JPH01250056A - Ultrasonic flaw detecting method - Google Patents

Abstract

PURPOSE:To evaluate a defect in a body to be inspected and to improve the accuracy of defect detection by sending an ultrasonic wave to the flaw detection surface of the body from a contactor and performs flaw detection, detecting the crest value of the reflected wave from an ultrasonic wave reflector, and evaluating the defect in the body. CONSTITUTION:The ultrasonic wave reflector 6 is arranged on both opposite flaw detection sides of the thin body 2 at a distance l from the body 2. If there is the defect 3 or a discontinuous layer, etc., in the body 2, a layer of air is present at this part to decrease the transmissivity of the ultrasonic wave 5 or cut off the ultrasonic wave 5 completely. The crest value of the reflected wave from the reflector 6 decreases or becomes zero. This is observed through a cathode-ray tube oscillograph connected to a probe 4 to evaluate the defect in the body 2. Consequently, the defect detection accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic flaw detection method that attempts to detect defects existing inside an object to be inspected by utilizing reflection or attenuation of ultrasonic waves.

[Conventional technology]

There are two well-known ultrasonic flaw detection methods that utilize physical properties unique to ultrasonic waves to detect defects inside an object to be inspected: a reflection method and a transmission method.

FIG. 3 is a diagram showing ultrasonic hot water sampling using the reflection method. As shown in the figure, a probe 4 is placed above the test object 2 immersed in water 1.
At the same time, ultrasonic waves 5 are emitted from the transmitting/receiving surface of the probe 4 toward the testing surface of the object to be inspected 2, reflected by the object to be inspected 2, and returned to the transmitting/receiving surface of the probe 4. By observing the state of reflection with a cathode ray tube oscillograph connected to the probe 4, a defect 3 existing inside the object to be inspected 2 is detected.

In addition, in ultrasonic inspection using the transmission method, a transmitting probe that transmits ultrasonic waves and a receiving probe that receives transmitted waves are placed opposite each other with the object to be inspected sandwiched between them. By transmitting ultrasonic waves from the child toward the testing surface of the object to be inspected, passing through the inside of the object, and reaching the receiving object, the ultrasonic waves are transmitted to the inside of the object to be inspected. Detect existing defects.

[Problem to be solved by the invention]

By the way, the conventional ultrasonic flaw detection method described above has the following problems. In other words, in the reflection method, as shown in Fig. 4, the Brown-G oscillograph not only captures the reflected waves from defects in the object to be inspected, but also the flaw detection surface (the ultrasonic incident surface) of the object to be inspected. Since the reflected waves from the bottom surface of the object to be inspected (the surface facing the incident surface) are displayed, if the object to be inspected is thin (approximately 5 am or less), these flaw detection It becomes difficult to separate the surface reflected wave S, the defect reflected wave F, and the (nth) bottom surface reflected wave Bn, making it impossible to perform an effective search. In addition, it is related to the wall thickness of the inspected object (,
In the so-called near-field sound field near the flaw detection surface, a phenomenon occurs in which the defect detection sensitivity decreases.

On the other hand, in the transmission method, evaluation is performed by using the reduction or blockage of ultrasonic waves due to defects in the object to be inspected. The receiving probe for receiving waves must be placed so as to sandwich the object to be inspected and face the transmitting probe, which requires complicated construction. Generally speaking, when inspecting a wide area of the object to be inspected, a transmitting probe that transmits ultrasonic waves is scanned, and a receiving probe is simultaneously scanned on the opposite side while maintaining coaxiality with the acoustic axis of the ultrasonic waves. I have to let it happen.

For this purpose, a drive mechanism is required to scan the transmitting probe and the receiving probe.

This invention was made in view of the above problems, and its purpose is to enable flaw detection even when the wall thickness of the object to be inspected is thin, and yet requires complicated preparation work and complicated equipment. Our goal is to provide an unprecedented ultrasonic flaw detection method.

[Means to solve the problem]

The purpose of the above is to place a probe that transmits and receives ultrasonic waves on the testing surface side of the test object that is immersed in water or oil, and to place a probe that sends and receives ultrasonic waves on the anti-flaw detection surface side away from the test object. flaw detection is performed by placing an ultrasonic reflector in the probe and transmitting ultrasonic waves from the probe toward the flaw detection surface of the object to be inspected, and after passing through the object to be inspected, This is achieved by an ultrasonic flaw detection method that evaluates defects inside the object to be inspected based on the peak value of the ultrasonic wave that is reflected, passes through the object to be inspected, and reaches the probe on the VH surface side. Ru.

[For production]

In the ultrasonic flaw detection method according to the present invention, an ultrasonic reflector is placed on the opposite side of the test object at a distance from the test object, and a probe placed on the deep side is directed to the test object. By transmitting ultrasonic waves toward the probe, ultrasonic waves are reflected by the ultrasonic reflector and returned to the probe, and defects inside the object to be inspected are evaluated using the wave height value. That is,
If there is a defect inside the object to be inspected, there will be a layer of air in that area, so the reflected waves from the ultrasonic reflector will decrease or become zero, so connect this to the probe. All you have to do is observe it at the Brown Palace Oshiro. 2. Since the ultrasonic reflector is placed apart from the object to be inspected, the reflected waves from the object to be inspected and the waves reflected from the ultrasonic reflector can be separated, and the thickness of the object to be inspected can be Even if the damage is weak, it is possible to search for victims.

