Stress analysis system

Abstract

To identify the stress state of a test piece in a short time.SOLUTION: A measurement sensor 30 receives a surface SH wave having propagated through a test piece in a measurement direction D1 along an extension direction Ψ of the test piece and in a measurement direction D2 orthogonal to the measurement direction D1. An auxiliary sensor 40 receives a surface SH wave having propagated through the test piece in a reference direction Dref crossing a main stress direction Ω of the test piece at a prescribed angle. An information processing device corrects a first speed index pertaining to the speed at which the surface SH wave propagates in the measurement direction D1 in accordance with the difference between a first reference index pertaining to the speed at which the surface SH wave propagates in the reference direction Dref and a reference value, and corrects a second speed index pertaining to the speed at which the surface SH wave propagates in the measurement direction D2 in accordance with the difference between a second reference index pertaining to the speed at which the surface SH wave propagates in the reference direction Dref and a reference value, then identifies the main stress difference of the test piece in accordance with the first speed index after correction and the second speed index after correction.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to techniques for determining a stress state in an object to be analyzed (hereinafter referred to as a "test piece"). [Background technology]

[0002] Techniques have been proposed for identifying the stress state of a test object by using surface SH (Shear Horizontal) waves that vibrate parallel to the object surface. For example, Patent Document 1 discloses an acoustoelastic stress measuring sensor that includes a transmitter that radiates surface SH waves to the surface of the test object and a receiver that receives the surface SH waves that have propagated through the test object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-37436 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to identify the principal stress direction in a test specimen under the conventional technology, it is necessary to measure the propagation velocity for each of a plurality of cases in which the propagation direction of the surface SH wave in the test specimen is different. Therefore, it takes a long time to identify the stress state of the test specimen. In consideration of the above circumstances, one aspect of the present disclosure aims to easily identify the stress state of a test specimen. [Means for solving the problem]

[0005] In order to solve the above problems, a stress analysis system according to one embodiment of the present disclosure includes a memory unit that stores a reference value related to the speed of surface SH waves propagating in a reference direction that intersects with a principal stress direction of a test body at a predetermined angle, a measurement sensor that receives surface SH waves propagating through the test body in each of a first direction along the rolling direction of the test body and a second direction perpendicular to the first direction, an auxiliary sensor that receives surface SH waves propagating through the test body in the reference direction, and an information processing unit including a calculation unit, a correction unit, and an analysis unit, wherein the calculation unit calculates a first speed index related to the speed at which surface SH waves propagate in the first direction based on the reception result of the measurement sensor, and calculates a first reference index related to the speed at which surface SH waves propagate in the reference direction based on the reception result of the measurement sensor. the correction unit executes a first correction process to correct the first velocity index according to a difference between the first reference index and the reference value and a second correction process to correct the second velocity index according to a difference between the second reference index and the reference value, and the analysis unit executes an analysis process to identify a principal stress difference of the test specimen according to the first velocity index after correction by the first correction process and the second velocity index after correction by the second correction process. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram illustrating a configuration of a stress analysis system according to one embodiment of the present disclosure. [Diagram 2] FIG. 4 is a plan view of the measurement sensor and the auxiliary sensor. [Diagram 3] FIG. 2 is a block diagram illustrating a functional configuration of a stress analysis system. [Figure 4] 4 is a flowchart of a measurement process and a correction process. [Diagram 5] 1 is a graph showing the relationship between the propagation direction of a surface SH wave and the propagation velocity of the surface SH wave. [Figure 6]13 is a flowchart of a stress analysis process. [Figure 7] 13 is a flowchart of a stress analysis process. [Figure 8] FIG. 13 is a plan view of a measurement sensor in a modified example. [Figure 9] FIG. 13 is a plan view of a measurement sensor in a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The embodiments for carrying out the present disclosure will be described with reference to the drawings. Note that in each drawing, the dimensions and scale of each element may differ from those of the actual product. The embodiment described below is an exemplary embodiment assumed when carrying out the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0008] A: Embodiment 1 is a block diagram illustrating the configuration of a stress analysis system 100 according to one embodiment of the present disclosure. The stress analysis system 100 is a measuring device for non-destructively identifying the state of stress acting on a test specimen 20 (hereinafter referred to as the "stress state"). The test specimen 20 is a metal plate-like member used, for example, in the deck of a ship.

[0009] The stress analysis system 100 of this embodiment identifies the principal stress difference Δ as the stress state of the test piece 20. The principal stress difference Δ is the difference between the maximum principal stress σ1 and the minimum principal stress σ2 (Δ=σ1−σ2).

[0010] 1, the stress analysis system 100 includes a measurement sensor 30, an auxiliary sensor 40, and a measurement device 50. Each of the measurement sensor 30 and the auxiliary sensor 40 is an ultrasonic sensor (probe) that transmits surface SH waves to the test piece 20 and receives the surface SH waves that have propagated through the test piece 20. The surface SH waves are ultrasonic waves that vibrate in a direction parallel to the surface 21 of the test piece 20, and propagate as elastic waves in the vicinity of the surface 21 of the test piece 20, as shown by the dashed arrow in FIG.

[0011] 2 is a plan view of the measurement sensor 30 and the auxiliary sensor 40. In this embodiment, the rolling direction Ψ and the principal stress direction Ω of the test piece 20 are known. The rolling direction Ψ is a direction parallel to the surface 21 of the test piece 20, and means a direction in which a metal material advances in a process of manufacturing the test piece 20 by rolling. The rolling direction Ψ can also be expressed as a direction perpendicular to the rotation axis of a pair of rollers used to roll the metal material. For example, the rolling direction Ψ of the test piece 20 is identified from the structure of a structure in which the test piece 20 is used.

[0012] An in-plane principal stress axis is determined inside the test piece 20. The principal stress direction Ω is the angle that the principal stress axis in the test piece 20 makes with respect to the rolling direction Ψ. Any known technique can be used to determine the principal stress direction Ω. Specifically, the principal stress direction Ω is determined by using various sensors such as strain gauges or piezoelectric elements.

[0013] 1 and 2, the measurement sensor 30 includes four transducer pairs 31-1 to 31-4, a support member 32, and a contact medium 33. In the following description, when there is no need to distinguish between the four transducer pairs 31-1 to 31-4, they will be collectively referred to as "transducer pair 31-n" (n=1 to 4). The same applies to the other symbols.

[0014] Each transducer pair 31-n is composed of a pair of a transceiver 35 and a transceiver 36. The transceiver 35 and the transceiver 36 are installed at a predetermined distance from each other. Each of the transceiver 35 and the transceiver 36 is a transducer that transmits and receives surface SH waves. Specifically, one of the transceiver 35 and the transceiver 36 transmits surface SH waves to the test piece 20. The surface SH waves propagate near the surface 21 of the test piece 20. The other of the transceiver 35 and the transceiver 36 receives the surface SH waves that have propagated through the test piece 20.

[0015] The support member 32 is a wedge member that supports the transceiver 35 and the transceiver 36 of each transducer pair 31-n. The transceiver 35 and the transceiver 36 of each transducer pair 31-n are supported by the support member 32 in an attitude that forms a predetermined angle with respect to the surface 21 of the test body 20. The coupling medium 33 is a medium that is interposed between the test body 20 and the support member 32. By filling the gap between the support member 32 and the test body 20 with the coupling medium 33, surface SH waves are efficiently propagated between each transducer pair 31-n and the test body 20.

