JP2012083297A - Ultrasonic flaw detection method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detection method in which the electrical noises generated in an ultrasonic flaw detection of a structure can be reduced.SOLUTION: The ultrasonic flaw detection method includes: an inspection step (S1) of irradiating the structure with ultrasonic waves using an array probe composed of a plurality of transducers and receiving output signals of ultrasonic echo caused by reflectors, such as defects of the structure; and a noise reduction step (S3) of inputting respective output signals received in the inspection step into an arithmetic processing unit and reducing the electrical noises included in the respective output signals by the correlation processing.

Description

  The present invention relates to an ultrasonic flaw detection method and an ultrasonic flaw detection apparatus, and more particularly to an ultrasonic flaw detection method and an ultrasonic flaw detection apparatus for a structure.

  Phased array flaw detection, which is one of ultrasonic flaw detection, arranges a plurality of transducers and receivers on a one-to-one basis, and shifts the timing of the input signal voltage applied to the transducers to change the direction of the ultrasonic beam. You can change or squeeze the ultrasonic beam. In such a phased array flaw detection method, high-accuracy flaw detection and high-accuracy flaw detection are possible, and because flaw detection results can be imaged, they are used for inspection of internal defects in structures, such as boilers and nuclear power plants. Used in many products.

On the other hand, a high-attenuating material that attenuates when an ultrasonic wave is incident, for example, a powder molded body or a porous molded body, has a low ultrasonic transmission property, so that it is necessary to perform ultrasonic flaw detection with high sensitivity. In this case, since it becomes easy to be affected by electrical noise by increasing the sensitivity, there is a problem that it is difficult to detect ultrasonic echoes from defects in the high attenuation material.
As a signal processing technique for reducing such electrical noise, a method using a wavelet and a method using a frequency filter are known.

Japanese Patent No. 4371364

However, since the above-described Patent Document 1 does not disclose each parameter necessary for wavelet calculation, there is a problem that a calculation error by a measurer increases and electric noise cannot always be reduced satisfactorily.
In addition, when using frequency filters, since there are so many types of frequency filters, it is necessary to investigate a filter suitable for reducing the electrical noise contained in the received output signal. It is not preferable.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ultrasonic flaw detection method and an ultrasonic flaw detection capable of reducing electrical noise generated in ultrasonic flaw detection of a structure. To provide an apparatus.

  In order to achieve the above object, an ultrasonic flaw detection method according to claim 1 is an ultrasonic flaw detection method using a phased array method in which a structure is irradiated with ultrasonic waves to inspect the structure. An inspection process for irradiating the structure with an ultrasonic wave using an array probe configured to receive an output signal of an ultrasonic echo due to a defect existing in the structure, and each received in the inspection process And a noise reduction step of inputting an output signal to an arithmetic processing device and reducing electrical noise included in each output signal by correlation processing.

The ultrasonic flaw detection method according to claim 2 is characterized in that, in claim 1, the noise reduction step performs a synthesis process for synthesizing output signals from the plurality of transducers before performing the correlation process. .
According to an ultrasonic flaw detection method of a third aspect, in the first or second aspect, the correlation processing uses an actual signal having a predetermined S / N ratio as a correlation processing function.

  An ultrasonic flaw detector according to claim 4 is an ultrasonic flaw detector using a phased array method in which a structure is irradiated with ultrasonic waves to inspect the structure, and an array probe including a plurality of transducers is provided. Using the inspection means for irradiating the structure with ultrasonic waves and receiving the output signal of the ultrasonic echo by the defect part inherent in the structure, and inputting each output signal received in the inspection process to the arithmetic processing unit And noise reduction means for reducing electrical noise included in each output signal by correlation processing.

  The ultrasonic flaw detector according to claim 5 is characterized in that, in claim 4, the noise reduction means performs a combining process for combining the output signals from the plurality of transducers before performing the correlation process. .

  According to the ultrasonic flaw detection method of claim 1, an ultrasonic wave is emitted to a structure using an array probe composed of a plurality of transducers, and an ultrasonic echo is output by a defect portion present in the structure. An inspection process for receiving a signal, and a noise reduction process for reducing electrical noise included in each output signal received in the inspection process by correlation processing using an arithmetic processing unit.

According to the ultrasonic flaw detection apparatus of claim 4, the structure is irradiated with ultrasonic waves using an array probe composed of a plurality of transducers, and an ultrasonic echo is generated by a defect portion present in the structure. Inspection means for receiving the output signal, and noise reduction means for reducing electrical noise contained in each output signal received by the inspection means by correlation processing using an arithmetic processing unit.
Therefore, by reducing the electrical noise included in each output signal by the correlation processing, it is possible to detect the defect signal that becomes the reflector with high accuracy, so that the inspection accuracy can be improved.

1 is a schematic configuration diagram of an ultrasonic flaw detector according to the present invention. It is a figure which shows an example of the phased array method which flaws by shifting the timing of the input signal voltage applied to each vibrator arrange | positioned in a probe by the focal depth of an ultrasonic beam. It is a flowchart which shows the ultrasonic flaw detection method of the structure based on this invention. It is a schematic block diagram for performing the signal processing investigation by the ultrasonic flaw detection method. (A) is a graph showing a signal processing result obtained by performing correlation processing after synthesizing each output signal received by the pulse receiver, and (B) is a signal processing obtained by performing synthesis processing after performing correlation processing on each output signal. The graph which showed the result, (C) is the graph which showed the signal processing result which combined each output signal, (D) is the graph which showed the signal processing result which combined each output signal after letting each output signal pass through a frequency filter It is.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram including an ultrasonic flaw detector according to the present invention.
The ultrasonic flaw detector 1 uses a phased array method, and is a device for acquiring defect information inside a structure, for example.

  The ultrasonic flaw detector 1 is connected to a pulse generator 4 that generates an input signal voltage and the pulse generator 4, and generates an ultrasonic wave by applying an input signal voltage to each transducer to be described later to the structure 2. An array probe 6 that irradiates and receives an ultrasonic echo from the defect 2a and converts it into an electrical signal, and a pulse that is connected to the array probe 6 and receives the electrical signal converted by the array probe 6 A receiver 8, an electric signal received by the pulse receiver 8, that is, an A / D converter 10 that performs analog / digital conversion on an output signal, an arithmetic processing device 12 connected to the A / D converter 10, and an arithmetic processing device 12 And a monitor 18 for outputting a processing result in the arithmetic processing unit 12 and the like.

As shown in FIG. 2, the array probe 6 disposed in the structure 2 is provided with a plurality of transducers 6 a disposed therein, and each of the transducers 6 a is applied by an input signal voltage applied from the pulse generator 4. The vibrator 6a vibrates to generate ultrasonic waves. Here, array probe 6, by shifting the timing of applying the input signal voltage to the vibrator 6a, it is possible to change the direction and depth of focus P _f of the ultrasonic beam.
The arithmetic processing unit 12 includes a central processing unit (hereinafter abbreviated as CPU) 14 and a memory 16. The memory 16 includes a RAM, a ROM, and the like, and stores each program.

Hereinafter, an ultrasonic flaw detection method according to the present invention of the ultrasonic flaw detection apparatus 1 configured as described above will be described.
FIG. 3 is a flowchart showing an ultrasonic flaw detection method for the structure 2, and will be described below based on the flowchart. Each process of steps S2 and S3 described below is performed by executing a program stored in the memory 16.

  In step S 1, the structure probe 2 is irradiated with ultrasonic waves from the array probe 6, and an ultrasonic echo from the defect 2 a in the structure 2 is received as an output signal via the array probe 6 and the pulse receiver 8. To do. Thus, the output signal is analog / digital converted by the A / D converter 10 and input to the arithmetic processing unit 12 (inspection process, inspection means). Here, the input signal input from the pulse generator 4 to the array probe 6 is a pulse wave.

In step S2, each output signal input to the arithmetic processing unit 12 is combined to be combined into one output signal.
Specifically, by irradiating ultrasonic waves from a plurality of transducers 6a, the number of output signals reflected and output from the defect portion 2a is also received by the number of transducers 6a. Are combined into one signal.

In step S3, correlation processing is performed on the synthesized signal (noise reduction step, noise reduction means).
Specifically, correlation processing is performed on the synthesized signal using a correlation processing function to reduce electrical noise contained in the synthesized signal. At this time, the reference wave stored in the memory 16 is used as the correlation processing function. The reference wave is an actual signal when a defect 2a is provided at a predetermined depth (for example, 50 mm) of the structure 2, and is an actual signal having a predetermined SN ratio (for example, 10.7). . In addition, since it is necessary to suppress an electrical noise in order to improve the S / N ratio of a reference wave, the depth of the defect part 2a should be comparatively shallow.

  As shown in the schematic configuration diagram in FIG. 4, the output signal received by the pulse receiver 8 by arranging the array probe 6 on the high-attenuator as the structure 2 in which the defective portion 2 a is formed by the method described above. A signal processing survey was conducted. Here, the defect portion 2a is a 20 mm square hole, and the depth D from the surface of the structure 2 on which the array probe 6 is disposed to the defect portion 2a is 110 mm. The reference wave used for the correlation process is a real signal when the defect 2a is provided at a depth of 50 mm of the structure 2, and the SN ratio is 10.7.

