JP7420312B2 - Mechanoluminescence measurement method and mechanoluminescence measurement device - Google Patents

Description

The present invention relates to a mechanoluminescence measurement method and a mechanoluminescence measurement device.

2. Description of the Related Art There is a known technique for analyzing the strain of a sample or structure coated with or mixed with a stress-stimulated luminescent material by measuring the strain of the stress-stimulated luminescent material based on the luminescence phenomenon of the stress-stimulated luminescent material. A stress-stimulated luminescent material is a member that emits energy and emits light when its energy state is increased, and when external mechanical force is applied, it emits light in response to stress generated inside. Since there is a correlation between the luminescence intensity (luminance) of the stress-stimulated luminescent material and the amount of strain, it is possible to image the stress-stimulated luminescent material using an imaging device and measure the strain of the stress-stimulated luminescent material from the brightness of the stress-stimulated luminescent material.

For example, Non-Patent Document 1 discloses a stress-stimulated luminescent image measuring device that uses a stress-stimulated coating film sensor as a sensor for detecting deformation in a plastically deformed region of a metal material. In Non-Patent Document 1, a stress-stimulated luminescent film having a thickness of about 120 μm is formed on the surface of a test piece made of an aluminum alloy plate. Then, this test piece is placed in a material testing machine, and a uniaxial tensile test is performed at a constant loading rate. During the tensile test, stress-induced luminescence images are taken using a high-speed camera at a shooting speed (frame rate) of 125 fps (frames per second).

Lee et al., "Structure diagnosis technology using stress-induced luminescence", p. 193-200, NTS Co., Ltd.

According to Non-Patent Document 1, strong stress-induced luminescence related to a PLC (Portevin-Le Chatalier) deformation band is confirmed in a stress-stimulated luminescence image in a plastic deformation region. Furthermore, the stress-stimulated luminescence photographed by a high-speed camera was generated in the upper part of the specimen at the initial stage of the plastic deformation region, and then moved in the axial direction, and the propagation of the PLC band was confirmed.

However, with the measuring device described in Non-Patent Document 1, while strong stress-induced luminescence is observed in response to deformation of the test piece, there is concern that it is difficult to capture minute changes in stress. This is because the thickness of the stress-stimulated luminescent film is 100 μm or more, so the minute stress propagated from the test piece to the stress-stimulated luminescent film is absorbed by the matrix that makes up the stress-stimulated luminescent film, and as a result, the surface of the test piece This is thought to be due to the fact that it is difficult for a light emission pattern that reflects the distribution of microscopic stress that occurs in the process to appear.

The present invention has been made to solve such problems, and its purpose is to provide a mechanoluminescence measurement method and a mechanoluminescence measurement device that enable highly sensitive stress measurement with a simple configuration. .

The mechanoluminescent measuring method according to the first aspect of the present invention includes the steps of forming a mechanoluminescent film having a thickness of 40 μm or less on a predetermined region of the surface of a test piece, and irradiating the mechanoluminescent film with excitation light. and applying a tensile force to the test piece; and photographing at least a predetermined region of the test piece while the tensile force is being applied using a photographing device having a frame rate of 60 fps or less.

The mechanoluminescent measuring device according to the second aspect of the present invention measures stress generated in a test piece when a tensile force is applied. A stress-stimulated luminescent film having a thickness of 40 μm or less is formed in a predetermined area on the surface of the test piece. The mechanoluminescent measuring device includes a testing machine for applying a tensile force to the test piece, a light source for irradiating the mechanoluminescent film with excitation light, and at least a predetermined area of the test piece when the tensile force is applied. and a photographing device that photographs at a frame rate of 60 fps or less.

According to the present invention, highly sensitive stress measurement can be realized with a simple configuration.

3 is a flowchart related to the mechanoluminescent measurement method according to Embodiment 1. FIG. FIG. 2 is a diagram schematically showing a test piece and a stress-stimulated luminescent film. FIG. 2 is a block diagram showing a first configuration example of a mechanoluminescent measuring device used in the measurement step (S20). FIG. 3 is a diagram showing the time course of the test force applied to the test piece. FIG. 2 is a diagram showing an example of a luminescence image photographed by a photographing device. FIG. 3 is a diagram showing the film thickness dependence of the luminescent properties of a stress-stimulated luminescent film. It is a block diagram showing the 2nd example of composition of a stress luminescence measuring device. FIG. 3 is a diagram showing an example of a display image using a luminescence image photographed by a photographing device. FIG. 7 is a diagram illustrating another example of a display image using a luminescence image photographed by a photographing device. 2 is a flowchart for explaining the stress-stimulated luminescent film forming step (S10 in FIG. 1). It is a schematic diagram for demonstrating the process (S12) of applying stress luminescent paint. It is a schematic diagram for demonstrating the process (S12) of applying stress luminescent paint. It is a figure which shows the measurement result of the surface quality of the stress-stimulated luminescent film formed by the stress-stimulated luminescent film formation process (S10). FIG. 9 is a diagram showing an example of a luminescence image photographed by the photographing device (FIG. 9).

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the same or corresponding parts in the figures are denoted by the same reference numerals, and the description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a flowchart of the mechanoluminescent measurement method according to the first embodiment. As shown in FIG. 1, the stress-stimulated luminescent measurement method according to the first embodiment mainly includes a stress-stimulated luminescent film forming step (S10), a measuring step (S20), and a display step (S30).

First, a stress-stimulated luminescent film forming step (S10) is performed. In this step (S10), the stress-stimulated luminescent film 1 is formed on a predetermined region of the surface of the test piece 2. FIG. 2 is a diagram schematically showing the test piece 2 and the stress-stimulated luminescent film 1.

Referring to FIG. 2, test piece 2 is made of a metal material. As the test piece 2, those specified in Japanese Industrial Standards (JIS) Z-2201 "Metallic material tensile test piece" can be used. In this embodiment, a tensile test of a metal material is performed as a strength test of the metal material. In a tensile test, the mechanical properties of a metal material are measured by applying strain to a test piece until it breaks due to tensile force.