[0016] FIG. 2 illustrates four different measurement directions D1 to D4 in a plane parallel to the surface 21 of the test piece 20. The transceiver 35 and the transceiver 36 of the transducer pair 31-1 are arranged at an interval from each other along the measurement direction D1. The measurement direction D1 is a direction along the rolling direction Ψ of the test piece 20. Specifically, the measurement direction D1 is a direction parallel to the rolling direction Ψ. The transceiver 35 and the transceiver 36 of the transducer pair 31-2 are arranged at an interval from each other along the measurement direction D2. The measurement direction D2 is a direction perpendicular to the measurement direction D1. The measurement direction D1 is an example of a "first direction", and the measurement direction D2 is an example of a "second direction".

[0017] The transceiver 35 and the transceiver 36 of the transducer pair 31-3 are arranged at a distance from each other along the measurement direction D3. The measurement direction D3 is a direction inclined at a predetermined angle with respect to the measurement direction D1. Specifically, the measurement direction D3 is a direction that forms an angle of 45° with respect to the measurement direction D1 (rolling direction Ψ). The transceiver 35 and the transceiver 36 of the transducer pair 31-4 are arranged at a distance from each other along the measurement direction D4. The measurement direction D4 is a direction perpendicular to the measurement direction D3. In other words, the measurement direction D4 is a direction that forms an angle of 135° with respect to the measurement direction D1 (rolling direction Ψ). The measurement direction D3 is an example of a "third direction", and the measurement direction D4 is an example of a "fourth direction".

[0018] As shown in the above example, the measurement sensor 30 receives surface SH waves propagating through the test piece 20 in each measurement direction Dn. The measurement sensor 30 is installed on the surface 21 of the test piece 20 so that each transducer pair 31-n is aligned with the measurement direction Dn with respect to the rolling direction Ψ of the test piece 20. That is, the four transducer pairs 31-1 to 31-4 are arranged to form angles of 0° (D1), 45° (D3), 90° (D2), and 135° (D4) with respect to the rolling direction Ψ. Therefore, as shown in FIG. 2, the transceivers 35 and 36 are arranged at intervals of 45° in the circumferential direction centered on a predetermined point.

[0019] The auxiliary sensor 40 is a sensor for assisting measurement using the measurement sensor 30. As illustrated in Fig. 1 and Fig. 2, the auxiliary sensor 40 includes a pair of transducers 41, a support member 42, and a contact medium 43.

[0020] The transducer pair 41 is composed of a pair of a transceiver 45 and a transceiver 46. The transceiver 45 and the transceiver 46 are installed at a predetermined distance from each other. Each of the transceiver 45 and the transceiver 46 is a transducer that transmits and receives surface SH waves. Specifically, one of the transceiver 45 and the transceiver 46 transmits surface SH waves to the test piece 20. The surface SH waves propagate near the surface 21 of the test piece 20. The other of the transceiver 45 and the transceiver 46 receives the surface SH waves that have propagated through the test piece 20.

[0021] The support member 42 is a wedge member that supports the transceiver 45 and the transceiver 46 of each transducer pair 41. The transceiver 45 and the transceiver 46 of each transducer pair 41 are supported by the support member 42 in an attitude that forms a predetermined angle with respect to the surface 21 of the test body 20. The coupling medium 43 is a medium that is interposed between the test body 20 and the support member 42. By filling the gap between the support member 42 and the test body 20 with the coupling medium 43, surface SH waves are efficiently propagated between each transducer pair 41 and the test body 20.

[0022] As illustrated in FIG. 2, the transceiver 45 and the transceiver 46 of the transducer pair 41 are arranged at a distance from each other along the reference direction Dref. The reference direction Dref is a direction intersecting with the known principal stress direction Ω of the test object 20 at a predetermined angle. Specifically, the reference direction Dref is a direction inclined at an angle of 45° with respect to the principal stress direction Ω. As described above, the auxiliary sensor 40 is installed on the surface 21 of the test object 20 so that the transducer pair 41 is aligned with the reference direction Dref. That is, the auxiliary sensor 40 receives the surface SH wave propagating through the test object 20 in the reference direction Dref.

[0023] The auxiliary sensor 40 is installed in the vicinity of the measurement sensor 30. Specifically, the measurement sensor 30 and the auxiliary sensor 40 are installed within a range close enough on the surface 21 of the test piece 20 that their temperatures are substantially the same. That is, the temperature of the test piece 20 is substantially the same between the position on the surface 21 of the test piece 20 where the measurement sensor 30 is installed and the position on the surface 21 of the test piece 20 where the auxiliary sensor 40 is installed. Specifically, the temperature of the test piece 20 at the position of the measurement sensor 30 and the temperature of the test piece 20 at the position of the auxiliary sensor 40 are close to or coincide with each other to such an extent that the measurement error of the stress state by the stress analysis system 100 is a numerical value within a predetermined tolerance range.

[0024] The measuring device 50 in Fig. 1 is a computer system that identifies the stress state of the test object 20 according to the results of the measurement sensor 30 and the auxiliary sensor 40 receiving the surface SH waves propagating through the test object 20. The measuring device 50 includes a driving device 51, a detecting device 52, a switching device 53, a switching device 54, and an information processing device 60. One or both of the driving device 51 and the detecting device 52 may be mounted on each of the measurement sensor 30 and the auxiliary sensor 40, or may be mounted on the information processing device 60. The switching device 53 may be mounted on the information processing device 60 or the measurement sensor 30. Similarly, the switching device 54 may be mounted on the information processing device 60 or the auxiliary sensor 40.

[0025] The driver 51 drives each measurement sensor 30 and the auxiliary sensor 40. Specifically, the driver 51 selectively drives each of the four transducer pairs 31-1 to 31-4 of the measurement sensor 30 in response to an instruction from the information processing device 60. For example, the driver 51 transmits a drive signal to the measurement sensor 30 for driving the transceiver 35 or the transceiver 36. Similarly, the driver 51 transmits a drive signal to the auxiliary sensor 40 for driving the transceiver 45 or the transceiver 46.

[0026] The detection device 52 generates a detection signal Y representing the waveform of the surface SH wave received by the transceiver 35 or the transceiver 36. That is, the detection signal Y is a signal representing the result of the measurement sensor 30 receiving the surface SH wave that has propagated through the test piece 20. The detection device 52 also generates a detection signal Z representing the waveform of the surface SH wave received by each transceiver 45 or each transceiver 46. That is, the detection signal Z is a signal representing the result of the auxiliary sensor 40 receiving the surface SH wave that has propagated through the test piece 20.

[0027] The switching device 53 and the switching device 54 are mechanisms for switching the connection destination of the driving device 51 and the detection device 52, respectively. The switching device 53 includes a switch 531 and a switch 532. The switch 531 selectively connects either the transceiver 35 or the transceiver 36 of each transducer pair 31-n to the driving device 51. The switch 532 selectively connects either the transceiver 35 or the transceiver 36 of the transducer pair 31-n to the detection device 52. As described above, the transceiver 35 and the transceiver 36 can both transmit and receive surface SH waves. However, in the following description, for convenience, it is assumed that the transceiver 35 transmits surface SH waves to the test object 20 and the transceiver 36 receives the surface SH waves propagated through the test object 20.

