JPS61256255A - Ultrasonic flaw detection apparatus - Google Patents

Abstract

PURPOSE:To accurately estimate the size and property of a flaw, by making a wave receiving angle independently changeable regardless of the transmitting angle of an ultrasonic wave and measuring the mode kind and intensity distribution of the plate wave reflected from a flaw. CONSTITUTION:A transmitter 11 and a receiver 12 are provided to an ultrasonic flaw detector and an ultrasonic wedge 15 is integrally provided to the transmitter. Pulse voltage is oscillated from a pulser 41 and an ultrasonic wave is transmitted to a material at an angle alpha from the transmitter 11. The ultrasonic wave 32 reflected from the flaw 22 of the material 21 s received by the receiver 12 to be sent to a receiving amplifier 2 and a display apparatus 43. At this time, the receiving angle theta of the receiver is changed to receive plate waves having different modes are received corresponding to respective angles theta. Because plate waves of all modes are measured by changing the receiving angle, a flaw reflected wave reflected in a mode different from that of transmitted plate waves can be detected and the size and property of the flaw can be accurately estimated.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an ultrasonic flaw detection device, and provides a new flaw detection device that can estimate the size of a material defect by measuring the mode conversion of a plate wave in a material defect. It is something to do.

[Background of the invention]

First, an overview of plate wave ultrasonic flaw detection will be explained.

Plate waves are one of the vibration modes of sound waves, similar to longitudinal waves (a type of vibration mode of sound waves that propagate in liquid or solid media) and transverse waves (also a type of vibration mode that can only propagate in solid media). This is a sound wave that is likely to be generated in a medium with two boundary surfaces in close proximity, that is, a thin plate-like medium, and can efficiently propagate in a direction parallel to the boundary surfaces.

Regarding its properties, refer to Nikkan Kogyosha corner ``Ultrasonic Flaw Detection Method''
It is explained in detail on pages 5 to 72, etc., but to summarize the related parts here, as shown in Figure 5, the S-1 need (symmetrical mode) and A There are two plate wave modes (obliquely symmetric mode), and each mode can be divided into So, S, and S2 depending on how to create vibration jfii (nodes) in the thickness direction of the medium, as shown in an example in Figure 6.・・・・・・Ao+
There are many higher-order vibration modes such as A, A2, etc.

Next, Figure 7 explains the method of transmitting and receiving plate waves.
Plate waves can be easily generated by making longitudinal waves obliquely incident on the surface of the sample medium using the ultrasonic shoe 15 (intermediate medium). However, the most efficient and strong plate waves can be generated under the condition that the following formula holds true.

However, α: Ultrasonic incident angle from the ultrasonic shoe to the medium Cw: Propagation speed of the longitudinal wave 30 in the ultrasonic shoe C: Propagation speed of the longitudinal wave 33 in the medium Receiving a plate wave is the same as when transmitting a wave. This is done using the same combination of ultrasonic shoes shown in FIG. 7, and the most sensitive reception is achieved when the condition of equation (1) is satisfied.

By the way, when implementing a so-called ultrasonic flaw detection device that uses this plate wave to inspect defects such as flaws in a material, the following points have conventionally been considered to be a problem.

In other words, as mentioned above, plate waves are most efficiently received at the same angle of the ultrasonic shoe as when they were generated, but in reality, when plate waves are reflected by defects etc., mode conversion (towards defects) occurs. From the mode of the incident plate wave, So, S□Is mentioned earlier
2...A o y A t tA2...
(converted to other modes such as This means that it is insufficient information regarding the size and properties of the defect.

In addition, the related technology is disclosed in Japanese Unexamined Patent Application Publication No. There are No. 124915, No. 50-122091, etc.

[Purpose of the invention]

The purpose of the present invention is to measure the mode types and intensity distribution of plate waves reflected from defects in ultrasonic flaw detection using plate waves,
An object of the present invention is to provide an ultrasonic flaw detector for plate wave flaw detection, which allows the size and properties of detected defects to be estimated from the results.

[Summary of the invention]

The conventional method of detecting material defects by propagating ultrasonic waves into the material and detecting the ultrasonic waves reflected from discontinuities in the material such as defects, does not detect defects. In a range sufficiently smaller than the width of the ultrasound beam, there is a correlation between the size and area of the defect and the strength of the ultrasound reflected from the defect, and the larger the defect, the stronger the reflected ultrasound.

However, when measuring the strength of the reflected wave 32 of the plate wave in a specific mode reflected from the slit-shaped artificial defect 22 while changing the depth d of the slit-shaped artificial defect 22 using the method shown in FIG. As shown in Figure (B), the depth of the artificial defect and the depth of the signal are not proportional. In other words, the defect size characteristic is such that the artificial defect 0, which is deeper than the 0 part in the figure, shows a minimum value. I understand. This means that not only cannot the scale (depth) of a defect be estimated from the strength of the defect signal, but also that it may not be possible to detect defects in the ω section, which is larger than the 0 section, depending on the size of the flaw detection distance Q. .

In order to find out the cause of this phenomenon, Figure 8 (B)
FIG. 9 shows an investigation of the mode distribution of the plate wave in the A and 0 parts of . In FIG. 9(A), the incident angle α of the ultrasonic wave from the wave transmitter 11 is kept constant to generate a plate wave of a specific mode (A1 mode plate wave in this figure), and this is transmitted to the ultrasonic machine 16. While continuously changing the receiving angle θ through the wave receiving element 1,
By doing this, it is possible to detect various modes of plate waves under the conditions that satisfy equation (1) where θ is replaced by α, and the mode of the plate wave generated by the wave transmitter can be detected. can be measured.

From FIG. 9(A), it can be seen that the transmitter 11 and the wedge 15 generate a plate wave mainly in the A1 mode with a strong intensity, which is accompanied by two modes, Sl and A2, although the intensity is weak. Ru.

Figure 9 (B) shows the mode distribution of the reflected plate wave 32 caused by the plate wave shown in Figure 8 (A) being reflected by a defect.
It can be seen that the A1 mode, which is the main component of the wave plate wave, is significantly weakened.

FIG. 9(C) shows the mode distribution at part 0 of FIG. 8(B), and the intensity of the A1 mode has recovered again.

From the above results, as shown in Figure 8 (B), the reason why the defect size (depth) and the reflection intensity of the plate wave are not proportional is that mode conversion occurs with the reflection of the plate wave, and the method of conversion depends on the defect size. It became clear that this was because they were different. Therefore, in plate wave flaw detection, it is insufficient to receive a plate wave in the same mode as the transmitting plate wave, and it is necessary to detect a mode with as wide a range as possible.

Going a step further, it seems possible to determine the size and type of the defect that is the reflection source by extracting the characteristics of the mode distribution of the reflector wave.

Now, when trying to measure the mode distribution of a reflector wave for the above purpose, as shown in Fig. 8(A), a wave transmitting probe (a combination of 11 and 15) and a wave receiving probe are used. (12
and 16) are arranged in front and behind each other and the receiving angle θ is changed little by little to measure the received signal, which is inevitably impractical in terms of efficiency and accuracy.

Therefore, we investigated a method to measure the plate wave mode distribution at high speed and with high precision by applying recent ultrasonic probe technology.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows an ultrasonic flaw detector with a basic configuration including a pulser 41, a receiving amplifier 42, a display device 43, and a synchronizing signal generator 44, with a transmitter 11 and a receiver 12 installed in an integrated ultrasonic wedge 15. By changing the receiving angle θ of the wave receiving element 12, it is possible to receive a plate wave in a mode determined by each θ.

There are mechanical methods and electrical methods for changing the reception angle, and the methods shown in Figs. 10 and 11. l'6 is an example using a mechanical method. In Fig. 10, the receiving angle is changed by moving the receiving element directly by hand, and in Fig. 11, the receiving angle is changed by moving the receiving element directly by hand, and in Fig. 11, the receiving angle is changed by sliding the receiving element 12 using a small electric motor 51, a pulley 52 rotated by the motor, and a link 53. It changes the angle.

In Figure 2, instead of mechanically sliding the wave receiver 12 as shown in Figure 1, a switch device [46] is used to switch between a large number of arrayed wave receiver groups and detect plate waves in modes corresponding to each wave receiver. do. If an electronic switch is used as the switch device 46, the speed can be increased.

In FIG. 3, the channel of the wave transmitter 11 is also changed, and the mode of the wave transmitter plate wave 31 can be selected from a wide range by switching the switch device 45.

FIG. 4(A) shows a configuration in which the wave transmitter group 11 and the wave receiver group 12 in FIG. and receive waves.