The metal material constituting the test piece 2 is, for example, aluminum, and is A1050 (pure aluminum with a purity of 99.50% or more). In the example of FIG. 2, the test piece 2 is a JIS No. 13B plate-shaped test piece, and the total length L = 220 mm, the distance between gauges Lo = 50 mm, the length of the parallel part Lc = 75 mm, the width W = 25 mm, and the parallel part width D = 12.5±0.04 mm, shoulder radius R = 25 mm, and plate thickness t = 1 mm.

The stress-stimulated luminescent film 1 is placed in a predetermined area on the surface of the test piece 2 . The predetermined region is located so as to cover the parallel portion of the test piece 2, and has a rectangular shape with a width of 80 mm and a length of 12.5 mm. The stress-stimulated luminescent film 1 has a thickness of approximately 4 μm (4±0.5 μm). In this specification, the thickness of the stress-stimulated luminescent film refers to the height of the stress-stimulated luminescent film in the direction perpendicular to the surface of the test piece.

The stress-stimulated luminescent film 1 is obtained by molding a stress-stimulated luminescent material alone or in combination with another material (such as a resin). A stress-stimulated luminescent material is a material that emits light when mechanically stimulated by an externally applied force (tension, compression, displacement, friction, impact, etc.).

In the stress-stimulated luminescent film 1, the emission intensity is proportional to strain energy. Moreover, since the stress-stimulated luminescent film 1 is strongly adhered to the surface of the test piece 2, the stress-stimulated luminescent film 1 and the test specimen 2 deform equally. Therefore, the distribution of stress generated on the surface of the test piece 2 due to deformation can be imaged (visualized) by light emission from the stress-stimulated luminescent film 1.

Next, a measurement step (S20) is performed. In this step (S20), the stress generated in the test piece 2 is measured by utilizing the luminescent phenomenon of the stress-stimulated luminescent film 1 when a tensile force is applied to the test piece 2. The luminescence of the stress-stimulated luminescent film 1 can be measured using a stress-stimulated luminescent measuring device 100 shown in FIG.

FIG. 3 is a block diagram showing a first configuration example of the mechanoluminescent measuring device 100 used in the measurement step (S20). Referring to FIG. 3, the stress-stimulated luminescence measuring device 100 includes a tensile tester 4, a control device 6, an imaging device 8, a light source 10, and a drive device 12. At least the tensile tester 4, the photographing device 8, and the light source 10 of the mechanoluminescent measuring device 100 are installed in a dark room.

The tensile tester 4 is a device for applying a tensile force to the test piece 2 and measuring mechanical properties of the test piece 2 such as tensile strength, yield point, elongation, and area of area. In the example of FIG. 3, a precision universal testing machine (product name: Autograph AG-Xplus, manufactured by Shimadzu Corporation) is used as the tensile testing machine 4.

The tensile tester 4 includes a table 40, a crosshead 42, a pair of screw rods 44, 46, an upper grip 48, a lower grip 50, and a load cell 52. A pair of screw rods 44 and 46 are rotatably erected on the table 40 so as to face vertically. The pair of screw rods 44 and 46 are made of ball screws.

The crosshead 42 is connected to each screw rod 44, 46 via a nut (not shown). The crosshead 42 is configured to be movable in the vertical direction along a pair of screw rods 44 and 46. A load mechanism (not shown) for raising and lowering the crosshead 42 is mounted inside the table 40.

The upper gripper 48 is connected to the crosshead 42 and grips the upper end of the test piece 2 . The lower gripper 50 is connected to the table 40 and grips the lower end of the test piece 2. The distance L1 between the upper gripping tool 48 and the lower gripping tool 50 is 120 mm. During a tensile test, the tensile tester 4 lifts the crosshead 42 under the control of the control device 6 while gripping both ends of the test piece 2 with an upper gripper 48 and a lower gripper 50. Apply tension to piece 2.

The load cell 52 is a sensor for detecting a test force, which is a tensile force applied to the test piece 2. The load cell 52 outputs a signal indicating the detected test force to the control device 6.

The control device 6 is communicatively connected to the tensile testing machine 4 and controls the tensile operation by the tensile testing machine 4. The control device 6 receives user operations such as setting operations and execution instruction operations for various parameters including test conditions for a tensile test, and controls the loading mechanism according to the received user operations. The control device 6 further receives various signals including the output signal of the load cell 52 and the signal indicating the displacement amount of the crosshead 42 from the tensile tester 4, and analyzes data such as the detected value of the test force.

The control device 6 includes a processor such as a CPU (Central Processing Unit), a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory), an interface circuit for connecting peripheral devices, and a display section 62. have The various functions described above are realized by the processor executing the tensile test program stored in the memory.

The display unit 62 displays various information based on signals input to the control device 6. For example, the display unit 62 displays the test force detected by the load cell 52 during execution of the tensile test. Further, the display section displays a displacement amount indicating the displacement (stroke) of the crosshead 42.

The light source 10 is arranged to face the test piece 2 and is configured to irradiate the stress-stimulated luminescent film 1 on the test piece 2 with excitation light. The light source 10 is, for example, a blue LED (Light Emitting Diode). Upon receiving excitation light irradiated from the light source 10, the stress-stimulated luminescent film 1 transitions to a light-emitting state. The number of light sources 10 is not limited. For example, a configuration may be adopted in which a plurality of light sources 10 are arranged and excitation light is irradiated toward the test piece 2 from a plurality of directions.

The drive device 12 supplies power for driving the light source 10 and controls turning on/off of the light source 10 . The drive device 12 can control the amount of excitation light emitted from the light source 10, the irradiation time of the excitation light, and the like.

The imaging device 8 is arranged so that at least a predetermined area of the test piece 2 is included in the imaging field of view. The photographing device 8 includes an optical system such as a lens and an image sensor. The image sensor is realized by, for example, a CCD (Charge Coupled Device) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, or the like. The image sensor generates a photographed image by converting light incident from the test piece 2 into an electrical signal via an optical system.

In the example of FIG. 3, a consumer digital video camera (product name: Handycam (registered trademark) HDR-CX670, manufactured by Sony Corporation) is used as the photographing device 8. The photographing device 8 is installed at a position approximately 30 cm away from the test piece 2.

Next, the measurement step (S20) using the mechanoluminescent measuring device 100 (FIG. 3) will be explained.

The measurement step (S20) includes a step of irradiating excitation light (S21), a step of extinguishing it (S22), a step of applying a tensile force (S23), and a step of photographing stress-induced luminescence (S24).

