JPS6287854A - Method for ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To certainly inspect the flaw of a surface layer or the fine flaw of an extremely thin material without receiving the effect of a signal propagation delay time between circuits, by operating a gate circuit by the pulse of a surface echo appearing at first after a set pulse width has been closed. CONSTITUTION:A peak detector 7 has a delay trigger circuit 14 setting the pulse width of a delay trigger operated when the lever of a transmission pulse exceeds a threshold value and a gate circuit 16 capable of setting the pulse width of a gate to an arbitrary position and width and detects the peak value of a reflected wave to output voltage proportional to said peak value. The flaw echo of the surface layer flaw close to the surface of an object to be inspected or the fine flaw internally present in an extremely thin material appears in extremely close vicinity to a surface echo. Therefore, when the circuit 14 is operated in such a state that the level of the transmission pulse exceeds the set threshold value and the set pulse width is closed, no delay is applied by the pulse of the surface echo and the circuit 16 is operated by the pulse of the surface echo appearing at first thereafter to open the gate so as to contain the surface echo and the flaw echo in the pulse width of the gate.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an ultrasonic flaw detection method for inspecting internal defects in materials or products, particularly in the vicinity of the surface of objects to be inspected, such as metal materials, ceramics, ICs, etc., and thin materials. This is a suitable flaw detection method for inspecting inherent minute defects.

(Background of the Invention) In materials or industrial products, it is used to detect internal defects in so-called thin materials and defects that exist near the surface of the specimen even if the thickness is not so thin (hereinafter referred to as surface defects). This has been carried out quite a lot in various technical fields.In order to enable new materials, electronic products, etc. to exhibit significantly higher performance and functionality than in the past, flaw detection is performed on the surface layer, which is closer to the surface. It has become necessary to reliably detect defects and even minute defects.An example of a flaw detection method using a conventional general flaw detection device will be explained with reference to Figs. 3 to 5. In this diagram, 1 is a water tank filled with water 2, 3 is a thin specimen placed at the bottom of the water tank 1, 4 is a probe immersed in water 2, and 5 is a probe immersed in water 2. A pulse circuit that causes the probe 4 to emit ultrasonic pulses; 6 a receiving circuit that receives and amplifies reflected waves reflected from the surface, defects, and bottom of the object 3 via the probe 4;
7' is a peak detector that detects the peak value of the reflected wave amplified by the receiving circuit 6 and outputs a DC voltage proportional to the peak value, and 8 is an oscilloscope that displays the waveform output from the peak detector 7'. FIG. 4 is a main block circuit diagram of the peak detector 7', in which 9 is an input circuit into which the pulse of the reflector amplified by the receiving circuit 6 is input, 10 is a trigger circuit, and 11 is a delay trigger pulse generator. 12 is a monitor circuit; 13 is a monitor synchro circuit; 14 is a delay trigger threshold setting circuit for setting a threshold to increase;
15 is a delay trigger circuit that sets the pulse width of a delay trigger that is activated when the level of the transmission pulse of the probe 4 exceeds the threshold; 15 is a delay circuit that sets the delay pulse width; 16 is a delay trigger circuit that sets the pulse width of the delay trigger; These gate circuits are capable of setting the gate pulse width to an arbitrary position and width, and are connected to the multiplexer 17 to form a gate control circuit 18 that adjusts the delay trigger, delay, and gate pulse widths. 19 is an RF that detects the pulse input to the input circuit 9;
A ridge wave circuit 20 converts the output signal of the RF detection circuit 19 into a DC'[pressure proportional to the value thereof and holds the value until the gate signal of the gate control circuit 18 is closed; 21 a peak detection circuit 20; This is an output circuit that outputs a DC voltage. FIG. 5 is a characteristic diagram illustrating a flaw detection method using the flaw detection device. In the figure, +8> is subject 3
This is an example of an echo pattern of a reflected wave from a transmission pulse, where T indicates a transmitted pulse, S indicates a surface echo, F indicates a defect echo, and B indicates a bottom echo. L is a line indicating the threshold level of the level of the transmission pulse T. fb) is the delay trigger circuit 14
(C) is the pulse width Pd of the communication trigger set in the delay circuit 15, (dl is the pulse width P9 of the gate set in the gate circuit 16).

