JP2016176884A - Ultrasonic thickness measurement method and apparatus, and defect position detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately measure the thickness of a subject in which crystal grains constituting a metal crystal structure have a statistical variation and the crystal orientation is unclear.SOLUTION: A method for detecting the thickness and defect position of a subject using an ultrasonic wave comprises: a step (S107) of setting the root-mean-square sound velocity; a step (S104) of propagating a vertically polarized transverse wave and a horizontally polarized transverse wave in a subject, and measuring the propagation time of the vertically polarized transverse wave and the horizontally polarized transverse wave; a step (S106) of propagating the longitudinal ultrasonic wave in the subject and measuring the longitudinal wave propagation time; a step (S108) of calculating the effective propagation time from the vertically polarized transverse wave propagation time, the horizontally polarized transverse wave propagation time and the longitudinal wave propagation time; and a step (S109) of calculating the thickness and defect position of the subject from the root-mean-square sound velocity and the effective propagation time.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic thickness measurement method and apparatus, and a defect position detection method.

  An ultrasonic thickness measuring method using longitudinal or transverse ultrasonic waves is known for measuring the thickness and dimensions of metallic materials. Transmits pulsed longitudinal or transverse sound waves from the surface of the subject to the inside of the subject, receives the reflected wave reflected from the bottom surface of the subject, and the propagation time at this time or the propagation time difference between multiple reflected waves , And the ultrasonic propagation distance is calculated by multiplying the propagation time of the thickness of the subject and the speed of sound, and the thickness is measured.

  If the crystal structure of the metal material of the subject is uniform, the sound velocity of the ultrasonic wave has a substantially constant value regardless of the propagation direction. A material having such characteristics is called an isotropic material, and the thickness of an isotropic material can be measured with high accuracy by the above method.

  On the other hand, when the crystal structure is non-uniform, the sound velocity of the ultrasonic waves takes different values depending on the propagation direction. For example, in the case of an austenitic material such as stainless steel or nickel-base alloy, the crystal grains are cubic single crystals and solidify while the crystal orientation is aligned in a specific direction during the cooling process. This direction is called the crystal growth direction. Since the crystal structure is composed of a plurality of crystal grains, the crystal growth direction is oriented to a specific orientation as an average value, and the crystal orientation is random in each crystal grain in the direction orthogonal to the crystal growth direction. It is known to turn.

  Therefore, when measuring the thickness of a specimen consisting of a solidified structure such as a casting or a welded portion, the crystal orientation is random in the plate thickness direction, and the ultrasonic sound velocity depends on the propagation direction of ultrasonic waves due to acoustic anisotropy. Therefore, accurate thickness measurement becomes difficult.

  Further, when measuring the thickness of a specimen having a texture such as a rolled material, the sound velocity of the ultrasonic wave takes different values depending on the state of the texture and the propagation direction. Thereby, accurate thickness measurement becomes difficult.

  On the other hand, there is also known a method in which an effective sound velocity value is measured in advance by using a calibration test body having a crystal orientation equivalent to that of the subject, and the thickness is measured. However, since the crystal orientation is random, it is difficult to reproduce the sound speed of the subject by the calibration specimen.

  As a background art of this technical field, there is Patent Document 1. In this publication, two ultrasonic probes for transmission and reception are opposed in parallel to the crystal growth direction, the crystal orientation direction of the subject, and the installation surface on which the two ultrasonic probes are installed In a plane formed by a direction orthogonal to the normal direction of the installation surface, the longitudinal wave ultrasonic wave is propagated in an oblique direction in a range of 30 degrees to 60 degrees with respect to the normal direction of the installation surface, There is a description of an ultrasonic thickness measurement method that uses the maximum and minimum average sound velocities of longitudinal wave propagating in the direction of 45 degrees with respect to the crystal orientation direction.

JP 2012-053027 A

  However, since the crystal orientation and texture of the crystal grains have statistical variations, the difference between the assumed sound speed and the actual sound speed is large in a subject with large anisotropy. There is a problem that it cannot be measured. In order to perform measurement with high accuracy, it is necessary to measure in advance the crystal orientation of the crystal grains constituting the subject. For example, it is necessary to measure the crystal orientation in advance by observing a cross section of the subject. However, when such a measurement is performed, there arises a problem that a simple measurement cannot be performed, for example, the measurement time is greatly increased.

