JPH067124B2 - Ultrasonic flaw detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic flaw detector for inspecting internal defects in materials or products, and particularly to the vicinity of the surface of an object such as a metal material, ceramics, IC or an ultrathin material. It is a flaw detection device suitable for inspecting minute defects existing in the.

[Conventional technology]

Conventionally, in materials or industrial products, it has been conventional to detect internal defects of so-called thin materials with a small thickness and defects existing near the surface of the subject (hereinafter referred to as surface layer defects) even if the thickness is not so thin. It has been widely implemented in various technical fields. Further, the flaw detection is required to reliably detect surface defects and fine defects closer to the surface in order to exert significantly higher performance and functions as compared with conventional ones for new materials and electronic products. Is coming. A conventional general flaw detector will be described with reference to FIGS. FIG. 5 is an explanatory view of the structure of the flaw detection device, 1 is a water tank filled with water 2, 3 is a thin material test object installed at the bottom of the water tank 1, and 4 is a probe immersed in water 2. is there. 5 is a probe 4
A pulse transmission circuit for transmitting an ultrasonic pulse to the object, 6 is an RF of a reflected wave reflected from the surface, defect and bottom of the subject 3.
A receiving circuit for receiving and amplifying a signal via the probe 4, 7 '
Is a peak detector that detects the peak value of the reflected wave amplified by the receiving circuit 6 and outputs a DC voltage proportional to the value, and 8 is an oscilloscope that displays the waveform output from the peak detector 7 '. FIG. 6 is a main block circuit diagram of the peak detector 7 ', in which 9 is an input circuit to which the RF signal of the reflected wave amplified by the receiving circuit 6 is input, 10 is a trigger circuit, and 11 is a delay trigger pulse. Delay trigger threshold setting circuit to set the rising threshold,
12 is a monitor circuit that outputs the output signal of the gate control circuit 18 to the oscilloscope 8, 13 is a monitor synchro circuit, and 14 is a delay trigger that operates when the level of the transmission pulse of the probe 4 exceeds the threshold value. Delay trigger circuit to set the pulse width of the, 15 is a delay circuit to set the pulse width of the delay, 16 is a gate circuit that can set the pulse width of the gate to any position and width, both multivibrator 17
And forms a gate control circuit 18 for adjusting the delay trigger, delay and gate pulse widths. Reference numeral 19 is an RF detection circuit for detecting the RF signal output from the input circuit 9, 20 is an output signal of the RF detection circuit 19 converted into a DC voltage proportional to its value, and until the gate signal of the gate control circuit 18 is closed. The peak detection circuit stores the value, and 21 is an output circuit that outputs the DC voltage. FIG. 7 is a characteristic diagram of a pulse generated when the flaw detector is used. In the figure, (a) is an example of an echo pattern of a reflected wave from the subject 3, T is a transmission pulse,
S is a surface echo, F is a defect echo, and B is a bottom echo. L is a line indicating the threshold value of the level of the transmission pulse T. (b) is the pulse width P _{t of} the delay trigger set by the delay trigger circuit 14, (c) is the pulse width P _{d of the} delay set by the delay circuit 15, and (d) is the gate set by the gate circuit 16. Of the pulse width P _g .

Level of the transmitted pulse T which is emitted from the probe 4 is immediately actuated to delay the trigger circuit 14 it exceeds the set threshold L, the pulse width P _t of the delay trigger is set. Then, when the surface echo S exceeds the threshold value L, the delay circuit 15 and the gate circuit 16 are activated to start the sequence, and the pulse width P _{d of the} delay is closed and the gate is opened at the same time, and the set pulse width P _{g is set.} Close after a lapse of time.

By the way, the minimum pulse widths P _d and P _g that can be set in the current delay circuit 15 and the gate circuit 16 in the multivibrator 17 are about
80 ns, and the propagation delay time of the multivibrator 17 is about 40 ns on average, although it varies depending on the configuration of the device.
Therefore, the delay pulse width P _d between the rise of the delay pulse at the threshold value L of the display echo S shown in FIG. 7C and the rise of the gate pulse of the next FIG. The minimum value is about 120 ns, and the defect echo F of the defect approaching within the propagation distance of the pulse corresponding to this time is shown in the same figure.
It cannot appear within the pulse width P _{g of the} gate shown in (d). The propagation distance is, for example, about 350μ in the case of steel materials.
m, the distance from the surface of the object 3 to the defect is about 350.
If it is not more than μm, the defect echo F has a gate pulse width P.
cannot appear within _g . As described above, in the circuit configuration, the defect echo F may appear within the pulse width P _{g of the} gate in flaw detection in the case of a thin material in which the thickness of the subject 3 is a certain thickness, for example, about 1 mm or more. However, in the case of inspecting a fine surface layer defect very close to the surface of the subject 3 or a fine defect existing in a very thin material such as a subject having a thickness of about 200 to 300 μm, the surface echo S is the defect echo F.
Appear very close to each other, so that the defect echo F cannot appear within the pulse width P _{g of the} gate.
Further, in the case where the object 3 is the steel material and the distance from the surface to the defect is 350 μm or more, and the defect echo F appears within the pulse width P _{g of the} gate,
For the surface layer defect at a distance close to the surface that appears within the propagation delay time, the gate is not actually gated for the above reason, and neither defect echo F can be detected. Therefore, the surface layer defect at such a position or the defect existing in the ultrathin material cannot be detected despite the existence of the defect.

