JPH09292374A - Ultrasonic flaw detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detector which improves the S/N ratio by lowering noises as well as enhancing spatial resolution. SOLUTION: This ultrasonic flaw detector is provided with an array probe 1 in which ultrasonic vibrators are arranged in an array and a drive controlling means 3 which controls the delay time of drive pulses to be applied to the ultrasonic vibrators, so that ultrasonic waves generated by the ultrasonic vibrators are focused at one point in a specimen A, to perform an operation of detecting ultrasonic waves reflected from the inside of the specimen multiple times, varying the focusing positions of the ultrasonic waves and a signal processing means 3 in which signals of the reflected ultrasonic waves obtained from the focusing positions in the specimen undergo an arithmetic mean processing to perform a process of fetching signals from a defective part in the specimen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detector for inspecting a defective portion such as an internal flaw in a subject with much noise such as a forest echo.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic flaw detector has been used as a device for nondestructively inspecting the presence or absence of defects such as flaws inside a steel material. The ultrasonic flaw detection device inspects the presence or absence of a defect inside the steel material by applying the ultrasonic wave generated by the probe to the steel material and detecting the reflected ultrasonic wave reflected by the defect portion and returning. In this case, the reflected ultrasonic waves detected include electrical noise and the like in addition to the echo from the defective portion. In order to remove such noise, the reflected ultrasonic waves are detected a plurality of times at the same probe position, and the averaging process is performed. Since the reflected ultrasonic waves from the defective portion are detected at a fixed position, the signal is detected without change even if the averaging process is performed. However, since electrical noise is random, it is reduced and detected by performing the averaging process, and the SN ratio is improved.

By the way, when the object is a steel material having relatively large crystal grains such as stainless steel, there is an echo called a so-called Yubayashi echo that reaches the surface of the steel material by being reflected at the interface of the crystal grains. . Since the position of the electronic noise is not constant, the electronic noise is reduced by performing the averaging process by performing the probe a plurality of times at the same probe position. However, since the forest echo is noise that depends on the position, it is detected in the same way when the probe position is the same, and even if the averaging process is performed, it is not reduced.

In order to reduce the above-mentioned forest-like echo, a signal processing device for an ultrasonic flaw detector as disclosed in Japanese Patent Laid-Open No. 6-207928 has been proposed. FIG. 4 is a diagram for explaining the principle.
In FIG. 1A, 50 is a probe and A is a subject. In this ultrasonic flaw detector, by moving the probe 50 or the subject A, the probe position is changed to detect reflected ultrasonic waves a plurality of times (three times in the case of FIG. 4), and the detected signal is detected. The defective portion 51 inside the subject A is detected by performing the averaging process. The waveform on the left side of FIG.
The signals of the reflected ultrasonic waves detected by the probe 50 at each position of the probe are shown, and the waveform on the right side of FIG. The signal is shown. Since the ultrasonic beam has a spread, the ultrasonic waves reflected from the defect can be detected even if the probe position is slightly displaced. On the other hand, since the forest echo is based on crystal grains, the appearance of the forest echo changes even if the position of the probe 50 is slightly deviated. Therefore, the position of the probe 50 is shifted to perform flaw detection a plurality of times,
By performing an averaging process on the plurality of detected reflected ultrasonic waves, it is possible to reduce the forest echo and detect the reflected ultrasonic waves from the defect portion.

[0005]

However, in the above-described conventional ultrasonic flaw detector, in order to reduce the forest echo, the probe position is gradually shifted and the reflected ultrasonic waves are detected a plurality of times. Since the signals of the detected reflected ultrasonic waves are added and averaged, there is a problem that the spatial resolution is lowered. That is, since the position of the probe is shifted to detect flaws,
It can be seen that the defect is within the displaced range, but it is unknown where it is located, and thus the spatial resolution is reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic flaw detector capable of enhancing the spatial resolution and reducing noise to improve the SN ratio. It is a thing.

[0007]

An ultrasonic flaw detector according to the present invention for achieving the above object generates ultrasonic waves inside a subject and detects reflected ultrasonic waves from the inside of the subject. In an ultrasonic flaw detector for detecting defects in a subject, an array transducer in which ultrasonic transducers are arranged in an array, and controlling the delay time of a drive pulse given to each ultrasonic transducer, Drive control means for focusing the ultrasonic waves emitted by the ultrasonic transducers at one point in the subject and performing a plurality of operations for detecting reflected ultrasonic waves from the inside of the subject by changing the focusing position of the ultrasonic waves, Signal processing means for performing processing for taking out the signal from the defective portion in the subject by averaging the signals of the reflected ultrasonic waves obtained from the respective focusing positions in the subject, and It is a thing.

