JP2014157038A - Apparatus and program for automatically measuring fatigue crack of object to be measured - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and program for automatically measuring fatigue crack of an object to be measured.SOLUTION: An apparatus for automatically measuring fatigue crack of an object includes a CCD camera 4, a triaxial moving stage device 7, and a computer 10. The computer 10 includes: a specific area extraction unit 29 which extracts a pattern located in a first specific area and a pattern located in a second specific area in an initial image on the basis of the position of imaging means; a corresponding area extraction unit 30 which extracts a pattern located in a second corresponding area in an image captured when a load is applied to a test piece T; a crack tip progress determination unit 31 which determines that a crack tip has progressed on condition that a difference between a distance of patterns located in the first and second specific areas and a distance of patterns located in the first and second corresponding areas is equal to or larger than a predetermined size. Every time the number of load applications reaches a predetermined number of times, on the basis of image data indicating an image captured by imaging means, a length and progress speed of a crack K are measured.

Description

  The present invention relates to an automatic measurement apparatus and program for a fatigue crack of an object to be measured.

  Conventionally, fatigue cracks are generated on a measured object such as a test piece with a fatigue testing machine, and the situation in which the fatigue crack is generated on the measured object is photographed with a CCD camera, and the image data representing the photographed image is analyzed. It is known to automatically measure the length and progress of a crack generated in an object to be measured (see, for example, Patent Documents 1 to 3).

  For example, in the crack propagation measuring device disclosed in Patent Document 1, an image obtained by photographing a test piece with a CCD camera equipped with a magnifying glass supported by a three-axis fine movement table is binarized, and binarized black and white. Based on the image, the tip of the crack is recognized by a microcomputer, and the CCD camera is made to automatically follow the propagation of the crack tip, thereby processing data representing the propagation of the crack tip in real time.

  Moreover, what was disclosed by patent document 2 is a video recording of the situation where a crack occurs in a test piece, generates a grayscale image by differentiating one still image, and between each edge of the generated grayscale image. Lines grouped from the distance are calculated, and the occurrence of cracks is determined from the calculated line spacing.

  In addition, what is disclosed in Patent Document 3 is that a mark is applied in advance to a crack generation surface of a test piece at a constant pitch in a direction in which the crack propagates, and a situation where a crack is generated is photographed. The crack tip is obtained based on the mark position above.

  In addition, a compliance method, a method of constantly monitoring an observer by displaying an image of a crack tip taken by a CCD camera on a display screen, and a method of visually observing the observer are known.

Japanese Utility Model Publication No. 4-90947 Japanese Patent Laid-Open No. 5-52729 JP 2001-281119 A

  However, in the technique described in Patent Document 1, when the crack tip progresses as a fine line, the crack cannot be distinguished from dirt or scratches. There was a problem that it could not be measured accurately.

  In addition, the technique described in Patent Document 1 has a shallow depth of field even when the magnification of the magnifier is increased, so that it is easy to be out of focus at the time of shooting during the test, and a crack is caused. Depending on the propagation direction of the crack, the crack is likely to be out of the field of view, so that there is a problem that the length and the propagation speed of the crack cannot be measured accurately.

  In addition, the techniques described in Patent Documents 2 and 3 have a problem that it is impossible to measure the crack propagation rate. Moreover, since the technique described in Patent Document 3 draws a mark on a crack of a test piece, there is a problem that an error is likely to occur, and the length and propagation speed of the crack cannot be accurately measured.

  In addition, the other methods described above, such as the compliance method, depend on the observer's visual observation. Therefore, especially when the crack tip progresses as a fine line, the crack length and propagation speed are accurately determined. However, there was a problem that it could not be measured.

  The present invention has been made to solve such a problem, and even when the crack tip progresses as a fine line, the length and speed of the crack can be accurately measured. An object of the present invention is to provide an automatic measuring apparatus and program for fatigue cracks.

  In order to achieve the above object, an automatic measurement device for a fatigue crack of an object to be measured according to the present invention includes: (1) an object of the object to be cracked in which a crack is generated by repeatedly applying a load to the object to be measured by a fatigue tester; An imaging means for imaging a surface part, a moving means for moving the imaging means according to the progress of the tip of the crack, and a predetermined time for adding the load each time the load is applied a predetermined number of times And an automatic measuring means for measuring at least one of the crack length and the propagation speed based on image data representing an image photographed by the imaging means every time The fatigue crack automatic measuring apparatus according to claim 1, wherein the automatic measuring means includes a pattern existing in a first specific area and a second pattern in an initial image captured before a crack is generated on a surface portion of the object to be measured. In certain areas Corresponding to a pattern existing in the first specific area in an image photographed when a load is applied to the object to be measured, a specific area extracting unit for extracting an existing pattern according to the position of the imaging means A corresponding area extracting unit for extracting a pattern existing in the first corresponding area and a pattern existing in the second corresponding area corresponding to the pattern existing in the second specific area; and the first and second specific areas It is determined that the crack tip has advanced on the condition that the difference between the pattern interval existing in the first and second corresponding regions is equal to or greater than a predetermined size. And a crack tip extension determination part.

  With this configuration, the apparatus for automatically measuring a fatigue crack of an object to be measured according to the present invention has an interval between patterns existing in the first and second specific regions and a pattern existing in the first and second corresponding regions. Since it is determined that the crack tip has progressed on the condition that the difference between the distance and the gap is equal to or larger than a predetermined size, even if the crack tip progresses as a fine line, the crack length and The progress rate can be measured accurately.

  The automatic measurement apparatus for fatigue cracks of an object to be measured according to the present invention is the automatic measurement apparatus for fatigue cracks of an object to be measured as described in (1) above. (2) The automatic measurement means starts a fatigue test. And further comprising a gauge judging section for judging that the crack tip has progressed on the condition that an electrical signal flowing through a crack gauge attached to the surface of the object to be measured has changed, and the fatigue by the gauge judging section On the condition that an external signal for instructing execution of the test has been input, instead of the crack tip progress determining unit, the gauge judging unit determines whether or not the crack tip has progressed. Also good.

  With this configuration, the automatic measurement device for a fatigue crack of an object to be measured according to the present invention is subject to a change in electrical signal due to the breaking of the conductive fine wire of the crack gauge according to the progress of the crack tip. Since it is determined that the crack tip has progressed, the crack length and the crack tip progress rate can be accurately calculated.

