JP2020073863A - Crack tip end position detecting method - Google Patents

Abstract

To simplify detection of a tip end position when a crack grows which is generated in a sample caused by applying a load.SOLUTION: A crack tip end position detecting method of the present technology has a tip end position detection procedure. The crack tip end position detecting method detects the tip end position of the growing crack on the basis of the light emission of a coated stress-induced emitter, when the crack formed on a sample grows by application of a load to the sample coated with the stress-induced emitter emitting light according to the stress.SELECTED DRAWING: Figure 2

Description

  The present technology relates to a crack tip position detection method. More specifically, the present invention relates to a method for detecting a tip position when a crack generated in a sample propagates by applying a load, and an apparatus to which the method is applied.

  Conventionally, a fracture toughness test by a double cantilever beam (DCB) test has been performed as a method for measuring the adhesive strength of a sample formed by laminating sample pieces made of CFRP (Carbon Fiber Reinforced Plastics) or the like. There is. This DCB test is a test method defined by ASTM D5528-13, ISO15024, ISO25217, JIS K 7086 and the like, and is a test method in which delamination is caused in a sample to measure strength. In these standards, a test method is determined for each delamination mode. For example, in the open type (mode I) test mode, a load that pulls the sample in the direction of rupturing the sample into two sample pieces is applied to the end portion of the sample, and the sample is cracked. The adhesive strength is calculated based on the length when the crack propagates according to the above-mentioned load.

  In order to acquire this crack length, it is necessary to detect the tip position of the growing crack. As a method for detecting the tip position of the crack, for example, a system for detecting the growth of the crack by comparing the surface color of the sample with the background color is used (for example, see Patent Document 1). ). In this system, the shape of the crack is detected by comparing the color of the surface of the sample with the color of the background or the inside of the sample, and the tip position of the crack is detected.

JP, 2016-50937, A

  In the above-mentioned conventional technique, a sample is photographed to generate an image, and hue, brightness, saturation, etc. are compared for each pixel of the generated image, and a region different from the sample surface in the image is acquired to detect cracks. Detect the shape. However, in the above-mentioned conventional technique, since the hue and the like are compared for each pixel, there is a problem that the process of detecting the tip position becomes complicated.

  The present technology has been made in view of the above-mentioned problems, and an object thereof is to simplify detection of a tip position when a crack generated in a sample propagates by applying a load.

  A first aspect of the present technology is, when a crack formed in the sample is developed by applying a load to a sample coated with a stress-stimulated luminescent material that emits light according to stress, the tip position of the developing crack. Is a crack tip position detection method and a detection device that include a tip position detection procedure for detecting the above based on the light emission of the applied stress-stimulated luminescent material. The region at the tip of the crack is the part where the fracture is progressing and the stress is concentrated. The area where the stress is concentrated is detected by the light emission of the stress-stimulated luminescent material. Since the luminescence of the stress-stimulated luminescent material is self-luminous, it has a different hue from the sample surface. Therefore, the light emitting position of the stress-stimulated luminescent material in the sample under test can be easily recognized. It is expected that the detection of the crack tip position will be simplified.

  Further, in the first aspect of the present technology, the stress-stimulated luminescent material may be applied to the surface of the sample on which the crack propagates. In this aspect, it is possible to detect the light emission of the stress-stimulated luminescent material on the surface where the crack propagates on the surface. It is expected to detect the tip position of the crack generated on the surface of the sample.

  Further, in the first aspect of the present technology, the tip position detection procedure may detect the center of the region in the applied stress-stimulated luminescent body in which the light emission has occurred as the tip position. In this aspect, even if the light emitting area of the stress-stimulated luminescent material is a relatively wide area, the center of the light emitting area can be detected as the tip position of the crack.

  Further, in the first aspect of the present technology, the stress-stimulated luminescent material may be applied to a surface of the sample that is orthogonal to the surface in which the crack propagates and is parallel to the direction in which the crack propagates. In this aspect, it is possible to detect the light emission of the stress-stimulated luminescent material on the surface where the crack propagates inside. It is expected to detect the tip position of the crack generated inside the sample.

