JPH06148151A - Ultrasonic flaw detecting method and device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to suppress the secondary pole with high accuracy without being affected by the hardware configuration of the linear array probe and the defect detection conditions. [Structure] Each of the reflected echo signals output from each of the elements 20, 20, ... Of the linear array probe 2 in response to the received reflected echo is impulse-converted by an impulse processor 6, and the respective impulse-converted reflections are performed. The echo signal is sent to the delay device 7,
Are delayed by 7, ..., Each delayed reflected echo signal is added by the adder 8, and the defect of the inspected material is detected based on the added reflected echo signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method and apparatus for detecting defects in a material to be inspected using ultrasonic waves.

[0002]

2. Description of the Related Art As a flaw detection method for detecting a defect of a material to be inspected such as a steel material, an ultrasonic flaw detection method for detecting a defect using an ultrasonic wave is performed. As the ultrasonic flaw detection method, elements for transmitting and receiving ultrasonic beams are arranged in parallel in one direction at a predetermined interval, and the ultrasonic beams transmitted from the respective elements are phase-matched to determine a predetermined material to be inspected. A method is known in which an ultrasonic beam is focused on a position and a defect is detected by using a linear array probe in which reflected echoes are received by each element.

In the method of detecting a defect using the linear array probe, a predetermined number of elements selected to perform a transmitting / receiving operation in order to form a focused ultrasonic beam at a certain position among all the elements. Electronic linear scanning that moves the focusing position of the ultrasonic beam on the inspected material in the direction in which the elements are arranged side by side by switching the groups, and the deflection angle of the ultrasonic beam is changed while each element group is driven. By,
Electronic sector scanning for changing the focus position of the ultrasonic beam within a predetermined range is performed.

However, when the ultrasonic beam is focused by using the linear array probe as described above, the ultrasonic beam is positioned at a position other than the target focusing position (hereinafter referred to as the main pole) as shown in FIG. Are focused and a secondary pole is generated. FIG. 5 is an explanatory diagram showing a generation state of the auxiliary pole. In the figure, 20, 20, ... Are elements of the linear array probe, and the ultrasonic beams transmitted from each element 20, 20 ,, ... Focus on M. However, since the elements 20, 20, ... Of the linear array probe are arranged in a discrete manner, due to the interference phenomenon of the ultrasonic beam, they are located at a position G (hereinafter referred to as a sub-pole) G other than the target main pole M. Also the ultrasonic beam is focused. When the secondary pole G is generated, a reflected echo having a high level other than the primary pole M is detected, so that the defect detection accuracy is deteriorated.

The appearance azimuth θ _G (angle from the center of the probe) of the sub-pole G is the element pitch (element spacing) P, the wavelength λ of the ultrasonic beam and the deflection angle θ _{0 of the main} pole M (probe). It is geometrically expressed by the following equation (1) by the angle from the center of.

Θ _G = sin ⁻¹ (λ / P ± sin θ ₀ ) ... (1)

The condition for the absence of the auxiliary pole G in the equation (1) is that sin θ _G is larger than 1, that is,
In the case where the element pitch P is smaller than half the wavelength λ of the ultrasonic beam, the element pitch P may be made small in order to prevent the generation of the auxiliary pole G. However, when the element pitch P is reduced in this way, the reason is as follows.
The number of elements that perform transmission / reception operations (hereinafter referred to as the number of simultaneously driven elements) to form a focus at a certain position is increased.

Equation (2) below is the beam width W of the ultrasonic beam.
It is an expression showing the relationship between _b , the wavelength λ, the number N of simultaneously driven elements, the element pitch P, and the focal depth Z.

W _b = 2 · [λ / (N · P)] · Z (2)

As shown in the equation (2), the beam width W _b of the ultrasonic beam has a characteristic that it becomes wider as the element pitch P becomes smaller, and it becomes narrower as the number N of simultaneously driven elements increases. . For this reason, if the element pitch P is reduced as described above, the beam width W _b may be widened and the defect detection accuracy may be degraded. Therefore, when the element pitch P is reduced, the simultaneous drive element number N is also increased. It is increased to suppress the expansion of the beam width W _b .

