JPS6326344B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection device capable of non-destructively inspecting the internal structure of a non-metallic object using a reflection method.

A conventional ultrasonic flaw detection device of this kind includes a transmitting sensor equipped with a piezoelectric element connected to an impact electric signal generator having a tuned circuit, a receiving sensor equipped with a piezoelectric element connected to a tuned amplification electric circuit, and the transmitting sensor. and a visual recognition device for converting and visually recognizing both the impact electric signal applied to the electric signal and the electric signal selectively and amplified from the receiving sensor through the tuned amplification electric circuit. Ultrasonic waves with a frequency band of several MHz transmitted from the transmitting sensor propagate within the metal object to be inspected, such as steel materials or welded structures, and the reflected waves reflected from the interface or internal defects are captured by the receiving sensor. ,
Convert to electrical signal. This electrical signal is sent to a visual recognition device via a tuned amplification circuit, and the waveform and propagation time of the reflected wave are measured to inspect the object to be inspected.It is useful for quality control of metal materials and construction management of structures. It has contributed significantly.

This technology is required to be widely applied to non-metallic materials, but since the constituent molecules of non-metallic materials themselves are larger than those of metals, and the content of closed microbubbles is large, high-frequency ultrasonic waves of several 100 KHz or higher are applied to non-metallic materials. On the other hand, even if you try to use a lower frequency, if you use a conventional thickness transducer, you have to make it significantly thicker than in metal flaw detection, so the damping is poor and the pulse width is very wide, reducing the resolution. Furthermore, since the thickness and radial dimensions are similar, thickness vibration significantly induces contour vibration and promotes surface waves, making it completely impossible to detect defects in non-metallic objects using the reflection method. It was hot.

Therefore, ultrasonic flaw detection for non-metals, such as detecting the presence or absence of adhesion defects in insulation materials attached to the inner walls of LPG tankers' holds, has been desired for many years, but has not been carried out at all. is the current situation.

This invention was made by focusing on these conventional problems, and the deflection type piezoelectric element with a fundamental frequency of KHz, which has conventionally been used only in audio equipment such as buzzers, has a thickness exceeding that of metal. It is as thin as that used for sonic flaw detection, and when pulse excitation can be used, dipping comparable to that used for metal ultrasonic flaw detection can be obtained.
It focuses on the fact that frequencies ranging from Hz to several 100 KHz can be obtained, and is based on a novel idea of using this as an ultrasound probe.

That is, the present invention solves the above problems by constructing the transmitting sensor and the receiving sensor from a deflecting piezoelectric element and a hard plate having a thickness proportional to the harmonic wavelength of the deflecting piezoelectric element. The purpose of the present invention is to provide a new ultrasonic flaw detection device that can easily inspect objects using a reflection method and with high precision.

The present invention will be explained below based on the drawings.

1 to 5 are diagrams showing one embodiment of the present invention.

First, the configuration will be described. Reference numeral 1 denotes a transmitting sensor, and a deflection-type piezoelectric element 3 bonded to a hard plate 2 by means of adhesive or the like is housed inside a case 4. Reference numeral 5 denotes an impact electric signal generator, which has a tuning electric circuit (not shown) tuned to the high frequency wavelength of the deflection type piezoelectric element 3, and connects the deflection type piezoelectric signal via a connector 6 provided at the top of the transmission sensor 1. It is connected to the piezoelectric element 3. 7 is wiring for the connection.

On the other hand, 8 is a reception sensor, which is a deflection type piezoelectric element 10 connected to a hard plate 9 like the transmission sensor 1.
is housed inside a case 12 having a connector 11 on the top. In addition, both the hard plates 2 and 9
is made of a metal plate having a thickness proportional to the harmonic wavelength of both deflection type piezoelectric elements 3 and 10, and is designed to emphasize a specific harmonic.

Reference numeral 13 denotes a harmonic tuning electric circuit for tuning and amplifying a specific harmonic component of the electric signal pulse sent from the deflection type piezoelectric element 10 of the receiving sensor 8.

Reference numeral 14 denotes a visual recognition device connected to the harmonic tuning electric circuit 13 and the impulse electric signal generating device 5, which includes, for example, a sweep circuit (not shown) and is connected to the cathode ray tube 1.
4a.

15 is wiring.

Next, the effect will be explained.

