RU2397489C1 - Ultrasonic flaw detection device and ultrasonic flaw detection method - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: ultrasonic flaw detection involves steps on which an ultrasonic wave falls on a specimen through an angular sensor from an inclined direction. The diffracted wave formed at the edge of a defect on the specimen is detected through a normal sensor over the defect and the position of the edge of the defect from the front surface of the specimen is determined using a triangular method based on the beam path which is a component of the diffracted wave which propagates directly upwards and passes through the defect between the angular sensor for transmission and the normal sensor for reception, and based on the interval between the position of incidence and position for detection of the ultrasonic wave, or based on the difference between propagation time of the surface wave to the normal sensor for reception and propagation time of the beam which is a component of the diffracted wave which propagates directly over the defect to the normal sensor for reception.

EFFECT: possibility of easy and accurate determination of the position, depth and height of a defect which can be a surface crack, corroded part near the surface layer of a thick specimen and an insignificant defect.

11 cl, 13 dwg, 1 tbl, 1 ex

Description

FIELD OF THE INVENTION

The present invention relates to a method for ultrasonic inspection and device ultrasonic inspection. More specifically, the present invention relates to an ultrasonic flaw detection method and an ultrasonic flaw detection apparatus suitable for detecting a defect edge position including a surface crack, a corroded portion near the surface layer of a thick sample and a minor defect, defect depth or defect height from the back surface.

State of the art

Traditionally, an ultrasonic inspection test is carried out in order to nondestructively monitor the depth of a defect in a surface crack of a weld of a thick pipe, such as the weld of a pipe of a nuclear power plant, and the depth and position of the defect, which includes a corroded portion near the surface layer and a slight defect, height defect from the back surface, etc. With non-destructive testing of a weld of a thick pipe, the need for accurate measurement of height, depth, defect size, etc. increases, in addition to simply detecting whether or not there is a defect. When determining the size of a defect, since it is necessary to detect the edge of the defect formation and the edge of the defect completion with very high accuracy, it has recently been invented to use ultrasonic flaw detection methods, such as the phased antenna array method, the TOFD method, i.e. time-of-flight diffraction method, angular defectoscopy method, etc.

For example, a TOFD method using a surface wave is generally used to evaluate the depth of a surface crack defect (Non-Patent Document 1). As shown in FIG. 13, according to the TOFD method, a difference is formed in the paths between the path T ₀ of the surface wave beam when there is no crack, and the path T ₁ of the surface wave beam when the crack is present. Thus, after the surface wave path T ₀ when the crack is absent is previously determined and the surface wave path T ₁ when the crack is present is determined, the defect depth d is estimated from the relation shown in equation 1. The beam path means the distance on which the beam passes between the sensor on the transmission side and the sensor on the reception side

Additionally, the height of the defect can be measured using an angular inspection method using an angular sensor (Non-Patent Document 2).

Additionally, the inventors have proposed an ultrasonic measurement method called the SPOD method, i.e. a short diffraction path method that is suitable for measuring a defect at the periphery of an austenite-based stainless steel weld based on austenite and Inconel (a registered trademark of Special Metals Corporation), which are mainly used in structures inside furnaces, circulation pipes, etc. primary construction of a nuclear power plant, in particular, the height of the defect in the hole on the back surface (Non-Patent Document 3). In the SPOD method, the defect height is determined from the difference between the arrival times of the component that directly spreads over the defect and the component that spreads over the defect after it is reflected on the back surface of the sample so that the angle sensor is combined with a conventional sensor, the ultrasonic pulse is forced must be incident on the defect in the sample from an oblique direction, and the diffracted wave generated at the edge of the defect is received by means of a conventional sensor over the def ktomu.

Non-Patent Document 1. The Japanese Society for Non-Destructive Inspection, "Flaw Height Measuring Method by TOFD Method Standardized by The Japanese Society for Non-Destructive Inspection", published December 1, 2001.

Non-Patent Document 2. The Japanese Society for Non-Destructive Inspection, "Flaw Height Measuring Method by Tip Echo Techniques Standardized by The Japanese Society for Non-Destructive Inspection", published June 1, 1997.

Non-Patent Document 3. "Proposal of Simple Flaw Sizing Method in Ultrasonic Flaw Detection Test", Program & Abstracts of Second Academic Lecture of Conservation Society of Japan, pp. 21-26, distributed July 8, 2005.

SUMMARY OF THE INVENTION

Problems Resolved by the Invention

However, a surface crack is often formed in a part with a varying shape of the structure, in which the stress concentration is prone to occur, for example, through the base of a thick pipe, and a weld in which thick pipes, such as T-joints, etc. are welded to each other at an angle. It is difficult to detect a surface defect in a part with a changing shape by placing two sensors in such a way as to clamp a surface crack. Additionally, it is not possible by the TOFD method to accurately assess the defect, since the echo of the surface wave to be received is weak. Accordingly, it is difficult to detect a surface crack from the hole and determine its depth using the TOFD method. In particular, the TOFD method has a problem in that it cannot be used for austenite-based stainless steel, Inconel and the like, which are mainly used in the construction inside the furnace, circulation pipes, and the like. primary construction of a nuclear power plant, the depth of the defect of which must be measured in a non-destructive way, since the TOFD method causes a significant amount of attenuation and noise.

Additionally, even when the lower edge of the surface crack is detected by angular inspection, since the echo of the diffracted wave from the lower edge of the defect cannot be detected, the depth of the defect cannot be estimated. This is because the echo of the diffracted wave, having such a degree that it cannot be detected, cannot be obtained, since the energy of the diffracted wave in the upper inclined direction is weak, as well as scattered and attenuated due to an increase in the length of the beam path.

