JP5251911B2 - Residual stress calculation device, residual stress measurement device, residual stress calculation method, residual stress measurement method, and program - Google Patents

Description

  The present invention relates to a residual stress calculation device, a residual stress measurement device, a residual stress calculation method, a residual stress measurement method, and a program.

  Residual stress (residual stress) remaining inside the object to be inspected, such as a metal plate, creates a complex and uneven stress distribution and greatly affects the mechanical properties of the object to be inspected. Measuring the magnitude of the stress accurately is an important technique for maintaining the performance of the object to be inspected. For this reason, various studies have been made on techniques for measuring the stress remaining in an object to be inspected, such as a metal plate, and various methods have been proposed.

  For example, in Patent Document 1 and Patent Document 2 below, X-rays or neutron beams are irradiated onto an object to be inspected, and the lattice spacing of the crystal is measured from the obtained diffraction pattern to measure the stress of the object to be inspected. A method is disclosed. In Non-Patent Document 1 below, acoustoelastic parameters are measured from the acoustic velocities of longitudinal and transverse waves propagating in the object to be inspected, and the principal stress is calculated from the relationship between the principal stress sum and the principal stress difference measured in advance. A method of calculating is disclosed. Here, the acoustoelastic parameter is a parameter calculated from a plurality of ultrasonic sound velocities correlated with the principal stress sum or the principal stress difference.

JP 60-78336 A JP-A-8-327471

Japan Nondestructive Inspection Association, “Acoustic Elasticity”, 1994 edition, Japan Nondestructive Inspection Association, November 1994, p. 25-26

  However, the method described in Patent Document 1 has a problem that only the residual stress on the surface of the object to be inspected can be measured. Moreover, although the method described in Patent Document 2 can measure the residual stress inside the object to be inspected, there is a problem that the measuring apparatus becomes large-scale. Moreover, since the methods described in Patent Document 1 and Patent Document 2 are methods using X-rays or neutron beams, there is a problem that there is a risk of exposure.

  On the other hand, although the method of Non-Patent Document 1 can measure the residual stress inside the object to be inspected with a relatively simple measuring device, the measurement error increases when the object to be inspected is plastically deformed. There was a problem.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to safely and accurately measure the stress remaining in the plastically deformed object. Another object is to provide a residual stress calculation device, a residual stress measurement device, a residual stress calculation method, a residual stress measurement method, and a program.

  In order to solve the above-described problem, according to one aspect of the present invention, sound speed information related to a plurality of ultrasonic sound speeds in a metal plate measured by generating a plurality of ultrasonic waves in a plastically deformed metal plate is obtained. The sound velocity information acquisition unit, the plastic deformation amount of the metal plate or a plastic deformation feature amount calculation unit that calculates a plastic deformation feature amount that is a value that can be converted into the plastic deformation amount, and the sound speed acquired by the sound speed information acquisition unit. Based on the information, the acoustoelastic parameter calculating unit for calculating the acoustoelastic parameter in the metal plate, and the plastic deformation feature amount calculated by the plastic deformation feature amount calculating unit, the stress of the acoustoelastic parameter A sound elasticity parameter coefficient correction unit that corrects a coefficient representing a change caused by the sound elasticity parameter, a sound elasticity parameter calculated by the sound elasticity parameter calculation unit, a coefficient corrected by the sound elasticity parameter coefficient correction unit, Based on the residual stress calculation unit for calculating a stress remaining in the metal plate, the residual stress calculating device with a provided.

  The residual stress calculation device further includes a storage unit storing correlation information representing a relationship between the coefficient and the plastic deformation feature amount, and the acoustoelastic parameter coefficient correction unit is the correlation stored in the storage unit. Preferably, the coefficient is determined using information and the plastic deformation feature amount calculated by the plastic deformation feature amount calculation unit.

The acoustoelastic parameter calculation unit calculates the sound velocity ratio R and the acoustic birefringence B as the acoustoelastic parameters using the sound velocity information, and the acoustoelastic parameter coefficient correction unit includes the plastic deformation feature amount calculation unit. calculated based on the plastic deformation characteristic quantity, the coefficient C _R and R ₀ in formula 1 _below, as well, it is preferable to determine the coefficients C _a and B ₀ in equation 2 below.

Here, in the following formulas 1 and 2, σ ₁ and σ ₂ represent main stresses remaining in the metal plate.

The residual stress calculation unit includes a sound speed ratio R and an acoustic birefringence B calculated by the acoustoelastic parameter calculation unit, and the coefficients R ₀ , C _R , B ₀ and C _A determined by the acoustoelastic parameter coefficient correction unit. It is preferable to calculate the principal stress remaining on the metal plate based on the formula 1 and the formula 2 using

The plastic deformation feature amount may be a plastic strain generated in the metal plate.
The plastic deformation feature amount may be a thickness reduction ratio that is a rate of change in the thickness of the metal plate accompanying plastic deformation.

  In order to solve the above problem, according to another aspect of the present invention, by generating a plurality of ultrasonic waves in a plastically deformed metal plate, the plurality of ultrasonic waves propagating in the metal plate are generated. A sonic velocity measuring device for measuring the sonic velocity, and a residual stress calculating device for calculating a residual stress in the plastically deformed metal plate using a measurement result of the sonic velocity measured by the sonic velocity measuring device. The stress calculation device includes a sound speed information acquisition unit that acquires sound speed information that is a measurement result regarding a plurality of ultrasonic sound speeds propagating in the plastically deformed metal plate from the sound speed measurement device, and a plastic deformation amount of the metal plate or Based on the sound velocity information acquired by the plastic deformation feature amount calculating unit that calculates a plastic deformation feature amount that is a value that can be converted into a plastic deformation amount, and calculating the acoustic elasticity parameter in the metal plate Sound elasticity A parameter calculation unit, a acoustoelastic parameter coefficient correction unit that corrects a coefficient representing a change due to stress in the acoustoelastic parameter using the plastic deformation feature value calculated by the plastic deformation feature value calculation unit, and A residual stress calculating unit that calculates a residual stress on the metal plate based on the acoustoelastic parameter calculated by the acoustoelastic parameter calculating unit and the coefficient corrected by the acoustoelastic parameter coefficient correcting unit. A stress measurement device is provided.

  In order to solve the above problems, according to still another aspect of the present invention, the present invention relates to a plurality of ultrasonic sound speeds in a metal plate measured by generating a plurality of ultrasonic waves in a plastically deformed metal plate. Obtaining a sound velocity information; calculating a plastic deformation amount of the metal plate or a plastic deformation feature amount that is a value that can be converted into a plastic deformation amount; and, based on the obtained sound velocity information, a sound in the metal plate. A step of calculating an elastic parameter; a step of correcting a coefficient representing a change of the acoustoelastic parameter due to stress using the calculated plastic deformation feature; a calculated acoustoelastic parameter; and a corrected coefficient And calculating a residual stress on the metal plate, based on the above.

  In order to solve the above problems, according to still another aspect of the present invention, the plurality of ultrasonic waves propagating in the metal plate by generating the plurality of ultrasonic waves in the plastically deformed metal plate. A step of measuring the sound velocity of the metal plate, a step of obtaining sound velocity information that is a measurement result of a plurality of ultrasonic sound velocities propagating in the metal plate, and a plastic deformation amount of the metal plate or a value that can be converted into a plastic deformation amount. While calculating a certain plastic deformation feature amount, calculating the acoustoelastic parameter in the metal plate based on the acquired sound velocity information, and using the calculated plastic deformation feature amount, Correcting a coefficient representing a change due to stress, and calculating a residual stress on the metal plate based on the calculated acoustoelastic parameter and the corrected coefficient. Residual stress measurement method is provided.

