JPH089642Y2 - Ultrasonic flaw detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an ultrasonic flaw detector using an electromagnetic ultrasonic transducer that is applied to nondestructive inspection of steel structures and nonferrous products during manufacturing of steel and nonferrous products.

[Conventional technology]

In the case of ultrasonic flaw detection using an electromagnetic ultrasonic transducer, in addition to reflected waves from defects, random impulse electric noise waves such as factory motor and switching noise when the crane electric furnace is operating are mixed. A gate is provided at the time when the defect wave appears in advance, the peak of the detection wave of the defect signal is held in the gate, and the recorded data of the defect is taken by a pen recorder or the like, so random disturbance noise is generated in the gate. When mixed, this disturbance noise is recorded in the recording data of a pen recorder or the like, so that the defect signal and the disturbance noise cannot be discriminated from the recording data.

[Problems to be solved by the device]

In the above method, when disturbance noise enters the gate, from the data of the pen recorder, which is the flaw detection result,
The following cannot be identified:

1) When there is a defect signal: When the noise level is higher than the defect signal, a noise peak is output and the defect peak cannot be obtained.

2) If there is no defective signal, it is impossible to distinguish whether the output signal is due to the defective signal or noise.

As described above, when noise enters the gate, it becomes impossible to estimate the existence of a defect, let alone the peak value thereof.

[Means for solving the problem]

In order to solve the above-mentioned problem, the defect extracting apparatus according to the present invention has n defect detectors under the condition that the defect occurrence site is substantially constant, that is, the time at which the defect signal appears is substantially constant. , One F-V converter (frequency-voltage converter) for each one gate, one comparator is used, and an OR circuit for taking the logical sum of n comparators, flaw detector It is characterized by including a time base circuit that generates a gate timing signal based on the trigger signal from the.

[Action]

In the present invention, as described above, the reflected wave passing through the preset gate is input to the frequency-voltage conversion, the output voltage of this conversion circuit is increased, and the defective signal is generated only when the reference level of the comparator is exceeded. It is output, and it is possible to make the probability of false detection due to noise as close to zero as possible. If it is a defect, it will always enter the gate continuously, but in the case of noise, it is extremely unlikely that it will enter the gate multiple times in succession. That frequency without generating transmission waves - whether the output voltage of the voltage conversion circuit increases the maximum extent, Be prepared with the voltage E _N, by setting the reference voltage of the comparator a (E _N + α), the What exceeds the level is nothing but a defect. This device can be applied to the case where the subject moves, but in order to increase the moving speed and keep the set voltage constant, it is necessary to shorten the period for transmitting the transmission wave, that is, repeatedly increase the frequency.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to illustrated embodiments.
FIG. 4A shows a received signal of the electromagnetic ultrasonic flaw detector,
(B) is the waveform of the rectified envelope. A and C are transmitted waves, and B and D are reflected waves due to defects.
(C) represents the gate timing signal, which is the gate width Δt ₁ , Δt ₂ , ..., Δt _n (all may be equal),
The trigger signal from the flaw detector of (d) is t ₁ , t ₂ , ..., t _n
, And gate channels G ₁ , G ₂ , ..., G _n are opened in order and the signals are addressed in order. Under the condition that the time at which the defect reflected wave appears is almost constant, the number of gates should be as small as possible and the gate width should be as narrow as possible according to the principle of noise removal. In addition, the trigger of (d) is synchronized with the signal, a tone burst wave such as A of (a) is oscillated, and an ultrasonic wave is generated in the subject every 1 / f _r (sec). FIG. 2 (repeating frequency is f _r Hz) shows an envelope rectified waveform when noise (E) is superimposed on the defect reflected wave (F). With such a waveform, it becomes impossible to determine the presence or absence of a defect reflection signal due to noise. However, it is considered statistically that the probability of continuous noise covering at such a timing sharply decreases as the number of consecutive times increases. In FIG. 3, (a) is a defect reflection wave, (b) is a gate timing signal, and (c) is a defect reflection wave that has passed through the gate, and is pulsed. FIG. 1 shows a block diagram of a flaw detector according to an embodiment of the present invention. The flaw detection output waves that pass through the gates 1 to n and are pulsed are input to an FV converter (frequency-voltage converter) FV. The outputs of the n F-V converters FV are each connected to a comparator, and the outputs of these n comparators are connected to an OR circuit that takes their logical sum. For example, if the signal coming into the gate k is due to a defect, it comes in continuously, so the output level of the FV converter FV rises, exceeds the reference level of the comparator k, and the OR circuit Send a detection signal to OR. If the signal coming into the gate k is noise, it is unlikely that the noise will come in a plurality of times in succession, and since the noise is random, the output of the FV converter k is the comparator k.
It does not reach the reference level of and the detection signal is not output to the OR circuit. The detection signal output from the OR circuit enters the one-shot multi circuit and delays the defect detection signal to some extent. By the principle as described above, the influence of noise can be removed, and the defect can be detected. FIG. 5 shows a time chart of each part when a defect is detected.

[Effect of device]

The present invention makes it possible to remove disturbance noise and the like by using the above-described signal processing in electromagnetic ultrasonic flaw detection under environmental conditions in which impulse-like disturbance noise and the like are generated, and at the same time, the object or the electromagnetic ultrasonic transducer can be removed. Even under the condition that the side moves, the presence of a defect can be output by a voltage output or the like, and the defect can be easily identified by the recorded data of a pen recorder or the like.

[Brief description of drawings]

FIG. 1 is a block diagram of a flaw detector according to an embodiment of the present invention, FIG. 2 is a waveform diagram in which noise is superimposed on a defect reflection wave of a flaw detection signal, and FIG. 3 is a gate timing signal. FIG. 4 is a defect reflection waveform diagram after passing through a gate, FIG. 4 is a timing diagram of a flaw detection signal, and FIG. 5 is a timing diagram according to an embodiment of the present invention.

Continuation of front page (56) Reference JP-A-63-115053 (JP, A) JP-A-61-155856 (JP, A) JP-A-61-91566 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A frequency-voltage conversion circuit converts a reflected wave pulse of an ultrasonic wave emitted by an ultrasonic transducer due to a defect passing through a preset gate into a voltage that increases according to the number of pulses, and outputs the output. An ultrasonic flaw detector characterized by detecting a defect by outputting a signal exceeding the reference level as a detection signal in comparison with the reference level.