JPS61138160A - Ultrasonic flaw detector - Google Patents

Abstract

PURPOSE:To improve S/N and the power to resolve defects without depending on the kind and size of a material to be inspected and the kind, etc. of the defects thereof by providing a filter group consisting of the filters which are the same in the characteristics and shape and are different in the central frequency to an ultrasonic signal receiving system and making arithmetic processing in such a manner that only the desired signal component is obtd. out of the received signals. CONSTITUTION:The reception signal from a receiver 3 is amplified by the filter group 4 having the filters which are equal in the characteristics and are different in the central frequency. The beam path and amplitude value are measured by a beam path measuring circuit 5 and an amplitude value measuring circuit 6 and are thereafter stored into a memory 8A. The position of an ultrasonic probe 1 is also detected 7 and is stored in the memory 8A. These sets of the data are subjected to the arithmetic processing to detect the max. value of the absolute amplitude value in an arithmetic part 8D and are stored in the memory 8A. The defect data and shape data are obtd. as the position coordinates with the data in the position of the same probe 1 as one set by using the distance-amplitude characteristic curve stored in a memory 8B and the shape value stored in a memory 8C and are displayed 10 after digital-to-analog conversion 9.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an ultrasonic detector 1 for measuring the presence or absence of defects and the dimensions of defects existing on the surface or inside of a metal material or the like as an object to be inspected.
The present invention relates to an ultrasonic flaw detection device, and particularly to an ultrasonic flaw detection device that improves the S/N ratio of a received signal and improves defect resolution.

[Technical background of the invention and its problems] In ultrasonic flaw detection, one way to reliably detect defects is to improve the ratio of defect signal to noise, that is, the S/N ratio. In particular, it is necessary to detect small defects that are in close contact with each other (due to large crystal grains) in materials with large material noise (due to large crystal grains), such as stress corrosion cracking that occurs in austenitic stainless steel. The detection limit is often determined by the above S/N comparison.

In the conventional ultrasonic flaw detection apparatus, efforts are being made to improve the flaw detection method, data processing method, etc. in order to meet the above-mentioned request for an improvement in the S/N ratio. However, no uniform measures have yet been taken to improve the S/N ratio regardless of the type of material of the test object, its size, type of defect, etc.

[Object of the Invention] The present invention has been made based on the above-mentioned circumstances, and its purpose is to improve the S/S/ An object of the present invention is to provide an ultrasonic flaw detection device that can improve the N ratio and defect resolution.

[Summary of the Invention] In order to achieve the above object, an ultrasonic flaw detection device according to the present invention uses a filter group consisting of a plurality of filters having the same shape of filter characteristics but different center frequencies in an ultrasonic receiving system. The L signal group is passed through the above filter group so that only the desired signal component is obtained from the received signal, taking advantage of the fact that the defective echo signal has frequency components in a wider band than the noise signal. This method is characterized by improved S/N ratio of the received signal and improved defect resolution.

[Embodiment of the Invention] An ultrasonic flaw detection apparatus according to the present invention will be described below according to an embodiment shown in FIG.

In FIG. 1, reference numeral 1 denotes an ultrasonic probe, such as an angle probe, equipped with an ultrasonic transducer 1A inside, and the object P
placed above. 2 is a pulser that applies a high voltage pulse for excitation to the ultrasonic probe 1. This pulser 2 excites the ultrasound probe 1 and transmits an ultrasound beam tJB to the subject P. 3 is a receiver, which transmits the ultrasonic beam tJ
B receives an ultrasonic echo UE formed by being reflected by a defect CL in the subject P via the ultrasonic probe 1.

Reference numeral 4 denotes a filter group (multi-channel analog filter) consisting of a large number of filters having the same filter characteristic shape but different center frequencies. This filter group 4 takes in the received signal from the receiver 3, and outputs a signal from which components other than predetermined frequency components have been removed.

5 is a beam path measuring circuit, 6 is an amplitude value measuring circuit,
These A/D convert the output signal from filter group 4,
The beam path and amplitude values are measured based on the digital signal. Reference numeral 7 denotes a probe position detector that detects the position of the ultrasound probe 1 on the subject P. Reference numeral 8 denotes a calculation microcomputer, which is used for input data to store the outputs from the beam path measurement circuit 5 and the amplitude value measurement circuit 6 as one data group, and also to store the output from the probe position detector 7 at that time. A memory 8A, a DAC curve memory 8B in which data indicating a DAC (distance amplitude characteristic) curve is pre-stored, a subject shape memory 8C1 in which data indicating the shape of the subject P is pre-stored;
It is composed of an arithmetic unit 8D that executes data processing to be described later based on data 8B and 8C.

9 is a D/A that converts the output from the calculation unit 8D into an analog signal.
It is a converter. Reference numeral 10 denotes a display device that displays images based on the output of the D/A converter 9 using display methods such as A scope, B scope, and C scope. Reference numeral 11 is a control microcomputer that controls each of the circuits described above.

In the above, the amplitude value data group at the same beam path stored in the input data memory 8A is calculated based on the beam path based on the DAC curve stored in the DCA curve memory 8B in the arithmetic unit 8D for each data in the same filter. After canceling out the effect of the difference, the maximum value is detected (by multiplying each amplitude value data by the reciprocal of the DAC curve value at the beam path at that time), and each amplitude value data is calculated by this maximum value. Standardized. Then, the minimum value of this standardized amplitude value data is detected for each beam path, and if this value exceeds a predetermined reference value, it is detected as a defect and converted into an analog signal by the D/A converter 9. and displayed on the display device 10.

Further, the data of the object shape stored in the object shape memory 8C of the calculation microcomputer 8 is stored in the calculation section 8D.
Shape arithmetic processing is performed, and the processing results, like the defect data described above, are converted into analog signals by the D/A converter 9 and displayed on the display device 10 together with the defect data described above.

The operation of this embodiment with the above configuration will be explained with reference to FIGS. 2 to 7.

As a feature of the operation of this embodiment, as shown in FIG. 2, attention is paid to the difference in frequency characteristics between the defective echo signal UE and the noise signal NS.
By taking advantage of the fact that frequency components exist in a wide band compared to The aim is to improve this and make it possible to detect minute defects. The operation will be explained in detail below.

The receiver 6 converts the received signal into a third
As shown in the figure, the filter is amplified by a filter group 4 which has a plurality of filters with the same filter characteristics but slightly different center frequencies, and the beam path measurement circuit 5 and the beam path measurement circuit 6 measure the beam path and amplitude values for each channel. After the data of the same beam path is measured, the data of the same beam path is stored as one data group in the input data memory 8A of the calculation microcomputer 8.

At the same time, the position of the ultrasound probe 1 is detected by the probe position detector 7 and stored in the input data memory 8A of the calculation microcomputer 8.

In the input data memory 8A of the arithmetic microcomputer 8, the above-mentioned data are stored in the format shown in the table below for each data of the same filter.

Next, the data stored in the input data memory 8A is processed by the calculation unit 8D to determine the amplitude absolute value of the amplitude values obtained in channels 1 to n at one probe position and one beam path length. Arithmetic processing for detecting the maximum value is performed, and data resulting from the processing is stored in the input data memory 8A.

Next, the data stored in the input data memory 8A is stored in the DAC curve memory 8B of the calculation microcomputer 8, with data at the same probe position set as one set.
The processing shown in FIG. 5 is executed in the arithmetic unit 8D using the AC curve 25 as shown in FIG. 4 and the shape values stored in the object shape memory 8C.

That is, in FIG. 5, probe position data is input from the probe position detector 7 in step S1.

In step S2, each beam path and the amplitude value data A at that time are input from the beam path measurement circuit 5 and the amplitude value measurement circuit 6, and the DAC songs IIF and fi are input from the DAC curve memory 8B and the object shape memory 8C, respectively. Width value reference value E
Enter.

In step S3, the DAC curve value at each beam path is calculated, and in step S4, the amplitude value data is multiplied by the reciprocal of the DAC curve value. In step S5, the maximum value of the amplitude value is detected. In step S6, each amplitude value data is normalized by the maximum value. In step S7, the minimum value AMIN(M) of one amplitude value is determined for each beam path. To detect.

In step S8, the minimum value AIvllN in step S7
It is determined whether or not (M) exceeds the amplitude value reference E. If it does, the defect position coordinates are calculated in step S9, and the result is output to the display device 1o. If the distance is not exceeded, the probe position is moved, and then the process returns to step S1 to execute the same process as described above.