  In order to solve the above problems, according to still another aspect of the present invention, a plurality of ultrasonic waves in a metal plate measured by causing a computer to generate a plurality of ultrasonic waves in a plastically deformed metal plate. A sound speed information acquisition function for acquiring sound speed information related to the sound wave speed, a plastic deformation feature amount calculation function for calculating a plastic deformation feature amount that is a value that can be converted into a plastic deformation amount or a plastic deformation amount of the metal plate, and the sound speed information. Based on the sound velocity information acquired by the acquisition function, using the acoustoelastic parameter calculation function for calculating the acoustoelastic parameter in the metal plate, and the plastic deformation feature amount calculated by the plastic deformation feature amount calculation function, A acoustoelastic parameter coefficient correction function for correcting a coefficient representing a change due to stress of the acoustoelastic parameter, an acoustoelastic parameter calculated by the acoustoelastic parameter calculation function, and the acoustoelastic parameter. Based on the coefficient meter factor correction function is corrected, program for implementing a residual stress calculating function of calculating a stress remaining in the metal plate is provided.

  As described above, according to the present invention, the acoustoelastic parameter calculated from the relationship of the sound velocity of the sound wave propagating through the metal plate and the correction value for correcting the influence of plastic deformation on the acoustoelastic parameter are used. Thus, since the residual stress in the metal plate is calculated, it is possible to safely and accurately measure the stress remaining in the plastically deformed test object.

It is explanatory drawing which showed the structure of the residual stress measuring apparatus which concerns on the 1st Embodiment of this invention. It is explanatory drawing which showed the example of the sound speed measuring apparatus which concerns on the same embodiment. It is the block diagram which showed the structure of the residual stress calculation apparatus which concerns on the same embodiment. It is the graph which showed the relationship between the plastic strain and the coefficient of the acoustoelastic parameter. It is the graph which showed the relationship between the plastic strain and the coefficient of the acoustoelastic parameter. It is the graph which showed the relationship between the plastic strain and the coefficient of the acoustoelastic parameter. It is the graph which showed the relationship between the plastic strain and the coefficient of the acoustoelastic parameter. It is the graph which showed the stress measurement result when correct | amending by plastic strain. It is the graph which showed the stress measurement result when correct | amending by plastic strain. It is the graph which showed the change of the measurement error when correct | amending by plastic strain. It is the graph which showed the change of the measurement error when correct | amending by plastic strain. It is the graph which showed the relationship between plastic strain and a thinning ratio. It is the graph which showed the relationship between the thinning ratio and the coefficient of the acoustoelastic parameter. It is the graph which showed the relationship between the thinning ratio and the coefficient of the acoustoelastic parameter. It is the graph which showed the relationship between the thinning ratio and the coefficient of the acoustoelastic parameter. It is the graph which showed the relationship between the thinning ratio and the coefficient of the acoustoelastic parameter. It is the graph which showed the stress measurement result when correct | amending by the thickness reduction ratio. It is the graph which showed the stress measurement result when correct | amending by the thickness reduction ratio. It is the graph which showed the change of the measurement error when correct | amending by the thinning ratio. It is the graph which showed the change of the measurement error when correct | amending by the thinning ratio. It is the flowchart which showed the flow of the residual stress calculation method which concerns on the same embodiment. It is the block diagram which showed the hardware constitutions of the residual stress calculation apparatus which concerns on embodiment of this invention. It is the flowchart which showed the flow of the residual stress measuring method using the conventional acoustoelastic effect. It is the graph which showed the measurement result of the acoustoelastic parameter when there is no plastic strain. It is the graph which showed the measurement result of the acoustoelastic parameter when there is no plastic strain. It is the graph which showed the measurement result of the acoustoelastic parameter when there exists plastic strain. It is the graph which showed the measurement result of the acoustoelastic parameter when there exists plastic strain. It is the graph which showed the stress measurement result when not considering plastic strain. It is the graph which showed the stress measurement result when not considering plastic strain.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(the purpose)
First, prior to describing the embodiment of the present invention, a conventional method for measuring residual stress using the acoustoelastic effect will be described with reference to FIGS. 19 to 25, and the problems of the conventional residual stress measuring method will be clarified. To. Further, the purpose of the present invention based on the problems of the conventional residual stress measurement method will be described. FIG. 19 is a flowchart showing the flow of a conventional residual stress measurement method using the acoustoelastic effect. 20 and 21 are graphs showing measurement results of acoustoelastic parameters when there is no plastic strain. 22 and 23 are graphs showing measurement results of acoustoelastic parameters when there is plastic strain. 24 and 25 are graphs showing stress measurement results when plastic strain is not considered.

  First, with reference to FIG. 19, the flow of a conventional residual stress measurement method using the acoustic elasticity effect will be briefly described.

  In the conventional residual stress measurement method using the acoustoelastic effect, first, the sound velocity of the sound wave (ultrasonic wave) propagating inside the object to be inspected (for example, a metal plate) is measured using a predetermined sound velocity measuring device. (Step S11). Specifically, longitudinal sound waves and transverse wave ultrasonic waves are generated inside the object to be inspected using a sound velocity measuring device, and the multiple reflection echo interval is measured or the resonance frequency is measured. Thereby, for example, the following physical quantities can be measured for the longitudinal ultrasonic waves and the transverse ultrasonic waves.

・ About longitudinal waves Echo interval _TL
Resonant frequency f _Ln (n is the order)
・ About transverse waves Echo interval T _S1 , T _S2
Resonant frequencies f _S1n , f _S2n (n is the order)

  Here, between the sound velocity and the echo interval, and between the sound velocity and the resonance frequency, the propagation distance of the ultrasonic wave (for example, the thickness of the object to be inspected) t is used, and is expressed by the following equations 11 and 12. The relationship is established. In the following formulas 11 and 12, C represents the speed of sound. N is the order of the resonance frequency.

C = 2t / T (Formula 11)
C = 2f _n t / n (Expression 12)

In Equation 11, T indicates the longitudinal wave echo interval T _L and the transverse wave echo intervals T _S1 and T _S2 , and in Equation 12, f _n represents the longitudinal wave resonance frequency f _Ln and the transverse wave frequency. The resonance frequencies f _S1n and f _S2n are indicated.

Thus, by utilizing the physical quantity obtained from the longitudinal ultrasonic waves (the echo interval or a resonance frequency), it is possible to calculate the sound velocity C _L of longitudinal ultrasonic waves, using a physical quantity obtained from the transverse ultrasonic waves Thus, the sound speeds C _S1 and C _S2 of the transverse ultrasonic waves can be calculated.

  Subsequently, in the conventional residual stress measurement method using the acoustoelastic effect, various acoustoelastic parameters are calculated using the measured sound speed (step S13). Examples of such acoustoelastic parameters include a sound speed ratio R expressed by the following formula 13 and an acoustic birefringence B expressed by the following formula 14.

  Here, the residual stress measurement method using the acoustoelastic effect is not intended to measure the speed of sound, as will be described below, but using the acoustoelastic parameters as shown in the above equations 13 and 14, The purpose is to measure the main stress remaining in the test object. As is clear from the contents of Equation 13 and Equation 14 above, the numerator and denominator of the equation representing the acoustoelastic parameter include the same order of sound velocity. The propagation distance of the sound wave is canceled by the numerator and the denominator. Therefore, in the conventional residual stress measurement method using the acoustoelastic effect, if measurement values such as the echo interval and the resonance frequency are used, the propagation distance of the ultrasonic wave (for example, the thickness of the object to be inspected) is There is no need to measure.

  Subsequently, in the conventional residual stress measurement method, the stress remaining in the object to be inspected is calculated using the calculated acoustoelastic parameter (step S15).

Here, the relationship between the sound velocity ratio R and the acoustic birefringence B is expressed by the following equations 15 and 16 between the main stresses σ ₁ and σ ₂ remaining in the object to be inspected. It has been known.

Here, in the above formula 15, C _R is a coefficient representing a change in the sound velocity ratio by the main stress sum changes, the constant term R ₀ is the speed of sound ratio under no stress. In the above equation 16, C _A is a coefficient representing the change in acoustic birefringence due to the change in main stress difference, and the constant term B ₀ represents the tissue anisotropy when the test object is not stressed.

Therefore, the relationship between the sound speed ratio R and the principal stress sum (σ ₁ + σ ₂ ) and the relationship between the acoustic birefringence B and the principal stress difference (σ ₁ −σ ₂ ) are measured in advance for a certain object to be inspected. Then, the main stress sum and the main stress difference are calculated from the calculated acoustoelastic parameters, and the main stresses σ ₁ and σ ₂ remaining in the object to be inspected are calculated.

  Here, two types of steel plates having different tensile strengths (Sample A: tensile strength 980 MPa class high strength steel plate with a thickness of 1 mm, sample B: tensile strength 590 MPa class high strength steel plate with a thickness of 1.4 mm) are used as test objects. The acoustoelastic parameter was measured while applying a load with a tensile tester. The two types of prepared steel plates are not plastically deformed. The obtained measurement results are shown in FIGS.

  20 and 21, the upper graph is a graph showing the relationship between the sound speed ratio R and the stress (that is, the magnitude of the load applied to the steel sheet, which corresponds to the principal stress sum). Further, the lower graph is a graph showing the relationship between the acoustic birefringence B and the stress (that is, the magnitude of the load applied to the steel sheet and corresponding to the main stress difference).

As apparent from FIGS. 20 and 21, it is understood that there is a linear relationship between the applied load (stress) and the acoustoelastic parameter when plastic deformation does not occur in the steel plate as the object to be inspected. Therefore, since the principal stress sum and the principal stress difference can be calculated from the calculated acoustoelastic parameters by using this linear relationship, the principal stresses σ ₁ and σ ₂ remaining in the inspection object are specified. be able to.

  On the other hand, the measurement result of the acoustoelastic parameter when a large strain is applied to the inspection object and the inspection object is subjected to plastic strain will be described. Predetermined plastic strain was given to the above-mentioned sample A and sample B, and the acoustoelastic parameters were measured while applying tensile stress to the sample given these plastic strains with a tensile tester.

The obtained results are shown in FIG. 22 and FIG.
In addition, the magnitude | size of the plastic strain given with respect to the steel plate is shown by the ratio which the steel plate extended. For example, the notation of 2% in each graph means that a tensile stress that increases the length of the steel sheet by 2% is applied by applying a tensile stress to the steel sheet. As is apparent from each graph, the inclination of the graph and the position of the intercept change due to the presence of plastic strain. The fact that the inclination of the graph and the position of the intercept are different indicate that the acoustoelastic parameter is changed even under the same stress condition due to the occurrence of plastic strain.

  The results of calculating the residual stress based on the acoustoelastic parameters shown in FIGS. 22 and 23 using the relationship between the acoustoelastic parameters and the stress when no plastic strain exists, as shown in FIGS. 24 and 25. FIG. 24 shows the residual stress measurement results for sample A, and FIG. 25 shows the residual stress measurement results for sample B.

The measurement performed is based on the result of a uniaxial tensile test performed on a steel plate as an object to be inspected. Therefore, a linear relationship that increases according to the tensile stress is established for the principal stress σ _{1 in the} direction parallel to the tensile direction, and the principal stress σ _{2 in the} direction orthogonal to the tensile direction is near 0 regardless of the tensile stress. A constant value is expected. 24 and 25, it can be seen that as the plastic strain increases, the error in the measurement result increases as compared to the case where there is no plastic strain (0%).

  As described above, in the conventional residual stress measurement method using the acoustoelastic effect, when a strain corresponding to the plastic deformation region, not the elastic deformation region, is applied to the inspection object, the error becomes large, and the inspection object There is a problem that the magnitude of the residual stress cannot be measured accurately.

  Therefore, the present inventors have aimed to find a method for calculating a residual stress that can accurately calculate the magnitude of the stress remaining in the object to be inspected even if the object is plastically deformed. As a result, we conducted intensive studies. As a result, the inventors have arrived at a residual stress calculation method and a residual stress measurement method according to an embodiment of the present invention as described below.

(First embodiment)
<About the configuration of the residual stress measurement device>
First, the configuration of the residual stress measurement apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory view showing a configuration of a residual stress measuring apparatus according to this embodiment.

  The residual stress measuring apparatus 10 according to the present embodiment is an apparatus that measures the stress remaining in the metal plate sample S that is an object to be inspected. As illustrated in FIG. 1, the residual stress measuring device 10 mainly includes a sound speed measuring device 100 and a residual stress calculating device 200.

  In addition to the apparatus shown in FIG. 1, the residual stress measuring apparatus 10 according to the present embodiment is an apparatus that measures surface roughness, an apparatus that measures strain such as a strain gauge, and a metal that is an object to be inspected. Various devices for measuring the thickness of the plate may be provided.

[Sonic velocity measuring device]
The sound velocity measuring apparatus 100 is an apparatus that generates ultrasonic waves on a metal plate sample S that is an object to be inspected and measures the sound velocity of ultrasonic waves that propagate through the metal plate S. The sound velocity measuring apparatus 100 may be a sing-around method, a pulse echo overlap method, a pulse superposition method, a resonance method, a time interval averaging method, or the like. Hereinafter, for example, the case where the sound velocity measuring device 100 using the multiple reflection echo interval or the sound velocity measuring device 100 using the resonance frequency as shown in FIG. 2 is used will be described. The apparatus 100 is not limited to the example shown in FIG.

FIG. 2 is an explanatory diagram showing the configuration of the sound velocity measuring apparatus 100 according to the present embodiment.
First, with reference to FIG. 2 (a), the configuration of a sound speed measuring apparatus using multiple reflection echo intervals will be briefly described.

  As shown in FIG. 2A, the sound velocity measuring device 100 using the multiple reflection echo interval mainly includes a pulsar receiver 101 and a probe 103.

  The pulsar receiver 101 is a so-called ultrasonic wave receiving / transmitting device, and transmits the generated ultrasonic wave to the metal plate S, which is an object to be inspected, via a probe 103 to be described later, and the reflected wave reflected in the metal plate S. Is a device that receives

  The probe 103 transmits the ultrasonic wave generated by the pulsar receiver 101 to the metal plate S and receives the reflected wave reflected in the metal plate S.

  In the sound velocity measurement method using the multiple reflection echo interval, multiple reflected waves such as a first reflected wave, a second reflected wave,... Are observed as shown in the graph on the right side of FIG. Interval (echo interval, time T in the graph of FIG. 2A) is measured. The echo interval of the multiple reflected waves has a relationship as shown in the above equation 11 with the sound velocity C in the metal plate, where the thickness t of the metal plate S is a parameter. The speed of sound in the metal plate S can be calculated from the interval T.

  Next, with reference to FIG. 2 (b), the configuration of the sound speed measuring device using the resonance frequency will be briefly described.

  As shown in FIG. 2B, the sound velocity measuring apparatus 100 using the resonance frequency includes a sine wave generator 111, a burst wave generator 113, and an electromagnetic ultrasonic transducer (Electro-Magnetic Acoustic Transducer: EMAT). 115 and an integrator 117 are mainly provided.

  The sine wave generator 111 is a device that generates a sine wave having an arbitrary frequency. The sine wave generated by the sine wave generator 111 is used as a carrier wave when the burst wave generator 113 described later generates a burst wave.

  The burst wave generator 113 is a device that generates a burst wave by using the sine wave generated by the sine wave generator 111 as a carrier wave. The burst wave generated by the burst wave generator 113 is transmitted to the metal plate S via the EMAT 115 described later. The burst wave generator 113 transmits the reflected wave reflected in the metal plate S received via the EMAT 115 to the integrator 117 described later.

  The electromagnetic ultrasonic transducer (EMAT) 115 converts the burst wave generated by the burst wave generator 113 into vibration (that is, ultrasonic wave) and transmits the vibration to the metal plate S that is an object to be inspected. The EMAT 115 receives the reflected wave reflected in the metal plate S, converts it into an electrical signal, and transmits it to the burst wave generator 113. By using this EMAT 115, a contact medium such as water or oil becomes unnecessary, and it is possible to measure the speed of ultrasonic waves propagating through the metal plate S in a non-contact manner.

  The integrator 117 is a device that integrates an electrical signal corresponding to the ultrasonic wave (reflected wave reflected in the metal plate S) received by the EMAT 115. With this integrator 117, it is possible to specify the resonance frequency of the ultrasonic wave that has propagated through the metal plate S.

The speed-of-sound measurement method using the resonance frequency, as shown in FIG. 2 (b) graph shown on the right side, the resonance frequency _{f 0, f 1, f 2} , observes ..., these resonant frequencies f _n taking measurement. The resonance frequency has a relationship as shown in the above equation 12 with the sound speed C in the metal plate when the plate thickness t of the metal plate S is used as a parameter. Therefore, the sound speed in the metal plate S is calculated from this resonance frequency. Can be calculated.

  Note that the sonic velocity measuring apparatus 100 shown in FIG. 2 preferably generates longitudinal and transverse ultrasonic waves on the metal plate S, which is an object to be inspected. The type is not limited to the above example. The sound velocity measuring device 100 may generate various ultrasonic waves such as SH waves and measure the sound velocity of the ultrasonic waves propagating through the object to be inspected.

  For example, when the sound speed is measured using surface SH waves, the sound speed is measured using acoustic anisotropy ΦS shown in the following expression 17 instead of the above expression 16 as an expression combined with the above expression 15. It is possible.

Here, in Expression 17, V _S1 and V _S2 are the sound speeds of the surface SH waves deflected in the main stress direction, and C _S is a coefficient representing a change in acoustic anisotropy due to a change in main stress difference.

  The measurement result relating to the sound velocity of the ultrasonic wave propagating through the metal plate S measured by such a sound velocity measuring device 100 is notified to the later-described residual stress calculating device 200 as sound velocity information relating to the sound velocity.

The sound velocity measuring apparatus 100 according to the present embodiment has been described above.
Next, the configuration of the residual stress calculation device 200 provided in the residual stress measurement device 10 according to the present embodiment will be described with reference to FIG.

[Residual stress calculation device]
FIG. 3 is a block diagram showing the configuration of the residual stress calculation apparatus 200 according to this embodiment. As shown in FIG. 3, the residual stress calculation apparatus 200 according to the present embodiment includes a sound speed information acquisition unit 201, a sound elastic parameter calculation unit 203, a plastic deformation feature amount calculation unit 205, and a sound elastic parameter coefficient correction unit. 207, a storage unit 209, and a residual stress calculation unit 211 are mainly provided. Further, the residual stress calculation device 200 may further include a display control unit 213 and a display unit 215.

  The sound speed information acquisition unit 201 is realized by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a communication device, and the like. The sound speed information acquisition unit 201 acquires information (sound speed information) about the sound speed in the metal plate measured by the sound speed measuring device 100 generating ultrasonic waves in the plastically deformed metal plate. The sound speed information preferably includes information on the sound speed of the longitudinal wave measured using longitudinal wave ultrasonic waves and information on the sound speed of the transverse waves measured using two types of transverse wave ultrasonic waves. This sound speed information may be information representing the sound speed itself, or may be information that can be used to calculate the sound speed such as the echo interval and the resonance frequency. The sound speed information acquisition unit 201 outputs the acquired sound speed information (that is, information related to the sound speed measurement value) to the sound elasticity parameter calculation unit 203 described later.

  The acoustic elasticity parameter calculation unit 203 is realized by, for example, a CPU, a ROM, a RAM, and the like. The sound elasticity parameter calculation unit 203 calculates a sound elasticity parameter related to the metal plate S that is an object to be inspected based on the sound speed information notified from the sound speed information acquisition unit 201. Specifically, the sound elasticity parameter calculation unit 203 calculates a physical quantity correlated with the sum or difference of main stresses remaining in the metal plate based on the sound speed information notified from the sound speed information acquisition unit 201. Calculate as Examples of such physical quantities that have a correlation with the sum or difference of main stresses include the sound speed ratio R and the acoustic birefringence B. In the following description, it is assumed that the acoustic elasticity parameter calculation unit 203 calculates the sound speed ratio R and the acoustic birefringence B as the acoustic elasticity parameters.

  The sound elasticity parameter calculation unit 203 calculates the sound speed ratio R based on the following equation 101 using the sound speed information notified from the sound speed information acquisition unit 201. Further, the acoustic elasticity parameter calculation unit 203 calculates the acoustic birefringence B based on the following equation 102 using the acoustic velocity information notified from the acoustic velocity information acquisition unit 201. When the calculation of the sound velocity ratio R and the acoustic birefringence B is completed, the acoustoelastic parameter calculation unit 203 outputs the calculated acoustoelastic parameters to the residual stress calculation unit 211 described later.

  The plastic deformation feature amount calculation unit 205 is realized by, for example, a CPU, a ROM, a RAM, a communication device, and the like. The plastic deformation feature amount calculation unit 205 calculates a plastic deformation feature amount representing the magnitude of plastic deformation of the metal plate. This plastic deformation feature amount may be the plastic deformation amount itself measured by a strain gauge or the like, or may be a thickness reduction ratio calculated from the plate thickness before and after deformation, which can be converted into the plastic deformation amount. Here, the thickness reduction ratio calculated from the plate thickness before and after deformation is a value defined by the following equation. Other values that can be converted into the amount of plastic deformation include surface roughness, hardness, plastic deformation amount estimated from FEM analysis results, and the like.

Thinning ratio = (t−t ₀ ) / t ₀

Here, in the definition formula of the thickness reduction ratio, t ₀ indicates the plate thickness of the metal plate before plastic deformation is applied, and t indicates the plate thickness of the metal plate after plastic deformation is applied. Show.

  The plastic deformation feature quantity calculation unit 205 outputs the acquired plastic deformation quantity itself or a plastic deformation feature quantity that can be converted into the plastic deformation quantity to the acoustoelastic parameter coefficient correction unit 207 described later.

  The plastic deformation feature quantity calculation unit 205 may refer to various calibration curves, approximate expressions, look-up tables, databases, and the like stored in the storage unit 209 and the like described later when calculating the plastic deformation feature quantity. .

  The acoustoelastic parameter coefficient correction unit 207 is realized by, for example, a CPU, a ROM, a RAM, and the like. The acoustoelastic parameter coefficient correcting unit 207 corrects a coefficient representing a change due to stress in the acoustoelastic parameter using the plastic deformation feature amount calculated by the plastic deformation feature amount calculating unit. Hereinafter, the coefficient correction process performed by the acoustoelastic parameter coefficient correction unit 207 will be described in more detail.

  As shown in Equations 15 and 16, the acoustoelastic parameter calculated by the acoustoelastic parameter calculation unit 203 is an amount formulated using the sum and difference of main stresses. Therefore, in the residual stress calculation apparatus 200 according to the present embodiment, the coefficient values included in the theoretical expressions such as Expression 15 and Expression 16 are corrected in order to correct the change in the acoustoelastic parameter due to plastic deformation.

  In the residual stress calculation apparatus 200 according to the present embodiment, the relationship between the plastic deformation feature amount calculated by the plastic deformation feature amount calculation unit 205 and the coefficient of the theoretical formula as described in Equation 15 and Equation 16 or the like. Is generated in advance.

  For example, consider a case where the acoustoelastic parameters calculated by the acoustoelastic parameter calculating unit 203 are the sound velocity ratio R and the acoustic birefringence B, and the plastic deformation feature amount calculated by the plastic deformation feature amount calculating unit 205 relates to plastic strain. . In this case, a calibration curve, an approximate expression, a look-up table, a database, and the like corresponding to the correlation information shown below are created in advance and stored in the storage unit 209 of the residual stress calculation device 200.

- correlation information expressing the relationship between the coefficient C _R shown in plastic strain and expression 15 - plastic strain and correlation information expressing the relationship between the coefficient R ₀ shown in Formula 15 - coefficient shown in plastic strain and Formula 16 C _A Information representing the relationship between the correlation strain and the correlation information representing the relationship between the plastic strain and the coefficient B ₀ shown in Equation 16

  The acoustoelastic parameter coefficient correction unit 207 uses the various calibration curves corresponding to the correlation information and the plastic deformation feature amount notified from the plastic deformation feature amount calculation unit 205 to notify the notified plastic deformation feature. The coefficient value corresponding to the quantity is calculated. Thereby, each coefficient described in Expression 15 and Expression 16 is corrected.

  The acoustoelastic parameter coefficient correction unit 207 outputs the corrected coefficient to the residual stress calculation unit 211 described later.

  The storage unit 209 is an example of a storage device included in the residual stress calculation device 200 according to the present embodiment. The storage unit 209 shows the correlation between the plastic deformation feature quantity and the proportional coefficient and the correlation between the plastic deformation feature quantity and the constant term, which the acoustoelastic parameter coefficient correction unit 207 uses when correcting the coefficient of the acoustoelastic parameter. Various calibration curves, approximate equations, lookup tables, databases, and the like are stored. The storage unit 209 may store various calibration curves, approximate expressions, look-up tables, databases, and the like that are used when the plastic deformation feature amount calculation unit 205 calculates the plastic deformation feature amount. Furthermore, in the storage unit 209, the residual stress calculation device 200 according to the present embodiment stores various parameters, processes in progress, or various databases that need to be stored when performing some processing, Recorded as appropriate. The storage unit 209 can be freely read and written by each processing unit included in the residual stress calculation apparatus 200.

  The residual stress calculation unit 211 is realized by, for example, a CPU, a ROM, a RAM, and the like. The residual stress calculation unit 211 uses the acoustoelastic parameter calculated by the acoustoelastic parameter calculation unit 203 and the coefficient corrected by the acoustoelastic parameter coefficient correction unit 207 to remain on the metal plate S that is an object to be inspected. Calculate the magnitude of the principal stress. Hereinafter, the calculation procedure of the residual stress performed by the residual stress calculation unit 211 will be described in detail.

The residual stress calculation unit 211 includes an acoustoelastic parameter formulated using the sum of main stresses calculated by the acoustoelastic parameter calculation unit 203 and an acoustoelastic parameter formulated using the difference between main stresses. Entered. The residual stress calculation unit 211 corrects the values of the two types of acoustoelastic parameters using the coefficients notified from the acoustoelastic parameter coefficient correction unit 207. Thereafter, the residual stress calculation unit 211 calculates the magnitudes of the main stress σ ₁ and the main stress σ ₂ using two types of corrected acoustic elasticity parameters.

  Here, the acoustoelastic parameters calculated by the acoustoelastic parameter calculating unit 203 are the acoustic velocity ratio R (acoustoelastic parameter formulated using the sum of main stresses) and acoustic birefringence B (using the difference between main stresses). It is assumed that the acoustic elasticity parameter is formulated.

The residual stress calculation unit 211 uses the acoustic velocity ratio R and the acoustic birefringence B notified from the acoustoelastic parameter calculation unit 203 as the coefficients R ₀ , C _R , B ₀ , C _A notified from the acoustoelastic parameter coefficient correction unit 207. Is used to correct as shown on the right side of the following Expression 103 and Expression 104. Here, Formula 103 and Formula 104 shown below are modified from the definition formulas (Formula 15 and Formula 16) of the sound speed ratio R and the acoustic birefringence B.

The values obtained as a result of the correction are values corresponding to the sum of the main stresses and the difference between the main stresses, as is apparent from the left side of the equations 103 and 104. Therefore, the residual stress calculation unit 211 calculates main stresses σ ₁ and σ ₂ remaining on the metal plate S by using the following formulas 105 and 106 and values obtained as a result of correction.

The principal stresses σ ₁ and σ ₂ calculated in this way are calculated in consideration of the effect of plastic deformation on the acoustoelastic parameter, and even if the object to be inspected is undergoing plastic deformation. Thus, a more accurate result can be obtained as compared with the conventional residual stress measurement method using the acoustoelastic effect.

  The residual stress calculation unit 211 outputs the calculation result of the residual stress remaining in the inspected object calculated in this way to the display control unit 213 described later. Further, the residual stress calculation unit 211 may record the calculation result of the residual stress in the storage unit 209 or the like as history information in association with information on the date and time when the residual stress is calculated, information on the object to be inspected, or the like. Further, the residual stress calculation unit 211 may output the calculated residual stress to various devices provided outside the residual stress calculation device 200. The calculation result may be output directly via a predetermined communication network or indirectly via various recording media.

  The display control unit 213 is realized by, for example, a CPU, a ROM, a RAM, and the like. The display control unit 213 performs display control when displaying the magnitude of the residual stress of the metal plate S, which is the object to be inspected, calculated by the residual stress calculation unit 211 on the display unit 215 included in the residual stress calculation device 200. In addition to the calculation result of the residual stress, the display control unit 213 also includes the calculated acoustoelastic parameter value, the corrected coefficient value, and the correlation between the plastic deformation feature value and the acoustoelastic parameter coefficient. Various types of information such as a graph diagram representing the above can be displayed on the display unit 215.

  The display unit 215 is realized by, for example, a CPU, a ROM, a RAM, an output device, and the like. The display unit 215 displays various types of information including the calculation result of the residual stress on an output device such as a display provided in the residual stress calculation device 200 while being controlled by the display control unit 213. Thereby, the user of the residual stress calculation apparatus 200 can grasp the magnitude of the residual stress remaining on the metal plate as the object to be inspected on the spot.

  Heretofore, an example of the function of the residual stress calculation device 200 according to the present embodiment has been shown. Each component described above may be configured using a general-purpose member or circuit, or may be configured by hardware specialized for the function of each component. In addition, the CPU or the like may perform all functions of each component. Therefore, it is possible to appropriately change the configuration to be used according to the technical level at the time of carrying out the present embodiment.

  A computer program for realizing each function of the residual stress calculation apparatus according to the present embodiment as described above can be produced and installed in a personal computer or the like. In addition, a computer-readable recording medium storing such a computer program can be provided. The recording medium is, for example, a magnetic disk, an optical disk, a magneto-optical disk, a flash memory, or the like. Further, the above computer program may be distributed via a network, for example, without using a recording medium.

<Specific example of residual stress calculation method>
Subsequently, a specific example of a residual stress calculation method performed by the residual stress calculation device 200 according to the present embodiment will be described with reference to FIGS. 4A to 16.

[When plastic strain is used as a plastic deformation feature]
First, an example in which plastic strain is used as the plastic deformation feature amount will be specifically described with reference to FIGS. 4A to 9. 4A to 5B are graphs showing the relationship between the plastic strain and the coefficient of the acoustoelastic parameter. 6 and 7 are graphs showing stress measurement results when correction is made by plastic strain. 8 and 9 are graphs showing changes in measurement error when correction is made by plastic strain.

  Specific examples shown below are two types of steel plates having different tensile strengths as samples to be inspected (sample A: tensile strength 980 MPa class high strength steel plate with a thickness of 1 mm, sample B: tensile strength 590 MPa class high tension with a thickness of 1.4 mm). It is the result of having prepared and measured it.

  First, attention is focused on FIGS. 4A to 5B. 4A and 4B are graphs showing the relationship between the plastic strain and the coefficient of the acoustoelastic parameter for the sample A. FIGS. 5A and 5B show the coefficient of the plastic strain and the acoustoelastic parameter for the sample B. It is the graph which showed this relationship. 4A and 5A show measurement results regarding the sound speed ratio R of each sample, and FIGS. 4B and 5B show measurement results regarding the acoustic birefringence B of each sample.

  Here, in FIG. 4A to FIG. 5B, the horizontal axis represents the plastic strain (%) given in advance to the object to be inspected, and the magnitude of the plastic strain is shown by the rate at which the steel plate is stretched. Moreover, the vertical axis | shaft of each graph figure has shown the magnitude | size of the coefficient. Each coefficient is measured by using a tensile tester for each sample having plastic deformation corresponding to each plastic strain value, and for example, graphs as shown in FIGS. 20 and 21 are created. It calculated by calculating | requiring the inclination and intercept value. Each graph shows an approximate straight line representing the relationship between the plastic strain and the coefficient, and an approximate expression thereof.

  As is clear from each graph, it was found that there was a correlation between the coefficient and the plastic strain, and the relationship between the two could be linearly approximated, for example. Therefore, the approximate expression obtained from each graph was used as information representing the correlation between the plastic strain and the coefficient, and the residual stress of Sample A and Sample B was calculated.

  That is, the plastic deformation feature amount calculation unit 205 obtains information on the change in length of the metal plate before and after the plastic deformation is applied, calculates the ratio of the length change, and uses the obtained value as the plastic deformation feature amount. (That is, plastic strain in FIGS. 4A to 5B). Further, the acoustoelastic parameter coefficient correcting unit 207 determines each coefficient by substituting the magnitude of the plastic strain calculated for each approximate expression of the corresponding sample. Thereafter, the residual stress calculation unit 211 calculates the residual stress of the sample A and the sample B using the coefficient calculated by the acoustoelastic parameter coefficient correction unit 207 and the acoustoelastic parameter calculated by the acoustoelastic parameter calculation unit 203. did.

The obtained results (residual stress measurement results) are shown in FIGS. 6 and 7, the horizontal axis represents stress (tensile stress, unit MPa), and the vertical axis represents the magnitude of main stress (MPa). 6 and 7, when attention is paid to the principal stress σ ₁ in a direction parallel to the direction in which the tensile stress is applied, the principal stress obtained even if the magnitude of the plastic deformation applied to the metal plate is changed. There is no significant change in the magnitude of σ ₁ as shown in FIGS. Further, when attention is paid to the principal stress σ ₂ in the direction orthogonal to the direction in which the tensile stress is applied, it can be seen that the values are almost constant in the vicinity of 0 in FIGS.

  8 and 9 show how the measurement error changes when correction is made by plastic strain. 8 and 9 plot the difference between the magnitude of the tensile stress actually applied and the calculated principal stress. As is apparent from FIGS. 8 and 9, when correction by plastic strain is not performed (FIGS. 8A and 9A), the error increases as the plastic strain increases. I understand that. In addition, when the correction by plastic strain is performed (FIGS. 8B and 9B), the error does not increase even when the plastic strain increases, and the absolute value of the error does not increase. It can be seen that the value is also smaller than when no correction is made.

  In this way, by calculating the residual stress after correcting by plastic strain, it is possible to accurately calculate the residual stress even when plastic deformation is applied to the metal plate that is the object to be inspected. Is possible.

[When using the reduction ratio as a plastic deformation feature value]
Subsequently, an example in the case of using the thickness reduction ratio as the plastic deformation feature amount will be specifically described with reference to FIGS. FIG. 10 is a graph showing the relationship between the plastic strain and the thinning ratio. 11A to 12B are graphs showing the relationship between the thinning ratio and the coefficient of the acoustoelastic parameter. FIG. 13 and FIG. 14 are graphs showing the stress measurement results when correction is performed by the thinning ratio. FIG. 15 and FIG. 16 are graphs showing changes in measurement error when correction is performed using the thinning ratio.

Below, the example at the time of utilizing the thickness reduction ratio represented by the following formula | equation 107 as a plastic deformation feature-value is demonstrated. In the following expression 107, t ₀ indicates the plate thickness of the metal plate before plastic deformation is applied, and t indicates the plate thickness of the metal plate after plastic deformation is applied. As is clear from the following formula 107, the thickness reduction ratio is a parameter indicating the rate of change in plate thickness due to plastic deformation.

Thinning ratio = (t−t ₀ ) / t ₀ (Equation 107)

  Here, the thickness of the metal plate as the object to be inspected can use the measurement result by a micrometer or the like, and can also use the estimation result by FEM analysis. In the example shown below, The measurement result with a micrometer was used.

  FIG. 10 shows the correlation between the plastic strain and the thinning ratio actually calculated for Sample A and Sample B described above. As is clear from FIG. 10, since a correlation is recognized between the plastic strain and the thinning ratio, the residual stress remaining in the object to be inspected can be calculated by using the thinning ratio instead of the plastic strain. It is considered possible to do.

  Therefore, for sample A and sample B, the relationship between the thinning ratio due to plastic deformation and the coefficient was measured. The obtained result is FIG. 11A-FIG. 12B. 11A and 11B are graphs showing the relationship between the thinning ratio and the coefficient of acoustoelastic parameter for sample A. FIGS. 12A and 12B are the graphs of the thinning ratio and acoustoelastic parameter for sample B. It is the graph which showed the relationship with a coefficient. Moreover, FIG. 11A and FIG. 12A have shown the measurement result regarding the sound speed ratio R of each sample, and FIG. 11B and FIG. 12B have shown the measurement result regarding the acoustic birefringence B of each sample.

In FIG. 11A and the like, a description such as “8.0E-06” is made, which corresponds to a value of “8.0 × 10 ⁻⁶ ”.

  As is apparent from the graphs, a correlation was recognized between the coefficient of the acoustoelastic parameter and the thinning ratio, and it was found that the relationship between the two can be linearly approximated, for example. Accordingly, the approximate expression obtained from each graph was used as information indicating the correlation between the thinning ratio and the coefficient of the acoustoelastic parameter, and the residual stress of Sample A and Sample B was calculated.

The obtained results (residual stress measurement results) are shown in FIGS. 13 and 14, the horizontal axis represents stress (tensile stress, unit MPa), and the vertical axis represents the magnitude of main stress (MPa). 13 and 14, when attention is paid to the principal stress σ ₁ in the direction parallel to the direction in which the tensile stress is applied, the principal stress obtained even if the magnitude of the plastic deformation applied to the metal plate changes. There is no significant change in the magnitude of σ ₁ as shown in FIGS. Further, when attention is paid to the main stress σ ₂ in the direction orthogonal to the direction in which the tensile stress is applied, it can be seen that the values are almost constant in the vicinity of 0 in FIGS.

  FIG. 15 and FIG. 16 show how the measurement error changes when correction is performed using the thinning ratio. As is apparent from FIGS. 15 and 16, when the correction by the thinning ratio is not performed (FIGS. 15A and 16A), the error increases as the absolute value of the thinning ratio increases. You can see that Further, when the correction by the thinning ratio is performed (FIGS. 15B and 16B), the error does not increase even if the absolute value of the thinning ratio increases, and the error It can be seen that the absolute value of is smaller than the case where no correction is made.

  In this way, the plastic deformation is applied to the metal plate, which is the object to be inspected, by calculating the residual stress after performing correction using the feature quantity correlated with the plastic strain, not the plastic strain itself. Even in this case, the residual stress can be calculated with high accuracy.

  In FIGS. 4A to 5B and FIGS. 11A to 12B, the correlation between the coefficient of the acoustoelastic parameter and the plastic deformation feature amount is approximated by linear approximation. Approximation may be performed using various curves such as multi-order functions such as... Exponential function, logarithmic function.

<Residual stress calculation method flow>
Subsequently, a flow of a residual stress calculation method performed by the residual stress calculation apparatus 200 according to the present embodiment will be briefly described with reference to FIG. FIG. 17 is a flowchart showing the flow of the residual stress calculation method according to this embodiment.

  Prior to the following description, it is assumed that information indicating the correlation between the plastic deformation feature quantity and the coefficient of the acoustoelastic parameter is stored in advance in the storage unit 209 and the like of the residual stress calculation device 200.