[0028] The switching device 54 includes a switch 541 and a switch 542. The switch 541 selectively connects either the transceiver 45 or the transceiver 46 of the transducer pair 41 of the auxiliary sensor 40 to the driving device 51. The switch 542 selectively connects either the transceiver 45 or the transceiver 46 of the transducer pair 41 to the detection device 52. As described above, the transceiver 45 and the transceiver 46 are capable of both transmitting and receiving surface SH waves. However, in the following description, for convenience, it is assumed that the transceiver 45 transmits surface SH waves to the test piece 20 and the transceiver 46 receives the surface SH waves propagating through the test piece 20.

[0029] The information processing device 60 is a computer system that identifies the stress state of the test piece 20 by processing the detection signal Y and the detection signal Z. The information processing device 60 is realized by an information device such as a personal computer or a tablet terminal. Specifically, the information processing device 60 includes a control device 61, a storage device 62, and a display device 63. The information processing device 60 may be realized by a single device, or may be realized by multiple devices configured separately from each other. The information processing device 60 is an example of an "information processing unit."

[0030] The control device 61 is composed of one or more processors that control each element of the information processing device 60. Specifically, the control device 61 is composed of one or more types of processors, such as a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0031] The storage device 62 is one or more memories that store the programs executed by the control device 61 and the data used by the control device 61. The storage device 62 is configured with a known storage medium such as a magnetic storage medium or a semiconductor storage medium. The storage device 62 may be configured with a combination of multiple types of storage media. A portable storage medium that is detachable from the information processing device 60 may be used as the storage device 62. The storage device 62 of this embodiment stores a reference value R that is applied to the calculation of the principal stress difference Δ. The storage device 62 is an example of a "storage unit."

[0032] The display device 63 displays an image under the control of the control device 61. Specifically, the display device 63 displays the results of the analysis of the test specimen 20. For example, the display device 63 displays the principal stress difference Δ identified as the stress state of the test specimen 20.

[0033] 3 is a block diagram illustrating a functional configuration of the information processing device 60. The control device 61 executes a program stored in the storage device 62 to realize a plurality of functions (a calculation unit 71, a correction unit 72, and an analysis unit 73) for identifying the stress state of the test piece 20.

[0034] The calculation unit 71 calculates the speed at which the surface SH waves propagate through the test piece 20 (hereinafter referred to as "propagation speed Vn") according to the results of reception of the surface SH waves by the measurement sensor 30. Each propagation speed Vn is the speed at which the surface SH waves propagate from the transceiver 35 of the transducer pair 31-n to the transceiver 36 of the transducer pair 31-n (i.e., the speed of sound). The calculation unit 71 calculates the propagation speed Vn (V1 to V4) for each of four different measurement directions D1 to D4. In other words, the propagation speed Vn is the speed at which the surface SH waves propagate in the measurement direction Dn near the surface 21 of the test piece 20. Specifically, the calculation unit 71 determines the time (propagation time) it takes for the surface SH wave to propagate from the transceiver 35 to the transceiver 36 of the transducer pair 31-n by analyzing the detection signal Y, and calculates the propagation velocity Vn by dividing the known distance between the transceiver 35 and the transceiver 36 by the propagation time.

[0035] As explained above, the propagation velocity V1 is the propagation velocity of the surface SH wave in the measurement direction D1 (0°) along the rolling direction Ψ. The propagation velocity V2 is the propagation velocity of the surface SH wave in the measurement direction D2 (90°) perpendicular to the measurement direction D1. The propagation velocity V3 is the propagation velocity of the surface SH wave in the measurement direction D3 inclined at 45° with respect to the measurement direction D1. The propagation velocity V4 is the propagation velocity of the surface SH wave in the measurement direction D4 (135°) perpendicular to the measurement direction D3.

[0036] The calculation unit 71 also calculates the speed at which the surface SH waves propagate through the test piece 20 (hereinafter referred to as the "reference speed U") based on the results of reception of the surface SH waves by the auxiliary sensor 40. The reference speed U is the speed at which the surface SH waves propagate from the transceiver 45 to the transceiver 46 of the auxiliary sensor 40 (i.e., the speed of sound). In other words, the reference speed U is the speed at which the surface SH waves propagate in the reference direction Dref in the vicinity of the surface 21 of the test piece 20. Specifically, the calculation unit 71 determines the time (propagation time) at which the surface SH waves propagate from the transceiver 45 to the transceiver 46 by analyzing the detection signal Z, and calculates the reference speed U by dividing the known distance between the transceiver 45 and the transceiver 46 by the propagation time.

[0037] The propagation velocity Vn depends on the temperature of the test specimen 20. Specifically, the propagation velocity Vn decreases as the temperature of the test specimen 20 increases. The effect of temperature on the propagation velocity Vn is more significant than the effect of stress acting on the test specimen 20. For example, in the case of a typical rolled steel plate, the rate of change of the propagation velocity Vn according to stress is about 0.02 [m / s / MPa], whereas the rate of change of the propagation velocity Vn according to temperature is about -0.5 [m / s / ℃]. Therefore, if the temperature of the test specimen 20 changes in the process of calculating each of the four propagation velocities V1 to V4 in order, there is a possibility that the stress state of the test specimen 20 cannot be accurately identified. In consideration of the above circumstances, the correction unit 72 of this embodiment corrects each propagation velocity Vn according to the temperature of the test specimen 20.

[0038] In a uniaxial stress state where the shear stress is zero, the propagation velocity in the reference direction Dref forming an angle of 45° with respect to the principal stress direction Ω (i.e., the reference velocity U) tends to depend on the temperature of the test specimen 20, but not substantially on the stress state of the test specimen 20. In other words, a change in the reference velocity U occurs due to a change in the temperature of the test specimen 20, and does not substantially occur due to a change in the stress state of the test specimen 20. Therefore, the reference velocity U can be used as an index of the temperature of the test specimen 20. Taking the above tendency into consideration, the correction unit 72 corrects each propagation velocity Vn using the reference velocity U.

[0039] The standard value R stored in the storage device 62 is the reference speed U measured when the test piece 20 is at a standard temperature (hereinafter referred to as the "standard temperature"). In other words, the standard value R is a numerical value that serves as a reference for the reference speed U.

[0040] FIG. 4 is a flowchart of the process in which the control device 61 (the calculation unit 71 and the correction unit 72) calculates and corrects the propagation velocity Vn. As illustrated in FIG. 4, the control device 61 executes a measurement process Pn and a correction process Cn. The measurement process Pn is a process for measuring the propagation velocity Vn and a reference velocity Un. The correction process Cn is a process for correcting the propagation velocity Vn. The correction process Cn is executed after the measurement process Pn is executed. The calculation unit 71 is realized by the control device 61 executing the measurement process Pn, and the correction unit 72 is realized by the control device 61 executing the correction process Cn.

[0041] When the measurement process Pn is started, the control device 61 instructs the driving device 51 to drive the transducer pair 31-n and the transducer pair 41 (S11). The driving device 51 drives the transceiver 35 of the transducer pair 31-n and the transceiver 45 of the transducer pair 41 in response to the instruction from the control device 61. Thus, surface SH waves in the measurement direction Dn are supplied from the transceiver 35 to the test piece 20, and surface SH waves in the reference direction Dref are supplied from the transceiver 45 to the test piece 20. The transmission of surface SH waves by the transceiver 35 and the transmission of surface SH waves by the transceiver 45 are performed sequentially or in parallel (i.e., simultaneously) within a short period of time such that the temperature of the test piece 20 does not substantially fluctuate.

