JPH02205749A - Apparatus for detecting crack and the like of solid - Google Patents

Abstract

PURPOSE:To make it possible to detect cracks and the like in the inside of a solid and the like quickly and accurately by providing a constitution which is provided with a striking device, a sound wave detector, a trigger circuit, first and second delay circuits, a peak detector, and a comparator. CONSTITUTION:A striking device 2 strikes a body under test 1 comprising a hard and brittle solid so as to cause vibration. Thus sound waves are generated. A sound wave detector 6 collects and amplifies the generated sound waves and outputs the sound wave signal. A trigger circuit 7 outputs a trigger signal when the sound wave signal has a sound pressure at a specified level or more. A first delay circuit 8 is operated by the trigger signal. The circuit 8 sets the starting time for receiving the output signal of the sound wave detector 6 and the receiving time period of said signal. A peak detector 9 is operated by the output signal of the delay circuit 8 and detects the peak value outputted from the sound wave detector 6. A second delay circuit 10 sets the reception terminating time of the output signal from the peak detector 9. A comparator 11 is operated by the output signal from the delay circuit 10, compares the peak value outputted from the peak detector 9 with a preset threshold value and outputs the compared value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for detecting cracks, etc. in a solid, and in particular, a device for easily detecting cracks, etc. occurring on the surface or inside of a solid.
The present invention relates to a detection device suitable for rapid and highly accurate detection.

Note that the solid here refers to hard materials such as metal materials,
It refers to hard and brittle materials such as glass and ceramics, and parts made of these materials.
In addition to various types of separation such as welding cracks, fatigue cracks, and polishing cracks, it also includes a state where a part of the solid is missing.

(Prior Art) Conventionally, to detect cracks, etc. in the solid, one of the quality inspections is so-called acoustic testing, in which the solid is struck with a hammer or the like and the quality is inspected by listening to the sound waves generated by the solid.
It was done as a method.

This acoustic test is performed by directly listening to the sound generated by the subject with the examiner's ears, or in the case of low sound pressure level sounds, an electroacoustic transducer (for example, a microphone) is used.
In both cases, cracks were detected by the sense of what the inspector heard with his/her ears. .

[Problem to be solved by the invention]

As mentioned above, the detection of cracks, etc. in solids relies on the inspector's auditory judgment, so in order to perform accurate and efficient inspections, the inspector needs to be highly skilled. At the same time, it was necessary to maintain the surrounding noise environment at a certain level at the inspection location.

However, the level of proficiency of the examiner requires not only the ability and physical strength of the examiner, but also many years of experience, and at the same time, the effectiveness may vary depending on the examiner's physical condition and age at the time. There are also some things that you may not be able to fully demonstrate. For this reason, it is often difficult to secure skilled personnel, and even if one is secured, the accuracy and efficiency of the test varies depending on the physical condition, etc., and long-term test work poses health and safety concerns for the tester. It had problems such as having an adverse effect on

On the other hand, depending on the type of test subject, the test location usually contains other noises from sources other than the test subject, and it is difficult to ensure an environment where only the sounds generated by the test subject can be detected. It is often difficult. For this reason, unless the noise environment around the inspection location is maintained at a constant level, the inspector will also hear the other noises mentioned above at the same time, causing a reduction in the accuracy and efficiency of the inspection.

In view of the problems of the prior art described above, the present invention provides a detection device for detecting cracks in solids that can easily, quickly, and accurately detect cracks occurring on the surface or inside of a solid. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the device for detecting cracks in solids, etc. of the present invention includes a striking device that excites an object made of a hard and brittle solid by impact and generates sound waves from the object, and a striking device that generates sound waves from the object. a sound wave detector that collects sound, amplifies it, and outputs the sound wave signal; a trigger circuit that outputs a trigger signal when the sound pressure of the sound wave signal has a sound pressure of a certain level or more; and the sound wave detector that is activated by the trigger signal. a first delay circuit that sets the timing and time to start capturing the output signal of the first delay circuit;
a peak detector that is activated by the output signal of the delay circuit and detects the peak value output from the sonic wave detector; a second delay circuit that sets the end time of capturing the output signal from the peak detector; A comparator that is activated by the output signal of the second delay circuit and compares the peak value output from the peak detector with a preset threshold value and outputs the comparison value. It is.

Further, a concave-shaped sound collector is arranged to face the sound wave detector to the subject and collects sound generated from the subject;
It is preferable to include a microphone and an amplifier that detect and amplify the sound collected by the sound collector.

