JP4738243B2 - Ultrasonic flaw detection system - Google Patents

Description

  The present invention relates to an ultrasonic flaw detection system having an ultrasonic flaw detection apparatus that scans an inspection object, and more particularly to an ultrasonic flaw detection system that can easily and reliably detect an inspection object.

  In general, the ultrasonic flaw detection system is used for accurately obtaining inspection results such as presence / absence and size of defects in ultrasonic inspection. In ultrasonic inspection, ultrasonic waves are transmitted from one or a plurality of ultrasonic transmission devices to the inspection object, ultrasonic waves reflected on the defect or bottom surface are received by the ultrasonic reception device, and the received ultrasonic data indicates the defect. Existence and size are measured.

  Here, in order to measure the presence / absence and size of a defect, it is necessary to perform determination by performing signal processing on ultrasonic data obtained by ultrasonic inspection. When the inspection target surface is a flat surface, the inspection range is narrow, and the assumed defect is a simple shape such as a slit and further vertical flaw detection, a time gate and a threshold value are applied to the ultrasonic data, for example. Defects can be detected with sufficient accuracy with a certain degree of processing.

  However, the actual surface to be inspected has irregularities, and it is difficult to inspect defects with a simple method having a complicated shape such as SCC (Stress Corrosion Cracking). Phased array ultrasonic flaw detection is performed as a method for accurately measuring the depth of defects with complex shapes such as SCC, but the data obtained is complicated, and a skilled inspector manually captures the data. The current situation is that defects are detected while looking.

  In phased array flaw detection, a plurality of methods have been proposed for data evaluation, but it is common to identify the position and depth of a defect by detecting the maximum value of the reflected echo from the defect. In order to detect the maximum value, a skilled inspector obtains an approximate position of the defect by looking at the ultrasonic intensity distribution in the cross section to be inspected called a B scope, and in detail, the ultrasonic waveform at the position where there is a possibility of a defect The position and depth of the defect are evaluated from the connection of the maximum echo values from the crack.

  As described above, manual operations by skilled workers are used for detecting defects. However, for example, in shroud inspections at nuclear power plants, the number of data is enormous, and the amount of work and burden on the inspectors is small. large. Furthermore, since the above evaluations vary depending on the skill of the inspector, it is currently the case that a plurality of inspectors perform the evaluation a plurality of times, and it is desired to reduce the burden on the inspector and improve the inspection efficiency. Yes.

  As a method for detecting the maximum value in order to detect the above-mentioned defect, it is proposed to automatically detect the maximum value by providing a gate to the ultrasonic signal and performing peak hold or comparison with a threshold value in the gate. ing.

  For example, by providing a peak hold circuit and a latch circuit for the detected ultrasonic waveform signal, it is possible to automatically determine whether the waveform is dumped or a signal from a different position without setting the gate time. A device for detecting the maximum value has been developed (see Patent Document 1).

Proposals have also been made to devise information provision means from the viewpoint of assisting inspectors. For example, a menu display has been devised so that a beginner or an expert can operate according to their skill (see Patent Document 2).
Japanese Patent Application No. 05-288128 Japanese Patent Laid-Open No. 11-174029

  In the current ultrasonic inspection system, it is necessary to evaluate ultrasonic signal data in detecting defects, but the problem is that the number of data is enormous and the load on the inspector is high. Further, since the data has a large variation (noise), the measurement result of the position and depth of the defect depends on the skill of the inspector, and the detection accuracy may not be obtained.

  In the ultrasonic flaw detection data evaluation apparatus disclosed in Patent Document 1, the maximum value of the ultrasonic signal is automatically detected when the waveform peak of the ultrasonic flaw detection signal is detected. For this reason, in the ultrasonic signal from a simple defect such as a slit shape, the influence of damping or the like can be automatically eliminated, and the defect can be automatically detected.