[0042] The transmitter / receiver 36 of the transducer pair 31-n receives the surface SH wave propagated in the measurement direction Dn through the test object 20. The transmitter / receiver 46 of the transducer pair 41 receives the surface SH wave propagated in the reference direction Dref through the test object 20. The detector 52 generates a detection signal Y representing the waveform of the surface SH wave received by the transducer pair 31-n and a detection signal Z representing the waveform of the surface SH wave received by the transducer pair 41. The control device 61 receives the detection signal Y and the detection signal Z from the detector 52 (S12). The control device 61 then calculates the propagation velocity Vn by analyzing the detection signal Y (S13) and calculates the reference velocity Un by analyzing the detection signal Z (S14). The procedure of the measurement process Pn is as described above. As can be understood from the above explanation, the propagation velocity Vn and the reference velocity Un can be regarded as measurement values ​​measured when the test object 20 is at substantially the same temperature.

[0043] The correction process Cn is a process for correcting the propagation velocity Vn measured by the immediately preceding measurement process Pn in accordance with the reference velocity Un measured together with the propagation velocity Vn. When the correction process Cn is started, the control device 61 calculates a correction value Qn (S21). The correction value Qn is the difference between the reference velocity Un and the reference value R stored in the storage device 62 (Qn=Un-R).

[0044] While the standard value R is a propagation speed corresponding to a standard temperature, the reference speed Un measured by the measurement process Pn is a propagation speed corresponding to the current temperature of the test piece 20 (i.e., the time when the propagation speed Vn is measured). As described above, the reference speed Un depends on temperature, so if the temperature of the test piece 20 changes from the standard temperature, the difference between the reference speed Un and the standard value R (i.e., the correction value Qn) increases. On the other hand, if the temperature of the test piece 20 at the time of calculating the reference speed Un is equal to the standard temperature, the reference speed Un and the standard value R are equal in value.

[0045] The control device 61 calculates the corrected propagation velocity Vn by subtracting the correction value Qn from the propagation velocity Vn (S22, Vn←Vn-Qn). As the temperature of the test piece 20 rises in a range above the reference temperature, the reference velocity Un decreases in a range below the reference value R, so the correction value Qn decreases within a negative number range. Therefore, as the temperature of the test piece 20 rises, the corrected propagation velocity Vn becomes a larger value compared to the value before correction. That is, the decrease in the propagation velocity Vn caused by the increase in temperature of the test piece 20 is compensated for.

[0046] On the other hand, as the temperature of the test piece 20 decreases below the reference temperature, the reference velocity Un increases above the reference value R, and therefore the correction value Qn increases within a positive range. Therefore, as the temperature of the test piece 20 decreases, the propagation velocity Vn after correction becomes smaller than the value before correction. In other words, the increase in the propagation velocity Vn caused by the decrease in the temperature of the test piece 20 is compensated for. As described above, the change in the propagation velocity Vn caused by the temperature of the test piece 20 is reduced by the correction process Cn.

[0047] 3 identifies the principal stress difference Δ of the test piece 20 according to each propagation velocity Vn corrected by the correction process Cn. The identification of the principal stress difference Δ using the propagation velocity Vn will be described in detail below.

[0048] FIG. 5 is a graph showing the relationship between the propagation direction θ (horizontal axis) of the surface SH waves on the surface 21 of the test specimen 20 and the propagation velocity V(θ) (vertical axis) of the surface SH waves. The propagation direction θ means the angle with the rolling direction Ψ as the reference (θ=0). FIG. 5 shows both a characteristic F1 when the principal stress difference Δ is 0 and a characteristic F2 when the principal stress difference Δ is not 0. The characteristic F2 is the characteristic when a stress along the rolling direction Ψ (θ=0) is applied to the test specimen 20.

[0049] In Fig. 5, it is assumed that the principal stress direction Ω coincides with the rolling direction Ψ (Ω = 0°). In the above state, as illustrated in Fig. 5, the difference between the propagation velocity V(0°) when the propagation direction θ of the surface SH wave is 0° and the propagation velocity V(90°) when the propagation direction θ is 90° corresponds to the principal stress difference Δ.

[0050] The relationship between the propagation velocity V(θ) of the surface SH wave and the principal stress difference Δ is expressed by the following equation (1).

number

[0051] The symbol Va in formula (1) is the average velocity between the propagation velocity V(θ) and the propagation velocity V(θ+90°). As mentioned above, the symbol θ means the direction of propagation of the surface SH wave based on the rolling direction Ψ.

[0052] Moreover, each symbol (CT, CL, α, β) in the formula (1) is expressed by the following formula: The symbol Cij is an effective elastic constant.

number

[0053] In this embodiment, under the condition that the rolling direction Ψ of the test specimen 20 is known, as described above, the propagation direction θ of the surface SH wave is determined to be a predetermined angle (0°, 45°, 90°, 135°) with respect to the rolling direction Ψ, and the stress state of the test specimen 20 is analyzed. When the propagation direction θ is 0°, 45°, 90°, or 135°, the second term on the right side of the formula (1) becomes 0.

[0054] By setting the propagation direction θ to 0°, the following formula (2) is derived. The propagation velocity V1 in formula (2) corresponds to the propagation velocity V(0°), and the propagation velocity V2 in formula (2) corresponds to the propagation velocity V(90°). The symbol Cs in formula (2) is the acoustoelastic coefficient of the surface SH wave, and is a known value that depends on the material of the test piece 20.

number

[0055] Similarly, by setting the propagation direction θ to 45°, the following formula (3) is derived. The propagation velocity V3 in formula (3) corresponds to the propagation velocity V(45°), and the propagation velocity V4 in formula (3) corresponds to the propagation velocity V(135°).

number

[0056] The analysis unit 73 can calculate the principal stress difference Δ by calculating formula (2) using the propagation velocities V1 and V2, or by calculating formula (3) using the propagation velocities V3 and V4.

[0057] 6 and 7 are flowcharts of a process (hereinafter referred to as a "stress analysis process") for the information processing device 60 to identify the principal stress difference Δ of the test piece 20. For example, the stress analysis process is started in response to an instruction from a user to the information processing device 60.

[0058] When the stress analysis process is started, the control device 61 (the calculation unit 71) executes a setting process Sa for setting a reference value R. For example, the setting process Sa is executed in a state in which the test piece 20 is at a reference temperature.

[0059] When the setting process Sa is started, the control device 61 instructs the driving device 51 to drive the transducer pair 41 of the auxiliary sensor 40 (Sa1). The transceiver 45 of the auxiliary sensor 40 supplies surface SH waves to the test piece 20 in response to a driving signal from the driving device 51. The transceiver 46 of the auxiliary sensor 40 receives the surface SH waves propagating through the test piece 20 in the reference direction Dref. The detection device 52 generates a detection signal Z representing the waveform of the surface SH waves received by the transceiver 46.

