JPH04198736A - Detecting method for structure defect and detecting device thereof - Google Patents

Abstract

PURPOSE:To uniformly detect a defect over a wide measurement range without using a fluid such as oil by feeding an acoustic wave signal to an acoustic generator, pressing it to the surface of a tested structure, and detecting the structural change. CONSTITUTION:An acoustic wave signal is fed to an acoustic generator 20 from signal generator 11, the generator 20 is pressed to a tested structure 30 with a constant pressure and closely stuck on the surface, the acoustic wave vibrates the structure 30, and the moving coil impedance of the generator 20 is changed by the vibration state. When the airtightness between the structure 30 and the generator 20 is kept constant, the same change is detected for the same tested structure, the impedance change is phase-detected by a phase detec tor 12 at the same frequency as that of the signal generator 11, it is then ampli fied by an amplifier 13, the noise signal other than the acoustic change signal is cancelled by a signal processor 14, it is displayed on an X-Y recorder 15, thus the position and size of a cavity section 21 of the structure 30 difficult to detect can be detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to structures made of new materials such as carbon fibers, or composite materials of new building materials (hereinafter collectively referred to as structures), etc. The present invention relates to a method for detecting defects in structures and a device for detecting defects therein.

[Conventional technology]

Conventionally, methods for nondestructively detecting defects in structures include, for example, an ultrasonic flaw detection method, an eddy current flaw detection method, and a percussion testing method.

In other words, the ultrasonic flaw detection method uses a probe that transmits and receives ultrasonic waves. When ultrasonic waves are applied to the material to be inspected, if there is a defect in the material to be inspected, the ultrasonic waves are reflected and scattered depending on the size and shape of the defect. . A portion of the reflected wave is received by the probe and displayed on the image display device, thereby detecting the position and size of the defect.

In addition, in the eddy current flaw detection method, when an alternating magnetic field is passed through a conductor such as a metal tube using a coil, an eddy current flows through the conductor. When the inspected material made of a conductor is a good product with no defects, the eddy current does not change and remains constant, and when the inspected material has a defect, the eddy current changes. As a result, the presence or absence and position of defects in the inspected material are detected.

Furthermore, the hammering sound inspection method taps the material to be inspected to generate vibrations.
An inspector listens to the tone and detects defects based on changes in tone.

[Problem to be solved by the invention]

However, the above conventional technology has the following problems. That is, in the ultrasonic flaw detection method, a fluid such as oil is interposed between the probe and the material to be inspected, thereby contaminating the material to be inspected. Furthermore, if the structure of the material to be inspected is significantly different from the ultrasonic transmission performance, the reflection from the boundary surface will be large, making it impossible to measure the presence or absence of peeling or cavities near the adhesive surface. Further, due to its nature, ultrasonic waves have strong directivity, and the measurement range of the negative point is narrow. Although this is an advantage when measuring small defects,
Measurement over a wide range requires an accurate scanning mechanism, which poses the problem of complicating the structure.

In addition, since the eddy current testing method measures electromagnetic effects on the material being inspected, it can only be used with conductors such as metals, making it impossible to inspect materials made of insulators such as non-metals. There is a problem with this.

Furthermore, the hammering sound inspection method requires the inspector to judge defects by listening to the tone of the hammer, which requires the inspector's sensitivity and experience, and there is a problem in that it is not possible to make a uniform judgment. To solve this problem, there is a method that measures the change in tone through a microphone, but this method also inputs unnecessary noise other than the vibration sound of hitting the test material, making it difficult to obtain the desired detection accuracy. A new problem arises.

Therefore, the present invention has been made in consideration of the above circumstances.
The purpose is to provide a method for detecting defects in structures that can uniformly detect defects over a wide measurement range without intervening fluids such as oil, and has increased versatility.

Another object of the present invention is to provide a structural defect detection device that has a simplified structure, reduces the influence of noise, and improves detection accuracy.

[Means to solve the problem]

In order to achieve the above object, in the structure defect detection method according to the present invention, at least one sound wave signal is applied to an acoustic generator, and the acoustic generator is brought into close contact with the surface of the structure to be detected. The object of the present invention is to measure changes in acoustic impedance due to structural changes in the structure to be detected when the structure is pressed with a constant pressure, thereby detecting structural changes in the structure to be detected.

Further, in the structure defect detection device according to the present invention,
a transmitter that emits at least one sound wave signal; an acoustic generator that is in close contact with the surface of a structure to be detected and obtains the sound wave signal of the transmitter to measure changes in acoustic impedance due to structural changes of the structure to be detected; The present invention includes means for phase-detecting the impedance change signal of the acoustic generator at the same frequency as the oscillator, and means for recording and displaying the change in acoustic impedance. Preferably, a buffer width made of an elastic material is provided at the edge of the opening of the sound generator.

