JPS6191568A - Identification of defect echo for ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To detect a true defect alone identifying echoes from a worked surface and defect echoes accurately, by making an ultrasonic pulse from a part of a plurality of probes incident into a portion looking like a defect of an object to be inspected to vary the ultrasonic wave frequency. CONSTITUTION:In an ultrasonic flow detection using a plurality of probes 3 and 5, an ultrasonic pulse from the probe 3 is made incident into a portion looking like a defect of an object 1 to be inspected and the other probe 5 is so arranged at such a position as to almost maximize the received signal considering the directivity of the reflected pulse. Then, the frequency of the ultrasonic wave made incident into a portion looking like a defect 2 of the object 1 being inspected is varied with a frequency setter 14. A corrector 10 corrects the attenuation of the distance according to the frequency of the signal received with an ultrasonic wave receiver 9 and from the relationship between the relative value of the amplitude of the received pulse with respect to the incident wave and the frequency thereof, the received pulse is judged to correspond to either a defect echo or an echo based on the shape with a memory-arithmetic unit 11 and the results are shown on a display 15 together with the amplitude, frequency and defect position.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an ultrasonic flaw detection method, and particularly to a defect echo identification method suitable for distinguishing between echoes from a machined surface of an object to be inspected and echoes from a defective surface. Regarding the method.

[Background of the invention]

As a flaw detection method that uses two or more probes, there is the delta method as shown in Ultrasonic Flaw Detection Method (published in 1974) published by Nikkan Kogyo Shimbun, pages 249 to 256.
The defect reflection shown in Figure 4 and the reflection based on the contour of the inspected object shown in Figure 5 are essentially the same, and it is very easy to distinguish between defect echoes and echoes from the machined surface. It has become difficult.

As a flaw detection method that determines defects based on the relationship between frequency and echo height, as in JP-A-52-134491, it is determined whether or not there is a defect according to the change in the peak value of the received pulse with respect to the change in frequency. Ta. However, since there is no correction method for the fact that the attenuation characteristics of the material and the amplitude of the incident pulse differ depending on the frequency, if the attenuation characteristics of the material or the amplitude of the incident pulse are highly dependent on the frequency, the wave of the received pulse The relationship between high value and frequency may become inappropriate for determining defects. In addition, since only one probe is used, if the directivity of the defective echo deviates from the direction of the probe, the received signal will be very small and accurate determination will not be possible.For example, as shown in Figure 6. If a transverse wave is incident at an angle of 60° into a defect perpendicular to the bottom surface as shown, the reflection angle will be 50'', and the reflected wave in the 60'' direction will be very small. FIG. 7 shows the relationship between the relative amplitude and frequency of the reflected wave with respect to the incident wave.

[Purpose of the invention]

An object of the present invention is to provide a defect echo identification method suitable for distinguishing between echoes from a defect and echoes from a machined surface of an object to be inspected.

[Existing necessity of the invention]

The present invention provides an ultrasonic flaw detection method using a plurality of probes, in which an ultrasonic pulse is made to enter a part of an object to be inspected that is considered to be a defect from a part of the probes, and the remaining probes The ultrasonic wave is placed at a position where the received signal is almost at its maximum considering the directivity of the reflected pulse, and the frequency of the ultrasonic wave incident on the part of the object to be inspected that is thought to be defective is changed, and the The relative value increases with frequency in the case of echoes from defects, but remains almost constant regardless of frequency in the case of echoes from machined surfaces, so it is possible to distinguish between echoes from defects and echoes from machined surfaces. It is something.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 3 shows a schematic configuration of the apparatus of this embodiment. The ultrasonic transceiver 13 is connected to the transverse wave probe 3, the distance measuring device 12, and the frequency setting device 4. The ultrasonic receiver 9 is connected to the longitudinal wave probe 5 and the distance measuring device 12. The corrector 10 is connected to an ultrasonic receiver 9, a distance measuring device 12, a frequency setting device 14, and a storage calculator 11, and a recording display 15 is connected to the storage calculator 11.

Next, the operation will be explained.