  The automatic measurement apparatus for fatigue cracks of an object to be measured according to the present invention is the automatic measurement apparatus for fatigue cracks of an object to be measured according to (1) or (2) above, (3) The image processing apparatus further includes a difference image generation unit that generates a difference image between an image when it is determined that the crack tip has advanced and the initial image, and the difference image generated by the difference image generation unit is displayed on a display device. You may make it display.

  With this configuration, the apparatus for automatically measuring a fatigue crack of an object to be measured according to the present invention causes a display device to display a difference image between an image when it is determined that a crack tip has advanced and an initial image. The developed crack can be clearly displayed on the display device.

  An automatic measurement apparatus for a fatigue crack of a measurement object according to the present invention is the automatic measurement apparatus for a fatigue crack of the measurement object according to any one of (1) to (3), wherein (4) the automatic measurement is performed. The means is provided on the condition that a vertical line corresponding to a crack tip in the difference image displayed on the display device is displayed on the display device, and the vertical line is displayed on the display device. And a recording unit that records on a storage medium the length of the crack and the number of times the load has been applied to the object to be measured.

  With this configuration, the apparatus for automatically measuring a fatigue crack of an object to be measured according to the present invention provides the length of the crack on the condition that the vertical line corresponding to the crack tip in the difference image is displayed on the display device. By recording the number of times the load is applied to the object to be measured on the storage medium, it is possible to record the process in which the crack has occurred.

  The automatic measurement apparatus for fatigue cracks of an object to be measured according to the present invention is the automatic measurement apparatus for fatigue cracks of an object to be measured according to any one of (1) to (4), wherein (5) the automatic measurement is performed. A means for instructing the fatigue testing machine to temporarily lower an excitation frequency to which the load is applied every time a load is applied to the object to be measured; An imaging instruction unit that instructs the imaging unit to perform imaging after instructing the fatigue tester to temporarily lower the frequency may be configured.

  With this configuration, the apparatus for automatically measuring a fatigue crack of an object to be measured according to the present invention temporarily reduces the excitation frequency in the fatigue testing machine when the imaging means images, so that the frame rate of the imaging means is set. An image without blurring can be picked up by the image pickup means without increasing the height.

  The automatic measurement apparatus for fatigue cracks of an object to be measured according to the present invention is the automatic measurement apparatus for fatigue cracks of an object to be measured according to any one of (1) to (5), wherein (6) the imaging means Is constituted by a CCD camera having an object side telecentric lens.

  With this configuration, the apparatus for automatically measuring a fatigue crack of an object to be measured according to the present invention images the surface portion of the object to be measured by a CCD camera equipped with an object-side telecentric lens, so that the crack propagation direction is shifted. Even if the crack is shifted upward or downward from the camera center, the influence of the aberration is small.

  The program according to the present invention includes (7) imaging means for photographing the surface portion of the object to be cracked by repeatedly applying a load to the object to be measured by a fatigue testing machine, and the progress of the tip of the crack. A moving means for moving the imaging means in response, and an image taken by the imaging means each time the load is applied a predetermined number of times or every time the load is applied for a predetermined time. An automatic measuring means for measuring at least one of the length and the propagation speed of the crack based on image data, and constituting the automatic measuring means of an apparatus for automatically measuring a fatigue crack of an object to be measured. A program to be executed by a computer, the pattern existing in the first specific area and the second specific area in the initial image captured before the surface portion of the object to be measured is cracked. Extracting a pattern to be performed according to the position of the imaging means, and a first correspondence corresponding to a pattern existing in the first specific area in an image photographed when a load is applied to the object to be measured Extracting a pattern existing in a region and a pattern existing in a second corresponding region corresponding to a pattern existing in the second specific region; and an interval between patterns existing in the first and second specific regions; And a step of determining that the crack tip has advanced on the condition that the difference between the interval between the patterns existing in the first and second corresponding regions is equal to or greater than a predetermined size. .

  With this configuration, the program according to the present invention allows the difference between the pattern interval existing in the first and second specific areas and the pattern interval existing in the first and second corresponding areas to be a predetermined magnitude. Since it is determined that the crack tip has progressed on the condition described above, even if the crack tip progresses as a fine line, the crack length and propagation speed can be accurately measured.

  According to the present invention, there is provided an automatic measuring device and program for a fatigue crack of a measured object, which can accurately measure the crack length and propagation speed even when the crack tip progresses as a fine line. be able to.

1 is a schematic hardware configuration diagram of an automatic measurement apparatus for fatigue cracks of an object to be measured according to an embodiment of the present invention. It is a functional block diagram of the outline of the automatic measurement apparatus of the fatigue crack of the to-be-measured object which concerns on embodiment of this invention. It is a figure which shows an example of the image at the time of no load which the initial image registration process part of the automatic measurement apparatus of the fatigue crack of the to-be-measured object which concerns on embodiment of this invention registered and displayed. It is a figure which shows an example of the pattern which exists in the 1st and 2nd specific area extracted from the initial image at the time of no load by the automatic measurement apparatus of the fatigue crack of the to-be-measured object which concerns on embodiment of this invention. . The automatic measurement apparatus for a fatigue crack of an object to be measured according to the embodiment of the present invention is configured to detect patterns existing in the first and second corresponding regions extracted from an image at the time of loading when the crack tip has advanced. It is a figure which shows an example. FIG. 6 is a schematic diagram in which the patterns existing in the first and second specific areas shown in FIG. 4 and the patterns existing in the first and second corresponding areas shown in FIG. It is a figure which shows an example of the difference image produced | generated by the difference image production | generation part of the automatic measurement apparatus of the fatigue crack of the to-be-measured object which concerns on embodiment of this invention. It is a figure which shows the display image which the vertical line display part of the automatic measurement apparatus of the fatigue crack of the to-be-measured object which concerns on embodiment of this invention displayed the vertical line according to the front-end | tip of the crack of a display image. It is a figure which shows the state which stuck the crack gauge used with the automatic measurement apparatus of the fatigue crack of the to-be-measured object which concerns on embodiment of this invention to the test piece. It is a figure for demonstrating the characteristic of the crack gauge of FIG. It is a flowchart which shows operation | movement of the automatic measurement apparatus of the fatigue crack of the to-be-measured object which concerns on this Embodiment of this invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an automatic measuring device for fatigue cracks of an object to be measured according to the present invention will be described below with reference to the drawings.

  First, a schematic configuration will be described.

  The automatic measurement apparatus 1 for a fatigue crack of an object to be measured according to an embodiment of the present invention generates a crack K in the test piece T by repeatedly applying a tensile force as a load to the test piece T as the object to be measured. The fatigue testing machine 2 is provided as shown in FIG.

  The automatic measuring apparatus 1 supports the CCD camera 4 as an imaging means for photographing the occurrence state of a crack K generated at a substantially central portion in the length direction of the test piece T, and moves in a three-dimensional direction while supporting the CCD camera 4. The triaxial moving stand device 7 as a moving means for moving the CCD camera 4 in real time according to the progress of the crack tip, and the timing and time of imaging of the CCD camera 4 are controlled. And a computer 10 as automatic measuring means for controlling movement.

  As the fatigue testing machine 2, a known fatigue testing machine can be used. For example, the fatigue testing machine 2 has a pair of upper and lower opposing crossheads, and an actuator for applying a load to one of the crossheads is linked, and the upper and lower ends of the test piece T are connected to the pair of crossheads. Is chucking.

  The fatigue testing machine 2 applies a tensile load that repeats various waveforms, such as a sine wave, a triangular wave, a trapezoidal wave, and a rectangular wave, at a frequency of about 10 Hz to 20 Hz, for example, to the test piece T at regular intervals. Crack K is generated. The test piece T is formed with a V-shaped concave portion on one side of the middle portion in the longitudinal direction, which serves as an initiation point for cracks.

  The controller 3 of the fatigue tester 2 outputs one count signal c to the computer 10 every time the fatigue tester 2 applies a load to the test piece T once. Thereby, the computer 10 can count the number of times the load is applied to the test piece T.

  Further, when the control unit 3 inputs a low excitation frequency instruction signal d described later from the computer 10, a frequency for applying a load to the test piece T for a certain time, for example, several seconds, according to the frame rate of the CCD camera 4. It is designed to switch low.

  The CCD camera 4 is a color CCD camera that can perform high-definition shooting. The CCD camera 4 includes an object-side telecentric lens 5 as an objective lens, and the light of the illumination 6 is introduced into the cylindrical body of the telecentric lens 5. Therefore, the CCD camera 4 can perform clear photographing by the light of the illumination 6 illuminating the test piece T brightly.

  When the CCD camera 4 receives the first imaging instruction signal a1 or the second imaging instruction signal a2 from the computer 10, the surface on which the crack K of the test piece T is generated at a different number of times depending on the type of the imaging instruction signal. The part is photographed. Specifically, the CCD camera 4 takes a picture once when the first photographing instruction signal a1 is input from the computer 10 before the fatigue test is started, that is, before the fatigue testing machine 2 applies a load. ing.

  When the CCD camera 4 receives the second imaging instruction signal a2 from the computer 10 after the fatigue test is started, the CCD camera 4 counts a predetermined time every time the load is added a predetermined number of times, for example, 1,000 times. For example, a plurality of times of shooting is performed for several seconds.

  The three-axis moving table device 7 includes an X table 7a provided on a fixed floor or the like and capable of fine reciprocation in the direction of arrow X, and a Y table 7b provided on the X table 7a and capable of fine reciprocation in the direction of arrow Y. And a Z table 7c provided on the Y table 7b and reciprocally movable in the arrow Z direction.

  The program of the present embodiment is created including a manual operation part that can control the movement of the three-axis moving table device 7 in the three-axis direction.

  For example, if the manual operation unit is selected for the content display in which manual control and automatic control are displayed on the display device 12 after activation, the X key of the key input unit 16 of the computer 10 is then pressed. If this is continued, the X table 7a will finely move in the X direction shown in FIG. 1, and if the X key is kept pressed while the shift key is pressed, the X table 7a will finely move in the direction opposite to the X direction.

  The fine movement in the Y direction of the Y table 7b and its reverse direction and the fine movement in the Z direction of the Z table 7c and its reverse direction are also operated by the Y key and the Z key in the same manner as the operation of the X key. Since this configuration is not a gist, further detailed explanation is omitted.

  The computer 10 includes a CPU (Central Processing Unit) 13, a RAM (Random Access Memory) 14, a ROM (Read Only Memory) 15, a key input unit 16, a large-capacity storage device such as a VRAM, HD, and DVD (not shown). .

  Furthermore, the computer 10 includes an output port A17, an output port B18, a LAN port 19, an RS232C20, an A / D port 21, and a counter port 22. The ROM 15 stores a program according to the present embodiment. As the ROM 15, an EEPROM or the like can be used.

  The computer 10 outputs the first photographing instruction signal a1 or the second photographing instruction signal a2 from the output port A17 to the controlled signal input port of the CCD camera 4.

  The first photographing instruction signal a1 is a signal that instructs the CCD camera 4 to photograph the test piece T at least once at a timing corresponding to a state in which no load is applied to the test piece T. The timing corresponding to the state in which no load is applied to the test piece T may be before or after the crack K is generated in the test piece T.

  The second photographing instruction signal a2 is a signal for instructing the CCD camera 4 to photograph the test piece T a plurality of times at a timing corresponding to a state in which a load is applied to the test piece T. Note that the number of times of instructing the instruction may be one. Alternatively, the second imaging instruction signal a2 is output after a low excitation frequency instruction signal d described later is output every time the load applied to the test piece T is counted a predetermined number of times, for example, 1,000. The

  The computer 10 inputs a photographic signal e output from the photographic signal output port of the CCD camera 4 to the LAN port 19 and performs image processing by the image processing unit 23.

  The computer 10 outputs a 3-channel motor control signal f from the RS232C 20 to the motor control amplifier 8. The motor control amplifier 8 amplifies the motor control signal f to generate a motor drive signal g, and outputs the motor drive signal g to a positioning control motor (not shown) of the X table 7a, Y table 7b, and Z table 7c of the three-axis moving table device 7.

  Prior to the start of the test, the computer 10 presses the X key, the Y key, and the Z key of the computer 10 to move the CCD camera 4 to a position facing the test piece T gripped by the fatigue testing machine 2. The movement of the three-axis moving table device 7 is controlled according to the input of an external signal. After starting the test, the computer 10 automatically controls the movement of the three-axis moving table device 7 without relying on the input of an external signal to press only the X table 7a.

  The computer 10 inputs an analog electrical signal h output from the crack gauge G from the A / D port 21, converts the analog electrical signal h into a digital signal with, for example, 256 gradations, takes it in, and determines the gauge as described later. A signal to be processed by the unit 36 is used.

  The computer 10 inputs a count signal c output from the control unit 3 of the fatigue testing machine 2 from the counter port 22 and activates a specific area extraction unit 29 described later every time the count signal c is counted 1,000. A timing signal is generated, and when the cumulative count is calculated and the recording unit 35 described later is activated, the crack length and the propagation speed are recorded in the storage unit 24 which is a storage medium described later. Yes.

  Now that the description of the external configuration has been completed, the substantial configuration including control will be described.

  FIG. 2 is a schematic functional block diagram of the automatic measurement apparatus for fatigue cracks of an object to be measured according to the above embodiment. As shown in FIG. 2, the computer 10 serving as an automatic measurement unit includes an image processing unit 23, a storage unit 24, and an arithmetic processing unit 25.

  The image processing unit 23 may be configured by the CPU 13 and the RAM 14 illustrated in FIG. 1, or may be configured by an image processing LSI. Here, the storage unit 24 is configured by the ROM 15 illustrated in FIG. 1, but may be configured by a large-capacity storage medium such as an HD (not illustrated). The arithmetic processing unit 25 is configured by the CPU 13 shown in FIG.

  A display device 12 is connected to the computer 10. As the display device 12, for example, a thin panel display device represented by a liquid crystal display device is employed.

  The arithmetic processing unit 25 reads the program according to the present embodiment stored in the ROM 15 to the RAM 14 and executes the program, thereby executing an initial image registration processing unit 26, an excitation frequency as shown in FIG. Instruction unit 27, imaging instruction unit 28, specific region extraction unit 29, corresponding region extraction unit 30, crack tip extension determination unit 31, moving means control unit 32, difference image generation unit 33, vertical line display unit 34, recording unit 35 And the gauge judgment part 36 is comprised.

  The arithmetic processing unit 25 displays the presence / absence of use of the crack gauge G on the display device 12 after starting the program, and selects either by pressing the Y key or the N key and inputting a signal. The use of the crack gauge G will be described later. The arithmetic processing unit 25 starts the initial image registration processing unit 26 after determining whether or not the crack gauge G is used.

  The initial image registration processing unit 26 outputs the first imaging instruction signal a1 from the output port A17 to the CCD camera 4 before the test piece T is cracked, and the CCD camera 4 is before the test piece T is cracked. An imaging signal e obtained by imaging once for the surface portion of the image is input via the LAN port 19.

  The initial image registration processing unit 26 registers an image obtained by causing the image processing unit 23 to perform image processing on the shooting signal e, for example, image data of the image shown in FIG. It is displayed on the display device 12.

  The initial image registration processing unit 26 is activated after the first activation of an excitation frequency instruction unit 27 to be described later, and an image obtained by photographing at the timing when the maximum load is applied to the test piece T. You may come to register.

  The arithmetic processing unit 25 outputs a start instruction signal b for causing the fatigue testing machine 2 to start a test to the control unit 3 of the fatigue testing machine 2 from the output port B18 after a predetermined time has elapsed since the start of the initial image registration processing unit 26. It is like that. Thereby, the fatigue testing machine 2 starts a fatigue test. That is, the fatigue testing machine 2 starts applying a load to the test piece T at a high excitation frequency.

  The arithmetic processing unit 25 outputs a count signal c corresponding to a numerical value “1” output from the control unit 3 from the counter port 22 every time the fatigue testing machine 2 applies a load to the test piece T once after the fatigue test is started. Input and count, and every time the count reaches a predetermined number, for example, 1,000, the excitation frequency instruction unit 27, the imaging instruction unit 28, the specific region extraction unit 29, the corresponding region extraction unit 30, and the crack tip extension The determination unit 31 is activated sequentially. Note that the arithmetic processing unit 25 may activate the excitation frequency instruction unit 27 and the like each time the load application time reaches a predetermined time.

  The arithmetic processing unit 25 first activates the excitation frequency instruction unit 27 every time the count number of the count signal c reaches 1,000. The excitation frequency instruction unit 27 instructs the control unit 3 of the fatigue testing machine 2 so that the excitation frequency of the load applied to the test piece T is lowered for a predetermined time, for example, for a few seconds, for example. Is output from the output port B18.

  As a result, the fatigue testing machine 2 lowers the excitation frequency at which the load is applied to the test piece T in accordance with the frame rate of the CCD camera 4 so that the CCD camera 4 can take a substantial still image.

  The arithmetic processing unit 25 activates the imaging instruction unit 28 after the fatigue testing machine 2 reaches a low excitation frequency. The imaging instruction unit 28 is configured to output from the output port A17 a second imaging instruction signal a2 that instructs the CCD camera 4 to perform imaging at the timing when the maximum load is applied to the test piece T.

  Accordingly, the CCD camera 4 moves the upper part and the lower part including the horizontal region at the center of the image, where the test piece T is expected to crack at the timing when the maximum load is applied to the test piece T, a plurality of times. You can shoot stably.

  The arithmetic processing unit 25 shoots the CCD camera 4 based on the second shooting instruction signal a2, inputs the shooting signal e output from the CCD camera 4 from the LAN port 19, and causes the image processing unit 23 to perform image processing. 3 is stored in the storage unit 24, and the plurality of images are displayed on the display device 12 so as to be updated in real time in a display area different from the image shown in FIG. The extraction unit 29 is activated.

  In the initial image shown in FIG. 3 captured before the crack is generated on the surface portion of the test piece T, the specific area extracting unit 29 has an expected position where a crack is expected to occur as shown in FIG. Of the upper part and the lower part, the pattern A1 existing in the specific area of the upper part corresponding to the position of the CCD camera 4 and the pattern B1 existing in the specific area of the lower part are extracted. Here, hereinafter, the specific area of the upper part is referred to as a first specific area, and the specific area of the lower part is referred to as a second specific area, but the first and second specific areas are upper and lower. When the crack propagates in the vertical direction, the first and second specific areas are the left and right areas sandwiching the crack.

  The arithmetic processing unit 25 instructs to store a plurality of images captured by the CCD camera 4 and processed by the image processing unit 23 in a predetermined storage area of the storage unit 24 based on the second imaging instruction signal a2. It has become.

  Next, the arithmetic processing unit 25 activates the corresponding region extraction unit 30. Corresponding region extraction unit 30 selects an image at the time of loading in a predetermined order from images photographed a plurality of times each time the count number of count signal c reaches 1,000, The pattern of the upper part and the pattern of the lower part corresponding to the pattern A1 existing in the first specific area and the pattern B1 existing in the second specific area of the lower part are extracted. Yes.

  When the corresponding region extraction unit 30 is activated in a state in which no crack is generated or in a state in which the crack tip K1 does not propagate, the center of photographing of the CCD camera 4 coincides with the crack tip K1 and From the image, a pair of patterns corresponding to substantially the same position within the range where the elastic deformation has increased in comparison with the patterns A1 and B1 are extracted.

  Further, as shown in FIG. 5, when the crack tip K1 is activated, the corresponding region extraction unit 30 is displaced in the X direction by the center of photographing of the CCD camera 4, and the CCD Since the gap of the crack K at the photographing center of the camera 4 is far away from the elongation caused by the elastic deformation due to the load, the pair of patterns A2 and B2 are extracted from the loaded image photographed in this state. It is supposed to be.

  The pattern A2 is a pattern existing in the first corresponding area corresponding to the pattern A1 existing in the first specific area, and the pattern B2 is changed to the pattern B1 existing in the second specific area. The pattern exists in the corresponding second corresponding area.

  The arithmetic processing unit 25 activates the crack tip extension determining unit 31 next to the corresponding region extracting unit 30. The crack tip extension determination unit 31 counts the pixels in the Y direction on the memory, for example, so that the interval W1 between the patterns A1 and B1 existing in the first and second specific regions and the first and second correspondences When the distance W2 between the patterns A2 and B2 existing in the region is calculated, the difference between the two distances is calculated, and the difference is larger than the threshold value for setting the elongation caused by the elastic deformation as a predetermined size. It is determined that the crack tip K1 has progressed.

  As a result, it is possible to eliminate the mistake of determining that the crack tip has advanced the elongation generated as an elastic deformation by the load, and it is possible to correctly determine only when the crack is surely generated. FIG. 6 schematically shows patterns A1 and B1 existing in the first and second specific regions and patterns A2 and B2 existing in the first and second corresponding regions after the crack tip has advanced. It is the figure which aligned and compared the difference of both space | interval.

  The arithmetic processing unit 25 determines the interval W1 between the pattern A1 existing in the first specific area and the pattern B1 existing in the second specific area, the pattern A2 existing in the first corresponding area, and the second corresponding area. When the difference between the existing pattern B2 and the interval W2 is less than a predetermined size, the activation of the crack tip extension determination unit 31 is terminated, and as described above, the count number of the next count signal c is 1 again. , 000 has passed, the operation returns to the operation of starting the excitation frequency instruction unit 27 described above.

  The crack tip progress determining unit 31 determines that the crack tip K1 has progressed when the difference between the interval W1 and the interval W2 is greater than or equal to a predetermined size. At the time of this determination, the arithmetic processing unit 25 sequentially activates the moving means control unit 32 and the difference image generation unit 33. Note that the order of activation of the moving means controller 32 and the difference image generator 33 may be reversed.

  The moving means control unit 32 outputs a control signal for moving the X table 7a from the RS232C20, amplifies it by the motor control amplifier 8, and outputs it as a drive signal to the control motor of the X table 7a of the three-axis moving table device 7. It is supposed to be.

  The CCD camera 4 is finely moved in accordance with a predetermined dimension, for example, 0.2 to 0.5 mm, along the progress direction of the crack tip based on the output of one control signal from the moving means control unit 32. Here, movement control of the Y table 7b and the Z table 7c is not performed.

  As a result, when the crack tip K1 progresses in the horizontal direction, the CCD camera 4 can continuously take an image of the upper and lower portions including the crack tip K1 without deviating from the crack tip K1 that has advanced. Follow.

  Since the CCD camera 4 includes the object-side telecentric lens 5, even when the crack tip K1 progresses obliquely upward or obliquely downward, the crack tip K1 is accurately photographed without distorting the distance due to aberration. Be able to.

  When the crack K is large at a stroke, the crack tip extension determination unit 31 determines that the crack tip K1 has progressed every time. As a result, the three-axis moving table device 7 advances in the X direction, and the CCD camera 4 can effectively follow the crack tip that has advanced greatly.

  The difference image generation unit 33 treats the image related to the load pattern (FIG. 5) as an absolute value image, performs difference processing with the image related to the initial pattern (FIG. 4), and generates a difference image M (FIG. 7). It is supposed to be.

  The arithmetic processing unit 25 stores the difference image M in the storage unit 24 and causes the display device 12 to display the difference image M in another display area. FIG. 7 shows a difference image M as an example related to the creation of the difference image generation unit 33.

  As can be seen from FIG. 7, according to the difference image M, it is possible to determine the progress of a thin crack that cannot be determined by the binarization process. That is, in the difference image M, even if the crack tip K1 is advanced very finely, the progress of the crack tip K1 can be revealed on the display device 12. The fatigue crack tester can easily know whether or not the crack tip K1 has progressed by observing the difference image M displayed on the display device 12.

  After the differential image M is displayed, the arithmetic processing unit 25 continuously counts the count signal c input to the counter port 22 and every time 1000 passes, the excitation frequency instruction unit 27, The imaging instruction unit 28, the crack tip extension determination unit 31, the movement means control unit 32, and the difference image generation unit 33 are sequentially activated.

  FIG. 8 shows a state in which the test operator inputs a vertical line L in accordance with the crack tip K1 in the image of the test piece T displayed in real time as shown in FIG.

  As shown in FIG. 7, the vertical line display unit 34 inputs a vertical line L to the crack tip K1 in the difference image M displayed on the display device 12 via the key input unit 16 or the mouse shown in FIG. To get.

  The recording unit 35 is activated in conjunction with the vertical line display unit 34 and stores the crack length corresponding to the input of the vertical line and the number of repetitions of the load from the start of the test in the storage unit 24. Note that the recording unit 35 may further store the time from the start of the test until the vertical line L is input in the storage unit 24.

  As a result, by inputting the vertical line L in line with the crack tip K1 that progresses one after another, the crack K is generated and progresses, and the crack K can be formed at a fine pitch in the process until it reaches the maximum length. The length and the number of repetitions of the load from the start of the test can be automatically recorded, and the progress history of the crack tip K1 can be easily and automatically recorded.

  From here, it demonstrates performing the automatic measurement of a fatigue crack using the crack gauge G. FIG.

  The arithmetic processing unit 25 attaches the crack gauge G to the test piece T (FIG. 9), and follows the guidance displayed on the display device 12 as an external signal using the crack gauge G for the test from the key input unit 16. When a Y key signal is input, the gauge determination unit 36 is activated in place of the crack tip extension determination unit 31.

  The crack gauge G is a rectangular ultrathin sheet that is not stretchable and easy to break, and the conductive fine wires extending in the vertical direction are parallel circuits at a pitch of 0.2 to 0.5 mm in the horizontal direction. With the progress of the crack tip K1, the resistance value Ω changes every time one conductive fine wire is cut from the end (FIG. 10).

  The gauge judgment unit 36 uses the fact that the crack gauge G is attached to the surface of the test piece T, and the wiring of the crack gauge G is cut one after another as the crack tip progresses. It is determined whether or not there has been a change in the amount of electricity to detect the progress of the crack tip K1, and an electrical signal for causing the CCD camera 4 to follow the progress of the crack tip K1 is obtained.

  The gauge determination unit 36 receives and monitors the signal of the crack gauge G, and determines that the crack tip K1 has advanced each time this signal changes. Therefore, if the conductive fine wires extending in the vertical direction of the crack gauge G are, for example, 0.2 mm pitch in the horizontal direction, the gauge determining unit 36 activates the moving means control unit 32 to change the signal of the crack gauge G. Every time, the X table 7a of the three-axis moving table device 7 is controlled to move 0.2 mm.

  For this reason, the gauge determination unit 36 can make the CCD camera 4 substantially follow the progress of the crack tip K1 based on the change in the amount of electricity from the crack gauge G attached to the test piece T. .

  The arithmetic processing unit 25 is activated by the alternative of the crack tip progress determining unit 31 when the gauge determining unit 36 is used. The arithmetic processing unit 25 causes the display device 12 to display whether or not to use the crack gauge G in the fatigue test, and waits for the input of an external selection signal.

  As a specific example, when the program starts, the arithmetic processing unit 25 displays, for example, “Do you want to perform a fatigue crack test using a crack gauge? Y key for YES, N for NO. Please press the key "message.

  When the external signal is input when the Y key of the key input unit 16 is pressed, the arithmetic processing unit 25 does not attach the crack gauge G to the surface of the test piece T. Please display the message "Please wear" on the display device 12, and when the crack gauge is attached to the surface of the test piece T and the electrical signal of the test piece T is input, the display of the message is terminated. ing.

  When there is an external signal input by pressing the N key of the key input unit 16, the arithmetic processing unit 25 executes it according to a program flow that does not use the crack gauge G.

  As described above, each time the load is applied to the test piece T, the arithmetic processing unit 25 calculates the length and the propagation speed of the crack K based on the imaging signal e captured by the CCD camera 4. The storage of the image and the calculation result in the storage unit 24 and the display on the display device 12 are controlled, and the CCD camera 4 and the three-axis moving table device 7 are controlled based on the calculation result.

  Next, the operation of the automatic measurement apparatus 1 for fatigue cracks of an object to be measured according to the present embodiment configured as described above, that is, the automatic measurement method will be described through the description of the flowchart shown in FIG.

  Before starting the program, the computer 10 is manually operated to adjust the three axes of the three-axis moving table device 7, and the imaging range of the CCD camera 4 is associated with the portion where the test piece T is cracked. Moreover, when the crack gauge G is used, the crack gauge G is stuck to the site | part in which the crack of the test piece T generate | occur | produces.

  When the program is started, the arithmetic processing unit 25 displays on the display device 12 a prompt to select whether or not to use the crack gauge G (step S1).

  When it is selected that the crack gauge G is not used, that is, when an external signal indicating that the N key is pressed is input from the key input unit 16, the arithmetic processing unit 25 uses the crack gauge G. The flag value indicating whether or not is held as “0” (step S2).

  The arithmetic processing unit 25 executes a program that uses the crack gauge G when an external signal indicating that the N key of the key input unit 16 is pressed is input in the determination of step S1.

  Next, the arithmetic processing unit 25 is activated by the initial image registration processing unit 26 and causes the initial image registration processing unit 26 to crack the test piece T at a timing corresponding to a state in which no load is applied to the test piece T. The upper and lower areas including the expected horizontal area where the image is generated are photographed by the CCD camera 4, the photographing signal e representing the image photographed by the CCD camera 4 is image-processed by the image processing unit 23, and the image processed image data is stored in the storage unit 24. And the image represented by the image data is displayed on the display device 12 (step S4).

  Next, the arithmetic processing unit 25 outputs a start instruction signal b to the fatigue testing machine 2 (step S5). Thereby, the fatigue testing machine 2 starts applying a load at a high excitation frequency, and outputs a count signal c from the control unit 3 every time a load is applied to the test piece T. Then, the arithmetic processing unit 25 counts the number of vibrations of the fatigue testing machine 2 based on the count signal c, and determines whether the count number has reached 1,000 (step S5).

  If the arithmetic processing unit 25 determines in step S5 that the count has reached 1,000 (determination of YES), it activates the excitation frequency instruction unit 27 and the excitation frequency instruction unit 27 performs a fatigue test. An instruction signal is output to the machine 2 so as to operate at a low excitation frequency (step S6). Thereby, the fatigue testing machine 2 operates at a low excitation frequency.

  Next, the arithmetic processing unit 25 activates the photographing instruction unit 28 and causes the photographing instruction unit 28 to instruct the CCD camera 4 to perform photographing at a timing corresponding to a state in which a load is applied to the test piece T. As a result, the CCD camera 4 captures an upper and lower area including an expected horizontal region in which the test piece T is cracked (step S7).

  Further, the arithmetic processing unit 25 causes the photographing instruction unit 28 to perform image processing on the photographing signal e from the CCD camera 4 in the image processing unit 23, and stores the image data subjected to the image processing in the storage unit 24, which is represented by the image data. An image is displayed on the display device 12 (step S7).

  Next, the arithmetic processing unit 25 determines whether or not an external signal instructing the end of the test is input (step S8). If it is determined that an external signal is not input, the arithmetic processing unit 25 determines that the test is continued, and the operation of the automatic measuring device 1 proceeds to step S9.

  Next, the arithmetic processing unit 25 determines whether or not the value of the flag is “1” (step S9). When the arithmetic processing unit 25 determines that the external signal is not inputted and the flag value is not “1”, the specific region extraction unit 29 is activated, and the specific region extraction unit 29 causes the pattern A1 existing in the specific region to be activated. , B1 are extracted (step S10).