[Effect]

A subject subjected to impact vibration by the impact device generates sound waves, and the generated sound waves are collected by a sound wave detector, amplified, and outputted from the sound wave detector as a sound wave signal. When the sound pressure of the sound wave signal at the time of impact vibration is equal to or higher than a certain level, the trigger circuit outputs a trigger signal, and the trigger signal activates the first delay circuit and starts capturing the sound wave signal. The acquisition of the sound wave signal is waited for a preset time in the first delay circuit,
After that time has elapsed, the first delay circuit outputs a control signal that activates the peak detector and the second delay circuit.

The acquisition of the sound wave signal continues after waiting for a preset time in the second delay circuit, and then ends the acquisition.

After the acquisition of the sound wave signal is completed, the second delay circuit outputs a control signal to operate the comparator, and the comparator detects the peak value of the sound wave signal output from the peak detector and a preset threshold value. are compared, and the comparison value is output.

The comparison value output from the comparator is displayed on a display, for example, but the sound pressure level and attenuation status of the sound pressure signal vary greatly depending on the presence or absence of cracks in the test object, and the signal waveform also differs. By displaying on a device or the like whether or not the comparator has the change, the presence or absence of cracks etc. can be detected quickly and reliably.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS. 1 to 3. Figure 1 is a diagram showing the overall configuration of a device for detecting cracks, etc., and Figures 2 and 3 are diagrams showing an example of the waveform of a sound wave signal output from a sonic detector. The specimen consists of a hard and brittle solid, 2 is the specimen 1
This is a striking device that generates sound waves from the subject 1 by striking and vibrating it, and is constructed by, for example, attaching a steel ball to the tip of a thread-like or rod-like member. 3 is a sound collector that collects the sound generated from the subject 1. In order to improve the sound collection efficiency, the sound collecting surface is formed into a concave shape such as a paraboloid of revolution or an ellipsoid of revolution. It is placed facing the specimen 1. Reference numeral 4 denotes a microphone, which is arranged to face the concave shape of the sound collector n3 in order to efficiently convert the sound collected by the sound collector 3 into acoustoelectricity.

5 is an amplifier that amplifies the sound wave signal from the microphone 4, and the sound collector 3. Together with the microphone 4, a sound wave detector 6 is configured. Reference numeral 7 denotes a trigger circuit that outputs a trigger signal when the sound pressure of the sound wave signal from the amplifier 5 is equal to or higher than a predetermined level; 8 is a first delay circuit activated by the trigger signal; The capture start time T0 and capture time tl are set in advance. A peak detector 9 is operated and controlled by a signal from the first delay circuit 8, and detects the peak value output from the amplifier 5. Reference numeral 10 denotes a second delay circuit which is activated by a signal from the first delay circuit 8, and the timing at which the acquisition of the peak value signal from the peak detector 9 ends is set in advance. Reference numeral 11 denotes a comparator whose operation is controlled by the output signal of the second delay circuit 10, which compares the peak value output from the peak detector 9 with a preset threshold value and outputs the comparison value. Reference numeral 12 denotes a display that displays the comparison value output from the comparator 11. Reference numeral 13 denotes an elastic member for placing the subject 1 in a freely supported state, and by placing the subject 1 in a freely supported state, the vibration of the subject 1 during impact vibration is brought into a state close to free vibration, and thus can be eliminated as much as possible. A moving table consisting of a conveyor or the like is used for testing in the first-generation flow system, and a large number of subjects 1 are placed on the moving table 14 together with an elastic member 13 at regular intervals and moved in the direction of the arrow shown in the figure. This is suitable for automating inspections.

When the subject 1 is struck by the striking device 2 with a pendulum movement in the direction of the arrow from the position indicated by the chain line in the figure, the subject 1 is excited and generates sound waves, and the generated sound waves propagate through the atmosphere and are collected. The sound reaches the device 3, is converged by the concave surface of the sound collector 3, and is collected. The collected sound waves are sent to an amplifier 5 via a microphone 4, amplified, and sent to a trigger circuit 7 as a sound wave signal. The trigger circuit 7 outputs a trigger signal when a sound wave signal with a sound pressure of a certain level or more is input manually, and the first delay circuit 8 is activated by the trigger signal, and the T shown in FIG. 2 or 3 is activated. Acquisition of sound wave signals begins. When the first delay circuit 8 finishes receiving the signal for a preset time t1, the first delay circuit 8 outputs a control signal that activates the peak detector 9 and the second delay circuit 10, and the second delay circuit At step 10, following the above-mentioned acquisition, a signal is acquired for a preset time L2, and at T2 after time t2 has elapsed.
The import ends at . T2 that finished importing
When , a control signal for operating the comparator 11 is output from the second delay circuit B10, and in the comparator 11, the peak value ■ of the sound wave signal output from the peak detector 9 and the preset threshold value ■ , and the comparison value is sent to the display 12.