  Further, in the first aspect of the present technology, the tip position detection procedure may detect a line connecting the centers of the linear regions in the applied stress-stimulated luminescent material in which the light emission has occurred as the tip position. .. In this aspect, it is expected to detect the shape of the tip of the crack generated inside the sample.

  Further, a second aspect of the present technology is that when a crack formed on the sample is developed by applying a load to a sample coated with a stress-stimulated luminescent material that emits light in response to stress, The tip position detection procedure for detecting the tip position based on the light emission of the applied stress-stimulated luminescent material, and the crack before the load is applied to the sample and the crack based on the detected tip position. A crack length detection method comprising a crack growth length detection procedure for detecting a growth length. Since the tip position of the crack is detected by the light emission of the stress-stimulated luminescent material having a different hue from the sample surface, simplification of the crack length detection is expected.

  In addition, a third aspect of the present technology is that when a crack formed on the sample is developed by applying a load to a sample coated with a stress-stimulated luminescent material that emits light in response to stress, The tip position detection procedure for detecting the tip position based on the light emission of the applied stress-stimulated luminescent material, and the crack before the load is applied to the sample and the crack based on the detected tip position. A sample strength measuring method comprising: a crack growth length detecting procedure for detecting a growth length; and a measuring procedure for measuring the strength of the sample based on the detected crack growth length. Since the tip position of the crack is detected by the light emission of the stress-stimulated luminescent material having a hue different from that of the sample surface, simplification of strength measurement is expected.

  The crack tip position detection method according to the present technology has an excellent effect of simplifying the detection of the tip position when a crack generated in a sample propagates by applying a load.

It is a figure showing an example of composition of a sample strength measuring device concerning an embodiment of this art. It is a figure showing an example of composition of a measurement part concerning an embodiment of this art. It is a figure showing an example of composition of a sample concerning an embodiment of this art. It is a figure showing an example of measurement of intensity concerning an embodiment of this art. It is a figure showing an example of detection of a tip position concerning a 1st embodiment of this art. It is a figure which shows an example of the measurement process of the adhesive strength which concerns on embodiment of this technique. It is a figure showing an example of detection of a tip position concerning a 2nd embodiment of this art.

  Next, a mode for carrying out the present technology (hereinafter, referred to as an embodiment) will be described with reference to the drawings. In the following drawings, the same or similar parts are designated by the same or similar reference numerals. However, the drawings are schematic, and the dimensional ratios of the respective parts and the like do not always match the actual ones. Moreover, it is needless to say that the drawings may include portions having different dimensional relationships and ratios.

<1. First Embodiment>
[Structure of sample strength measuring device]
FIG. 1 is a diagram showing a configuration example of a sample strength measuring device according to an embodiment of the present technology. The sample strength measuring device 1 in the figure includes a test device 2, a camera 3, and a measuring unit 4.

  The test apparatus 2 performs a tensile test on the sample 10. The test apparatus 2 performs a test by applying a tensile load to the sample 10 as a load. The test apparatus 2 in the figure applies a vertical tensile load to the sample 10. Further, the test apparatus 2 measures the load due to the load and the displacement of the sample 10 while applying the load, and outputs it to the measuring unit 4. Here, the load corresponds to the force applied to the sample 10 by the tensile load. The test apparatus 2 shown in the figure includes a load cell 21, an actuator 22, and test jigs 23 and 24.

  The test jigs 23 and 24 hold the sample 10. The test jig 23 holds the sample 10 from above, and the test jig 24 holds the sample 10 from below. In these test jigs 23 and 24, a pin (not shown) is passed through a through hole formed in the load-loading blocks 16 and 17 of the sample 10 which will be described later, and the pin is used as a U-shaped holding portion in the same figure. By being fixed, the blocks 16 and 17 for load application are respectively connected. Since the load-bearing blocks 16 and 17 are bonded to the sample 10, the test jigs 23 and 24 can hold the sample 10. Even if the sample 10 is bent during the test by connecting the test jigs 23 and 24 and the load-loading blocks 16 and 17 via the pins, respectively, the direction of the load on the sample 10 (vertical direction) Direction) can be maintained.