In the step of irradiating excitation light (S21), the surface of the test piece 2 is irradiated with excitation light from the light source 10. By irradiating excitation light onto the stress-stimulated luminescent film 1 arranged in a predetermined region of the test piece 2, the stress-stimulated luminescent film 1 is brought into an excited state. In the step of extinguishing light (S22), the light source 10 is stopped, and the process waits until the emitted light intensity of the excited stress-stimulated luminescent film 1 becomes stable. The irradiation time (excitation time) of the light source 10 was 1 minute, and the standby time (extinction time) after irradiation was 2 minutes.

In the step of applying a tensile force (S23), a tensile force is applied to the test piece 2 by driving the tensile tester 4. The conditions for the tensile test were a tensile speed of 10 mm/min and a maximum load of 1500N.

FIG. 4 is a diagram showing the time course of the test force applied to the test piece 2. FIG. 4 shows the time course of the test force (corresponding to the tensile force) and the stroke (corresponding to the amount of displacement of the crosshead 42). The test force is a value detected by the load cell 52.

As shown in FIG. 4, when application of the test force is started at time 0 (seconds), the stroke increases monotonically according to a preset tensile speed of 10 mm/min.

The test force increases linearly immediately after the start of the test. This region corresponds to an elastic deformation region where the test piece 2 deforms linearly and elastically.

The increase in the test force stopped 4 to 6 seconds after the start of the test, and thereafter the test force remained almost constant. This region corresponds to the plastic deformation region of test piece 2. In the example of FIG. 4, in the plastic deformation region, the test force maintains a value smaller than the maximum load of 1500N as the stroke increases. Then, about 80 (seconds) after the start of the test, the test piece 2 broke.

In the step of photographing stress-induced luminescence (S24), a predetermined region of the test piece 2 is photographed by the photographing device 8. That is, the light emission from the stress-stimulated luminescent film 1 is photographed by the photographing device 8 . In this embodiment, the stress-stimulated luminescent film 1 was photographed by setting the recording mode of a consumer digital video camera to high-quality FH mode, the recording method to AVCHD, and the photographing speed (frame rate) to 60 fps.

In the display step (S30), the image photographed by the photographing device 8 is displayed. FIG. 5 is a diagram showing an example of an image (luminescence image) of the stress-stimulated luminescent film 1 photographed by the photographing device 8. As shown in FIG. The luminescent image shown in FIG. 5 is obtained by cutting out image data (moving image data) taken in frame units under the above-mentioned photographing conditions.

FIG. 5 shows luminescence images taken at a plurality of time points in the time course of the test force shown in FIG. 4. Specifically, FIG. 5(1) is a light emission image near the time of transition from the elastic deformation region to the plastic deformation region (approximately 5 seconds after the start of the test). FIGS. 5(2) to 5(4) are luminescence images at the initial stage of the plastic deformation region (approximately 30 seconds from the start of the test).

The luminescence image shows the distribution of luminescence intensity in a predetermined region of the test piece 2. This emission intensity distribution represents the stress distribution occurring in a predetermined region of the test piece 2. Specifically, a portion with high emission intensity indicates a portion with high stress, and a portion with low emission intensity indicates a portion with low stress. The luminescence images (FIGS. 5 (1) to (4)) at each time point during the tensile test show temporal changes in the stress distribution generated on the surface of the test piece 2 due to the tensile force.

In detail, as shown in FIG. 5(1), when transitioning from the elastic deformation region to the plastic deformation region, an X-shaped luminescent band first appears at the bottom of the parallel part of the specimen 2. . Then, when transitioning to the plastic deformation region, this X-shaped luminescent band starts moving toward the upper end of the test piece 2, as shown in FIG. 5(2).

Thereafter, as shown in FIG. 5(3), a new X-shaped luminescent band appears above the parallel portion of the test piece 2. This new luminescent band starts moving toward the lower end of the test piece 2. These two light emitters are combined near the center of the parallel portion, as shown in FIG. 5(4). Note that the combined luminescent band disappears after that.

According to the luminescence image shown in FIG. 5, when the test piece 2 is pulled at a constant speed, in the plastic deformation region of the test piece 2, stress concentration first occurs near the end of the parallel part of the test piece 2. It is possible to visually observe how this stress concentration moves toward the central portion of the parallel portion of the test piece 2.

It is assumed that the X-shaped luminescent band corresponds to a band-like pattern called a Lüders band that appears on the surface of the test piece 2. This Lüders band is said to be caused by deformation (referred to as "slip") caused by the displacement of the crystals of the metal material.

As described above, according to the mechanoluminescence measurement method according to the first embodiment, a general-purpose photographing device (for example, a consumer video camera) is used to measure the minute stress generated on the surface of the test piece 2 during the tensile test. Changes can be imaged by visible light stress luminescence. That is, highly sensitive stress measurement can be achieved with a simple configuration.

Such an effect is due to the fact that the stress-stimulated luminescent film 1 formed on the surface of the test piece 2 is made thinner than the conventional stress-stimulated luminescent film as described in Non-Patent Document 1. Since the conventional stress-stimulated luminescent film has a film thickness of 100 μm or more, there is a problem in that it is difficult to detect minute changes in stress occurring on the surface of the test piece 2. This is because as the thickness of the stress-stimulated luminescent film 1 increases, the light emitted when force is applied to the test piece 2 comes from the stress generated in the stress-stimulated luminescent film 1. Furthermore, by increasing the thickness of the stress-stimulated luminescent film 1, there is a possibility that the stress-stimulated luminescent film 1 suppresses the force applied to the test piece 2. As a result, it becomes difficult to measure minute stresses occurring in the test piece 2. In the embodiment described above, since the thickness of the stress-stimulated luminescent film 1 is as small as about 4 μm, it is not possible to visualize changes in stress occurring in the test piece 2 in the plastic deformation region using stress-stimulated luminescence, as shown in FIG. can.

Further, the present inventors investigated the relationship between the thickness of the stress-stimulated luminescent film 1 and the luminescence characteristics, and obtained the results shown in FIG. 6. FIG. 6 is a diagram showing the film thickness dependence of the luminescent properties of the stress-stimulated luminescent film 1. The luminescence characteristics shown in FIG. 6 were obtained by the measurement step (S20) using the stress-stimulated luminescence measuring device 100 shown in FIG.

FIG. 6 shows the luminescence characteristics of a stress-stimulated luminescent film with a thickness of 40 μm and the luminescence characteristics of a stress-stimulated luminescent film with a thickness of 5 μm. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the luminescence intensity of the stress-stimulated luminescent film.

In FIG. 6, the luminescent properties of each stress-stimulated luminescent film are shown when the tensile speed in the tensile test was changed in three steps: 2 mm/min, 5 mm/min, and 10 mm/min.

When the excitation light irradiation ends, the stress-stimulated luminescent film emits light and releases energy. The stress-stimulated luminescent film with a thickness of 40 μm has a larger amount of accumulated energy than the stress-stimulated luminescent film with a film thickness of 5 μm, so the luminescence intensity (amount of afterglow) at the time before applying an external force (time 0 seconds) is getting bigger. At this point, the ratio of the amount of afterglow between the film thickness of 5 μm and the film thickness of 40 μm is about 1:8. That is, the ratio of the amount of afterglow almost matches the ratio of the film thickness of the stress-stimulated luminescent film.

Note that in a stress-stimulated luminescent film with a film thickness of 40 μm, the amount of afterglow gradually decreases over time. On the other hand, in the stress-stimulated luminescent film with a film thickness of 5 μm, the amount of afterglow hardly changes over time.

When a tensile force is applied, the luminescence intensity of any stress-stimulated luminescent film reaches a peak at a certain point. This peak represents light emission (stress-induced luminescence) caused by stress generated in the stress-stimulated luminescent film due to a tensile force. The point at which stress-stimulated luminescence occurs depends on the tensile speed. In the example of FIG. 7, as the tensile speed increases, the time point at which stress-stimulated luminescence occurs becomes earlier. Note that, under the same tensile speed, the time point at which the peak occurs is almost the same between the film thickness of 40 μm and the film thickness of 5 μm.

The amount of stress-stimulated luminescence, which is the increase in luminescence intensity due to stress-stimulated luminescence, corresponds to the height of the peak in stress-stimulated luminescence characteristics. The stress luminescence amount can be determined by subtracting the afterglow amount from the total luminescence intensity. Comparing the stress-stimulated luminescence amount (peak height) when the film thickness is 40 μm and the stress-stimulated luminescence amount when the film thickness is 5 μm, the stress-stimulated luminescence amount is smaller when the film thickness is 5 μm. The ratio of stress luminescence amount between a film thickness of 5 μm and a film thickness of 40 μm is approximately 1:2. This stress-induced luminescence amount ratio (1:2) is smaller than the stress-stimulated luminescent film thickness ratio (1:8). According to this, it can be seen that the amount of stress-stimulated luminescence is not greatly influenced by the thickness of the stress-stimulated luminescent film 1. In other words, even if the thickness of the stress-stimulated luminescent film 1 is reduced, the amount of stress-stimulated luminescence that exceeds the rate of decrease in the film thickness can be obtained.

According to the measurement results shown in FIG. 6, as the thickness of the stress-stimulated luminescent film becomes thinner, the amount of stress-stimulated luminescence decreases. On the other hand, as the film thickness becomes thinner, the amount of afterglow, which is the baseline in the luminescence characteristics, becomes smaller, so the ratio of the stress-stimulated luminescence amount to the total luminescence intensity increases. Furthermore, as the film thickness becomes thinner, the change over time in the amount of afterglow becomes smaller, so the peak waveform becomes sharper. As a result, the contrast of the luminescence image is increased, making it possible to measure stress-stimulated luminescence based on minute changes in stress with high sensitivity.

Note that even if the stress-stimulated luminescent film is made thinner, it maintains a high stress-stimulated luminescence amount that is independent of the film thickness ratio. In the example of FIG. 6, it can be determined that a stress-stimulated luminescent film with a thickness of 5 μm is suitable for achieving high measurement sensitivity.

[Embodiment 2]
In Embodiment 2, a second configuration example of the mechanoluminescence measurement apparatus 100 used in the measurement step (S20 in FIG. 1) will be described.

FIG. 7 is a block diagram showing a second configuration example of the mechanoluminescent measuring device 100. The second configuration example shown in FIG. 7 differs from the first configuration example shown in FIG. 3 in that it includes a photographing device 8A instead of the photographing device 8, and that it includes a control device 14. The other configurations are the same as those in FIG. 3, so their explanation will be omitted.

The photographing device 8A is an industrial camera (machine vision camera) and has a higher resolution than the photographing device 8.

The control device 14 controls the photographing operation by the photographing device 8A and the driving of the light source 10 by the driving device 12. The control device 14 is connected to the control device 6 of the tensile testing machine 4 through a communication line 16. The control device 14 can centrally control the tensile tester 4, the imaging device 8A, and the light source 10 by exchanging data with the control device 6 via the communication line 16. Communication between the control device 14 and the control device 6 may be realized by wireless communication.

The control device 14 includes a processor such as a CPU, a memory such as a ROM and a RAM, an interface circuit for connecting peripheral devices, and a display section 142. The above-mentioned measurement step (S20 in FIG. 1) is realized by the processor executing the tensile test program stored in the memory.

Note that in this embodiment, the control device 14 of the light source 10 and the photographing device 8A, and the control device 6 of the tensile tester 4 are provided separately, but the control device 14 and the control device 6 are provided separately. You can.

The display unit 142 displays various information based on signals input to the control device 14. For example, the display unit 142 can display data input from the control device 6 via the communication line 16 (test force detected by the load cell 52, displacement amount indicating the displacement (stroke) of the crosshead 42, etc.). I can do it.

Further, the display unit 142 can display an image (luminescence image) of the stress-stimulated luminescent film 1 photographed by the photographing device 8A. Specifically, the display unit 142 can display in real time a luminescence image photographed by the photographing device 8A. The display unit 142 can further display an image in which the luminescence image photographed by the photographing device 8A and the data related to the tensile test inputted from the control device 6 are superimposed. The display image on the display unit 142 will be described later.

The measurement step (S20) using the mechanoluminescent measuring device 100 shown in FIG. (S23) and a step (S24) of photographing stress-stimulated luminescence.