[For production]

In the present invention having the above configuration, at least one sound wave signal is applied to the acoustic generator to vibrate the acoustic generator,
When the acoustic generator is pressed with a constant pressure so as to come into close contact with the surface of the detected structure, the acoustic waves cause the detected structure to vibrate. This vibration state changes the impedance of the moving coil of the acoustic generator, and by phase-detecting this impedance change at the same frequency as the transmitter, it is possible to detect structural changes in the target structure that are difficult to detect. .

Further, the buffer width made of the elastic body provided at the edge of the opening of the acoustic generator acts to improve airtightness when the acoustic generator is pressed against the structure to be detected.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1st
An embodiment of the structure defect detection apparatus according to the present invention is shown in FIG. As shown in FIG. 1, the defect detection device is roughly composed of a detection device main body 10 and a sound generator (speaker) 20, and detects defects such as peeling and cavities in the detected structure 30 shown in FIG. It is something to detect.

The detection device main body 10 includes a transmitter 11 that transmits at least one sound wave signal, and a phase detector 12 that detects the phase of the acoustic change signal from the detected structure 30 using the sound wave signal sent from the transmitter 11 to the sound generator 20. , an amplifier 13 for amplifying the signal phase-detected by the phase detector 12, and a signal processor 1 for eliminating signals due to noise other than the acoustic change signal.
4, and X- as a means for recording and displaying acoustic change signals.
Y recorder 15.

The transmitter 11 emits in a frequency range of 30 Hz to 20 KH2, and the frequency is selected based on the material and structure of the structure 30 to be detected for detecting defects. When the detected structure 30 is a composite material panel as shown in FIG. 2, the frequency is set to approximately IKH7 to detect defects in the peeled lv portion.

The acoustic generator 20 obtains a sound wave signal from the transmitter 11 and measures changes in acoustic impedance due to structural changes in the detected structure 30, as shown in FIGS. 3(A) and 3(B). In order to absorb as much as possible the influence of unevenness of the detection structure 30, a buffer ring 22 made of an elastic material such as anti-vibration rubber is provided at the opening edge of the diaphragm (cone) 21.
- Pressed against the detected structure 30 with a constant pressure. Note that the buffer ring 22 is not limited to vibration-proof rubber, and may be an elastic body made of synthetic resin, for example.

Further, it is desirable that the sound generator 20 changes the shape of the buffer ring 22 in accordance with the surface shape of the detected structure 30. That is, when the distance between the diaphragm 21 of the acoustic generator 20 and the surface of the detected structure 30 is required, the buffer ring 22 is set at a distance of 2 to 2 when the detected structure 30 is flat.
A ring shape with a thickness of 3 mm and a width of several mm may be sufficient, but if the detected structure 30 has uneven parts, the ring shape shown in Fig. 4 (A) may be used.
.

As shown in (B), 20 mm is attached to the trumpet-shaped auxiliary member 23.
By attaching the buffer ring 24 with the above width, high airtightness can be maintained with respect to the detected structure 30.

Next, the operation of this embodiment will be explained.

A sound wave signal is applied from the transmitter 11 to the sound generator 20 to cause the diaphragm 21 of the sound generator 20 to vibrate. Next, as shown in FIG. 2, the acoustic generator 20 is pressed against the detection target structure 30 with a constant pressure to bring it into close contact with the surface thereof. Then, the acoustic wave causes the detected structure 30 to vibrate, and the moving coil φ impedance of the acoustic generator 20 changes depending on the vibration state.

At this time, the detected structure 30 changes depending on its material and structure, regardless of whether it is metal or non-metal. Here, if the airtightness between the detected structure 30 and the acoustic generator 20 is maintained constant,
The same change is detected in the same detected structure.

The phase detector 12 detects this impedance change from the oscillator 11.
After phase detection is performed at the same frequency as that of The position and size of the cavity 31 of the detection structure 30 can be detected.

Furthermore, a specific experimental example to which this embodiment is applied will be explained.

Experimental Example 1 As shown in FIGS. 5(A), 5(B), and 5(C), detection of cavities in a carbon material during the manufacturing process of a carbon head for a golf club was carried out under the following conditions.

Sound generator 20: Opening diameter 5cm, circular speaker, impedance 8Ω Buffer ring 22: 2III11 thickness, inner diameter 33mm, outer diameter 43m
11 Frequencies: 1. lKH2, relative amplification: 20dB
The acoustic generator 20 is pressed against the carbon head 32, 33, 34 as a structure to be detected shown in FIGS. The waveform is shown in Figure 6 (A).