In this way, when the element pitch P is reduced and the number N of simultaneously driven elements is increased to suppress the generation of the auxiliary pole G, the maximum deflection angle of the main pole M, the focal depth, the measurement accuracy requirement, etc. are required. The element pitch P and the number N of simultaneously driven elements of the linear array probe are determined based on the defect detection condition and the hardware configuration of the detection apparatus, and the element pitch P and the number N of simultaneously driven elements are realized. It is necessary to use a linear array transducer.

Further, as a method of suppressing the generation of the auxiliary pole G, the interference of the ultrasonic beams is suppressed by shortening the pulse duration T _d of the ultrasonic beams transmitted from the respective elements 20, 20 ,. There is a method of suppressing the generation of the auxiliary pole G. In this method, if the ratio (T _d / T _c ) between the pulse duration T _d and the period T _{c of the} ultrasonic beam becomes small, each element 20, 2
This is because the ultrasonic beam transmitted from 0, ... Does not interfere with the appearance direction θ _G of the auxiliary pole G.
However, in order to realize this method, the pulse duration T
_It is necessary to create a special transducer with a short _d .

[0013]

However, the element pitch P
In the conventional method of suppressing the generation of the auxiliary pole G by using the linear array probe in which the number of simultaneously driven elements is increased while reducing the number of elements, in the linear array probe, the element pitch P and the simultaneously driven elements are set. When detecting a defect under a detection condition different from the detection condition used when determining the number N,
There has been a problem that the sub pole G cannot be suppressed sufficiently.

Also, the pulse duration T _{d of the} ultrasonic beam
In order to realize the conventional method of shortening the pulse duration, it is necessary to manufacture a special linear array probe having a short pulse duration T _d, but the reduction of the pulse duration T _d is limited by the hardware configuration. Therefore, there is a limit to the suppression of the auxiliary pole G.

The present invention has been made in view of such circumstances, and it is possible to suppress the auxiliary pole with high accuracy without being affected by the hardware configuration of the linear array probe and the defect detection condition. It is an object of the present invention to provide a method and apparatus for ultrasonic flaw detection.

[0016]

According to an ultrasonic flaw detection method of the present invention, a focused ultrasonic wave is incident on a material to be inspected from a linear array probe having a plurality of elements for transmitting and receiving ultrasonic waves arranged in parallel. Then, the reflected echo is received by each element, in the ultrasonic flaw detection method for detecting the defect of the material to be inspected based on the reflected echo signal representing each received reflected echo,
Each of the reflected echo signals received by each element is impulse-converted, a predetermined delay according to the focusing position is added to each impulse-converted reflected echo signal, and each delayed reflected echo signal is added. The defect of the material to be inspected is detected based on the added reflected echo signal.

In the ultrasonic flaw detector according to the present invention, a focused ultrasonic wave is incident on a material to be inspected from a linear array probe in which a plurality of elements for transmitting and receiving ultrasonic waves are arranged in parallel, and the reflected echo is reflected. Received by each element, in the ultrasonic flaw detector for detecting the defect of the material to be inspected based on the reflected echo signal representing each received reflected echo, each of the reflected echo signals received by each element A means for performing impulse conversion, means for adding a predetermined delay to the respective reflection echo signals impulse-converted by the means according to the focus position, and means for adding the respective reflection echo signals delayed by the means. The defect of the material to be inspected is detected based on the reflected echo signal added by the means.

[0018]

In the present invention, each of the reflected echo signals is impulse-converted to shorten the duration of the signal. Then, each of the impulse-converted reflected echo signals is added after a predetermined delay according to its focus position (main pole), and at this time, the reflected echo from the main pole position is Because they match, they strengthen each other.
On the other hand, since the duration of each impulse-converted reflected echo signal has been shortened, phase matching of the reflected echo from the sub-pole position is less likely to occur during delay and addition calculation of each reflection echo signal, and The reflected echo signal of
It is suppressed compared to the reflection echo from the main pole position.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram showing the configuration of an ultrasonic flaw detector according to the present invention.

