JPS5822702B2 - Accorstates query detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an acoustic emission (hereinafter abbreviated as AE) detection device, and more particularly to a detection device suitable for removing noise having a frequency characteristic different from that of a signal.

The AE measurement method is a method of receiving elastic waves generated by materials or structures themselves to evaluate the strength of the test objects, inspect for defects, etc.

In this measurement, there is a conventional problem of how to distinguish noise generated during measurement from a signal.

As a method for removing this noise, a method of identifying the signal and the noise using the difference in their characteristics is used.

For example, when there is a significant difference in frequency characteristics, discrimination means using a frequency filter has conventionally been used.

The conventional system using this frequency filter will be explained with reference to FIG.

The figure shows a case in which crack growth is monitored by AE measurement in a tensile fatigue test, and it is assumed that the test piece 1 is installed on a jig 4.degree. 5 via pins 2 and 3.

The jig 4 is fixed, and a tensile load is repeatedly applied to the jig 5.

A sensor 6 for detecting the AE multiplied signal is installed on the test piece 1, and its output voltage is amplified and impedance-converted by a preamplifier T, passed through a filter 8, further amplified by a main amplifier 9, and then sent to a signal processing circuit. 10
The signal is subjected to signal processing and output to the recorder 11.

The filter 8 has a frequency filtering function for so-called noise removal.

Further, the signal processing circuit includes an AE effective value conversion circuit, an AE
It has functions such as an event generation circuit and an AE ringdown counting circuit.

In the case of such a tensile fatigue test, the notch part 1 of the test piece 1
As the crack propagates, a sudden type AE double signal 8 is generated from c, as shown in FIG. 2a.

Further, at this time, mechanical noise en as shown in FIG. 2A is often generated from the mounting portions of the pins 2 and 3 or the mounting portions of the jigs 4 and 5.

The amplitude and frequency characteristics of these AE multiplied signal noises vary depending on factors such as the shape, material, and size of the test piece and testing machine, but there are often characteristic differences between the signal and noise characteristics, and these can be Figure 3 shows an example of the frequency characteristics of so-called AE multiplied signal noise.

As shown in the figure, when the frequency component of the noise en is lower than that of the AE multiplied signal 8, the cutoff frequency fc is used to attenuate the noise to some extent by using an i-pass filter (HPF). However, e8 and e
As long as there is a frequency domain in which n overlaps, complete separation is impossible.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art as described above and to provide an acoustic emission detection device that effectively detects only the normal AE multiplied signal.

In order to improve the effect of removing noise that becomes an interference in AE measurement, the present invention provides a frequency filter that passes the AE multiplied signal frequency band, calculates the output ratio of the tear output signal and the non-sweep signal, and calculates the ratio This invention relates to a method of controlling an analog gate circuit based on the magnitude of coefficients and discriminating between signals and noise.

FIG. 4 shows an embodiment of the present invention, in which the output of the preamplifier 7 is divided into two groups, a numerator system and a denominator system. Consisting of a main amplifier 9a and a molecular detection circuit 12a,
The denominator system is a denominator main amplifier 9b and a denominator detection circuit 12.
Consists of b.

Comparison circuit 1 which inputs the output voltage Ea of the molecular system detection circuit and the output voltage Eb of the denominator system detection circuit into a division circuit 13 and discriminates whether it is a signal or noise based on the magnitude of the output voltage (proportionality coefficient).
4 (the applicant has an earlier application for this).

On the other hand, the molecular system detection output is input to the event generation circuit 15, and the output and the output of the comparison circuit 14 are input to the control signal generation circuit 1.
6 to create a control signal pulse.

Further, the output voltage of the molecular main amplifier 9a passes through a delay circuit 17 and is then applied as an input signal to an analog gate circuit 18, and the output pulse of the control signal generation circuit 16 is applied as a control signal to the analog gate circuit.

FIG. 5 shows a time chart for explaining the present invention in detail.

As you will see from next time, in the case of a signal, the divider circuit output E
Since a/Eb is larger than the comparison voltage Er, a control signal (A7) is generated, and the analog gate circuit output (A8)
A signal voltage is output.

On the other hand, in the case of "noise", the output of the divider circuit (Y5) is lower than the comparison voltage Er, so the control signal (A7) is not generated and is not output to the analog gate circuit (Y8).

In this manner, according to the present invention, signals and noise can be completely separated.

Next, a more specific example of the molecular detection circuit 12a, the event generation circuit 15, and the control number generation circuit 16 is shown in FIG.

The molecular detection circuit 12a is a half-wave or full-wave rectifier circuit 120.
, and a time constant circuit 121.

This circuit 12a obtains an envelope signal of the signal obtained through the molecular main amplifier.

The time constant circuit 121 has the role of a low-pass filter for removing high frequency components for detecting an envelope signal.

The event generation circuit 15 includes a comparison circuit 150 which inputs the envelope signal obtained from the detection circuit 12a, an AND gate 151, and a lid couple mono multivibrator (MM).
)152.

In the comparison circuit 150, the envelope signal and the reference signal vR
A signal having a higher level than the reference signal vR is waveform-shaped and output.

This reference signal VR is set to cut the low level signal of the envelope signal.