[0060] The control device 61 receives the detection signal Z from the detection device 52 (Sa2). The control device 61 calculates the reference value R by analyzing the detection signal Z (Sa3) and stores the reference value R in the memory device 62 (Sa4). As can be understood from the above explanation, the reference value R is an index related to the speed of the surface SH wave propagating in the reference direction Dref in the test object 20, and is calculated according to the result of reception of the surface SH wave by the auxiliary sensor (i.e., the detection signal Z). As described above, in this embodiment, the reference value R is calculated according to the result of reception of the surface SH wave by the auxiliary sensor 40. Therefore, compared to a form in which a numerical value stored in advance in the memory device 62 is used as the reference value R, it is possible to calculate an appropriate principal stress difference according to a state specific to each test object 20, such as the state in which the test object 20 is installed.

[0061] When the setting process Sa is executed, the control device 61 judges whether or not the known principal stress direction Ω coincides with the measurement direction D3 or the measurement direction D4 (Sb), as illustrated in Fig. 7. That is, it is judged whether or not the principal stress direction Ω is a direction at an angle of 45° or 135° with respect to the rolling direction Ψ.

[0062] When the principal stress direction Ω coincides with the measurement direction D3 or the measurement direction D4 (Ω=45°, 135°), the denominator (cos2Ω) of formula (2) is zero, so the principal stress difference Δ cannot be properly calculated by the calculation of formula (2). Therefore, when the principal stress direction Ω coincides with the measurement direction D3 or the measurement direction D4 (Sb: YES), the control device 61 calculates the principal stress difference Δ by the calculation of formula (3) applying the propagation velocity V3 and the propagation velocity V4. On the other hand, when the principal stress direction Ω does not coincide with the measurement direction D3 or the measurement direction D4 (Ω≠45°, 135°), the principal stress difference Δ can be properly calculated by the calculation of formula (2). Therefore, when the principal stress direction Ω does not coincide with the measurement direction D3 or the measurement direction D4 (Sb: NO), the control device 61 calculates the principal stress difference Δ by the calculation of formula (2) applying the propagation velocity V1 and the propagation velocity V2. The specific processing steps are described in detail below.

[0063] First, when the principal stress direction Ω does not coincide with the measurement direction D3 or the measurement direction D4 (Sb: NO), the control device 61 executes a measurement process P1 and a correction process C1 for the propagation velocity V1 in the measurement direction D1, and a measurement process P2 and a correction process C2 for the propagation velocity V2.

[0064] In a measurement process P1, the control device 61 (the calculation unit 71) calculates a propagation speed V1 in the measurement direction D1 according to the reception result of the measurement sensor 30, and calculates a reference speed U1 in the reference direction Dref according to the reception result of the auxiliary sensor 40. In a correction process C1, the control device 61 (the correction unit 72) corrects the propagation speed V1 according to the difference between the reference speed U1 and the reference value R (correction value Q1).

[0065] In a measurement process P2, the control device 61 (the calculation unit 71) calculates a propagation speed V2 in the measurement direction D2 according to the reception result of the measurement sensor 30, and calculates a reference speed U2 in the reference direction Dref according to the reception result of the auxiliary sensor 40. In a correction process C2, the control device 61 (the correction unit 72) corrects the propagation speed V2 according to the difference between the reference speed U2 and the reference value R (correction value Q2).

[0066] The order of the measurement process P1, the correction process C1, the measurement process P2, and the correction process C2 is not limited to the above example. For example, the correction process C1 and the correction process C2 may be performed after the measurement process P1 and the measurement process P2.

[0067] After executing the above processes (P1, C1, P2, C2), the control device 61 (analysis unit 73) executes analysis process A12. In analysis process A12, the control device 61 applies the propagation velocity V1 corrected by the correction process C1 and the propagation velocity V2 corrected by the correction process C2 to formula (2) to calculate the principal stress difference Δ.

[0068] As described above, when the principal stress direction Ω does not coincide with the measurement direction D3 or the measurement direction D4, the calculation unit 71 performs the measurement process P1 and the measurement process P2, the correction unit 72 performs the correction process C1 and the correction process C2, and the analysis unit 73 performs the analysis process A12. The measurement process P1 is an example of a "first measurement process", and the measurement process P2 is an example of a "second measurement process". Furthermore, the correction process C1 is an example of a "first correction process", and the correction process C2 is an example of a "second correction process".

[0069] On the other hand, when the principal stress direction Ω coincides with the measurement direction D3 or the measurement direction D4 (Sb: YES), the control device 61 executes a measurement process P3 and a correction process C3 for the propagation velocity V3 in the measurement direction D3, and a measurement process P4 and a correction process C4 for the propagation velocity V4.

[0070] In a measurement process P3, the control device 61 (the calculation unit 71) calculates a propagation speed V3 in the measurement direction D3 according to the reception result of the measurement sensor 30, and calculates a reference speed U3 in the reference direction Dref according to the reception result of the auxiliary sensor 40. In a correction process C3, the control device 61 (the correction unit 72) corrects the propagation speed V3 according to the difference between the reference speed U3 and the reference value R (correction value Q3).

[0071] In a measurement process P4, the control device 61 (the calculation unit 71) calculates a propagation speed V4 in the measurement direction D4 according to the reception result of the measurement sensor 30, and calculates a reference speed U4 in the reference direction Dref according to the reception result of the auxiliary sensor 40. In a correction process C4, the control device 61 (the correction unit 72) corrects the propagation speed V4 according to the difference between the reference speed U4 and the reference value R (correction value Q4).

[0072] The order of the measurement process P3, the correction process C3, the measurement process P4, and the correction process C4 is not limited to the above example. For example, the correction process C3 and the correction process C4 may be performed after the measurement process P3 and the measurement process P4.

[0073] After executing the above processes (P3, C3, P4, C4), the control device 61 (analysis unit 73) executes analysis process A34. In analysis process A34, the control device 61 applies the propagation velocity V3 corrected by the correction process C3 and the propagation velocity V4 corrected by the correction process C4 to formula (3) to calculate the principal stress difference Δ.

[0074] As described above, when the principal stress direction Ω coincides with the measurement direction D3 or the measurement direction D4, the calculation unit 71 executes the measurement process P3 and the measurement process P4, the correction unit 72 executes the correction process C3 and the correction process C4, and the analysis unit 73 executes the analysis process A34. The measurement process P3 is an example of a "third measurement process", and the measurement process P4 is an example of a "fourth measurement process". Furthermore, the correction process C3 is an example of a "third correction process", and the correction process C4 is an example of a "fourth correction process".

[0075] When the principal stress difference Δ is calculated by the above processing, the control device 61 displays the principal stress difference Δ on the display device 63 (Sc). That is, the result of analyzing the stress state of the test piece 20 is displayed on the display device 63.

[0076] The control device 61 determines whether or not a predetermined termination condition is met (Sd). The termination condition is, for example, when the end of the stress analysis process is instructed by a user, or when the number of calculations of the principal stress difference Δ reaches a predetermined value. If the termination condition is not met (Sd: NO), the control device 61 transitions the process to step Sb. That is, the calculation of the principal stress difference Δ is repeated until the termination condition is met. In each process of calculating the principal stress difference Δ, the reference value R stored in the memory device 62 is commonly used. When the termination condition is met (Sd: YES), the control device 61 terminates the stress analysis process.

[0077] As described above, in this embodiment, the measurement sensor 30 installed based on the known rolling direction Ψ of the test piece 20 is used to identify the stress state of the test piece 20. Therefore, the principal stress difference Δ of the test piece 20 can be easily identified without the need for a procedure of searching for a direction in which the measurement sensor 30 should be installed while changing the angle of the surface SH wave with respect to the test piece 20.