Additionally, when the corroded part is present in the sample, since the corroded part and the undamaged part on their periphery have the same physical properties from the beginning, and their physical properties do not change significantly, even if they are corroded, the ultrasonic wave almost completely passes through the interface between them, and thereby, the formed reflected wave and the formed diffracted wave become weak. Accordingly, since it is difficult to detect the boundary surface between the corroded part and the undamaged part by conventional ultrasonic measurement methods, such as TOFD, it is difficult to detect the presence or absence of the corroded part that did not appear on the front surface by means of non-destructive testing and additionally detect the depth of the corroded part, if she appeared on the front surface. The same is true for closed defects, in general, such as an initial fatigue crack, a closed crack, a void due to creep at the grain boundary, and fine peeling when they are visible in the sample as a group of small defects (hereinafter called a minor defect), etc. . which are much shorter than the incident wavelength. Block of minor defects, etc. can be defined as the corroded and damaged part (hereinafter referred to as the corroded part), and the traditional method of ultrasonic flaw detection cannot determine the position of the depth of the boundary surface between the corroded part and the intact part.

Additionally, it was found that when the depth of the defect from the front surface of the sample or the height of the defect from the back surface of the sample is detected, even the SPOD method, which is proposed by the inventors and disclosed in Non-Patent Document 3, does not allow to detect the signal due to attenuation, because the beam path of the diffracted wave, which spreads over the defect after it is reflected on the back surface of the sample, increases in length, although the SPOD method uses the downward component of the diffracted wave, from which the strongest energy can be obtained, wherein the above defect includes a surface crack of a thick specimen, such as a weld of a thick pipe, and a corroded portion near the surface layer. The component that propagates only downward, of the diffracted wave, which expands in an arched shape (spherical shape), is the strongest. However, in a thick sample, when the edge of the defect is too far from the back surface of the sample, for example, when the height of the defect placed next to the surface layer, the defect in the clearance of the front surface and the defect in the clearance of the back surface is too high and far from the back surface, the diffracted wave, reflected on the back surface of the sample cannot return to the sensor on the receiving side, and thus the echo reflected from the bottom surface may not be observed. Accordingly, the SPOD method, which determines the height of a defect from the difference between the time of arrival of a component that directly spreads over the defect, the diffracted wave formed on the edge of the defect, and the time of arrival of the component that spreads over the defect after it is reflected once on the back surface may not determine the surface depth of a surface crack, etc. The same thing takes place in a diffracted wave formed at the interface between the corroded part and the ordinary part, and the diffracted wave, which propagates in the corroded part and is reflected on the lower surface, cannot be detected, since it is strongly attenuated. Those. it cannot be observed in an oscilloscope.

Therefore, it is an object of the present invention to provide an ultrasonic flaw detection method and an ultrasonic flaw detection device that can simply and accurately determine the position, depth and height of the edge of a defect, which includes a surface crack, a corroded portion near the surface layer of a thick sample and a minor defect.

Problem Solver

In order to achieve the goal, as a result of various studies, the inventors found that in the components of the diffracted wave, which is formed due to the presence of a defect, the component that returns to the source of incidence is weak, the component that propagates immediately below the defect, i.e. extends to the side of the back surface, i.e. the lower surface opposing the front surface on which the ultrasonic wave is incident is the strongest, and the component that directly spreads over the defect, i.e. on the side of the front surface of the sample, is second in strength. However, in a defect in the lumen of the front surface and a defect located near the front surface of the sample, the component that extends directly above the defect is less attenuated, since its propagation distance is less than the propagation distance of the component that propagates upward after reflection on the back surface once, with the result in the form that the first component can be clearly accepted as the strongest signal. Taking into account the above fact, the inventors determined the position, depth of the defect, or height of the defect for the edge of the defect, including a crack in the front surface, a corroded part near the surface layer of a thick sample, and a minor defect using the triangle method, i.e. Pythagorean theorem, from the beam path of an ultrasonic wave that propagates directly above the defect as a diffracted wave after it reaches the defect, and the distance between the incident position and the position of detection of the ultrasonic wave on the front surface of the sample, or the difference between the propagation time to the normal sensor for receiving surface wave, which reflects the above ratio, and the propagation time to the normal sensor component of the diffracted wave, which is spread anyaetsya directly above the defect.

Those. The ultrasonic flaw detection method according to claim 1, wherein the ultrasonic wave is incident on the sample by an angular sensor from an oblique direction, a diffracted wave formed on the edge of the defect in the sample by means of a normal sensor above the defect is detected, and the position of the defect edge from the front surface of the sample is determined using the triangle method from the beam path of a component that propagates directly above the defect of the diffracted wave, and the beam path passes through the defect between the angle sensor for transmission and the normal sensor for receiving, and the interval between the position of incidence and the position of detection of the ultrasonic wave, or the difference between the propagation time of the surface wave, on which the above ratios are reflected, to the normal sensor for reception and the propagation time of the diffracted wave, which propagates immediately above the defect, to the normal sensor for reception. Since the relationship between the beam path and the propagation time is shown as “beam path = propagation time × velocity of the incident ultrasonic wave”, when the propagation time can be detected in a material in which it is believed that the ultrasonic wave has a substantially predetermined velocity, the beam path can be determined by arithmetic operations.

Further, since the ultrasonic inspection method of the present invention determines the defect edge position using a diffracted wave component propagating in the direction of the defect detection surface, the method is suitable for determining the defect depth from the front surface of the sample or the height of the defect from the back surface of the sample in a case in which it is difficult to detect component of the diffracted wave, which propagates to the position of the edge of the defect, which includes a surface crack, the part near the surface layer of a thick sample and a slight defect also spreads under the defect (the surface on the opposite side for the surface onto which the ultrasonic wave is incident) and propagates upward after being reflected on the back surface once. When the defect is a minor defect, the beam path or the difference between propagation times is determined by instructing the incidence of the ultrasonic wave having a large amplitude as an ultrasonic wave and detecting the harmonic wave component of the diffracted wave that propagates directly upward from the minor defect. Additionally, when the lower surface on which the diffracted wave is reflected is far from the edge of the defect, as with a defect near the surface layer of the sample or a defect in the lumen of the front surface, as in the weld of a thick pipe, and when the height of the defect in the lumen of the back surface is too far , the height of the defect from the back surface can be determined from the difference between the thickness of the sample, measured by the method of ultrasonic inspection, and its thickness, measured by another method.

Additionally, the interval between the incident position and the detection position of the ultrasonic wave can be detected, for example, from the propagation time of the surface wave, the interval between the angular sensor for transmission and the normal sensor for reception can be measured, or the incidence position and the detection position of the sound wave on the front side the surface of the sample can be maintained up to a predetermined interval.

Additionally, a piezoelectric vibrator and a magnetostrictive generator are usually used as a source for generating ultrasonic waves, acting as an angular sensor, the ultrasonic wave can be excited by a laser depending on the application. According to the method of laser ultrasonic waves, since the ultrasonic wave is excited in a non-contact manner, it is preferable for measuring in a high temperature medium and measuring a sample having a complex shape and the like, and is further preferable when the defect height is estimated from the ratio of the propagation times of the surface wave and the diffracted wave , which propagates over the defect, because there is a received signal of a strong surface wave, in comparison with the method of ultrasonic defect FDI using a piezoelectric element. Here, when the laser is used as an angle sensor, the interferometer is preferably used as a normal sensor for reception. Additionally, in the method of laser ultrasonic waves, it is preferable that the laser consisted of a plurality of lasers, and the time delay is applied to the lasers by means of a delay generator in order to shift the laser irradiation intervals so that the generated ultrasonic waves reach an arbitrary single point simultaneously, thereby controlling the propagation direction .

Additionally, the ultrasonic inspection device according to the present invention includes an angular sensor for transmitting to cause an ultrasonic wave to fall on a defect in a sample from an oblique direction, a normal sensor for receiving to receive a diffracted wave propagating over the defect, and an arithmetic module for calculating the position of the edge of the defect from the front surface of the sample using the triangle method from the interval between the beam path of a component that propagates directly above the defect of the diffracted wave, which is received by the normal sensor for reception and is formed on the edge of the defect, the beam path passing through the defect between the angular sensor for transmission and the normal sensor for reception, and the position of incidence and the position of detection of the ultrasonic wave, or from the difference between the time the propagation of a surface wave to a normal sensor for reception and the propagation time of the component of the diffracted wave directly propagating over the defect to normal Atchik for reception.

Advantage of the invention

According to the ultrasonic inspection method and the ultrasonic inspection device of the present invention, since the component of the diffracted wave, the intensity of which follows the intensity of the component of the diffracted wave propagating in the direction immediately below the defect, and which has the shortest path of the beam, is directly received without passing through the prism, it is very unlikely that the component of the diffracted wave will be affected by attenuation, and it can be accepted as the strongest signal. Consequently, even an unprepared flaw detectorist can accurately measure a defect without a scatter in the measured results.

Further, according to the ultrasonic inspection method and the ultrasonic inspection device of the present invention, even when the damage and the like. is located near the surface layer of the sample, the position from the front surface of the sample to the edge of the defect can be determined. Accordingly, the presence or absence of a defect near the surface layer or the position of the defect from the front surface or the back surface of the sample, in particular, the depth of the surface defect, the depth of the corroded defect from the front surface, or the presence or absence of a closed defect near the surface layer and its position may be defined, and additionally the height of the lumen of the back surface, etc. can also be determined from a known sample thickness determined by another measurement method.

Moreover, according to the ultrasonic inspection method and the ultrasonic inspection device of the present invention, the position of the edge of the defect can be simply calculated. Those. it is possible to evaluate the depth of the defect on the front surface of the sample without affecting the material and changing the shape of the measurement surface.

According to the ultrasonic inspection method and ultrasonic inspection device of the present invention, since it is possible to detect a defect in a sample, such as a bubble in a weld, the characteristics of the product can be evaluated by preliminary measuring their initial defects.

According to the ultrasonic inspection method and the ultrasonic inspection device of the present invention according to claim 4, since a diffracted wave component is used that has the shortest distance, the intensity of which corresponds to the intensity of the diffracted wave component propagating directly to the normal sensor, and which propagates directly under the defect, even weak reflection source, such as the interface between the undamaged part and the corroded hour Strongly in a sample can receive the diffracted wave at the level and intensity that can be detected. Accordingly, the position of the interface between the corroded part and the undamaged part can also be determined using another measurement method and visual assessment, and in addition, the depth of the corroded part from the front surface of the sample or the height of the corroded part from its back surface can be determined.

Additionally, according to the ultrasonic inspection method and the ultrasonic inspection device of the present invention according to claim 5, since the diffracted wave component that propagates up the shortest path of the beam is directly received without passing through the prism, a harmonic component having a higher frequency can be adopted, since it is unlikely that it will be affected by attenuation. Those. since the frequency of the ultrasonic wave for detection can be increased to a greater extent than the traditional one, it has a high resolution for detection, and a more minor defect can be detected.

Brief Description of the Drawings

FIG. 1 is an explanatory view of a defectoscopy method and an assessment of the depth of defects according to the ultrasonic inspection method of the present invention.

FIG. 2 is a view showing an example of received waveforms of a surface wave and a diffracted wave when a defect depth is estimated.

FIG. 3 is a view for explaining a defectoscopy method and evaluating the depth of defects according to the ultrasonic flaw detection method of the present invention.

4 is an explanatory view illustrating an example of an ultrasonic inspection device for exciting an ultrasonic wave by a laser.

5 is an explanatory view illustrating an example of an ultrasonic inspection device using a piezoelectric vibrator.

6 is an explanatory view of an example embodiment in which a defect in a sample is detected.

7 is a view for explaining the principle of detecting an interface of a corroded portion of a back surface in a sample.

Fig. 8 is a graph illustrating an example of a received waveform in the detection method of Fig. 7, in which the vertical axis shows the displacement, and the transverse axis shows the path of the beam.

9 is a view illustrating a principle for detecting an interface of a corroded portion of a front surface in a sample.

Fig. 10 is a graph illustrating an example of a received waveform in the detection method of Fig. 9, in which the vertical axis shows the displacement, and the transverse axis shows the path of the beam.

11 is an explanatory view showing a method for detecting an edge of a defect in a sample when moving a position to which the excitation laser is emitted in a state where the sensor on the receiving side is fixed above the slit.

12 is an explanatory view showing a method of detecting an edge of a defect in a sample controlled by simultaneously moving the sensor for reception and the position to which the excitation laser is emitted, with a constant interval between the sensor and the position being maintained.

13 is a view for explaining a method of defect depth for a surface crack by a conventional TOFD method.

Explanation of Reference Numbers

1 - device ultrasonic inspection

2 - laser

3 - delay generator

6 - sample

7 - interferometer

8 - laser detection

12 - personal computer

13 - front surface of the sample

14 - back surface of the sample

15 - surface wave

16 - ultrasonic wave incident on the sample

17 - diffracted wave

18 - diffracted wave propagating up

21 - angle sensor for transmission

22 - normal sensor for reception

25 - corroded part

26 - intact part

27 - the interface between the corroded part and the intact part

Optimum Mode for Carrying Out the Invention

The structure of the present invention will now be described in detail based on the embodiment shown in the drawings.

The ultrasonic flaw detection method of the present invention causes an ultrasonic wave to fall onto the sample by means of an angular sensor from an oblique direction, detects a diffracted wave generated at the edge of the defect in the sample by means of a normal sensor above the defect, and determines the position of the edge of the defect from the front surface of the sample using the triangle path method beam component of the diffracted wave, which propagates directly upward and passes through the defect between the angular sensor for transmission and the normal sensor for reception, and the interval between the position of incidence and the position of detection of the ultrasonic wave, or from the difference between the propagation time of the surface wave, on which the above ratios are reflected, to the normal sensor for reception and the propagation time of the component of the diffracted wave, which propagates directly above defective, to a normal sensor for reception.

The ratio shown in expression 2 is established between the path of the beam and the propagation time.

Thus, when the propagation time can be detected in a material in which it is believed that the ultrasonic wave has a practically predetermined speed, the beam path Wt can be determined by arithmetic operation. Additionally, as shown in FIG. 1, the component 18, which propagates directly above the diffracted wave 17, formed on the edge of the defect 20, and the surface wave 15, which propagates on the front surface 13 of the sample 6 from the point of incidence of the ultrasonic wave in the direction of the normal sensor for receiving (detection position), has the ratio of a right triangle with respect to the beam 16, which reaches the defect 20 from the point of incidence. From what is described above, it is possible to determine the distance from the edge of the defect to the front surface or the back surface of the sample, i.e. the depth or height of the defect, which includes a surface crack, a corroded portion near the surface layer of a thick sample, and a minor defect using the triangle method, from the difference between the propagation time of the surface wave 15 propagating along the front surface 13 of the sample and the propagation time of the ultrasonic wave 16 , which propagates in sample 6, and to form a diffracted wave 17 in the defect 20, or from the paths of the rays of the corresponding waves. Since the propagation distance of the component that propagates directly above the defect, the diffracted wave is shorter to a depth to the defect, it is less scattered and attenuated, thereby the diffracted wave can be accurately detected.

Here, it is preferable to use a longitudinal wave as a reception wave. This is because it is unlikely that a longitudinal structure is affected by the metal structure due to its significant wavelength in addition to the fact that it reaches the sensor faster than the shear wave. However, the wave used for detection is not limited to a longitudinal wave, and a shear wave can be used. A normal sensor for reception may also receive a shear wave in addition to a longitudinal wave. Experiments have confirmed that both waves have very high accuracy and excellent fault tolerance. Accordingly, since the shear wave can be stronger depending on the position of detection, the defect can be clearly detected using either or both of the longitudinal wave and the shear wave, from which the optimal detection result can be obtained.

Although a piezoelectric vibrator and a magnetostrictive generator are typically used as an angle sensor for transmission in an ultrasonic inspection method and apparatus, a laser can also be used depending on the situation. When an ultrasonic wave is excited by a laser, since the ultrasonic wave is excited in a non-contact manner, the laser is preferably used for measurement in a high temperature environment, for measuring a sample having a complex shape, and the like. Additionally, the inventors have found that when an ultrasonic wave excited by a laser is used, a received signal having a strong surface wave is present in comparison with a case where an ultrasonic wave is incident by a piezoelectric element. As a result, since there is a received signal having a strong surface wave in comparison with the method of ultrasonic inspection using a piezoelectric element, it is preferable for determining the depth of the defect from the front surface of the sample or the height of the defect from the back surface of the sample using the triangle method, and the defect includes a surface crack, a corroded part near the surface layer of a thick sample, and a slight defect. Needless to say, a conventional angle sensor for transmission and a normal normal sensor for reception using a piezoelectric vibrator, magnetostrictive generator, etc. allow you to easily detect a defect. Those. any of the method of laser ultrasonic waves and the method of ultrasonic flaw detection using a piezoelectric element allows you to accurately detect the depth of the defect.

When a laser is used as an angular sensor for transmission, it is effective and preferable to use an interferometer as a normal sensor to receive when a diffracted wave is detected and to detect a defect in a non-contact way using an interferometer. When the ultrasonic vibration propagating in the sample reaches its front surface, the point of arrival vibrates at a slight displacement in nm or less. Thus, when a laser beam is emitted to a position in which ultrasonic wave detection is required, a slight transformation of the light frequency is formed, i.e. Doppler shift, in reflected light. When the frequency and phase of the laser beam are sufficiently stable, a slight transformation of the frequency of light can be measured using the interference effect. Note that when a laser is used as an angle sensor, an interferometer is usually used as a normal sensor for reception. However, when the defect can be detected in the contact state, the piezoelectric element and magnetostrictive generator can be used as a normal sensor for reception.

Further, when an ultrasonic wave is excited by laser radiation into a sample, it is preferable to control the propagation direction with a plurality of lasers 2 and by applying a time delay such that a longitudinal wave or a shear wave of all of the ultrasonic waves that are generated by a time shift in which the respective lasers 2 are emitted, through a delay generator 3, reaches an arbitrary one point at a time, as shown in FIG. 4. In this case, ultrasonic waves, sequentially excited by the corresponding laser beams 9, which are emitted into the sample 6, are synthesized, whereby an ultrasound wave having a large amplitude can be generated. With this operation, a defect can be accurately detected with good sensitivity. Additionally, the propagation direction of the excited wave can be controlled by transmitting laser beams 9 for excitation from the respective lasers 2 at different times and generating an ultrasonic wave. For example, when the time delay is set equal to a small value, the angle of incidence of the synthesized wave can be reduced, and when the time delay is set to a large value, the angle of incidence of the synthesized wave can be increased. Thus, the angle of incidence of the rays can be controlled by controlling the time lag. Additionally, an ultrasonic wave having a narrow band in which energy is concentrated near the natural frequency can be generated by controlling the order of arrival of the waves excited by the plurality of lasers 2 and integrating the wave.

A YAG laser having Q switching, a CO ₂ laser, an excimer laser, and the like. can be used as lasers 2 on the transmission side in an embodiment. Next, the laser pulses are created with time delay by setting the time delay of the Q-switching of the respective lasers 2 on the transmission side by means of a delay generator 3 relative to the trigger signal 8 for detection. Additionally, although it is preferable to use, for example, a mixed interferometer with two light waves as interferometer 7, it is not limited to this, and other known or new interferometers, for example, Fabry-Perot interferometer (CFPI), can be used. Additionally, a personal computer 12, which collects data and acts as a controller, is connected to the interferometer 7 through an oscilloscope 11 and a band-pass filter 10. The signal detected by the interferometer 7 is recorded by an oscilloscope 11 through a band-pass filter 10 and is additionally input into a computer 12. The computer 12 includes a central processor (not shown), a program for pre-setting the operating procedure of the central processor, a memory device for storing data, and the like, processing accessed by the central processor, a means of a storage device for storing input data, a display means, an input means such as a keyboard and a mouse, and constructs a function corresponding to a flaw detector, together with an oscilloscope 11 and a band-pass filter 10. Note that the links with numbers 4a, 4b in the drawings, they mean mirrors, and reference number 5 indicates a capacitor lens. The band-pass filter 10 is, for example, a low-pass band-pass filter, and is used to remove noise and the like.

According to an ultrasonic inspection device arranged as described above, the process of applying a time delay so that the ultrasonic waves reach an arbitrary one point at a time can be executed by, for example, simple monitoring of the oscilloscope 11. In particular, first the waveform, excited by an arbitrarily selected laser 2, is detected and registered on the screen of the oscilloscope 11. Next, the remaining lasers 2 are sequentially excited one by one, and the margin yvanie time is set for 2 lasers when viewed on an oscilloscope forms resulting signal 11 so that the resulting waveforms agree with the peak waveforms registered to them. Needless to say, time lag can be predefined by calculation using the triangle method. Additionally, the time delay of the laser can be predefined for each parameter, for example, the thickness of the sample 6, the material, the interval between the positions of the radiation.

Further, when a sensor using a piezoelectric element is used, the ultrasonic inspection method of the present invention can be carried out by means of a device having the structure shown, for example, in FIG. 5. The ultrasonic inspection device has an angular sensor 21 for transmitting to cause the ultrasonic wave to fall onto sample 6, a normal sensor 22 for receiving to receive a diffracted wave propagating over the defect in sample 6, and a personal computer 12 that collects and acts as a controller and controls the operation transmitting and receiving operation of the sensor 21 for transmitting and the sensor 22 for receiving by means of a pulse receiving device 23 connected to it through the card 24 analog-to-digital conversion.

The computer 12, which performs the control operation and receives the data, makes up the function corresponding to the flaw detector using the analog-to-digital conversion board 24 and the pulse receiving device 23. There is no need to say that the flaw detector can be used separately, and the computer 12 only collects data. Additionally, the computer 12 exclusively sets the scanning condition and controls the scanning when a defect is detected.

Note that in any of the methods, the computer 12 calculates the position of the edge of the defect 20 from the front surface 13 of the sample 6 using the central processor using the triangle method from the entire path Wt of the beam of the incident ultrasonic wave 16 passing through the defect 20 between the angular sensor 21 for transmission and the normal sensor 22 for receiving a component which directly propagates above a flaw of a diffracted wave 17, and the interval between the position s and the position of incidence of the ultrasonic wave is detected, or from the difference _(t t -t _s) in between TERM propagation of the incident ultrasonic wave 16 which is incident on the defect 20 reaches the flaw 20 and directly propagates above the flaw 20 as a diffracted wave, and the propagation time of the surface wave in the sample 15. At the same time, the difference between the time of arrival to the surface of the flaw detector is shown by simultaneously displaying the surface wave 15 of the ultrasound beam and the signal of the component 18, which propagates directly above the defect, of the diffracted wave 17, which is formed when the component 18 reaches the edge of the defect 20, on the oscilloscope 11 in as a means of display.

1 illustrates an explanatory view of an embodiment in which an ultrasonic inspection method is applied to measuring a defect depth for a surface crack. Note that the embodiment is explained with respect to the case where the laser is used as a sensor on the transmission side, and the interferometer and the laser for detection are used as a normal sensor for reception.

ультразвуковой волны заданы равными предварительно определенным значениям, центр ультразвукового луча, который расширяется в дугообразной форме, не всегда достигает оконечности дефекта 20. Тем не менее, даже если часть луча от его центра достигает оконечности дефекта 20, формируется дифрагированная волна, и тем самым оконечность дефекта 20 может быть обнаружена. Дополнительно, позиция излучения лазерного света 9 для возбуждения может быть просканирована.In an embodiment, it is assumed that the position of the emission of laser light 9 for excitation and the position of the emission of laser light 8 for detection are moved in the same direction by one amount while maintaining a predetermined interval between them. In this case, the signal can only be obtained by jointly moving the position of the emission of laser light 9 for excitation and the position of the emission of laser light 8 for detection, no time is taken to select the fixation position of one of the sensors. Accordingly, when the radiation position of the laser light 8 for detection becomes above the surface crack 20, a diffracted wave is detected from the lower edge of the defect 20. By this operation, even a surface crack can be detected that cannot be visually distinguished. Note that there is no need to say that when the position of the surface crack 20 is known in advance, the position of the radiation of the laser 8 for detection can be determined as the position of the surface crack. When the interval S between the position of incidence and position of detection of ultrasonic waves and the angle of incidence

ultrasonic waves are set equal to predetermined values, the center of the ultrasonic beam, which expands in an arc shape, does not always reach the tip of the defect 20. Nevertheless, even if a part of the beam from its center reaches the tip of the defect 20, a diffracted wave is formed, and thereby the tip of the defect 20 can be detected. Additionally, the position of the emission of laser light 9 for excitation can be scanned.

When an ultrasonic wave is incident, the normal pickup sensor 22 first detects a surface wave 15 having a short beam path after the time t _{s has} passed, and then detects an incident ultrasonic wave that propagates directly above the defect as a diffracted wave through defect 20, and has a beam path Wt after the time t _t passes, as shown in FIG. When the speed of sound is shown by C, the trajectory Ws of the beam of the surface wave 15 and the entire trajectory Wt of the beam of the ultrasonic wave in sample 6 are shown as Ws = Ct _s , Wt = Ct _t by the relation of the expression 2 described above. From what is described above, the defect depth d for the surface crack 20 can be obtained from expression 3 derived from the Pythagorean theorem. Note that the interval S between the radiation position of the laser light 9 for excitation and between the radiation position of the laser light 8 for detection, i.e. the surface wave path Ws of the surface wave may be calculated from the propagation time of the surface wave 15, or the interval may be predefined to a predetermined value, or may actually be measured each time a defect is detected. Additionally, the speed C of sound depends on the material of the sample and can be determined previously:

Next, figure 3 shows the principle when the height d of the defect of the back surface of a thick sample is determined. An ultrasonic wave 16, the propagation direction of which in sample 6 is controlled by time delays set equal to the set of lasers 2 of the ultrasonic inspection device 1 shown in FIG. 4, propagates to the defect 20 through the beam path W _t1 and is further diffracted at the edge of the defect 20 and forms diffracted wave 17. The component 18 of the diffracted wave 17, which propagates directly above the defect 20, propagates directly to the front surface 13 of the sample 6 through the path uw W _t2 beam. At the same time, the longitudinal surface wave 15 propagates to the area near the front surface of the sample 6 in the beam path Ws.

Expressions 4, 5 shown below are given from the arrival times t _s , t _t of the surface wave 15 and the diffracted wave 18, which propagates above the incident ultrasonic wave 16

Additionally, W _t2 can be determined from expression 6, and the defect height d can be determined by subtracting W _t2 from the thickness T of sample 6. Note that the thickness T of sample 6 can be measured by simply a thickness gauge or the like. Thus, even if the reflection of the diffracted wave 17 from the back surface 14 cannot be detected when the distance W _t2 from the edge of the defect in the lumen of the back surface to the front surface 13 of the sample can be determined, the height d of the defect 20 from the back surface of the sample can be determined:

Additionally, in the ultrasonic inspection method of the present invention, the presence of the edge of the closed defect in the sample, for example, a closed spherical defect, such as a bubble formed in the weld, which was traditionally difficult to detect, can also be detected similarly and the position of the depth of damage can be estimated from the front surface of the defect sample. In particular, as shown in FIG. 6, the ultrasonic inspection method of the present invention is useful when the defect 20 is present near the surface layer of the sample 6, or when a diffracted wave (not shown) that propagates to the side of the front surface of the sample 6, i.e. . extends upward after it is reflected once on the back surface 20 of sample 6, cannot be accepted, since the defect in the lumen of the back surface has a large height.

Those. the position from the front surface 13 of the sample to the edge of the defect 20 can be determined by the method described above. In contrast, then, whether the defect 20 is an open defect or a closed defect can be easily distinguished by the ultrasonic inspection method of the present invention in conjunction with another ultrasonic inspection method. When, for example, an angular inspection method is used, since a strong reflected wave from the lumen is received as an echo of the lumen, whether or not defect 20 is a closed defect can be determined by the presence or absence of an echo of the lumen. Accordingly, it is possible to determine the position d by the height of the defect 20 having a spherical inner part, such as a bubble, from the bottom surface, the detection of which is difficult with the traditional ultrasonic inspection method, by combining the ultrasonic measurement method of the present invention and the angular inspection method.

