JPH06174703A - Curved surface shape-follow-up type ultrasonic flaw detector and control method for probe attitude - Google Patents

Abstract

(57) [Summary] [Configuration] A function approximating the surface shape is generated from the surface shape data of the object 2 to be inspected obtained immediately before the flaw detection, and when the function is obtained, the surface position of the flaw detection position Then, the probe 1 is moved in advance to detect a flaw. The error between the predicted position and the actual position is corrected by measuring the ultrasonic signal from the surface of the DUT 2 obtained from the probe 1. Probe 1
One of the two axes for correcting the inclination is corrected by the relationship between the angle of the surface of the probe 1 and the surface of the device under test 2 and the intensity of the reflected wave. [Effect] A curved surface on which a flaw can be detected by generating a function approximating the shape of the surface of the object to be inspected and following the object to be inspected whose shape changes three-dimensionally with the information obtained from one probe. A shape-following ultrasonic flaw detector and a probe attitude control method can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detector for detecting defects such as scratches existing on an object to be inspected by using ultrasonic waves while following the surface shape of the object to be inspected. The present invention relates to a curved surface shape following type ultrasonic flaw detection apparatus and a probe attitude control method capable of performing flaw detection following a shape even in flaw detection of a curved surface inspected object whose shape changes.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 64-38648 discloses an example of a conventional apparatus for flaw detection while the probe follows the shape of an object to be inspected. In this example, as shown in FIG. 7, a plurality of displacement sensors 6 and 6 ′ are arranged around the flaw detection probe 1 so as to sandwich the flaw detection probe 1, and outputs from the displacement sensors 6 and 6 ′ are provided. Based on the above, the flaw detection is performed with the flaw detection probe 1 and the inspection object 2 kept at a constant inclination.
The principle is to detect the inclination of the flaw detection probe 1 from the difference between the signals obtained from the two opposed displacement sensors 6 and 6 ', and to detect the distance from the inspection object 2 from the sum of the signals. is there. By performing control using a servo mechanism according to the detected inclination and distance, a certain posture is maintained with respect to the inspection object 2, and ultrasonic flaw detection is realized by following the surface shape.

[0003]

In the conventional method, the distance and angle between the flaw detection probe and the object to be inspected are detected by a displacement sensor which is not involved in the flaw detection itself, and therefore the object to be inspected having a three-dimensional curved surface is detected. In the flaw detection that follows the body, it is necessary to arrange a large number of displacement sensors, and the configuration of the sensor unit cannot be made small. Further, since the displacement sensors are arranged with the flaw detection probe interposed therebetween, there is a limit in reducing the interval between the pair of displacement sensors. Therefore, it is difficult to apply the shape of the curved surface, which changes within a range smaller than the distance between the displacement sensors, because the distance and inclination between the flaw detection probe and the surface of the object to be inspected cannot be detected well.

A first object of the present invention is to provide a non-contact type curved surface shape follow-up type which can follow the surface shape even when the sensor portion is miniaturized and the inspected object has a three-dimensionally changed curved surface. An object is to provide an ultrasonic flaw detector.

A second object of the present invention is to provide a probe attitude control method for miniaturizing the sensor part and for following the surface shape even when the object to be inspected has a three-dimensionally curved surface. It is in.

[0006]

The first object of the present invention is to:
After the flaw detection, when moving the probe to the next flaw detection position, the angle between the probe and the object to be inspected in the scanning direction, or the angle between the probe and the object to be inspected in the direction perpendicular to the scanning direction angle,
And the shape data of the inspected object obtained up to immediately before the position of the inspected object, that is, the vertical position of the probe at each flaw detection point, the inclination in the scanning direction, and the direction perpendicular to the scanning direction. A function for expressing the surface shape of the object to be inspected is generated from the tilt data, and from the function, the probe is tilted in the vertical position and the scanning direction at the next flaw detection position, or in the direction perpendicular to the scanning direction. Is obtained, and when the probe is moved to the next flaw detection position, ultrasonic flaw detection is performed by setting the posture of the probe to the value obtained from the above function.

A second object of the present invention is to detect the error between the predicted posture of the probe and the actually required posture of the probe after the probe is moved to the flaw detection position. The distance between the probe and the surface of the object to be inspected is measured by measuring the propagation time of the reflected wave of the ultrasonic wave from the surface of the object to be inspected. By detecting the position where the intensity of the reflected wave from the surface of the object to be inspected is maximum by changing the inclination of the probe, the ultrasonic reflection intensity and the probe central axis are detected in the other direction. It is corrected by obtaining the inclination based on the angle relationship with the surface of the object to be inspected, and at the time of flaw detection, it is achieved by setting the probe in a posture that allows ultrasonic waves to enter the inside of the object to be inspected at a predetermined angle. It

[0008]

In the present invention, the surface shape of most of the objects to be inspected is minute and the change is gradual, and the surface shape of the object cross section in the scanning direction of the probe is approximated by an appropriate function. Thus, the vertical height and inclination of the surface of the inspection object at the next flaw detection position can be obtained.

Further, according to the present invention, the change in the three-dimensional shape of the object to be inspected is measured by the propagation time and the reflection intensity of the ultrasonic wave reflected from the surface of the object to be inspected, which is obtained from the probe. The child is moved to a predetermined flaw detection position to perform flaw detection. For angle measurement, if the distance between the probe and the object under test is constant,
The property that the intensity of the reflected wave depends on the inclination of the probe is used. That is, the inclination of the probe can be obtained from the difference in intensity from the reference value by previously obtaining the rate of change in the intensity of the reflected wave before flaw detection. When the inspected object changes three-dimensionally, the relationship between the inclination of the inspected object and the intensity of the reflected wave may not be uniquely determined, but the direction controlling the inclination of the probe is detected. When the child's scan direction and two directions perpendicular to the scan direction are set, the tilt in either direction can be detected by detecting the position where the intensity of the reflected wave is maximum. Can apply the relationship between the tilt of the probe and the intensity of the reflected wave.

Therefore, the structure of the flaw detection device required for performing the above-mentioned ultrasonic flaw detection is such that the focus type probe for both transmission and reception and the probe are held, and the horizontal and vertical three directions, the scanning direction, and the scanning direction. A probe holding mechanism capable of moving and tilting in a direction perpendicular to the probe holding mechanism and its drive control device, and an ultrasonic signal obtained from the probe are received and processed, and necessary for the probe holding mechanism control device. There are signal processing devices for transmitting information.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a curved surface shape following flaw detection apparatus according to the present invention. The measurement of the surface position of the inspected object 2 to follow the shape and the flaw detection are performed using the non-contact type focus probe 1, so these measurements are performed in a water tank filled with a medium such as water. To be done. The probe 1 includes a three-axis moving mechanism 33 for moving the focus of the focus type probe to any position on the device under test 2, which is movable in three horizontal and vertical orthogonal directions, and a probe. 1 is held by a probe holding / driving mechanism including a probe tilting mechanism 34 capable of changing the tilt in the scanning direction and the direction perpendicular to the scanning direction without changing the focal position. DUT 2
Is installed in the water tank 7, but circular products such as a water turbine runner and a pump impeller are installed in the water tank 7 or installed on a rotating table that can rotate the water tank itself for flaw detection. To control the probe holding / driving mechanism 3, the drive control device 5 provides the drive control device 5 with information necessary for measuring a shape, processing an ultrasonic signal for flaw detection, and setting the position and orientation of the probe. The signal processing device 4 performs the process of sending to

The flaw detection of the object to be inspected according to the present invention is performed by the processing blocks a to l shown in FIG. After moving to the flaw detection start point, first, an initial flaw detection is performed in which flaw detection is performed while obtaining the number of data required to approximate the cross-sectional shape of the inspection object 2. That is, the height of the surface of the DUT 2 in the vertical direction is obtained from the propagation time of the reflected wave from the surface, and the distance between the focus type probe 1 and the surface of the DUT 2 is Correct so that it is equal to the focal length. Next, the angle of the probe is changed within the cross section in the scanning direction, the angle at which the intensity of the reflected wave is maximized is obtained, and the probe is moved to that angle. The reflection intensity of the ultrasonic wave depends on the inclination of the probe and becomes maximum when the probe is perpendicular to the device under test 2. Therefore, the angle at which the reflection intensity is maximum is the angle of the surface of the inspection object 2 in the cross section in the scanning direction (hereinafter, θ axis). When the distance between the probe 1 and the surface of the object to be inspected 2 and the inclination in the θ-axis cross section are kept constant by the above two operations, the angle between the probe and the surface of the object to be inspected and the reflection intensity are By obtaining the relationship in advance, the inclination of the surface of the inspection object 2 in the direction perpendicular to the scanning direction (hereinafter, φ axis) can be obtained from the measured reflection intensity. After obtaining the number of data required to generate a function approximating the surface shape by initial flaw detection, flaw detection using the shape approximation function is performed. That is, FIG.
Processing blocks c to l in FIG. The shape approximation function is generated in the signal processing device. The position and inclination of the surface of the object to be inspected in the vertical direction (hereinafter referred to as the Z axis) at the next flaw detection position are obtained from the generated function, and the posture of the probe is changed in advance when the probe is moved to the next flaw detection position. By setting, the error between the actual surface position obtained by the shape measurement by ultrasonic waves and the predicted position by the generated function is promptly corrected.
The correction of the error between the position obtained by the actual measurement and the predicted position is performed while measuring the ultrasonic signal in the order of the Z axis, the θ axis, and the φ axis, as in the procedure for the initial flaw detection. After the above correction, the posture of the probe is set so that ultrasonic waves are incident on the probe under the conditions necessary for flaw detection, and the flaw detection is performed. The processing blocks c to l are repeated until all required surface flaw detection is completed.

FIG. 3 shows an example of generating the surface shape approximation function. The example of FIG. 3 is a case where the surface shape of the inspection object 2 is represented by a quadratic equation of the scanning axis (hereinafter, X axis) and Z axis at each flaw detection position in the θ axis cross section. Since three sets of coordinates are required to determine the quadratic equation, the initial flaw detection in this case is repeated three times. The nth flaw detection position from the flaw detection start is set to P _n (X _n , Z
_n ) and the next flaw detection position is P _{n + 1} (X _{n + 1} , Z _{n + 1} ). With P _{n + 1} by the shape approximation function f _x ,

[0015]

## EQU1 ## Z _{n + 1} = f _x (X _{n + 1} ) and the coefficients A, B, and C of f _x are P _i : i = n-2,
It is a function of n-1, n. P stored in the signal processing device
_{By obtaining} the coefficient of f _x from _i (i = n−2, n−1, n), the Z axis value Z _{n + 1} at the next flaw detection position can be obtained. Further, f _x in P _{n + 1} by f _x have been determined
, That is, the inclination θ _{n + 1 of the} surface of the object to be inspected in the θ-axis cross section
But,

[0016]

(2) θ _{n + 1} = tan ⁻¹ (f _x (X _{n + 1} )).

In the present invention, the shape change of the object to be inspected is continuously changed, and it is difficult to apply it as it is to a corner such as an edge where the shape sharply changes as shown in FIG. If the required ultrasonic signal intensity is not obtained even when scanning a certain range in the error correction processing in the processing block of FIG. 2, processing blocks m and n for expanding the scanning range are added to perform the expansion scanning. This can be dealt with by performing the process from the initial flaw detection again after the flaw detection position where the necessary ultrasonic signal is obtained. The processing in this case is shown in FIG.

FIG. 6 is a block diagram showing the flow of ultrasonic signals, control signals and the like in the curved surface shape tracking type ultrasonic flaw detector according to the present invention. The probe holding / driving mechanism 3 is composed of an electric motor 31 for driving each axis, a sensor 32 for detecting a driving amount, and the focus type probe 1, and a signal of the probe 1 is a signal processing device 4. The signal of the sensor is sent to the drive control device 5. In the signal processing device 4, the detection circuit 41 detects the signal from the probe 1 by using the propagation time and the reflection intensity of the reflected wave from the surface,
Also, the propagation time and the reflection intensity of the signal from the defect obtained at the time of flaw detection are detected and sent to the calculator 43 through the A / D converter 42, and the defect data is accumulated in the memory circuit 44, and the inspection object 2
The data of the surface position is processed in the calculator 43, the surface shape approximation function f _x is generated, the moving amount of the probe is calculated, and the data such as the moving amount is sent to the drive control device 5. The drive control device 5 receives the position data of the probe 1 from the sensor 32 in the probe holding / driving mechanism 3 via the interface 51, and the movement amount data of the probe 1 from the signal processing device 4. Is converted into a movement command and is driven by the electric motor 31 via the interface 52.

[0019]

According to the present invention, in order to obtain information on the relative distance and relative angle between the probe and the object to be inspected from the signal from the probe used for flaw detection, the shape of the object to be inspected is grasped. The sensor can be miniaturized without the need to provide a new sensor. Further, in order to approximate the surface shape of the inspection object by the function generated from the measurement data, the information of the inspection object is three-dimensionally obtained only by the information of the relative distance and the relative angle with the inspection object obtained from one probe. It is possible to follow up even when the shape changes, and it is possible to realize a curved surface shape following type ultrasonic flaw detector that follows the shape of the object to be inspected. Further, due to the miniaturization of the sensor unit, there is no gap between the point for flaw detection and the point for measuring the angle between the probe and the object to be inspected,
It is possible to realize a curved surface shape tracking type ultrasonic flaw detection device capable of accurately grasping the shape of the inspection object and performing flaw detection along the surface shape of the inspection object.

[Brief description of drawings]

FIG. 1 is a perspective view of a curved surface shape following type ultrasonic flaw detector according to the present invention.

FIG. 2 is a flowchart of a series of flaw detection processing using the probe attitude control method according to the present invention.

FIG. 3 is an explanatory diagram showing a process for generating a shape approximation function of a surface of an inspection object using a cross-sectional view of the inspection object in the scanning direction.

FIG. 4 is an explanatory diagram showing an ultrasonic signal at an edge portion.

FIG. 5 is a flowchart of flaw detection processing that considers follow-up processing at an edge portion.

FIG. 6 is a block diagram showing a signal flow of the curved surface shape following type ultrasonic flaw detector according to the present invention.

FIG. 7 is an explanatory view of the principle of the flaw detection probe of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Probe, 2 ... Inspected object, 3 ... Probe holding / driving mechanism, 4 ... Signal processing device, 5 ... Drive control device.

Claims (2)

[Claims] 1. A non-contact ultrasonic flaw detector for detecting defects by scanning along a shape of an object to be inspected by using a focus type probe, in a scanning direction or perpendicular to the scanning direction. The angle between the probe and the surface to be inspected in any of the directions, or the position of the surface of the object to be inspected, is predicted using a function represented by the shape data of the object to be inspected obtained immediately before, A curved surface shape following type ultrasonic flaw detector, which has a function of performing flaw detection by moving a probe to a predicted position in advance. 2. The method according to claim 1, wherein the distance between the focus type probe and the surface of the object to be inspected is obtained from the propagation time of the ultrasonic wave from the focus type probe to the surface of the object to be inspected, and the scanning direction, Alternatively, the angle between the focusing probe and the surface to be inspected, which is perpendicular to the scanning direction, is obtained as the angle at which the reception intensity of the reflected ultrasonic wave from the surface of the object to be inspected is maximum. The angle between the focus type probe and the surface of the inspected object in a direction different from the obtained direction is determined by the strength of the reflected wave from the surface of the inspected object which the focus type probe receives. Utilizing the fact that it depends on the angle between the center axis of the child and the normal to the inspection surface of the object to be inspected, it is obtained from the change in the intensity of the reflected wave from the surface of the object to be inspected, and the focus type probe is inspected By controlling the posture of the focus probe to maintain an arbitrary angle and distance to the body surface, Probe attitude control method for performing flaw detection while following of the shape.