In the figure, reference numeral 1 is a material to be inspected, which is composed of a large number of elements 20, 20, ... Which transmit and receive ultrasonic beams arranged in parallel at a predetermined interval, and which are transmitted from each element 20, 20 ,. The ultrasonic beam is focused on a predetermined position of the inspected material 1 by phase matching the ultrasonic beam to be generated, and the reflected echo is reflected by each element 2
The linear array probe 2 receiving at 0, 20, ... Is arranged on the steel pipe 1 through water (not shown).

This linear array probe 2 has all its elements.
Of 20, 20, ..., By sequentially switching a predetermined number of element groups selected to perform transmission / reception operation in order to form a focus of an ultrasonic beam at a predetermined position, The electronic linear scanning, which is a scan for moving the focusing position of the ultrasonic beam in the direction in which the elements are arranged, is performed, and the ultrasonic beam transmitted from each of the elements 20, 20, ... When each of the element groups is driven. By changing the timing, it is possible to perform electronic sector scanning, which is scanning for changing the deflection angle of the phase-matched ultrasonic beam within a predetermined range.

Each of the elements 20, 20, ... Of the linear array probe 2 has a large number of pulse signals for exciting them.
It is designed to be given by each of 3 ,. However,
The number of pulsers 3, 3, ... Is the same as the number N of simultaneously driven elements in each element group, and the pulse signals from the pulsers 3, 3 ,. It is given to the element group. The driving timing of each of the pulsers 3, 3, ... Is controlled by a pulser drive controller 4, and the pulser drive controller 4 preliminarily performs the electronic linear scanning and the electronic sector scanning. A drive timing signal is given to the pulsers 3, 3, ... At a predetermined timing. Each element 20, 20, ... Is excited by the pulse signal, transmits an ultrasonic beam to the inspected material 1, and receives a reflection echo from the inspected material 1.

Each of the reflected echoes received by each of the elements 20, 20, ... Is converted into an electric signal (referred to as a reflected echo signal), and the reflected echo signals are individually amplified by the amplifiers 5, 5 ,.
Given to. The reflected echo signals given to the amplifiers 5, 5, ... Are amplified and given to the impulse processor 6.

The impulse processor 6 includes A / D converters 61, 61,
... and arithmetic units 62, 62, ..., and is an A / D converter
61, 61, ... A / D convert the respective reflection echo signals (analog signals) given from the amplifiers 5, 5 ,.
The reflected echo signal (digital signal) after A / D conversion is given to each of the computing units 62, 62, .... The arithmetic units 62, 62, ... Perform impulse conversion by numerical calculation such as Wiener filtering processing or L1 norm processing on the reflected echo signal after A / D conversion, and convert the reflected echo signal into a spike-shaped impulse signal. Convert. In this way, the respective reflected echo signals impulse-processed by the impulse processor 6 are given to the respective delay devices 7, 7 ,.

In the delay devices 7, 7, ..., The reflection echo signals supplied from the impulse processor 6 are delayed as shown below to match the phases of the respective reflection echo signals obtained from the main pole position. And gives it to the adder 8. The reflected echo signal obtained by the reflection of the ultrasonic beam at the focal position (main pole position) on the surface of the material 1 to be inspected is received by each element 20, 20 ,.
The distance to 0,20, ... differs for each element 20,20, ...
The reception timing of the reflected echo signal differs for each of the elements 20, 20, .... That is, the element 20 having a short distance from the focal position
Has a reception timing of the reflected echo signal earlier than that of the element 20 having a long distance.

Therefore, in the delay devices 7, 7, ...
Based on the value of the distance at 20, 20, ..., The delay time is set for each of the elements 20, 20, ..., such that the respective phases of the reflected echo signals from the main pole position to be output match. By delaying its output by the delay time, the reflected echo signals whose phases are matched are given to the adders 8, respectively.