By the way, the waveform of the sound wave signal output from the amplifier 5 is
Since the test object 1 is a hard and brittle solid, the sound pressure is high and a loud sound is generated at T0 when the test object 1 is struck. However, if the test object 1 is a good product with no defects such as cracks, it is shown in Fig. 2. On the other hand, in the case of a defective product with defects such as cracks in the test object 1, as an example, the third As shown in the figure, it has a waveform characteristic that does not resonate and rapidly attenuates after a certain period of time (in the figure, after a set time). This clearly becomes V,>V when the peak is detected, and on the other hand, in the case of the defective product shown in FIG. 3, the time is also clearly V,
This appears as a relationship of <V.

A signal indicating the relationship between the peak value ■2 and the threshold value ■3 for the above-mentioned non-defective products and defective products is sent to the display 12, and the display 1
In step 2, for example, if a lamp or LED, etc. is used to determine pass/fail, it is possible to detect defects such as cracks by simply looking at the color of the lamp, etc., regardless of the inspector's skill level or the surrounding inspection environment. The specimen 1 can be detected instantaneously, and therefore cracks and the like can be detected from the specimen 1.

In addition, the signal related to the relationship between V and V is used to control the classification and sorting of non-defective products and defective products from the movable base 14 when a large number of objects 1 are continuously inspected using the movable base 14. It can be used as a signal.Furthermore, if the relationship between ■ and ■ is displayed in stages depending on the degree of cracking, etc., it is possible to sort out good products and defective products in stages. It can be used to determine whether or not repairs are possible.

In the embodiment described above, the trigger signal in the trigger circuit 7 is output by the sound wave signal sent from the amplifier 5, but this is performed by the impact device 2 on the subject 1.
This may be performed using a level signal of the excitation force generated by impact vibration, or may be performed using a signal from a dedicated microphone and amplifier provided separately from the microphone 4° amplifier 5.

〔Effect of the invention〕

Since the present invention is configured as described above, it has an excellent effect of being able to easily, quickly, and accurately detect cracks and the like occurring on or inside a solid.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing one embodiment of the device for detecting cracks in solids, etc. of the present invention, and FIG. 2 is a diagram showing an example of the waveform of a sound wave signal in the case of a non-defective product output from a sound wave detector. FIG. 3 is a diagram showing an example of the waveform of a sound wave signal in the case of a defective product corresponding to FIG. 2. 1... Subject, 2... Impact device, 3... Sound collector,
4... Microphone, 5... Amplifier, 6... Sound wave detector, 7... Trigger circuit, 8... First delay circuit, 9... Peak detector, 10... No. 2 delay circuit,
11...Comparator, 12...Display device. 41. -Microphone il! Figure 1 Patent applicant Hitachi Construction Machinery Co., Ltd. Agent Patent attorney Tadashi Akimoto 1 other person

Claims (1)

[Claims] 1. A striking device that excites an object made of a hard and brittle solid by impact and generates a sound wave from the object, and a sound wave signal that collects and amplifies the generated sound wave. a trigger circuit that outputs a trigger signal when the sound pressure of the sound wave signal is at a certain level or higher; and a trigger circuit that is activated by the trigger signal and determines when to start capturing and how long the output signal of the sound wave detector is to be captured. a first delay circuit to be set; a peak detector that is activated by the output signal of the first delay circuit to detect the peak value output from the sonic wave detector; and completion of capturing the output signal from the peak detector. The second step is to set the timing.
a comparator that is activated by the output signal of the second delay circuit and compares the peak value output from the peak detector with a preset threshold value and outputs the comparison value; A device for detecting cracks in solids, etc. 2. A concave sound collector that is arranged to face the sound wave detector and collect the sound generated from the test subject, and a microphone and an amplifier that detect and amplify the sound collected by the sound collector. 2. The apparatus for detecting cracks, etc. in a solid according to claim 1, comprising: