JPH03291509A - Shape measuring method for ultrasonic flaw detection - Google Patents

Abstract

PURPOSE:To enable highly accurate shape measurement by coating a body to be measured with fine white particles at the time of the shape measurement. CONSTITUTION:The body 1 to be measured with coated with fine white particles and installed in a water tank in a room which contains no water and a laser range finder 6 is put in scanning operation in an (x) and a (y) direction to measure the distance between the surface of the body 1 to be measured and the range finder 6 at respective points (x,y) on the (x) and (y) axes, thereby obtaining the shape function of the body 1 to be measured. Measured shape data are inputted to a computer 9. Then water is poured in the water tank for the ultrasonic flaw detection in the water. At this time, the fine white particles applied to the body 1 to be measured are removed naturally. Thus, an ultrasonic probe 5 is controlled according to the shape data stored in the computer 9 to maintain a constant distance from the surface of the body 1 to be measured 1 at a constant angle so that the surface of the body 1 to be measured is profiled, thus performing the ultrasonic flaw detection. Consequently, highly accurate shape measurement is performed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for automatically performing underwater ultrasonic flaw detection on curved objects made of various materials such as metal ceramics and composite materials. be.

[Conventional technology]

A method for automatically performing underwater ultrasonic flaw detection on objects with arbitrary curved shapes using a 3D scanner is to input and store the shape data of the object in advance, or to measure it using a distance sensor. Based on the stored shape data, the ultrasonic wave emitted from the ultrasonic probe is incident at a certain angle and from a certain distance with respect to the ultrasonic incident point on the surface of the object to be measured. A method has been adopted to automatically drive and control the position and direction of the ultrasonic probe.

(JP-A-63-309852, JP-A-63-3098
In order to perform ultrasonic flaw detection with high precision, it is necessary to drive and control the ultrasonic probe so that it follows the surface of the object to be measured as accurately as possible. The trajectory of the ultrasonic probe is determined based on shape data obtained through shape measurement, so shape measurement should also be performed at the highest possible speed, especially when measuring and storing shape data of the object to be measured. Must be done with precision. For this reason, a laser distance meter is used for shape measurement, which can perform highly accurate distance measurement in a non-contact manner. A laser distance meter measures the distance to an object by using the principle of triangulation, using scattered light from a laser beam that is directed at the object.

The actual flaw detection procedure is to first place the object to be measured in an empty tank with no water in it, scan the laser distance meter in a fixed position above the object, and scan each point on the X and Y axes. The distance between the laser rangefinder and the surface of the object to be measured at (x, y) is measured in a non-contact manner, and the shape function of the object to be measured z=f
Find (XF y). Next, after water is injected into the water tank, the ultrasonic waves emitted from the ultrasonic probe underwater are incident at a certain angle and from a certain distance with respect to the ultrasonic incident point on the surface of the object to be measured. Ultrasonic flaw detection is performed by automatically controlling the position and direction of the ultrasonic probe based on the measured shape function.

[Problem to be solved by the invention]

However, the laser distance meter used for shape measurement is
As mentioned above, the distance to the object to be measured is measured using the principle of triangulation using the light that is scattered and returned from the laser beam irradiated to the object to be measured. Distance measurement accuracy varies depending on reflectance and color. In particular, it is known that objects with metal or mirror surfaces do not scatter laser light, making measurements hazy, and objects with dark colors that absorb light also reduce measurement accuracy because there is little scattered light.

In addition, in order to measure distance with high accuracy, it is desirable that the surface of the object to be measured be perpendicular to the laser beam emitted by the laser distance meter, and the greater the inclination of the laser beam with respect to the vertical plane, the lower the measurement accuracy. do.

Further, if the surface of the object to be measured is tilted to a certain degree or more with respect to the plane perpendicular to the laser beam, distance measurement becomes impossible. Therefore, when the object to be measured has a curved surface and the shape is to be measured by scanning the object from above while keeping the laser rangefinder in a fixed position, the object to be measured has a curved surface. The surface may become sloped, making measurement difficult. In this case, the degree of accuracy loss and the angle at which measurement becomes impossible are greatly affected by the reflectance and color of the object to be measured.Metal surfaces, mirror surfaces, and dark objects will cause a significant loss of accuracy, and even a slight inclination will cause distance measurement. measurement becomes impossible.

