S (0) ₃ ,...) Having a fixed time interval. It is configured.

Here, if the time interval between S (0) ₁ echo and S (0) ₂ echo is τ _S (0) (sec), this time interval τ _S (0) is the thickness D (m ), The transverse sound velocity V _S (0) (m / sec) in the specimen M is calculated by the following equation (5).

Since the sound speed of the transverse wave is about half that of the longitudinal wave, the time interval τ _S (0) of FIG. 3B is about twice the time interval τ _L of FIG. .

In addition, the method for measuring the time interval τ _S (0) is not limited to a technique such as a sing-around method or an echo overlap method, and it is possible to use a general-purpose measurement method with high accuracy other than these methods. This is the same as in the case of longitudinal waves.

  By the way, the probe holder 6 is rotated stepwise so that the ultrasonic wave traveling direction of the transverse wave ultrasonic probe 3 gradually moves away from the X-axis direction by a rotation angle of 180 ° / N (for example, 15 °). When ultrasonic transmission / reception operations are performed at each rotation angle, the waveform of echo data obtained by such a series of transmission / reception operations is affected by the surface tissue acoustic anisotropy of the specimen M. Become.

Considering such a series of (N−1) transverse wave echo data waveforms obtained by the processing of steps 6 and 7 in FIG. 2, between the multiple echoes obtained by the transmission / reception operation at the I-th rotation position. Is the time interval τ _S (I), and the sound velocity of the transverse ultrasonic waves is V _S (I). The traveling direction of the transverse ultrasonic waves at this time is a direction inclined by (I × 180 / N) (degrees) from the X-axis direction.

Sound velocities V _S (1), V _S (2), V _S (3),..., V _S (I) _,. N-1) can be obtained by the following arithmetic expression similar to the expression (5).

  FIG. 4 summarizes the time interval and the sound velocity of the echo data for the longitudinal wave ultrasonic probe 1 obtained as described above and the echo data for each rotation angle for the transverse wave ultrasonic probe 3. It is explanatory drawing which shows the content of the data table. The measurement data analysis means 16 stores the contents of such a data table in its own storage unit.

  Next, a method for obtaining the surface tissue acoustic anisotropy of the specimen M using the above data table will be described.

  5A and 5B are explanatory diagrams showing the specimen M and the three-dimensional coordinates set thereto, wherein FIG. 5A is an explanatory diagram in which the plane P1 orthogonal to the X axis is indicated by oblique lines, and FIG. 5B is orthogonal to the Y axis. It is explanatory drawing which showed the surface P2 to perform by the oblique line.

In FIG. 5 (a), if the residual stress in the X-axis direction acting on the surface P1 is σ _x (z), no external force is acting on the surface P1, so the following (6) The formula holds.

Here, when σ _X (z) is uniform in the Y-axis direction, equation (6) can be rewritten as equation (7), and therefore equation (8) holds.

  According to the reference (2), the following is known about the longitudinal sound velocity. First, in the case of tensile residual stress, the longitudinal sound velocity that propagates in a direction orthogonal to the residual stress direction increases. Conversely, in the case of compressive residual stress, the longitudinal sound velocity that propagates in the direction orthogonal to the residual stress direction decreases. Accordingly, these residual stresses are expressed by equation (8), and the influence of the residual stresses is offset. Therefore, it can be considered that the longitudinal wave sound velocity propagating through the specimen M is less changed by the residual stress, and the average Can be thought of as the speed of sound.

Further, according to the reference (2), as with the longitudinal wave sound velocity, the following is known for the shear wave sound velocity. That is, when the vibration direction of the transverse wave and the direction of the stress are the same, the transverse wave sound velocity increases in the case of compressive stress, and the transverse wave sound velocity decreases in the case of tensile stress. Accordingly, these residual stresses are expressed by equation (8), and the influence of the residual stresses is offset. Therefore, it can be considered that the transverse wave sound velocity propagating through the specimen M is less changed by the residual stresses. That is, it can be considered that V _S (0) is not affected by the residual stress in the X-axis direction, but only by the surface texture acoustic anisotropy, similarly to the longitudinal sound velocity.

The residual stress in the Y-axis direction can be considered in the same manner as described above. That is, in FIG. 5B, if the residual stress in the Y-axis direction acting on the surface P2 is σ _Y (z), no external force is acting on the surface P2, and therefore the following ( 9) Formula is established.

Here, when σ _Y (z) is uniform in the X-axis direction, equation (9) can be rewritten as equation (10), and therefore equation (11) holds.

Accordingly, as in the case of the X-axis, the sound velocity V _S (I) of the transverse wave that vibrates in the Y-axis direction is not affected by the residual stress in the Y-axis direction, but is affected by only the tissue acoustic anisotropy. It can be thought of as wave speed.

Therefore, the surface texture acoustic anisotropy can be defined if the acoustic velocity of the surface acoustic wave can be calculated by some method using the longitudinal wave velocity and the transverse wave velocity that are not easily affected by the residual stress. It is.