  The actuator 22 applies a downward tensile load to the sample 10 via the test jig 24. For example, the actuator 22 can apply a tensile load based on a predetermined tensile speed (displacement speed). As the actuator 22, an actuator driven by hydraulic pressure can be used. The displacement of the sample 10 is measured by a strain gauge (not shown) arranged on the actuator 22 and output to the measuring unit 4.

  The load cell 21 measures a load applied to the sample 10 via the test jig 23. The measured load is output to the measuring unit 4.

  The camera 3 photographs the sample 10. The camera 3 photographs the light emission of the sample 10 and the stress-stimulated luminescent material applied to the sample 10 to generate an image, and outputs the image to the measurement unit 4.

  The measuring unit 4 measures the adhesive strength of the sample 10. The measuring unit 4 detects the crack length by detecting the crack tip position of the sample 10 from the image output from the camera 3. The measuring unit 4 also measures and outputs the adhesive strength based on the load and the displacement and the crack length output from the test apparatus 2. As shown in the figure, the measurement unit 4 is connected to the test apparatus 2 and the camera 3 by signal lines 8 and 9, respectively. The measuring unit 4 can be configured by, for example, a computer that performs image processing.

  The configuration of the sample strength measuring device 1 is not limited to this example. For example, it is possible to arrange two cameras on both sides of the sample 10 to perform photographing. In this case, the tip positions of the cracks on both sides of the sample 10 can be detected, as will be described later with reference to FIG. Further, the camera can be placed above or below the sample 10 or both of them to take an image. In this case, as will be described later with reference to FIG. 7, it is possible to detect the light emission of the stress-stimulated luminescent material on the upper surface and the lower surface of the sample 10.

[Measurement section configuration]
FIG. 2 is a diagram illustrating a configuration example of the measurement unit according to the embodiment of the present technology. The measurement unit 4 in the figure includes a control unit 41, a strength measurement unit 42, a crack tip position detection unit 43, and a crack growth length detection unit 44.

  The control unit 41 controls the test apparatus 2. The control unit 41 can control the start and stop of the tensile load on the test apparatus 2. Further, the control unit 41 controls the entire measuring unit 4.

  The crack tip position detection unit 43 detects the tip position of the crack in the sample 10 based on the image generated by the camera 3. The crack tip position detection unit 43 detects the tip position by performing image processing. Details of the detection of the tip position by the crack tip position detection unit 43 will be described later. The crack tip position detection unit 43 is an example of the crack tip position detection device described in the claims.

  The crack growth length detection unit 44 detects the length of crack propagation based on the tip position detected by the crack tip position detection unit 43. Details of the detection of the crack growth length in the crack growth length detection unit 44 will be described later.

  The strength measuring unit 42 measures the strength of the sample based on the displacement output from the test apparatus 2 and the crack growth length output from the crack growth length detection unit 44 when the load. In addition to the adhesive strength of the sample, this strength corresponds to, for example, the peeling strength of other members formed on the base material, the breaking strength of the sample composed of a single member, and the like. In the figure, the adhesive strength of the sample 10 is measured. The measured intensity is output as the measured intensity of the sample intensity measuring device 1. Details of the measurement of the intensity in the intensity measuring unit 42 will be described later.