This invention was made to solve this problem, and makes it possible to perform shape measurement with high precision for ultrasonic flaw detection of objects with curved surfaces, regardless of the reflectance or color of the object to be measured. That is the issue.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention measures the shape of the object in advance using a laser distance meter installed in a three-dimensional scanner, and based on the memorized shape data, emits light from an ultrasonic probe. automatically driving and controlling the position and direction of the ultrasonic probe so that the ultrasonic waves incident on the surface of the object to be measured are incident at a certain angle and from a certain distance with respect to the ultrasonic wave incident point on the surface of the object to be measured; In the ultrasonic flaw detection method, highly accurate shape measurement is performed by applying white fine powder to the object to be measured during shape measurement.

[Effect]

By applying white powder to the object to be measured during shape measurement, the laser beam from the laser distance meter is efficiently scattered on the surface of the object, improving the accuracy of distance measurement at each point measured. Furthermore, even when the surface of the object to be measured is somewhat inclined with respect to the vertical plane of the laser beam, highly accurate distance measurement is possible.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings. The ultrasonic flaw detection device shown here is for automatically performing ultrasonic flaw detection underwater on curved objects made of various materials, and uses a laser distance meter installed on a three-dimensional scanner. The shape of the object to be measured is measured in advance, and based on the stored shape data, the ultrasonic waves emitted from the ultrasonic probe are set at a constant angle with respect to the ultrasonic incident point on the surface of the object to be measured. And so that it is incident from a certain distance,
This is a type of device that performs flaw detection by automatically controlling the position and direction of an ultrasonic probe.

Fig. 1 is a schematic diagram of the tip of a three-dimensional scanner in an ultrasonic flaw detection device, in which 1 is the object to be measured and 2 is x
, y, and z scanners, 3 is a θ-axis motor, 4 is an α-axis motor, 5 is an ultrasonic probe, 6 is a laser distance meter, and 7 is a water tank for automatic underwater flaw detection.

As shown in the figure, a laser distance meter 6 is attached to the tip 2 of the scanner, which has X, Y, and Z axes.

Movement of each axis controls its position. Moreover, the ultrasonic probe 5 has two axes, an X axis and a Y axis.

It is attached to the tip of the scanner, which consists of a θ-axis and an α-axis, and its position and orientation are controlled by the movement of each axis. Note that the X-axis, y-axis, and Z-axis are orthogonal to each other, the θ-axis is attached to the Z-axis and rotates around two axes, and the α-axis is attached to the θ-axis.
It is attached to the shaft and rotates in a direction perpendicular to θ.

FIG. 2 is a schematic diagram of the overall structure of the device. With reference to FIG. 2, a process in which a curved object is automatically ultrasonically detected by this ultrasonic flaw detection apparatus will be explained.

First, the shape of the object to be measured 1 placed in the water tank 7 is obtained by importing distance data to the object to be measured 1 into the computer 9, which is measured while scanning the laser distance meter 6 in the XvY direction. Based on the shape data of the object to be measured l imported into the computer 9, the ultrasonic waves emitted from the ultrasonic probe 5 are set at a constant angle and at a constant angle with respect to the ultrasonic incident point on the surface of the object to be measured 1. The computer 9 determines the position and direction in which the ultrasonic probe 5 should move so that the ultrasonic probe 5 is incident from a distance of .

Then, the movements of the XyYtZp θ and α axes are calculated to realize such movement of the ultrasound probe 5, and the computer 9
A command is sent to the control device EII of each axis motor. While the ultrasonic probe 5 is moving to follow the surface of the object to be measured 1, the ultrasonic flaw detection results are taken into the computer 9 via the ultrasonic flaw detector 8 and displayed on the CRT10. As described above, the object to be measured 1 having a curved surface is automatically subjected to ultrasonic flaw detection.

FIG. 3 shows a diagram of the principle of the laser distance meter used in this example. In the figure, the light emitted from the laser 12 is scattered by the surface of the object to be measured and enters the optical position detection element 13, but when the surface of the object to be measured is displaced, the spot on the optical position detection element 13 moves. By converting this amount of movement into an electrical signal and knowing it, the distance to the surface of the object to be measured can be obtained from the principle of triangulation.

In this way, the laser rangefinder uses the light that is scattered and returned from the laser beam that hits the object to be measured, so the surface of the object to be measured is perpendicular to the laser beam emitted by the laser distance meter. It is desirable that the laser beam be tilted to the vertical plane, the measurement accuracy will be lowered as the inclination of the laser beam with respect to the vertical plane is greater, and if the inclination exceeds a certain level, it will be impossible to measure the distance. This tendency is particularly remarkable when the object to be measured is an object with little scattered light, that is, an object with a metal surface or a dark surface.

The state and effect of shape measurement according to the present invention will be explained by taking as an example the case where a dark sample with a curved surface as shown in FIG. 4 is detected.

First, white fine powder is applied directly to the object 1 to be measured, or after it is dissolved in water or the like, it is sprayed or brushed.

Apply by dipping, etc. The white fine powder used here is one that can be easily removed later with water, etc.The object to be measured 1 is placed in an empty water tank 7 without water, and a laser distance meter is placed above it. 6 in the XpY direction, and measure the distance between the surface of the object to be measured 1 and the laser distance meter at each point (xt y) on the X and y axes.
Obtain the shape function z = f (XI y). The shape data measured here is taken into the computer 9. Of the shape data, data for one line scanned in the y direction is shown in FIG.

After this, water is poured into the water tank 7 in order to perform underwater ultrasonic flaw detection. At this time, the white fine powder applied to the object to be measured 1 is naturally removed by water.

Based on the shape data stored in the computer 9 in this way, the ultrasonic probe 5 follows the surface of the object to be measured 1 from a direction at a constant angle to the surface, as described above. It is controlled to maintain a certain distance, and ultrasonic flaw detection is realized.

For comparison, FIG. 6 shows data for one line obtained by scanning the shape data in the y direction when the white fine powder was not applied during shape measurement. The depressed area at the bottom of the figure indicates that the laser rangefinder could not measure the distance.

Comparing Figures 5 and 6, it can be seen that without applying white fine powder,
If the measurement is made on the black surface, it is a horizontal surface.

In other words, approximately 1
It can be seen that measurements are not possible in areas tilted by 8° or more. On the other hand, when white fine powder was applied, the shape of the entire line in the y direction was accurately measured.

〔Effect of the invention〕

As explained above, according to the present invention, the shape of a curved object to be measured is measured in advance using a laser distance meter installed in a three-dimensional scanner, and an ultrasonic probe is used based on the stored shape data. The position and direction of the ultrasonic probe is automatically adjusted so that the ultrasonic wave emitted from the probe is incident at a constant angle and from a constant distance to the ultrasonic incident point on the surface of the object to be measured. In the ultrasonic flaw detection method that controls the drive, applying fine white powder to the object to be measured during shape measurement prevents the surface of the object from being tilted, especially when it comes to metal surfaces or black objects. High-precision shape measurement is possible even when there is a large number of defects, and high-precision ultrasonic flaw detection can be performed using the shape data obtained from the shape measurement.

In addition, as for the fine white powder applied to the object to be measured, by using one that is easily removed by water, etc., there is no need for a special process to remove the fine powder, and it can be injected into a water tank during ultrasonic flaw detection. Since it is naturally removed by water, it does not leave any effect on the object to be measured after a series of flaw detection operations.

[Brief explanation of drawings]

Fig. 1 is a perspective view schematically showing the tip of a three-dimensional scanner in an ultrasonic flaw detection device, Fig. 2 is a block diagram showing a schematic configuration of the entire device, and Fig. 3 shows the principle of the laser distance meter used in the example. Fig. 4 is a perspective view showing an example of a sample of an object to be measured with a curved, dark surface, and Fig. 5 shows a sample after applying white fine powder to the sample shown in Fig. 4 using a laser rangefinder. Graph showing the results of shape measurement, No. 6
This figure is a graph showing the results of shape measurement of the sample shown in FIG. 4 using a laser distance meter without applying white fine powder. 1: Measured object 2: Tip of Xp'jp" scanner 3: θ-axis motor 4: α-axis motor 5 Near: 9: 11: 13: Ultrasonic probe water tank calculator Control device for each axis motor Optical position detection Element 6: Laser distance meter 8: Ultrasonic flaw detector 10: CRT 12: Laser

Claims (1)

[Claims] The shape of the object to be measured is measured in advance using a laser distance meter installed in a three-dimensional scanner, and based on the memorized shape data, the ultrasonic waves emitted from the ultrasonic probe detect the surface of the object to be measured. In an ultrasonic flaw detection method that automatically controls the position and direction of an ultrasonic probe so that the ultrasonic waves are incident at a certain angle and from a certain distance with respect to the point of incidence,
A shape measurement method for ultrasonic flaw detection characterized by performing highly accurate shape measurement by applying fine white powder to the object to be measured during shape measurement.