In the step of irradiating excitation light (S21), the surface of the test piece 2 is irradiated with excitation light from the light source 10. In the step of extinguishing light (S22), the light source 10 is stopped and the light source 10 is kept on standby until the emitted light intensity of the excited stress-stimulated luminescent film 1 becomes stable. The irradiation time (excitation time) of the light source 10 was 1 minute, and the waiting time after irradiation was 2 minutes.

In the step of applying a tensile force (S23), a tensile force is applied to the test piece 2 by driving the tensile tester 4. The conditions for the tensile test were a tensile speed of 10 mm/min and a maximum load of 1500N.

In the step of photographing stress-induced luminescence (S24), a predetermined region of the test piece 2 is photographed by the photographing device 8A. In this embodiment, for example, an industrial camera (product name: VCXU-15M, manufactured by Baumer) is used as the photographing device 8A, and the frame rate is set to 1 fps to photograph the stress-stimulated luminescent film 1. went.

FIG. 8 is a diagram showing an example of a display image using a luminescence image photographed by the photographing device 8A.

As shown in FIG. 8, the displayed image includes time waveform data of the test force by the tensile tester 4. The time waveform data of the test force is based on the detected value of the load cell 52. In FIG. 8, a portion corresponding to the plastic deformation region of the test piece 2 (a portion where the test force is approximately constant) is extracted and shown from the time waveform data of the test force.

In the example in Figure 8, two peaks (Peak1, Peak2) appear continuously in the time waveform of the test force when transitioning from the elastic deformation region to the plastic deformation region (5 to 6 seconds after the start of the test). There is. Then, at the beginning of the plastic deformation region (6 to 27 seconds from the start of the test), a first stable period Plateau1 in which the test force is approximately constant appears in the time waveform of the test force. Following this first stable period Plateau1, a third peak Peak3 appears (approximately 27 seconds after the start of the test). Then, after the third peak Peak3, a second stable period Plateau2 appears (approximately 27 to 60 seconds from the start of the test). After the second stable period Plateau2, the test force gradually decreases, and then the test piece 2 breaks.

In FIG. 8, a plurality of light emission images are further displayed so as to be superimposed on the time waveform data of the test force. The plurality of light emission images are images taken by the photographing device 8A at a plurality of time points of the time waveform of the test force. In the example of FIG. 8, a light emission image is shown superimposed on a characteristic portion of the time waveform of the test force.

Specifically, two light emission images are shown corresponding to two peaks (Peak1, Peak2) that appear when transitioning from an elastic deformation region to a plastic deformation region. In the luminescence image corresponding to the first peak Peak1, X-shaped luminescence bands appear above and below the parallel portion of the test piece 2. In the luminescence image corresponding to the second peak Peak2, each of the two luminescence bands has started moving toward the center of the test piece 2.

Luminescence images corresponding to the first plateau1 and the third peak Peak3 are further shown. According to this, in the first stable period Plateau1, both the two emission bands continue to move. In the luminescence image corresponding to the third peak Peak3 following the first stable period Plateau1, two luminescence bands are combined.

In the second stable period Plateau2 after the third peak Peak3, the entire parallel portion of the test piece 2 is in a state of emitting light. FIG. 8 shows a luminescence image at the time when the test force is at its maximum (approximately 43 seconds after the start of the test).

After the second stable period Plateau2, the test force gradually decreases. In the luminescence image immediately before the test piece 2 breaks (approximately 80 seconds after the start of the test), dotted luminescence (bright spots) appears. Note that bright spots whose moment of light emission cannot be captured appear as dark spots due to extinction. After that, the test piece 2 breaks. According to the luminescence image at the time of breakage, it was observed that the plurality of bright spots described above were connected and led to breakage. Note that the bright spots are presumed to be caused by dimples (dents) that occurred on the surface of the test piece 2 immediately before rupture.

In the example of FIG. 8, the test force time waveform includes three peaks and two stable periods. By displaying the luminescence image in correspondence with the time waveform of the test force, it is possible to know the luminescence state (emission intensity, luminescence pattern, etc.) in each phase when the test piece 2 is deformed. Thereby, the stress distribution of the test piece 2 in each phase can be observed.

Note that the test force changes by about 30 N at the maximum during the three peaks and two stable periods. As shown in FIG. 8, the luminescence image captures the change in stress generated in the test piece 2 due to this change in test force of about 30N. In this way, the stress-stimulated luminescent film 1 makes it possible to measure minute stress changes occurring in the test piece 2 with high sensitivity.

FIG. 9 is a diagram showing another example of a display image using a luminescence image photographed by the photographing device 8A. In the example of FIG. 9, in the luminescence image, pixels whose luminance exceeds a predetermined value are colored. That is, a portion of the predetermined region of the test piece 2 where stress is large is displayed in color. According to this, the visibility of the portion of the test piece 2 where stress concentration occurs can be improved. Furthermore, by measuring the pattern and size of the colored portion, the pattern of stress distribution and the magnitude of stress can be easily detected. As a result, it is possible to improve the user's convenience when analyzing changes in stress occurring in the test piece 2.

As explained above, according to the mechanoluminescence measurement method according to the second embodiment, by configuring the mechanoluminescence measurement device using a high-resolution imaging device, minute amounts generated in the test piece 2 due to tensile force can be detected. Changes in stress can be imaged more precisely.

[Embodiment 3]
In Embodiment 3, the stress-stimulated luminescent film forming step (S10) shown in FIG. 1 will be described.

The method of forming the stress-stimulated luminescent film 1 on the surface of the test piece 2 includes a method of pasting a stress-stimulated luminescent sheet mixed with a stress-stimulated luminescent material on the test piece using an adhesive, and a method of attaching a stress-stimulated luminescent sheet mixed with a stress-stimulated luminescent material to the test piece, and a method of applying a stress-stimulated luminescent material mixed in a spray can. There is a method of spraying and painting the sample.

However, since the stress-stimulated luminescent sheet is made by dispersing a stress-stimulated luminescent material in a resin and cured, there is a concern that the film thickness will inevitably increase. When the thickness of the stress-stimulated luminescent sheet becomes large, the force applied to the stress-stimulated luminescent sheet itself becomes dominant, so the stress of the stress-stimulated luminescent sheet may be measured rather than that of the test piece. Furthermore, since an adhesive layer is interposed between the stress-stimulated luminescent sheet and the sample, there is a concern that the adhesive strength of the adhesive layer may affect the accuracy of controlling the external force applied to the test piece.