The ultrasonic transmitter/receiver 13 makes a transverse ultrasonic pulse 6 of a frequency set by a frequency setter 14 enter the defect 2 of the object 1 to be inspected via the transverse probe 3 .

The transverse wave echo 7 from the defect 2 is received by the ultrasonic transmitter/receiver 13 via the transverse wave probe 3, the delay time is measured, and the distance to the defect is determined by the distance measuring device 12. Defect 2
The longitudinal wave echo 8 generated by the mode conversion is transmitted to the probe 5.
The signal is received by the ultrasonic receiver 9 via the ultrasonic receiver 9 and output to the distance measuring device 12 to determine the distance to the defect.

The corrector 10 performs distance attenuation correction on the signal received by the ultrasonic receiver 9 according to the frequency based on distance information and frequency information, and adjusts the signal to an ultrasonic transmitter, receiver, or probe based on the frequency information. Correcting the frequency characteristics of the child, etc. is performed. In other words, by going through this processing stage, the amplitude of the received signal is affected only by the defect and one frequency characteristic is corrected to be flat, so that it is not affected by other influences. In other words, it can be considered as a relative value to the incident wave. The corrected received signal is input to the storage calculator 11 along with the distance information and frequency information, the amplitude of the received signal, the distance to the defect, and the frequency are stored, the defect position is calculated, and the relationship between frequency and amplitude is also calculated by calculation. The echoes are determined and displayed on the display 15 along with the amplitude, frequency, and defect location.

The relationship between the pulse amplitude relative value and frequency shown in Figure 1 was obtained under the flaw detection conditions shown in Figure 2, and the pulse amplitude relative value, which is the relative value of the amplitude of the reflected wave to the amplitude of the incident wave, is It can be seen that there is an increasing tendency with respect to frequency. The defect-reflected transverse wave RT in FIG.
This is what I received. As shown by the ratio of the defect size H to the wavelength λ of the incoming wave resistance on the horizontal axis of FIG. Further, it is preferable that the incident wave has a beam diameter large enough to allow the ultrasonic wave to be incident on the entire surface of the defect.

In the above embodiment, since the longitudinal wave generated by mode conversion is used as the wave to be received, the relative value of the pulse amplitude and the frequency are almost proportional to each other as shown in FIG. As explained on page 250 of the ultrasonic flaw detection method of the above-mentioned reference, there is an effect that it can also be determined that there is a plane perpendicular to the bottom surface of the object to be inspected.

〔Effect of the invention〕

According to the present invention, defect echoes and echoes from the machined surface can be accurately distinguished, so that only true defects can be accurately detected.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the frequency dependence of the relative received pulse amplitude value, Fig. 2 is a diagram showing the ultrasonic flaw detection conditions that obtained the results in Fig. 1, and Fig. 3 is a diagram showing an embodiment of the present invention. , Fig. 4 and Fig. 5 are diagrams showing the delta method, Fig. 6 is a diagram showing the ultrasonic flaw detection method considering the deviation of the reflection angle, and Fig. 7 is the relative value of received pulse amplitude in the case of Fig. 6. FIG. 2 is a diagram showing the frequency dependence of 2... Defect, 3, 4... Shear wave probe, 5... Longitudinal wave probe, 9... Ultrasonic receiver, 10... Corrector, 1
1... Memory calculator, 12... Distance measuring device, 13...
・Ultrasonic transmitter/receiver, 14... Frequency setting device, 15...
·display.

Claims (1)

[Claims] 1. In an ultrasonic flaw detection method using multiple probes, some of the probes inject ultrasonic pulses into the part of the object to be inspected that is considered to be defective, and the remaining probes emit reflected pulses. The ultrasonic wave is placed at a position where the received signal is almost at its maximum considering the directivity of the object, and the frequency of the ultrasonic wave made to be incident on the part of the object to be inspected that is considered to be defective is varied, and the amplitude of the received pulse at that time is A method for identifying a defect echo in an ultrasonic flaw detection method, comprising determining whether the received pulse is a defect echo or a shape-based echo from a relationship between a relative value thereof and a frequency.