[Sample composition]
FIG. 3 is a diagram showing a configuration example of a sample according to the embodiment of the present technology. In the figure, a represents the configuration of the sample 10. The sample 10 is a sample configured by bonding two sample pieces 11 and 12 with an adhesive 13. For the sample pieces 11 and 12, for example, sample pieces made of CFRP can be used. The adhesive strength of this adhesive becomes the measurement target of the sample strength measuring device 1. An initial crack 14 is formed at the left end of the sample 10 in the figure. The initial crack 14 is a region in the sample 10 where the adhesive 13 is not applied. The initial crack 14 can be formed by holding a film or the like when the sample pieces 11 and 12 are bonded. Load-bearing blocks 16 and 17 are bonded to the sample pieces 11 and 12 in which the initial cracks 14 are formed, respectively. The through holes 18 and 19 are formed in the load-bearing blocks 16 and 17, respectively.

  B in the figure shows the case where a tensile load is applied to the sample 10 as a load. The arrows in the figure represent the tensile loads applied to the load-bearing blocks 16 and 17. In the figure, b represents an example in which the adhesive portion of the sample 10 is broken by a tensile load to generate a crack 15. The crack 15 is a crack that has grown from the end of the initial crack 14.

[Measurement of adhesive strength]
FIG. 4 is a diagram showing an example of intensity measurement according to the embodiment of the present technology. The principle of measuring the adhesive strength will be described by taking the sample 10 described in b in FIG. 3 as an example. In the figure, P represents a tensile load. Further, δ represents the displacement at the crack opening of the sample 10. In addition, a represents the crack length. The adhesive strength G of the sample 10 in the figure can be calculated, for example, by the following equation.
G = 3 × P × δ / (2 × b × a)
Here, b represents the width of the sample pieces 11 and 12. The strength measurement unit 42 described in FIG. 2 acquires the displacement δ output from the test apparatus 2 and the load P and the crack length a output from the crack growth length detection unit 44, and the strength is calculated based on the above equation. To calculate. Thereby, the adhesive strength is measured.

  In this way, the adhesive strength can be calculated by detecting the crack length. In order to detect the crack length, it is necessary to detect the tip position of the crack in the sample 10. In the sample strength measuring device 1 described in FIG. 1, a stress-stimulated luminescent material is applied to the sample 10, and the tip position of the crack is detected based on the light emission of the applied stress-stimulated luminescent material. Here, the stress-stimulated luminescent material is one that emits light according to stress. As the stress-stimulated luminescent material, for example, a stress-stimulated luminescent material that emits light due to deformation caused by a mechanical external force is dispersed in a paint base material such as a resin to form a paint. The sample 10 can be easily coated with the paint.

  A known or unknown material can be adopted as the stress-stimulated luminescent material. Known stress-stimulated luminescent materials include, for example, oxides, sulfides, selenides, and tellurium having spinel structure, corundum structure, β-alumina structure, wurtzite structure, or sphalerite structure, and structures in which these coexist. And the like. For example, a silicate having the above structure or a defect control type aluminate is applicable.

In addition, regarding the stress-stimulated luminescent material, if more specific representative examples are given, strontium aluminate containing europium (Eu) ions (hereinafter referred to as SrAl ₂ O ₄ : Eu), LiSrPO ₄ : Eu ²⁺ , Other examples include LiBaPO ₄ : Eu ²⁺ and xSrO.yAl ₂ O ₃ .zMO: Eu ²⁺ . Here, M represents a divalent metal, and x, y, and z each represent a positive integer. Note that M is not limited as long as it is a divalent metal, but Mg, Ca, or Ba is preferable.

Moreover, the following substances can be mentioned as another example. Described together with the emission color. _{xSrO · yAl 2 O 3 · zSiO} 2 ( emission color: _{green-red), BaTiO 3 -CaTiO 3: Pr} ( emission color: red), ZnS: M (M is not intended to be limited as long as it is a divalent metal but, Mn, Ga and Cu and the like are desirable) (emission color:. _{red-yellow), Sr 2 SiO 4: EuDy} ( emission color: _{yellow), SrAl 2 O 4: Eu} ( emission color: green), CaAl ₂ Si ₂ O ₈ : Eu (emission color: blue), Ca ₂ Al ₂ SiO ₇ : Ce (emission color: blue), Ca ₂ MgSi ₂ O ₇ : Ce (emission color: blue), SrAl ₂ O ₄ : Ce (emission). _{blue), CaYAl 3 O 7: Eu} ( emission color: _{blue), SrAl 2 O 4: HoCe} ( emission color: UV), the general formula Sr {1- (2x + 3y + 3z) / 2} Al 2 O 4: xEu 2+ ^, yCr 3+, to ^{zNd 3+} Represented by materials (although, x, y and z are, 0.25~10mol%, preferably 0.5 to 2.0 mol%.) (Emission color: near infrared).