On the other hand, as another system process of step S1, step Sfl
Then, shape data of the object to be inspected is input, defect position coordinates are calculated in step S1t, and the calculation result is output to the display device 10 in the same manner as above.

Through the above calculation, defect data and shape data are obtained as position coordinates, which are converted into analog signals by the D/A converter 1, and the flaw detection results are displayed on the display device 10. In addition, the object shape memory 8 of the calculation microcomputer 8
Since the data stored in C is also processed by the calculation unit 8D and displayed on the display device 10 at the same time, the flaw detection result is displayed as a cross-sectional image (B scope image) as shown in FIG.

As described above, according to the embodiment, the difference in frequency characteristics between the defective echo signal and the noise signal, that is, the fact that the frequency component of the defective echo signal exists in a wider band than that of the noise signal, is utilized. Since the filter is selected, the S/N ratio can be improved, and therefore, it is possible to detect minute defects.

In addition, the flaw detection results are displayed as cross-sectional images, which not only makes it easier to understand the defect location, but also uses a frequency analysis method to process the signal by normalizing the signal after passing through the filter. Therefore, the deviation in the peak position of the amplitude value is small, and therefore the defect position can be displayed with high accuracy.

Next, another embodiment of the present invention will be described with reference to FIG. Although the S/'N ratio can be greatly improved in the embodiments described above, some problems remain in the discrimination between defective echoes and pseudo echoes based on shape and the like. That is, there is a possibility that a false echo due to the shape or the like may be determined to be a defective echo.

As a countermeasure against this problem, as shown in FIG. 7, a table representing the difference in frequency characteristics between defective echoes and pseudo echoes due to shape, etc. is stored in the memory of the calculation microcomputer 8 in advance, and the amplitude values at each beam path mentioned above are stored in advance. Minimum iiiA of
For those exceeding the standard value E of MIN, the seventh
Reliability can be further improved by adding a judgment as to which region is included in the defective echo region or the pseudo echo region shown in the figure, and improving the display device 10 so that only those included in the defective echo region tiil are displayed as defects. You can improve.

The present invention is not limited to the above embodiments, and can be implemented with various modifications without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the present invention, a filter group consisting of a plurality of filters having the same filter characteristic shape but different center frequencies is provided in the ultrasonic receiving system, and defective echo signals are Taking advantage of the fact that frequency components exist in a wider band than noise signals, the signal that has passed through the above filter group is subjected to paralysis processing so that only the desired signal component is obtained from the received signal. It is possible to provide an ultrasonic flaw detection device that can improve the SZN ratio of the received signal and the defect resolution regardless of the type of material of the specimen, its size, type of defect, etc.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of an embodiment of an ultrasonic flaw detection device according to the present invention, and Figs. 2 to 6 explain the operation of the embodiment. Figure 3 is a diagram showing the characteristics of individual filters in the filter group, Figure 4 is a diagram showing the DAC curve, and Figure 5 is a diagram showing the processing procedure performed in the calculation section. 6 is a diagram showing an example of the flaw detection results displayed on the display device, and FIG. 7 is for explaining another example of implementation according to the present invention, which is for discriminating defect echo signals and noise signals. FIG. 2 is a diagram showing a table installed in the memory of the calculation microcomputer. 1... Ultrasonic probe, 1A... Ultrasonic transducer, 2.
... Balsa 1.3... Receiver, 4... Filter group, 5... Beam path measuring circuit, 6... Amplitude value measuring circuit, 7... Probe position detector, 8...・Microcomputer for calculation, 8A...Memory for input data, 8B
... DAC curve memory, 8C... object shape memory, 8D... calculation unit, 8th... filter memory,
9...D/A converter, 10...Display device, 11...
- Control microcomputer. Applicant's agent Patent attorney Suzue Takehiko-ku";b-xrt\4th race

Claims (1)

[Claims] In an ultrasonic flaw detection device that sends and receives ultrasonic waves to and from a test object to ultrasonically detect defects existing inside the test object, multiple filters are used that have the same filter characteristic shape but exceptionally different center frequencies. A filter group consisting of the above is installed in the ultrasonic receiving system to take advantage of the fact that defective echo signals have frequency components in a wider band than noise signals, so that only desired signal components can be obtained from the received signal. An ultrasonic flaw detection apparatus characterized in that the signal group that has passed through the filter group is subjected to arithmetic processing to improve the S/N ratio of the received signal and the defect resolution.