  Further, the high attenuation body usable as the structure 2 is, for example, a powder molded body such as a compacted ceramic green body, a porous molded body such as concrete or a ceramic composite material, a cast or welded portion of stainless steel, Examples thereof include fiber reinforced plastics and carbon fiber reinforced carbon composite materials.

  The survey results are shown in FIGS. Here, FIG. 5A is a graph showing the signal processing result when the correlation processing is performed after combining the output signals received by the pulse receiver 8 as described above. As a comparative example, FIG. 5B is a graph showing signal processing results when the received output signals are subjected to correlation processing after performing correlation processing, and FIG. 5C is a case where the received output signals are combined. FIG. 5D is a graph showing the signal processing result when the synthesis processing is performed after each received output signal is passed through the frequency filter. The frequency filter used in FIG. 5D is an infinite impulse response filter (hereinafter abbreviated as IIR filter).

  According to FIGS. 5 (A) and 5 (B), by performing correlation processing on each received output signal, the electrical noise Sn is smaller than when correlation processing is not performed as shown in FIG. 5 (C). It can be seen that the defect signal Sd is accurately detected and the defect signal Sd is accurately detected. 5D using the IIR filter, the electrical noise Sn is reduced as compared with FIG. 5C, but FIGS. 5A and 5B are still better than FIG. 5D. It can also be seen that the reduction range of the electrical noise Sn is large.

  Then, according to FIG. 5A, it can be seen that the electrical noise Sn is satisfactorily reduced even when compared with FIG. 5B, and there is no significant difference in the SN ratio. In other words, even when the correlation process is performed after the output signals are combined, the electrical noise Sn is reduced well and the defect signal Sd is accurately detected, as in the case where the combination process is performed after the correlation processing of the output signals. It can be detected.

  As described above, according to the present embodiment, the array probe 6 composed of a plurality of transducers 6a is arranged on the structure 2, and ultrasonic waves are emitted from the transducers 6a so A sound wave echo is received as an output signal, the received output signal is input to the arithmetic processing unit 12, and correlation processing is performed using a reference wave.

As a result, the electrical noise Sn can be satisfactorily reduced and the defect signal Sd can be detected with high accuracy, so that the inspection accuracy can be improved.
In particular, since the correlation process is performed after combining each received output signal into one signal, the time required for the correlation process is 1 / number of transducers, and the signal processing time can be shortened while maintaining the inspection accuracy. , Work efficiency can be improved. Therefore, even when the vibrator 6a is increased in order to improve the inspection accuracy, the signal processing time can be shortened.

Furthermore, by using a real signal with a high S / N ratio as a reference wave for the correlation processing function, the electrical noise Sn can be reduced well, and the inspection accuracy can be improved.
Although the description of the embodiment is finished as described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Ultrasonic flaw detector 2 Structure 2a Defect part 4 Pulse generator 6 Array probe 8 Pulse receiver 10 A / D converter 12 Arithmetic processor

Claims (5)

In the ultrasonic flaw detection method using the phased array method of inspecting the structure by irradiating the structure with ultrasonic waves,
An inspection step of irradiating the structure with an ultrasonic wave using an array probe composed of a plurality of transducers and receiving an output signal of an ultrasonic echo due to a defect existing in the structure;
A noise reduction step of inputting each output signal received in the inspection step to an arithmetic processing device, and reducing electrical noise included in each output signal by correlation processing;
An ultrasonic flaw detection method comprising:   The ultrasonic flaw detection method according to claim 1, wherein the noise reduction step performs a synthesis process of synthesizing output signals from the plurality of transducers before performing the correlation process.   3. The ultrasonic flaw detection method according to claim 1, wherein in the correlation processing, an actual signal having a predetermined S / N ratio is used as a correlation processing function. In an ultrasonic flaw detector using a phased array method in which a structure is irradiated with ultrasonic waves to inspect the structure,
An inspection unit that irradiates the structure with ultrasonic waves using an array probe composed of a plurality of transducers, and receives an output signal of an ultrasonic echo due to a defect existing in the structure;
Noise reduction means for inputting each output signal received in the inspection process to an arithmetic processing device and reducing electrical noise included in each output signal by correlation processing;
An ultrasonic flaw detector characterized by comprising:   The ultrasonic flaw detector according to claim 4, wherein the noise reduction unit performs a synthesis process of synthesizing output signals from the plurality of transducers before performing the correlation process.

Images