  In the thickness measurement method described in Patent Document 1 described above, the maximum and minimum average sound velocities of the longitudinal wave propagating in the direction of 45 degrees with respect to the crystal orientation direction are used, and the crystal orientation (perpendicular to the crystal growth direction) is used. With regard to the component), the thickness can be easily measured by measuring the average propagation time, focusing on the propagation time of the ultrasonic wave propagating in an oblique direction that is not easily affected by statistical randomness. However, since the average sound speed is selected as the representative value as the sound speed, when the crystal orientation is unknown, the sound speed greatly varies from the average value, and there is a problem that accurate measurement is difficult. In addition, there is a problem that it is necessary to prepare a calibration specimen whose crystal orientation is known in advance.

  Therefore, the present invention has been made in view of the above problems, and even in a subject in which the crystal grains constituting the metal crystal structure have statistical variations and the crystal orientation is unknown, An object of the present invention is to provide an ultrasonic thickness measuring method and apparatus and a defect position detecting method for measuring the thickness with high accuracy.

  In order to achieve the above object, the present invention relates to a method for detecting the thickness and defect position of an object using ultrasonic waves, a step of setting a root mean square sound velocity, a vertical polarization transverse wave, and a horizontal polarization transverse wave. To the subject and measure the propagation time of each of the vertically polarized wave and the horizontally polarized wave, to propagate the longitudinal ultrasonic wave to the subject and measure the longitudinal wave propagation time, and the vertical The step of calculating the effective propagation time from the polarization transverse wave propagation time, the horizontal polarization transverse wave propagation time and the longitudinal wave propagation time, and the thickness and defect position of the subject are calculated from the root mean square sound velocity and the effective propagation time. It is characterized by that.

  According to the present invention, it is possible to easily and accurately measure a thickness and a defect position even in a specimen in which crystal grains constituting a metal crystal structure have statistical variations and the crystal orientation is unknown. it can.

3 is a flowchart illustrating a procedure of an ultrasonic thickness measuring method according to the first embodiment. It is a conceptual diagram which shows the principle of ultrasonic thickness measurement. It is a conceptual diagram which shows the relationship between the crystal orientation of the single crystal test object made into a measuring object, and an ultrasonic propagation direction. It is a conceptual diagram which shows the relationship between the ultrasonic wave propagation direction and sound velocity of the single crystal test object made into a measuring object. It is a conceptual diagram which shows the relationship between the crystal orientation of the welding part of the test object made into a measuring object, and an ultrasonic propagation direction. It is a conceptual diagram which shows the relationship between the ultrasonic wave propagation direction of the welding part of the subject made into a measuring object, and a sound speed. 1 is a block diagram illustrating an overall configuration of an ultrasonic thickness measuring apparatus according to Embodiment 1. FIG. It is a block diagram which shows the detailed structure of the ultrasonic thickness measuring apparatus of Example 1. 6 is a flowchart illustrating a procedure of a sound speed setting method according to the second embodiment. 10 is a flowchart illustrating a procedure of a sound speed setting method according to the third embodiment. It is a block diagram which shows the detailed structure of the ultrasonic defect position detection apparatus of Example 4.

  Hereinafter, examples will be described with reference to the drawings.

  Hereinafter, the flaw detection apparatus according to the first embodiment will be described with reference to FIGS.

  First, the ultrasonic thickness measurement method used in the embodiment will be briefly described with reference to FIG. FIG. 2 is an explanatory diagram of an ultrasonic thickness measuring apparatus using a conventional ultrasonic thickness measuring method. The ultrasonic thickness measurement apparatus converts the voltage into a physical force by the ultrasonic probe 104 and transmits / receives an ultrasonic wave to / from the subject 106. In the ultrasonic mode, both a longitudinal wave that vibrates in the same direction as the propagation direction and a transverse wave that vibrates in a direction perpendicular to the propagation direction are used. The ultrasonic probe 104 is in contact with the subject 106 through the delay material 105. The object 106 is made of an acoustic anisotropic material whose crystal orientation 114 is unknown. The delay material 105 is a synthetic resin block such as polystyrene, and is used to obtain a reflected wave 107 from the surface of the subject 106. The ultrasonic probe 104 and the delay material 105 and the delay material 105 and the subject 106 are brought into contact with each other through a contact medium, respectively. When the surface of the subject is not flattened, the shape of the delay material 105 may be processed into a curved surface, for example, in order to improve the contact with the subject. The ultrasonic transceiver 101 includes a pulsar 102 and a receiver 103.