As shown in FIG. 3, the transmitting sensor 1 and the receiving sensor 8 are arranged and lightly pressed on the surface of a porous non-metallic object A such as plywood or foamed urethane. The high-frequency pulse of the electric signal generated by the impulse electric signal generator 5 is sent to the viewing device 14 via the wiring 7, and a waveform of the transmitted pulse is drawn on the fluorescent surface of the cathode ray tube 14a.

The other wave is sent to the deflection type piezoelectric element 3 of the transmitting sensor 1 and converted into a predetermined harmonic mechanical vibration within a frequency of several KHz to several 100 KHz. This harmonic vibration is emphasized by the resonance of the hard plate 2 and enters the object A to be inspected. In this case, since the vibrator uses a deflection type piezoelectric element 3 which is thinner than the radial direction, surface waves due to contour vibration are not generated even on porous plywood as in conventional thickness vibrators. . Further, it is possible to emit and propagate harmonic waves having good directivity and a frequency that does not scatter even in porous materials without using any couplant.

A portion of the propagated incident wave 16 is reflected by the adhesive layer B. When this reflected wave 17 reaches the reception sensor 8, it is transmitted to the upper deflection piezoelectric element 10, which is emphasized by the hard plate 9 in the same manner as described above, and is converted into an electric signal pulse in a unique harmonic band.

The electric signal pulse passes through the wiring 15 and is further selectively amplified by a harmonic tuning electric circuit 13 to select and amplify specific frequency components, and is sent to the visual recognition device 14, where the waveform of the received pulse is drawn on the fluorescent surface of the cathode ray tube 14a as in the conventional case. .

Figures 4 and 5 show waveforms drawn on the cathode ray tube 14a, and show the quality of the adhesion when two sheets of plywood with a thickness of 12 mm are glued together. This is an example of inspection using a low-frequency ultrasonic flaw detector. Figure 4 shows a location with poor adhesion, and Figure 5 shows a location with good adhesion. In the figure, T is the transmitted pulse, F is the echo reflected by the adhesive layer, and
B is the reflected echo from the opposite end face of the plate. As is clear from the figure, the quality of the adhesion can be easily detected from the difference in frequency and amplitude of the reflected echo F of the adhesive layer.

In addition to the above-mentioned reflection method, both transmitting and receiving sensors 1,
It is also possible to apply the parallel method in which the interval of 8 is arbitrarily set to be equal to or greater than the thickness of the object to be inspected.

In this case, ultrasonic waves coming from various routes are received, but if there are gaps due to cracks or peeling in the middle, high frequency components are cut off due to scattering and absorption, which can be detected as large fluctuations in frequency.

Therefore, it can be used to inspect large objects to be inspected, such as roads.

As explained above, according to this invention,
The transmitter and receiver sensors used as probes in conventional ultrasonic flaw detection equipment are constructed by bonding a deflection-shaped piezoelectric element to a hard plate having a thickness proportional to the harmonic wavelength of the piezoelectric element. Therefore, the wave can easily propagate even in porous soft materials and materials in which no couplant can be used.
The 10KHz frequency band can be used efficiently, and the contained harmonic waves act on intervening foreign objects that need to be detected, producing reflected waves. The effect is that non-metal flaw detection can be performed in the same manner as metal ultrasonic flaw detection.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a transmitting sensor and related equipment according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a receiving sensor and its related equipment, and FIG. 3 is an explanatory diagram of the use of the device according to the present invention. , FIG. 4 is a photographic diagram showing the test results of a poorly bonded area using the apparatus of the present invention, and FIG. 5 is a photographic diagram showing the test results of a well bonded area. 1... Transmission sensor, 2, 9... Hard plate, 3, 1
0... Deflection type piezoelectric element, 5... Impact electric signal generator, 8... Receiving sensor, 13... Tuned amplification electric circuit, 14... Visual recognition device.

Claims (1)

[Claims] 1: a transmitting sensor equipped with a piezoelectric element connected to an impulse electric signal generator having a tuned electric circuit; a receiving sensor equipped with a piezoelectric element connected to a tuned amplification electric circuit; an impulse electric signal to the transmitting sensor and the receiving sensor; In an ultrasonic flaw detection device comprising a visual recognition device for converting and visually recognizing electric signals that are selectively amplified from the sensor through the tuned amplification electric circuit,
An ultrasonic flaw detection apparatus for nonmetallic objects, wherein the transmitting sensor and the receiving sensor are constructed by bonding a deflection-shaped piezoelectric element to a hard plate having a thickness proportional to the harmonic wavelength of the piezoelectric element.