JPS5942827B2 - AE diagnostic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diagnostic device using an acoustic emission method (hereinafter abbreviated as AE method) used when testing the health of structural materials and pressure vessels.

In general, the sound waves that are generated when a substance, especially a solid material, deforms or breaks under stress are called acoustic emission (hereinafter abbreviated as AE). being called. In recent years, an abnormality diagnosis system using AE as described above has been developed.

In particular, AE diagnostic equipment has been developed and is widely used for flaw detection in hydraulic tests of large structures such as pressure vessels and oil tanks. According to the AE diagnostic method, by simply attaching a small number of AE sensors to the surface of the test object and evaluating the detection outputs of these sensors, it is possible to inspect the entire wide area of the test object in a short time. Not only that, but you can also know the location of defects.

These are features that the conventional inspection method, ultrasonic flaw detection, does not have. However, the signals detected by the AE sensor are caused by plastic deformation due to stress concentration generated in the defective part of the test object due to the pressurizing force during the hydraulic test, and by the development of defects latent inside the material. There is a need to distinguish between the two. Generally, an AE diagnostic device has a plurality of AE sensors, an amplifier that amplifies their detection output, a signal processing device that receives the amplifier output and performs various signal processing, and a display device that displays the processed output. are doing.

The AE sensor is attached to the surface of the test object and detects the AE waves generated by deformation and defect growth, and the amplifier amplifies these detection outputs to the level required for signal processing. be. The signal processing device determines the number of AE waves generated, their frequency of occurrence, etc., and determines the position of the AE generation source from the difference in reception time of each AE sensor. When the relationship between the test pressure of a water pressure test and the number or frequency of occurrence of AE waves is determined using the above-mentioned apparatus, a curve as shown in FIG. 1 is obtained.

When it is confirmed that the frequency of AE waves increases as the test pressure increases, it is determined that there is a defect that causes stress concentration in a part of the test object. In addition, the position of the AE wave source is determined by any pair of AE sensors AB.
It is determined by the time difference ΔT between the arrival times of the signals. In other words, the AE wave generation source that gives the time difference △T is expressed by the following equation, where △T is constant, where the distance between sensors AB is 2a, and the distance that the AE wave travels during the time difference △T is -constant. Exists on a hyperbolic line. x2y21 -......1 to 24a2- to 24 Therefore, at least three AE sensors are used, the hyperbola obtained by the time difference of each pair of AE sensors is obtained, and their By finding the intersection, the location of the AE wave source can be found.

In the above-mentioned equipment, it is possible to know the generation of AE waves and the location of the source, but it is possible to determine whether the generation is due to a phenomenon of plastic deformation of an internal defect or whether the defect is expanding and progressing. It is not possible to determine whether it is based on
The present invention was made in view of the above circumstances, and an object of the present invention is to obtain an AE diagnostic device that can determine the extent of defects.

In the present invention, the above object is achieved using the Kaiser effect.

In other words, the Kaiser effect is defined as ``When a material has a stress history, almost all A
It is said that this Kaiser effect is clearly observed for AE caused by plastic deformation, but not for AE caused by fracture. Therefore, in the case of AE based on plastic deformation, the test water pressure time curve,
As shown by curve a in Figure 3, which shows the AE frequency time curve, there is clearly a Kaiser effect between the test water pressure and the number of AE occurrences, but the same effect can be seen in the case of AEs caused by the progress of a defect. As shown by curve b in the figure, no Kaiser effect is observed.
Note that in this figure, K indicates the Kaiser effect region. As shown in the water pressure/time curve in Fig. 3, if a water pressure cycle 199 is added in which the maximum value becomes larger as the water pressure rectifies over time, the water pressure that gives the AE occurrence frequency Ns is P in the case of curve b. ~, but in the case of curve a, Pl, P2, P3 (P1 × P2 < P3
). Therefore, conversely, it is possible to determine what the AE generation source is from the pressure value.

The AE diagnostic device of the present invention is constructed based on the above principle.

The details of the present invention will be explained below with reference to FIG.

FIG. 4 shows a state in which the pressure vessel V is being diagnosed by the apparatus of the present invention. Pressure device 1 is installed in pressure vessel V.
Pressure is applied such that the pressure increases over multiple cycles. There are four AE sensors 2a on the surface of the pressure vessel V.
2d are attached, and their detection outputs are amplified by corresponding amplifiers 3a to 3d, respectively, and sent to the AE signal discrimination circuit 4.

The AE signal discrimination circuit 4 extracts the AE signal from the input signal by separating it from the noise, and counts and generates the AE signal detected by the position locating circuit 5 and each sensor, which locates the position of the AE source using the above equation 1. Counters 6a to 6 for calculating frequency
send it to d. Note that the output of the position locating circuit 5 is displayed on the occurrence position display device 7. The outputs of the counters 6a to 6d are a comparator 8a that uses the AE occurrence frequency N as a reference value for variable setting.
~8d and the display 9. Comparator 8a~
8d is assumed to generate an output when the reference value Ns and the actually calculated incidence rate n are equal (.=Ns),
Each comparator output is given to display control circuits 10a-10b. The display control circuits 10a to 10d input the pressure signal of the control device 11 that controls the pressurizing device 1 to the display 9 when the output of the corresponding comparator is received.

The output of the display control circuit is also output to the displays 12a-12d. A
It is given to the E type determination circuit 13.

The AB type determination circuit 13 receives from the display control circuits 10a to 10d the pressure signal value when the AE incidence rate n becomes Ns when the pressure cycle is repeated, and determines the pressure cycle, .
When n = N8, an alarm is generated when the pressure signal becomes P1 × P2 × P3 as Pl, P2, P3.
Alarm indicator 14 indicates whether an alarm has been issued regarding the E sensor.
Displayed in a to 14d. Note that no alarm is generated when P1=P2=P3. As is clear from the above, according to the apparatus of the present invention, it is possible to locate the source of the AE waves generated inside the object under test during a hydraulic test, and to determine whether the cause of AE generation is based on the progress of a defect or the plastic deformation of the material. It is possible to automatically determine whether the

Therefore, the reliability of abnormality diagnosis of the test object is improved, and the degree of risk thereof can be accurately known.

Note that the present invention measures the time difference between the pressure signal obtained at a predetermined AE wave generation frequency N8 and the pressure signal corresponding to the increased pressure while keeping the pressure increase rate of the pressure cycle the same,
It may be configured to issue an alarm when this time difference increases.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the number of AE occurrences or the frequency of occurrence in the test object during a water pressure test and the test water pressure. FIG. 3 is a diagram showing a pressure time curve and an AE occurrence frequency time curve when a pressure cycle is applied to a test object, and FIG. 4 is a process diagram of an embodiment of the present invention. 1... Pressure device, 2a-2d...AE
Sensor, 4...AE signal discrimination circuit, 5...
...Positioning circuit, 6a to 6d...Counter,
8a-8d... Comparator, 9, 12a-12d.
...Display device, 10a to 10d. ．． ．． ．． ．． ．． Display control circuit, 11... Control circuit, 13...
AE type determination circuit.

Claims (1)

[Claims] 1. A pressurizing device that increases and pressurizes the test object in multiple cycles, a detection system that detects the AE waves generated in the test object, and a predetermined AE occurrence frequency n_ by counting the output of each detection system.
a counting means for calculating s, and an AE product for determining the AE type by comparing the pressure signal from the pressurizing device corresponding to the AE occurrence frequency n_s obtained by the counting means with the pressure signal for each pressure cycle. An AE diagnostic device comprising a separate determination means.