JPH0629722Y2 - AE measuring device - Google Patents

Description

Detailed Description of the Invention A. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AE (acoustic emission) measuring device, and more particularly to an AE measuring device suitable for use in repeated tests.

B. 2. Description of the Related Art In order to accurately measure the fatigue state of a member to be inspected by measuring the AE wave generated in the member to be inspected in a repeated test,
AE at which phase of the repeated stress applied to the inspected member
It is necessary to determine whether a wave is generated or to measure the stress value when the AE wave is generated. In the conventional AE measuring devices, the excitation waveform voltage signal corresponding to the repeated stress applied to the inspected member by the shaker is input to a plurality of comparators having different reference voltages, and the repeated stress is thereby obtained. By setting the level region, it is measured at which stress level region the AE wave starts to occur.

C. Problems to be Solved by the Invention Such a conventional AE measuring device requires a plurality of comparators, and the circuit becomes complicated. In addition, whether the AE wave is generated at the rise of the repeated stress or not Sometimes it cannot be discriminated whether the AE wave is generated.

D. Means for Solving the Problems The AE measuring device according to the present invention is an oscillator that outputs a pulse having a frequency proportional to the frequency of repeated stress applied to a member to be inspected, and a detection that detects a reference position of each cycle of repeated stress. Means, a counter that starts counting the pulses in response to detection of the reference position, a sensor that detects an AE wave in the member to be inspected and outputs an AE signal, and the sensor when the AE signal rises. A reading unit for reading the count value of the counter.

E. Function In the present invention, the oscillation frequency of the oscillator is increased as the frequency of the repeated stress increases, and the output pulse is counted by the counter. The detecting means detects the reference position of each cycle of the stress signal, and in response to the detection, the counter starts counting the output pulses and the reading means reads the count value at the rising edge of the AE signal.

F. Embodiment FIG. 1 shows an embodiment of the present invention in which a stress signal is input to one terminal of a comparator 1. The stress signal is a voltage level signal corresponding to the amplitude and frequency of the repeated stress applied to the member to be inspected, and is, for example, the second signal.
As shown in the figure (a), the maximum stress σmax and the minimum stress σ
It is a voltage signal that repeats at an amplitude according to min and a frequency according to the frequency of the repeating stress. Comparator 1
A threshold voltage signal TH is input to the other terminal of the.
One-shot multi-vibrator 3 for comparator 1.
, And its output is input to the reset terminal of the counter 5. An oscillator 7 that outputs a pulse signal having a frequency corresponding to the frequency of the repeated stress is connected to the counter 5, and the counter 5 is further followed by a latch 9. The oscillator is a digital-analog converter (D
/ A converter) 7a and a voltage controlled oscillator (V / F converter) 7b. An AE sensor 11 that detects an AE wave and outputs an AE signal is connected to the latch 9, and the latch 9 responds to the incoming AE signal in response to the AE wave from the AE sensor 11. Is configured to be latched and output.

On the other hand, the stress signal is an analog-digital converter (A /
The D converter) 13 is also input and converted into a digital value, and the digital value is sequentially supplied to the microprocessor 15. The latch 9 is also connected to the microprocessor 15, and the microprocessor 15 is followed by a data recorder 17.

A switch 19 for setting a repetition frequency is also connected to the microprocessor 15, and the repetition frequency set by the switch 19 is converted by the microprocessor 15 into predetermined binary data. A D / A converter 7a is connected to the microprocessor 15 so that the conversion data regarding the frequency of the repeated stress is converted into an analog signal and output to the V / F converter 7b. As a result, the output pulse of the V / F converter 7b increases as the frequency of the repeating stress, that is, the frequency of the stress signal increases. For example, when each cycle of the stress signal is divided into 360, specifications such as conversion in the V / F converter 7b and the microprocessor 15 are determined so that an oscillation frequency 360 times the stress signal frequency can be obtained. Good.

The operation will be described with reference to FIGS. 2 (a) to 2 (d).

When the stress signal shown in FIG. 2A is input to the comparator 1, the comparator 1 outputs a high level signal to the one-shot multivibrator 3 only while the stress signal is larger than the threshold value TH. The rising of the high level signal of the comparator 1 triggers the multivibrator 3 to obtain a one-shot pulse at the times t1 and t2. As shown in FIG. 2 (d), the counter 5 is reset by the one-shot pulse and its content becomes "0". Then, in response to the pulse from the oscillator 7, the counter 5 advances by "+1" as shown in FIG. 2 (d). When the AE signal is output from the sensor 11 at time t3 in FIG. 2 (c), the contents of the counter 5 are latched at the start of rising thereof (see FIG. 2 (d)). Therefore, the count value itself of the counter 5 latched by the latch 9 is the AE
It indicates the phase information of the repeating stress at the time when the wave is generated. For example, if each element is set so that the oscillation frequency of the oscillator 7 is 360 times the stress signal frequency, when the repeating stress is set to a frequency of 1 Hz, the frequency of the output pulse of the oscillator 7 is 360 Hz, , The counter value of the counter 5 is 90 when the maximum stress σmax is reached, and is 270 when the minimum stress σmin is reached.
Further, when the frequency of the stress signal is set to 5 Hz, the frequency of the output pulse becomes 1.8 KHz, so the count values at σmax and σmin do not change. Therefore, even if the repeating stress frequency becomes large, the separability of the phase detection at the rising of the AE wave does not change.

The frequency input switch 19 for repeated stress may be directly connected to the D / A converter 7a as a digital switch. Of course, the switch 19 may be configured like a variable resistor so that its output voltage is directly input to the voltage controlled oscillator 7b. In those cases, depending on the desired resolution. Set each device.

In this embodiment, the starting point of each cycle of the stress signal is set as the reference position, but the starting point of each cycle is not limited and the intermediate point may be set as the reference position.

G. Effect of the Invention According to the present invention, the oscillation frequency of the oscillator is changed according to the frequency of the repeated stress, the number of oscillation pulses from the reference position during one cycle of the repeated stress is counted, and the count value at the time of generation of the AE wave is calculated. By reading, the phase of each cycle in which the AE wave is generated is measured.
Even if the frequency of repeated stress increases, the resolution as a count value can be maintained at a desired accuracy, and accurate measurement can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS. 2 (a) to 2 (d) are waveform diagrams showing output waveforms of respective parts thereof. 1: Comparator 3: One-shot multivibrator 5: Counter 7: Oscillator 7a: Digital-analog converter 7b: Voltage controlled oscillator 9: Latch 11: Sensor 13: Analog-digital converter 15: Microprocessor 17: Data recorder 19: Switch

Claims (1)

[Scope of utility model registration request] 1. An oscillator that outputs a pulse having a frequency proportional to the frequency of repeated stress applied to a member to be inspected, and a detection unit that detects a reference position of each cycle of repeated stress.
A counter that starts counting the pulses in response to the detection of the reference position, a sensor that detects an AE wave in the member to be inspected and outputs an AE signal, and a counter that counts when the AE signal rises. An AE measuring device comprising: a reading unit for reading a numerical value.