Shown in (B) and (C). Therefore, looking at their relative output levels, carbon heads 32 and 34 have a high output level and are detected to be good products, while carbon heads 33 has a lower output level than carbon heads 32 and 34, so they are detected as defective products. It was detected that In this experimental example, when the amplified output signal of a non-defective product is pseudo-zeroed by the signal processor 14, the amplified output becomes a comparison signal with a non-defective product, and the comparative detection of non-defective products and defective products can be performed accurately and easily. be able to.

Experimental Example 2 Detection of a cavity 36 and a peeled part 37 of a composite material 35 as a structure to be detected as shown in FIGS. 7(A) and 7(B) was performed under the following conditions.

Sound generator 20: Opening diameter 5 cm, circular speaker, impedance 8Ω Frequency: 1.4 KIIZ, relative amplification +26 dB While pressing the sound generator 20 into close contact with the surface of the composite material 35, scanning was performed in the order of 81 to S5. Of the X and Y outputs, Sl and S
The X and Y output waveforms of No. 5 are shown in FIGS. 8(A) and 8(B), respectively. In the output waveform of FIG. 10(B) compared to FIG. 10(A), we found parts where the output level is significantly lower and parts where the output level is slightly lower. The part where the output level is significantly reduced indicates the presence of the cavity 36, and the part where the output level is slightly reduced indicates the presence of the peeled part 37.
We were able to fully detect them.

Here, in Experimental Example 2, by simultaneously transmitting a second signal frequency different from the above frequency from the transmitter 11, signal output due to noise (drift noise) generated at the contact surface of the acoustic generator 20, airtight leakage, etc. It is possible to offset the changes and further improve measurement accuracy. This is similar to the multi-frequency method used in eddy current testing.

In the above embodiments, the carbon head of a golf club or the composite material 50 of a new building material was used as the structure to be detected, but the present invention is not limited thereto and can be applied to any other structure. .

〔Effect of the invention〕

As explained above, the method for detecting defects in structures according to the present invention provides the following effects.

(a) Since defects are detected by bringing the acoustic generator into close contact with the structure to be detected, the structure to be detected is not contaminated without intervening fluid such as oil.

(b) By using the sonic frequency, it is possible to widen the measurement surface at the negative point and detect defects deep within the structure to be detected.

(C) Since the change in acoustic impedance due to vibration is measured, it is possible to easily compare good and defective structures regardless of whether the structure to be detected is metal or non-metal, and the versatility is significantly improved.

Moreover, according to the structure defect detection apparatus according to the present invention, the following effects are achieved.

(2) By phase-detecting the acoustic change signal from the detected structure using the sound wave signal sent to the acoustic generator, it is possible to reduce the effects of noise and improve detection accuracy.

■When detecting defects on a wide surface, an accurate scanning mechanism is not required, and the structure can be simplified.

Furthermore, since a buffer ring made of an elastic material is provided at the opening edge of the sound generator, when the sound generator is pressed with a constant pressure,
High airtightness with the structure to be detected is maintained, measurement conditions are kept constant, and detection accuracy can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a defect detection device according to the present invention, FIG. 2 is an explanatory diagram showing a defect detection state of a structure to be detected by the device of FIG. 1, FIG. 3(A), (B) is a perspective view 9 an exploded perspective view showing the sound generator of FIG. A), (B), and (C) are perspective views showing the carbon head of the golf club used in Experimental Example 1. Figure 6 (A), (B), and (C) show the experimental results of Experimental Example 1. Output waveform diagram, Figures 7 (A) and (B) are front views and cross-sectional views showing the composite material as the detected structure in Experimental Example 2, Figure 8 (A),
(B) is an output waveform diagram showing experimental results according to Experimental Example 2. 10...Detection device main body, 11...Transmitter, 12...
・Phase detector, 13...Amplifier, 14...Signal processor, 15...X-Y recorder (recording/displaying means), 2
0: Sound generator, 21: Vibration plate, 22: Buffer width, 30: Detected structure. Applicant's agent Hiromitsu Fujimoto (A) (B) Figure 3 Figure 4 36 (A) 3.7

Claims (1)

[Claims] 1. When at least one sound wave signal is applied to the acoustic generator and the acoustic generator is pressed with a constant pressure so as to come into close contact with the surface of the detected structure, the A method for detecting defects in a structure, characterized in that a structural change in a structure to be detected is detected by measuring a change in acoustic impedance due to a structural change. 2. A transmitter that emits at least one sound wave signal, and an acoustic generator that is in close contact with the surface of the structure to be detected and obtains the sound wave signal from the transmitter to measure changes in acoustic impedance due to structural changes of the structure to be detected. Detecting defects in a structure, comprising: a means for phase-detecting the impedance change signal of the acoustic generator at the same frequency as the transmitter; and a means for recording and displaying the change in acoustic impedance. Device. 3. A defect detection device for a structure according to claim 2, wherein a buffer ring made of an elastic body is provided at the edge of the opening of the acoustic generator.