  The ultrasonic wave is transmitted in a direction perpendicular to the surface of the subject 106, and a reflected wave 107 reflected on the surface of the subject 106 and a reflected wave 108 reflected on the bottom surface are generated. The reflected ultrasonic wave is converted again into an electric signal by the ultrasonic probe 104. The received electrical signal is received by the receiver 103 of the ultrasonic transceiver 101 and displayed as a waveform signal on the display 109. Here, the waveform signal 110 is the waveform of the reflected wave 107 from the surface of the subject, and the waveform signal 111 is the waveform of the reflected wave 108 from the bottom surface of the subject. The thickness 113 can be evaluated by measuring the time difference 109 propagated through the subject 106 from these waveform signals 110 and 111 and multiplying the ultrasonic sound speed by the time difference 109.

  With reference to FIG. 3 and FIG. 4, the sound velocity of the ultrasonic wave propagating through the subject as the inspection object of the ultrasonic inspection method according to the first embodiment will be described.

  The acoustic anisotropy material that is the object is a single crystal material, a unidirectional solidified material composed of a plurality of crystal grains having a specific crystal orientation such as, for example, a build-up weld or a cast product, and the rolling process. For example, a polycrystalline body having a rolling texture in which micro crystals are formed with statistical variations. The unidirectional solidified material can be handled as a rotationally symmetric model with a specific crystal orientation as the rotation center. The rolling texture can be handled as an orthorhombic model whose main axis is the rolling direction and the orthogonal direction of rolling.

  The speed of sound of ultrasonic waves can be theoretically handled by the eigenvalue equation called the Christoffel equation from the density of the subject, the 6 × 6 component matrix c called elastic stiffness and the ultrasonic wave propagation direction.

  As with the isotropic material, the acoustic anisotropy material is assumed to have a certain sound speed, and when the thickness 113 is measured using longitudinal or transverse waves, the assumed sound speed is different from the actual sound speed, and the thickness measurement accuracy is different. Decreases.

  The speed of sound of the ultrasonic wave propagating through the cubic single crystal 201 will be described with reference to FIG. FIG. 3A shows a model of the ultrasonic wave 202 propagating through the cubic single crystal 201. For example, FIG. 3B shows an example in which the speed of sound in pure iron which is a cubic crystal 201 material is calculated using the Christoffel equation. When the direction of the cubic crystal, for example, <100> is the crystal orientation, and the angle 115 between the crystal orientation and the ultrasonic wave propagation direction is θ, the longitudinal wave velocity 204 and the transverse wave velocity (vertically polarized transverse wave velocity 205, horizontally polarized transverse wave). The speed of sound 206) varies depending on θ. Further, the transverse ultrasonic wave propagates separately into a vertically polarized transverse wave and a horizontally polarized transverse wave, and shows different vertically polarized transverse wave sound velocity 205 and horizontally polarized transverse wave sound velocity 206, respectively.

  In the pure iron illustrated in FIG. 3B, when the crystal orientation of the specimen is random or unknown, the thickness 113 is measured assuming the average sound speed as the sound speed of the cubic crystal. An error of about ± 8.0% occurs when a vertically polarized transverse wave is used, and an error of about ± 21.7% occurs when a horizontally polarized wave is used.

  Further, the speed of sound of ultrasonic waves propagating in the unidirectional solidified material 301 composed of a plurality of crystal grains solidified while aligning with a certain crystal orientation will be described with reference to FIG. FIG. 4A shows a model of the ultrasonic wave 302 that propagates in the unidirectional solidified material 301. For example, FIG. 4B shows an example in which the sound speed of a welded portion in stainless steel, which is a unidirectional solidified material 301, is calculated using the Christoffel equation. Assuming that the crystal growth direction is the crystal orientation and the angle 115 formed between the crystal orientation and the ultrasonic wave propagation direction is θ, as in the case of the cubic Chang single crystal described with reference to FIG. The polarization shear wave velocity 305 and the horizontal polarization shear wave velocity 306) vary depending on θ.

  In the unidirectional solidified material of stainless steel illustrated in FIG. 4B, when the crystal orientation of the specimen is random or unknown, the thickness 113 is measured assuming the average sound velocity as the sound velocity of the unidirectional solidified material. When using waves, the maximum error is about ± 7.0%. When using vertically polarized transverse waves, the maximum error is about ± 18.0%. When using horizontally polarized transverse waves, the maximum error is about ± 8.7%. Arise.

  Similarly to the above example, for specimens having a rolled texture, if the formation state of the rolled texture is unknown, the longitudinal and transverse wave velocities change, so the sound speed of the isotropic material is taken as the average sound speed. Measuring thickness decreases accuracy.

  For this reason, even if the average sound speed is used as the representative value of the sound speed, it is difficult to ensure the thickness measurement accuracy and accurately measure the thickness 113. However, since the thickness measurement using ultrasonic waves is calculated by multiplying the ultrasonic sound speed by the propagation time 112, the thickness 113 cannot be determined unless the representative value of the sound speed can be determined. In addition, since the subject 106 has randomness, in order to obtain a significant average sound velocity value, it is necessary to perform measurement at a plurality of locations with a plurality of calibration specimens, and the thickness cannot be easily determined. .

  Therefore, in this embodiment, the thickness is measured using the root mean square sound speed calculated from three kinds of sound speeds of longitudinal wave speed, vertical polarization transverse wave speed, and horizontal polarization shear wave speed as the sound speed value. As shown in FIGS. 3 (B) and 4 (B), for example, the root mean square sound velocities 207 and 307 of a single crystal of pure iron and a unidirectional solidified material of stainless steel have crystal orientations and ultrasonic propagation directions. It is not affected by the angle θ formed. Similarly, for the rolling texture, the root mean square sound velocity is a constant value independent of the crystal orientation. In order to calculate the thickness 113, an effective propagation time in which the thickness can be calculated by multiplying by the root mean square sound speed is used. The effective propagation time is not affected by the angle θ between the crystal orientation and the ultrasonic wave propagation direction.

  As described above, the root mean square sound velocity and the effective propagation time corresponding thereto are not easily affected by the change in the angle 115 formed by the ultrasonic wave propagation direction and the crystal orientation, so that the crystal grains constituting the metal crystal structure are statistical. Even for a specimen 106 that has a general variation and whose crystal orientation is unknown, the thickness can be measured easily and accurately.

  The ultrasonic thickness measuring apparatus according to the first embodiment will be described with reference to FIGS.

  FIG. 5 is an explanatory diagram of the overall configuration of the ultrasonic thickness measuring apparatus according to this embodiment. The ultrasonic probe 104 propagates longitudinal waves and transverse waves in the subject through the same propagation path. The ultrasonic transmitter / receiver has a vibration direction rotating mechanism 407 for rotating the vibration direction of the transverse wave transmitted / received from the ultrasonic probe. In order to measure the longitudinal wave propagation time, the vertical polarization transverse wave propagation time, and the horizontal polarization transverse wave propagation time, the longitudinal wave propagation time measuring device 402, the vertical polarization transverse wave propagation time measuring device 403, and the horizontal polarization transverse wave propagation time measuring device. 404 is provided. The display 109 includes a longitudinal wave display 109A that displays the measurement result of the longitudinal wave and a transverse wave display 109B that displays the measurement result of the transverse wave. For each of the longitudinal wave and the transverse wave, the longitudinal wave signal 110A and the transverse wave signal 110B corresponding to the reflected wave 107 from the surface of the subject 106, and the longitudinal wave signal 111A and the vertical polarization corresponding to the reflected wave 108 from the bottom surface of the subject 106 are detected. A transverse wave signal 111B and a horizontally polarized wave signal 111C are displayed. The thickness measuring apparatus 401 includes a database 405 that holds the root mean square sound speed for each material.

  The thickness calculator 406 includes a longitudinal wave propagation time measuring unit 402, a vertical polarization transverse wave propagation time measuring unit 403, a vertical polarization transverse wave propagation time measuring unit 404, and a vertical polarization transverse wave propagation time 112 B. The thickness 113 is calculated from the horizontal polarization transverse wave propagation time 112C and the root mean square sound velocity. However, the example shown in FIG. 5 does not limit the embodiment of the present invention. 2 and 5, the same reference numerals indicate the same parts.

FIG. 6 is an explanatory diagram of a detailed configuration of the vibration direction rotating mechanism of the ultrasonic transmitter / receiver of the ultrasonic thickness measuring apparatus according to the present embodiment. In the longitudinal wave amplitude setting unit 501 and the transverse wave amplitude setting unit 502, voltage values to be applied to the ultrasonic probe 104 for generating longitudinal waves and transverse waves are set. In the rotation angle setting unit 503, a rotation angle φ representing the transverse wave vibration direction is set. The ultrasonic probe 104 includes piezoelectric elements 104A, 104B, and 104C that generate longitudinal waves and transverse waves that vibrate in two orthogonal directions. The pulsar 102A generates a voltage based on the voltage value set by the longitudinal wave amplitude setting unit 501 and applies it to the longitudinal wave piezoelectric element 104A. Based on the rotation angle φ set by the rotation angle setting unit 503, the voltage value set by the transverse wave amplitude setting unit 402 is converted into a voltage value by the multipliers 504A and 504B that multiply cos φ and sin φ, and is sent to the pulser 102B and the pulser 102C. It is done. The pulsar 102B and the pulsar 102C generate a voltage based on the received voltage value and apply it to the transverse-wave piezoelectric elements 104B and 104C. Transmission and reception of the longitudinal wave and the transverse wave may be performed at different timings or simultaneously. The piezoelectric elements 104A, 104B, 104C that have received the reflected waves 107, 108 send the converted electrical signals to the receivers 103A, 103B, 103C. The longitudinal wave receiver 103A sends the received signal to the longitudinal wave display 109A. The transverse wave receiver 109B and the transverse wave receiver 109C send the received signals RB and RC to the transverse wave waveform calculation unit 505. The transverse wave waveform calculation unit 505 calculates (RB ² + RC ² ) ^1/2 and sends it to the transverse wave display 109B. The display device 109 displays the received signal on, for example, a liquid crystal display. However, the example shown in FIG. 6 does not limit the embodiment of the present invention. For example, the ultrasonic probe may be replaced with a dedicated ultrasonic probe for each longitudinal wave and transverse wave measurement, or an ultrasonic probe having a vibration direction in one direction is used for the transverse wave vibration direction. However, the ultrasonic probe itself may be rotated mechanically.

  Next, the operation procedure of the ultrasonic thickness measuring method according to this embodiment will be described with reference to FIG. First, of the transverse waves, the vibration directions of the vertically polarized wave and the horizontally polarized wave are obtained. In step S101, transverse wave ultrasonic waves are transmitted / received from the ultrasonic probe 104. The longitudinal wave amplitude is set to a voltage value sufficient for the reflected wave 108 from the bottom surface of the subject 106 to reach the ultrasonic probe 104 and be displayed on the display 109 with a sufficient peak value. The vibration direction is set to φ = 0 degrees.

  In step S102, the transverse wave propagation time is measured using the reflected wave signal displayed on the display 109. At this time, when the transverse wave vibration direction does not coincide with the vibration direction of the vertically polarized wave or the horizontally polarized wave, the reflected wave signals 111B and 111C are mixed and displayed on the display. The propagation time 112B and the horizontal polarization transverse wave propagation time 112C cannot be measured with high accuracy.

  Therefore, in step S103, the rotation angle φ is changed. Returning to step 104 again, the transverse wave is transmitted and received. When this step is repeated, if the time interval between the reflected wave signals 111B and 111C is large and separated, either 111B or 111C signal disappears and only 111B or 111C is displayed. The Φ at this time is the vibration direction of the vertically polarized wave or the horizontally polarized wave. That is, it can be determined as a direction that matches the crystal orientation of the object to be inspected. Further, for example, when the thickness of the object to be inspected is thin or the difference in sound speed between the vertically polarized wave and the horizontally polarized wave is small, the time interval between the reflected wave signals 111B and 111C is small, and the signals are mixed and observed. The case where it is done is considered. In such a case, it can be considered that the case where only one of 111B and 111C is displayed when the propagation time becomes maximum or minimum corresponds to the crystal orientation. Φ at this time is the vibration direction of the vertically polarized wave or the horizontally polarized wave. In the following description, it is assumed that the transverse wave at the rotation angle φ is a vertically polarized transverse wave. The procedure is the same when the rotation angle φ is a horizontally polarized transverse wave.

  In step S104, φ obtained in the above step is set in the rotation angle setting unit, the transverse wave is transmitted / received, the propagation time 112B of the vertically polarized transverse wave is measured, and held by the vertical transverse wave propagation time measuring device 403. Subsequently, φ + 90 degrees is set in the rotation angle setting unit, the transverse wave is transmitted and received, the propagation time 112B of the horizontally polarized transverse wave is measured, and the horizontal transverse wave propagation time measuring unit 404 holds it.

  Next, the longitudinal wave propagation time is measured using the reflected wave signal displayed on the display 109. In step S105, longitudinal wave ultrasonic waves are transmitted and received, and the received signal is displayed on the display 109. The longitudinal wave propagation time 112 </ b> A is measured and held by the longitudinal wave propagation time measuring device 402.

In step S107, the root mean square sound speed is set. Specify the material and read and set the root mean square sound velocity from the database. In step S108, the longitudinal wave propagation time T _L , the vertical polarization transverse wave propagation time T _S1 , the horizontal polarization transverse wave held by the longitudinal wave propagation time measuring device 402, the vertical transverse wave propagation time measuring device 403, and the horizontal transverse wave propagation time measuring device 404. From the propagation time T _S2 , the effective propagation time T _RMS is
It calculates using the relationship of (Formula 1).

Finally, in step S109, from the above-specified root mean square sound velocity V _RMS and the calculated effective propagation time T _RMS ,
The thickness L is calculated as (Formula 2). The calculated thickness is displayed on the display 109.

  By measuring the root mean square sound velocity and the corresponding effective propagation time in this way, the crystal orientation varies statistically, and even in a specimen where the crystal orientation is unknown, the thickness can be easily and accurately measured. Can be measured.

  Steps 101 to 103 may be used as necessary and are not essential steps. Without performing steps 101 to 103, the propagation time and the horizontal transverse wave propagation time of the vertically polarized wave of step 104 are directly measured (in this case, the rotation operation of 90 degrees is unnecessary), and the longitudinal wave propagation obtained separately is obtained. Even if the effective propagation time is calculated using time, the effect is obtained. By performing steps 101 to 103, the propagation time can be observed by separating the vertical polarization transverse wave and the horizontal polarization transverse wave propagation, so that an improvement in accuracy can be expected.

  Next, a thickness measuring method according to the second embodiment will be described with reference to FIG.

  FIG. 7 is a flowchart for explaining a method of setting the root mean square sound speed according to the second embodiment. In the second embodiment, the root mean square sound speed is calculated using a calibration specimen having a known thickness in place of the method of specifying from the database for the root mean square sound speed setting step S107 shown in FIG. 1 in the first embodiment. It is what you do. In the setting of the root mean square sound speed in the present embodiment, the steps up to the calculation of the effective propagation time shown in the first embodiment can be used in the same manner. Therefore, in the flowchart of FIG. 7, the description of the components having the same functions as those in FIG.

  In step S201, the thickness L of the calibration specimen is set. For example, the calibration specimen is cut out from the same material as the subject 106 and created. The crystal orientation of the calibration specimen itself may have statistical variations and the crystal orientation may be unknown.

Next, in step S202, the root mean square sound velocity V _RMS is calculated using the set thickness L and the effective propagation time T _RMS calculated in step S108, and is set in the ultrasonic thickness measuring apparatus. The root mean square sound speed is
It can be calculated from (Formula 3). In order to calculate the root mean square sound speed with higher accuracy, the mean square root sound speed may be obtained and averaged twice or more using a plurality of calibration specimens having different thicknesses.

  Using the root mean square set in the above procedure, the thickness can be measured according to the flowchart of FIG.

  In this way, by measuring the root mean square sound velocity measured by the calibration test specimen and the corresponding effective propagation time, the crystal orientation of the calibration test specimen itself and the crystal grains calibrating the specimen have statistical variations. Even when the crystal orientation is unknown, the thickness can be measured easily and accurately.

  Next, a thickness measurement method according to Example 3 will be described with reference to FIG.

  FIG. 8 is a flowchart illustrating a method of setting the root mean square sound speed according to the third embodiment. In the third embodiment, the root mean square sound speed is calculated using the density and elastic stiffness of the object in place of the method of specifying from the database in the root mean square sound speed setting step S107 shown in FIG. 1 in the first embodiment. It is what you do.

  In step S301, the density ρ of the subject is set.

In step S302, the elasticity stiffness of the subject is designated. Elastic stiffness is a symmetric matrix with 6 × 6 elements, so it has 21 independent components. However, in the case of a single crystal of cubic metal having high symmetry, the root mean square sound velocity can be calculated simply by specifying the two components c ₁₁ and c ₄₄ . In addition, even when the crystal structure of the specimen is made of cubic metal, such as a cast product that is a set of unidirectional solidified material or coarse crystal grains such as a welded part, the single crystal constituting the structure two components c ₁₁ and c ₄₄ need only specify. Even when the specimen has a rolling texture, it is only necessary to specify the two components c ₁₁ and c ₄₄ when the crystal grains are completely random and can be considered isotropic.