[0078] In this embodiment, the propagation velocity Vn is corrected according to the difference (correction value Qn) between the reference value R for the velocity of the surface SH wave propagating in the reference direction Dref intersecting the known principal stress direction Ω at a predetermined angle (45°) and the reference velocity Un for the velocity at which the surface SH wave propagates in the reference direction Dref. Therefore, without preparing a relationship between the temperature and the propagation velocity in the test piece 20 in advance, the change in the propagation velocity Vn caused by the change in the temperature of the test piece 20 can be compensated for, and the principal stress difference Δ of the test piece 20 can be determined with high accuracy.

[0079] As described above, in a uniaxial stress state where the shear stress is zero, the propagation velocity (reference velocity U) of the reference direction Dref forming an angle of 45° with respect to the principal stress direction Ω does not substantially depend on the stress state of the test piece 20. If it is assumed that the principal stress direction Ω coincides with the rolling direction Ψ (hereinafter referred to as the "comparative example"), the reference direction Dref coincides with the measurement direction D3. Therefore, in the comparative example, it is possible to correct each propagation velocity Vn by using the propagation velocity V3 measured by driving the transducer pair 31-3 as the reference velocity U. That is, the auxiliary sensor 40 is not required in the comparative example.

[0080] However, the comparative example has a problem that the situation in which the principal stress difference Δ can be appropriately determined is limited to the case where the principal stress direction Ω coincides with the rolling direction Ψ. In the present embodiment, the reference speed U is calculated using the auxiliary sensor 40 installed along the principal stress direction Ω. Therefore, in contrast to the comparative example, there is an advantage that the principal stress difference Δ can be appropriately determined even when the principal stress direction Ω and the rolling direction Ψ differ.

[0081] In addition, in this embodiment, when the principal stress direction Ω of the test piece 20 does not coincide with the measurement direction D3 or the measurement direction D4, the principal stress difference Δ is calculated according to the propagation velocity V1 in the measurement direction D1 and the propagation velocity V2 in the measurement direction D2, and when the principal stress direction Ω of the test piece 20 coincides with the measurement direction D3 or the measurement direction D4, the principal stress difference Δ is calculated according to the propagation velocity V3 in the measurement direction D3 and the propagation velocity V4 in the measurement direction D4. That is, the principal stress difference Δ is calculated according to two propagation velocities Vn related to a set of two mutually orthogonal directions. Therefore, the processing load required to identify the principal stress difference Δ is reduced compared to the form in which the principal stress difference Δ is calculated according to four propagation velocities V1 to V4. For example, when the principal stress direction Ω does not coincide with the measurement direction D3 or the measurement direction D4, processing related to the propagation velocity V3 and the propagation velocity V4 (P3, C3, P4, C4, A34) is not necessary, and when the principal stress direction Ω coincides with the measurement direction D3 or the measurement direction D4, processing related to the propagation velocity V1 and the propagation velocity V2 (P1, C1, P2, C2, A12) is not necessary.

[0082] B: Variation Specific modified embodiments added to each of the above-mentioned embodiments are exemplified below. Two or more embodiments selected from the following examples may be appropriately combined as long as they are not mutually contradictory.

[0083] (1) The method of calculating the correction value Qn and the method of correcting the propagation speed Vn using the correction value Qn are not limited to the above-mentioned examples. For example, in the above-mentioned embodiment, the correction value Qn is calculated by subtracting the standard value R from the reference speed Un, but the correction value Qn (Qn=R-Un) may be calculated by subtracting the reference speed Un from the standard value R. In the embodiment in which the reference speed Un is subtracted from the standard value R, the propagation speed Vn after correction is calculated by adding the correction value Qn to the propagation speed Vn.

[0084] For example, as the temperature of the test piece 20 rises in a range above the reference temperature, the reference velocity Un decreases in a range below the reference value R, so the correction value Qn (Qn = R - Un) increases within a range of positive numbers. Therefore, the propagation velocity Vn after correction by adding the correction value Qn becomes a larger value compared to the value before correction as the temperature of the test piece 20 rises. That is, the decrease in the propagation velocity Vn caused by the increase in the temperature of the test piece 20 is compensated. On the other hand, as the temperature of the test piece 20 decreases in a range below the reference temperature, the reference velocity Un increases in a range above the reference value R, so the correction value Qn (Qn = R - Un) decreases within a range of negative numbers. Therefore, the propagation velocity Vn after correction by adding the correction value Qn becomes a smaller value compared to the value before correction as the temperature of the test piece 20 rises. That is, the increase in the propagation velocity Vn caused by the decrease in the temperature of the test piece 20 is compensated. As described above, similar to the second embodiment, the change in the propagation velocity Vn caused by the temperature of the test piece 20 is reduced.

[0085] For example, a data table in which the relationship between the difference between the reference speed Un and the reference value R and the correction value Qn is registered may be used to set the correction value Qn. The control device 61 searches the data table for the correction value Qn corresponding to the difference between the reference speed Un and the reference value R, and corrects the propagation speed Vn using the correction value Qn. Also, for example, an arithmetic expression expressing the relationship between the difference between the reference speed Un and the reference value R and the correction value Qn may be used to set the correction value Qn. The control device 61 calculates the correction value Qn by applying the difference between the reference speed Un and the reference value R to the arithmetic expression.

[0086] (2) In the above embodiment, the measurement sensor 30 is illustrated as having four transducer pairs 31-1 to 31-4 aligned along different measurement directions Dn, but the configuration of the measurement sensor 30 is not limited to the above example. For example, as illustrated in FIG. 8, a measurement sensor 30 in which one transducer pair 31 is rotatably supported may be used. The transducer pair 31 in FIG. 8 is rotatable in any one of four measurement directions D1 to D4. The control device 61 (calculation unit 71) calculates the propagation velocity Vn by analyzing the detection signal Y detected when the transducer pair 31 is aligned along the measurement direction Dn.

[0087] In the above embodiment, the four transducer pairs 31-1 to 31-4 have a common center, but as shown in FIG. 9, the four transducer pairs 31-1 to 31-4 may be arranged in parallel at different positions. According to the configuration of FIG. 9, the paths of the surface SH waves transmitted and received by each transducer pair 31-n do not overlap, so that interference of the surface SH waves in each transducer pair 31-n is suppressed. Therefore, it is possible to drive the four transducer pairs 31-1 to 31-4 in parallel. On the other hand, according to the above embodiment, the four transducer pairs 31-1 to 31-4 have a common center, which is advantageous in that it is easier to miniaturize the measurement sensor 30 compared to the configuration of FIG. 9.

[0088] In the above-described embodiment, the transceiver 35 and the transceiver 36 are used for both transmitting and receiving surface SH waves, but one of the transceiver 35 and the transceiver 36 may be dedicated to transmitting surface SH waves, and the other of the transceiver 35 and the transceiver 36 may be dedicated to receiving surface SH waves. In a configuration in which the transmission / reception of surface SH waves is fixed, the switching device 53 may be omitted. Similarly, for the auxiliary sensor 40, one of the transceiver 45 and the transceiver 46 may be dedicated to transmitting surface SH waves, and the other of the transceiver 45 and the transceiver 46 may be dedicated to receiving surface SH waves. The switching device 54 may be omitted.