[0008]

[Operation] By using the arrayed probe in which the ultrasonic transducers are arranged in an array, the timing of the pulse signal supplied to each ultrasonic transducer is controlled, and the ultrasonic waves emitted by each ultrasonic transducer are controlled. Is focused on one point in the subject to detect reflected ultrasonic waves. The detection operation is performed a plurality of times by changing the focusing position, and the detection results are added and averaged to reduce electrical echoes and forest echoes, and a signal of reflected ultrasonic waves from the defect portion is extracted. Detecting a defective part inside the subject with high spatial resolution by fixing the position of the arrayed probe and changing the ultrasonic focus position in the depth direction of the subject and performing multiple measurements. You can

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an ultrasonic flaw detector which is an embodiment of the present invention, FIG. 2 is a diagram for explaining the principle of the ultrasonic flaw detector, and FIG. 3 is a diagram for explaining a method of driving an ultrasonic transducer. FIG.

The ultrasonic flaw detector 10 of this embodiment has an arrayed probe 1 in which a large number of ultrasonic transducers 1a are arranged in an array, an object A and the arrayed probe 1 through water. The array unit 1 has a coupling unit 2 for accommodating the array-shaped probe 1 and a control unit 3 for controlling driving of the array-shaped probe 1 and the like. The control unit 3 not only has a function as a drive control unit and a signal processing unit, but also performs all electrical control of this device. Although not shown, the control unit 3 is provided with various switches, a display device, and the like as in the conventional device. Further, in the present embodiment, the steel material A that is the subject is assumed to be transported in the left-right direction in FIG.

The control unit 3 issues a pulse signal to each ultrasonic transducer 1a of the arrayed probe 1 coupled to the subject A via water. Upon receiving the pulse signal, each ultrasonic transducer 1a emits ultrasonic waves to the subject A. Here, the ultrasonic waves emitted by each ultrasonic transducer 1a are set at a specific position,
For example, in order to focus the ultrasonic waves on the position shown in FIG. 1, it is necessary to vibrate each ultrasonic vibrator 1a so that the ultrasonic waves emitted from each ultrasonic vibrator 1a reach the position at the same time.
Therefore, in the present embodiment, the timing of the pulse signal to be sent to each ultrasonic transducer 1a is gradually changed to a substantially arc shape as shown in FIG. As a result, the ultrasonic waves emitted by each ultrasonic transducer 1 can be focused on one point. After passing the focus point, the focused ultrasonic wave spreads again, reaches the back surface of the subject A, is reflected here, and returns to the front surface of the subject A. The reflected ultrasonic waves returning to the surface of the subject A are
The ultrasonic waves are received by the array-shaped probe 1, converted into an electric signal by each ultrasonic transducer 1 a, and sent to the control unit 3.

A position for focusing such flaw detection (see FIG. 2).
In the case of, the depth is changed in 5 steps. The focusing position can be deepened by adjusting the timing shift of the pulse signal supplied to each ultrasonic transducer 1a, that is, by reducing the arcuate curvature shown by the one-dot chain line in FIG. By increasing the curvature, the focus position can be made shallow. Therefore, according to the present embodiment, it is possible to easily change the focus position of ultrasonic waves. In this way, FIG. 2 (a) changes the focusing position to 5
FIG. 2B shows a state in which the flaw detection is performed, and the waveform on the left side of FIG. 2B shows the signal of the reflected ultrasonic wave detected when the beam is focused at each position to. In the case of FIG. 2A, since the defective portion exists at the focus position, the reflected ultrasonic wave from the defective portion is detected most when the ultrasonic wave is focused at the position. Even when focused at other positions ,,, although it is deviated from the defective portion, it is possible to obtain an echo according to the intensity of the ultrasonic wave hitting the defective portion.

Reflected by the back surface of the object A, a defective portion, etc.,
Also when extracting the reflected ultrasonic waves returning to the surface of the subject A, the detection timing of the ultrasonic transducer 1a is shifted. In this case, the method of shifting is to add the signals after delaying the received signals from the ultrasonic transducers by the same delay time as when the ultrasonic waves were generated. The control unit 3 reduces various kinds of noise and detects a signal from the defective portion by performing an averaging process on the signals of the reflected ultrasonic waves thus extracted. In the case shown in FIG. 2, the reflected ultrasonic wave from the defect becomes the largest when the ultrasonic wave is focused on the position,
The amplitude of the reflected ultrasonic wave from the defect portion in other flaw detection becomes small. However, the ultrasonic waves reflected from the defect portion have the same phase, although the amplitudes thereof are different for each flaw detection, so that they appear at the same position of the output signal waveform as shown by the waveform on the left side of FIG. 2B. . On the other hand, in the forest echo, the ultrasonic wave generated differs for each flaw detection performed five times, and therefore the appearance thereof changes for each flaw detection. Therefore, it is possible to reduce electrical noise and forest echoes and extract reflected ultrasonic waves from the defective portion by performing averaging processing on the signal waveforms at each of the five flaw detections. This improves the SN ratio.