[Detection of tip position]
FIG. 5 is a diagram showing an example of detection of a tip position according to the first embodiment of the present technology. The figure shows the detection of the tip position of the crack by the stress-stimulated luminescent material. In the figure, a represents the sample 10 before the test. The stress-stimulated luminescent material 61 is applied to the side surface of the sample 10. The stress-stimulated luminescent material can also be applied to the side surface of the sample 10 opposite to the paper surface in the figure. The side surface is a surface on which crack initiation and propagation can be observed from the outside. That is, the stress-stimulated luminescent material 61 is applied to the surface of the sample 10 where the crack propagates.

  B in the same figure shows the sample 10 when the crack 15 propagates. Further, b in the same figure is an enlarged view of the region of the tip of the crack 15, and the tip of the crack 15 is represented by a crack tip 71. The stress-stimulated luminescent material 61 emits light as the crack 15 propagates. The light emitting region 72 shown in b in the figure represents the light emitting region of the stress-stimulated luminescent material 61. The tip of the crack is a portion where stress is concentrated and the fracture of the bonded portion of the sample 10 is progressing. Due to this concentration of stress, the stress-stimulated luminescent body 61 around the crack tip 71 emits intense light, and a luminescent area 72 is generated. Note that a relatively small stress is applied to the region near the crack tip 71 of the sample 10. For this reason, weak light emission (not shown) is also generated in the stress-stimulated luminescent material 61 applied to this neighboring region. When detecting the tip of the crack, it is necessary to exclude the light emitting region near the tip of the crack. For example, by comparing the brightness of each area of the image generated by the camera 3 with a predetermined threshold value, the light emission of the stress-stimulated luminescent body 61 based on the weak stress is removed, and the light emitting area 72 shown in the figure is detected. You can

The luminescence of the stress-stimulated luminescent material is self-luminous due to the excited luminescence center, and can be easily observed by the naked eye or detected by image processing. This is because the hue is different from that of the sample 10 and the background. Specifically, a luminescence image of the stress-stimulated luminescent material 61 can be generated by calculating the difference in luminance between the images of the sample 10 before and after the start of the test. This processing is performed by the crack tip position detection unit 43. Further, since the hue of the luminescence of the stress-stimulated luminescent material is different from that of the sample 10 and the like, the accuracy of detecting the luminescent area can be improved. Further, since the stress-stimulated luminescent material containing SrAl ₂ O ₄ : Eu described above has a high response speed of light emission due to stress, by applying this stress-stimulated luminescent material, the detection accuracy of the tip position of the developing crack is further improved. be able to. As described above, the crack tip position detection unit 43 applies the stress emission light applied to the sample 10 at the tip position of the crack 15 that is formed when the crack 15 formed in the sample 10 to which the load is propagated. It detects based on the light emission area | region 71 which is the light emission of the body 61.

When the measurement of crack growth of the sample 10 is also performed, the stress-stimulated luminescent material having a hue different from the ambient light such as illumination is selected to simplify the detection of the crack tip position. It is possible to improve the detection accuracy of the crack tip position under a bright place. For example, when the measurement is performed under indoor illumination with a fluorescent lamp, a stress-stimulated luminescent material having a stress-stimulated luminescent material that emits light of a hue different from the illumination color (visible light, mainly 400 to 700 nm) of the fluorescent lamp is selected. To do. Specifically, the stress-stimulated luminescent material represented by the general formula Sr {1- (2x + 3y + 3z) / 2} Al ₂ O ₄ : xEu ²⁺ , yCr ³⁺ , zNd ³⁺ is a near-infrared light (mainly 700 to Since it contains luminescence of 1200 nm), it can be selected as a stress-stimulated luminescent material having a hue different from the illumination color of a fluorescent lamp. Further, for example, SrAl ₂ O ₄ : Eu exhibiting a green emission color can be selected as a stress-stimulated luminescent material having a hue different from ambient light when the illumination color is blue, yellow, orange or red.

  When the emission brightness of the stress-stimulated luminescent material 61 is saturated with respect to the stress, the light emitting area 72 occupies a relatively wide area. In this case, the effect of saturation of the luminance of the stress-stimulated luminescent material can be reduced by setting the center of the light emitting region 72 at the tip position of the crack.

  When the stress-stimulated luminescent material 61 is applied to the two side surfaces of the sample 10 as described above, the tip positions based on the light emitting region 72 are detected on the respective side surfaces, and the average of these tip positions from the end portion of the sample 10 is detected. The tip position of the crack can be detected by calculating

  The propagation length of the crack 15 can be detected based on the difference between the tip positions of the cracks of the sample 10 before and after applying the load. Specifically, the crack tip position of the sample 10 before applying a load is recorded as an initial position, and the difference between the crack tip position detected by the crack tip position detection unit 43 and the crack tip position is calculated to calculate the growth length. Can be detected. This processing is performed by the crack growth length detection unit 44 described in FIG. Further, when the test is performed on the sample 10 having the initial crack 14 described in FIG. 3, the propagation length can be calculated with the tip position of the initial crack 14 as the initial position. When the adhesive strength is measured by performing a plurality of cycles of applying a load to the same sample 10 and then developing the crack and then releasing the load, the tip position of the crack in the previous cycle is initialized. It is possible to calculate the progress length as a position.

  The stress-stimulated luminescent material 61 needs to be applied in a state that does not affect the measurement of the adhesive strength of the sample 10. Specifically, it is necessary to apply the stress-stimulated luminescent material 61 in such a thickness that the strength thereof is sufficiently smaller than the adhesive strength of the adhesive 13. Further, by applying the adhesive to the area of the sample 13 or the vicinity thereof, the detection accuracy of the tip position can be improved. Further, in order to identify the tip position of the crack, it is necessary to adjust the ratio of the stress-stimulated luminescent material in the stress-stimulated luminescent material 61. Further, it is necessary to optically excite the stress-stimulated luminescent body 61 before starting the test.

[Measurement of adhesive strength]
FIG. 6 is a diagram illustrating an example of an adhesive strength measurement process according to the embodiment of the present technology. First, the strength measuring unit 42 records the crack tip position (step S101). This is a process performed to grasp the tip position of the crack in the initial state. For example, it can be performed by recording the tip position of the initial crack 14 of the sample 10. Next, the tensile load in the test apparatus 2 is started (step S102). This can be performed by the control unit 41 controlling the test apparatus 2. At this time, the displacement speed of the actuator 22 can be controlled to a speed of 1 mm / min, for example. Next, the strength measuring unit 42 detects the load and the displacement (step S103). This can be done by acquiring the load and displacement output from the test apparatus 2.

  Next, the crack tip position detection unit 43 detects the crack tip position (step S104). This is performed by the crack tip position detection unit 43 detecting the light emission of the stress-stimulated luminescent material in the image generated by the camera 3. The image generation by the camera 3 can be performed at a frame rate of 10 fps, for example. Next, the crack growth length detection unit 44 detects the length of the crack (step S105). This can be done by calculating the difference between the crack tip position recorded in step S101 and the tip position detected in step S104. Next, the control unit 41 determines whether or not a predetermined crack length has been reached (step S106). For example, a value of 5 mm can be adopted as the predetermined crack length. As a result, when the predetermined crack length has not been reached (step S106: No), the processing from step S103 is executed again.