[0089] (3) In the above embodiment, the principal stress direction Ω is determined using a sensor such as a strain gauge or a piezoelectric element, but the method for determining the principal stress direction Ω is not limited to the above example. For example, the principal stress direction Ω may be determined using a measurement sensor 30, as shown in the following example.

[0090] From equations (2) and (3), the following equation (4) is derived for calculating the principal stress direction Ω.

number

[0091] (4) In the above-described embodiment, the calculation unit 71 calculates the propagation velocity Vn of the surface SH wave, but the index used to identify the stress state of the test piece 20 is not limited to the propagation velocity Vn. For example, the control device 61 (calculation unit 71) may calculate the propagation time for the surface SH wave to propagate from the transceiver 35 to the transceiver 36 of each transducer pair 31-n. For example, the propagation velocity Vn in the above-described embodiment may be replaced with the reciprocal of the propagation time.

[0092] As can be understood from the above description, the calculation unit 71 is comprehensively expressed as an element that calculates a velocity index related to the velocity at which the surface SH wave propagates through the test piece 20. The velocity index is any index related to the propagation velocity Vn of the surface SH wave. That is, in addition to the propagation velocity Vn exemplified in the above embodiment, any index linked to the propagation velocity Vn, such as the propagation time or the reciprocal of the propagation time, is included in the concept of the "velocity index."

[0093] Similarly, in the above-described embodiment, the calculation unit 71 calculates the propagation velocity of the surface SH wave as the reference velocity U, but the index used to correct the propagation velocity Vn is not limited to the reference velocity U. For example, the control device 61 (calculation unit 71) may apply the propagation time for the surface SH wave to propagate from the transceiver 45 to the transceiver 46 of the transducer pair 41 to correct the propagation velocity Vn. For example, the reference velocity U in the above-described embodiment may be replaced with the reciprocal of the propagation time.

[0094] As can be understood from the above explanation, the indices used for correcting the propagation velocity Vn are comprehensively expressed as indices (reference indices) related to the velocity at which the surface SH wave propagates in the reference direction Dref through the test piece 20. That is, in addition to the reference velocity U exemplified in the above embodiment, any indices linked to the propagation velocity in the reference direction Dref, such as the propagation time or the reciprocal of the propagation time, are included in the concept of the "reference indices."

[0095] (5) In the above embodiment, the reference direction Dref forms an angle of 45° with respect to the principal stress direction Ω, but the reference direction Dref may be a direction that forms an angle of substantially 45° with respect to the principal stress direction Ω, in addition to a direction that forms an angle of strictly 45° with respect to the principal stress direction Ω. Specifically, even if the angle between the reference direction Dref and the principal stress direction Ω does not strictly coincide with 45°, the reference direction Dref can be interpreted as forming an angle of substantially 45° with respect to the principal stress direction Ω as long as it is within the range of the measurement error of the principal stress direction Ω or the installation error of the auxiliary sensor 40.

[0096] As described above, in a uniaxial stress state where the shear stress is zero, the propagation velocity of the surface SH wave in the reference direction Dref that forms an angle of 45° with respect to the principal stress direction Ω tends to be substantially independent of the stress state of the test specimen 20. Therefore, according to a configuration in which the reference direction Dref intersects with the principal stress direction Ω at 45°, the change in the propagation velocity caused by the change in temperature of the test specimen 20 can be compensated with high accuracy. As can be understood from the above explanation, the reference direction Dref can also be expressed as a direction in which the propagation velocity is substantially independent of the stress state of the test specimen 20.

[0097] (6) In the above embodiment, the principal stress difference Δ of the test specimen 20 identified by the stress analysis process is displayed on the display device 63, but the method of processing the analysis results is not limited to the above example. For example, a form in which the normal / abnormal state of the test specimen 20 is determined by comparing the principal stress difference Δ identified by the stress analysis process with a predetermined threshold value, and an alarm is output when the test specimen 20 is determined to be abnormal, is also conceivable. In other words, the output of the principal stress difference Δ is not essential to the present disclosure.

[0098] (7) As described above, the functions of the information processing device 60 according to the embodiment are realized by the cooperation of one or more processors constituting the control device 61 and the program stored in the storage device 62. The above-mentioned programs can be provided in a form stored in a computer-readable recording medium and installed in the computer. The recording medium is, for example, a non-transitory recording medium, and a good example is an optical recording medium (optical disk) such as a CD-ROM, but also includes any known type of recording medium such as a semiconductor recording medium or a magnetic recording medium. Note that the non-transitory recording medium includes any recording medium except for a transient propagating signal, and does not exclude volatile recording media. In addition, in a configuration in which a distribution device distributes a program via a communication network, the recording medium that stores the program in the distribution device corresponds to the non-transitory recording medium described above.

[0099] C: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0100] A stress analysis system according to one aspect (aspect 1) of the present disclosure includes a memory unit that stores a reference value for the speed of surface SH waves propagating in a reference direction that intersects with a principal stress direction of a test piece at a predetermined angle, a measurement sensor that receives surface SH waves propagating through the test piece in each of a first direction along the rolling direction of the test piece and a second direction perpendicular to the first direction, an auxiliary sensor that receives surface SH waves propagating through the test piece in the reference direction, and an information processing unit including a calculation unit, a correction unit, and an analysis unit, wherein the calculation unit calculates a first speed index for the speed at which surface SH waves propagate in the first direction based on the reception result of the measurement sensor, and calculates a first reference index for the speed at which surface SH waves propagate in the reference direction based on the reception result of the auxiliary sensor. the correction unit executes a first correction process to correct the first velocity index according to the difference between the first reference index and the reference value, and a second correction process to correct the second velocity index according to the difference between the second reference index and the reference value, and the analysis unit executes an analysis process to identify a principal stress difference of the test piece according to the first velocity index after correction by the first correction process and the second velocity index after correction by the second correction process.

[0101] In the above-mentioned embodiment, the measurement sensor installed based on the known rolling direction of the test specimen is used to identify the principal stress difference of the test specimen. Therefore, the principal stress difference of the test specimen can be easily identified without the need for a procedure of searching for a direction in which the measurement sensor should be installed while changing the angle of the ultrasonic wave with respect to the test specimen.

[0102] In addition, the velocity index is corrected according to the difference between a reference value for the velocity of surface SH waves propagating in a reference direction intersecting the known principal stress direction at a predetermined angle and a reference index for the velocity of surface SH waves propagating in the reference direction. Therefore, without preparing a relationship between the temperature of the test specimen and the velocity index in advance, the principal stress difference of the test specimen can be determined with high accuracy by compensating for the change in the velocity index caused by the change in the temperature of the test specimen.

[0103] The first direction is, for example, a direction parallel to the rolling direction. The direction parallel to the rolling direction includes a direction strictly parallel to the rolling direction as well as a direction substantially parallel to the rolling direction. A direction substantially parallel to the rolling direction is a direction inclined to the rolling direction within a range in which the effects of the present disclosure are realized. For example, a direction inclined to the rolling direction within a range of manufacturing error can be interpreted as a direction along the rolling direction.