The conventional ultrasonic flaw detector shown in FIG. 4 reduces the forest echo by shifting the flaw detector position, obtaining a plurality of flaw detection signals, and subjecting the plurality of flaw detection signals to an averaging process. We are trying to improve the SN ratio. However, since the flaw is detected by shifting the probe position, it can be seen that the detected defect is within the shifted range, but it is unknown at which position it is, and therefore the spatial resolution is reduced. . On the other hand, in the present embodiment, it is possible to perform flaw detection a plurality of times as quickly as it can be considered that the position of the array probe is fixed, so that the defective portion inside the subject is detected with high spatial resolution. be able to. For example,
If the steel plate thickness is 200 mm, the reciprocating distance is 400 mm
Since the longitudinal wave sound velocity in the steel material is 5900 m / s, the ultrasonic wave propagation time in this steel material is 400 mm / 5900 m / s = 68 μs. That is, since the ultrasonic wave propagates through the subject at a very high speed, even if the subject is transported, the moving distance of the subject during the propagation of the ultrasonic wave is extremely small and can be ignored. The flaw repetition frequency is about 1 kHz.
(1 ms is required for one flaw detection). Therefore, in order to make the moving distance of the object in five flaw detections negligible, for example, 0.5 mm, the moving speed of the object is (0.5 mm ÷ 1 ms) / 5 = 100 mm / s. That is, the moving speed of the subject is 100 mm / s.
In this case, the defective portion inside the subject can be detected with high accuracy of 0.5 mm.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention. For example, in the above embodiment, the case where the ultrasonic transducers are linearly arranged has been described, but the ultrasonic transducers may be arranged in a ring and arranged in a concentric circle. . As a result, the ultrasonic waves can be focused on one point more efficiently than when they are arranged linearly.

In the above embodiment, the case where the focus position of the ultrasonic waves is changed in the depth direction of the subject has been described, but the focus position can be changed in the transport direction of the subject.

[0017]

As described above, according to the present invention, the ultrasonic wave generated by each ultrasonic transducer is transmitted to the inside of the subject by using the arrayed probe in which the ultrasonic transducers are arrayed. The operation of focusing on one point and detecting the reflected ultrasonic wave of the ultrasonic wave is performed multiple times by changing the focusing position, and the measurement results are added and averaged to reduce electrical echoes and forest echoes. The signal from the defective part can be taken out,
In addition, by fixing the position of the arrayed probe and changing the focus position of ultrasonic waves in the depth direction of the subject and performing multiple measurements, the defect inside the subject can be detected with high spatial resolution. It is possible to provide an ultrasonic flaw detector that can do the above.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an ultrasonic flaw detector according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of the ultrasonic flaw detector according to the present embodiment.

FIG. 3 is a diagram for explaining a driving method of an ultrasonic transducer.

FIG. 4 is a diagram for explaining the principle of a conventional ultrasonic flaw detector.

[Explanation of symbols]

 1 Array-shaped probe 2 Coupling part 3 Control part 1a Ultrasonic transducer 10 Ultrasonic flaw detector A A subject

Claims (3)

[Claims] 1. An ultrasonic flaw detector for detecting defects in a subject by generating ultrasonic waves inside the subject and detecting reflected ultrasonic waves from the inside of the subject. By arraying arrayed probes and controlling the delay time of the drive pulse given to each of the ultrasonic transducers, the ultrasonic waves generated by each of the ultrasonic transducers are focused on one point in the subject, Drive control means for performing a plurality of operations of detecting reflected ultrasonic waves from the inside by changing the focal position of the ultrasonic waves, and adding and averaging the signals of the reflected ultrasonic waves obtained from the respective focusing positions in the subject. An ultrasonic flaw detection apparatus comprising: a signal processing unit that performs a process of extracting a signal from a defective portion in a subject. 2. The ultrasonic flaw detector according to claim 1, wherein the subject is a steel material. 3. An ultrasonic wave is generated by each ultrasonic transducer by controlling the driving order of the ultrasonic transducers by using an array probe in which the ultrasonic transducers are arranged in an array. Focusing on one point in the subject, the operation of detecting the reflected ultrasonic waves of the ultrasonic waves is performed multiple times by changing the focusing position, and the obtained multiple reflected ultrasonic waves are averaged and processed from the defective portion. The ultrasonic flaw detection method characterized by extracting the signal of