  First, the sound speed information acquisition unit 201 of the residual stress calculation apparatus 200 acquires sound speed information (sound speed measurement result) about a metal plate that is an object to be inspected from, for example, the sound speed measurement apparatus 100 (step S101). When the sound speed information acquisition unit 201 acquires sound speed information about the object to be inspected, the sound speed information acquisition unit 201 outputs the acquired sound speed information to the sound elasticity parameter calculation unit 203.

  Next, the sound elasticity parameter calculation unit 203 calculates the sound elasticity parameter of the metal plate using the sound speed information notified from the sound speed information acquisition unit 201 (step S103). The calculated acoustoelastic parameters are, for example, acoustoelastic parameters formulated using the sum of principal stresses, and acoustoelastic parameters formulated using the difference of principal stresses. As an example, the sound speed ratio R and the acoustic birefringence B can be mentioned. The acoustoelastic parameter calculation unit 203 outputs the calculated acoustoelastic parameter to the residual stress calculation unit 211.

  On the other hand, the plastic deformation feature amount calculation unit 205 of the residual stress calculation device 200 acquires information such as plastic strain, plate thickness, and length of a metal plate that is an object to be inspected, and is a feature amount indicating the degree of plastic deformation. A certain plastic deformation feature amount is calculated (step S105). As an example of such a plastic deformation feature amount, plastic strain, a thickness reduction ratio, and the like can be given. The plastic deformation feature amount calculation unit 205 outputs the calculated plastic deformation feature amount to the acoustoelastic parameter coefficient correction unit 207.

  The acoustoelastic parameter coefficient correcting unit 207 uses the plastic deformation feature amount notified from the plastic deformation feature amount calculating unit 205 and the information indicating the correlation stored in the storage unit 209 and the like to calculate the acoustoelastic parameter. The coefficient is corrected (step S107). The coefficient of the acoustoelastic parameter is, for example, a coefficient that appears in the equation when the acoustoelastic parameter is formulated using the sum or difference of main stresses. When the acoustoelastic parameter coefficient correcting unit 207 corrects the acoustoelastic parameter coefficient, the acoustoelastic parameter coefficient correcting unit 207 outputs the corrected acoustoelastic parameter coefficient to the residual stress calculating unit 211.

  Next, the residual stress calculation unit 211 corrects the acoustoelastic parameter notified from the acoustoelastic parameter calculation unit 203 using the coefficient notified from the acoustoelastic parameter coefficient correction unit 207. Thereby, the value of the acoustoelastic parameter considering the influence of plastic deformation can be obtained. Thereafter, the residual stress calculation unit 211 calculates the residual stress remaining on the metal plate, which is the object to be inspected, using the corrected acoustoelastic parameter (step S109).

  By performing the process according to the flow described above, the residual stress calculation method according to the present embodiment calculates the residual stress with high accuracy even when the metal plate as the object to be inspected is plastically deformed. It becomes possible to do.

  FIG. 17 shows a case where a series of flows for calculating the acoustoelastic parameter and a series of flows for calculating the plastic deformation feature amount are performed in parallel. The flow relating to the calculation and the flow relating to the calculation of the plastic deformation feature amount do not have to be performed in parallel.

(About hardware configuration)
Next, the hardware configuration of the residual stress calculation device 200 according to the embodiment of the present invention will be described in detail with reference to FIG. FIG. 18 is a block diagram for explaining a hardware configuration of the residual stress calculation apparatus 200 according to the embodiment of the present invention.

  The residual stress calculation apparatus 200 mainly includes a CPU 901, a ROM 903, and a RAM 905. The residual stress calculation device 200 further includes a bus 907, an input device 909, an output device 911, a storage device 913, a drive 915, a connection port 917, and a communication device 919.

  The CPU 901 functions as an arithmetic processing unit and a control unit, and controls all or a part of the operation in the residual stress calculation device 200 according to various programs recorded in the ROM 903, the RAM 905, the storage device 913, or the removable recording medium 921. . The ROM 903 stores programs used by the CPU 901, calculation parameters, and the like. The RAM 905 primarily stores programs used in the execution of the CPU 901, parameters that change as appropriate during the execution, and the like. These are connected to each other by a bus 907 constituted by an internal bus such as a CPU bus.

  The bus 907 is connected to an external bus such as a PCI (Peripheral Component Interconnect / Interface) bus via a bridge.

  The input device 909 is an operation unit operated by the user, such as a mouse, a keyboard, a touch panel, a button, a switch, and a lever. The input device 909 may be, for example, remote control means (so-called remote control) using infrared rays or other radio waves, or may be an external connection device 923 such as a PDA corresponding to the operation of the residual stress calculation device 200. There may be. Furthermore, the input device 909 includes, for example, an input control circuit that generates an input signal based on information input by a user using the operation unit and outputs the input signal to the CPU 901. The user of the residual stress calculation device 200 can input various data and instruct a processing operation to the residual stress calculation device 200 by operating the input device 909.

  The output device 911 is configured by a device that can notify the user of the acquired information visually or audibly. Examples of such devices include CRT display devices, liquid crystal display devices, plasma display devices, EL display devices and display devices such as lamps, audio output devices such as speakers and headphones, printer devices, mobile phones, and facsimiles. The output device 911 outputs results obtained by various processes performed by the residual stress calculation device 200, for example. Specifically, the display device displays the results obtained by the various processes performed by the residual stress calculation device 200 as text or an image. On the other hand, the audio output device converts an audio signal composed of reproduced audio data, acoustic data, and the like into an analog signal and outputs the analog signal.

  The storage device 913 is a data storage device configured as an example of a storage unit of the residual stress calculation device 200. The storage device 913 includes, for example, a magnetic storage device such as an HDD (Hard Disk Drive), a semiconductor storage device, an optical storage device, or a magneto-optical storage device. The storage device 913 stores programs executed by the CPU 901, various data, various data acquired from the outside, and the like.

  The drive 915 is a recording medium reader / writer, and is built in or externally attached to the residual stress calculation apparatus 200. The drive 915 reads information recorded on a removable recording medium 921 such as a mounted magnetic disk, optical disk, magneto-optical disk, or semiconductor memory, and outputs the information to the RAM 905. The drive 915 can also write a record on a removable recording medium 921 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. The removable recording medium 921 is, for example, a CD medium, a DVD medium, a Blu-ray medium, or the like. The removable recording medium 921 may be a CompactFlash (registered trademark) (CompactFlash: CF), a flash memory, an SD memory card (Secure Digital memory card), or the like. Further, the removable recording medium 921 may be, for example, an IC card (Integrated Circuit card) on which a non-contact IC chip is mounted, an electronic device, or the like.

  The connection port 917 is a port for directly connecting a device to the residual stress calculation device 200. Examples of the connection port 917 include a USB (Universal Serial Bus) port, an IEEE 1394 port, a SCSI (Small Computer System Interface) port, and an RS-232C port. By connecting the external connection device 923 to the connection port 917, the residual stress calculation device 200 acquires various data directly from the external connection device 923 or provides various data to the external connection device 923.

  The communication device 919 is a communication interface configured with, for example, a communication device for connecting to the communication network 925. The communication device 919 is, for example, a communication card for wired or wireless LAN (Local Area Network), Bluetooth (registered trademark), or WUSB (Wireless USB). The communication device 919 may be a router for optical communication, a router for ADSL (Asymmetric Digital Subscriber Line), or a modem for various communication. The communication device 919 can transmit and receive signals and the like according to a predetermined protocol such as TCP / IP, for example, with the Internet and other communication devices. The communication network 925 connected to the communication device 919 is configured by a wired or wireless network, and may be, for example, the Internet, a home LAN, infrared communication, radio wave communication, satellite communication, or the like. .