In step S303, the root mean square sound velocity V _RMS is calculated from the density ρ and the elastic stiffness components c ₁₁ and c _44.
It is calculated from the relationship of (Formula 4).

  Using the root mean square set in the above procedure, the thickness can be measured according to the flowchart of FIG.

However, the method described here is not the only method for calculating the root mean square sound speed by specifying the density and the elastic stiffness. For example, by calculating all the independent components of elastic stiffness and solving the Christoffel equation, the longitudinal wave velocity V _L , the vertical polarization transverse wave velocity V _S1 , and the horizontal polarization transverse wave velocity V _S2 are calculated and squared. Average square root velocity V _RMS
You may use the method calculated from the relationship of (Formula 5).

  As described above, by measuring the root mean square sound speed calculated using the density and elastic stiffness of the specimen and the effective propagation time corresponding to it, the crystal orientation of the calibration specimen itself and the crystal grain calibrating the specimen can be statistically measured. Even when the crystal orientation is unknown and the crystal orientation is unknown, the thickness can be measured easily and accurately.

  Next, the defect position measuring method according to the fourth embodiment will be described with reference to FIG.

  The thickness measurement methods described in the first to third embodiments can be applied as long as the object to be measured is not only the thickness of the subject but can reflect ultrasonic waves. For example, the positions of the defects 607 and void defects shown in FIG. 9 can be obtained with high accuracy.

  The fourth embodiment is greatly different in that the ultrasonic thickness measurement device 401 in the first embodiment is an ultrasonic defect position detection device 601 and the defect position calculator 406 is a defect position calculator 606.

  Similar to the thickness measurement method described in the first to third embodiments, the measurement of the root mean square sound velocity and the effective propagation time from the corresponding defect makes it possible to calibrate the calibration test specimen itself or the specimen. Even when the orientation has statistical variations and the crystal orientation is unknown, the defect position can be detected easily and accurately. That is, the defect position 608 can be obtained.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 101 Ultrasonic transmitter / receiver 102 Pulsar 103 Receiver 104 Ultrasonic probe 105 Delay material 106 Subject 107 Reflected wave 108 from subject surface Reflected wave 109 from subject bottom surface Display 110 Corresponding to reflected wave from subject surface Signal 111 corresponding to the reflected wave from the bottom surface of the object 112 Propagation time of the ultrasonic wave reciprocating through the object 113 Thickness of the object 114 Crystal orientation 115 of the object The crystal orientation of the object and the ultrasonic propagation direction Angle 201 Cubic Chang Single Crystal Model 202 Propagation Direction of Ultrasonic Waves Propagating Cubic Chang Single Crystal 204 Longitudinal Sound Velocity 205 in Pure Iron Horizontally Polarized Transverse Wave Velocity 206 in Pure Iron Vertically Polarized Transverse Wave Velocity 207 in Pure Iron Root mean square sound velocity 301 in pure iron 301 Model of unidirectional solidified material 302 Propagation direction of ultrasonic wave propagating in unidirectional solidified material 304 Longitudinal of stainless steel weld Sonic velocity 305 Horizontally polarized shear wave velocity 306 of stainless steel weld 306 Vertically polarized shear wave velocity 307 of stainless steel weld zone Root mean square sound velocity 401 of stainless steel weld zone 401 Ultrasonic thickness measuring device 402 Longitudinal wave propagation time measuring device 403 Vertical transverse wave propagation time measurement Unit 404 horizontal shear wave propagation time measuring unit 405 root mean square sound velocity database 406 thickness calculator 407 vibration direction rotating mechanism 501 longitudinal wave amplitude setting unit 502 transverse wave amplitude setting unit 503 rotation angle setting unit 505 transverse wave waveform calculating unit 601 ultrasonic defect Position detection device 606 Defect position calculator 607 Defect 608 Defect position S101 to S109 Calculation step of ultrasonic thickness measurement S207 Execution step of sound velocity calibration using calibration specimen S301 to S303 Execution step of sound velocity calculation based on density and elastic stiffness

Claims (7)

