JPS62126346A - Method for ultrasonic detection in non-contact state - Google Patents

Abstract

PURPOSE:To economically and accurately perform flaw detection in a non- contact state with high efficiency, by a compact apparatus constituted so that the oscillation of an ultrasonic wave is performed by an electromagnetic ultrasonic system and the reception of a reflection signal is performed by a laser ultrasonic system. CONSTITUTION:An electromagnetic ultrasonic oscillation part 3 consists of a bias magnetic field generating circuit 4, a high voltage pulse generating circuit 5 and a high frequency magnetic core 6 having lead wires from said circuits wound therearound and a laser ultrasonic wave receiving part 7 consists of a laser oscillator 8, a half mirror 9, a mirror 10, a PIN diode 11 and a signal amplifying/processing circuit 12. The oscillation part 3 and the receiving part 7 are connected to a synchronous circuit 13. The ultrasonic wave oscillated by the magnetic core 6 of the oscillation part 3 is reflected by the flaw part 2 of a pipe 1 and the reflected ultrasonic wave is caught as a laser beam signal by the receiving part 7 and grasped as a flaw signal by the signal amplifying/ processing circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a non-contact ultrasonic flaw detection method for non-contact detection of defects, etc. on the inner surface of a tube in, for example, gas/dry brine.

[Prior art and its problems]

For example, non-contact ultrasonic flaw detection is used when it is not possible to perform contact flaw detection on the object to be inspected, such as inspecting for defects on the inner surface of a tube in a gas/zoo line, or online flaw detection in a steel hot rolling line. There is.

As such a non-contact ultrasonic flaw detection method, an electromagnetic ultrasonic method and a laser ultrasonic method are known. In addition to the advantage of non-contact flaw detection, the electromagnetic ultrasonic method can oscillate ultrasonic waves in various modes using a combination of a magnet (permanent magnet or electromagnet) and a coil. It has the feature of being able to receive only the following signals.

However, the electromagnetic ultrasonic method has poor conversion efficiency as a sensor, with a conversion efficiency of 40 to 50% during oscillation and reception.
A conversion loss of dB occurs. Therefore, in order to compensate for such conversion loss, when using permanent magnets, a large-sized magnet structure made of rare elements that has high coercive force during one oscillation is required, and when using electromagnets, It is necessary to increase the number of turns of the coil and to flow a large current. Furthermore,
During reception, it is necessary to use an amplifier with a high amplification factor and average the received signal to improve the S/N ratio.

On the other hand, the laser ultrasonic method has the advantage of non-contact flaw detection as well as the ability to directly capture the displacement of the object to be inspected as a received signal.

However, the laser ultrasonic method uses several B at the time of reception.
While a laser output of about W is sufficient, during excavation a high-power laser of at least several W is required to excite the ultrasonic waves to the object to be inspected, which makes the equipment expensive and difficult to install. A wide space is required for this purpose.

As described above, although the conventional non-contact ultrasonic flaw detection method has the advantage of being able to perform non-contact flaw detection, it has many problems as described above.

[Purpose of the invention]

Therefore, the purpose of this invention is to solve the above-mentioned conventional problems, and to be able to perform non-contact flaw detection economically and accurately with high efficiency using a connoxious device that does not require large amounts of power during oscillation. The object of the present invention is to provide a non-contact ultrasonic flaw detection method.

[Summary of the invention]

The present invention provides a non-contact ultrasonic flaw detection method in which ultrasonic waves are oscillated toward an object to be inspected and defects are detected by the reflected signals thereof, in which the oscillation of the ultrasonic waves is performed using an electromagnetic ultrasonic method,
The apparatus is characterized in that the reflected signal from the object to be inspected is received by a laser ultrasonic method.

[Structure of the invention]

Next, the method of the present invention will be explained with reference to the drawings.

The drawing is a block diagram illustrating one embodiment of the method of the invention. As shown in the drawings, in the present invention, as an object to be inspected, for example, a defect 2 occurring on the inner surface of a circumferential weld 1' of a pipe 1 in a pipe line etc. is detected by non-contact ultrasonic flaw detection. In order to do this, the oscillation side uses an electromagnetic ultrasonic method.

The receiving side uses a laser ultrasound system.

The electromagnetic ultrasonic oscillator 3 includes a bias magnetic field generating circuit 4, a high voltage/gurus generating circuit 5, and a high frequency magnetoelectric generator around which core wires from each of the bias magnetic field generating circuit 4 and the high voltage/gurus generating circuit 5 are wound.・It consists of 6.

The laser ultrasonic receiver 7 includes a laser oscillator 8, a half mirror 9 and a mirror 10 for changing the laser beam from the laser excavator 8 in the direction of the arrow, a PIN diode 11, and a signal amplification processing circuit 12. ing. Reference numeral 13 denotes a synchronization circuit between the electromagnetic ultrasonic oscillator 3 and the laser ultrasonic receiver 7.

Frost: The ultrasonic waves excavated by the high frequency magnetic core 6 of the magneto-ultrasonic excavation unit 3 are reflected at the defective part 2 of the tube (2) as shown by the arrow. The ultrasonic waves emitted from such an electromagnetic ultrasonic excavation section 3 and reflected at the defective section 2 are captured by the laser ultrasonic receiving section 7 as a laser light signal, and grasped as a defect signal by the signal amplification processing circuit I2. .

As described above, according to the method of the present invention, electromagnetic ultrasound is used only for oscillating ultrasound waves, and laser ultrasound is used for receiving the oscillated ultrasound waves. It is possible to prevent the influence of induction due to high power generated during oscillation on the receiving coil, and there is no need for a high-output laser during oscillation as in the laser ultrasonic method.

〔Effect of the invention〕

As mentioned above, according to the present invention, non-contact ultrasonic flaw detection of the inner surface of a tube in a gas/zooline, for example, can be performed with high efficiency without requiring large amounts of power during excavation and with a compact device. It can be carried out economically and accurately, resulting in excellent industrial effects.

[Brief explanation of drawings]

The drawing is a block diagram illustrating one embodiment of the method of the invention. In the drawings, 1...pipe, 1'...welded part, 2...
・Defect part, 3... Electromagnetic ultrasonic oscillation part, 4...
Bias magnetic field generation circuit, 5... High voltage, o-ruse generation circuit, 6... High frequency magnetic core, 7... Laser ultrasound receiving section. 8...Laser oscillator, 9...Nof mirror, 1
0. Mirror, 11... PIN diode, 1
2...Signal amplification processing circuit, ■3...Synchronization circuit.

Claims (1)

[Claims] In a non-contact ultrasonic flaw detection method in which ultrasonic waves are emitted toward the object to be inspected and defects are detected by the reflected signals, the ultrasonic waves are oscillated by an electromagnetic ultrasonic method, and the reflected signals from the object to be inspected are detected. A non-contact ultrasonic flaw detection method characterized by receiving signals using a laser ultrasonic method.