JP2510393Y2 - Ultrasonic flaw detector - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an ultrasonic inspection apparatus using an electromagnetic ultrasonic transducer, which is applied to the nondestructive inspection of steel structures and nonferrous products during the manufacture 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, the following identification is not possible from the data of the pen recorder, which is the flaw detection result.

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

2) When there is no defective signal, it is impossible to distinguish whether the output signal is due to a 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]

As a means for solving the problem, since the flaw detection area of the subject to be inspected is well known, the arrival time area of the defect signal where the reflected signal of the ultrasonic wave from the defect in the area returns is the sound velocity and the ultrasonic wave. It is easier to find than the propagation distance. Therefore, n gates are provided in the time region corresponding to the target flaw inspection range. M comparators per gate,
FF (flip-flop), counter (output signal only when continuously counting up to a set number of times) are provided, OR circuit that takes the logical sum of these n × m counter outputs, and the detection signal is the defect detection time. (Time after reaching the set count) Hold circuit for extending the weight, circuit for weighting the output signal (circuit for setting the output voltage corresponding to the comparator reference voltage V _k when the counter k satisfies the count condition), One-shot multi-circuit to extend the detection signal time to the length of the defect (extends the detection signal for the time up to the set count value), and the gate timing signal based on the trigger signal from the flaw detector It is characterized by having a time base circuit for controlling the reset signal depending on the presence or absence of the reset signal.

[Action]

As described above, the present invention outputs a defective signal only when there is a signal that passes through the gate a predetermined number of times continuously and exceeds a preset level, so that erroneous detection due to noise can be eliminated. . If a defect is generated, it will always enter the gate continuously, but in the case of noise, it is extremely unlikely that it will be introduced multiple times in succession. In other words, if the N value of the maximum number of consecutive noises is checked and the setting is made (N + α) times, the signal counted beyond this value is nothing but a defect. With this device, the detectability and resolution of defects can be improved by increasing the repetition frequency of the transmitted wave, and it is also applicable when the subject is moving, but the moving speed is increased and the resolution of the set number of times is increased. In order to keep it constant, it is possible to easily cope with it by increasing the repetition frequency for emitting the transmission wave.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. FIG. 4 (a) shows the received signal of the electromagnetic ultrasonic flaw detector, and FIG. 4 (b) shows the detected waveform of the conventionally used received signal. A and C are transmitted waves, and B and D are reflected waves due to defects. (C) represents the gate timing signal of each gate obtained by dividing the range of the inspection region of the object to be inspected by a plurality of gates, and the gate widths Δt ₁ , Δt ₂ ,.
At Δt _k , ... Δt _n (all may be equal), the trigger signal from the flaw detector in (d) is delayed by t ₁ , t ₂ , ..., T _k , ... t _n , and gate channels G ₁ , G ₂ ,…, G _k ,… G _n are opened in order and signals are taken in order. A tone burst wave such as A in (a) is oscillated in synchronization with the trigger signal in (d), and an ultrasonic wave is generated in the subject every 1 / _r (sec). However, the repetition frequency is _r (Hz). Figure 2 shows the reflected wave F
The detection waveform when the noise E is superimposed on is shown. With such a waveform, it is impossible to determine the presence or absence of a defective signal due to noise. However, the probability that impulse noise is continuously superimposed a plurality of times at such timing sharply decreases as the set number of times increases. FIG. 3 shows the reference voltage level for the defect reflection in the comparison section. In this figure
It sets m different reference levels from V _{1 to} V _m .

FIG. 1 shows a block diagram of the flaw detection system. Gates G _{1 to} G _n
The detection waveform of the flaw detection output signal that passes through V ₁ to V
Enter m comparators CP with a reference voltage of V _m . For example, as shown in FIG. 3, the counter (CO) 1 to the counter (CO) k counts 1 at the gate having a signal exceeding V _k (the flip-flop FF in front of the counter CO counts at 1 repetition cycle). To limit the number to one). At this time, the k counters CO that have counted 1 are the time base circuits T
A counter reset prevention signal is issued to the counter G to prevent the counter (CO) 1 to counter (CO) k of the gate G from being reset by the trigger signal to prepare for the next repetition cycle.
If a signal of the same level enters the same gate G in the next repetition cycle, the counter (CO) 1 to the counter (CO) k count 2 as before. If nothing comes in, the counters (CO) 1 to (CO) k will all return to zero count without issuing any counter reset blocking signal. In this way, the set number (N + α) described in the action section
When the number of times (α is a safe number) is exceeded, the counter outputs output signals, but these outputs enter the OR circuit OR. Therefore, the hold circuit HD turns on immediately. When the counter CO counts up to the set number of times, it returns to count 0, but after that,
When a signal exceeding V _k continues to enter the comparator CP, this hold circuit HD holds the detection signal. Counter co
If the counter does not count up and the counter reset blocking signal is no longer output, a reset signal is generated and the counter
CO is reset and the hold circuit HD finishes holding. Next, the output of the hold circuit HD enters the weighting circuit W which outputs the detection voltage corresponding to the counter (CO) k. Further, the output signal of the weighting circuit W is sent to the one-shot multi circuit M. This one shot multi circuit M
Is stretched draw detection signal by (N + α-1) × 1 / f r,
The detection output corresponds to the actual defect length and diameter. As described above, even when the object is moving, the detection signal corresponding to the diameter and length of the defect can be output while eliminating the influence of noise. Incidentally, the n, m, V _k can vary the set value depending on the operating conditions and the like. Finally, FIG. 5 shows a time chart when N + α = 4 (the counter is assumed to count six times in succession). When the set number N + α of the counter CO is “4” as described above, the counter CO counts the signal output from the comparator CP through the flip-flop FF four times as shown in FIG. Output to the hold circuit HD via the OR circuit OR. The hold circuit HD is
When the defect detection signal is output 6 times in succession, the signal output from the counter CO is counted for 3 counts, that is,
Hold for (1 / f _r ) × 3 time. The output signal of the hold circuit HD is weighted by the weighting circuit W corresponding to the counter (CO) k, and the one-shot multi-circuit M
Sent to. As shown in FIG. 5, the one-shot multi-circuit M extends the time width of the input signal by (1 / _fr ) × (4-1) according to the set number of the counter CO, and according to the above weighting. The signal of different level is output as the defect detection signal. The time width of this defect detection signal is (1 / f _r ) × 3
+ (1 / _fr ) × (4-1), which corresponds to the length of the defect.

[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 where impulse disturbance noise and the like are generated, and at the same time, the object or the electromagnetic ultrasonic transducer can be removed. Even when the side moves, the size and length of the defect can be output by voltage output or the like, and the size and length of the defect can be easily evaluated from the recorded data of the 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 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 reference voltage setting diagram of a comparator. 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.

Claims (1)

(57) [Scope of utility model registration request] 1. A plurality of gate circuits divided into ranges corresponding to an inspection region of an object to be inspected after a signal output detected as a reflected wave of an ultrasonic pulse is rectified by a detection circuit by half-wave or full-wave. Supply a plurality of comparators with different reference voltages for each gate circuit, pass a gate circuit for each repetition frequency, provide a counter to count the number of signals exceeding the reference voltage, and set a preset number of times. The defect signal is output under the condition that the number of consecutive counts for N is large, whereby noise and defect are identified, and the output of the comparator is input to the weighting circuit to determine the size of the defect. Further, the present invention is characterized in that the length of the defect is supplied to the recording device by the one-shot circuit and the hold circuit for extending the time defect signal proportional to the count setting number N, and only the defect signal is output. Ultrasonic flaw detector.