  On the other hand, when the predetermined crack length is reached (step S106: Yes), the tensile load in the test apparatus 2 is stopped (step S107). This can be performed by the control unit 41 controlling the test apparatus 2 and releasing the tensile load, as in step S102. At this time, the displacement speed of the actuator 22 can be controlled to the same speed as in step S102. Finally, the strength measuring unit 42 measures the adhesive strength (step S108). This can be performed by the strength measuring unit 42 calculating the adhesive strength based on the crack length and the like.

  The configuration of the sample strength measuring device 1 according to the first embodiment of the present technology is not limited to this example. It can also be applied to other tests, for example, the detection of the adhesive strength in an end notch flexure (ENF) test. It is also possible to apply it to a test of a sample composed of a material other than CFRP. For example, it can also be applied to a test of a sample composed of various polymer materials or a sample composed of aluminum (Al), iron (Fe) and titanium (Ti), and alloys thereof.

  As described above, the crack tip position detection method according to the first embodiment of the present technology detects the tip position based on the light emission of the stress-stimulated luminescent material having a hue different from that of the sample 10 or the background. The detection of the crack tip position can be simplified. It is also possible to improve the detection accuracy of the crack tip position.

<2. Second Embodiment>
In the tip position detecting method of the first embodiment described above, the stress-stimulated luminescent material is applied to the surface of the sample 10 on which the crack propagates. On the other hand, the tip position detection method according to the second embodiment of the present technology is different from that of the first embodiment in that the stress-stimulated luminescent material is applied to the surface of the sample 10 different from the surface on which the crack propagates. different.

[Detection of tip position]
FIG. 7 is a diagram showing an example of detection of the tip position according to the second embodiment of the present technology. The figure shows an example in which the stress-stimulated luminescent material 62 is applied to the upper surface or the lower surface of the sample 10 which is a surface different from the surface on which the crack 15 propagates in the sample 10. Specifically, the stress-stimulated luminescent material 62 is applied to the surface that is orthogonal to the side surface that is the surface on which the crack 15 propagates and that is parallel to the direction in which the crack 15 propagates. In the figure, a is a diagram showing the light emission of the stress-stimulated luminescent material when a crack propagates. At a in the figure, the stress-stimulated luminescent material 62 emits linear light. The light emitting region 73 is obtained by projecting the tip position of the crack 15 inside the sample 10 including the crack tip 71 onto the upper surface of the sample 10.

  As described above, the stress is concentrated in the region of the crack tip 71 of the sample 10, and as a result, the crack propagates. On the other hand, the tip of the crack corresponds to the boundary between the region where the sample pieces 11 and 12 are bonded and the peeled region. The sample pieces 11 and 12 will bend starting from the tip position of the crack. Therefore, stress concentration occurs also on the surfaces of the sample pieces 11 and 12. This stress concentration has a linear shape corresponding to the tip of the crack inside the sample 10. As shown in a in the figure, by applying the stress-stimulated luminescent material 62 to the surface of the sample piece 11 or 12, that is, the upper surface or the lower surface of the sample 10, the concentration of linear stress is detected as the luminescent area 73. be able to. Specifically, the line connecting the centers of the light emitting regions 73 can be set at the tip position of the crack 15.

  Further, by applying the stress-stimulated luminescent material 62 to the upper surface or the lower surface of the sample 10 and detecting the tip position of the crack, it is possible to grasp the state of the growth of the crack inside the sample 10. Thereby, for example, when judging whether the adhesive strength of the adhesive 13 or the rigidity of the sample 10 is uniform, the detection result of the crack growth can be used. In the figure, b is a top view of the sample 10 and shows another example of the light emitting region 73. The stress-stimulated luminescent material 62 is not shown. When the light emitting region 73 has a curved shape in this way, it can be determined that the growth of cracks inside the sample 10 is not uniform.