Additionally, when an ultrasonic wave that has a large amplitude that is at least five to ten times greater than the amplitude of the ultrasonic wave (of the order of 1 nm) used in a conventional flaw detection test, is used instead of the above ultrasonic wave, a slight defect that exists the sample may be closed, and since the wave partially passes through the stretching phase of the ultrasonic wave, a harmonic component is formed for the diffracted wave 17 (non-linear property of the diffracted wave). Accordingly, the normal sensor 22 for receiving receives a diffracted wave including a harmonic component. For example, when an ultrasonic wave having a frequency of 5 MHz is incident, the normal sensor 22 for receiving receives a second-order harmonic wave of 10 MHz. In this way, it can be determined whether or not there is a minor defect in the sample, i.e. a minor defect can be detected depending on whether the harmonic component is included in the received diffracted wave 18. Additionally, the position of the minor defect 20 from the front surface of the sample can be estimated from the difference between the arrival times of the diffracted wave 18, which propagates directly upward from the minor defect 20 , and the arrival time of the surface wave 15. In this case, since an ultrasonic wave having a large amplitude can detect more insignificant ny defect because the ultrasonic wave has a higher frequency, it is preferable to use an ultrasonic wave having a higher frequency in a range in which the normal sensor may receive an ultrasonic wave.

An ultrasonic wave having a large amplitude has a greater attenuation than a conventional ultrasonic wave. Thus, when the ultrasonic wave has a large propagation distance because it is diffused and attenuated, a harmonic component having a signal level that can be received by a normal sensor for reception cannot be detected. However, in the present invention, when the diffracted wave 18, which propagates directly upward from the tip of the defect 20, i.e. propagates to a normal sensor 22 for reception, is received directly by a normal sensor 22 for reception without a prism, a diffracted wave 18 can be received while maintaining a strong signal and minimize attenuation. Accordingly, when a true conventional prism is used, a normal sensor for receiving can receive a second-order harmonic wave having 16 MHz at maximum.

Note that when there is an intention to detect only whether or not a minor defect 20 exists, a normal sensor 22 needs to receive at least only the diffracted wave 18 and its harmonic component for reception.

Additionally, the ultrasonic inspection method of the present invention can also be applied when an interface 27 is detected between the undamaged part 26 and the corroded part 25 in sample 6. For example, as shown in FIG. 7, the interface 27 can be detected with minimal attenuation by calling the incidence of the ultrasonic wave 16 from the angular sensor 21 for transmitting and capturing a weak diffracted wave 18, which propagates upward from the interface 27 of the diffracted wave 17, forming located on the section surface 27 in a short beam path. Note that in an ultrasonic inspection method, an ultrasonic wave having a normal amplitude can be used, or an ultrasonic wave having a large amplitude can be used in order to use a non-linear ultrasonic wave as an incident wave 16. Additionally, when minor defects form in the sample as group, the position of the group can be defined as the corroded and damaged part (hereinafter referred to as the corroded part).

When the waveform is observed when scanning the angle sensor 21 for transmission in the direction of the arrow in the drawing with the normal receiving sensor 22 fixed on the corroded portion 25, the received waveform, as shown in FIG. 8, can be obtained if the interface 27 is present. The bias peak 28 shows the diffracted wave 18 from the interface 27, and the continuous bias after the peak 28 shows the scattered wave 29 from the back surface 14. Note that although it is assumed in the embodiment that the angular sensor 21 for transmission and the normal sensor 22 for reception move By maintaining a predetermined interval between them, the interval between two sensors can be measured each time it is required. Note that, as shown in FIG. 8, when the scattered wave 29 appears after peak 28, it can be confirmed that the corroded portion is present on the back surface.

In contrast to when the corroded portion 25 is present on the surface layer of the sample 6, as shown in FIG. 9, the received waveform, as shown in FIG. 10, is provided, and the depth T _{1 of the} interface 27 can be determined by the triangle method, as described above. Here, when there is surface corrosion, the scattered wave 29 is first received from the interface 27, and then the peak 28 of the diffracted wave 18 from the interface 27 is received. Accordingly, then, corrosion is the corrosion of the front surface formed on the front surface, or the corrosion of the back surface formed on the back surface, can be determined depending on what first appears from the scattered wave 29 and peak 28.

Note that the embodiment described above is the preferred embodiment, the present invention is not limited to this and can be modified in various ways and implemented within the scope, which does not depart from the essence of the present invention. For example, an electromagnetic ultrasonic sensor (EMAT) that applies Lorentz force can be used as a sensor. Additionally, when an ultrasonic wave is excited in the direction of the sample by a laser, a defect can be detected by installing sample 6 in water (immersion method in water).

Additionally, although it is most preferable to place the normal sensor 22 for reception directly above the defect 20, it is not limited exactly to the position directly above the defect, and the position of the normal sensor 22 can be appropriately shifted within the range in which the diffracted wave 18 propagating directly above the defect 20, can be taken according to the situation.

Further, when the defect detection surface on which the sensors 21, 22 are placed has an irregular part, for example, a weld bulge, a deformed surface, an unpolished part, and the like, a sensor, in particular a normal receiving sensor 22 that does not use a prism, not in direct contact with the defect detection surface. Therefore, it is preferable to use a sensor that has flexibility with respect to a defect detection surface. As the flexible sensor 7, for example, a soft sensor made in Japan Probe and the like can be used.

Additionally, it is also possible to perform transmission and reception in a state where a water vessel is placed around either or both of the sensors for transmission and reception, and they are immersed in water. Note that the partial immersion method in water can also be used by means of a sensor on the transmission side by changing its angle in water.