On the other hand, with the method of spray painting a stress-stimulated luminescent material, although the thickness of the stress-stimulated luminescent film formed by one spraying is as small as about 20 μm, the film thickness is uneven, so it is necessary to ensure uniformity of the film thickness. In order to do this, it becomes necessary to spray the stress-stimulated luminescent material multiple times to the same location. As a result, there is a concern that the stress-stimulated luminescent film will become thicker. Furthermore, in spray painting, there is a concern that the consumption amount of the stress-stimulated luminescent material increases compared to the amount of stress-stimulated luminescent material applied to the test piece.

In this embodiment, the stress-stimulated luminescent film 1 is formed on the surface of the test piece 2 using a printing technique using a screen plate. FIG. 10 is a flowchart for explaining the stress-stimulated luminescent film forming step (S10 in FIG. 1). As shown in FIG. 10, the stress-stimulated luminescent film forming step (S10) includes a step of generating a stress-stimulated luminescent paint (S11), a step of applying the stress-stimulated luminescent paint (S12), and a step of drying the stress-stimulated luminescent paint (S13). ).

In the step of producing a stress-stimulated luminescent paint (S11), a paint containing a stress-stimulated luminescent material (stimulated luminescent paint) is produced. In this step, first, a stress-stimulated luminescent material is prepared. A stress-stimulated luminescent material is a material in which an element serving as a luminescent center is dissolved in the skeleton of an inorganic crystal (base material), and a typical example is strontium aluminate doped with europium. Other examples include zinc sulfide doped with transition metals or rare earths, barium/calcium titanate, and calcium/yttrium aluminate. Known stress-stimulated luminescent materials can be used.

The stress-stimulated luminescent material is in powder form and is composed of a plurality of ceramic particles. In order to form a uniform stress-stimulated luminescent film with a thickness of several tens of μm, the particle diameter of the stress-stimulated luminescent material is ideally preferably on the order of submicrons.

Here, a typical stress-stimulated luminescent material is composed of ceramic particles having an average particle diameter of about 2 to 3 μm and a particle size distribution in the range of 1 to 10 μm. This is said to be because if a stress-stimulated luminescent material is produced by aiming at a particle size on the submicron order from the beginning, the crystal structure becomes cubic, which does not have stress-stimulated luminescence ability, instead of monoclinic crystal, which has stress-stimulated luminescence ability. There is. However, when the particle size is on the order of microns, it becomes difficult to make the stress-stimulated luminescent film several tens of micrometers thick.

As a result of extensive research into a method for producing mechanoluminescent materials with particle diameters on the submicron order, the present inventors have found that even when particles with mechanoluminescent properties are crushed, the crystal structure of the particles does not change. It was found that the mechanoluminescence ability was not impaired. Therefore, based on this knowledge, the present inventors discovered a step (S111) of making the stress-stimulated luminescent material fine. In this step (S111), particles of the stress-stimulated luminescent material are crushed. The stress-stimulated luminescent material can be pulverized using a known pulverizer.

However, stress-stimulated luminescent materials have low water resistance and may change in quality due to heating, resulting in a decrease in their stress-stimulated luminescent ability. Therefore, it is preferable to use a pulverizer that can pulverize particles to submicron order by colliding particles with each other at high speed. For example, a wet pulverizer (equipment name: Labostar, manufactured by Ashizawa Finetech Co., Ltd.) can be used. This wet-type pulverizer rotates a rotor in a chamber containing bead-shaped grinding media, circulates the sample on the slurry in the chamber, and causes it to collide with the media, thereby pulverizing the object. be.

Alternatively, a pulverizer (equipment name: Nano Jet Miser, manufactured by Aisin Nano Technologies Co., Ltd.) can be used. This pulverizer accelerates particles by forming concentric swirling vortices by high-pressure jet streams inside the mill. Particles can be crushed by collisions between accelerated particles. At this time, the Joule-Thomson effect (temperature lowering effect during free expansion under pressure) can suppress the temperature rise of the material to be crushed.

Note that the pulverization conditions are not particularly limited and may be set in consideration of the particle size and particle size distribution of the stress-stimulated luminescent material before pulverization.

The particle size distribution of the stress-stimulated luminescent material after pulverization was measured. For the measurement, a laser diffraction/scattering particle size distribution measuring device (device name: CILAS 1090 Liquid, manufactured by Cirrus Corporation) was used. The average particle size was calculated from the volume-based particle size distribution obtained by measurement using a particle size distribution measuring device. As a result, the average particle diameter (D50) was 1.6 μm, and the average particle diameter (D90) was 2.1 μm. Note that the average particle diameter (D50) refers to a particle diameter whose cumulative volume is 50% of the total volume in a volume-based particle diameter distribution. The average particle diameter (D90) refers to a particle diameter whose cumulative volume is 90% of the total volume in a volume-based particle diameter distribution.

Furthermore, the specific surface area of the stress-stimulated luminescent material after pulverization was measured by the BET (Brunauer-Emmett-Teller) method. For the measurement, a fully automatic specific surface area measuring device (device name: Macsorb HM model-1200, manufactured by Mountec Co., Ltd.) was used. The specific surface area of the mechanoluminescent material after pulverization was 2.4 m ² /g.

Next, a stress-stimulated luminescent paint is generated by a step (S112) of mixing the crushed stress-stimulated luminescent material and a solvent. The solvent contains a film-forming resin. As the film-forming resin, thermosetting resins, room temperature curable resins, ultraviolet curable resins, radiation curable resins, etc. can be used.

In addition, the solvent may include solvents, dispersants, fillers, thickeners, leveling agents, curing agents, pigments, antifoaming agents, antioxidants, light stabilizers including ultraviolet absorbers, and flame retardants as necessary. Coating additives such as curing catalysts, bactericidal agents, and antimicrobial agents can be included.

In the step (S112), the stress-stimulated luminescent material and the solvent are mixed by crushing the slurry state in which the stress-stimulated luminescent material is dispersed in a solvent. The crushing method is not particularly limited, and for example, a roller mill or a ball mill can be used.

In the step of applying the stress-stimulated luminescent paint (S12), the stress-stimulated luminescent paint is applied to a predetermined area on the surface of the test piece 2. A printing technique using a screen plate can be used to apply the stress-stimulated luminescent paint. FIG. 11 and FIG. 12 are schematic diagrams for explaining the step (S12) of applying the stress-stimulated luminescent paint.

As shown in FIG. 11, the test piece 2 is placed on the pedestal 76. A boss 78 (protrusion) is provided at a corner of the base 76. The screen plate 70 has a two-dimensional mesh structure, and a plurality of through holes 71 are formed in a matrix. The screen plate 70 is stretched with its outer edge held by a frame 72. The screen plate 70 and frame 72 are fixed to a printing frame 74.

A hole is formed in the printing frame 74 at a position facing the boss 78 of the pedestal 76 . By arranging the printing frame 74 so that the boss 78 fits in this hole, the printing frame 74 can be fixed to the pedestal 76. In this state, the screen plate 70 is placed in contact with the surface of the test piece 2.

With the screen plate 70 in contact with the surface of the test piece 2, the stress-stimulated luminescent paint 84 is supplied from the nozzle 86 onto the screen plate 70. A squeegee 82 inclined with respect to the vertical direction is provided above the printing frame 74. The squeegee 82 has a flat plate shape, and its lower end abuts against the screen plate 70 linearly (in the direction perpendicular to the plane of the paper). The squeegee 82 is configured to be movable horizontally (from left to right in the paper) on the screen plate 70 in this state.

By providing a nozzle 86 in front of the squeegee 82 in the traveling direction and moving the nozzle 86 as the squeegee 82 moves, the stress-stimulated luminescent paint 84 can be supplied onto the screen plate 70.

Next, as shown in FIGS. 12A and 12B, the squeegee 82 is moved horizontally on the screen plate 70 while in contact with the screen plate 70. As a result, each through hole 71 of the screen plate 70 is filled with the stress-stimulated luminescent paint 84 (S121).

Furthermore, as shown in FIG. 12(C), by moving the squeegee 82 in the horizontal direction on the screen plate 70 with the squeegee 82 in contact with the screen plate 70, the stress-stimulated luminescent paint 84 filled in each through hole 71 is is transferred onto the surface of the test piece 2 (S122). By repeatedly moving the squeegee 82 on the screen plate 70, the amount of stress-stimulated luminescent paint 84 filled into each through hole 71 can be made uniform. Thereby, the uniformity of the thickness of the stress-stimulated luminescent film 1 can be improved.

Next, as shown in FIG. 12(D), the printing frame 74 is moved above the pedestal 76 to isolate the screen plate 70 from the surface of the test piece 2 (S123). As a result, the stress-stimulated luminescent paint 84 filled in each through hole 71 of the screen plate 70 is removed from the screen plate 70 and transferred onto the surface of the test piece 2. Adjacent stress-stimulated luminescent coatings 84 are bonded to each other by surface tension, so that a stress-stimulated luminescent coating film having a uniform thickness is formed on a predetermined region of the surface of the test piece 2.

In the step of drying the stress-stimulated luminescent coating (S13), the solvent and water in the solvent evaporate during drying, thereby hardening the stress-stimulated luminescent coating. As a result, a thin stress-stimulated luminescent film 1 is formed on the surface of the test piece 2. Drying conditions can be determined depending on the curing temperature of the resin used, etc.

Note that the thickness of the stress-stimulated luminescent coating before drying can be adjusted by changing the thickness and aperture ratio of the screen plate 70. The thickness of the stress-stimulated luminescent film 1 after drying can be adjusted by changing the boiling point, viscosity, etc. of the stress-stimulated luminescent paint, in addition to the thickness and aperture ratio of the screen plate 70.

FIG. 13 is a diagram showing the measurement results of the surface properties of the stress-stimulated luminescent film 1 formed in the stress-stimulated luminescent film forming step (S10) described above. A non-contact three-dimensional shape measuring device (device name: NH-3Ns, manufactured by Mitaka Kohki Co., Ltd.) was used to measure the surface properties of the stress-stimulated luminescent film 1. As a result of the measurement, the thickness of the stress-stimulated luminescent film 1 was 4.0±0.5 μm. In this embodiment, the particle diameter of the stress-stimulated luminescent material contained in the stress-stimulated luminescent paint is reduced to 2 μm or less, and the stress-stimulated luminescent paint is applied to a test piece by printing using a screen plate to form a stress-stimulated luminescent film. By forming this, it was possible to form a thin stress-stimulated luminescent film 1 with excellent smoothness.

FIG. 14 is a diagram showing an example of an image (luminescence image) of the stress-stimulated luminescent film 1 photographed by the photographing device 8A (FIG. 7). The luminescent image in FIG. 14 is an image of the stress-stimulated luminescent film 1 taken by the photographing device 8A when the test piece 2 is elastically deformed.

As shown in FIG. 14, light emission is observed throughout the parallel portion of the test piece 2. This indicates that in the elastic deformation region, the stress distribution in the parallel portion of the test piece 2 is almost uniform. However, although slight, variations in emission intensity are observed. As shown in FIG. 13, the stress-stimulated luminescent film 1 is a thin film and has excellent uniformity in film thickness. Therefore, the magnitude of minute stress generated on the surface of the test piece 2 can be detected.

[Mode]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.

(Section 1) A stress-stimulated luminescence measurement method according to one embodiment includes the steps of forming a stress-stimulated luminescent film having a thickness of 40 μm or less on a predetermined region of the surface of a test piece, and irradiating the stress-stimulated luminescent film with excitation light. The method includes the steps of: applying a tensile force to the test specimen; and photographing at least a predetermined region of the test specimen while the tensile force is applied using a photographing device having a photographing speed (frame rate) of 60 fps or less.

According to the mechanoluminescent measurement method described in Section 1, by forming a thin mechanoluminescent film with a thickness of 40 μm or less on the surface of the test piece, a It is possible to observe minute changes in stress. According to this, highly sensitive stress measurement can be realized with a simple configuration.

(Section 2) In the stress-stimulated luminescent measurement method described in item 1, the step of forming a stress-stimulated luminescent film includes the step of forming a stress-stimulated luminescent film having a thickness of 5 μm or less.