The output of comparison circuit 150 is applied to one input of AND gate 151.

The backclock signal CL is applied to the other input of the AND gate 151.
is inputting.

Therefore, the AND gate 151 outputs the clock signal CL only when the output of the comparison circuit 150 is present.

This output is input to MM152. The time constant (oscillation pulse width) of this IVIM is the pulse width T of the clock signal CL.

(To +ΔT).

The reason for this is that the output of the comparator circuit 150 may be intermittent, and if the intermittent time is short, it is recognized that the signal is in the signal identification period, and if it is long, it is recognized that the signal is in the next signal identification period. be.

The intermittent time is T+ΔT. As a result, when a comparison output is generated, then temporarily disappears, and then a comparison output is generated again, if the above-mentioned temporary comparison output does not occur, if the time is smaller than T + ΔT, one cycle is generated. The MMI 52 continues to generate outputs as the comparison outputs of .

However, the output of the MM 152 disappears for a time greater than T+ΔT, and the comparison period is recognized as having ended.

In any case, the output of the correct comparison period will be obtained from the MM.

Note that the true reason for setting T+ΔT is that the signal period is not necessarily constant, and when the signal period is a constant value, the above method is unnecessary.

Next, the control signal generation circuit 16 includes an AND gate 160, a differentiation circuit 161, a time difference detection circuit 162, and a flip-flop (FF) 163.

The output of the comparison circuit 14 and the output of the event circuit 15 are input to the AND gate 160 .

The output of the comparison circuit 14 generally has a slight time delay compared to the output of the event generation circuit 15.

Gate 160 produces a tt l pp ratio output when both signals are present.

This output triggers and sets flip-flop 163 on its rising edge.

Therefore, at the same time as the gate output is generated, the FF163 at
ln output is generated and the analog gate circuit 18 is switched on.

Next, we will explain how to reset the FF 163.

In the time difference detection circuit 162, the event output and the comparison circuit 1
4 is input, and the difference in rise time between the two is detected.

As described above, the event output occurs first, and the comparison output occurs after a slight delay.

This generation time difference is detected.

Furthermore, this detected time difference is stored. The detection circuit 162 is configured to start with the output of the differentiating circuit 162 and generate a trigger pulse after the time difference has elapsed.

Therefore, the counter is the main component.

Now, the differentiating circuit 161 only when there is a gate output,
The falling edge of the output of the event J north circuit 15 is differentiated.

The fall of the output is the time when the event output ends. Therefore, the detection circuit 162 resets the FF 163 after a time corresponding to the time difference after the end of the event output.

−Can be done.

The switch is turned on by the output of the FF 163, and the output of the delay circuit 17 in the on period passes through.

This passing signal is a regular signal as described above, and noise signals are cut off.

Note that the delay time of the delay circuit 17 is the sum of the circuit transmission delay and the time corresponding to the above-mentioned time difference, and therefore, the delay time can be controlled by the time difference detection circuit 162.

Note that there are cases where the time difference can be ignored, and in that case, the time difference detection circuit is unnecessary, and the FF 163 may be reset only by the fall of the event output.

As another embodiment, an even greater effect can be obtained by providing a noise filter whose passband is the noise frequency band before the denominator main amplifier shown in FIG.

Further, in the division circuit shown in FIG. 4, if the output voltage of the molecular type detection circuit and the output voltage of the denominator type detection circuit are respectively raised to powers, an even greater comparison effect can be obtained.

As described above, according to the present invention, the reliability of the data obtained is extremely high compared to the conventional method.
The effect is significant.

[Brief explanation of the drawing]

Fig. 1 is a diagram of a conventional example of AE measurement, Fig. 2 a sb is a waveform side diagram before and after 1-wave processing, Fig. 3 is a side diagram of frequency characteristics of the AE multiplied signal and noise, and Fig. 4 is an example of the present invention. Figure, 5th
The figure is an explanatory diagram for explaining the operation of FIG. 4, and FIG. 6 is a diagram of a more specific embodiment of the present invention. 6...Sensor, 7...Preamplifier, 12a...Molecular system detection circuit, 12b...Denominator system detection circuit, 15...
・Event conversion circuit, 16...control signal generation circuit, 18
...Analog gate circuit.

Claims (1)

[Claims] 1 A sensor that detects time-series acoustic emissions as an electrical signal, means for amplifying the sensor output and outputting it to the numerator system and the denominator system, respectively, and a signal corresponding to the frequency band of the signal using the sensor output as input. a molecular-based bandpass filter that only passes through the molecular-based bandpass filter, a molecular-based detection means that detects the output obtained through the molecular-based bandpass filter, a denominator-based detection means that detects the sensor output, and a molecular-based detection means that detects the sensor output. and a discriminator that divides the detection output of the denominator system detection means and the detection output of the denominator system detection means as input, and distinguishes between a signal and noise based on the magnitude relationship; circuit and
A gate that receives the output of the event generation circuit and the output of the discrimination means as input, and passes a signal obtained by amplifying the sensor output only when there is an event output that includes a time period in which the output of the discrimination means exists. An acoustic emission detection device comprising: a detection means for turning on and outputting, and extracting and detecting the outputted signal as a regular acoustic emission signal.