JP7344155B2 - Crack detection device, crack detection method and program for hole expansion test - Google Patents

Description

The present invention relates to a crack determination device, a crack determination method, and a program for a hole expansion test.

A hole expansion test is prescribed by JIS (Japanese Industrial Standards) as a method for evaluating the workability of metal materials. In the hole expansion test, a punch is pushed into a punched hole formed in a test piece of a metal material, and it is visually determined whether a crack has occurred in the thickness section (inner peripheral surface) of the punched hole. However, since visual crack detection inevitably involves variations due to individual differences, attempts have been made to automate crack detection. For example, Patent Document 1 discloses an apparatus that acquires positional data of the inner peripheral end of a punched hole from an image of a punched hole of a test piece, and performs a crack determination based on the acquired positional data.

Japanese Patent Application Publication No. 2011-209189

Patent Document 1 discloses an apparatus that performs crack determination with less variation than visual crack determination, but there is still room for further improvement in improving the accuracy of crack determination in hole expansion tests.

The present invention has been made based on this background, and an object of the present invention is to provide a crack detection device, a crack detection method, and a program that improve the accuracy of crack detection in punched holes in hole expansion tests. do.

In order to achieve the above object, a crack determination device according to a first aspect of the present invention includes:
A crack determination device that determines that a crack has occurred that penetrates a punched hole of a test piece in the thickness direction of the plate thickness cross section in a hole expansion test, comprising:
an acquisition unit that acquires image data generated by photographing a punched hole in a test piece that is expanded by a punch of a hole expansion tester in a direction opposite to the pushing direction of the punch;
a brightness profile generation unit that generates a brightness profile indicating the brightness on a brightness trace circle set in the plate thickness cross section of the punched hole of the test piece, based on the image data acquired by the acquisition unit;
A Fourier transform is performed to convert the data related to the brightness profile generated by the brightness profile generation unit into frequency axis data, and the high band and low band are cut in the frequency axis data subjected to the Fourier transform. a crack revealing section that performs a crack revealing process that performs inverse Fourier transform on the frequency axis data from which the low frequency band has been cut;
Equipped with

The low band is a band including a frequency smaller than a first frequency threshold,
The high band is a band that includes a frequency larger than a second frequency threshold that is larger than the first frequency threshold,
The first frequency threshold and the second frequency threshold may be set for each metal material of a test piece on which a hole expansion test is performed.

The brightness profile generation unit may generate a brightness profile that associates brightness on a brightness trace circle with a position of the brightness on the brightness trace circle.

The brightness profile generation unit generates a plurality of brightness profiles corresponding to the plurality of set brightness trace circles,
Further comprising an LUT conversion unit that calculates an average brightness based on the plurality of brightness profiles, and converts a value of brightness equal to or higher than the average brightness to the average brightness for each of the plurality of brightness profiles,
The crack revealing section may execute the crack revealing process using a brightness profile whose brightness value has been converted by the LUT converting section as data regarding the brightness profile.

further comprising an inner circumferential edge approximate circle generation unit that generates an inner circumferential edge approximate circle that approximates the inner circumferential edge of the punched hole based on the image data acquired by the acquisition unit,
The brightness profile generation section has the same center point as the inner edge approximate circle generated by the inner edge edge approximate circle generator, and sets a diameter larger than the inner edge edge approximation circle by a predetermined length. A brightness profile indicating the brightness on the brightness trace circle may be generated.

In order to achieve the above object, a crack determination method according to a second aspect of the present invention includes:
A crack determination method for determining that a crack has occurred that penetrates a punched hole of a test piece in the thickness direction of the plate thickness cross section in a hole expansion test, the method comprising:
an acquisition step of acquiring image data generated by photographing a punched hole of a test piece that is expanded by a punch of a hole expansion tester in a direction opposite to the pushing direction of the punch;
a brightness profile generation step of generating a brightness profile indicating the brightness on a brightness trace circle set in the plate thickness cross section of the punched hole of the test piece, based on the image data acquired in the acquisition step;
A Fourier transform is performed to convert the data related to the brightness profile generated in the brightness profile generation step into frequency axis data, and the high band and low band are cut in the frequency axis data subjected to the Fourier transform. a crack revealing step of performing a crack revealing process of performing inverse Fourier transform on the frequency axis data with the low frequency band cut;
including.

In order to achieve the above object, a program according to a third aspect of the present invention,
computer,
A program for functioning as a crack determination device that determines that a crack has occurred that penetrates a punched hole of a test piece in the thickness direction of the plate thickness cross section in a hole expansion test, the program comprising:
Acquisition means for acquiring image data generated by photographing a punched hole in a test piece that is expanded by a punch of a hole expansion tester in a direction opposite to the pushing direction of the punch;
Brightness profile generation means for generating a brightness profile indicating the brightness on a brightness trace circle set in the plate thickness cross section of the punched hole of the test piece, based on the image data acquired by the acquisition means;
A Fourier transform is performed to convert the data related to the brightness profile generated by the brightness profile generating means into frequency axis data, and the high band and low band are cut in the frequency axis data subjected to the Fourier transform. a crack revealer that performs a crack revealer process that performs inverse Fourier transform on the frequency axis data from which the low frequency band has been cut;
function as

According to the present invention, it is possible to provide a crack determination device, a crack determination method, and a program that improve the accuracy of crack determination in punched holes in a hole expansion test.

BRIEF DESCRIPTION OF THE DRAWINGS It is a front view which shows the structure of the hole expansion test apparatus based on embodiment of this invention. 1 is a sectional view showing the configuration of a testing machine according to an embodiment of the present invention. (a) to (c) are cross-sectional views showing the flow of a hole expansion test using a testing machine according to an embodiment of the present invention. FIG. 1 is a block diagram showing the hardware configuration of a crack determination device according to an embodiment of the present invention. (a) shows an example of a data table in the image data storage section, (b) shows an example of a data table in the brightness profile storage section, and (c) shows an example of a data table in the crack score storage section. FIG. FIG. 3 is a diagram for explaining a method of searching for an inner circumferential end of a punched hole on a photographed image according to an embodiment of the present invention. FIG. 3 is a diagram showing a plurality of brightness trace circles set outside an inner circumferential end approximate circle according to an embodiment of the present invention. FIG. 3 is a diagram showing a brightness profile in which each brightness on a brightness tracing circle is expressed in association with an angle according to an embodiment of the present invention. FIG. 7 is a diagram showing an LUT conversion straight line that converts brightness exceeding average brightness into average brightness. (a) to (e) are diagrams for explaining a series of processes for exposing cracks in a brightness profile. 8 is a diagram showing five brightness profiles corresponding to each brightness trace circle in FIG. 7. FIG. It is a graph which shows each crack score calculated based on the image data of the punched hole based on embodiment of this invention. This is a graph obtained by superimposing the graph of FIG. 12 along the time axis. 3 is a flowchart showing the flow of crack determination processing according to an embodiment of the present invention. 7 is a flowchart showing the flow of inner circumferential end approximate circle generation processing according to the embodiment of the present invention. 3 is a flowchart showing the flow of crack manifestation processing according to an embodiment of the present invention. It is a flowchart which shows the flow of crack score calculation processing concerning an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a crack detection device, a crack detection method, and a program according to the present invention will be described in detail with reference to the drawings. In each drawing, the same or equivalent parts are given the same reference numerals. In addition, in the embodiment, the direction in which the test piece is pushed horizontally from the test piece conveyor toward the testing machine is the Y-axis direction, and the direction on the same horizontal plane as the Y-axis direction and orthogonal to the Y-axis direction is the X-axis direction. , the direction (vertical direction) perpendicular to the X-axis direction and the Y-axis direction is the Z-axis direction.

FIG. 1 is a front view showing the configuration of a hole expansion test device 1 according to an embodiment. The hole expansion test device 1 includes a test piece conveyor 100, a testing machine 200, and a crack determination device 300. Each part is communicably connected to each other via a communication line or the like.

The test piece conveyor 100 is a device that supplies test pieces to the test machine 200 and collects the test pieces from the test machine 200. The test piece conveyor 100 includes a supply stocker 110 that stores a large number of test pieces to be supplied to the test machine 200, and a supply stocker 110 that supplies test pieces from the supply stocker 110 to the test machine 200 based on a control signal from the test machine 200. , a transport robot 120 that collects the test piece from the testing machine 200 after the test is completed, and a collection stocker 130 that stores the test piece collected by the transport robot 120.

The testing machine 200 receives the test piece supplied from the test piece transport machine 100, performs a hole expansion test on the received test piece, and returns the test piece after the hole expansion test to the test piece transport machine 100. It is a device.

The testing machine 200 pushes a punch into a punched hole formed in a test piece until a crack generated in the thickness section of the punched hole penetrates in the thickness direction of the sheet thickness section at at least one location. Thereafter, the inner diameter of the punched hole at the time of penetration is measured by a measuring device (not shown), and the ratio of the diameter of the punched hole at the time of penetration to the initial diameter of the punched hole (hole expansion ratio) is calculated. The hole expansion rate is an index for evaluating the workability of metal materials.

FIG. 2 is a cross-sectional view showing the configuration of the testing machine 200 according to the embodiment. The testing machine 200 includes a punch 210 that extends in a direction perpendicular to the test piece and is pushed into the punched hole of the test piece, a die 220 that holds the test piece into which the punch 210 is pushed, and a punch 210 that holds the test piece that is inserted into the punched hole of the test piece. and a camera 230 that takes pictures from the opposite side to the pushing direction.

The punch 210 is a cone-shaped tool for pushing and spreading. The punch 210 has a size that can enlarge the punched hole of the test piece to such an extent that a crack occurs in the thickness direction of the punched hole in the plate thickness cross section. The punch 210 is supported by an extrusion mechanism (not shown), for example, a hydraulic load mechanism, and is extruded toward the die 220 by the extrusion mechanism.

The die 220 includes a pair of wrinkle holders 221 and 222, and holds the test piece in a sandwiched state from both sides in the Z-axis direction. The wrinkle holders 221 and 222 are inserted with the punch 210 pushed out toward the die 220 with the test piece sandwiched between them, and have a size large enough to allow deformation around the punched hole of the test piece. Through holes 221a and 222a, which are central holes, are provided at the center of the holes 221 and 222, respectively.

The camera 230 photographs the punched hole in the test piece into which the punch 210 has been pushed. The camera 230 includes a camera module including, for example, a CCD (Charge Coupled Device) image sensor. The camera 230 photographs the punched hole in the test piece in a direction opposite to the pushing direction of the punch 210, and is arranged so that the center point of the punch 210 is the center of the image. The camera 230 photographs the punched hole at a predetermined period, for example, at a 200 msec period, at least while the punch 210 of the testing machine 200 is raised, and transmits the obtained image data to the crack determination device 300 in real time.

Next, with reference to FIGS. 2 and 3, the flow of the hole expansion test performed by the testing machine 200 according to the embodiment will be described. First, as shown in FIG. 3(a), the test machine 200 holds the test piece in a state where the pair of wrinkle holders 221 and 222 are separated from each other and the tip of the punch 210 slightly protrudes from the wrinkle holder 222 (initial state). A test piece conveyed from the conveyor 100 in the Y-axis direction is received. Thereafter, as shown in FIG. 3(b), the tip of the punch 210 is confirmed based on the photographed image of the camera 230, and the punch 210 is slightly raised to align the center point of the punched hole of the test piece with the tip of the punch 210. Perform alignment with the center point (centering).

Next, as shown in FIG. 3(c), with the wrinkle holder 221 kept stationary, the punch 210 and the wrinkle holder 222 are raised together, and the test piece is held between the pair of wrinkle holders 221 and 222. . When only the punch 210 is raised with the test piece sandwiched between the pair of wrinkle holders 221 and 222, the inner peripheral surface of the punched hole gradually turns over, and the thickness section of the punched hole changes from horizontal to horizontal, as shown in FIG. It gradually deforms so that it faces upward. The inner edge (contour) when the thickness section of the punched hole is turned up is the "inner edge", and the outer edge (outline) when the thickness section of the punched hole is turned up. is the "outer edge".

When the crack determination device 300 detects the rise of the punch 210, it starts a crack determination process in the punched hole of the test piece. Thereafter, when the crack determination device 300 detects that even one crack has occurred in the thickness direction of the punched hole in the thickness direction of the punched hole, the testing machine 200 that has received the information The punch 210 is stopped from rising. Then, the testing machine 200 lowers the punch 210 slightly to relieve the elastic stress of the test piece, then measures the inner diameter of the punched hole with a measuring instrument (not shown), and determines the diameter of the punched hole based on the measured inner diameter of the punched hole. Calculate the spread rate. After that, the testing machine 200 lowers the punch 210 and the wrinkle holder 222, and causes the test piece conveyor 100 to collect the test piece.
The above is the flow of the hole expansion test executed by the testing machine 200.

Returning to FIG. 1, the crack determination device 300 receives the image data of the punched hole from the testing machine 200, and detects a crack that penetrates the punched hole in the thickness direction of the sheet thickness cross section based on the image data. Determine what has occurred and notify the user. The crack determination device 300 includes, for example, an operation control panel 300A, a testing machine control panel 300B, and an automatic signal processing panel 300C.

FIG. 4 is a block diagram showing the hardware configuration of the crack determination device 300 according to the embodiment. The crack determination device 300 includes an operation section 310, an output section 320, a communication section 330, a storage section 340, and a control section 350. Each unit is communicably connected to each other via an internal bus (not shown) or the like.

The operation unit 310 receives a user's instruction and supplies an operation signal corresponding to the accepted operation to the control unit 350. The operation unit 310 includes, for example, a keyboard, a mouse, and a barcode reader. The operation unit 310 receives, for example, input of characters by the user, and reads various codes affixed to a test piece or the like.

The output unit 320 outputs information such as the position (angle) and crack score of the crack in the thickness section of the punched hole, information indicating that the crack penetrated in the thickness direction of the thickness section of the punched hole, etc. Notify the testing machine 200, external equipment, etc. For example, as shown in FIG. 1, the output unit 320 includes a display 321 that can be viewed by the user, and a printer 322 that prints various documents. The crack score is an index indicating the possibility that a crack candidate point detected based on the brightness information of the photographed image of the punched hole is actually a crack, and its details will be described later.

Returning to FIG. 4, the communication unit 330 is an interface that can be connected to a communication network such as the Internet, for example.

The storage unit 340 is exemplified by a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, and a hard disk drive. The storage unit 340 stores programs executed by the control unit 350 and various data. Furthermore, the storage unit 340 functions as a work memory for the control unit 350 to execute processing. Furthermore, the storage unit 340 includes an image data storage unit 341, a brightness profile storage unit 342, and a crack score storage unit 343.

FIG. 5A shows an example of a data table in the image data storage section 341. The image data storage unit 341 stores image data obtained by photographing a punched hole of a test piece in association with the sample number of the test piece, the date and time of photographing the image, and the like.

FIG. 5B shows an example of a data table in the brightness profile storage section 342. The brightness profile storage unit 342 stores the waveform data of the brightness profile in association with the sample number of the test piece, the date and time of image capture, and the identification number of the brightness trace circle.

The brightness profile is created by detecting the brightness while tracing a brightness tracing circle set outside the inner edge of the punched hole at a predetermined pitch in the circumferential direction in the photographed image of the test piece, and then adding the detected brightness to the brightness tracing circle. This is data expressed in association with angles around the center point. The brightness trace circle has the same center point as the circle that approximates the inner edge of the punched hole (the inner edge approximate circle), and is a circle whose diameter is increased by a predetermined length from the inner edge approximate circle. . Details of the brightness profile and brightness trace circle will be described later.

FIG. 5C shows an example of a data table in the crack score storage section 343. The crack score storage unit 343 stores the crack score in association with the sample number of the test piece, the date and time of image capture, and the angle of the crack candidate point. The crack score storage unit 343 stores a history of crack scores sequentially calculated based on each image of the punched hole of the test piece taken over time. The crack candidate point is a position on the brightness profile where a crack may have occurred in the thickness section of the punched hole of the test piece. The position on the brightness profile is specified by the radius and angle of the brightness profile. In addition, the crack score is an index indicating the possibility that a crack that penetrates the plate thickness section of the punched hole of the test piece in the thickness direction of the plate thickness section has occurred at each crack candidate point. The sample number of a test piece is a unique number assigned to identify each test piece.

Returning to FIG. 4, the control section 350 includes a CPU (Central Processing Unit) and the like, and controls each section of the crack determination apparatus 300. The control unit 350 executes the programs stored in the storage unit 340 to perform the crack determination process in FIG. 14, the inner circumference edge approximate circle generation process in FIG. 15, the crack manifestation process in FIG. 16, and the process in FIG. The crack score calculation process is executed respectively.

Functionally, the control unit 350 includes an image data acquisition unit 351, an inner circumference edge approximate circle generation unit 352, a brightness profile generation unit 353, an LUT (Lookup Table) conversion unit 354, and a crack manifestation unit 355. , a crack score calculation section 356 , a noise element removal section 357 , and a crack determination section 358 .

The image data acquisition unit 351 acquires image data of the punched hole, which is periodically photographed by the camera 230 of the testing machine 200 and stored in the image data storage unit 341 shown in FIG. 4(a).

The inner peripheral end approximate circle generation unit 352 measures the brightness at predetermined intervals in the radial direction from the virtual center point, which is the center point of the tip of the punch 210, in the photographed image of the punched hole, and searches for the maximum differential point in the radial direction. . Then, the inner circumferential end approximate circle generation unit 352 executes a search for the maximum differential point at a predetermined pitch in the circumferential direction over the entire circumference of the virtual center point, and based on the plurality of searched maximum differential points of brightness, Calculate the center coordinates and radius of the circumference approximate circle. The inner circumferential end approximate circle is, for example, an approximate circle generated by applying the least squares method of circles to the position data of the maximum differential point of brightness. The maximum differential point of brightness is the point where the brightness changes the most on a straight line extending in the radial direction from the virtual center point.

In addition, the inner circumferential end approximate circle generation unit 352 determines whether the average distance in the radial direction between the inner circumferential edge approximate circle and the maximum differential point of each brightness is less than or equal to the first threshold value. Determine whether to regenerate the peripheral edge approximation circle. The first threshold value is set in consideration of, for example, the initial value of the diameter of the punched hole in the test piece, the plate thickness, the material, and the like. If the average distance is less than or equal to the first threshold, it is determined that the error in the inner edge approximation circle is large, and the inner edge approximation is performed by, for example, increasing the number of searches for the maximum differential point of brightness. Generate a circle.

With reference to FIG. 6, a specific method of searching for the inner peripheral edge of a punched hole on a photographed image will be described. FIG. 6 is a plan view showing a punched hole into which the punch 210 has been pushed, as photographed by the camera 230, and the symbol x is the virtual center point. In the photographed image of the punched hole, the punch 210 has a relatively dark brightness, whereas the thickness section of the punched hole has a relatively bright brightness. Therefore, it can be understood that the maximum differential point of brightness, which is searched radially from the virtual center point in the thickness section of the punched hole, is a part of the inner circumferential end of the punched hole. Therefore, when the rightmost position is set to 0° and the maximum differential point of brightness is searched radially from the virtual center point at a predetermined circumferential pitch, for example, 1° pitch, each spot S ₁ , S ₂ , S ₃ , S ₄ , ...S _n , ... can obtain the maximum differential point of luminance.

In order to accurately detect the inner edge of a punched hole, it is possible to reduce the pitch in the circumferential direction and search for the maximum differential point of brightness, but considering computer processing time, for example, It is sufficient to detect the maximum differential point of luminance by dividing 360° at a pitch of 1°. In this case, a total of 360 luminance differential maximum points can be detected.

Next, position data (x _i , y _i ) of the maximum differential point of each brightness is generated based on the position of the pixel where the maximum differential point of each brightness is detected in the photographed image of the punched hole. Specifically, each pixel of the photographed image of the punched hole and the XY coordinates corresponding to the actual dimensions of the punched hole are associated in advance and stored in the data table of the storage unit 340. Then, by referring to the data table and reading which position in the XY coordinates corresponds to the pixel where the maximum differential point of each luminance was obtained, the position data (x _i , y _i ).

Next, the center coordinates and radius of the inner edge approximate circle are calculated based on the position data (x _i , y _i ) of the maximum differential point of each brightness. The center coordinates and radius of the inner circumferential end approximate circle may be calculated using a known method, for example, the least squares method of circles.

Returning to FIG. 4, the brightness profile generation unit 353 sets a plurality of brightness trace circles on the captured image of the test piece based on the inner edge approximate circle generated by the inner edge edge approximate circle generator 352, and each By detecting the brightness while tracing the brightness trace circle at a predetermined pitch in the circumferential direction, a brightness profile of each brightness trace circle is generated. Further, the brightness profile generation unit 353 causes the brightness profile storage unit 342 to store the generated brightness profile.

FIG. 7 is a diagram showing a plurality of brightness trace circles C1 to C5 set outside the inner edge approximate circle. Each of the brightness tracing circles C1 to C5 is set on the plate thickness section of the punched hole, and has a radius that increases at predetermined intervals. The number of brightness trace circles is arbitrary, but in consideration of computer processing time, etc., it is preferably within the range of 2 to 7, for example. The interval between the radii of each of the brightness trace circles C1 to C5 is set according to the number of brightness trace circles, the thickness of the test piece, and the like.

A specific method for setting a brightness trace circle on a photographed image of a test piece will be explained. First, the minimum brightness tracing circle is set so that it does not deviate inward from the inner peripheral edge of the punched hole. The inner edge of the punched hole has some distortion, unlike the inner edge approximate circle, which is a perfect circle. Therefore, if you set the brightness trace circle along the inner edge approximate circle, the thickness of the punched hole will change. There is a possibility that the brightness of a portion outside the cross section will be detected. For this reason, the minimum brightness trace circle is set with a certain margin from the inner circumferential edge approximate circle, for example, by increasing the diameter by several pixels from the inner circumferential edge approximate circle.

To explain in more detail, the minimum brightness tracing circle is, for example, approximately +2 pixels considering the distortion of the inner circumferential edge of the punched hole, and +2 pixels considering the calculation error of the center coordinates and inner diameter of the circumferential edge approximate circle. It is preferable to allow a margin of about +1 pixel in consideration of the size and other errors, and set the interval by a total of 5 pixels from the inner edge approximate circle. For example, if the imaging resolution is 0.05 mm, the length of 5 pixels corresponds to about 0.25 mm. The interval between the inner circumferential end approximate circle and the minimum brightness tracing circle is not limited to the above specific example, and is set as appropriate depending on the target test piece.

The interval between adjacent luminance tracing circles is also set to a length of, for example, five pixels, in accordance with the interval between the inner peripheral end approximate circle and the luminance tracing circle with the minimum diameter. Note that the interval between adjacent luminance tracing circles is not limited to the above specific example, and is appropriately set depending on the test piece to be tested.

When the test piece has a certain thickness, reflection unevenness may occur depending on the condition of the punched holes in the test piece and the material properties of the test piece. Therefore, depending on the state of uneven reflection, you can either widen the interval between the brightness trace circles and evaluate the cracks over the entire plate thickness section of the punched hole, or narrow the interval between the brightness trace circles and evaluate the brightness near the edge of the inner circle. Determine whether to evaluate cracks with tracing circles. Which one to adopt can be determined by conducting a hole expansion test on the target test piece in advance.

FIG. 8 is a diagram showing a brightness profile in which each brightness on a brightness tracing circle is expressed in association with an angle. The symbol x in FIG. 8 is the center point of the inner peripheral end approximate circle. The rightmost position of the brightness tracing circle is set as 0°, and the brightness at spots arranged clockwise at a predetermined circumferential pitch, for example, a 1° pitch is detected. If a brightness profile is drawn with the brightness detected from the photographed image as the vertical axis and the angle corresponding to each brightness as the horizontal axis, the waveform data shown in the upper part of FIG. 8 can be obtained.

The brightness of the photographed image of the punched hole is detected for each pixel of the photographed image. Therefore, in order to detect the brightness on the brightness tracing circle, it is necessary to devise measures so as not to use the brightness of the same pixel in the photographed image of the punched hole redundantly. For this reason, when a brightness trace circle is superimposed on a photographed image of a punched hole, which pixels are used to express the brightness trace circle are associated in advance.

This association may be performed for a large number of brightness trace circles having different diameters, and the positions of a large number of pixels corresponding to each brightness trace circle may be stored in the data table of the storage unit 340. Then, once the brightness tracing circle corresponding to the inner edge approximate circle is set, the brightness of the pixels corresponding to the set brightness tracing circle can be sequentially read by referring to the data table.

Note that reading the brightness in a captured image is not limited to the above method; for example, at each point that makes up each brightness trace circle, the brightness of the pixels around the point is read and calculated proportionally based on the area ratio of the pixels. It is also possible to use the brightness.

Returning to FIG. 4, the LUT conversion unit 354 calculates the average brightness based on the plurality of brightness profiles generated by the brightness profile generation unit 353, and averages the brightness value higher than the average brightness for each of the plurality of brightness profiles. Convert to brightness. The LUT conversion unit 354 converts the brightness value of the brightness profile by referring to a lookup table that stores the relationship between input brightness and output brightness. Hereinafter, this conversion will be referred to as "LUT conversion."

FIG. 9 is a diagram in which LUT conversion for converting luminance exceeding the average luminance into average luminance is expressed using a polygonal line. This polygonal line (LUT conversion straight line) is made up of two straight lines defining an input/output relationship such that when a luminance equal to or higher than the average luminance is input, the average luminance is output. The lookup table stores data indicating an LUT conversion straight line created based on all the brightness profiles generated by the brightness profile generation unit 353.

LUT conversion is performed on the brightness profile near the middle part between the inner and outer edges of the plate thickness cross section of the punched hole, where there is a bright area even though it is not the inner edge. This is to do so. LUT conversion is performed on the luminance profile so that the boundary between brightness and darkness, including the brightness portion, is not erroneously determined to be the inner circumferential surface.

Returning to FIG. 4, the crack revealing section 355 executes a crack revealing process for exposing the crack site on the brightness profile converted by the LUT converting section 354. A specific example of the crack manifestation process will be described below with reference to FIG.

First, by performing Fourier transform, for example, FFT (Fast Fourier Transform), on the brightness profile converted by the LUT conversion unit 354 shown in FIG. 10(a), the brightness profile is converted into a frequency Convert to axis data.

Next, as shown in FIG. 10(c), a digital filter is applied to the frequency axis data subjected to FFT to cut high band and low band data. The low band is a band that includes frequencies that are smaller than the first frequency threshold, and the high band is a band that includes frequencies that are larger than the second frequency threshold. Both the first frequency threshold and the second frequency threshold are individually set for each metal material forming the test piece.

The first frequency threshold is, for example, a low frequency of about several Hz, and may be set to cut large waves from the frequency axis data, and does not need to be adjusted for each condition of the hole expansion test. On the other hand, the second frequency threshold is adjusted so that even minute cracks as small as a hair can be detected in the test piece and unnecessary noise can be cut. The second frequency threshold is set by performing a hole expansion test according to the present embodiment on a target test piece in advance. By adjusting the first frequency threshold and the second frequency threshold, the degree of crack detection in the punched hole of the test piece can be adjusted.

Next, by performing inverse Fourier transform, for example, inverse FFT, on the frequency axis data in FIG. 10(c), a brightness profile shown in FIG. 10(d) is obtained. Then, by performing absolute value calculation on the brightness profile shown in FIG. 10(d), a brightness profile shown in FIG. 10(e) is obtained. Compared to the brightness profile before the series of processes, the brightness profile after the series of processes has been performed has the waveform at the crack site inverted, the overall waveform noise has been reduced, and as a result, the brightness profile has become brighter. The cleft area is obvious.

Returning to FIG. 4, the crack score calculation unit 356 calculates the plate thickness cross section of the punched hole of the test piece at each crack candidate point based on each brightness profile in which the crack site is revealed by the crack revealing unit 355. A crack score is calculated, which is an index indicating the possibility that a crack has occurred through the thickness of the plate in the thickness direction. Specifically, first, the luminance profile (360° omnidirectional waveform data) corresponding to the outermost luminance tracing circle (maximum luminance tracing circle) among multiple concentric luminance circles is traced sequentially from an angle of 0°. Then, a peak whose brightness (wave height value) is equal to or higher than a second threshold value is detected as a crack candidate point. Next, the brightness value (wave height value) of the peak detected as a crack candidate point in the maximum brightness trace circle and the maximum brightness trace circle other than the maximum brightness trace circle determined to constitute the same crack as the detected crack candidate point. The crack score at each crack candidate point is calculated by accumulating the peak brightness values (wave height values) in other brightness profiles. For example, at a detected crack candidate point, the brightness value (wave height value) of the peak detected as a crack candidate point in the maximum brightness trace circle is determined to be the same crack as the detected crack candidate point. The peak brightness values (peak values) in brightness profiles other than the maximum brightness tracing circle may be summed. The second threshold is set, for example, based on the results of past hole expansion tests.

Hereinafter, a specific example of a method for calculating a crack score from each brightness profile will be described with reference to FIG. 11. FIG. 11 is a diagram showing five luminance profiles P1 to P5 corresponding to each of the luminance trace circles C1 to C5 in FIG. 7. In each of the brightness profiles P1 to P5, crack sites are exposed through the processing shown in FIG.

First, a crack candidate point, which is a position on the polar coordinates where the brightness in the brightness profile P1 is equal to or higher than the second threshold shown by the dotted line in FIG. 11, is searched. Of the two peaks whose brightness is equal to or higher than the second threshold, the peak with the angle a1 is designated as the first crack candidate point (candidate 1), and the peak with the angle b1 is designated as the second crack candidate point (candidate 2). ). The wave height values of each peak are L11 and L12, respectively. Note that the peak angle of the brightness profile is the first value in the continuous range from when the brightness is equal to or higher than the second threshold until it becomes less than the second threshold when the brightness is read in the circumferential direction from an angle of 0°. It is indicated by the part with the highest brightness detected.

Next, the brightness profile P2 is searched for a peak indicating the same crack as the peak of the crack candidate point in the brightness profile P1. The brightness profile P2 is sequentially traced in the circumferential direction from the position at an angle of 0°, and when the brightness of the brightness profile P2 is equal to or higher than a predetermined threshold value, it is determined that a peak exists. In FIG. 11, brightness peaks are detected at angles a2 and b2, and the peak values of each peak are L21 and L22.

The peak of the brightness profile P2 is determined to be a peak indicating the same crack as the peak of the crack candidate point when the conditions expressed by the following equations (1) and (2) are satisfied, respectively.
|a1-a2|<α…(1)
|b1-b2|<α…(2)
For example, when α=10°, if the angle a1 of the peak of the first candidate of brightness profile P1 is 100°, and the angle a2 of the peak of the first candidate of brightness profile P2 is 105°, then both are the same. It can be judged that it shows a crack.

Next, the brightness profile P3 is searched for a peak indicating the same crack as the peak of the crack candidate point in the brightness profile P1. The brightness profile P3 is sequentially traced in the circumferential direction from the position at an angle of 0°, and when the brightness of the brightness profile P3 is equal to or higher than a predetermined threshold value, it is determined that a peak exists. In FIG. 11, a brightness peak is detected at an angle a3, and the peak value is L31. The brightness peak of the brightness profile P3 is determined to indicate the same crack as the peak of the first crack candidate point when the condition expressed by the following equation (3) is satisfied.
|a1-a3|<α…(3)

Similarly, each of the brightness profiles P4 and P5 is sequentially traced in the circumferential direction from the 0° angle position, and it is determined that a peak exists when the brightness of the brightness profiles P4 and P5 exceeds a predetermined threshold value. In FIG. 11, brightness peaks are detected at angles a4 and a5, respectively, and the peak values of each peak are L41 and L51.

Note that other methods may be used to determine whether each peak detected in each of the brightness profiles P2 to P5 constitutes the same crack as the peak of each crack candidate point in the brightness profile P1. For example, when the angular difference between the peak of brightness profile P1 and the peak of brightness profile P2 is within a predetermined range, the difference in angle between the peak of brightness profile P2 and the peak of brightness profile P3 is also within a predetermined range. If so, it may be determined that the peak of the brightness profile P2 and the peak of the brightness profile P3 indicate the same crack.

Furthermore, when the angular difference between the peak of brightness profile P1 and the peak of brightness profile P2 is r ₁ , the difference in angle r ₂ between the peak of brightness profile P2 and the peak of brightness profile P3 is less than or equal to r ₁ + r'. If so, it may be determined that the peak of the brightness profile P2 and the peak of the brightness profile P3 indicate the same crack.

Next, the peak brightness value of the crack candidate point of the brightness profile P1 and the peak brightness value of each brightness profile P2 to P5 indicating the same crack as the peak of the crack candidate point are accumulated. Then, calculate the crack score for each crack candidate point. For example, the peak brightness value of the crack candidate point of the brightness profile P1 and the brightness value of the peak of each brightness profile P2 to P5 indicating the same crack as the peak of the crack candidate point may be summed. . Specifically, the crack score of the first candidate is L11+L21+L31+L41+L51, and the crack score of the second candidate is L12+L22.
The above is a specific example of a method for calculating a crack score from each brightness profile.

Returning to FIG. 4, the noise element removal unit 357 applies a minimization filter to the history of crack scores at the crack candidate points calculated by the crack score calculation unit 356 to remove crack candidates containing noise elements. Remove points. The crack score history is a history in which crack scores calculated based on images of punched holes in test pieces taken over time are arranged in the order in which the images were taken. It is stored in the score storage section 343. The minimization filter receives the crack score history at the crack candidate point and outputs the minimum value from among the received crack score history. Crack candidate points for which the minimum value output from the minimization filter is less than the third threshold may be excluded as containing noise elements. The third threshold value is set for each metal material of the test piece based on the results of past hole expansion tests.

A method for removing crack candidate points including noise elements will be described with reference to FIGS. 12 and 13. FIG. 12 is a graph showing each crack score calculated based on the image data of the punched hole.

In Figure 12, two crack scores are expressed by each symbol, and these crack scores are determined by, for example, the striped pattern caused by oil adhering to the surface of the test piece, the material of the die, the shape of the punched hole, and the irregularities. There is also a possibility that noise elements generated by etc. are the cause. Therefore, in order to eliminate noise elements from crack scores, it is necessary to understand changes in crack scores over time.

FIG. 13 is a graph obtained by overlapping the graph of FIG. 12 with the graphs slightly shifted along the time axis. The dotted line in FIG. 13 connects symbols indicating crack scores that change over time. In the dotted line of the second candidate, the crack score changes rapidly, so it is judged that the crack score did not increase due to the propagation of a crack that gradually spread, but that it included a noise element that appeared instantaneously. can. On the other hand, for the dotted line of the No. 1 candidate, the crack score is stable over time, so it can be determined that it does not include noise elements. Therefore, in order to exclude crack candidate points that include noise elements, a minimization filter is applied to the history of multiple crack scores calculated over time, and if the output of the minimization filter is below a third threshold, then It is sufficient to exclude fissure candidate points.

Returning to FIG. 4, the crack determination unit 358 penetrates the plate thickness cross section of the punched hole in the thickness direction of the plate thickness cross section at the crack candidate point that was not removed by the noise element removal unit 357 as containing a noise element. Determine whether a crack has occurred. Specifically, in a crack candidate point that was not removed by the noise element removal unit 357 as including a noise element, if the crack score calculated by the crack score calculation unit 356 is equal to or higher than the fourth threshold, It is determined that a crack that penetrates the plate thickness section of the punched hole in the thickness direction of the plate thickness section has occurred at the crack candidate point corresponding to the crack score. The fourth threshold is set, for example, based on the results of past hole expansion tests.

The crack determination unit 358 outputs a control signal to stop the extrusion mechanism of the testing machine 200 when determining that a crack has occurred that penetrates the plate thickness section of the punched hole in the thickness direction of the plate thickness section. In addition, the crack determination unit 358 outputs to the output unit 320 the position of a crack candidate point where a crack has occurred that penetrates the plate thickness cross section of the punched hole in the thickness direction of the plate thickness cross section, the crack score, and the date and time when the image was taken. It is output to the storage unit 340 and stored in the storage unit 340.
The above is the hardware configuration of the crack determination device 300.

Next, a series of flows of crack determination processing executed by the crack determination apparatus 300 according to the embodiment will be described with reference to the flowcharts of FIGS. 14 to 17. The crack determination process is started when the punch 210 starts moving in the pushing direction after the centering of the test piece in the testing machine 200 is completed and the test piece is held by the wrinkle holders 221 and 222.

First, the image data acquisition section 351 acquires the image data of the test piece transmitted from the testing machine 200 and stored in the image data storage section 341 shown in FIG. 5(a) (step S1).

Next, the inner circumferential end approximate circle generation unit 352 executes inner circumferential end approximate circle generation processing for generating an inner circumferential end approximate circle of the punched hole (step S2). The flow of the inner circumferential end approximate circle generation process in step S2 will be described below with reference to the flowchart of FIG.

First, the inner peripheral end approximate circle generation unit 352 searches for the maximum differential point of luminance radially from the virtual center point, which is the center point of the punch 210 (step S21). The maximum differential point of luminance is searched radially around the virtual center point at a pitch of 1°, for example, as shown in FIG.

Next, the inner circumferential end approximate circle generation unit 352 determines whether the maximum differential point of luminance has been searched for the entire circumference around the virtual center point (step S22). If it is determined that the maximum differential point of brightness has been searched all around the virtual center point (step S22; Yes), the process advances to step S23. On the other hand, if it is determined that the maximum differential point of brightness has not been searched all around the virtual center point (step S22; No), the process returns to step S21. In the process of step S21, the maximum differential point of brightness is searched for by changing conditions such as the number of search points for the maximum differential point of brightness. For example, the maximum differential point of luminance may be searched at a pitch of 0.5° in the circumferential direction.

If Yes in the process of step S22, the inner circumferential end approximate circle generation unit 352 generates position data (x _i , y _i ) (step S23).

Next, the inner circumferential edge approximate circle generation unit 352 calculates the center coordinates and radius of the inner circumferential edge approximate circle based on the position data (x _i , y _i ) generated in step S23 (step S24), Return processing. For example, by applying the circular least squares method to the position data (x _i , y _i ) of the 360 luminance differential maximum points generated in step S23, the center coordinates and radius of the inner edge approximate circle can be determined. Calculate.
The above is the flow of the inner circumferential end approximate circle generation process.

Returning to FIG. 14, the inner circumferential end approximate circle generation unit 352 calculates the distance between the inner circumferential end approximate circle and the maximum differential point of each luminance based on the center coordinates and radius of the inner circumferential end approximate circle calculated in step S2. The average distance in the radial direction is calculated (step S3). For example, the distances in the radial direction between the inner circumferential end approximate circle and the 360 maximum luminance differential points are calculated, and the average value of all the calculated distances is calculated.

Next, the inner peripheral edge approximate circle generation unit 352 determines whether the average distance calculated in step S3 is less than or equal to a first threshold (step S4). If it is determined that the average distance calculated in step S3 is less than or equal to the first threshold (step S4; Yes), the process proceeds to step S5. On the other hand, if it is determined that the average distance calculated in step S3 is not less than or equal to the first threshold (step S4; No), the process returns to step S2. In step S2, for example, by narrowing the pitch in the circumferential direction, the number of spots for searching for the maximum differential point of luminance is increased, and an inner circumferential end approximate circle is generated.

If Yes in the process of step S4, the brightness profile generation unit 353 sets a plurality of brightness trace circles having a larger diameter than the inner edge approximate circle generated in step S2, and traces on the set brightness trace circles. By detecting the brightness at each angle at a predetermined pitch in the circumferential direction, a brightness profile in the brightness tracing circle is generated, and the brightness profile is stored in the brightness profile storage unit 342 shown in FIG. 5(b) (step S5). Specifically, as shown in FIG. 8, the brightness of pixels corresponding to the brightness tracing circle is read from the captured image, and a brightness profile showing the brightness associated with each angle is created. The brightness trace circle is set on the plate thickness section of the punched hole in the photographed image of the punched hole, and is set at a predetermined interval, for example, several pixels apart, outside the inner circumferential end approximate circle, as shown in FIG. Multiple items are set.

Next, the LUT conversion unit 354 performs LUT conversion on the brightness profile generated in step S5, and stores it in the brightness profile storage unit 342 (step S6). For example, a brightness histogram is created based on all the brightness profiles, and the average brightness is calculated from the created brightness histogram. Then, with reference to the lookup table expressed by the LUT conversion straight line shown in FIG. 9, for each of the plurality of brightness profiles, the value of brightness greater than or equal to the average brightness is converted to the average brightness.

Next, the crack revealing unit 355 performs a crack revealing process to make cracks obvious on the brightness profile converted in step S6 (step S7). The flow of the crack manifestation process will be described below with reference to the flowchart of FIG. 16.

First, the crack revealing unit 355 performs FFT on the luminance profile subjected to LUT conversion in step S6 (step S71). For example, by performing FFT on the brightness profile shown in FIG. 10(a), the waveform of the brightness profile is converted into frequency axis data shown in FIG. 10(b).

Next, the crack revealing unit 355 cuts the high frequency band and the low frequency band of the frequency axis data subjected to the FFT in step S71 (step S72). For example, the frequency axis data shown in FIG. 10(b) is passed through a digital filter that cuts high and low bands to generate the frequency axis data shown in FIG. 10(c).

Next, the crack revealing unit 355 performs inverse FFT on the frequency axis data from which the high frequency band and the low frequency band were cut in step S72 (step S73). For example, by performing inverse FFT on the frequency axis data shown in FIG. 10(c), it is possible to obtain a luminance profile in which the overall noise of the waveform is reduced as shown in FIG. 10(d).

Next, the crack revealing unit 355 performs absolute value calculation on the brightness profile subjected to the inverse FFT in step S73 (step S74), and returns the process. For example, when absolute value calculation is performed on the brightness profile shown in FIG. 10(d), the crack site is reversed and a brightness profile in which the crack site is exposed is obtained as shown in FIG. 10(e). I can do it. Note that whether or not to perform absolute value calculation on the luminance profile that has been subjected to the inverse FFT can be appropriately selected in consideration of the processing described later.
The above is the flow of the crack manifestation process.

Returning to FIG. 14, when the crack revealing process in step S7 is completed, the brightness profile generation unit 353 determines whether the brightness profile has been revealed for all brightness tracing circles (step S8). For example, if five brightness trace circles C1 to C5 are set as shown in FIG. 7, it is determined whether all five brightness profiles have been realized.

If it is determined that the brightness profile has been revealed for all the brightness trace circles (step S8; Yes), the process advances to step S9. On the other hand, if it is determined that there is a brightness tracing circle whose brightness profile is not revealed (step S8; No), the process returns to step S7.

In the case of Yes in the process of step S8, the crack score calculation unit 356 determines that the crack site has been revealed through the process of step S7 and corresponds to the outermost maximum brightness trace circle among the plurality of concentric brightness traces. A crack score calculation process is executed to detect crack candidate points from the brightness profile and calculate a crack score at each detected crack candidate point (step S9). The flow of the crack score calculation process will be described below with reference to the flowchart in FIG. 17.

First, the crack score calculation unit 356 searches for a crack candidate point in the brightness profile corresponding to the maximum brightness trace circle converted in step S7, and determines whether or not a crack candidate point is detected (step S91 ). The crack candidate point is a position where the peak wave height value is equal to or greater than the second threshold in the brightness profile corresponding to the maximum brightness trace circle, and is expressed by an angle around the center point of the brightness trace circle. If it is determined that a crack candidate point has been detected (step S91; Yes), the process advances to step S92. On the other hand, if it is determined that no crack candidate point has been detected (step S91; No), it can be determined that a crack that penetrates the punched hole in the test piece in the plate thickness direction has not occurred. The process returns to step S1 of the crack determination process.

If Yes in the process of step S91, the crack score calculation unit 356 calculates the crack score of each crack candidate point searched in step S91 (step S92). For example, the difference between the angle of the crack candidate point detected from the brightness profile corresponding to the maximum brightness trace circle and the angle at which the peak of the brightness profile corresponding to the other brightness trace circles exists is calculated. Next, if the absolute value of the difference is smaller than a predetermined value, the peak of the brightness profile corresponding to another brightness trace circle is detected as a peak indicating the same crack as the peak detected as a crack candidate point. do. Next, by summing the brightness value (crest value) of the crack candidate point in the brightness profile corresponding to the maximum brightness trace circle and the peak brightness value (crest value) in other brightness profiles, Calculate the crack score of the crack candidate point.

In the specific example of FIG. 11, the crack score of the first candidate is L11+L21+L31+L41+L51, and the crack score of the second candidate is L12+L22. For example, the crack score is calculated by summing the wave height values of each brightness profile, so the more cracks are connected from the outer edge to the inner edge of the plate thickness section of the punched hole, the larger the value becomes. .

Next, the crack score calculation unit 356 stores the crack score calculated in step S92 in the crack score storage unit 343 in FIG. It is stored (step S93) and the process is returned.
The above is the flow of the crack score calculation process.

Returning to FIG. 14, the noise element removal unit 357 minimizes the history of crack scores sequentially calculated in the crack score calculation process of step S9 and stored in the crack score storage unit 343 of FIG. 5(c). By applying a filter, crack candidate points including noise elements are removed (step S10). Specifically, crack candidate points for which the output of the minimization filter that receives the history of the crack score calculated for each image data of the punched hole is below the third threshold may be removed as including noise elements. .

Next, the crack determination unit 358 detects a crack that penetrates the plate thickness section of the punched hole in the thickness direction of the plate thickness section at the crack candidate point that was not removed as containing a noise element in the process of step S10. It is determined whether or not this has occurred (step S11). Specifically, if the crack score calculated in step S9 is equal to or higher than the fourth threshold in a crack candidate point that was not removed as containing a noise element in the process of step S10, the crack score corresponding to the crack score is It is determined that a crack that penetrates the plate thickness cross section of the punched hole in the thickness direction of the plate thickness cross section has occurred at the crack candidate point. On the other hand, if the crack score calculated in the process of step S9 is less than the fourth threshold in the crack candidate points that were not removed as including noise elements in the process of step S10, or if all the crack candidate points are removed in the process of step S10, When the crack candidate point is removed, it is determined that no crack has occurred that penetrates the plate thickness section of the punched hole in the thickness direction of the plate thickness section.

If it is determined that a crack has occurred that penetrates the plate thickness section of the punched hole in the thickness direction of the plate thickness section (step S11; Yes), the process proceeds to step S12. On the other hand, if it is determined that no crack has occurred that penetrates the plate thickness section of the punched hole in the thickness direction of the plate thickness section (step S11; No), the process returns to step S1.

If Yes in the process of step S11, the crack determination unit 358 outputs a control signal to stop the extrusion mechanism of the testing machine 200 (step S12). In addition, the crack determination unit 358 obtains information regarding the position of a crack candidate point where a crack has occurred that penetrates the plate thickness section of the punched hole in the thickness direction of the plate thickness section, the crack score, the date and time of image capture, etc. It is output to the output unit 320 and stored in the storage unit 340, and the process ends.
The above is the flow of the crack determination process.

Thereafter, upon receiving a control signal to stop the extrusion mechanism from the crack determination device 300, the testing machine 200 stops the operation of the extrusion mechanism, and measures the inner diameter of the punched hole using a measuring instrument (not shown). Then, the testing machine 200 calculates the hole expansion rate based on the measured inner diameter, and stores the calculated hole expansion rate in the memory in association with the sample number of the test piece.

As explained above, the crack determination device 300 according to the embodiment performs Fourier transform to convert data related to a brightness profile into frequency axis data, and performs a high frequency band and a low frequency band in the frequency axis data subjected to the Fourier transform. A crack revealing unit 355 is provided which performs inverse Fourier transform on the frequency axis data from which the high frequency band and the low frequency band have been cut. Therefore, the crack site becomes apparent in the brightness profile generated from the photographed image of the punched hole, and as a result, the accuracy of crack determination in the hole expansion test can be improved.

The present invention is not limited to the embodiments described above, and modifications described below are also possible.

(Modified example)
In the above embodiment, the average distance in the radial direction between the inner edge approximation circle and the maximum differential point of each luminance is calculated, and if the calculated average distance is less than or equal to the first threshold, the inner edge approximation is performed. Although the process of generating a circle was executed (steps S3 and S4), the present invention is not limited to this. For example, after executing the inner circumferential edge approximate circle generation process (step S2), steps S3 and S4 may be omitted and the process of generating a brightness profile (step S5) may be executed.

In the embodiment described above, the crack score calculation process (step S9) is executed after the crack manifestation process (step S7) is executed, but the present invention is not limited to this. For example, if priority is given to the processing time over the accuracy of crack determination in the crack determination process, the crack score calculation process may be performed without performing the crack manifestation process.

Specifically, among the crack profiles obtained in step S5, the angle at which the peak of brightness detected in the brightness profile of the outermost maximum brightness trace circle is less than or equal to a predetermined threshold is determined as a crack candidate point. The brightness value (wave height value) of the peak detected as a crack candidate point in the maximum brightness trace circle and the maximum brightness trace circle determined to constitute the same crack as the detected crack candidate point. What is necessary is just to perform the crack score calculation process which calculates the crack score of a crack candidate point by summing the value of the brightness|luminance of the peak (wave height value) in each brightness profile other than that.

In each brightness profile other than the maximum brightness trace circle, it may be determined that a peak exists if the brightness value (crest value) is equal to or less than a predetermined threshold value. In addition, if the angle of the peak in each brightness profile other than the maximum brightness trace circle is within a predetermined range based on the angle at which the crack candidate point exists, then the peak is the same as the crack candidate point. It is only necessary to judge that it constitutes a fissure.