Examples

Example 1

An experiment was conducted in order to confirm whether or not the ultrasonic inspection method of the present invention is useful. In this experiment, an aluminum sample 6 was used, having a polished front surface, 40 mm wide, 80 mm long, and 20 mm thick. Note that in the experiment in the sample 6, instead of defects, slots 20 are formed having a width of 0.5 mm and a height of 2 mm, 5 mm, and 8 mm. In an experiment, an ultrasonic wave is excited with a simple laser. Note that the angle of incidence of the longitudinal ultrasonic wave is controlled as 45 °.

Since sample 6 has a thickness of 20 mm, slots cannot be detected by a laser for detection. To deal with this problem, a normal receiving sensor 22 is used, consisting of a piezoelectric element having a base frequency of 5 MHz and a diameter of 8 mm.

Scanning is performed by two scanning methods, as shown in Figs. 11 and 12. As shown in Fig. 11, one of the methods is such that the normal sensor 22 for receiving is initially placed constantly above the slit 20, and the position of the emission of laser light 9 for excitation on the transmission side moved. As shown in FIG. 12, another method is such that a predetermined interval S is set between the respective positions of the radiation of the normal sensor 22 for receiving and the laser light 9 for excitation, and the laser light 9 for excitation and the normal sensor 22 for receiving are moved together simultaneously one size in one direction. Note that x indicates the distance between the laser radiation position and the slit 20 when scanning is started, and S shows the distance between the laser radiation position and the position of the sensor 22 for reception. Note that the scan was performed in increments of 1 mm. Additionally, the arrow indicated by reference number 30 indicates the direction of scanning.

The table illustrates the results of flaw detection. In a flaw detection method using a surface wave and an upper diffracted wave, when the gap 20 is 2 mm or 5 mm in height, no error occurs, and even if the gap 20 is 8 mm in height, the error is only 0.4 mm (5% error ), from which it can be confirmed that the defect height can be measured with high accuracy. As described above, according to the ultrasonic inspection method of the present invention, it can be confirmed that the accuracy of measuring the height of the defect can be improved.

Slit Length (mm) The method of using the surface wave and the upper diffracted wave Measurement Result (mm) Error (mm) 2.0 2.0 0,0 5,0 5,0 0,0 8.0 8.4 0.4

Claims (11)

1. The method of ultrasonic inspection, containing the stages at which
cause the ultrasonic wave to fall on the sample by means of an angular sensor from an inclined direction;
detecting a diffracted wave formed at the edge of the defect in the sample by means of a normal sensor above the defect; and
determine the position of the edge of the defect from the front surface of the sample using the triangle method from the beam path of the component of the diffracted wave, which propagates directly upward and passes through the defect between the angular sensor for transmission and the normal sensor for reception, and the interval between the position of incidence and the position of detection of an ultrasonic wave, or from the difference between the propagation time of a surface wave to a normal sensor for reception and the propagation time of a diffracted wave component nd extends directly above the defect, the normal probe for reception. 2. The ultrasonic inspection method according to claim 1, wherein the defect is a surface crack and the defect depth from the front surface of the sample is determined. 3. The ultrasonic inspection method according to claim 1, wherein the defect is damage in the sample, and the position of the depth of damage from the front surface of the sample is determined. 4. The ultrasonic inspection method according to claim 1, wherein the defect is the corroded part, and the depth or height of interference between the undamaged part and the corroded part in the sample from the front surface or back surface of the sample is determined. 5. The ultrasonic inspection method according to claim 1, wherein the defect is minor damage, the ultrasound having a large amplitude drops as an ultrasonic wave, and the beam path or propagation time of the diffracted wave component is determined by detecting a harmonic component of the diffracted wave that propagates directly upward from minor defect. 6. The method of ultrasonic inspection according to claim 1, additionally containing stages, in which
detecting a surface wave propagating along the front surface of the sample, and a diffracted wave component scattered upward from the edge of the defect;
determining the position of the edge of the defect from the front surface of the sample from the difference between the propagation time of the surface wave and the propagation time of the component of the diffracted wave using the triangle method; and
determine the height of the defect in the lumen to the back surface or the defect in the sample from the back surface based on the difference from the thickness of the sample. 7. The ultrasonic inspection method according to claim 1, wherein the interval between the position of the incidence of the ultrasonic wave and the position of detection of the ultrasonic wave is detected from the propagation time of the surface wave. 8. The method of ultrasonic inspection according to claim 1, in which the interval between the position of the incidence of the ultrasonic wave and the position of detection of the ultrasonic wave is predefined and maintained equal to a predetermined interval. 9. The ultrasonic inspection method according to claim 1, wherein the angle sensor is a laser. 10. The ultrasonic inspection method according to claim 9, in which the laser consists of many lasers, and the time delay is used so that the generated ultrasonic waves simultaneously reach an arbitrary single point by shifting the intervals of the laser radiation through the delay generator, thereby controlling the propagation direction. 11. An ultrasonic inspection device containing
an angular sensor for transmitting to cause an ultrasound beam to fall on a defect in the sample from an oblique direction;
a normal reception sensor for receiving a diffracted wave propagating over a defect; and
arithmetic module for calculating the position of the edge of the defect from the front surface of the sample using the triangle method from the beam path of the component that propagates directly above the defect, a diffracted wave, which is received by a normal sensor for reception and is formed on the edge of the defect, and the beam path passes through the defect between an angular sensor for transmitting and a normal sensor for receiving, and the interval between the position of incidence and the position of detection of an ultrasonic wave, or from p connectivity between the time of propagation of a surface wave probe to the normal to the reception propagation time and the diffracted wave component, directly propagates above the flaw, the normal sensor for reception.

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