  Next, the arithmetic processing unit 25 activates the corresponding region extracting unit 30 to cause the corresponding region extracting unit 30 to extract the patterns A2 and B2 existing in the corresponding region (step S11), and then the crack tip progress determining unit 31. Is activated, and the crack tip progress determining unit 31 determines whether or not the crack tip has advanced (step S12).

  Next, the arithmetic processing unit 25 activates the moving unit control unit 32, and the moving unit control unit 32 sets the X table 7a of the three-axis moving table device 7 in a dimension set in advance in the X direction, for example, 0.2 mm. Move (step S14). Thereby, the CCD camera 4 moves so as to follow the progress of the crack tip.

  Next, the arithmetic processing unit 25 activates the difference image generation unit 33 and causes the difference image generation unit 33 to make an image related to the load pattern as an absolute value image and perform a difference process with the image related to the initial pattern. Then, the difference image M is generated, the image data of the difference image M is stored in the storage unit 24, and the difference image M is displayed on the display device 12 (step S15).

  Next, the arithmetic processing unit 25 activates the vertical line display unit 34 and causes the vertical line display unit 34 to determine whether or not the vertical line L has been input within the time (steps S16 and S17). When a signal indicating that a vertical line L is to be input is input, the vertical line L is input in accordance with the crack tip K1, and then the recording unit 35 is activated. The length of the tip and the accumulated vibration number at that time are recorded in the storage unit 24 and displayed on the display device 12 (step S18).

  The operation of the automatic measuring device 1 returns to step S5 after step S18, and returns to step S5 if NO is determined in each of steps S5 and S12 and YES is determined in step S17.

  The arithmetic processing unit 25 determines whether or not an external signal for instructing the end of the test has been input (step S8). When it is determined that an external signal for instructing the end of the test has been input, 2 is output (step S19), and the control is ended.

  As described above, the arithmetic processing unit 25 displays the display device 12 so as to prompt the user to select whether or not to use the crack gauge G (step S1), and when the use of the crack gauge G is selected, That is, when an external signal indicating that the Y key is pressed is input from the key input unit 16, the value of the flag is changed to “1”, which is an identification code indicating that the crack gauge G is used (step S3). .

  Thereafter, the operation of the automatic measuring apparatus 1 proceeds from step S4 to step S7 in order, and the CCD camera 4 takes an image of the test piece T. When the operation proceeds to step S8 and no external signal indicating completion of the test is input. Proceed to step S9.

  If the value of the flag is “1” in the determination of step S9, the arithmetic processing unit 25 activates the gauge determining unit 36, and the gauge determining unit 36 determines whether or not the electric quantity of the crack gauge G has changed. Is determined (step S13). When it is determined that the electric quantity of the crack gauge G has changed, the operation of the automatic measuring device 1 proceeds to the series of steps S14 to S18 described above, and then returns to step S5. If it is determined that the amount has not changed, the process returns to step S5.

  As can be seen from the flowcharts described above, the automatic measurement apparatus 1 for a fatigue crack of an object to be measured according to the present embodiment includes a crack tip growth determination unit 31 and a crack gauge G when the crack gauge G is not used. The gauge judgment unit 36 in the case of use can be operated alternatively, and in any case, a difference image can be generated and displayed on the display device 12, and a vertical line can be formed in accordance with the crack tip. The length of the crack tip and the accumulated vibration frequency at that time can be recorded.

  As described above, the fatigue crack automatic measurement device 1 and the program according to the present embodiment, when the load is not applied by the initial image registration processing unit 26 in the specific region extraction unit 29. With respect to the photographed initial image shown in FIG. 3, the pattern A1 existing in the first specific area and the pattern B1 existing in the second specific area are extracted according to the position of the CCD camera 4.

  The automatic measuring device 1 and the program are present in the first corresponding region corresponding to the pattern A1 existing in the first specific region in the image shown in FIG. 4 taken when a load is applied to the test piece T. The pattern B2 existing in the second corresponding area corresponding to the pattern A2 and the pattern B1 existing in the second specific area are extracted.

  Then, as shown in FIG. 6, the automatic measuring apparatus 1 and the program include an interval W1 between the patterns A1 and B1 existing in the first and second specific areas and a pattern A2 existing in the first and second corresponding areas. The difference between the interval B2 and the interval W2 is calculated, and it is determined that the crack tip K1 has progressed on the condition that the difference is equal to or greater than a predetermined size.

  Here, the predetermined size is the elongation of the test piece T generated as an elastic deformation. Therefore, the automatic measuring apparatus 1 and the program eliminate the error that the crack tip K1 has advanced with respect to the elongation of the test piece T generated as an elastic deformation by the load, and whether the crack tip K1 has advanced. Judgment of whether or not.

  For this reason, even if the crack tip K1 progresses as a fine line, it can be reliably detected, and the CCD camera 4 can accurately follow the crack tip K1. And the propagation speed of the crack tip K1 can be accurately calculated.

  In addition, since the apparatus configured as described above controls the CCD camera 4 using the computer 10 to automatically shoot and automatically measure and displays the image and the calculation result on the display device 12 of the computer 10, it is not necessary to take part in the test. The work efficiency is improved and the human error at the time of specifying the crack tip position, which has occurred in the conventional fatigue crack measurement test, can be eliminated.

  Since the automatic measurement apparatus 1 for fatigue cracks of an object to be measured according to the present embodiment includes a gauge determination unit 36, a fatigue test can be performed using a crack gauge G. The imaging means can be made to accurately follow the progress of the tip K1, and the length of the crack K and the speed of the crack tip K1 can be accurately calculated.

  In the automatic measurement apparatus 1 for fatigue cracks of an object to be measured according to the present embodiment, the arithmetic processing unit 25 performs difference processing on two images, generates a difference image M, and displays the difference image M on the display device 12. It is possible to determine the progress of a thin crack that cannot be determined by the digitization process, and to visualize the situation in which the crack tip K1 has progressed extremely finely, which could not be grasped by a conventional automatic measuring apparatus that binarizes the image. .

  The automatic measurement apparatus 1 for a fatigue crack of an object to be measured according to the present embodiment includes a vertical line display unit 34 and a recording unit 35. Therefore, a new crack tip when the crack tip K1 progresses extremely finely. When the vertical line L is input in accordance with K1, even if the crack tip K1 advances very finely next, the position of the crack tip K1 is clarified by the difference image M generated by the difference processing and the vertical line L, and The display device 12 can easily monitor the timing at which the crack tip K1 advances.

  Then, by inputting a vertical line L in line with the crack tip K1 that occurs extremely finely, the crack K length and load in the process until the crack K is generated and progresses to reach its maximum length. The number of repetitions can be automatically recorded, and table data can be easily collected.

  Since the automatic measurement apparatus 1 for a fatigue crack of an object to be measured according to the present embodiment includes an excitation frequency instruction unit 27 and an imaging instruction unit 28, the repetition frequency of the load in the fatigue testing machine 2 is reduced. Therefore, it is possible to shoot without increasing the frame rate of the CCD camera 4, which leads to cost reduction.

  In the automatic measurement apparatus 1 for fatigue cracks of an object to be measured according to the present embodiment, the CCD camera 4 having the object-side telecentric lens 5 constitutes the imaging means. Even if it is shifted from the center of the camera 4, it is possible to take a clear image without losing the field of view, and it is possible to use a CCD camera 4 that can automatically follow the crack tip K1 accurately and does not have a large frame rate. Thus, the cost of the CCD camera 4 can be kept low.

  The fatigue crack propagation automatic measuring apparatus and program according to the present invention have the effect of accurately measuring the crack length and propagation speed even if the crack tip progresses as a fine line. This is useful for all technologies that automatically measure the length and speed of a crack by photographing the situation in which the tip develops with an imaging means.

  DESCRIPTION OF SYMBOLS 1 ... Automatic measuring device of fatigue crack of to-be-measured object, 2 ... Fatigue testing machine, 3 ... Control part, 4 ... CCD camera (imaging means), 5 ... Object side telecentric lens, 7 ... Triaxial moving stand apparatus (movement) Means), 10 Computer (automatic measurement means), 12 Display device, 23 Image processing unit, 24 Storage unit, 25 Calculation processing unit, 26 Initial image registration processing unit, 27 Excitation frequency instruction unit 28 ... Shooting instruction unit, 29 ... Specific region extraction unit, 30 ... Corresponding region extraction unit, 31 ... Crack tip extension determination unit, 32 ... Moving means control unit, 33 ... Difference image generation unit, 34 ... Vertical line display unit, 35: Recording unit, 36: Gauge determination unit, G: Crack gauge, K ... Crack, K1 ... Crack tip, T ... Test piece (object to be measured), A1 ... Pattern existing in the first specific area, B1 ... Pattern existing in the second specific area, A2 ... First correspondence Patterns present pass, B2 ... pattern present in the second corresponding region, L ... vertical line, d ... low vibration frequency instruction signal, M ... difference image

Claims (7)

Imaging means for photographing the surface portion of the object to be cracked by repeatedly applying a load to the object to be measured by a fatigue tester;
Moving means for moving the imaging means according to the progress of the tip of the crack;
Each time the load is applied a predetermined number of times or every time the load is applied for a predetermined time, the length of the crack is based on image data representing an image photographed by the imaging means. And an automatic measuring device for measuring a fatigue crack of an object to be measured, comprising:
The automatic measuring means includes
A pattern existing in the first specific area and a pattern existing in the second specific area in the initial image captured before the surface portion of the object to be measured is cracked are extracted according to the position of the imaging means. A specific area extraction unit;
A pattern existing in the first corresponding area corresponding to a pattern existing in the first specific area and a pattern existing in the second specific area in an image taken when a load is applied to the object to be measured A corresponding area extracting unit that extracts a pattern existing in a second corresponding area corresponding to
On the condition that the difference between the interval between the patterns existing in the first and second specific areas and the interval between the patterns existing in the first and second corresponding areas is equal to or greater than a predetermined size. An apparatus for automatically measuring a fatigue crack of an object to be measured, comprising: a crack tip progress determining unit that determines that a crack tip has progressed.   The automatic measuring means further includes a gauge determining unit that determines that the crack tip has advanced on the condition that an electrical signal flowing through a crack gauge attached to the surface of the object to be measured has changed at the start of a fatigue test. The crack tip is advanced by the gauge judgment unit in place of the crack tip progress judgment unit, provided that the gauge judgment unit inputs an external signal instructing execution of the fatigue test. The apparatus for automatically measuring a fatigue crack of an object to be measured according to claim 1, wherein it is determined whether or not it has been performed.   The automatic measurement unit further includes a difference image generation unit that generates a difference image between an image when it is determined that the crack tip has advanced and the initial image, and is generated by the difference image generation unit. 3. The apparatus for automatically measuring a fatigue crack of an object to be measured according to claim 1, wherein the difference image is displayed on a display device. The automatic measuring means includes
A vertical line display unit for displaying on the display device a vertical line corresponding to a crack tip in the difference image displayed on the display device;
And a recording unit that records on the storage medium the length of the crack and the number of times the load is applied to the object to be measured, on the condition that the vertical line is displayed on the display device. The apparatus for automatically measuring a fatigue crack of an object to be measured according to claim 3. The automatic measuring means includes
Each time a load is applied to the object to be measured a predetermined number of times, an excitation frequency instruction unit that instructs the fatigue testing machine to temporarily lower the excitation frequency to which the load is applied,
5. An imaging instruction unit for instructing the imaging unit to perform imaging after instructing the fatigue testing machine to temporarily lower the excitation frequency. An apparatus for automatically measuring a fatigue crack of an object to be measured.   6. The apparatus for automatically measuring a fatigue crack of an object to be measured according to claim 1, wherein the image pickup means comprises a CCD camera having an object side telecentric lens. Imaging means for photographing a surface portion of the object to be cracked when a load is repeatedly applied to the object to be measured by a fatigue testing machine, and moving means for moving the imaging means according to the progress of the tip of the crack Each time the load is applied a predetermined number of times or every time the load is applied for a predetermined time, based on image data representing the image photographed by the imaging means, An automatic measuring means for measuring at least one of the length and the growth rate, and a program for causing a computer constituting the automatic measuring means to execute the automatic measuring device for a fatigue crack of an object to be measured,
A pattern existing in the first specific area and a pattern existing in the second specific area in the initial image captured before the crack is generated on the surface portion of the object to be measured are extracted according to the position of the imaging means. Steps,
A pattern existing in the first corresponding area corresponding to a pattern existing in the first specific area and a pattern existing in the second specific area in an image taken when a load is applied to the object to be measured Extracting a pattern existing in a second corresponding region corresponding to
On the condition that the difference between the interval between the patterns existing in the first and second specific areas and the interval between the patterns existing in the first and second corresponding areas is equal to or greater than a predetermined size. A program for determining that the crack tip has advanced.

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