JP2722087B2 - Ultrasonic flaw detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic flaw detector, and more particularly to an ultrasonic flaw detector suitable for automatic ultrasonic flaw detection having a complicated surface shape.

[Conventional technology]

As one method of ultrasonic flaw detection aimed at precise flaw detection,
There is a water immersion automatic flaw detection method in which a subject is immersed in water, and the surface of the subject is scanned for flaws by an ultrasonic probe in the water.

In the automatic water immersion flaw detection method, the distance between the ultrasonic probe and the subject is kept constant, and the direction of the center axis of the ultrasonic beam is measured on the surface of the subject in order to accurately know the size of the flaw. Must match the line direction.

Related devices of this type include those shown in the Japan Society of Mechanical Engineers, Vol. 90, No. 826, pp. 5-9, and JP-A-61-240158.

[Problems to be solved by the invention]

Of the above-mentioned prior arts, the former is capable of detecting a test object having a flat surface, but for a test object having a curved surface as shown in FIG. 3, the direction of the center axis of the ultrasonic beam is changed. Flaw detection was impossible because it was difficult to match the normal direction of the surface of the subject.

On the other hand, the latter has at least two for normal direction control.
Since more than one ultrasonic receiver is required, cost increase is unavoidable.

In addition, as shown in FIG. 8, when the surface of the subject has a flaw or the like, the reflected wave cannot be received due to the irregular reflection of the ultrasonic beam, so that the constant distance control and the normal direction control cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic flaw detection apparatus capable of detecting a test object having a curved surface with an inexpensive apparatus configuration and detecting a test object even when an ultrasonic beam is irregularly reflected.

[Means for solving the problem]

The present invention provides an ultrasonic probe that transmits ultrasonic waves to an object whose surface is not necessarily planar and receives a reflected wave, and detects a distance between the ultrasonic probe and the object to achieve the above object. Distance detecting means, distance constant control means for keeping the distance between the ultrasonic probe and the subject constant by a signal from the distance detecting means, and the direction of the center axis of the ultrasonic beam transmitted from the ultrasonic probe Normal direction control means for matching the direction of the normal line at each position on the surface of the subject, and flaw detection means for detecting the position by reflected waves from each position in the constant distance control and normal direction control state When the ultrasonic beam is irregularly reflected due to the influence of a flaw or the like existing on the surface of the subject and the reflected wave cannot be received, the distance is constant at least at two points before and after the position of the flaw and the like. Control and normal directions The distance and the normal direction at the position of such a flaw interpolation calculation by the results of the control, characterized by comprising means for performing distance constant control and the normal direction control in a position such as the flaw.

[Action]

The distance detecting means calculates the distance between the probe and the subject surface based on the time difference between the transmitted wave and the reflected wave from the subject surface,
Output to control means. The control means first moves the probe to the scanning initial position in accordance with a signal from the input means. Next, at the initial position, constant distance control is performed to keep the distance between the probe and the surface of the subject constant. The normal direction control is performed using one probe while keeping this distance constant, and the center axis of the ultrasonic beam is made to coincide with the normal direction of the surface of the subject. Thereafter, the surface of the subject is scanned while performing constant distance control and normal direction control, and ultrasonic flaw detection is performed.

On the way, if the ultrasonic beam is irregularly reflected due to a scratch on the surface and cannot receive the reflected wave, it moves a minute distance from there, performs constant distance control and normal direction control at the moved position, and then performs the opposite operation. Side, the same distance, and at that position, constant distance control and normal direction control are performed. Then, the position where the reflected wave from the subject surface cannot be received due to the distance between the probe and the subject surface at each position and the direction in which the center axis of the ultrasonic beam is directed, that is, the normal direction of the subject surface. The distance between the probe and the surface of the subject and the direction in which the center axis of the ultrasonic beam should be directed, that is, the normal direction of the surface of the subject, are interpolated. Therefore, returning to the position where the signal cannot be received, the diffuse reflection compensation control for setting the scanning condition based on the calculation result is performed, the scanning axis is driven, and the ultrasonic inspection is restarted.

By repeating these series of operations, flaw detection of the object having a curved surface is possible, and flaw detection of the object is possible even at a position where the ultrasonic beam is irregularly reflected.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment of the ultrasonic flaw detector according to the present invention. In the figure, 1 is an ultrasonic probe, 2 is a probe holder, 3 is a motor for θ axis, 4 is Z
Axis 5, motor for Z axis, 6 for X
A member driven in the axial and Y-axis directions;
Denotes recording means, 9 denotes distance detecting means, 10 denotes arithmetic control means, 11
14 to 14 are positioning means, and 15 is a subject.

When the motor 3 is rotated, the probe 1 rotates around the θ axis. When the motor 5 is rotated, the probe 1 moves in the Z axis, that is, in the vertical direction. The positioning means 11 to 14 are provided by a position command signal from the arithmetic and control means 10 and a signal from a position detector such as a potentiometer incorporated in each motor.
Determine the position in each axis direction.

FIG. 2 is a block diagram showing an example of the configuration of the distance detecting means 9. The distance detecting means 9 includes a transmitter 16 for transmitting an ultrasonic signal to the ultrasonic probe 1, a receiver 17 for receiving an ultrasonic signal reflected from the subject 15, and a timing circuit 18. The timing circuit 18 measures a time interval between a transmission signal from the transmitter 16 and an ultrasonic reflection signal from the surface of the subject 15 and outputs the time interval to the arithmetic and control unit 10. Assuming that this time interval is t and the velocity of sound in water is V, the distance m between the probe 1 and the surface of the subject 15 is m.
Is obtained by the following equation: m = Vt / 2 (1) The signal of the receiver 17 is output to the arithmetic and control unit 10 for normal direction control.

Next, taking the subject 15 shown in FIG.
Will be described. The constant distance control and the normal direction control are performed at positions a, b,..., E, f,.

In the subject 15 shown in FIG. 3, the surface normal direction has the scanning start point (A or B) and one scanning end point (A 'or B').
Is a member that does not change. The case where the subject 15 is scanned from the point A to the point B 'in the scanning order shown in the drawing will be described.

FIG. 4 is a flowchart showing the control contents of the arithmetic control means 10, FIG. 5 is a diagram showing a state in which the constant distance control and the normal direction control are completed, FIG. 6 is a flowchart of the normal direction control, FIG. FIG. 8 is a diagram showing a search position of a probe at the time of diffuse reflection compensation control, FIG. 8 is a diagram showing diffuse reflection of an ultrasonic beam, and FIG.
The figure shows the search operation of the probe during diffuse reflection compensation control.
FIG. 10 is a flowchart of the diffuse reflection compensation control.

In step 19 of FIG. 4, the probe 1 is positioned just above the scanning start point A, as shown by the broken line in FIG.

In the example of FIG. 5, although the normal direction of the point A of the subject 15 and the direction of the ultrasonic beam of the probe 1 are largely displaced, in actuality, the normal direction of the point A and the ultrasonic wave of the probe 1 The probe 1 is positioned so that the direction of the beam is almost matched, and is taught by offline teaching from the shape data of the subject 15 to a position where the reflected wave from the surface of the subject 15 can be received without fail. , For positioning the probe 1.

In step 20, it is determined whether the peak value of the reflected wave from the surface of the subject 15 can be detected at this position. As shown in FIG. 8, the reflected wave from the surface of the subject 15 can be received as long as the surface of the subject 15 is not damaged and the ultrasonic beam is not irregularly reflected.

In step 21, based on a signal from the distance detecting means 9, so that the distance m between the surface of the probe 1 and the specimen 15 reaches the predetermined value m _o, drives the Z axis motor 5. The state at this time is I in FIG. The predetermined value m _o is set from the input unit 7 according to the difference or the like of the characteristics of the probe 1.

In step 22, if only the θ axis is changed, the ultrasonic beam deviates from point A. Therefore, it is necessary to search the normal direction while irradiating the ultrasonic beam to the point A and controlling the distance between the probe 1 and the surface of the subject 15 to be constant. For this purpose, control may be performed so that the rotation center H of the probe 1 shown in FIG. 5 moves on a circle around the point A.

In FIG. 5, assuming that the position of H is (Y, Z), the position of point A is (Y _A , Z _A ), the distance from H to point A is l _o , and the rotation angle of probe 1 is θ. , Y _A = Y + l _ocos θ (2) Z _A = Z + l _osin θ (3) When rewritten, Y = Y _A− l _ocos θ (4) Z = Z _A− l _osin θ (5) Becomes Here, Y _A and Z _A are I when the constant distance control is completed.
In the condition (1), the calculation is performed from the equations (2) and (3), and is given to the positioning means 12 and 13. At the time of the normal direction control, the position command value of the Y and Z axes is simultaneously calculated by the equations (4) and (5) while changing θ.
And gives it to the positioning means 12 and 13.

 Next, the search operation in the normal direction will be described with reference to FIG.

 In step 27, the flag is set to "0".

In step 28, the lens is rotated by Δθ in the positive direction in which θ increases from the state of I in FIG. At this time, the Y and Z axes are also
Based on the equations (4) and (5), the robot moves by a very small position.

In step 29, the peak value of the surface reflected wave (voltage level of the receiver 17) is measured and compared with the previous peak value. The peak value of the reflected wave becomes highest when the ultrasonic signal is incident in the normal direction, and becomes lower as the reflected wave deviates from the normal direction.

As a result of the comparison in step 29, if the current peak value is higher than the previous peak value, that is, if the normal direction approaches, in step 30, the flag is set to 1 and the probe 1
Are rotated in the same direction by Δθ. This step is repeated, and if the current peak value is smaller than the previous peak value, that is, if the current peak value has passed the normal direction, it is determined in step 31 whether the flag is 1 or not.

If 1, the search in the normal direction has been completed, so
The operation then proceeds to step 32, in which the motor is rotated in the negative direction by Δθ. In the state where the process has proceeded to step 32, the probe 1 has passed the normal direction by Δθ, so that the probe 1 is to be corrected by that amount.

The control flow when the normal direction rotates Δθ in the negative direction will be described. In the case of a negative value, when compared in step 29, the result is that the current peak value is lower than the previous peak value,
Control passes to step 31.

At step 31, it is determined whether the flag is "1". However, since the flag has not passed through step 30, the flag is "0".

Then, the process proceeds to step 33, and steps 33 and 34 are repeated.
The normal direction control in step 22 in the figure is completed.

Next, the control moves to step 24 in FIG. 4, and moves from the point A to the point A '. Here, the process proceeds to step 25 to determine whether or not the flaw detection has been completed. However, since the flaw detection has not been completed at first, the process returns to step 26 to move by a predetermined distance. For example, the positioning is performed in the state III, which is moved by ΔY in the Y direction from the state I in FIG.

Returning to step 20, it is determined whether the peak value of the reflected wave from the surface of the subject 15 can be detected at this position. In this case, the probe 1 and the subject 1 are in the state of III in FIG.
The distance to the surface of 5 and the center axis of the ultrasonic beam and the subject 1
Although the normal direction of the surface of 5 is shifted, the movement distance to this position is very small.
The peak value of the reflected wave from the surface can be detected, and the process proceeds to step 21.

However, if there is a flaw or the like on the surface of the subject 15, as shown in FIG. 8, the distance between the probe 1 and the surface of the subject 15, the center axis of the ultrasonic beam, and the method Even if the line directions match, the reflected wave from the surface of the subject 15 cannot be received. Therefore, at such a position, the constant distance control and the normal direction control become impossible. In order to solve this, the irregular reflection compensation control in step 23 is executed.

The irregular reflection compensation control will be described with reference to FIG. 9 and FIG.

In step 36, the positive direction movement counter and the negative direction movement counter are cleared.

In step 37, for example, the robot moves a small distance in the positive Y-axis direction from the position indicated by the broken line IV in FIG.

In step 38, the forward movement counter is incremented by one in accordance with step 37.

In step 39, it is determined whether or not the peak value of the surface reflected wave from the surface of the subject 15 can be detected. If not, the process returns to step 37 and repeats this.

If it can be detected, at step 40, constant distance control and normal direction control are executed. This position is the position V in FIG. The data of the positions of the X, Y, and Z axes and the rotation angle θ of the probe 1 are stored, and in step 41, the process returns to the initial position, that is, the control start position IV.

In step 42, the robot moves a minute distance in the direction opposite to the previous direction. This minute distance is the same as the minute distance in the positive direction.

In step 43, the negative direction movement counter is incremented by one in accordance with step 42.

At step 44, it is determined whether or not the peak value of the surface reflected wave from the surface of the subject 15 can be detected, and if not detected, the process returns to step.

If it can be detected, at step 45, constant distance control and normal direction control are executed. This position is the position of VI in FIG. The data of the position of the X, Y, and Z axes and the rotation angle θ of the probe 1 are stored.

In FIG. 9, if the solid line of VI indicates that the normal direction of the surface of the subject 15 matches the center axis of the ultrasonic beam and the distance is a predetermined value, the position of L (X , Y,
Z) and the rotation angle can be calculated as follows.

The position of J is (X _J , Y _J , Z _J ), and the position of _K is (X _K , Y _K ,
Z _K ), and the rotation angles of the probe 1 are θ _J and θ _K , respectively.
As shown in the figure, even if the surface of the subject 1 is a curved surface, if the distance traveled by the diffuse reflection compensation control is very small, the distance between the two can be regarded as almost a straight line. X = (N · X _J + M · _{X K) / (M + N} ) ... (6) Y = (N · Y J + M · Y K) / (M + N) ... (7) Z = (N · Z J + M · Z K) / (M + N) ... (8 ) Θ = (N · θ _J + M · θ _K ) / (M + N) (9) Here, M is a positive direction movement counter value, and N is a negative direction movement counter value.

Using the equations (6) to (9), the position of the X, Y, and Z axes of IV in FIG.
Give to ~ 14. The moving distance of the diffuse reflection compensation control can be set from the input device 7. If there is a pair of information (B and C, D and E, F and G), the equations (6) to (9) can be calculated regardless of the direction in which the probe 1 is moved. It is.

After the diffuse reflection compensation control, the process proceeds to step 24, and the above steps 20 to 25 are repeated. When the probe 1 reaches the point B ', the flaw detection is completed.

Note that, as shown in FIG. 8, when the subject 15 has a large scratch and cannot receive a reflected wave from the surface of the subject 15 at all,
FIG. 4 is a flowchart showing the procedure for detecting the peak value in step 20.
Move on to 23 diffuse reflection compensation control. However, even if the surface of the subject 15 has a flaw, when the flaw is small, the peak value may be detected in some cases. If the normal direction control is performed for such a surface state, there is a possibility that the ultrasonic beam of the probe 1 cannot be positioned in the correct normal direction.

Next, an embodiment in which the ultrasonic beam of the probe 1 can be accurately positioned in the normal direction even in such a case will be described.

FIG. 11 is a flowchart showing the second control content of the arithmetic control means 10. Components other than steps 50 to 52 and having the same reference numerals as those in FIG. 4 are the same as those in FIG. In step 50, it is determined whether or not the peak value of the reflected wave from the surface of the subject 15 is equal to or greater than a specified value. Since the subject 15 is a continuum, the difference between the direction of the ultrasonic beam of the probe 1 and the normal direction of the surface of the subject 15 is small. For example, it can be seen that there is not much change in the normal direction at the positions g and h in FIG. For this reason, if there is no scratch on the surface of the subject 15, the peak value becomes a certain value or more. Therefore, when the peak value is not less than the specified value in step 50, the
Since the surface has a small flaw, the procedure shifts to the diffuse reflection compensation control in step 23.

Step 51 determines whether or not the direction of the ultrasonic beam of the probe 1 as a result of performing the normal direction control in step 22 is substantially the same as the result of the previous normal direction control. Subject
Since 15 is a continuum, the direction of the previous ultrasonic beam and the direction of the current ultrasonic beam should almost coincide with each other for the reason described above. For this reason, if the directions are significantly different, this is due to a wound that was missed in the check in step 50. Therefore, in that case, the procedure shifts to the diffuse reflection compensation control in step 23.

Step 52 stores the direction of the current ultrasonic beam for the next step 51.

Although illustration is omitted, in the diffuse reflection compensation control, step 50 is added after step 39 and step 44.
By inserting the steps 51 and 52 after the step 40 and the step 45, it is possible to cope with a small scratch on the surface of the subject 15.

The recording device 8 records the defect distribution of the subject 15 using the position signal of each operation axis of the receiver 17.

In the apparatus of the present embodiment, the flaw detection of an object having a curved surface can be performed even when a reflected wave from the surface of the object cannot be received due to irregular reflection of an ultrasonic beam. Moreover, since a special probe for controlling the normal direction is not required, an inexpensive ultrasonic flaw detector can be obtained.

In addition, since the ultrasonic beam scans the surface of the object at regular intervals, it is easy to draw a defect distribution map.

[Effects of the Invention] According to the present invention, flaw detection of an object having a curved surface is possible, and inexpensive flaw detection of an object can be performed even when a reflected wave from the surface of the object cannot be received due to irregular reflection of an ultrasonic beam. An ultrasonic flaw detector is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of the configuration of an ultrasonic flaw detector according to the present invention, FIG. 2 is a block diagram showing an example of the configuration of a distance detecting means, and FIG. 3 is an example of an object having a curved surface. FIG. 4 is a flowchart showing the control contents of the arithmetic control means, FIG. 5 is a view showing a state in which the constant distance control and the normal direction control are completed, and FIG. 6 is a diagram showing the normal direction control. FIG. 7 is a diagram showing a search position of a probe during diffuse reflection compensation control, FIG. 8 is a diagram showing diffuse reflection of an ultrasonic beam, and FIG. 9 is a search for a probe during diffuse reflection compensation control. FIG. 10 is a flowchart showing the position, FIG. 10 is a flowchart showing diffuse reflection compensation control, and FIG. 11 is a flowchart showing the second control content of the arithmetic control means. DESCRIPTION OF SYMBOLS 1 ... Ultrasonic probe, 2 ... Probe holder, 3 ... Motor for θ-axis, 4 ... Motor for Z-axis, 5 ... Motor for Z-axis, 6 ... Moving member in X and Y-axis directions, 7 ... Input means, 8 ... recording means, 9 ... distance detection means, 10 ... arithmetic control means, 11-14 ... positioning means, 15 ... subject, 16 ... transmitter, 17 ... receiver, 18 ... timekeeping circuit.

Continued on the front page (72) Inventor Eiji Minamiyama 650, Kandate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd.Tsuchiura Plant (56) References JP-A-61-240158 (JP, A) JP-A-63-195566 (JP, A) JP-A-63-134951 (JP, A)

Claims (1)

(57) [Claims] An ultrasonic probe for transmitting an ultrasonic wave to a subject whose surface is not necessarily flat and receiving a reflected wave, a distance detecting means for detecting a distance between the ultrasonic probe and the subject, and a subject Distance detecting means for detecting the distance between the ultrasonic probe, a distance constant control means for keeping the distance between the ultrasonic probe and the subject constant by a signal from the distance detecting means, and an ultrasonic beam transmitted from the ultrasonic probe Normal direction control means for matching the direction of the central axis of the object with the direction of the normal line at each position on the surface of the subject, and flaw detection of the position by reflected waves from each position in the constant distance control and normal direction control states An ultrasonic flaw detection device having a flaw detecting means for detecting flaws or the like present on the surface of the subject when the ultrasonic beam is irregularly reflected and cannot receive a reflected wave, at least two points before and after the position of the flaw or the like. Constant distance system executed in And the distance and the normal direction at the position of such a flaw interpolation calculation by the results in the normal direction control,
An ultrasonic flaw detector comprising means for performing constant distance control and normal direction control at the position of the flaw or the like.