  The measurement data analysis means 16 performs the process in this way, and can calculate the constant of the surface tissue acoustic anisotropy using the equations (12) and (13).

Next, the second method will be described. According to References (3), as shown in the left equation of (19) below, it is possible to represent the ratio between the speed of sound V _R and transverse wave sound velocity V _S of the surface acoustic wave in the Poisson's ratio σ The Poisson's ratio σ is represented by a transverse wave sound velocity V _S and a longitudinal wave sound velocity C _L as in the right equation of the following equation (19).

Next, the fourth method will be described. The surface acoustic wave sound velocity around the measurement target site of the surface tissue acoustic anisotropy of the test body M can be measured in advance. The surface acoustic wave sound velocity acquired by this measurement is defined as V _R ′ (I). Therefore, the transverse wave ultrasonic probe 3 is rotated N times at a rotation angle of 180 ° / N from the X axis, and N pieces of data V _R ′ (I) at the rotation position after each rotation are expressed by (25 ), The sound velocity V _R ⁰ of the surface acoustic wave in the isotropic body can be obtained. By substituting this calculated value into the equations (12) and (13), a constant of surface texture acoustic anisotropy can be calculated.

Next, the fifth method will be described. As described in the fourth method, the surface acoustic wave sound velocity around the measurement target site of the surface tissue acoustic anisotropy of the specimen M can be measured in advance. Therefore, it is possible to actually measure the surface acoustic wave sound velocity propagating in the X-axis direction with respect to V _R '(0) and the surface acoustic wave sound velocity propagating in the Y-axis direction with respect to V _R ' (90). The sound velocity V _R ⁰ of the surface acoustic wave can be approximately obtained by calculating the average value of the two actually measured data as shown in the following equation (26). By substituting this calculated value into the equations (12) and (13), a constant of surface texture acoustic anisotropy can be calculated.

  As described above, according to the configuration of FIG. 1, the measurement data analysis unit 16 performs echoes under the control of the probe control unit 13 for the longitudinal wave ultrasonic probe 1 and the transverse wave ultrasonic probe 3. Various measurement data such as data, rotation position data, and slide position data are collected, and by this collected measurement data analysis processing, it is possible to obtain a constant of surface tissue acoustic anisotropy that could not be obtained conventionally. . Therefore, it is possible to accurately calculate the residual stress of the specimen M, that is, the stress measurement target material, based on the obtained surface texture acoustic anisotropy constant.

Reference 1

  Fukuoka Hidekazu, "Basics and Applications of Acoustoelasticity" Ohmsha, April 1993

Reference 2

  Supervised by Kozo Kawada "Latest Stress / Strain Measurement Evaluation Technology", pp.308-310, published by General Technology Center Co., Ltd.

Reference 3

  B. A. Auld: Acoustic Fields and Waves in Solid, Volume II, pp. 88-94, Krieger Publishing Company, Florida

The block diagram of the apparatus used in order to implement the ultrasonic type stress measuring method which concerns on embodiment of this invention. The flowchart for demonstrating the operation | movement of FIG. It is a wave form diagram of the echo data collected by the measurement data analysis means 16 in FIG. 1, (a) shows multiple echoes of longitudinal waves, (b) shows multiple echoes of transverse waves. Explanatory drawing which shows the content of the data table which put together the calculation data by the measurement data analysis means 16 in FIG. It is explanatory drawing which shows the test body M in FIG. 1, and the three-dimensional coordinate set to this, (a) is explanatory drawing which showed the surface P1 orthogonal to X-axis by the oblique line, (b) is orthogonal to Y-axis. Explanatory drawing which showed the surface P2 by the oblique line.

Explanation of symbols

M: Specimen (material for stress measurement)
1: Longitudinal wave ultrasonic probe 2: Longitudinal wave contact medium 3: Transverse wave ultrasonic probe 4: Transverse wave contact medium 5: Probe drive mechanism 6: Probe holder 7: Slide drive unit 8: Rotation drive unit 9: Slide driver 10: Slide position detector 11: Rotation driver 12: Rotation position detector 13: Probe control means 14: Probe switch 14a: Contact 15: Ultrasonic transmission / reception circuit 16: Measurement data analysis means Pe: firing pulse Pr: reflection pulse

Claims (8)