FIG. 4(B) shows a configuration in which a plate wave is transmitted and received using the array type ultrasonic transducer 11 and the transducers arranged in a plane by applying phase matching technology.

FIG. 4(C) explains that the ultrasonic transmission angle α can be changed arbitrarily by using the array type ultrasonic transducer 11 arranged on a plane as shown in FIG. 4(B) and the phase matching technology. be. - If the timing of exciting the wave transmitters arranged in a row with the electric pulse 40 is sequentially shifted for each wave transmitter, the wavefront of the sound wave sent out from each wave transmitter will gradually draw an arc with a different diameter. They are synthesized in certain aspects.

They emphasize each other to form a new wavefront 35 of sound waves, which propagate in the direction 36. By appropriately adjusting the above timing, the propagation direction α of the sound wave can be changed arbitrarily.

The above has been explained for the case of transmitting waves, but in the case of receiving waves, the timing of receiving waves of each wave element is sequentially shifted and the two received signals are combined, so that only sound waves at arbitrary receiving angles can be generated. can be received.

In either case, these devices are characterized in that the receiving angle θ can be changed independently regardless of the transmitting angle α, and are fundamentally different from the design concept of conventional devices.

To explain this point with reference to FIG. 4(B), in the first design concept of conventional ultrasonic flaw detection equipment, the technical concern is how to efficiently receive the transmitted ultrasonic waves. Therefore, the delay amount for each transmitting/receiving element in the transmitting delay circuit 47-1 and the receiving delay circuit 47-2 in FIG. 4(B) is designed to be completely equal, and the directivity of the transmitting wave and The directionality of the received waves was made to be equal. For this reason, the control unit 49 (usually a microcomputer is used) is often used for both the transmitting and receiving sides, and the delay circuit 47-1.47-
2 was also commonly used. In FIG. 4(B), the control units 49-1, 49-2. Delay circuit 4.7-1.4.7-2
, switching circuits 45 and 46 were written separately for the transmitting side and the receiving side, but it is possible to control both by shifting them in time, and it is of course possible to use both parts in common as in the past. be.

By the method described above, an ultrasonic flaw detection device capable of receiving plate waves of all modes independently of the transmitting plate wave is realized.

FIG. 12 shows an example in which the depth of a crack is estimated from the pattern of the intensity distribution of the received wave mode, and the type of defect is estimated from the characteristic matrix of the mode that appears.

Of course, in order to actually apply these, data must be accumulated, but once these master curves or matrix input patterns are determined, it becomes possible to determine whiteness using a computer.

〔Effect of the invention〕

According to the present invention, plate waves of all modes reflected from defects can be measured.

l) Missing detection of defective reflected waves reflected in a mode different from the wave transmitting plate wave can be prevented.

2) Information for estimating the size and properties of defects can be obtained by measuring and patterning the mode distribution of the reflector waves.

There are other effects.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of a plate wave ultrasonic flaw detection device according to an embodiment of the present invention, Fig. 2, Fig. 3, Fig. 4 (A), (B),
(C) is an explanatory diagram of the embodiment; FIGS. 5, 6, and 7 are explanatory diagrams regarding plate waves; and FIGS. 8 and 9 are mode conversions of plate waves due to defects, which are the background of the present invention. Fig. 6 is an explanatory diagram of the state in which the wave receiving angle is changed by moving the wave receiver by hand. FIG. 11 is an explanatory diagram of a state in which a wave receiving element is moved by a small electric motor to change a receiving angle. FIG. 12 is an explanatory diagram of an example used as a method for estimating the type and size of a defect. 11... Wave transmitter, 12... Wave receiver, 14... Sliding piece, 15.16... Ultrasonic model, 31... Wave transmitter plate wave,
32...Reflector wave, 33...Plate wave, 40...Electrical pulse, 4]...Pulser, 42...Preamplifier, 43...Display section, 44...Synchronization circuit , 45.46
...Switching circuit, 47-1.47-2...Delay circuit.

Claims (1)

[Claims] 1. A pulse oscillator, an ultrasonic transducer that receives the pulse voltage from the pulse oscillator and transmits or receives ultrasonic waves, and an amplifier that amplifies the signal from the ultrasonic transducer; and a display unit that displays the amplified received wave signal, the ultrasonic flaw detection device characterized in that the transmitting angle and the receiving angle of the ultrasonic waves with respect to the flaw detection surface are not equal. .