As soon as the level of the transmitted pulse T emitted from the probe 4 exceeds the set threshold;
4 is activated and the delay trigger pulse D pL is set.Subsequently, when the surface echo S exceeds the threshold,
The delay circuit 15 and gate circuit 16 operate to start the sequence, and the gate opens at the same time as the delay pulse width Pd closes, and closes after the set pulse width P9 has elapsed. Here, as shown in FIG. 5(d), even if the circuit is configured to open the gate at the same time as the delayed pulse in the surface echo S closes, the signal propagation delay time P9 between the circuits
Since there is always □, it is as if the gate has a delay pulse width P
.

After the propagation delay time P9n has elapsed after the gate is closed, it becomes the same state as if it were opened, and even if the pulse width is set to P, the pulse width of the actually open gate is P9. becomes.

The defective echo F is just included within the pulse width P, . This condition appears in flaw detection when the specimen 3 is a thin material with a certain thickness, for example around 11, or more, but it is caused by minute surface defects very close to the surface of the specimen 3. Ultra-thin material, e.g. thickness 200-300
When inspecting minute defects inherent in an object of about μm size, the surface echo S and the defect echo F appear very close to each other, so the defect echo F is divided into the pulse width p of the gate.
It cannot be made to appear within 9s. This is because the minimum pulse width Pa, P, which can be set with the current delay circuit 15 and gate circuit 16 is about 60 to 80 ns, and the propagation distance of the pulse corresponding to this time is about 350 μm, and the surface of the object 3 This means that unless the distance from the surface to the defect is about 350 μm or more, the defect echo F cannot appear within the gate pulse width P. On the other hand, if the distance from the surface to the defect is about 350 μm or more, Even if the defect echo F appears within the pulse width P9, if the thickness of the object 3 or the surface defect is such that it appears within the propagation delay time P911, it will not actually be gated, and the defect echo F will be detected in both cases. Therefore, there was a problem that it was impossible to test the subject.

[Purpose of the invention]

The present invention solves the above-mentioned problems of the prior art, and reliably detects surface defects very close to the surface of the test object and minute defects inherent in ultra-thin materials without being affected by the signal propagation delay time between circuits. The purpose of the present invention is to provide an ultrasonic flaw detection method that can perform inspection by gating defect echoes.

[Summary of the invention]

The present invention includes a pulse circuit that causes a probe to emit ultrasonic pulses, a receiving circuit that receives and amplifies reflected waves reflected from the surface, defect, and bottom of an object through the probe, and a delay trigger circuit that sets the pulse width of a delay trigger that is activated when the level of the transmitted pulse exceeds a threshold; and a gate circuit that can set the pulse width of the gate to an arbitrary position and width; An ultrasonic flaw detection device equipped with a peak detector that detects the peak value of the reflected wave amplified by the receiving circuit and outputs a voltage proportional to that value, and an oscilloscope that displays the waveform output from the peak detector detects the peak value of the reflected wave amplified by the receiving circuit. In a flaw detection method for flaw detecting a test object in a tank, the pulse width set by the delay trigger circuit is
The pulse of the surface echo of the reflected wave reflected from the surface of the object that appears first after being closed activates the gate circuit to open the gate, thereby detecting a surface defect very close to the surface of the object. This method makes it possible to reliably detect defect echoes and inspect minute defects inherent in ultra-thin materials without being affected by signal propagation delay time between circuits.