Place a longitudinal wave ultrasonic probe and a transverse wave ultrasonic probe on the surface of the stress measurement target material,
Moving or rotating the probes along the surface of the material;
After causing one probe of the two probes to perform transmission / reception of ultrasonic waves with respect to the measurement target portion of the material, the arrangement of one probe and the other probe is switched. The other probe is made to perform the transmission / reception operation of the ultrasonic wave to the same measurement target part, and the transverse wave ultrasonic probe is rotated at every rotation angle of 180 ° / N (N: integer of 2 or more). N times of rotation, so that the transmission / reception operation is performed at each rotation position,
A surface tissue acoustic anisotropy constant is obtained from the acoustic velocity data of the surface acoustic wave obtained by the transmission / reception operations of the two probes, and the residual stress of the stress measurement target material is calculated based on the obtained constant.
An ultrasonic stress measurement method characterized by the above. A longitudinal wave ultrasonic probe and a transverse wave ultrasonic probe that can be arranged on the surface of the stress measurement target material; and
A probe driving mechanism capable of moving or rotating the two probes along the surface of the material;
One probe of the two probes is made to transmit / receive ultrasonic waves to / from the measurement target portion of the material, and then one probe is controlled by controlling the movement of the probe driving mechanism. The arrangement of the probe and the other probe is switched, and the other probe is made to perform the transmission / reception operation of the ultrasonic wave with respect to the same measurement target part. For the transverse wave ultrasonic probe, 180 ° / N A probe control means for performing N rotations for each rotation angle (N: an integer of 2 or more) and performing transmission / reception operations at each rotation position;
Measurement data for calculating the surface tissue acoustic anisotropy constant from the acoustic velocity data of the surface acoustic wave obtained by the transmitting and receiving operations of the two probes and calculating the residual stress of the stress measurement target material based on the obtained constant Analysis means;
An ultrasonic stress measuring device comprising: The sound velocity data of the surface acoustic wave is
Velocity data of surface acoustic waves propagating in the X-axis direction without being affected by surface stress anisotropy,
Sound velocity data of surface acoustic waves propagating in the Y-axis direction perpendicular to the X-axis direction without being affected by the surface stress anisotropy;
Sound velocity data of surface acoustic waves in an isotropic body that is not affected by any of surface stress anisotropy and surface tissue acoustic anisotropy,
The ultrasonic stress measuring apparatus according to claim 2. Sound velocity data of surface acoustic waves propagating in the X-axis direction and the Y-axis direction, respectively,
It is obtained as a solution of a predetermined 6-dimensional surface acoustic wave sound velocity equation expressed by using the longitudinal wave sound velocity and the transverse wave sound velocity in the X-axis direction and the Y-axis direction,
Sound velocity data of surface acoustic waves in an isotropic body that is not affected by any of the surface stress anisotropy and surface tissue acoustic anisotropy is
As a solution of a predetermined 6-dimensional surface acoustic wave sound velocity equation expressed by using the longitudinal wave sound velocity and the transverse wave sound velocity in the ultrasonic traveling direction at the rotational position after each N rotations of the transverse wave ultrasonic probe. It is obtained by calculating the average value of the sound velocity data of the obtained N surface acoustic waves.
The ultrasonic stress measuring device according to claim 3. Sound velocity data of surface acoustic waves propagating in the X-axis direction and the Y-axis direction, respectively,
The ratio between the sound velocity of the surface acoustic wave in the X-axis direction and the Y-axis direction and the transverse wave sound velocity in the X-axis direction and the Y-axis direction is obtained from a predetermined equation expressed by Poisson's ratio.
Sound velocity data of surface acoustic waves in an isotropic body that is not affected by any of the surface stress anisotropy and surface tissue acoustic anisotropy is
The ratio of the sound velocity of the surface acoustic wave in the ultrasonic traveling direction to the transverse wave velocity in the same direction at the rotation position after each of N rotations of the transverse wave ultrasonic probe is expressed as a Poisson ratio. The sound velocity data of N surface acoustic waves obtained from the equation is obtained by calculating the average value.
The ultrasonic stress measuring device according to claim 3. Sound velocity data of surface acoustic waves in an isotropic body that is not affected by any of the surface stress anisotropy and surface tissue acoustic anisotropy is
Sound velocity data of a surface acoustic wave propagating in the X-axis direction without being affected by the surface stress anisotropy, and a Y-axis direction perpendicular to the X-axis direction without being affected by the surface stress anisotropy It is obtained by calculating the average value of two data of sound velocity data of the surface acoustic wave that propagates.
The ultrasonic stress measuring device according to claim 3. Sound velocity data of surface acoustic waves in an isotropic body that is not affected by any of the surface stress anisotropy and surface tissue acoustic anisotropy is
The acoustic velocity data of N surface acoustic waves in the ultrasonic traveling direction at the rotational position after each rotation of the transverse wave ultrasonic probe N times is obtained in advance by actual measurement, and these obtained N pieces of data are obtained. It is obtained by calculating the average value.
The ultrasonic stress measuring device according to claim 3. Sound velocity data of surface acoustic waves in an isotropic body that is not affected by any of the surface stress anisotropy and surface tissue acoustic anisotropy is
Sound velocity data of a surface acoustic wave propagating in the X-axis direction without being affected by the surface stress anisotropy, and a Y-axis direction perpendicular to the X-axis direction without being affected by the surface stress anisotropy Two data of sound velocity data of the surface acoustic wave propagating are obtained in advance by actual measurement, and the obtained two data are obtained by calculating an average value.
The ultrasonic stress measuring device according to claim 3.

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