The adder 8 adds (adds) the respective reflected echo signals given from the delay devices 7, 7, .... In this case, since the reflected echo signals from the main pole position are in phase with each other, they are strengthened (the level is increased) in the adder 8. The reflected echo signal added by the adder 8 is given to the display 9. In the display unit 9, the adder 8
The reflected echo signal given from the device is displayed on the screen as the result of defect detection.

In the ultrasonic flaw detector having the above-mentioned structure, the ultrasonic beam is emitted by the linear array probe 2 to be inspected.
When the ultrasonic beam is focused on the target position (main pole), the ultrasonic beam is focused on the position (sub-pole) other than the target position due to the interference phenomenon of the ultrasonic beam. Therefore, the reflection echoes received by the elements 20, 20, ... Of the linear array probe 2 include the reflection echoes from the main pole position and the reflection echoes from the sub-pole position. If the reflected echo signals related to the reflected echoes are each added as they are after a predetermined delay according to the focus position, and if they are added, phase matching of the reflected echo signals from the sub-pole position is likely to occur, and as a result, A relatively large reflected echo signal of is detected. When such a signal is used as it is as a defect detection signal, the peak of the reflection echo signal related to the sub pole appears in the detection signal in addition to the peak of the reflection echo signal related to the main pole,
Defect detection accuracy decreases.

Therefore, the impulse processor 6, the delay units 7, 7, ... And the adder 8 perform signal processing for suppressing the sub-pole. The signal processing will be described below.

In the impulse processor 6, the reflected echo signal is impulse-converted, and by the conversion, the reflected echo signal is shaped as shown in FIG. Figure 2 (a),
2 (b) is a waveform diagram showing the relationship between the original waveform of the reflected echo signal and its waveform after impulse conversion. The original waveform is shown in FIG. 2 (a) and the waveform after impulse conversion is shown in FIG. 2 (b). 2A and 2B, the vertical axis represents signal amplitude and the horizontal axis represents time.

As shown in FIGS. 2 (a) and 2 (b), the reflected echo signal has its signal duration T by impulse conversion.
a is shortened and the signal becomes a spike-like impulse signal having a short signal duration Tb. When the signal duration of the reflected echo signal is shortened in this way, in the signal delay processing performed by the delay device 7 and the signal addition processing performed by the adder 8, reflection from a portion other than the main pole position is performed. Phase matching is less likely to occur in the echo signal, and the sub-pole component is easily suppressed.

The respective reflected echo signals that have been made into impulses are made to have the phases of their main pole components matched by the delay devices 7, 7, ... And added by the adder 8. In this case, the reflected echo signals are reflected. Since the main pole components of the signals are in phase with each other, when the signals are added, they are strengthened by phase matching and the main pole component is emphasized. On the other hand, the sub-pole component of each reflected echo signal does not match the phase of the main pole component in each reflected echo signal, as described above. Therefore, when the signals are added, they are weakened by phase mismatch. Fit, removed or suppressed.

Next, the result of actual defect detection using the ultrasonic flaw detector as described above will be described. In this detection, the linear array probe 2 is about 5 times the width of the simultaneous drive element group of the linear array probe 2 with respect to the inspected material of a steel ball with a diameter of 0.3 cm submerged in water. The linear array probe 2 is arranged so that the distance is the depth of focus, and the deflection angle of the linear array probe 2 is 0 degree, and the deflection angle is 30 degrees.
Regarding the case, defect detection was performed between the case where the above-described impulse processing was executed and the case where the impulse processing was not executed.

3 (a) and 3 (b) show the scanning position of the linear array probe 2 with and without the impulse process under the condition that the deflection angle is 0 degree. FIG. 3 is a waveform diagram showing the relationship with the amplitude of the reflected echo signal, showing the relationship between the reflected echo signal amplitude on the vertical axis and the scanning position of the linear array probe 2 on the vertical axis, and FIG. FIG. 3A shows the above relationship when the impulse processing is not executed, and FIG. 3B shows the above relationship when the impulse processing is executed.

