Magnetic powder flaw detection device and magnetic powder flaw detection method

Abstract

This magnetic powder flaw detection device uses a magnetic powder to detect a flaw on the surface of a flaw detection target material, said device including: a magnetization unit for magnetizing the flaw detection target material; a magnetic powder adhesion unit for adhering the magnetic powder to the surface of the flaw detection target material which has been magnetized by the magnetization unit; an ultraviolet ray radiation unit for radiating ultraviolet rays onto the surface of the flaw detection target material to which the magnetic powder has been adhered by the magnetic powder adhesion unit; an image-capturing unit for generating a plurality of captured images by, at a plurality of different exposure periods or at a plurality of different ultraviolet ray outputs, capturing images of a region considered to be the same as the position, on the surface of the flaw detection target material, that is radiated with ultraviolet rays by the ultraviolet ray radiation unit; a selection unit for selecting a captured image from among the plurality of captured images on the basis of a preset condition; and an inspection unit for inspecting the surface of the flaw detection target material on the basis of the captured image selected by the selection unit.

Description

Magnetic Particle Inspection Device and Magnetic Particle Inspection Method

[0001] The technology of the present disclosure relates to a magnetic particle inspection device and a magnetic particle inspection method, and more particularly to a magnetic particle inspection device and a magnetic particle inspection method for inspecting the surface of a workpiece to be inspected using magnetic particles.

[0002] In magnetic particle inspection, the workpiece to be inspected is magnetized, and a magnetic particle liquid is applied to the surface of the magnetized workpiece. In the magnetized workpiece, magnetic flux leaks from a surface-opening defect or a non-opening defect directly below the surface, and the magnetic particles in the applied magnetic particle liquid adhere to the defect. Therefore, when ultraviolet light is irradiated onto the surface of the workpiece to which the magnetic particle liquid has been applied, the adhered magnetic particles are excited to emit light, and the light-emitting part appears as a defect pattern. Magnetic particle inspection for inspecting the surface of a workpiece using magnetic particles is performed, for example, by an inspector visually observing such a defect pattern in a dark room. The defects that can be confirmed by magnetic particle inspection vary widely in shape and pattern, and may closely resemble harmless pseudo-patterns caused by, for example, accumulations of magnetic particle liquid.

[0003] The inspector needs to determine whether it is harmful or harmless while distinguishing between the defect pattern and the pseudo-pattern. However, this determination is very difficult and largely depends on the skill of the inspector. In addition, magnetic particle inspection is a long-term operation in a dark room, which also makes the inspection work difficult. Furthermore, the inspection work becomes difficult even when the shape of the workpiece to be inspected is complex. Therefore, in magnetic particle inspection by an inspector, the workpiece to be inspected may flow out with surface defects overlooked, resulting in serious claims. Therefore, automation of magnetic particle inspection work is required.

[0004] Magnetic particle inspection is performed by projecting uniform ultraviolet light onto the surface of the workpiece to which the magnetic particle liquid has been applied and visually observing or imaging with a camera the pattern generated by the excited light emission from the magnetic particles adhering to the defects. For example, in Japanese Patent Application Laid-Open No. 2021-025867, a magnetic particle inspection device is proposed that images the surface of the workpiece to which magnetic particles have adhered and adjusts the supply of a cleaning liquid for washing away excess magnetic particles among the magnetic particles adhering to the surface of the workpiece or adjusts the magnetization of the workpiece so that the luminance of the captured image falls within a predetermined range.

[0005] However, in magnetic particle testing, variations in the concentration of magnetic particles dissolved in the magnetic particle solution are unavoidable, which can result in unevenness in the magnetic particles adhering to the surface of the material being tested. Furthermore, variations in the surface properties of the material being tested can also cause unevenness in the magnetic particles adhering to its surface. When unevenness occurs in the magnetic particles adhering to the surface of the material being tested, the intensity of light emitted from the material changes in each region of the surface, causing a change in the average brightness of the captured image. For example, if the average brightness of the captured image is too low, even defects that should be detected will appear dark, potentially leading to them being missed. On the other hand, if the average brightness of the captured image is too high, many false patterns caused by magnetic particles other than defects will appear in the captured image, potentially leading to the false patterns being mistakenly detected as defects. Therefore, it is desirable to be able to accurately detect defects even when there is unevenness in the magnetic particles adhering to the surface of the material being tested.

[0006] The present invention aims to provide a magnetic particle testing apparatus and method that can accurately detect defects even when there are irregularities in the magnetic particles adhering to the surface of the material to be tested.

[0007] A magnetic particle inspection apparatus according to a first aspect of the technology of the present disclosure is a magnetic particle inspection apparatus for inspecting the surface of a material to be inspected using magnetic particles, comprising: a magnetization unit for magnetizing the material to be inspected; a magnetic particle attachment unit for attaching the magnetic particles to the surface of the material to be inspected that has been magnetized by the magnetization unit; an ultraviolet irradiation unit for irradiating the surface of the material to be inspected to which the magnetic particles have been attached by the magnetic particle attachment unit with ultraviolet light; an imaging unit for generating a plurality of imaged images by imaging regions on the surface of the material to be inspected that can be considered to be at the same position, irradiated by the ultraviolet irradiation unit, with a plurality of different exposure times or with a plurality of different ultraviolet light outputs; a selection unit for selecting an imaged image from the plurality of imaged images based on preset conditions; and an inspection unit for inspecting the surface of the material to be inspected based on the imaged image selected by the selection unit.

[0008] A magnetic particle inspection apparatus according to a second aspect of the technology of the present disclosure is a magnetic particle inspection apparatus according to a first aspect, wherein the preset conditions include a first condition that the number of luminance-saturated pixels in the captured image is less than or equal to a preset threshold for the number of pixels, a second condition that the average luminance in the captured image is within a preset threshold range for luminance, and a third condition that the standard deviation of luminance in the captured image is within a preset threshold range for standard deviation.

[0009] A magnetic particle testing method according to a third aspect of the technology of the present disclosure is a magnetic particle testing method for testing the surface of a material to be tested using magnetic particles, and uses a magnetic particle testing apparatus comprising: a magnetization unit for magnetizing the material to be tested; a magnetic particle attachment unit for attaching the magnetic particles to the surface of the material to be tested that has been magnetized by the magnetization unit; an ultraviolet irradiation unit for irradiating the surface of the material to be tested to which the magnetic particles have been attached by the magnetic particle attachment unit with ultraviolet light; an imaging unit for generating a plurality of imaged images by imaging regions on the surface of the material to be tested that can be considered to be at the same position as the ultraviolet light irradiated by the ultraviolet irradiation unit, at multiple different exposure times or at multiple different ultraviolet light outputs; a selection unit for selecting an imaged image from the plurality of imaged images based on preset conditions; and an inspection unit for inspecting the surface of the material to be tested based on the imaged image selected by the selection unit, wherein the magnetic particle testing apparatus uses the magnetization unit to test the surface of the material to be tested. The apparatus comprises: a magnetization step of magnetizing the material to be inspected; a magnetic powder attachment step of attaching the magnetic powder to the surface of the material to be inspected that has been magnetized by the magnetization step using the magnetic powder attachment unit; an ultraviolet irradiation step of irradiating the surface of the material to be inspected that has been coated with magnetic powder by the magnetic powder attachment unit with ultraviolet light using the ultraviolet irradiation unit; an imaging step of generating multiple images by using the imaging unit to image regions on the surface of the material to be inspected that can be considered to be in the same position, with multiple different exposure times or with multiple different ultraviolet light outputs; a selection step of using the selection unit to select an image from the multiple images based on preset conditions; and an inspection step of using the inspection unit to inspect the surface of the material to be inspected based on the image selected by the selection unit.

[0010] The present invention provides a magnetic particle testing apparatus and a magnetic particle testing method that can accurately detect defects even when there are irregularities in the magnetic particles adhering to the surface of the material to be tested.

[0011] This is a perspective view showing an example of the schematic configuration of a magnetic particle testing apparatus and a material to be inspected according to one embodiment of the technology disclosed herein. This is a block diagram showing an example of the functional configuration of the processing apparatus. This is a diagram showing an example of multiple captured images obtained for regions that can be considered identical. This is a graph showing an example of a first condition for selecting an captured image. This is a graph showing an example of a second condition for selecting an captured image. This is a graph showing an example of a third condition for selecting an captured image. This is a diagram showing an example of multiple captured images obtained for different regions and one captured image selected for each region. This is a block diagram showing an example of the hardware configuration of the processing apparatus. This is a flowchart showing an example of the flow of a magnetic particle testing method.

[0012] Hereinafter, one embodiment of the technology of this disclosure will be described with reference to the drawings.

[0013] (Description of the overall configuration of the magnetic particle testing apparatus 10) Figure 1 shows an example of the schematic configuration of a magnetic particle testing apparatus 10 and a material to be inspected 70 that is the subject of magnetic particle testing according to one embodiment of the technology of this disclosure. The material to be inspected 70 is a ferromagnetic object. In the following description, as shown in Figure 1, the shape of the material to be inspected 70 is cylindrical, and the case in which magnetic particle testing is performed on the outer surface of the material to be inspected 70 while rotating the material to be inspected 70 around its central axis 70A is given as an example, but the shape of the material to be inspected 70 can be anything, and it does not have to be rotated. Also, magnetic particle testing may be performed on surfaces other than the outer surface of the material to be inspected 70. Magnetic particle testing detects a defect 72 that has occurred on the outer surface of the material to be inspected 70. The defect 72 is, for example, an open crack and is formed along the central axis 70A of the material to be inspected 70. The outer surface of the material to be inspected 70 is an example of the "surface of the material to be inspected" in the technology of this disclosure.

[0014] The central axis 70A of the material to be inspected 70 refers to the axis that passes through the center of the circular cross-section of the material to be inspected 70 and is perpendicular to the cross-section. The outer surface of the material to be inspected 70 refers to the surface that exists in the circumferential direction of the cylindrical material to be inspected 70. The circumferential direction of the material to be inspected 70 refers to the direction around the central axis 70A, centered on the central axis 70A.

[0015] The magnetic particle testing apparatus 10 is a device that uses magnetic particles to inspect the outer surface of a material to be inspected 70. The magnetic particle testing apparatus 10 includes a magnetization device 12, a magnetic particle adhesion device 14, a rotating device 16, an ultraviolet irradiation device 18, an imaging device 20, a marking device 22, and a processing device 24.

[0016] The magnetization device 12 is a device that magnetizes the material to be inspected 70, which is a ferromagnetic material. That is, at the start of magnetic particle inspection, the magnetization device 12 magnetizes the material to be inspected 70 under the control of the control unit 60, which will be described later. The magnetization device 12 is an example of a "magnetization unit" in the technology of this disclosure. The magnetization device 12 has a permanent magnet or electromagnet for magnetizing the material to be inspected 70. The magnetization device 12 also has an actuator for moving the permanent magnet or electromagnet. The actuator has a motor or a robot arm, etc.

[0017] The magnetic powder adhesion device 14 is a device that applies a magnetic powder solution, in which magnetic powder is dissolved, to the outer surface of the material to be inspected 70, which has been magnetized by the magnetization device 12, thereby adhering magnetic powder to the outer surface of the material to be inspected 70. That is, at the start of the magnetic powder inspection, the magnetic powder adhesion device 14 applies the magnetic powder solution to the magnetized material to be inspected 70 under the control of the control unit 60, which will be described later, thereby adhering magnetic powder to the outer surface of the material to be inspected 70. The magnetic powder adhesion device 14 is an example of a "magnetic powder adhesion unit" in the technology of this disclosure. The magnetic powder adhesion device 14 has a nozzle or brush, etc., for applying the magnetic powder solution. The magnetic powder adhesion device 14 also has an actuator, etc., for moving the nozzle or brush, etc. The actuator has a motor or a robot arm, etc.

[0018] The rotating device 16 is a mechanism that rotates the material to be inspected 70 around its central axis 70A. More specifically, the rotating device 16 is a mechanism that rotates the material to be inspected 70 around a central axis 70A that is parallel to the direction perpendicular to the optical axis of the imaging device 20, which will be described later, so that the outer surface of the material to be inspected 70 is shown to the optical axis of the imaging device 20, which will be described later. The rotating device 16 has a reduction gear and a motor, etc., so that the material to be inspected 70 can be rotated at a desired speed. That is, under the control of the control unit 60, which will be described later, the rotating device 16 is activated at the start of the magnetic particle inspection to start the rotation of the material to be inspected 70. In this embodiment, the rotating device 16 rotates the material to be inspected 70 with the axis of the cylindrical material to be inspected 70 perpendicular to the optical axis of the imaging device 20 as the central axis 70A. The rotating device 16 is an example of a "rotating part" in the technology of this disclosure.

[0019] The ultraviolet irradiation device 18 irradiates ultraviolet light onto the outer surface of the material to be inspected 70 to which magnetic powder is attached (more precisely, the space including the material to be inspected 70). That is, under the control of the control unit 60, which will be described later, the ultraviolet irradiation device 18 starts irradiating ultraviolet light at the start of the magnetic particle inspection. The ultraviolet irradiation device 18 may be, for example, a ring-shaped ultraviolet irradiation device 18 that emits ultraviolet light. The ultraviolet irradiation device 18 is also arranged coaxially with the imaging device 20, which will be described later, and is configured to irradiate ultraviolet light into the area including the imaging range 20A of the imaging device 20 (i.e., the irradiation range). The ultraviolet irradiation device 18 may also be configured such that ultraviolet light from the ultraviolet irradiation device 18 is uniformly irradiated into the irradiation range by providing a diffusion film on the front surface of the ultraviolet irradiation device 18. The ultraviolet light remains irradiated until the magnetic particle inspection is completed. The ultraviolet irradiation device 18 is an example of the "ultraviolet irradiation unit" in the technology of this disclosure.

[0020] The imaging device 20 generates multiple imaged images 30 for each region that can be considered identical when imaging multiple regions along the circumferential direction of the outer surface of the material to be inspected 70 to which magnetic powder excited and emitted by ultraviolet light is attached. The imaging device 20 is a camera capable of imaging the outer surface of the material to be inspected 70 (i.e., the surface around the central axis 70A) as a monochrome or color imaged image 30. The imaging device 20 may be, for example, a two-dimensional camera in which image sensors such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) are arranged in two dimensions.

[0021] The imaging device 20 is positioned such that its optical axis is included in the plane containing the central axis 70A of the material to be inspected 70. The imaging device 20 images the area including at least the outer periphery of the material to be inspected 70, which is visible from the imaging device 20, as the imaging range 20A. Furthermore, as described above, the imaging device 20 is positioned such that its optical axis is coaxial with the ultraviolet irradiation device 18. By making the imaging device 20 and the ultraviolet irradiation device 18 coaxial, the imaging sensitivity can be made as close to maximum as possible. The captured image 30 will include the outer periphery of the material to be inspected 70 contained within the imaging range 20A, as well as magnetic powder adhering to the outer periphery of the material to be inspected 70 and excited and emitted by ultraviolet light irradiated from the ultraviolet irradiation device 18.

[0022] The marking device 22 is a device that marks the outer surface of the material to be inspected 70. The marking device 22 may be, for example, a robotic arm with a drawing tool at its tip. In this case, the marking device 22 draws a specified symbol, character, mark, etc., at a specified location on the outer surface of the material to be inspected 70, for example, at a location where a problematic defect 72 is detected. This makes it easy to identify locations on the outer surface of the material to be inspected 70 that are of quality concern.

[0023] (Description of the functional configuration of the processing unit 24) The processing unit 24 is a device that performs various controls related to the magnetic particle testing device 10 and various calculations related to the inspection of the material to be inspected 70, and is composed of a computer with a hardware configuration described later. Figure 2 shows an example of the functional configuration of the processing unit 24. The processing unit 24 includes a control unit 60, a selection unit 62, and an inspection unit 64 as its functional configuration.

[0024] The control unit 60 is a functional unit that controls the various devices included in the magnetic particle inspection apparatus 10 to enable them to perform their functions. Specifically, the control unit 60 controls the magnetization device 12, the magnetic particle adhesion device 14, the rotating device 16, the ultraviolet irradiation device 18, the imaging device 20, and the marking device 22. The control unit 60 synchronizes the timing of various controls by obtaining the rotation angle and rotation period of the material to be inspected 70 from a rotary encoder or the like provided on the rotating device 16.

[0025] Incidentally, in magnetic particle testing, variations in the concentration of magnetic particles dissolved in the magnetic particle solution are unavoidable, which can result in unevenness in the magnetic particles adhering to the surface of the material to be tested 70. Furthermore, variations in the surface properties of the material to be tested 70 can also cause unevenness in the magnetic particles adhering to its surface. When unevenness occurs in the magnetic particles adhering to the surface of the material to be tested 70 in this way, the intensity of light emitted from the material to be tested 70 changes in each region of its surface, causing the average brightness of the captured image 30 to change. For example, if the average brightness of the captured image 30 is too low, the scratches 72 that should be detected will also appear dark, and there is a risk of missing the scratches 72. On the other hand, for example, if the average brightness of the captured image 30 is too high, many false patterns 74 (see Figure 3) made of magnetic particles other than the scratches 72 will be captured in the image 30, and there is a risk of misdetecting the false patterns 74 as scratches 72. Therefore, it is desirable that the defects 72 can be detected accurately even when there are inconsistencies in the magnetic particles adhering to the surface of the material to be inspected 70. Accordingly, the magnetic particle inspection device 10 of this embodiment operates as follows in order to accurately detect the defects 72.

[0026] First, the imaging device 20 images the entire circumference of the outer surface of the material to be inspected 70 along the circumferential direction and generates an image 30. More specifically, the imaging device 20 images the entire circumference of the outer surface of the material to be inspected 70 while changing its position on the material to be inspected 70 as captured in the image 30. At this time, the imaging device 20 images each position on the material to be inspected 70 as captured in the image 30 with different exposure times within a time frame in which the position can be considered the same, thereby generating multiple images 30. Therefore, the imaging device 20 images the range on the surface of the material to be inspected 70 as being the same position with multiple different exposure times, thereby generating multiple images. Note that since the material to be inspected 70 rotates during imaging, it is not possible to image the exact same area multiple times. However, for each region of the outer surface of the material to be inspected 70, the imaging device 20 images multiple times at high speed to the extent that the areas being imaged can be considered the same region. Therefore, since the target area of ​​the captured image 30, which is captured multiple times at high speed, is almost the same area, in this embodiment, this area is referred to as the area where the surface position of the material to be inspected 70 can be considered to be the same.

[0027] Figure 3 shows an example of multiple captured images 30 obtained for regions that can be considered identical. In the example shown in Figure 3, five captured images 30 are obtained by imaging regions that can be considered identical with five different exposure times. Specifically, the exposure time increases sequentially from the first captured image 30 to the fifth captured image 30.

[0028] Of the five captured images 30, the first captured image 30, which has the shortest exposure time, has a low average brightness, and the scratches 72 that should be detected appear dark. Therefore, if magnetic particle testing is performed using the first captured image 30, there is a risk of missing the scratches 72. On the other hand, the fifth captured image 30, which has the longest exposure time, has a high average brightness, and many false patterns 74 made of magnetic particles other than the scratches 72 are captured. Therefore, if magnetic particle testing is performed using the fifth captured image 30, there is a risk of misdetecting the false patterns 74 as scratches 72. In the example shown in Figure 3, of the five captured images 30, the third captured image 30 captures the scratches 72 that should be detected with sufficient brightness, and there are few false patterns 74. Therefore, if magnetic particle testing is performed using the third captured image 30, the scratches 72 can be detected with high accuracy.

[0029] Next, the operation of the selection unit 62 for accurately detecting defects 72 will be explained. The selection unit 62 selects one image 30 suitable for magnetic particle testing from a plurality of image images 30 obtained for each region, based on preset conditions. The preset conditions are as follows.

[0030] Figure 4 shows a graph illustrating the first condition for selecting the captured image 30. In the graph shown in Figure 4, the horizontal axis represents the exposure time [μsec], and the vertical axis represents the number of luminance-saturated pixels. The number of luminance-saturated pixels is the number of pixels in the captured image 30 whose luminance has saturated. The first condition is set to ensure that the number of luminance-saturated pixels in the captured image 30 is less than or equal to a preset threshold for the number of pixels. Since luminance-saturated pixels appear white and their luminance cannot be appropriately represented numerically, if the number of luminance-saturated pixels in the captured image 30 is 1 or more, there is a risk that the detection accuracy of the scratches 72 will decrease due to the luminance-saturated pixels. Therefore, it is desirable that the number of luminance-saturated pixels in the captured image 30 be 0. Thus, in this embodiment, as an example, the threshold for the number of pixels is set to 0.

[0031] Figure 5 shows a graph illustrating the second condition for selecting the captured image 30. In the graph shown in Figure 5, the horizontal axis represents the exposure time [μsec], and the vertical axis represents the average brightness. The average brightness is the average brightness of multiple pixels included in the captured image 30. The second condition is set to ensure that the average brightness in the captured image 30 falls within a preset brightness threshold range. If the average brightness of the captured image 30 is low, the scratches 72 that should be detected will appear dark, so there is a risk of missing scratches 72 when performing magnetic particle testing using an captured image 30 with low average brightness. On the other hand, if the average brightness of the captured image 30 is high, many false patterns 74 made of magnetic particles other than scratches 72 will be captured, so there is a risk of misdetecting false patterns 74 as scratches 72 when performing magnetic particle testing using an captured image 30 with high average brightness. Therefore, it is desirable that the average brightness in the captured image 30 be above the brightness required to detect scratches 72 without missing them, and below the brightness required to detect scratches 72 without misdetecting false patterns 74 as scratches 72. Therefore, in this embodiment, the selection unit 62 calculates an average value from the average brightness of the captured image 30 that can detect scratches 72 without misidentifying the pseudo-pattern 74 as scratches 72, and from the average brightness of the captured image 30 that can detect scratches 72 without missing any, and sets a preset brightness threshold range from the margin of the average value. Since the surface properties of the outer surface differ for each type and shape of the material to be inspected 70, it is preferable to explore and set the brightness threshold range for each type and shape of the material to be inspected 70.

[0032] Figure 6 shows a graph illustrating the third condition for selecting the captured image 30. In the graph shown in Figure 6, the horizontal axis represents the exposure time [μsec], and the vertical axis represents the luminance standard deviation. The luminance standard deviation is the standard deviation of the luminance of multiple pixels included in the captured image 30. The third condition is set to the condition that the luminance standard deviation in the captured image 30 falls within a preset standard deviation threshold range. Similar to the luminance threshold range in the second condition, the preset standard deviation threshold range is set to be greater than or equal to the standard deviation at which scratches 72 can be detected without missing them, and less than or equal to the standard deviation at which scratches 72 can be detected without falsely detecting pseudo-patterns 74 as scratches 72. In other words, the selection unit 62 sets the preset standard deviation threshold range from the average value of the average luminance of captured images 30 that can detect scratches 72 without falsely detecting pseudo-patterns 74 as scratches 72, and captured images 30 that can detect scratches 72 without missing them. Since the surface properties of the outer surface differ depending on the type and shape of the material to be inspected 70, the threshold range of the standard deviation should be explored and set for each type and shape of the material to be inspected 70. In this embodiment, as an example, the first condition, the second condition, and the third condition are used, but either the second condition or the third condition may be used alone.

[0033] Figure 7 shows an example of multiple captured images 30 obtained for different regions 1 to 5, and one captured image 30 selected for each region. Regions 1 to 5 are different regions along the circumferential direction of the outer surface of the material to be inspected 70. In the example shown in Figure 7, five captured images 30 are obtained for each region by imaging each region with five exposure times. The captured images 30 enclosed by dashed lines are the captured images 30 selected by the selection unit 62. In the example shown in Figure 7, the emission intensity from the material to be inspected 70 changes from region to region due to unevenness in the magnetic powder attached to each region. However, the selection unit 62 selects an captured image 30 that satisfies the above conditions from the multiple captured images 30 obtained by imaging each region with multiple exposure times, thereby extracting an captured image 30 suitable for detecting defects 72 for each region as an inspection image.

[0034] The inspection unit 64 inspects the outer surface of the material to be inspected 70 based on the captured images 30 selected by the selection unit 62 for each region. Specifically, the inspection unit 64 performs predetermined image processing (for example, brightness unevenness correction, filtering, binarization, shape calculation processing, and machine learning processing) on ​​the captured images 30 selected by the selection unit 62. The inspection unit 64 then determines whether or not there is a scratch 72 on the outer surface of the material to be inspected 70 (i.e., whether or not the scratch 72 is visible in the processed captured image 30). If the inspection unit 64 determines that there is a scratch 72 on the outer surface of the material to be inspected 70, it identifies the location of the scratch 72 from the captured image 30 and stores the identified location of the scratch 72 in the storage device 46 (see Figure 8), which will be described later.

[0035] (Description of the hardware configuration of the processing unit 24) Figure 8 shows an example of the hardware configuration of the processing unit 24. The processing unit 24 is composed of a computer. The processing unit 24 has a CPU (Central Processing Unit) 42, memory 44, storage device 46, input device 48, output device 50, storage medium reader 52, and communication I / F (Interface) 54. Each component is connected to the others so as to be able to communicate with each other via a bus 56.

[0036] The storage device 46 stores a program for performing the magnetic particle testing process described later. The CPU 42 is a central processing unit that executes various programs and controls each component. Specifically, the CPU 42 reads a program from the storage device 46 and executes the program using memory 44 as a workspace. The CPU 42 controls each component and performs various calculations according to the program stored in the storage device 46.

[0037] Memory 44 is composed of RAM (Random Access Memory) and temporarily stores programs and data as a working area. Storage device 46 is composed of ROM (Read Only Memory), HDD (Hard Disk Drive), or SSD (Solid State Drive), etc., and stores various programs including the operating system and various data.

[0038] The input device 48 is a device for performing various types of input, such as a keyboard or mouse. The output device 50 is a device for outputting various types of information, such as a display or printer. By using a touch panel display as the output device 50, it may also function as the input device 48.

[0039] The storage medium reader 52 reads data stored on various storage media such as CD (Compact Disc)-ROM, DVD (Digital Versatile Disc)-ROM, Blu-ray disc, or USB (Universal Serial Bus) memory, and writes data to the storage media. The communication I / F 54 is an interface for communicating with other devices, and standards such as Ethernet®, FDDI, or Wi-Fi® are used.

[0040] Furthermore, the processing unit 24 may have electronic circuits such as a PLD (Programmable Logic Device) or ASIC (Application Specific Integrated Circuit) in place of, or in addition to, a processor such as a CPU 42. Some or all of the processor's functions may be implemented by electronic circuits such as a PLD or ASIC.

[0041] (Explanation of Magnetic Particle Testing Method) Figure 9 shows an example of the flow of the magnetic particle testing method. The CPU 42 reads a program for executing the magnetic particle testing process from the storage device 46, loads the program into memory 44, and executes it. As a result, the CPU 42 functions as a functional unit of the processing device 24, and the magnetic particle testing process is executed. This executes the magnetic particle testing method in the magnetic particle testing device 10. In the magnetic particle testing method, first, the material to be tested 70 is brought into the magnetic particle testing device 10.

[0042] Next, in step S10, the control unit 60 operates by controlling the magnetization device 12 and the magnetic powder adhesion device 14. As a result, the magnetization device 12 executes a magnetization step of magnetizing the test piece 70, and the magnetic powder adhesion device 14 executes a magnetic powder adhesion step of applying a magnetic powder liquid to the outer peripheral surface of the test piece 70 magnetized by the magnetization device 12 to adhere magnetic powder.

[0043] Next, in step S12, the control unit 60 turns on the ultraviolet irradiation device 18 by controlling it. As a result, the ultraviolet irradiation device 18 starts an ultraviolet irradiation step of irradiating the outer peripheral surface of the test piece 70 to which magnetic powder has adhered (more precisely, the space including the test piece 70) with ultraviolet rays.

[0044] Next, in step S14, the control unit 60 operates by controlling the rotation device 16. As a result, the rotation device 16 starts a rotation step of rotating the test piece 70 about the central axis 70A of the test piece 70. The rotation step is executed until the end of the imaging step described later.

[0045] Next, in step S16, the control unit 60 controls the imaging device 20 to image the outer peripheral surface of the test piece 70 in accordance with a predetermined cycle of rotation of the test piece 70. As a result, the imaging device 20 starts an imaging step of imaging the outer peripheral surface of the test piece 70 to which magnetic powder has adhered in the space illuminated with ultraviolet rays by the ultraviolet irradiation device 18. In the imaging step, the imaging device 20 generates a plurality of imaging images 30 related to a plurality of regions along the circumferential direction over the entire circumference of the outer peripheral surface of the test piece 70 by imaging the outer peripheral surface of the test piece 70. Also, at this time, the imaging device 20 generates a plurality of imaging images 30 corresponding to a plurality of different exposure times by imaging each region with a plurality of different exposure times. After the end of the imaging step, the magnetic flaw detection method proceeds to step S18.

[0046] Next, in step S18, the selection unit 62 executes a selection step of selecting one imaging image 30 suitable for the magnetic flaw detection inspection from the plurality of imaging images 30 obtained for each region based on preset conditions.

[0047] Next, in step S20, the inspection unit 64 executes an image processing step including predetermined image processing (for example, luminance unevenness correction, filtering, binarization processing, shape calculation processing, and machine learning processing, etc.) on the captured image 30 selected by the selection unit 62.

[0048] Next, in step S22, the inspection unit 64 executes a determination step of determining whether there is a defect 72 on the outer peripheral surface of the inspected material 70 (that is, whether the defect 72 appears in the captured image 30 subjected to image processing). Here, if it is determined by the inspection unit 64 that there is a defect 72 on the outer peripheral surface of the inspected material 70, the magnetic particle inspection method proceeds to step S24. On the other hand, if it is determined by the inspection unit 64 that there is no defect 72 on the outer peripheral surface of the inspected material 70, the inspected material 70 is carried out from the magnetic particle inspection device 10, and the magnetic particle inspection method proceeds to step S28. Steps S20 and S22 are an example of the "inspection step" in the technology of the present disclosure.

[0049] In step S24, the inspection unit 64 executes a storage step of identifying the position of the defect 72 from the captured image 30 and storing the identified position of the defect 72 in a storage device described later.

[0050] Next, in step S26, by the control unit 60 controlling the marking device 22, the marking device 22 executes a marking step of marking at the position of the defect 72. After the execution of the marking step, the inspected material 70 is carried out from the magnetic particle inspection device 10, and the magnetic particle inspection method proceeds to step S28.

[0051] In step S28, the CPU executes an end determination step of determining whether the magnetic particle inspection has been completed for all the inspected materials 70. If the magnetic particle inspection has not been completed for all the inspected materials 70, the magnetic particle inspection method proceeds to step S10, and the magnetic particle inspection is performed on the next inspected material 70. On the other hand, if the magnetic particle inspection has been completed for all the inspected materials 70, the surface inspection method ends. Incidentally, as the magnetic particle inspection for all the inspected materials 70 is completed, the control unit 60 turns off the ultraviolet irradiation device 18 to stop the irradiation of ultraviolet rays.

[0052] (Operation and Effects of Magnetic Particle Testing Apparatus 10) As described above, in this embodiment, the imaging device 20 is used to image multiple images 30 by irradiating the outer surface of the material to be inspected 70 with ultraviolet light using the ultraviolet irradiation device 18, in areas where the positions of these areas can be considered to be the same, at multiple different exposure times. Then, the selection unit 62 is used to select one image 30 suitable for magnetic particle testing from the multiple images 30 based on preset conditions, and the inspection unit 64 is used to inspect the outer surface of the material to be inspected 70 based on the image 30 selected by the selection unit 62. Therefore, even if there is unevenness in the magnetic particles adhering to the outer surface of the material to be inspected 70 and the emission intensity from the material to be inspected 70 changes, the inspection can be performed based on one image 30 suitable for magnetic particle testing, so that defects 72 can be detected with high accuracy.

[0053] Furthermore, the pre-set conditions include a first condition that the number of brightness-saturated pixels in the captured image 30 is less than or equal to a pre-set threshold for the number of pixels. Therefore, it is possible to suppress the inclusion of brightness-saturated pixels in the selected captured image 30, thereby suppressing a decrease in the detection accuracy of the scratches 72 caused by brightness-saturated pixels.

[0054] Furthermore, the pre-set conditions include at least one of two conditions: a second condition that the average brightness in the captured image 30 falls within a pre-set brightness threshold range, and a third condition that the standard deviation of the brightness in the captured image 30 falls within a pre-set standard deviation threshold range. Therefore, it is possible to select an captured image 30 with brightness suitable for detecting scratches 72, thereby suppressing the oversight of scratches 72 or the misdetection of pseudo-patterns 74 as scratches 72.

[0055] (Modified form of magnetic particle testing apparatus 10) In the above embodiment, multiple images 30 are generated by imaging regions on the outer surface of the material to be tested 70, which has been irradiated with ultraviolet light by the ultraviolet irradiation device 18, at multiple different exposure times, where the positions of these regions can be considered to be the same. However, multiple images 30 (hereinafter referred to as "multiple ultraviolet output images") may be generated by changing the output of the ultraviolet irradiation device 18 and imaging at multiple different ultraviolet outputs. Then, one ultraviolet output image suitable for magnetic particle testing may be selected from the multiple ultraviolet output images based on pre-set conditions, and the outer surface of the material to be tested 70 may be inspected based on the selected ultraviolet output image. In this way, as with the multiple images 30, multiple ultraviolet output images with different brightness levels depending on the exposure amount are obtained for each region, so the same effects as in the above embodiment can be obtained.

[0056] Furthermore, in the above embodiment, multiple imaged images 30 are generated for each region by imaging multiple times with different exposure times for regions where the position of the outer surface of the material to be inspected 70 can be considered to be the same during one rotation of the material to be inspected 70. Alternatively, one imaged image 30 may be generated for each region by imaging each region once with the same exposure time during one rotation of the material to be inspected 70, and multiple imaged images 30 may be generated for each region by repeating the imaging with a different exposure time each time the material to be inspected 70 rotates. That is, if five imaged images 30 are to be generated for each region, the material to be inspected 70 may be rotated five times.

[0057] Furthermore, although a ring-shaped imaging device 20 is used in the above embodiment, a line-shaped imaging device 20 may also be used. Alternatively, a pair of line-shaped ultraviolet irradiation devices 18 may be horizontally arranged above and below the imaging device 20. Depending on the size and shape of the material to be inspected 70, multiple ultraviolet irradiation devices 18 may be arranged to illuminate from multiple directions.

[0058] Furthermore, although the ultraviolet irradiation device 18 is positioned to illuminate the surface of the material to be inspected 70 perpendicularly, this is not limited to the shape of the material to be inspected 70 or the shape of the defect 72. Also, the shape of the ultraviolet irradiation device 18 is not limited to a ring shape or a line shape.

[0059] Furthermore, the shape of the material to be inspected 70 is not limited to a cylindrical shape. Depending on the shape of the material to be inspected 70, the image 30 may be acquired without rotating the material to be inspected 70, or the image 30 may be acquired while translating the material to be inspected 70.

[0060] Furthermore, in the above embodiment, a two-dimensional camera with image sensors arranged in two dimensions is used as the imaging device 20, but a one-dimensional camera with image sensors arranged in one dimension may also be used.

[0061] Furthermore, in the above embodiment, the surface of the material to be inspected 70 may be treated based on the marked position. The treatment may be performed by a treatment device or by manual labor.

[0062] The above describes an example of the technology disclosed herein. However, the technology disclosed herein is not limited to the above, and it is of course possible to implement it in various modified forms without departing from its essence.

[0063] The disclosure of Japanese Patent Application No. 2024-174403 is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated as being incorporated by reference.

Claims

1. A magnetic particle flaw detection apparatus for inspecting the surface of a material to be inspected using magnetic powder, comprising: a magnetization unit for magnetizing the material to be inspected; a magnetic powder attachment unit for attaching the magnetic powder to the surface of the material to be inspected that has been magnetized by the magnetization unit; an ultraviolet irradiation unit for irradiating the surface of the material to be inspected to which the magnetic powder has been attached by the magnetic powder attachment unit with ultraviolet light; an imaging unit for generating multiple images by imaging regions on the surface of the material to be inspected that can be considered to be at the same position, irradiated with ultraviolet light by the ultraviolet irradiation unit, at multiple different exposure times or at multiple different ultraviolet light outputs; a selection unit for selecting an image from the multiple images based on preset conditions; and an inspection unit for inspecting the surface of the material to be inspected based on the image selected by the selection unit.

2. The magnetic particle inspection apparatus according to claim 1, wherein the preset conditions include a first condition that the number of luminance-saturated pixels in the captured image is less than or equal to a preset threshold for the number of pixels, a second condition that the average luminance in the captured image falls within a preset threshold range for luminance, and a third condition that the standard deviation of luminance in the captured image falls within a preset threshold range for standard deviation.

3. A magnetic particle flaw detection method for inspecting the surface of a material to be inspected using magnetic powder, comprising: a magnetization unit for magnetizing the material to be inspected; a magnetic powder attachment unit for attaching the magnetic powder to the surface of the material to be inspected that has been magnetized by the magnetization unit; an ultraviolet irradiation unit for irradiating the surface of the material to be inspected to which the magnetic powder has been attached by the magnetic powder attachment unit with ultraviolet light; an imaging unit for generating multiple images by imaging regions on the surface of the material to be inspected that can be considered to be the same position, irradiated by the ultraviolet light unit, with multiple different exposure times or multiple different ultraviolet light outputs; a selection unit for selecting an image from the multiple images based on preset conditions; and an inspection unit for inspecting the surface of the material to be inspected based on the image selected by the selection unit, wherein the magnetic particle flaw detection apparatus comprises: a magnetization step of magnetizing the material to be inspected using the magnetization unit; and a magnetic powder attachment step of attaching the magnetic powder to the surface of the material to be inspected that has been magnetized by the magnetization unit using the magnetic powder attachment unit. A magnetic particle testing method comprising: an ultraviolet irradiation step of irradiating the surface of the material to be tested, on which magnetic powder has been attached by the magnetic powder attachment section, with ultraviolet light using the ultraviolet irradiation section; an imaging step of generating multiple images by using the imaging section to image regions on the surface of the material to be tested that can be considered to be in the same position, irradiated with ultraviolet light by the ultraviolet irradiation section, with multiple different exposure times or with multiple different ultraviolet light outputs; a selection step of using the selection section to select an image from the multiple images based on preset conditions; and an inspection step of using the inspection section to inspect the surface of the material to be tested based on the image selected by the selection section.

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