[Embodiments of the invention]

One embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 2 is a main block circuit diagram of the peak detector according to this embodiment, which has a circuit configuration in which the delay circuit 15 is eliminated compared to the conventional peak detector 7' shown in FIG. FIG. 1 is a characteristic diagram for explaining a flaw detection method using the flaw detection apparatus shown in FIG. 3, which is equipped with a peak detector 7. In FIGS. 1 and 2, the same reference numerals as in FIGS. 3 to 5 indicate the same components. As shown in the echo pattern in (a), the defect echo F of a surface defect very close to the surface of the object 3 or a minute defect inherent in an extremely thin material is
It appears very close to the surface echo S. Therefore, in the present invention, when the level of the transmission pulse T exceeds a set threshold value and the delay trigger circuit 14 is activated, and the pulse width P of the set peak is closed, the pulse of the surface echo S is The gate circuit 16 is activated to open the gate by the pulse of the surface echo S that appears first after that without delay, and the surface echo S and the defect echo F are generated within the pulse width P9 of the gate in (d). be included. In this case, the peak value of the echo within the gate pulse width 2g is the surface echo S, but the signal propagation delay time P between the circuits. Therefore, even if the gate pulse width is P9, the gate pulse I is actually open! In this case, P9m, and the surface echo S falls within the propagation delay time P9, so it is not detected. Therefore, in the end, only the defect echo F within the pulse width of 29 m is detected and its peak value can be evaluated. In this way, the surface echo S and the defect echo F are close to each other but are displayed separately, such as a surface defect or an internal defect of an ultra-thin material. It is possible to reliably inspect the information by reusing it in a corresponding manner.

〔Effect of the invention〕

As explained above, the present invention provides a flaw detection method for detecting defects in a test object in a liquid tank, in which a pulse width set by a delay trigger circuit is reflected from the surface of the test object that first appears after closing. The pulse of the surface echo of the reflected wave activates the gate circuit and opens the gate, allowing the signal propagation between the circuits to detect surface defects very close to the surface of the object and minute defects inherent in ultra-thin materials. It has an excellent effect of being able to reliably gate and detect defect echoes and perform flaw detection without being affected by delay time.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram illustrating an example of the flaw detection method of the present invention;
FIG. 2 is a diagram showing an example of a main block circuit of a peak detector that appears in the characteristic diagram shown in FIG. 1. Fig. 3 is an explanatory diagram of the configuration of a general flaw detection device, Fig. 4 is a main block circuit diagram of a conventional peak detector, and Fig. 5 is a characteristic explaining the conventional flaw detection method using the peak detector shown in Fig. 4. It is a line diagram. l... Water tank, 3... Subject, 4... Probe, 5...
...Pulse circuit, 6...Reception circuit, 7.7'...Peak detector, 8...Oscilloscope, 14...
Delay trigger circuit, 15... Delay circuit, 16... Gate circuit, S... Surface echo, F... Defect echo, P
9n...Propagation delay time. Patent applicant Hitachi Construction Machinery Co., Ltd. Hitachi, Ltd. Agent Patent attorney Masaaki Akimoto
1 Figure 2 Figure 4 Procedural amendment to Figure 5 (voluntary) May 12, 1985

Claims (1)

[Claims] 1. A pulse circuit that causes a probe to emit ultrasonic pulses;
a receiving circuit that receives and amplifies reflected waves reflected from the surface, defect, and bottom surface of the object through the probe; and a receiving circuit that operates when the level of the transmitted pulse of the probe exceeds a threshold value. It has a delay trigger circuit that sets the pulse width of the delay trigger and a gate circuit that can set the pulse width of the gate to any position and width, and detects the peak value of the reflected wave amplified by the receiving circuit. In a flaw detection method that detects a specimen in a liquid tank using an ultrasonic flaw detection device equipped with a peak detector that outputs a voltage proportional to , and an oscilloscope that displays the waveform output from the peak detector,
The pulse width set by the delay trigger circuit activates the gate circuit to open the gate with a pulse of a surface echo of a reflected wave reflected from the surface of the subject that appears first after the gate is closed. An ultrasonic flaw detection method characterized by: 2. The pulse width of the gate of the gate circuit includes the surface echo and defect echo of the object to be inspected, and the propagation delay time of the signal between the circuits in the ultrasonic flaw detection device is made to correspond to the region of the surface echo. An ultrasonic flaw detection method according to claim 1, characterized in that: