JPS5917154A - Method and device for detecting defect by ultrasonic wave method - Google Patents

Abstract

PURPOSE:To discriminate a defect accurately in the direction, inclination, size, and depth, by transmitting and receiving an ultrasonic wave beam which crosses the center of rotation in a flaw detection area in a material to be inspected, and finding the correlation between a flaw detection pattern and a preset reference pattern. CONSTITUTION:A probe rotating mechanism 7 is scanned by a scanning mechanism 23 in an X-axis and a Y-axis direction, and the scanning mechanism 23 is cotrolled by a controller 24. Pulser receivers 25-28 are provided corresponding to probes 14'17 of four channels CH1-CH4. While the probe rotating mechanism 17 is rotated, ultrasonic wave beams 14a-17a are transmitted to the material 2 to be inspected by the probes 14-17 during flaw detection, and then a reflection echo from the defect 3 in the material 2 to be inspected is received by the pulser receivers 25-28 through the probes 14-17; and analog peak holding circuits 29-32 hold the peak values of signals generated at flaw detection gates 14b- 17b, and 128 flaw detection patterns of every 360 deg./128 from the incidence direction are stored through A/D converters 33-36 and shift registers 37-40 to generate a flaw detection pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for detecting defects using an ultrasonic method, and is capable of detecting the direction, inclination, size, and depth of defects such as horizontal defects occurring inside a material at high speed. However, in order to determine the degree of harmfulness of the defect, horizontal hole-shaped cavities may occur in the cast material due to gas trapped inside during the @-casting process. In this case, in many cases, the shape of the defect and its harmfulness to material strength have been clarified depending on the purpose of use, and for some types of cast materials, the harmfulness of the defect is determined by the plane transparency. It is defined by the size on the shadow map. However, due to the directionality of the stress applied to the material, the level of harm is usually different depending on whether a horizontal hole-like defect of the same length is located in the X direction or in the Y direction. Conversely, the size of defects that can be tolerated in terms of material strength usually differs between the X direction and the Y direction. Under such circumstances, the shape of the horizontal hole defect (
It is necessary to accurately recognize the direction, inclination, and size.

As a method for detecting such internal defects, an ultrasonic method in which an ultrasonic beam is transmitted inside a material to be inspected and echoes from the defect are received has been provided and put into practical use. However, in the conventional ultrasonic method, the probe is simply moved in a predetermined direction within the flaw detection area of the material being tested and the echoes are captured. The elements that can be determined from are extremely limited.
, it was difficult to completely capture the shape of a horizontal hole-like defect. Therefore, the present inventors developed an oblique probe that transmits and receives an ultrasonic beam so as to intersect the rotation center in the flaw detection area inside the test material. The angle probe is rotated around zero during rotation while transmitting and receiving ultrasonic beams from each direction of 360°.
A method in which the peak value of the echo generated within the flaw detection gate is displayed as a flaw detection pattern on a display medium in correspondence with the incident direction of the ultrasonic beam, and the direction, inclination, size, and depth of the defect are determined from this flaw detection pattern. invented. This has the advantage of being able to reliably recognize the shape, ie, direction, inclination, size, and depth of defects inside the specimen, unlike conventional ultrasonic methods.

However, since there is only one probe, in order to identify the depth, it is necessary to repeat the same operation several times while changing the flaw detection depth, which has the disadvantage that the flaw detection time is somewhat longer. Since the hazardousness of defects is determined by the worker, there is no particular problem when detecting small materials, but it cannot be used when detecting particularly large materials, and the hazardousness level is determined by on-site online flaw detection. It cannot be said that it can be determined.

In view of these problems, the present invention uses a plurality of angle probes with different flaw detection depths at the same time and obtains flaw detection patterns of multiple channels, thereby gaining insight into the depth all at once. The defect information included in the flaw detection pattern is decoded using a correlation method, and the degree of harmfulness is determined online in a very short time.
The feature of this is that when detecting defects inside the test material using the ultrasonic method, the ultrasonic beam is transmitted and received so as to intersect the rotation center in the flaw detection area inside the test material, and the flaw detection depth is different. Using a multi-channel angle probe, each channel's angle probe is rotated around 0 and 360 degrees, and ultrasonic beams are transmitted and received from each direction from 360 degrees to perform flaw detection on each channel. By creating multiple flaw detection patterns in which the peak value of the echo generated in the gate corresponds to the incident direction for each channel, and finding the correlation between each of these flaw detection patterns and a preset reference pattern, the direction of the defect can be determined. , the inclination, size, and depth are deciphered and the harmfulness of the defect is determined from the results.The second feature is that defects inside the specimen are detected by ultrasonic method. The device includes a multi-channel bevel probe that transmits and receives an ultrasonic beam so as to intersect the center of rotation in a flaw detection region inside the material to be inspected and has different flaw detection depths, and the bevel probe is rotated as described above. In addition to being equipped with a probe rotation mechanism that rotates the probe around the center, each probe is equipped with a means for holding the peak value of the echo generated in the flaw detection gate of each channel and creating a flaw detection pattern corresponding to the incident direction. Correspondingly, a memory for storing multiple types of success/failure patterns is provided, and a digital correlator is provided for determining the correlation between the flaw detection pattern of each channel and the reference pattern. There is a way to decipher the depth and determine the degree of harm.

Next, the present invention will be explained in detail. Figure 1 (Shu (B) shows a horizontal hole-like defect (3) with an inclination η in the side to be examined (2) by angle-angle ultrasonic flaw detection using an oblique angle probe f+ with a refraction angle θ). The path of the ultrasonic beam (4) when causing a wound is shown. However, θ〉
Let it be η. As shown in Figure 1 (A) and (B), the probe (
When the ultrasonic beam (4) is transmitted while rotating the ultrasonic beam (4) once around the rotation center from the starting line position (the position in the elongated direction when the defect is projected onto the material surface) in the direction of the arrow, the ultrasonic beam (
4) is incident perpendicularly to the defect (3), α from the starting line
There are two directions: 1 and α22 rotated positions. This is shown using the symbols in the figure: P→Q-+R→Q→P and pl→Q1→
It is shown as R1→Q+→R1. Therefore, it can be seen from a simple geometrical calculation that there is a relationship between α, η, and θ as shown in the following equation.

. . , ,! 'u22jl)-ichishi-l,
■2 tanθ Actually, when rotating the probe (1), from h, Fig. 1 (B)
If the ultrasonic beam (4) is transmitted and received along the trajectory C of the incident point shown in Figure 2, and the peak value of the echo obtained at that time is plotted against the incident direction α, the flaw detection pattern shown in Figure 2 is obtained. is obtained. The angle-related characteristics of such a flaw detection pattern are determined by the formula 0, and the maximum peak value is determined by the defect (
It is determined by the size of 3). For the relationship between the size of the defect (3) and the echo height, a conventional flaw detection equation can be used, or an actual value from an artificial defect can be used. From this, it can be seen that the flaw detection pattern shown in FIG. 2 includes information on the direction, inclination, and size of the defect (3).

Usually, the direction of the starting line is a special direction of the shape of the material to be inspected (2),
For example, since the longitudinal direction is selected, the direction of the defect (3) is measured from such a starting line. The direction of defect (3) is then given by the following equation.

Medium+180° (β2-β1-18o)
(2) Also, the slope η of defect (3) can be obtained from the following equation.

. . 8 (pregnancy J1-) = 轡1 2 tan19 (β2-β1-18o) ■
0 β2−β1 also anηcos (1B
O--) = tan-j (β2-β, 〉1800)■
Such an operation can be performed by a person with graphic recognition ability, but it requires a large amount of time. On the other hand, from a practical point of view, it is sufficient to be able to detect and judge defects from 0 to 45 with an error of 2.5 degrees. took advantage of the law.

The cross-correlation process is given by the following equation.

C(Sl = ---5,,"0r(αl f (a+
S) d a ■60 Here, f (ffl, r @l is an arbitrary function defined as O≦α≦360. Cross-correlation processing has recently been used in pattern recognition technology in image processing and error detection in communication technology. This invention is applied to correction techniques, etc., but the present invention considers the shape of the flaw detection pattern, compares the unknown flaw detection pattern with a known reference pattern, and considers it to be similar to the reference pattern with the highest degree of similarity. A brief explanation of this process is as follows.
The figure shows one flaw detection pattern and five types of reference patterns r1
An example of 4m - β5 (at is shown below. In the case of humans, the number of peaks, the distance between peaks, and the slope of the peaks can be compared using the original pattern recognition function. Then, the overlap between the detection pattern and the reference pattern can be compared. , and determine that it is the same as β4 (-), which has the greatest degree of overlap. Such an operation is a correlation process, and it is quantitatively determined to what extent the types match. Therefore, the formula 0 was introduced as a value proportional to the area of the overlapping parts.

S in Equation 0 is the offset needle on the horizontal axis when two patterns are superimposed as described above.

In this case, the volume pattern is originally created from a horizontal hole-like artificial defect by actual measurement or by division according to the 0 formula, and the characteristics (direction, inclination) of these artificial defects are not known. Therefore, the amount of deviation S gives the deviation between the direction of the artificial defect and the direction of the defect just detected.

Applying the above principle, a reference pattern with the same direction, length, and depth of the reflective surface, and with an inclination of 0.5.10.
15. 20. 25. 30. 35. 40. 45 γ Mouth By preparing the results obtained from 0 types of horizontal hole artificial defects and correlating them with the flaw detection pattern just obtained,
The direction and inclination of defects can be detected. Defect classification can be best achieved by keeping the maximum value constant for the reference pattern at this time.

In addition, as the correlation method is often used in signal processing to improve S/N, it is also effective when the flaw detection pattern includes a lot of noise as shown in Figure 4. It is extremely difficult for a machine to perform operations such as measuring the number of peaks and the distance between peaks for a flaw detection pattern (which is the usual case in actual flaw detection).

Next, embodiments of the defect detection device according to the present invention will be described. Figures 5 and 6 show a four-probe type detection device using the local water immersion method. ) is provided with a water tank (6) that is movable over the test material (2), a probe rotation mechanism (7) is disposed inside this water tank (6), and water ( 8) is supplied.

The probe rotation mechanism (7) has a cylindrical rotating shaft (02) which is rotatably held in a bearing case (11) on a support plate (5) via a bearing +91 flol, and this rotating shaft (12). The probe holder (13) has a probe holder (03) attached to the lower end, and the probe holder (13) has four probes arranged at a pitch of 90° in the circumferential direction.
The bevel probes (14) (151 (161 (lη) are built in. The probes (14IQ(5)Q61Q71 detect flaws in a range of 20111M from the surface of the test material (2) at a pitch of 8H. Each probe Q41Q5) θ chain (171 is, for example, an ultrasonic beam (14a) (15a) with a refraction angle θ of 45°).
The beam diameter of (16g) and (17a) is 9.2mm,
As shown in FIG. 7, each ultrasonic beam (14a) (1
5g) (16a) (17a) depth 2.5, f, 5.1
2.5.17.5 They are arranged at slightly different distances from the rotation center so as to intersect with the rotation center at the MM position. Therefore, when the probe (+41Q5) Q61 (Iη) is rotated once, the respective flaw detection gates (x4b) (t5b
) (16b) (t7b), the detection area becomes a 9-ball shape (shaded area) as shown in FIG. 7, and it is possible to capture echoes of defects within this range. (18) is a motor that drives the probe rotation mechanism (7), Q9) is a rotary encoder that detects the rotation angle of the probe rotation mechanism (7), and these are attached to the support plate (5). 0 (221 is the probe rotation mechanism (7)) which is interlocked and connected to the rotating shaft (i) through the belt transmission mechanism (2rli (211)).
61 [171K] This is a slip ring for transmitting and receiving ultrasonic signals.

FIG. 8 shows a block diagram of the signal processing device, and the operation during flaw detection will be explained with reference to FIG.

(5)) is a scanning mechanism that scans the probe rotation mechanism (7) in the X-axis and Y-axis directions, and (24) is a controller that controls this scanning mechanism (23). □□□ and 6 rise η and 8) is 4
Channel (CHl) (CHs+) (CH3XCH4)
probe f14+ 05) ([1 (pulsar receiver provided corresponding to +η, Q29) (support)) Ct++
ea is an analog peak hold circuit, which holds each probe (14) while rotating the probe rotation mechanism (7) during flaw detection.
1 (151961Q) When ultrasonic beams (14a) (15a) (16a) (17a) are transmitted to the inspection material (2), the reflection from the defect (3) in the inspection object (2) occurs. The echo is loved by the probe (141 (lfil (1610η) and the pulsar receiver (2 hills (261'7)), and the flaw detection gate (14b) (15b) (16b) (17
Analog peak hold circuit (29) ((0) (311j3'): h
le)-f le. (331 (34! (31m) (361
is the peak value wo'/1) converter, C(7j (3R1(3
! l+ (41'i is a shift register, (360
728) It goes without saying that a peak value from the 128 incident direction for each channel, that is, a flaw detection hole is created for each channel in accordance with the incident direction. @1) is RAM, ROM @
10s of reference patterns are stored in this memory, as will be described later. (4) is a data selector, [(8) is a digital correlator, which performs correlation processing between the flaw detection pattern sent to each channel through the data selector (42) and the reference pattern stored in the memory (41). (44) is a digital peak detector that detects the maximum value of the correlation value between the flaw detection pattern of each channel and the reference pattern.

The amount of deviation S at this time is detected by a data latch (4ri1. The maximum value Cmi (1=1.2.3.4) of the correlation value for each channel detected in this way and the amount of deviation Si ( i = 1.2.3.4), and the current position (χ, y) of the scanning mechanism (z3) is determined by the data selector (4
6) and stored in the shift register (47). Note that the signal processing after the digital correlator (43) can be executed by software using a computer as described later, but in that case it usually takes a long time.0 Output of the digital correlator (43) Figure 9 shows the D/A conversion of
As shown in the figure. Defect (3) at this time is shown in Figure 11 (A) (
As shown in B). The slope η of defect (3) is 24°, and it can be seen from the figure 9 that it has the maximum correlation with the reference pattern of 25°. Also, since the peak value of the correlation is shifted from the center (=0) by +60, this defect (3
) is found to be at an angle of 60° with respect to the specific direction of the test material (2).

Such a judgment is actually an interface (48)
By transferring the data in the shift register (4'fl) to a computer (not shown) through the transfer register, it can be executed easily and at high speed.The processing in the computer will be described below.

As shown in Figure 7, the ultrasonic beam ft of each channel
4a) flsA) (t6a) (t7a) is the test material (2
), significant correlation values Cmi appear in multiple channels from one defect (3). Therefore, in that case, the depth of the reflecting surface of defect (3) is calculated using the following formula.Next, the deviation of the reflecting surface of defect (3) from the center line of the ultrasonic beam is corrected.

Cmi = (1+k'-”Lee) Cmi
■1 Here, k is a proportionality constant that depends on the probe diameter, frequency, etc. The length of the defect (3) can be determined from the Cmi thus obtained. FIG. 12 shows the actual measured value (marked with an X) of the maximum correlation value between the flaw detection pattern obtained from a defect with a diameter of φ2, a length of l, and an inclination of 35° and a reference pattern with an inclination of η=35°. From such data, it is possible to calculate the effect that the received sound pressure deviation is less than the correlation value and determine k.

During flaw detection, the XY position of the probe rotation mechanism (7) (corresponding to the XY position of the defect) is controlled by the controller (24).
Shift register (47) via data selector
The data is stored in the computer via the interface +41'Q and transferred to the computer along with data such as the maximum correlation value.

Then, this data is later displayed on the CRT as position information of the defect (3) when displaying the detection data of the harmful defect. In FIG. 8, (49) is a timing controller. The probe rotation mechanism (7) can also be replaced with an electronic scanning probe. Figure 13 i, j: Signals when shape recognition of defect (3) is performed on the software of computer I0) This is a block diagram showing the flow of
The same names as in FIG. 8 are given the same reference numerals, and the description thereof will be omitted. In this case, the pulsar receiver (2r+l
(261 (2η (2), analog peak hold circuit (29) (2)) ('rl+cqz and A/D converter 4'1314'+4+(g) (3G), probe (
141(+51
- Store in Jl+ and create a flaw detection pattern. The memory (51) is an external memory of the computer (a), and before the probe (14) (If+06) αη transmits and receives the first ultrasound beam in the next rotation, the memory (Jl) node is stored by DMA. Search for patterns in the internal memory via the power interface (15z).
Transfer to. The computer (60) has a CPU (541,
CRT display (6(5),
It has a floppy disk (561, etc.) for storing flaw detection data.

Computer (2) processes the signal according to the flowchart shown in FIG. In Fig. 14, the flaw detection pattern is indicated by Ai (φ, the subscript 1 is the channel, and α is the rotation angle. The reference pattern is indicated by Rj (α), and j indicates the slope of the defect. Ai ( The correlation equation between Rj and Rj(α) is given by: This equation is generally provided as software.

A case will be described in which the present invention is applied to flaw detection of a cast propeller (57). This propeller (571 flaw detection area (1
'iR' is as shown in the shaded area in Figure 15 < 1200x8
It is a 00ff rod and the flaw detection depth is QQMM from the surface.

The horizontal hole-shaped defects (3) included in this flaw detection area (68) are detected, and only harmful defects are output from them, but the harmful defects of the propeller vJ7) are determined by considering the direction of stress. Evaluation is made using the projected length lo in the circumferential direction. The degree of harm also varies depending on the depth 9 of the tip of the defect (3). Therefore,
The harmfulness of defect (3) is defined by the defect projected length lo shown in FIGS. 16(A) and 16(B) and the defect tip depth q shown in FIG. 17. From this, computers (Zui,
The following is performed as final processing.

(1) Calculation of defect projection length la = Zcoe η+ 5ind
D where l is the actual length of the defect, η is the slope of the defect, and α is the direction of the defect with the starting line in the radial direction.

(11) Calculation of defect tip depth q q=Max [0, (d-+esinη)]
DHere, d is the center depth of the defect 01 () Determination of whether or not to output the defect When O≦q10 J? o≧4 drunkenness ■0≦9≦2
When 0 /! . ≧811nI ■This is defined as the allowable projected defect size in two stages.

Jutte, Computer (translation) 'B, Figure 15 (7>
70-Calculate ■ and ■ as shown in the chart 7,
When any of the conditions described in Using angle probes, these probes are rotated simultaneously while transmitting and receiving ultrasonic beams, and the peak value of the echo generated within the flaw detection gate of each channel is captured to obtain a flaw detection pattern. Unlike the case with a probe, it is not necessary to test the same spot several times while changing the detection depth, and the work can be carried out more efficiently.Also, it is possible to correlate the flaw detection pattern with a preset reference pattern. This method uses a method to decipher the direction, inclination, size, and depth of the defect by determining the defect's direction, inclination, size, and depth, and to judge the degree of harmfulness of the defect from the results, which requires less computer and hardware resources than when determining from the detection pattern itself. It is easy to make a judgment by a machine using a logic circuit, and in this respect, speeding up can also be promoted.

The device of the present invention is equipped with a probe rotation mechanism that rotates a plurality of channel angle probes around zero during rotation, and the probe is directly rotated by this probe rotation mechanism. ,
The configuration is simpler than when using an electronic scanning probe. In addition, since the correlation between the flaw detection pattern and the reference pattern is determined using a digital correlator, high-speed online detection is possible, and subsequent signal processing is facilitated. This method has the advantage that the processing time can be shortened compared to the case where the method is used.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present invention, and FIG. 1 (A) and (B) are explanatory diagrams showing the path of the ultrasonic beam, FIG. 2 is a waveform diagram of a flaw detection pattern, and FIG. An explanatory diagram of correlation processing, @Figure 4 is a waveform diagram of an actual flaw detection pattern, Figure 5 is a sectional view of the probe rotation mechanism, Figure 6 is a bottom view of a part of the probe holder, and Figure 7 is a diagram of the waveform of the actual flaw detection pattern. An explanatory diagram of the flaw detection area, FIG. 8 is a block diagram, FIG. 9 is a waveform diagram when the output of the digital correlator is D/A converted, and FIG. 10 is a slope diagram. Waveform diagrams of flaw detection patterns obtained from 24 defects, FIGS. 11A and 11B are explanatory diagrams of the defects, and FIG. 12 is an explanatory diagram showing the relationship between the length of the defect and the ratio of the maximum correlation value, Figure 13 is a block diagram, Figure 14 is a flowchart, Figure 15 is a partial plan view of the propeller, Figures 16 (A) and (B) are illustrations of harmful defects, and Figure 17 is the depth of the tip of the defect and allowable projection. It is an explanatory view showing the relationship with defect length. (1) (141Q6) (lFilθη...angle flaw detector, (2)...test material, (3)...defect, f41
(14a) (15a) (16a) (17a) --- Ultrasonic beam, f71 --- Probe rotation mechanism, (tab) (
xsb) (16b) mb)...flaw detection gate, (company) (
26) (27) (2. Pulsar receiver, (29) (
b)) (3) Analog peak hold circuit,
4')71 (38)139) (4n'r...A
/D converter, (41) Q10... memory, (43)
...digital correlator, (hn)...computer.

Claims (1)

[Claims] 1. # When detecting internal defects on the lateral side using the ultrasonic method, an ultrasonic beam is transmitted and received so as to intersect the rotation center in the flaw detection area inside the test material, and the flaw detection depths are different. Using a multi-channel bevel probe, the bevel probe of each channel is rotated around its rotation center while transmitting and receiving ultrasonic beams from each of 360 directions to detect flaws generated within the flaw detection gate of each channel. By creating multiple flaw detection patterns in which the echo peak value corresponds to the incident direction for each channel, and finding the correlation between each of these flaw detection patterns and a preset reference pattern, the direction, inclination, and size of the defect can be determined. , a method for detecting defects using an ultrasonic method, characterized by decoding the depth and determining the degree of harmfulness of the defect from the result. 2. In a device that detects defects inside a test material using the ultrasonic method, an ultrasonic beam is transmitted and received so as to intersect the rotation center in the flaw detection area inside the test material, and multiple channels with different flaw detection depths are installed at different angles. It is equipped with a probe and a probe rotation mechanism that rotates the angle probe around the rotation center, and also holds the peak value of the echo generated in the flaw detection gate of each channel to correspond to the incident direction. A means for creating a flaw detection pattern corresponding to each probe is provided, a memory for storing multiple types of reference patterns is provided, and a digital correlator is provided to obtain a correlation between the flaw detection pattern of each channel and the reference pattern. What is claimed is: 1. A defect detection device using an ultrasonic method, characterized in that the device is provided with means for determining the degree of harmfulness by deciphering the direction, inclination, size, and depth of a defect from a pattern formed by the defect.