JPH06273389A - Ultrasonic crack inspection method - Google Patents

Abstract

PURPOSE:To allow determination of a microcrack along with the type and length thereof by collecting the historical data of the intensity of ultrasonic wave in the axial direction while rotating a work and detecting the duration of intensity data exceeding a predetermined threshold value. CONSTITUTION:Positional relationship between a CCD camera 2 on a screen and an ultrasonic probe 5 is determined before starting the inspection. At the time of inspection, tubular works 4 are arranged in many rows 4a, 4b, on a supply conveyor 1 and transferred below the camera 2 where the images of the works are picked up sequentially starting from the frontmost row 4a thus preparing a histogram. The work 4 is then transferred onto an ultrasonic inspection stage 7 which is rotated by means of a motor 9 to shift the probe 5 in the axial direction of the work 4 thus scanning the work 4 spirally and collecting the historical data of the intensity of ultrasonic wave. Type and length of crack are determined according to the duration of the intensity of ultrasonic wave exceeding a threshold level being set according to the experimental historical data of ultrasonic intensity for failed works.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a crack generated in a cylindrical work by ultrasonic flaw detection.

[0002]

2. Description of the Related Art An apparatus for inspecting defects by moving an ultrasonic probe in the axial direction of a work while rotating a cylindrical work is disclosed in JP-A-61-175563.
-132957 publication. JP-A-61-1
The invention described in Japanese Patent No. 75563 discloses that an ultrasonic probe is attached in the longitudinal direction of the chilled roll while rotating the chilled roll, and a large amount of data is acquired and processed. The invention described in JP-A-1-132957 discloses an inspection in which the ultrasonic contactor is moved by one movement unit for each rotation of the inspection target work. An ultrasonic inspection apparatus equipped with image processing is disclosed in Japanese Patent Application Laid-Open No. 2-57966. In the invention described in this publication, the rotation deviation of one work to be inspected is obtained by an image processing device, and the work is moved so that its axis is aligned with the moving direction of the ultrasonic probe.

[0003]

In the above prior art, when the inspection is performed by moving the ultrasonic probe in the axial direction while rotating the workpiece to be inspected, attention is paid to the relationship between the collected data. Not not. In particular, no attention is paid to the peak value due to noise and the defect state judgment based on the ultrasonic intensity between data.

[0004]

In order to solve the above problems, the present invention adopts the following method. That is, in the method of inspecting the crack of the cylindrical inspection target work by the intensity of the ultrasonic wave, the threshold value of the ultrasonic intensity for discriminating the defect by the type of the crack defect is preset, while rotating the work. After collecting the ultrasonic intensity history data while moving the ultrasonic probe in the axial direction of the work, crack defects from the duration of the ultrasonic intensity data exceeding the preset threshold value for the history data It is a crack inspection method by ultrasonic waves that is used to determine

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the embodiment of the present invention, as the inspection target work, as shown in FIG.
An example in which several cylindrical magnets (ferrite magnets) 4 shown in FIG. 2 are put together at the same time and cracks in individual works are detected will be described.

FIG. 1 shows a block diagram of an apparatus for carrying out the present invention. In FIG. 1, a plurality of magnets 4 to be inspected (hereinafter referred to as works) are arranged on the supply conveyor 1 in a line in the axial direction (4a, 4b, ...). A CCD camera 2 for picking up an image of the frontmost work row 4a is installed above the conveyor 1. An ultrasonic probe moving robot 3 is provided with an ultrasonic probe 5 for performing an inspection. The ultrasonic probe 5 is movable along the slide shaft 6 of the robot 3. A water tank 8 is provided on the inspection stage 7. In the water tank 8, a stage (not shown) for collectively inspecting the works arranged in one row is provided. As this stage, for example, two rotatable rods are arranged in parallel, and a work is placed on the rods. This rod is rotated by the motor 9, and when this rod is rotated, all the works in one row are simultaneously rotated. Reference numeral 10 denotes a defective product dispensing robot that dispenses a defective work after inspection, and has a projecting hand 10a. Reference numeral 11 is a conveyor for delivering non-defective products. At the end of the payout conveyor 11,
Stage 1 for receiving one row of work that has been inspected
2 is provided. Stage 12 is payout conveyor 11
It is possible to rotate in the direction of the upper surface. Further, in the vicinity of the CCD camera 2, an illumination 1 for the work rows 4a, 4b, ...
Install 3.

FIG. 2 shows a system configuration diagram of the apparatus shown in FIG. In the figure, 14 is a device for controlling this device,
For example, a personal computer or a microcomputer.
The personal computer 14 has an image processing unit A, an ultrasonic wave detecting unit B, a crack detecting unit C, a motor controller 15 for controlling the motor 9, an interface 16 for connecting the ultrasonic probe moving robot 3, and a sequencer. An interface 18 for connecting 17 is provided. The CCD camera 2 is connected to the image processing means A. An ultrasonic flaw detector 19 such as the ultrasonic probe 5 is connected to the ultrasonic detecting means B. In addition, the sequencer 17
Although not shown in FIG. 1, the work transfer robot 20 and the defective product delivery robot 10 are connected.

Next, the operation of the present invention will be described.
First, before starting the inspection, the position on the image of the CCD camera 2 and the ultrasonic probe 5 on the ultrasonic probe moving robot 3 are measured.
Find the positional relationship with. The procedure will be described with reference to FIG. One work 4 is placed on the supply conveyor 1, the work 4 is imaged by the CCD camera 2, and the position on the image, for example, the end face position of the work 4 is obtained. Then, the work transfer robot 20 transfers the work 4 to the inspection position of the inspection stage 7. Next, the ultrasonic probe moving robot 3 moves the ultrasonic probe 5 to the position of the end surface of the work 4, reads the coordinate position of the ultrasonic probe moving robot 3 at this time, and reads the coordinate position. Is the position of the ultrasonic probe 5. Then, the converted value of these two positional relationships is obtained to obtain the positional relationship between the image position data and the ultrasonic probe 5. This positional relationship is stored in the crack detecting means C. This operation may be performed only when the apparatus is started up.

Next, the inspection procedure will be described. First, a work supply robot (not shown) arranges the works 4 to be inspected on the supply conveyor 1 in a large number of rows 4a, 4b, ... As shown in FIG. Since the supply conveyor 1 advances in the direction of the arrow L, the CCD camera 2 captures an image of the one row 4a of the work 4 conveyed below the CCD camera 2. The image data captured by the CCD camera 2 is transferred to the image processing means A. As shown in FIG. 4, the image processing means A creates a brightness histogram 21 on the image Y axis within the image processing range H using the image X axis as a parameter. Subsequently, the histogram 21 is differentiated to extract shadows formed on the boundaries of the plurality of works 4 illuminated by the illumination 13, and the positions on the image of the boundaries between the works 4 are obtained. An example of the result of this differential processing is shown in FIG.
In FIG. 5, 22a, 22b, 22c, ... Show boundaries between the works 4. With only the image histogram shown in FIG. 4, uneven brightness causes deviation in brightness value depending on the position of the work 4. However, it is understood that the boundary of the work 4 can be extracted irrespective of the illumination unevenness by performing the differential processing. When determining the boundary of the work 4, the image threshold value Ta is provided on the differential processing data, and the position of the boundary of the work 4 is determined from the position of the pixel that exceeds the threshold value Ta. A procedure for obtaining the boundary position of the work 4 is shown in FIG.

The work 4 having undergone the image processing is moved by the supply conveyor 1 into the movable range of the work transfer robot 20 which handles it on the ultrasonic inspection stage 7. Then, the one-row work 4a is carried to the ultrasonic inspection stage 7 by the work carrying robot 20. Next, the work 4 on the inspection stage 7 is rotated by the motor 9 to move the ultrasonic probe 5 attached to the ultrasonic probe moving robot 3 in the axial direction of the work 4,
While helically inspecting, the ultrasonic intensity history data is stored in the storage device of the ultrasonic detecting means. As a result of various investigations and experiments on the relationship between the cracks generated in the work 4 and the ultrasonic wave intensity, the following facts were revealed. Ultrasonic probe 5
7 shows an example of ultrasonic history data of four workpieces having diagonal cracks, FIG. 8 also shows an example of frontal cracks of the ultrasonic probe 5, and no cracks at all. An example of the case is shown in FIG. In these figures, the point where the ultrasonic intensity diagram is interrupted indicates the boundary between the works 4. In these figures, the ultrasonic history data is 5
It is collected every 0 ms, and the distance between sampling points is about 1.
It is 7 mm. As can be seen from FIGS. 7, 8 and 9, when the ultrasonic wave intensity is weak, but the duration of the historical data of ultrasonic wave intensity exceeding the threshold value is long, the ultrasonic probe 5 is attached to the work 4.
It has been found that there is a long crack oblique to the ultrasonic wave, and the ultrasonic wave intensity is strong, but when the duration is also short, the work 4 has a short crack in front of the ultrasonic probe 5. . Thus, if the threshold of ultrasonic intensity is properly selected based on the experiment of the historical data of ultrasonic intensity of the defective work, the type of crack can be determined from the duration of the intensity of ultrasonic waves exceeding this threshold. The length can be judged.

Subsequently, the crack detecting means C determines whether the work 4 is good or bad from the boundary position data of the work 4 obtained by the image processing means A and the ultrasonic intensity history data. FIG. 10 shows a processing procedure for detecting a front crack on the ultrasonic probe (probe), and FIG. 11 shows a processing procedure for detecting an oblique crack on the ultrasonic probe. This procedure will be described in detail below.

First, the position data on the image of the boundary of the work 4 obtained from the image data is converted into coordinate values of the ultrasonic probe moving robot 3. The ultrasonic probe 5 is provided with two ultrasonic intensity thresholds Tb for judging a front crack and an ultrasonic intensity threshold Tc for judging an oblique crack. Since the boundary position between the works 4 is known by the above procedure, the number of continuous data which exceeds the ultrasonic intensity threshold Tb for each inspection target work 4 from this boundary position and the ultrasonic intensity threshold Tc. The number of cracks and the length of the cracks are judged from each number, and the quality of the workpiece 4 to be inspected is judged. These judgments can also be made by knowledge processing. Further, the ultrasonic intensity data near the boundary of the work 4 is masked as a dead zone to remove the influence of this boundary. The work 4 that has been inspected at the inspection stage 7 is moved to the stage 12 of the payout conveyor 11 by the work transfer robot 20. Then, the crack detecting means C of the personal computer 14 stores which one of the works 4 in the row which has been inspected is defective, and therefore transfers this information to the defective product dispensing robot 10. Then, the robot 10 extends the protruding hand 10a to remove the defective work. Then, the stage 12 is rotated by a predetermined angle to transfer the non-defective work to the payout conveyor 11. The non-defective work 4 on the payout conveyor 11 is conveyed to the next step.

As described above, in the present invention, since the means for detecting the crack length is adopted rather than simply judging the good or bad of the workpiece 4 to be inspected only from the peak of the ultrasonic intensity, it does not become a defective product. It is possible to judge such a minute crack, and it is possible to detect a finer crack as compared with the conventional device.

[0014]

The present invention has the following effects. 1) Conventionally, the quality of the work to be inspected was judged only from the simple peak value of the ultrasonic intensity, but in the present invention, the ultrasonic intensity history data is analyzed and judged in detail to determine the It is not necessary to overlook an oblique crack with respect to the acoustic probe or to judge a crack that has a high peak value of a frontal crack but is not defective as defective, and thus it is possible to further improve the inspection accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an apparatus for carrying out the present invention.

FIG. 2 is a system configuration diagram of the device shown in FIG.

FIG. 3 is a diagram for explaining a method of obtaining a positional relationship between works by an image processing unit and an ultrasonic wave detecting unit.

FIG. 4 is a diagram showing an example of image histogram data.

FIG. 5 is a diagram showing a result of differentiating the histogram data of FIG.

FIG. 6 is a flowchart showing a procedure for extracting a work boundary surface according to the present invention.

7 is a diagram showing an example of history data of ultrasonic intensity collected by the apparatus shown in FIG.

8 is a diagram showing an example of history data of ultrasonic intensity collected by the device shown in FIG.

9 is a diagram showing an example of history data of ultrasonic intensity collected by the apparatus shown in FIG.

FIG. 10 is a flowchart showing a procedure for judging a crack on the front surface of a work with respect to the ultrasonic probe adopted in the present invention.

FIG. 11 is a flowchart showing a procedure for judging a crack in an oblique direction of a work with respect to the ultrasonic probe adopted in the present invention.

FIG. 12 is a diagram showing an example of the shape of the inspection target work applicable to the present invention.

[Explanation of symbols]

 1 Supply Conveyor 2 CCD Camera 3 Robot for Moving Ultrasonic Probe 4 Workpiece 5 Ultrasonic Probe 14 Personal Computer A Image Processing Means B Ultrasonic Detecting Means C Crack Detecting Means

Claims (1)

[Claims] 1. A method for inspecting a crack in a cylindrical workpiece to be inspected by the intensity of ultrasonic waves, wherein a threshold value of ultrasonic intensity for discriminating defects for each type of crack defects is preset and the workpiece is After collecting the ultrasonic intensity history data while moving the ultrasonic probe in the axial direction of the work while rotating, the duration of the ultrasonic intensity data exceeding the preset threshold value for the history data. A crack inspection method using ultrasonic waves, which is characterized by further identifying a crack defect.