[Problems to be solved by the invention]

As described above, in the conventional ultrasonic flaw detector, the minimum pulse width that can be set by the delay circuit or gate circuit is about 80 ns.
Therefore, it is impossible to detect the surface layer defect of the object and the defect existing in the object of the ultra-thin material. In addition, since it was not possible to gate only the defect echo at any desired depth, there was a problem that each defect could not be detected when multiple defects were present close to each other in the thickness direction. Was there.

The present invention solves the above-mentioned problems of the prior art, and enables the inspection of an object and a surface layer defect of an ultra-thin material, and at the same time, it has a plurality of defects existing in proximity in the thickness direction. Even if it exists, it aims at providing the ultrasonic flaw detector which can detect each defect arbitrarily.

[Means for solving problems]

The present invention relates to a pulse transmission circuit that is connected to a probe facing a subject in a liquid tank and applies a transmission pulse, a reception circuit that receives an RF signal of a reflected wave from the subject, and a pulse of a delay trigger. Delay trigger circuit that sets the width, delay circuit that sets the pulse width of the delay after the delay trigger pulse is closed, delay trigger threshold setting circuit that sets the threshold for raising the delay trigger and delay pulse, setting A trigger circuit that issues a trigger signal when the transmission pulse or the echo level of the reflected wave from the object exceeds the threshold value
And an input circuit to which each circuit of the gate circuit that sets the pulse width of the gate is connected to a multivibrator that generates a pulse set in each of the circuits, and to which the RF signal received by the receiving circuit is input, and A peak detector for outputting a voltage proportional to the peak value of the detected RF signal, and an oscilloscope for displaying the output waveform of the peak detector, having an RF detection circuit for detecting the RF signal output from the input circuit; In the provided ultrasonic flaw detector, when the transmission pulse exceeds the threshold value, it operates by the trigger signal output from the trigger circuit and delays the RF signal output from the input circuit by an arbitrarily set time. An RF delay circuit for
Since the peak detector having a configuration for inputting a signal to the RF detection circuit is provided, it is possible to detect not only an inspection target of an ultrathin material and surface layer defects but also a plurality of internal defects that are close to each other in the thickness direction. This is an ultrasonic flaw detector that is capable of

[Action]

When the level of the transmission pulse emitted from the probe exceeds the set threshold value, the delay trigger circuit operates to set the pulse width of the delay trigger, and subsequently, when the surface echo S exceeds the threshold value, The delay circuit and the gate circuit are activated to start the sequence of outputting each pulse of the delay and gate of the set pulse width. On the other hand, the RF received by the receiving circuit
The signal is input to the RF delay circuit through the input circuit, and the RF delay circuit operates by the trigger signal output from the trigger circuit at the same time when the level of the transmission pulse exceeds the threshold value, and the RF delay circuit operates in the circuit. The input RF signal is the input R signal
A delay terminal is selected and delayed for a desired time so that a defective echo of the F signal appears within the pulse width of the gate, and the delayed signal is output.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. In the figure, the same reference numerals as those in FIGS. 5 to 7 indicate the same elements. FIG. 1 is a main block circuit diagram of the peak detector, FIG. 2 is a characteristic diagram thereof, FIG. 3 is a diagram showing a concrete configuration example of an RF delay circuit, and FIG. 4 is a characteristic diagram thereof.

Reference numeral 22 is an RF delay circuit to which the RF signal received by the receiving circuit 6 is inputted via the input circuit 9. The circuit 22 outputs the signal from the trigger circuit 10 when the level of the transmission pulse T exceeds the threshold value L. It is a circuit that operates by a trigger signal, delays the RF signal by an arbitrarily set time, and outputs it so that the defect echo F appears in the gate pulse. Reference numeral 7 is a peak detector having the above circuit configuration. R in Figure 3
An example in which an inductor is used as the F delay circuit 22 is shown. In this case, the delay time in the RF delay circuit 22 depends on the number of coil turns, that is, the inductance H and the conductance C. Therefore, by providing multiple taps in the coil, It can be arbitrarily selected within the range. Figure 4 is the third
FIG. 4 is a characteristic diagram showing a state of delay corresponding to a plurality of delay terminals shown in the figure, in the case where three terminals a, b, and c are sequentially provided from an input terminal IN to an output terminal OUT.
As the number of coil turns increases Therefore, the waveform of the RF signal is shown in Fig. 4 (I
Time t _d1 shown from the position shown in N) to the terminal a drawing (a)
The output terminal O
In the UT, the position is delayed by the time t _dout . Therefore, the delay time can be arbitrarily set by selecting the terminal.

As described above, in the surface layer defect or the defect existing in the ultra-thin material, the defect echo F appears very close to the surface echo S, and as an example, an echo pattern as shown in FIG. Become. When the level of the transmission pulse T emitted from the probe now exceeds the threshold value L, the delay trigger circuit 14 operates to set the delay trigger pulse having the pulse width P _t shown in FIG. 2 (b), When the surface echo S exceeds the threshold value L after the time t _S, the delayed pulse having the pulse width P _d set by the delay circuit 15 and shown in FIG. Then, at the same time as the delay pulse width P _d is closed, the gate pulse having the pulse width P _g shown in FIG. However, in this way, at the same gate pulse output position as in the prior art, as shown in the figure, the positional deviation cannot be applied to the gate as in the prior art. Therefore, as shown in (e) of the figure, the level of the transmission pulse T exceeds the threshold value L, and at the same time, the trigger signal (pulse width P _T ) output from the trigger circuit 10 activates the RF delay circuit 22, R
The waveform of the F signal is delayed by the time t _d set by the circuit 22 and output. Therefore, the surface echo S is the threshold value L
Position of over becomes the position of the time _{t S} and RF delay circuit time set by the 22 _{t d} and the sum of the time _(t S + t _d),
The defect echo F can appear within the pulse width P _{g of the} gate.

The time t _d can be arbitrarily set by the echo patterns of the surface echo S and the defect echo F, the pulse width P _{d of the} delay set according to the echo pattern, the pulse width P _{g of the} gate, and the like. Of course, for a single defect in which the echo S and the defect echo F appear close to each other,
Even when a plurality of defects are closely present in the thickness direction of the subject, it is possible to arbitrarily gate only one of the defect echoes. For example, defect echo F ₁ , F
_In the case of an echo pattern in which ₂ and F ₃ are close to each other, the delay terminals are sequentially selected from a and the corresponding time t _d
By setting, it is possible to detect defects by sequentially applying the defects to the gate.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, the present invention provides an ultrasonic flaw detector including a pulse transmitting circuit and a receiving circuit connected to a probe facing a subject in a liquid tank, a peak detector and an oscilloscope, and the peak detector. Within
Since an RF delay circuit that operates by the trigger signal output from the trigger circuit when the transmission pulse exceeds the set threshold value and delays the RF signal by an arbitrarily set time is provided, Enables flaw detection of the subject and surface defects to a shallow position, which was not possible in the past, and also enables multiple flaws existing in close proximity in the thickness direction of the subject, and also performs flaw detection with high accuracy. It has an excellent practical effect that makes it possible.

[Brief description of drawings]

1 to 4 are explanatory views of an embodiment according to the present invention, and FIG. 1 is a main block circuit diagram of a peak detector,
FIG. 2 is a characteristic diagram thereof, FIG. 3 is a diagram showing a concrete configuration example of the RF delay circuit, and FIG. 4 is a characteristic diagram thereof. FIG. 5 is an explanatory view of the structure of the ultrasonic flaw detector, FIG. 6 is a main block circuit diagram of a conventional peak detector, and FIG. 7 is a characteristic diagram thereof.

Claims (2)

[Claims] 1. A pulse transmission circuit connected to a probe facing a subject in a liquid tank, for applying a transmission pulse, a receiving circuit for receiving an RF signal of a reflected wave from the subject, and a delay trigger. Delay trigger circuit that sets the pulse width, delay circuit that sets the pulse width of the delay after the delay trigger pulse is closed, delay trigger threshold setting circuit that sets the delay trigger and the threshold for raising the delay pulse, A trigger circuit that generates a trigger signal when the transmission pulse or the echo level of the reflected wave from the subject exceeds the set threshold value.
And an input circuit to which each circuit of the gate circuit that sets the pulse width of the gate is connected to a multivibrator that generates a pulse set in each of the circuits, and to which the RF signal received by the receiving circuit is input, and A peak detector for outputting a voltage proportional to the peak value of the detected RF signal, and an oscilloscope for displaying the output waveform of the peak detector, having an RF detection circuit for detecting the RF signal output from the input circuit; In the provided ultrasonic flaw detector, when the transmission pulse exceeds the threshold value, it operates by the trigger signal output from the trigger circuit and delays the RF signal output from the input circuit by an arbitrarily set time. An RF delay circuit for
An ultrasonic flaw detector comprising a peak detector configured to input a signal to the RF detection circuit. 2. The ultrasonic flaw detector according to claim 1, wherein the RF delay circuit is an inductor.