[0104] The second direction is a direction perpendicular to the first direction. The direction perpendicular to the first direction includes a direction strictly perpendicular to the first direction as well as a direction substantially perpendicular to the first direction. A direction substantially perpendicular to the first direction is a direction inclined with respect to the first direction within a range in which the effects of the present disclosure are realized. For example, a direction within a range of 90°±10° (more preferably ±5°) with respect to the first direction is interpreted as a direction substantially perpendicular to the first direction. The orthogonality between the third direction and the fourth direction can be interpreted in the same manner.

[0105] In a specific example (aspect 2) of aspect 1, the measurement sensor further receives surface SH waves propagating through the test piece in each of a third direction inclined with respect to the first direction and a fourth direction perpendicular to the third direction, and when the principal stress direction does not coincide with the third direction or the fourth direction, the first measurement process and the second measurement process by the calculation unit, the first correction process and the second correction process by the correction unit, and the analysis process by the analysis unit are executed, and when the principal stress direction coincides with the third direction or the fourth direction, the calculation unit calculates a third velocity index related to the velocity at which the surface SH wave propagates in the third direction according to the reception result of the measurement sensor, and a third reference index related to the velocity at which the surface SH wave propagates in the reference direction. based on the reception results of the auxiliary sensor, and a fourth measurement process of calculating a fourth velocity index related to the velocity at which surface SH waves propagate in the fourth direction based on the reception results of the measurement sensor and a fourth reference index related to the velocity at which surface SH waves propagate in the reference direction based on the reception results of the auxiliary sensor, the correction unit executes a third correction process of correcting the third velocity index based on the difference between the third reference index and the reference value, and a fourth correction process of correcting the fourth velocity index based on the difference between the fourth reference index and the reference value, and the analysis unit executes an analysis process of identifying a principal stress difference of the test specimen based on the third velocity index after correction by the third correction process and the fourth velocity index after correction by the fourth correction process.

[0106] In the above-mentioned aspect, when the principal stress direction of the test specimen does not coincide with the third or fourth direction, the principal stress difference is calculated according to the first speed index in the first direction and the second speed index in the second direction, and when the principal stress direction of the test specimen coincides with the third or fourth direction, the principal stress difference is calculated according to the third speed index in the third direction and the fourth speed index in the fourth direction. That is, the principal stress difference is calculated according to two speed indexes related to a set of two mutually orthogonal directions. Therefore, the processing load required to identify the principal stress difference is reduced compared to the aspect in which the principal stress difference is calculated according to the first speed index, the second speed index, the third speed index, and the fourth speed index.

[0107] The third direction is a direction inclined at a predetermined angle with respect to the first direction. A direction inclined at a predetermined angle with respect to the first direction includes a direction that is strictly at the predetermined angle with respect to the first direction, as well as a direction that is substantially at the predetermined angle with respect to the first direction. For example, a direction within a range of a predetermined angle of ±10° (more preferably ±5°) with respect to the first direction is interpreted as a direction inclined at a predetermined angle with respect to the first direction.

[0108] In a specific example (Aspect 3) of Aspect 1 or Aspect 2, the reference value is calculated according to the reception result of the auxiliary sensor. In the above aspects, the reference value is calculated according to the reception result of the surface SH waves by the auxiliary sensor. Therefore, compared to a form in which a fixed reference value R that is set statistically or experimentally and stored in advance in a storage device is applied, it is possible to calculate an appropriate principal stress difference according to the unique state of each test specimen.

[0109] In a specific example (Aspect 4) of any one of Aspects 1 to 3, the predetermined angle is 45°. In a uniaxial stress state where the shear stress is zero, the propagation velocity of the surface SH wave in the reference direction that forms an angle of 45° with the principal stress direction tends to depend on the temperature of the test specimen, but is substantially independent of the stress state of the test specimen. Therefore, according to the embodiment in which the reference direction intersects with the principal stress direction at 45°, the change in the propagation velocity caused by the change in the temperature of the test specimen can be compensated for with high accuracy. [Explanation of symbols]

[0110] 100...stress analysis system, 20...test specimen, 21...surface, 30...measurement sensor, 31...vibrator pair, 32...support member, 33...coupling medium, 35...transmitter / receiver, 36...transmitter / receiver, 40...auxiliary sensor, 41...vibrator pair, 42...support member, 43...coupling medium, 45...transmitter / receiver, 46...transmitter / receiver, 50...measuring device, 51...driving device, 52...detection device, 53, 54...switching device, 60...information processing device, 61...control device, 62...storage device, 63...display device, 71...calculation unit, 72...correction unit, 73...analysis unit.

Claims

1. a memory unit that stores a reference value related to the velocity of a surface SH wave propagating in a reference direction that intersects with a principal stress direction of a test specimen at a predetermined angle; a measurement sensor that receives surface SH waves propagating through the test piece in each of a first direction along the rolling direction of the test piece and a second direction perpendicular to the first direction; an auxiliary sensor for receiving a surface SH wave propagating through the test object in the reference direction; An information processing unit including a calculation unit, a correction unit, and an analysis unit, The calculation unit is a first measurement process for calculating a first velocity index related to the velocity at which a surface SH wave propagates in the first direction according to a reception result of the measurement sensor, and for calculating a first reference index related to the velocity at which a surface SH wave propagates in the reference direction according to a reception result of the auxiliary sensor; a second measurement process for calculating a second velocity index related to the velocity at which surface SH waves propagate in the second direction in accordance with the reception result of the measurement sensor, and for calculating a second reference index related to the velocity at which surface SH waves propagate in the reference direction in accordance with the reception result of the auxiliary sensor; The correction unit is a first correction process for correcting the first speed indicator according to a difference between the first reference indicator and the reference value; a second correction process for correcting the second speed index according to a difference between the second reference index and the reference value; The analysis unit executes an analysis process for identifying a principal stress difference of the test specimen according to a first speed index corrected by the first correction process and a second speed index corrected by the second correction process. Stress analysis system.

2. The measurement sensor further receives surface SH waves propagating through the test object in each of a third direction inclined with respect to the first direction and a fourth direction perpendicular to the third direction; when the principal stress direction does not coincide with the third direction or the fourth direction, the first measurement process and the second measurement process are performed by the calculation unit, the first correction process and the second correction process are performed by the correction unit, and the analysis process is performed by the analysis unit; When the principal stress direction coincides with the third direction or the fourth direction, The calculation unit is a third measurement process for calculating a third velocity index related to the velocity at which a surface SH wave propagates in the third direction according to the reception result of the measurement sensor, and calculating a third reference index related to the velocity at which a surface SH wave propagates in the reference direction according to the reception result of the auxiliary sensor; a fourth measurement process for calculating a fourth velocity index related to the velocity at which surface SH waves propagate in the fourth direction in accordance with the reception result of the measurement sensor, and for calculating a fourth reference index related to the velocity at which surface SH waves propagate in the reference direction in accordance with the reception result of the auxiliary sensor; The correction unit is a third correction process for correcting the third speed index according to a difference between the third reference index and the reference value; a fourth correction process for correcting the fourth speed index according to a difference between the fourth reference index and the reference value; The analysis unit executes an analysis process for identifying a principal stress difference of the test specimen according to a third speed index corrected by the third correction process and a fourth speed index corrected by the fourth correction process. The stress analysis system of claim 1 .

3. The reference value is calculated according to the reception result of the auxiliary sensor. The stress analysis system of claim 1 .

4. The predetermined angle is 45°. The stress analysis system according to any one of claims 1 to 3.

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