  Heretofore, an example of the hardware configuration capable of realizing the function of the residual stress calculation device 200 according to the embodiment of the present invention has been shown. Each component described above may be configured using a general-purpose member, or may be configured by hardware specialized for the function of each component. Therefore, it is possible to change the hardware configuration to be used as appropriate according to the technical level at the time of carrying out this embodiment.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the acoustic velocity ratio R and the acoustic birefringence B are exemplified as the acoustoelastic parameters. However, in the residual stress calculation method according to the embodiment of the present invention, the acoustoelastic parameters are limited to the above-described example. I don't mean. For example, instead of the acoustic birefringence B, a acoustoelastic parameter relating to the sound velocity anisotropy of the surface SH wave may be used.

DESCRIPTION OF SYMBOLS 10 Residual stress measuring device 100 Sonic measuring device 101 Pulsar receiver 103 Probe 111 Sine wave generator 113 Burst wave generator 115 Electromagnetic ultrasonic transducer (EMAT)
117 Integrator 200 Residual Stress Calculation Device 201 Sonic Information Acquisition Unit 203 Acoustoelastic Parameter Calculation Unit 205 Plastic Deformation Feature Quantity Calculation Unit 207 Acoustoelastic Parameter Coefficient Correction Unit 209 Storage Unit 211 Residual Stress Calculation Unit 213 Display Control Unit 215 Display Unit S Metal plate

Claims (10)

A sound speed information acquisition unit for acquiring sound speed information related to a plurality of ultrasonic sound speeds in the metal plate measured by generating a plurality of ultrasonic waves in the plastically deformed metal plate;
A plastic deformation feature amount calculating unit that calculates a plastic deformation feature amount that is a value that can be converted into a plastic deformation amount or a plastic deformation amount of the metal plate;
Based on the sound speed information acquired by the sound speed information acquisition unit, a sound elasticity parameter, which is a parameter correlated with a main stress sum or a main stress difference, is calculated from a plurality of ultrasonic sound speeds in the metal plate. An acoustoelastic parameter calculator;
An acoustoelastic parameter coefficient correction unit that corrects a coefficient representing a change of the acoustoelastic parameter due to stress using the plastic deformation feature value calculated by the plastic deformation feature value calculating unit;
Based on the acoustoelastic parameter calculated by the acoustoelastic parameter calculating unit and the coefficient corrected by the acoustoelastic parameter coefficient correcting unit, a residual stress calculating unit that calculates the residual stress on the metal plate;
A residual stress calculation device comprising: The residual stress calculation device further includes a storage unit storing correlation information representing a relationship between the coefficient and the plastic deformation feature amount,
The acoustoelastic parameter coefficient correction unit determines the coefficient using the correlation information stored in the storage unit and the plastic deformation feature amount calculated by the plastic deformation feature amount calculation unit. The residual stress calculation apparatus according to claim 1. The sound elasticity parameter calculation unit calculates a sound speed ratio R and an acoustic birefringence B as the sound elasticity parameters using the sound speed information,
The acoustoelastic parameter coefficient correction unit, based on the plastic deformation feature amount calculated by the plastic deformation feature amount calculation unit, coefficients C _R and R ₀ in the following formula 1 and coefficient C _A in the following formula 2 And B ₀ are determined, The residual stress calculation apparatus according to claim 2, wherein:
Here, in the following formulas 1 and 2, σ ₁ and σ ₂ represent main stresses remaining in the metal plate.

The residual stress calculation unit includes a sound speed ratio R and an acoustic birefringence B calculated by the acoustoelastic parameter calculation unit, and the coefficients R ₀ , C _R , B ₀ and C _A determined by the acoustoelastic parameter coefficient correction unit. The residual stress calculation device according to claim 3, wherein the main stress remaining in the metal plate is calculated based on the formula 1 and the formula 2 using   The residual stress calculation apparatus according to claim 1, wherein the plastic deformation feature amount is a plastic strain generated in the metal plate.   The residual stress calculation apparatus according to claim 1, wherein the plastic deformation feature amount is a thickness reduction ratio that is a rate of change in thickness of the metal plate accompanying plastic deformation. A sound speed measuring device that measures the speed of sound of the plurality of ultrasonic waves propagating in the metal plate by generating a plurality of ultrasonic waves in the plastically deformed metal plate;
A residual stress calculation device that calculates a residual stress in the plastically deformed metal plate using a measurement result of the sound velocity measured by the sound velocity measurement device;
With
The residual stress calculation device is:
A sound speed information acquisition unit that acquires sound speed information, which is a measurement result of a plurality of ultrasonic sound speeds propagating in the plastically deformed metal plate, from the sound speed measurement device;
A plastic deformation feature amount calculating unit that calculates a plastic deformation feature amount that is a value that can be converted into a plastic deformation amount or a plastic deformation amount of the metal plate;
Based on the sound speed information acquired by the sound speed information acquisition unit, a sound elasticity parameter, which is a parameter correlated with a main stress sum or a main stress difference, is calculated from a plurality of ultrasonic sound speeds in the metal plate. An acoustoelastic parameter calculator;
An acoustoelastic parameter coefficient correction unit that corrects a coefficient representing a change of the acoustoelastic parameter due to stress using the plastic deformation feature value calculated by the plastic deformation feature value calculating unit;
Based on the acoustoelastic parameter calculated by the acoustoelastic parameter calculating unit and the coefficient corrected by the acoustoelastic parameter coefficient correcting unit, a residual stress calculating unit that calculates the residual stress on the metal plate;
A residual stress measuring device comprising: Obtaining sound velocity information regarding a plurality of ultrasonic sound speeds in the metal plate measured by generating a plurality of ultrasonic waves in the plastically deformed metal plate;
The plastic deformation amount of the metal plate or a plastic deformation feature value that is a value that can be converted into the plastic deformation amount is calculated, and is calculated from a plurality of ultrasonic sound speeds in the metal plate based on the acquired sound speed information. Calculating an acoustoelastic parameter which is a parameter correlated with the principal stress sum or principal stress difference;
Using the calculated plastic deformation feature amount, correcting a coefficient representing a change due to stress of the acoustoelastic parameter;
Calculating a residual stress on the metal plate based on the calculated acoustoelastic parameter and the corrected coefficient;
The residual stress calculation method characterized by including. Measuring the speed of sound of the plurality of ultrasonic waves propagating through the metal plate by generating a plurality of ultrasonic waves in the plastically deformed metal plate;
Obtaining sound speed information that is a measurement result of a plurality of ultrasonic sound speeds propagating in the metal plate;
The plastic deformation amount of the metal plate or a plastic deformation feature value that is a value that can be converted into the plastic deformation amount is calculated, and is calculated from a plurality of ultrasonic sound speeds in the metal plate based on the acquired sound speed information. Calculating an acoustoelastic parameter which is a parameter correlated with the principal stress sum or principal stress difference;
Using the calculated plastic deformation feature amount, correcting a coefficient representing a change due to stress of the acoustoelastic parameter;
Calculating a residual stress on the metal plate based on the calculated acoustoelastic parameter and the corrected coefficient;
A residual stress measurement method comprising: On the computer,
A sound speed information acquisition function for acquiring sound speed information related to a plurality of ultrasonic sound speeds in a metal plate measured by generating a plurality of ultrasonic waves in a plastically deformed metal plate,
A plastic deformation feature amount calculation function for calculating a plastic deformation feature amount that is a value that can be converted into a plastic deformation amount or a plastic deformation amount of the metal plate;
Based on the sound speed information acquired by the sound speed information acquisition function, a sound elasticity parameter, which is a parameter correlated with a main stress sum or a main stress difference, is calculated from a plurality of ultrasonic sound speeds in the metal plate. A sound elasticity parameter calculation function;
Acoustoelastic parameter coefficient correction function for correcting a coefficient representing a change due to stress of the acoustoelastic parameter using the plastic deformation feature value calculated by the plastic deformation feature value calculating function;
A residual stress calculation function for calculating a stress remaining in the metal plate based on the acoustoelastic parameter calculated by the acoustoelastic parameter calculation function and the coefficient corrected by the acoustoelastic parameter coefficient correction function;
A program to realize

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