If the impulse processing is not executed,
As shown in FIG. 3 (a), on both sides of the main pole M, the main poles M and 20
Clear sub-poles G and G with dB difference appear, but when impulse processing is executed, the difference between the main pole M and 26 dB is near the main pole M as shown in Fig. 3 (b). Only a very small sub-pole G appears, and when the impulse processing is executed as apparent from this figure, the sub-pole G is sufficiently suppressed.

FIGS. 4 (a) and 4 (b) show the scanning position of the linear array probe 2 with and without the impulse process under the condition that the deflection angle is 30 degrees. FIG. 4 is a waveform diagram showing the relationship with the amplitude of the reflected echo signal, showing the relationship between the reflected echo signal amplitude on the vertical axis and the scanning position of the linear array probe 2 on the vertical axis, and FIG. FIG. 4A shows the relationship when the impulse processing is not executed, and FIG. 4B shows the relationship when the impulse processing is executed.

When the impulse processing is not executed,
As shown in FIG. 4 (a), in the vicinity of the main pole M, the main poles M and 6
Although there is a clear sub pole G with a difference of dB, when impulse processing is executed, there is a difference of 18 dB with the main pole M in the vicinity of the main pole M as shown in Fig. 4 (b). Only the minute auxiliary pole G appears, and when the impulse processing is executed as is clear from this figure, the auxiliary pole G is sufficiently suppressed.

In the present embodiment, the impulse conversion is executed by numerical calculation such as Wiener filtering processing or L1 norm processing. However, the present invention is not limited to this, and the reflected echo signal is converted into impulses by using a pulse generator and a comparator. Is also good.

[0039]

As described above in detail, in the ultrasonic flaw detection method and apparatus according to the present invention, the impulse conversion of the reflection echo signals, the delay of each impulse-converted reflection echo signal, and the delay of each delayed reflection echo signal. Since the auxiliary pole is removed by signal processing such as addition, the auxiliary pole can be suppressed with high accuracy without being affected by the hardware configuration of the linear array probe and the defect detection condition.
The present invention has excellent effects.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram showing a relationship between an original waveform of a reflected echo signal and a waveform after its impulse conversion.

FIG. 3 shows the relationship between the scanning position of the linear array probe and the amplitude of the reflected echo signal when the impulse process is not executed and when the impulse process is executed under the condition that the deflection angle is 0 degree. It is a waveform diagram.

FIG. 4 shows the relationship between the scanning position of the linear array probe and the amplitude of the reflected echo signal in the case where the impulse process is not executed and the case where the impulse process is executed under the condition that the deflection angle is 30 degrees. It is a waveform diagram.

FIG. 5 is an explanatory diagram showing a generation state of a sub pole.

[Explanation of symbols]

 1 material to be inspected 2 probe 6 impulse processor 7 delay device 8 adder 20 elements

Claims (2)

[Claims] 1. A focused ultrasonic wave is incident on a material to be inspected from a linear array probe in which a plurality of elements for transmitting and receiving ultrasonic waves are arranged in parallel, and the reflected echo is received by each element,
In the ultrasonic flaw detection method for detecting defects in the material to be inspected based on the reflection echo signals representing the respective reflection echoes received, each of the reflection echo signals received by each of the elements is impulse-converted and impulse-converted. A predetermined delay according to the focusing position is added to each reflected echo signal, each delayed reflected echo signal is added, and the defect of the inspected material is detected based on the added reflected echo signal. Characteristic ultrasonic flaw detection method. 2. A focused ultrasonic wave is made incident on a material to be inspected from a linear array probe in which a plurality of elements for transmitting and receiving ultrasonic waves are arranged in parallel, and the reflected echo is received by each element,
In the ultrasonic flaw detector for detecting defects in the material to be inspected based on the reflection echo signals representing the respective reflection echoes received, means for impulse converting each of the reflection echo signals received by each of the elements, Means for adding a predetermined delay according to the focus position to each reflected echo signal impulse-converted by the means, and means for adding each reflected echo signal delayed by the means, and added by the means An ultrasonic flaw detector, wherein a defect of the material to be inspected is detected based on a reflected echo signal.