  However, for a defect having a complicated shape such as stress corrosion cracking (SCC), useful information may be included in the adjacent part. However, when Patent Document 1 is used, the information from the adjacent part disappears. Therefore, accurate defect measurement is difficult.

  In the menu display device of the ultrasonic flaw detector of Patent Document 2, the load on the inspector is reduced by switching the display according to the skill of the inspector. However, it is manual to identify the position and depth of the defect. It must be judged with. As described above, various proposals have been made in the evaluation of ultrasonic flaw detection data. However, a technique for simultaneously improving the detection accuracy and reducing the load on the inspector has not been developed.

  The present invention has been made in consideration of such points, and provides an ultrasonic flaw detection system capable of accurately and easily flaw-detecting a defect to be inspected using a maximum value of an ultrasonic signal. The purpose is to do.

The present invention scans an inspection target and continuously transmits and receives ultrasonic waves, an ultrasonic flaw detector that receives an ultrasonic signal from the sensor, and an ultrasonic signal received by the ultrasonic flaw detector. Based on the maximum value detection device for detecting the maximum value at different inspection locations, the storage device for storing the maximum value detected by the maximum value detection device, the scanning speed of the sensor, the flaw detection angle and the thickness of the inspection object, The maximum value interval prediction calculation device for obtaining the interval between the maximum values when the ultrasonic signals obtained at different positions are reflected from the same defect, and between two continuous maximum values among the maximum values stored in the storage device Is compared with the interval between the maximum values obtained by the maximum value interval prediction calculation device, and it is determined whether or not two consecutive maximum values correspond to ultrasonic waves from the same defect, and the defect depth is determined. The desired comparison operation Location and an ultrasonic flaw detection system characterized by comprising a display device for displaying the defect depth determined by the comparison operation unit.

The present invention scans an inspection object and transmits / receives ultrasonic waves at a predetermined flaw detection angle, an ultrasonic flaw detection device that receives an ultrasonic signal from the sensor, and an ultrasonic flaw detection device that receives an ultrasonic flaw detection device. Maximum value detection device that detects local maximum values at different consecutive inspection locations based on sound wave signals, storage device that stores local maximum values detected by the local maximum value detection device together with the detection time, sensor scanning speed, and flaw detection Based on the angle and the thickness of the object to be inspected, the maximum value interval prediction calculation device for obtaining the interval between the maximum values when the ultrasonic signals obtained at different positions are reflected from the same defect, and the maximum value stored in the storage device Among the values, the interval between two consecutive maximum values is compared with the interval between the maximum values obtained by the maximum value interval prediction calculation device, and the two consecutive maximum values are compared with the ultrasonic waves from the same defect. Whether it determined to an ultrasonic flaw detection system characterized by comprising a display device for displaying the maximum value for successive.

  According to the present invention, a defect to be inspected can be detected accurately and easily and reliably without depending on the skill of the inspector.

First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the ultrasonic flaw detection system 10 has a piezoelectric element portion 1 a that scans the inspection object 2 and is arranged in large numbers, and transmits and receives ultrasonic waves at a predetermined flaw detection angle. Type phased array sensor 1, ultrasonic flaw detector 4 that receives an ultrasonic signal from phased array sensor 1, and maximum value detection that detects a maximum value based on ultrasonic signal 101 received by ultrasonic flaw detector 4 The apparatus 11 includes a storage device 12 that stores the maximum value detected by the maximum value detection device 11 together with the detection time.

  In addition, the ultrasonic flaw detector 4 calculates the difference in the time of flight of the ultrasonic waves when the ultrasonic signals obtained at different positions are reflected from the same defect based on the scanning speed of the sensor, the flaw detection angle and the thickness of the inspection object. Then, a maximum value interval prediction calculation device 13 for obtaining an interval between the maximum values is connected. Further, the storage device 12 calculates the continuity of the ultrasonic waveform at different positions from the storage device 12 and the maximum value interval prediction calculation device 13, and if it is determined to be continuous, the maximum value is determined from the defect. A comparison operation device 14 that calculates the depth of the defect is connected as being reflected ultrasonic waves.

  The defect depth obtained by the comparison calculation device 14 is displayed on the display device 6.

  Among the above components, the data analysis device 5 is configured by the maximum value detection device 11, the storage device 12, the maximum value interval prediction calculation device 13, and the comparison calculation device 14.

  The focus type phased array sensor 1 in which a plurality of piezoelectric sensors 1a are arranged as shown in FIG. 2 is scanned on the inspection object 2 to perform ultrasonic flaw detection at a plurality of positions. A defect 3 is formed on the back surface of the inspection object 2.

  The phased array sensor 1 is driven by the ultrasonic flaw detector 4, and the ultrasonic signal 101 obtained via the cable 1 b is analyzed by the data analyzer 5 for analysis and displayed on the display device 6.

  There are other devices that realize the functions necessary for ultrasonic flaw detection, such as a function for controlling the ultrasonic oscillation timing of the phased array sensor 1, an AD conversion function, and an addition circuit, all of which are the ultrasonic flaw detector 4 include. The scanning direction of the phased array sensor 1 is x, the depth direction of the inspection target is y, the flaw detection angle 102 is θ, and the entire phased array sensor 1 is moved by Δx during the inspection. Instead of actually moving the sensor 1, a technique of obtaining ultrasonic data at a plurality of points having position information, such as electronic scanning, may be used.

  Next, the operation of the present embodiment having such a configuration will be described.

  First, the phased array sensor 1 scans the inspection target 2 having the defect 3 on the back surface, and during this scanning, ultrasonic waves are transmitted from the phased array sensor 1 to the inspection target 2, and the superposition from the inspection target 2 is detected. Sound waves are received by the phased array sensor 1.

  The ultrasonic signal received by the phased array sensor 1 is sent to the ultrasonic flaw detector 4 via the cable 1b, and the ultrasonic signal is further sent from the ultrasonic flaw detector 4 to the data analyzer 5 for data analysis. .

  Data analysis in the data analysis device 5 will be described below.

First, a data processing method in the maximum value detection device 11 of the data analysis device 5 will be described. First, in order to detect the time for the reflected ultrasonic wave to return from the defect opening or the defect end with respect to the ultrasonic signal 101 input from the ultrasonic flaw detector 4 at the position Pos ₁ , a maximum value is set for each ultrasonic signal. To detect. An example of the local maximum detection method is shown in FIG.

For the input waveform (FIG. 3A), the center frequency band of each sensor is f _c (Hz), and the resolution of the built-in AD converter is f _sampling (Hz) (f _sampling > f _c ). When, performing the peak hold with f _sampling / f _c or more points (Figure 3 (b)). In FIG. 3B, for simplicity, peak hold is performed with f _sampling / f _c × 5 times the number of points. Next, thinning is performed on the data subjected to peak hold with the same number of points as the peak hold (FIG. 3C). When the thinned data is compared with the preceding and succeeding data and the point is maximum, the corresponding point in the original waveform is searched and the point is taken as the point where the maximum value of the ultrasonic waveform is taken (FIG. 3 ( d)), the detected n local maximum values are stored in the storage device 12 as a matrix Peak ₁ (i) = (t _pi , L _pi ) (t: peak time, L: local maximum level).

By this processing, the influence of damping and noise can be reduced, and the maximum value in the obtained ultrasonic signal can be easily obtained. It is still difficult to determine whether or not the ultrasonic signal is reflected from the defect opening or the defect end because there is a possibility of influence of noise or the like on the data of one point of the maximum value. Therefore, the above-described processing is performed for the position Pos ₂ (= Pos ₁ + Δx) where the sensor has moved to obtain a matrix of peak values Peak ₂ (i), and whether or not the maximum values are continuously generated at successive inspection points. Find out. This makes it possible to determine whether the ultrasonic wave is reflected at the actual defect opening or the defect edge or noise.

In order to determine whether or not the maximum values are continuous, the maximum value interval prediction calculation device 13 calculates the difference between the time t _pi at Peak ₁ (i) at Pos ₁ and the time t _pj at Peak ₂ (j). Calculate from physical positional relationship. In order to explain the method of calculating the maximum value interval, a positional relationship as shown in FIG. 4 is assumed.

In FIG. 4, for simplicity, the divergence (spreading) of the ultrasonic waves is not considered, the directivity of the sensor is ignored, and only the ultrasonic waves from only the defect opening are considered. Further, as shown in the figure, the flaw detection angle is θ, and the thickness of the inspection object is D. Pos ₁ is a position where the defect opening coincides with the directivity angle of the sensor, and Pos ₂ is a position scanned from Pos ₁ by ΔX. In calculation, the propagation distance of ultrasonic waves in Pos ₁ (one way) is D / cosθ (1)
And the propagation distance of ultrasonic waves in Pos ₂ (one way) is ((D ・ tanθ−Δx) ^ 2−D ^ 2) ^ 0.5 (2)
It is.

So the maximum at Pos ₂ is
t _pi + [{(D · tanθ−Δx) ^ 2−D ^ 2} ^ 0.5− (D / cosθ)] / Sv (3)
(Sv is the speed of sound in inspection object 2).

The comparison arithmetic unit 14 creates a gate using the maximum value time t _pi obtained at Pos ₁ , and if the maximum value time t _pj at Pos ₂ is within the gate, Peak ₁ (i) And Peak ₂ (j) can be considered to be echoes from the same defect opening or defect end.

The example in FIG. 4 is an extreme example in which the portion where the ultrasonic level is thought to be strongest at the defect opening is written as Pos ₁ , and in fact, the point before Pos ₁ (for example, Pos ₀ and Pos ₁ ) is the time. The interval becomes longer, and the time interval becomes shorter at the previous points (for example, Pos ₂ and Pos ₃ ). Similarly, the time interval changes at the defect end. Therefore, in actuality, instead of searching for a point where t _pi and t _pi + [{(D · tanθ−Δx) ^ 2−D ^ 2} ^ 0.5− (D / cosθ)] / Sv match,
| T _pi -t _pj | <[{(D · tanθ−Δx) ^ 2−D ^ 2} ^ 0.5− (D / cosθ)] / Sv ± δ
(Δ is set in accordance with the inspection condition), the comparator 14 determines that the echoes are from the same defect opening or defect end.

In the comparison arithmetic unit 14, this process is repeated with Pos ₀ and Pos ₁ , Pos ₁ and Pos ₂ , Pos ₂ and Pos ₃ ..., Thereby obtaining a continuous matrix of local maximum values LM1 (i), LM2 (i). .., And those having a small number of elements in each matrix are excluded from the candidates of ultrasonic waves reflected from the defect opening or the defect edge (as a result, LMa (i), LMb (i) The maximum value in each matrix of maximum values is obtained (assuming LMa_t and LMb_t). Of these, the one with the longest time is the reflected ultrasonic signal from the defect opening, and the other maximum value is the reflected ultrasonic signal from the defect end. Thereby, the arrival time of the ultrasonic signal from the defect opening and the defect end part can be obtained from the flaw detection waveform from which the maximum value of the defect end ultrasonic signal candidate is obtained, and the depth of the defect can be automatically identified.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS.

  In the first embodiment described above, an example in which the depth of a defect is automatically identified has been described. However, in the case of a complex defect such as an actual stress corrosion crack, a human judgment is finally required. In such a case, the continuity of the maximum value may be displayed on the display device 6. By displaying the continuity of the maximum value on the screen of the display device 6 in this way, the efficiency of the inspector's defect recognition can be improved. For example, it is assumed that ultrasonic waves are transmitted and received at five locations as shown in FIGS. 6A to 6E, and ultrasonic signals as shown on the right side of FIGS. 6A to 6E are obtained. When the same processing as that of the first embodiment is performed on the obtained ultrasonic signal, the maximum value of the ultrasonic signal from the defect opening and the end is obtained as shown in FIGS. It can be displayed with continuous solid lines.

  As can be seen from FIGS. 6A to 6E, the change in the reflected ultrasonic maximum value from the defect opening is clearly displayed, and the inspector only sees FIG. , B has a crack opening ”can be easily detected.

  FIG. 7 shows the result of data processing at the time of actual ultrasonic inspection (in this example, there is no reflection from the crack end, only reflection from the defect opening). FIG. 7 shows a plurality of lines indicating continuity in addition to the change in the maximum value of the reflected ultrasonic wave from the defect. The reflected ultrasonic wave from the defect opening is positioned as the phased array sensor 1 is scanned. Clearly changes. In the second embodiment, the continuity of only two points is checked and displayed. However, even if processing such as increasing the number of points or setting a threshold value on the level and not setting a low level as a maximum point is performed. Good.

The figure which shows 1st Embodiment of the ultrasonic flaw detection system by this invention. BRIEF DESCRIPTION OF THE DRAWINGS The figure for demonstrating the outline of 1st Embodiment of the ultrasonic flaw detection system by this invention. The figure for demonstrating the method of detecting the maximum value from an ultrasonic signal. The figure for demonstrating the method of detecting the maximum value from an ultrasonic signal. The figure which shows 2nd Embodiment of the ultrasonic flaw detection system by this invention. The figure which shows the surface sound wave signal which changes according to scanning. The figure which shows the example which detected the continuity of local maximum. The figure which shows the display result at the time of applying 2nd Embodiment to real data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Phased array sensor 1a Piezoelectric element part 2 Inspection object 3 Defect 4 Ultrasonic flaw detector 5 Data analysis apparatus 6 Display apparatus 11 Maximum value detection apparatus 12 Memory | storage device 13 Maximum value space | interval prediction calculation apparatus 14 Comparison calculation apparatus

Claims (2)

A sensor that scans the inspection object and transmits and receives ultrasonic waves;
An ultrasonic flaw detector for receiving an ultrasonic signal from the sensor;
A maximum value detecting device for detecting a maximum value at different consecutive inspection points based on an ultrasonic signal received by the ultrasonic flaw detector;
A storage device for storing the maximum value detected by the maximum value detection device;
Based on the scanning speed of the sensor, the flaw detection angle, and the thickness of the inspection object, a maximum value interval prediction calculation device for obtaining an interval between the maximum values when the ultrasonic signals obtained at different positions are reflected from the same defect ,
Of the maximum values stored in the storage device, the interval between two consecutive maximum values is compared with the interval between the maximum values obtained by the maximum value interval prediction calculation device, and the two consecutive maximum values are the same. A comparison operation device for determining whether or not to deal with ultrasonic waves from the defect and obtaining the defect depth;
A display device for displaying the defect depth determined by the comparison operation device;
An ultrasonic flaw detection system comprising: A sensor that scans the inspection target and transmits and receives ultrasonic waves at a predetermined flaw detection angle;
An ultrasonic flaw detector for receiving an ultrasonic signal from the sensor;
A maximum value detecting device for detecting a maximum value at different consecutive inspection points based on an ultrasonic signal received by the ultrasonic flaw detector;
A storage device for storing the maximum value detected by the maximum value detection device together with the detection time;
Based on the scanning speed of the sensor, the flaw detection angle, and the thickness of the inspection object, a maximum value interval prediction calculation device for obtaining an interval between the maximum values when the ultrasonic signals obtained at different positions are reflected from the same defect ,
Of the maximum values stored in the storage device, the interval between two consecutive maximum values is compared with the interval between the maximum values obtained by the maximum value interval prediction calculation device, and the two consecutive maximum values are the same. A display device for determining whether to respond to ultrasonic waves from a defect, and displaying a continuous maximum value;
An ultrasonic flaw detection system comprising:

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