In addition, since ultrasonic waves are transmitted and received using a single probe,
Preparation work for detective work is simple, and scanning of the probe is easy even when inspecting a wide range of objects to be inspected.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is an explanatory diagram of the ultrasonic flaw detection method according to the present invention,
FIG. 2 is a waveform diagram showing the output waveform displayed on the cathode ray tube oscilloscope at this time. In addition, in Figure 1,
The same parts as in FIG. 3 are given the same reference numerals, and their explanation will be omitted.

As shown in FIG. 1, an ultrasonic reflector 6 is placed at a distance t from the object 2 to be inspected on the anti-exploration surface wJ (lower part in FIG. 1) of the thin object 2 to be inspected. The reflecting surface 6a is flat and perpendicular to the sound axis of the ultrasonic wave 5 transmitted from the bracket probe 4.

Note that this ultrasonic reflector 6 is made of steel having a high sound pressure reflectance.

The probe 4 currently placed on the flaw detection surface side of the object to be inspected 2
The ultrasonic waves 5 are transmitted from the ultrasonic wave 5 toward the object 2 to be inspected. Ultrasonic waves are divided into components that are reflected at the interface between different materials, that is, components that are reflected at areas with different acoustic impedances, and components that are encountered.
As shown in Fig. 2, the cathode ray tube oscillograph connected to the probe 4 receives reflected waves from the flaw detection surface of the object to be inspected 2 (flaw detection surface reflected waves S), and reflected waves from defects in the object to be inspected 2. (In the defect reflected wave), the reflected wave from the bottom surface of the object to be inspected 2 (nth bottom surface reflected wave Bn) and the reflected wave from the ultrasonic reflector 6 are displayed.

Here, attention is paid to the reflected wave from the ultrasonic reflector 6, and defects inside the inspected object 2 are evaluated using this wave height value. That is, if there is a defect 3 or a discontinuity inside the object 2 to be inspected, a layer of air will be present in this part, and the transmittance of ultrasonic waves will decrease, or the ultrasonic wave 5 is completely blocked, the peak value of the reflected wave from the ultrasonic reflector 6 decreases or becomes zero. Defects inside the object to be inspected 2 can be evaluated by observing this with a cathode ray tube oscillograph connected to the probe 4. Note that the distance between the object to be inspected 2 and the ultrasonic reflector 6 is sufficient, and the
Waves B,, Bs... are reflected waves R from the ultrasonic reflector 6
Adjust in advance so as not to affect the

〔Effect of the invention〕

As is clear from the above explanation, in the ultrasonic flaw detection method according to the present invention, a probe that transmits and receives ultrasonic waves is placed on the flaw detection surface side of the test object immersed in water or oil, and a An ultrasonic reflector is placed on the testing surface side away from the object to be inspected, and flaw detection is performed by transmitting ultrasonic waves from the probe toward the testing surface of the object to be inspected. Defects inside the object to be inspected are evaluated using the peak value of the reflected wave. Here, since the ultrasonic reflector is placed apart from the object to be inspected, the reflected waves from the object to be inspected and the waves reflected from the ultrasonic reflector can be sufficiently separated. Even when the wall thickness is thin, flaw detection can be performed reliably. In addition, since it is a so-called one-probe method in which ultrasonic waves are transmitted and received using one probe, the preparation work for the inspection is simple, and even when testing a wide range of objects to be inspected. Since there is no need to scan the transmitting probe and the receiving probe in synchronization, the scanning of the probes is easy.

For these reasons, according to the present invention, improvement in defect detection latitude and work efficiency can be expected in ultrasonic flaw detection tests.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the ultrasonic flaw detection method according to the present invention, Fig. 2 is a waveform diagram showing the output waveform displayed on a cathode ray tube oscilloscope when performing the ultrasonic flaw detection method according to the present invention, and Fig. 3 is an explanatory diagram of the conventional ultrasonic flaw detection method, and FIG. 4 is a waveform diagram showing the output waveform displayed on the Brownian oscillograph when the conventional ultrasonic flaw detection method is performed. 2: Inspected object, 3: Defect% 4: Probe, 5: Super defective 1
Kaushi 2 Kuni

Claims (1)

[Claims] 1) A probe that transmits and receives ultrasonic waves is placed on the flaw detection side of the test object immersed in water or oil, and an ultrasonic reflector is placed on the anti-flaw detection side at a distance from the test object. place,
Flaw detection is performed by transmitting ultrasonic waves from the probe toward the detection surface of the object to be inspected, and after passing through the object to be inspected, the ultrasonic waves are reflected by the ultrasonic reflector and transmitted through the object to be inspected again. An ultrasonic flaw detection method characterized in that defects inside the object to be inspected are evaluated based on the peak value of the ultrasonic waves that reach the probe on the flaw detection surface side.