JPS5922180B2 - Defect position locating device using AE signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an apparatus for detecting an AE signal (acoustic/machining signal) generated from an object to be measured and locating a defect position in the object to be measured.

When a conflict acts on a solid material, an AE signal is emitted from the defect location and propagates through the solid material.

By applying this phenomenon, we can monitor the progress of various defects that occur during the operation of structures such as reactor pressure vessels and primary cooling system piping, and constantly diagnose their health to ensure the safety of these structures. can be ensured. Conventional defect position locating technology using AE signals detects the AE signal with a set of AE signal converters attached to the object to be measured.
The time difference between the two AE signal converters is measured based on the point at which the signal exceeds a certain threshold voltage at the rising edge of the signal, and the generation of the AE signal is calculated from the relationship with the AE signal propagation speed in the object under test. . By the way, when the object to be measured is a large structure such as a nuclear reactor vessel or primary cooling system piping, the propagation distance of the AE signal becomes long, and as a result, the amplitude of the propagated AE signal is only attenuated. Instead, it separates into two or more waves such as longitudinal waves and transverse waves. For AE signals with such dull waveforms, it is difficult to set the threshold voltage using the conventional method that uses the point at which the threshold voltage is exceeded as a reference, and when a longitudinal wave with a fast propagation speed exceeds the threshold voltage, the propagation speed The problem was that the slow transverse waves of the waveforms irregularly exceeded the threshold voltage, reducing measurement accuracy. 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 a defect position locating device using an AE signal with small measurement errors.

The present invention has a set of AE signal converters, introduces the AE signals from the converters into respective peak hold circuits, and guides the peak-held signal for a predetermined fixed period of time to a time difference measuring circuit. The time difference is determined using the fall position of the signal as a reference, and the AE signal is guided to the arrival order discrimination circuit, and the defect position is located by the signal from the time difference measurement circuit and the signal from the arrival order discrimination circuit. This is a defect position locating device using AE signals.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, and is an example applied to a case where the object to be measured is a one-dimensional structure. A pair of AE signal converters 2a and 2b are pasted at appropriate locations on both ends of the object to be measured 1. The output from each AE signal converter 2a, 2b is output to an amplifier/filter 3a, 3, respectively.
After being connected to b and peak hold circuits 4a and 4b,
The signal is guided to a time difference measuring circuit 5 and further sent to a signal position calculation device 6. Further, the outputs from the amplifier/filters 3a and 3b are sent to the arrival rank discrimination circuit 7, and further sent to the signal position calculation device 6. Next, the operation of this device will be explained.

It is assumed that there is a defect at point D of the object to be measured 1 (a point close to the AE signal converter 2a). When an external force is applied to the object to be measured 1, an AE signal is generated from the defect D and propagates through the object to be measured. This mechanical AE signal is converted into an energy signal by AE signal converters 2a and 2b. The outputs from the AE signal converters 2a and 2b are shown in Figure 2 A and b, and since the defect D is closer to the converter 2a, the AE signal appears earlier in the converter 2a, and Since the distance between the defect D and the transducer 2b is long, the AE signal appearing on the transducer 2b is separated into a longitudinal wave component with a fast propagation speed and a transverse wave component with a slow propagation speed. The signals thus obtained are sent to amplifier/filters 3a and 3b, respectively. Amplify as appropriate by the amplifier section,
The filter section attenuates relatively large low frequency components of environmental noise, improving the S/N ratio of the AE signal. The AE signal thus obtained is sent to peak hold circuits 4a and 4b.
sent to. The peak held signal waveform is shown in Figure 2C,
Shown in d. The dotted line is the AE signal. A peak hold circuit holds the highest level of an input signal for a certain period of time, and the optimum value of the holding time varies depending on the size of the object to be measured. The retention time is set to be larger than the maximum time difference between the longitudinal wave component and the transverse wave component so that even if the AE signal propagates over a long distance and separates into two or more waves as shown in Figure 2d, the transverse wave component can always be detected. put. Using the falling part of the peak hold signal obtained in this way as a reference for measurement, the time difference measurement circuit 5 generates a time difference signal e in Figure 2, and measures the time difference between the AE signals that have reached both AE signal converters. be. This time difference can be measured by using, for example, the time difference signal shown in FIG. 2e as a gate signal, controlling the output from an oscillator that oscillates at a constant frequency, and counting by a pulse counter. Next, the arrival order discrimination circuit 7 determines which transducer the AE signal reached first, and thereby determines whether the defect is closer to the transducer 2a or 2b. can be determined. Information regarding the arrival time difference and information regarding the arrival order are sent to the signal position calculation device 6,
The generation position of the AE signal is calculated from the relationship with the E signal propagation velocity. Additionally, malfunctions can be expected if noise happens to occur immediately before or after the AE signal, but errors due to noise can be statistically eliminated by performing long-term measurements and accumulating data. be able to. Although this example is applied to a case where the object to be measured is a one-dimensional structure, the same can be applied to a two-dimensional structure by installing three to four AE signal converters. Needless to say, it is possible to locate the defect position. This invention (as mentioned above, since it is configured to measure the arrival time difference of the AE signals reaching a set of AE signal converters using the peak voltage position of the AE signals as a reference, it is possible to Even when the signal propagation distance is long and the waveform is distorted, the arrival time difference can be measured accurately, and errors in defect position location can therefore be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a defect position locating device according to an embodiment of the present invention, and FIGS. 2 a to 2 e are operational waveform diagrams of the device shown in FIG. 1. 1...Plow to be measured, 2a, 2b...AE
Signal converter, 4a, 4b... Peak hold circuit, 5... Time difference measuring circuit, 7... Arrival rank discrimination circuit.

Claims (1)

[Claims] 1 has a set of AE signal converters, and the AE from the converters
Each signal is introduced into a peak hold circuit, and the signal whose peak is held for a predetermined period of time is led to a time difference measuring circuit, where the time difference is determined based on the falling position of the peak hold signal, and the AE signal is reached. A defect position locating device using an AE signal, characterized in that the defect position is guided to a rank discriminating circuit, and the defect position is located by a signal from the time difference measuring circuit and a signal from the arrival rank discriminating circuit.