  In b in the figure, for example, the average position of the distances of the points 74 and 76, which are the end points of the light emitting region 73, from the left end of the sample 10 can be set as the tip position of the crack. Further, for example, the point 75 corresponding to the position where the crack propagates the most can be the tip position of the crack. Further, for example, it is also possible to calculate the average position of the elements forming the curve represented by the light emitting area 73 and use it as the tip position of the crack.

  The configuration of the sample strength measuring device 1 other than this is the same as that of the sample strength measuring device 1 described in the first embodiment of the present technology, and therefore the description thereof is omitted.

  As described above, in the crack tip position detection method according to the second embodiment of the present technology, the surface of the sample 10 that is orthogonal to the surface in which the crack 15 propagates and is parallel to the direction in which the crack 15 propagates. The tip position is detected based on the light emission of the stress-stimulated luminescent material applied to. Thus, the tip position of the crack inside the sample 10 can be detected.

  Finally, the above description of each embodiment is an example of the present technology, and the present technology is not limited to the above embodiment. Therefore, it is needless to say that various modifications other than the above-described embodiments can be made according to the design and the like as long as they do not deviate from the technical idea of the present technology.

  Further, the processing procedure described in the above-described embodiment may be regarded as a method having these series of procedures, or as a program for causing a computer to execute the series of procedures or a recording medium storing the program. You can catch it. As this recording medium, for example, a CD (CompactDisc), a DVD (Digital VersatileDisc), a memory card, or the like can be used.

1 Sample Strength Measuring Device 2 Testing Device 3 Camera 4 Measuring Unit 10 Samples 11 and 12 Sample Piece 13 Adhesive 14 Initial Crack 15 Crack 16 and 17 Load Block 21 Load Cell 22 Actuator 23 and 24 Test Jig 41 Control Unit 42 Strength Measuring Section 43 Crack Tip Position Detecting Section 44 Crack Growth Length Detecting Section 61, 62 Stress Luminescent Material 71 Crack Tip 72, 73 Light Emitting Area

Claims (8)

  When a crack formed in the sample by applying a load to the sample to which the stress-stimulated luminescent material that emits light in accordance with stress is propagated, the tip position of the crack that develops is the coated stress-stimulated luminescent material. A crack tip position detecting method comprising a tip position detecting procedure for detecting based on light emission.   The crack tip position detecting method according to claim 1, wherein the stress-stimulated luminescent material is applied to a surface of the sample where a crack propagates.   3. The crack tip position detecting method according to claim 2, wherein the tip position detecting step detects the center of a region where the light emission has occurred in the applied stress-stimulated luminescent body as the tip position.   The crack tip position detection method according to claim 1, wherein the stress-stimulated luminescent material is applied to a surface of the sample that is orthogonal to a surface in which a crack propagates and is parallel to a direction in which the crack propagates.   5. The crack tip position detecting method according to claim 4, wherein the tip position detecting step detects a line connecting the centers of the linear regions in the applied stress-stimulated luminescent material where the light emission has occurred, as the tip position. When a crack formed in the sample by applying a load to the sample to which the stress-stimulated luminescent material that emits light in accordance with stress is propagated, the tip position of the crack that develops is the coated stress-stimulated luminescent material. A tip position detection procedure for detecting based on light emission,
A crack length detection method comprising: a crack growth length detection procedure for detecting a crack growth length based on the crack before applying the load to the sample and the detected tip position. When a crack formed in the sample by applying a load to the sample to which the stress-stimulated luminescent material that emits light in accordance with stress is propagated, the tip position of the crack that develops is the coated stress-stimulated luminescent material. A tip position detection procedure for detecting based on light emission,
A crack growth length detection procedure for detecting the crack growth length based on the crack and the detected tip position before applying the load to the sample,
A sample strength measuring method, comprising: a measuring procedure for measuring the strength of the sample based on the detected crack growth length.   When a crack formed in the sample by applying a load to the sample to which the stress-stimulated luminescent material that emits light in accordance with stress is propagated, the tip position of the crack that develops is the coated stress-stimulated luminescent material. A crack tip position detection device comprising a tip position detection unit that detects based on light emission.

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