Alternatively, the waveform of the brightness profile in which cracks have been exposed through the crack revealing process may be displayed on the display 321 or the like of the output unit 320 without executing the crack score calculation process. In addition, without executing the crack score calculation process, all of the brightness peaks detected in all the brightness profiles in which cracks have been exposed by the crack revealing process are equal to or higher than a predetermined threshold, and If the peak of the brightness exists within a predetermined range (for example, within a range of 10 degrees), it is determined that a crack that penetrates through the thickness direction of the plate thickness cross section of the punched hole has occurred in the plate thickness cross section. However, a control signal for stopping the extrusion mechanism of the testing machine 200 may be output.

In the embodiment described above, the noise element removal process (step S10) is executed after the crack score calculation process (step S9) is executed, but the present invention is not limited to this. For example, depending on the type of metal material constituting the test piece, there is a low possibility that noise will occur, so the process in step S10 may be omitted.

In the embodiment described above, various data are stored in the storage unit 340 of the crack determination device 300, but the present invention is not limited thereto. For example, all or part of various data may be stored in an external server, computer, etc. via a communication network.

In the above embodiment, the crack determination apparatus 300 operates based on the programs stored in the storage unit 340, but the present invention is not limited thereto. For example, a functional configuration realized by a program may be realized by hardware.

In the above embodiment, the crack determination device 300 is, for example, a dedicated system, but the present invention is not limited to this. For example, the crack determination device 300 may be realized by a general-purpose computer, or may be a computer provided on a cloud.

In the embodiment described above, the process executed by the crack determination device 300 is realized by the device having the above-described physical configuration executing the program stored in the storage unit 340. It may be realized as a program, or it may be realized as a storage medium on which the program is recorded.

In addition, the program for executing the above processing operations can be read by a computer such as a flexible disk, CD-ROM (Compact Disk Read-Only Memory), DVD (Digital Versatile Disk), MO (Magneto-Optical Disk), etc. By storing and distributing the program in a non-transitory recording medium and installing the program on a computer, an apparatus that executes the above-described processing operations may be configured.

The above-mentioned embodiments are illustrative, and the present invention is not limited thereto, and various embodiments are possible without departing from the spirit of the invention described in the claims. The components described in each embodiment and modification example can be freely combined. Furthermore, inventions equivalent to the inventions described in the claims are also included in the present invention.

1 Hole expansion test device 100 Test piece transporter 110 Supply stocker 120 Transport robot 130 Collection stocker 200 Testing machine 210 Punch 220 Dies 221, 222 Wrinkle retainer 221a, 222a Through hole 230 Camera 300 Crack determination device 300A Operation control panel 300B Testing machine Control panel 300C Automatic signal processing panel 310 Operation section 320 Output section 321 Display 322 Printer 330 Communication section 340 Storage section 341 Image data storage section 342 Brightness profile storage section 343 Crack score storage section 350 Control section 351 Image data acquisition section 352 Inner circumference End approximate circle generation unit 353 Brightness profile generation unit 354 LUT conversion unit 355 Crack manifestation unit 356 Crack score calculation unit 357 Noise element removal unit 358 Crack determination unit

Claims (7)

A crack determination device that determines that a crack has occurred that penetrates a punched hole of a test piece in the thickness direction of the plate thickness cross section in a hole expansion test, comprising:
an acquisition unit that acquires image data generated by photographing a punched hole in a test piece that is expanded by a punch of a hole expansion tester in a direction opposite to the pushing direction of the punch;
a brightness profile generation unit that generates a brightness profile indicating the brightness on a brightness trace circle set in the plate thickness cross section of the punched hole of the test piece, based on the image data acquired by the acquisition unit;
A Fourier transform is performed to convert the data related to the brightness profile generated by the brightness profile generation unit into frequency axis data, and the high band and low band are cut in the frequency axis data subjected to the Fourier transform. a crack revealing section that performs a crack revealing process that performs inverse Fourier transform on the frequency axis data from which the low frequency band has been cut;
A crack detection device equipped with. The low band is a band including a frequency smaller than a first frequency threshold,
The high band is a band that includes a frequency larger than a second frequency threshold that is larger than the first frequency threshold,
The first frequency threshold and the second frequency threshold are set for each metal material of the test piece on which the hole expansion test is performed.
The crack determination device according to claim 1. The brightness profile generation unit generates a brightness profile that associates brightness on a brightness trace circle with a position of the brightness on the brightness trace circle.
The crack determination device according to claim 1 or 2. The brightness profile generation unit generates a plurality of brightness profiles corresponding to the plurality of set brightness trace circles,
Further comprising an LUT conversion unit that calculates an average brightness based on the plurality of brightness profiles, and converts a value of brightness equal to or higher than the average brightness to the average brightness for each of the plurality of brightness profiles,
The crack revealing unit executes the crack revealing process using a brightness profile whose brightness value has been converted in the LUT converting unit as data regarding the brightness profile.
The crack determination device according to any one of claims 1 to 3. further comprising an inner circumferential edge approximate circle generation unit that generates an inner circumferential edge approximate circle that approximates the inner circumferential edge of the punched hole based on the image data acquired by the acquisition unit,
The brightness profile generation section has the same center point as the inner edge approximate circle generated by the inner edge edge approximate circle generator, and sets a diameter larger than the inner edge edge approximation circle by a predetermined length. generate a brightness profile showing the brightness on the brightness trace circle,
The crack determination device according to any one of claims 1 to 4. A crack determination method for determining that a crack has occurred that penetrates a punched hole of a test piece in the thickness direction of the plate thickness cross section in a hole expansion test, the method comprising:
an acquisition step of acquiring image data generated by photographing a punched hole of a test piece that is expanded by a punch of a hole expansion tester in a direction opposite to the pushing direction of the punch;
a brightness profile generation step of generating a brightness profile indicating the brightness on a brightness trace circle set in the plate thickness cross section of the punched hole of the test piece, based on the image data acquired in the acquisition step;
A Fourier transform is performed to convert the data related to the brightness profile generated in the brightness profile generation step into frequency axis data, and the high band and low band are cut in the frequency axis data subjected to the Fourier transform. a crack revealing step of performing a crack revealing process of performing inverse Fourier transform on the frequency axis data with the low frequency band cut;
Crack detection method including computer,
A program for functioning as a crack determination device that determines that a crack has occurred that penetrates a punched hole of a test piece in the thickness direction of the plate thickness cross section in a hole expansion test, the program comprising:
Acquisition means for acquiring image data generated by photographing a punched hole in a test piece that is expanded by a punch of a hole expansion tester in a direction opposite to the pushing direction of the punch;
Brightness profile generation means for generating a brightness profile indicating the brightness on a brightness trace circle set in the plate thickness cross section of the punched hole of the test piece, based on the image data acquired by the acquisition means;
A Fourier transform is performed to convert the data related to the brightness profile generated by the brightness profile generating means into frequency axis data, and the high band and low band are cut in the frequency axis data subjected to the Fourier transform. a crack revealing means that performs a crack revealing process of performing inverse Fourier transform on the frequency axis data from which the low frequency band has been cut;
A program to function as

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