In an ultrasonic thickness measurement method that measures the thickness of a subject using ultrasonic waves,
Setting a root mean square sound velocity;
Propagating a vertically polarized wave and a horizontally polarized wave to a subject, and measuring a propagation time of each of the vertically polarized wave and the horizontally polarized wave;
Propagating longitudinal ultrasonic waves to the subject and measuring longitudinal wave propagation time;
Calculating an effective propagation time from the vertical polarization transverse wave propagation time, the horizontal polarization transverse wave propagation time and the longitudinal wave propagation time;
An ultrasonic thickness measurement method for calculating a thickness of a subject from the root mean square sound velocity and the effective propagation time. In the ultrasonic thickness measuring method of Claim 1,
Rotating the vibration direction of the transverse wave to propagate the transverse wave ultrasonic wave to the subject, and measuring the vibration direction of each of the vertically polarized wave and the horizontally polarized wave of the subject;
An ultrasonic thickness measurement method comprising a step of propagating a vertically polarized wave and a horizontally polarized wave to a subject based on the vibration direction and measuring a propagation time of each of the vertically polarized wave and the horizontally polarized wave. In the ultrasonic thickness measuring method according to claim 1 or 2,
The step of setting the root mean square sound velocity is a step of calculating a mean square root sound velocity V _RMS from a longitudinal wave sound velocity V _L , a vertical polarization transverse wave velocity V _S1, and a horizontal polarization transverse wave velocity V _S2 that propagates through the subject.
The step of calculating and setting from the relationship of: and the step of calculating the effective propagation time include the longitudinal wave propagation time T _L propagating in the subject, the vertical polarization transverse wave propagation time T _S1 and the horizontal polarization transverse wave. Effective propagation time T _RMS is _calculated from propagation time T _S2.
A step of calculating from the relationship of
From the root mean square sound velocity V _RMS and the effective propagation time T _RMS ,
As an ultrasonic thickness measurement method for calculating the plate thickness L. In the ultrasonic thickness measuring method according to any one of claims 1 to 3,
The step of setting the root mean square sound speed comprises:
Using a calibration test specimen made of the same material composition as the subject, rotating the transverse wave vibration direction to propagate the transverse wave ultrasonic wave to the object, and measuring each vibration direction of the vertically polarized wave and horizontally polarized wave When,
Based on the vibration direction, propagating a vertically polarized wave and a horizontally polarized wave to a calibration specimen, and measuring a propagation time of the vertically polarized wave and a horizontally polarized wave:
Propagating longitudinal ultrasonic waves to the object and measuring longitudinal wave propagation time;
Calculating an effective propagation time from the vertical polarization transverse wave propagation time, the horizontal polarization transverse wave propagation time and the longitudinal wave propagation time;
An ultrasonic thickness measurement method for calculating a root mean square sound speed from the thickness of the calibration test specimen and the effective propagation time. In the ultrasonic thickness measuring method according to any one of claims 1 to 3,
The step of setting the root mean square sound speed comprises:
Setting the density of the subject;
Setting elastic stiffness of a single crystal model of crystal grains constituting the crystal structure of the specimen;
An ultrasonic thickness measurement method for calculating a root mean square sound velocity from the density and the elastic stiffness. In an ultrasonic thickness measurement device that measures the thickness of a subject using ultrasonic waves,
An ultrasound probe that transmits and receives longitudinal and transverse ultrasonic waves into the subject; and
A pulsar for driving the ultrasonic probe;
A receiver that receives the longitudinal and transverse ultrasonic waves;
A vibration direction rotation mechanism that rotates the vibration direction of the transverse wave ultrasonic wave;
A database holding values of root mean square sound speed,
A longitudinal wave propagation time measuring device for measuring the propagation time of longitudinal ultrasonic waves;
A transverse wave propagation time measuring device for measuring the propagation time of the transverse wave ultrasonic wave,
An effective propagation time calculator that calculates an effective propagation time based on the propagation time measured by the longitudinal wave propagation time measuring device and the transverse wave propagation time measuring device;
A thickness calculator that calculates the thickness of the subject based on the root mean square sound velocity value stored in the database and the effective propagation time calculated by the effective propagation time calculator;
An ultrasonic thickness measuring device comprising: a display for displaying the value of the root mean square sound velocity and the thickness. In the defect position detection method for detecting the defect position of the subject using ultrasonic waves,
Setting a root mean square sound velocity;
Propagating the vertically polarized wave and the horizontally polarized wave to the subject, measuring the propagation time of the vertically polarized wave and the horizontally polarized wave from the defect,
Propagating longitudinal ultrasonic waves to the subject and measuring the longitudinal wave propagation time from the defect;
Calculating an effective propagation time from the vertical polarization transverse wave propagation time, the horizontal polarization transverse wave propagation time and the longitudinal wave propagation time;
A defect position detection method for detecting a defect position of a subject from the root mean square sound velocity and the effective propagation time.