JPS5819987B2 - AE - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an apparatus for detecting an AE multiplied signal (acoustic emission signal) generated from an object to be measured and locating a defect position in the object to be measured. The present invention relates to an AE signal discrimination device that compares AE multiplied signal amplitude values obtained by a signal converter in consideration of propagation distance and outputs only appropriate position calculation results.

When an external force acts on a solid material, an AE multiplied signal is emitted from the defective location and propagates through the solid material.

Utilizing this acoustic emission 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, constantly diagnose their health, and Safety can be ensured.

Defect position locating using such an AE multiplied signal involves measuring the arrival time difference and arrival order of the AE multiplied signal to a set of AE signal converters attached to the object to be measured, and determining the AE signal from the relationship with the AE signal propagation speed. This is done by calculating the location of the occurrence.

By the way, the sound detected by the AE signal converter is A
It includes not only the E-fold signal but also various noises due to the measurement environment.
Therefore, in order to obtain high-quality analysis results, it is necessary to eliminate measurement errors caused by harsh noise.

This invention was made in view of the above-mentioned circumstances, and its purpose is to identify the signal of a defect position locating device using an AE multiplied signal so that the true defect position of the object to be measured can be located with high precision. The goal is to provide equipment.

This invention was made by taking advantage of the fact that when an AE multiplied signal propagates through an object under test, its amplitude attenuates according to a certain relational expression, and the difference in arrival time of the AE multiplied signal to a set of AE signal converters is In the apparatus for locating the AE multiplied signal generation position from This is a signal discriminating device that is installed in a comparator circuit to compare the values, and outputs a position calculation result only when the values are approximately equal.

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

The drawing is a block diagram of an embodiment of the present invention, and is an example in which the object to be measured is a one-dimensional structure.

A pair of AE signal converters 2a are installed at appropriate locations on both ends of the object to be measured 1.
, 2b are attached.

The output from each AE signal converter 2a, 2b is an amplifier/filter 3a, 3b and a peak hold circuit 4a, respectively.
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 amplifiers/filters 3a and 3b are sent to the arrival order discrimination circuit 7, and the signal regarding the arrival order is sent to the signal position calculation device 6.

The AE multiplied signal amplitude voltage from the peak hold circuits 4a and 4b and the AE signal position information from the signal position calculation device 6 are sent to the attenuation correction calculators 7a and 7b, and the output thereof is led to the comparator circuit 8. The output from 8 controls the output of the position calculation results.

Next, the operation of this device will be explained.

Assuming that there is a defect at point D (point near the transducer 2a) of the object to be measured 1, the AE multiplied signal generated at the point D propagates through the object to be measured.

This mechanical AE multiplied signal is converted into an electrical signal by the AE signal converters 2a and 2b, but since it is assumed that the defect is near the converter 2a, it is faster to convert the signal to the converter 2a.
The AE multiplied signal will appear.

The AE multiplied signals thus converted into electrical signals are sent to the amplifier/filters 3a and 3b, respectively.

The amplifier section amplifies the minute AE multiplied signal to an appropriate amplitude,
The filter section attenuates relatively large low frequency components of environmental noise, improving the AE multiplied signal S/N ratio.

The thus obtained AE multiplied signal peak hold circuit 4a
, 4b.

The peak hold circuits 4a and 4b are circuits that have the function of holding the highest level of the input signal for a preset period of time, and use the falling part of the peak hold signal obtained in this way as a reference for measurement. A time difference measuring circuit 5 measures the time difference between the falling edges of both peak hold signals.

Next, the arrival order discrimination circuit 7 determines which converter the AE multiplied signal reaches first, and thereby determines whether the defect is closer to the converter 2a or closer to the converter 2b. be able to.

The above information regarding the arrival time difference and the information regarding the arrival order are sent to the signal position calculation device 6, and the AE multiplied signal generation position is calculated from the relationship with the AE signal propagation speed.

In principle, it is possible to locate the defect location using the above device, but as mentioned above, it is necessary to avoid mixing the electrical signal detected by the transducer with the true AE multiplied signal environmental noise generated from the defect. Therefore, there is no guarantee that the peak held signal is always the true AE multiplied signal.

If the peak-held signal is based on environmental noise, it is obvious that the defect location determined by the peak-held signal is incorrect.

By the way, the amplitude is attenuated due to the AE multiplied signal propagation.

In the case of a one-dimensional structure, according to experimental results, the propagated A
The following relationship holds between the E-fold signal amplitude value E and the amplitude value Eo at the generation position.

Here, L is the signal propagation distance and C is the proportionality constant.

Therefore, the amplitude value Eo at the generation position can be determined from the measured AE signal amplitude value E and the propagation distance.

Attenuation correction calculators 7a and 7b are peak hold circuits 4a
, 4b and the uncertain information regarding the defect position obtained by the signal position calculation device 6, the arithmetic processing is performed according to the above attenuation formula, and the AE signal at the occurrence position is calculated. This is to find the amplitude value.

Assuming that the signals detected and peak-held by both AE signal converters 2 a t 2 b are AE multiplied signals generated from the same defect position, the amplitude values obtained by both attenuation correction calculators 7 a and 7 b should be approximately equal, and if the peak-held signal is due to an AE multiplied signal generated from a different defect position or due to the mixing of environmental noise, both attenuation correctors 7a.

The amplitude values obtained in step 7b should be completely different.

The comparator circuit 8 compares the AE signal amplitude values at the generation positions subjected to attenuation correction by both attenuation correction calculators 7a and s7b, and only when the comparison results are approximately equal, the AE signal converters 2a and 2
It determines that the signal detected by b is valid and outputs the position calculation result.

Conversely, if the comparison results are completely different, the position calculation results are rejected.

Note that this example is applied to a case where the object to be measured is a one-dimensional structure, but by installing three to four AE signal converters, defect locations can be similarly detected for two-dimensional structures, etc. It is a hot topic to locate the scales.

With the above configuration, this invention can determine whether or not the signal detected by the transducer, which is the basis for defect position location calculation, is valid. It is possible to prevent this and locate the true defect position of the object with high precision.

[Brief explanation of drawings]

The drawing is a block diagram of an embodiment of the invention. 2a, 2b...A, E signal converter, 7a,
7b... Attenuation correction calculator, 8... Comparison circuit.

Claims (1)

[Claims] 1. In a device that locates the AE multiplied signal generation position from the arrival time difference and arrival order of the AE multiplied signal reaching a set of AE signal converters, the signal generation position calculation result and the AE multiplied signal amplitude from each of the AE signal converters are used. A signal discrimination device characterized in that the amplitude correction results are introduced into an attenuation correction calculator, each amplitude correction result is introduced into a comparison circuit for comparison, and a position calculation result is output only when the amplitude correction values are substantially equal. .