According to the mechanoluminescent measurement method described in Section 2, by setting the thickness of the mechanoluminescent film to 5 μm or less, the contrast of the mechanoluminescent image increases, so the mechanoluminescence based on minute changes in stress can be measured with high sensitivity. It becomes possible to measure by

(Section 3) The mechanoluminescent measurement method described in item 1 or 2 includes the step of detecting the time waveform of the tensile force applied to the test piece, and the step of detecting a luminescent image of the mechanoluminescent film photographed by an imaging device. and a step of displaying. The step of displaying includes the step of superimposing and displaying the luminescence image on the time waveform of the tensile force applied to the test piece.

According to the mechanoluminescence measurement method described in Section 3, an image indicating the luminescence state (emission intensity, luminescence pattern, etc.) is displayed in association with each phase when the specimen is deformed, so that Changes in stress distribution over time can be easily measured.

(Section 4) The mechanoluminescent measuring method described in item 1 or 2 further includes a step of displaying a luminescent image of the mechanoluminescent film photographed by an imaging device. The step of displaying includes a step of coloring and displaying pixels of the luminescence image whose luminescence intensity is equal to or higher than a predetermined value.

According to the mechanoluminescence measurement method described in item 4, it is possible to improve the visibility of the portion of the test piece where stress concentration occurs. Furthermore, by measuring the pattern and size of the colored portion, the pattern of stress distribution and the magnitude of stress can be easily detected.

(Section 5) In the mechanoluminescent measurement method described in items 1 to 4, the step of forming a mechanoluminescent film includes the step of refining the mechanoluminescent material having monoclinic particles; The method includes the steps of mixing the granulated mechanoluminescent material and a solvent, applying the mixture of the mechanoluminescent material and the solvent to the surface of the test piece, and drying the applied mixture.

According to the mechanoluminescent measuring method described in item 5, the fine particles of the mechanoluminescent material maintain a monoclinic crystal structure, and their mechanoluminescent ability is not impaired. Therefore, by using this stress-stimulated luminescent material, a thin stress-stimulated luminescent film having a thickness of 40 μm or less can be formed on the surface of a test piece.

(Section 6) In the mechanoluminescent measurement method described in Section 5, the step of applying the coating includes the step of arranging a plate-like body in which a plurality of through holes are arranged in a mesh pattern on the surface of the test piece; filling the plurality of through-holes with the mixture by applying the mixture to the surface of the specimen; and transferring the mixture to the surface of the test piece.

According to the mechanoluminescent measurement method described in item 6, a highly uniform mechanoluminescent film can be formed on the surface of the test piece.

(Section 7) A mechanoluminescence measuring device according to one embodiment measures stress generated in a test piece when a tensile force is applied. A stress-stimulated luminescent film having a thickness of 40 μm or less is formed in a predetermined area on the surface of the test piece. The mechanoluminescent measuring device includes a testing machine for applying a tensile force to the test piece, a light source for irradiating the mechanoluminescent film with excitation light, and at least a predetermined area of the test piece when the tensile force is applied. and a photographing device that photographs at a frame rate of 60 fps or less.

According to the mechanoluminescent measuring device described in item 7, by forming a thin mechanoluminescent film with a film thickness of 40 μm or less on the surface of the test piece, it is possible to It is possible to observe minute changes in stress. According to this, highly sensitive stress measurement can be realized with a simple configuration.

(Section 8) In the stress-stimulated luminescent measuring device according to item 7, the thickness of the stress-stimulated luminescent film is 5 μm or less.

According to the mechanoluminescent measurement method described in Section 8, by setting the thickness of the mechanoluminescent film to 5 μm or less, the contrast of the mechanoluminescent image increases, so the mechanoluminescence based on minute changes in stress can be measured with high sensitivity. It becomes possible to measure by

Regarding the above-mentioned embodiments and modifications, combinations of the configurations described in the embodiments, including combinations not mentioned in the specification, may be combined as appropriate within the scope of not causing any inconvenience or contradiction. It is scheduled from.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that equivalent meanings and all changes within the scope of the claims are included.

1 Stress-stimulated luminescent film, 2 Test piece, 4 Tensile tester, 6, 14 Control device, 8, 8A Imaging device, 10 Light source, 12 Drive device, 16 Communication line, 40 Table, 42 Cross head, 44, 46 Screw rod, 48 Upper gripping tool, 50 Lower gripping tool, 52 Load cell, 62,142 Display section, 70 Screen plate, 71 Through hole, 72 Frame, 74 Printing frame, 76 Pedestal, 78 Boss, 82 Squeegee, 84 Stress-luminescent paint, 86 Nozzle, 100 Stress luminescence measuring device.

Claims (11)

forming a stress-stimulated luminescent film having a thickness of 40 μm or less on a predetermined region of the surface of the test piece;
irradiating the stress-stimulated luminescent film with excitation light;
applying a tensile force to the specimen;
Photographing at least the predetermined region of the test piece when the tensile force is applied using a photographing device with a frame rate of 60 fps or less ;
detecting a time waveform of the tensile force applied to the test piece;
displaying a luminescent image of the stress-stimulated luminescent film photographed by the photographing device,
The displaying step includes displaying the luminescent image superimposed on the time waveform of the tensile force applied to the test piece,
The stress luminescence measurement method , wherein the luminescence image includes at least a luminescence image corresponding to a time point when the test piece transitions from an elastic deformation region to a plastic deformation region . forming a stress-stimulated luminescent film having a thickness of 40 μm or less on a predetermined region of the surface of the test piece;
irradiating the stress-stimulated luminescent film with excitation light;
applying a tensile force to the specimen;
Photographing at least the predetermined region of the test piece while the tensile force is applied using a photographing device with a frame rate of 60 fps or less ;
detecting a time waveform of the tensile force applied to the test piece;
displaying a luminescent image of the stress-stimulated luminescent film photographed by the photographing device,
The step of displaying includes the step of superimposing and displaying the luminescent image on the time waveform of the tensile force applied to the test piece,
The luminescent image includes at least one luminescent image corresponding to at least one peak in the time waveform of the tensile force . forming a stress-stimulated luminescent film having a thickness of 40 μm or less on a predetermined region of the surface of the test piece;
irradiating the stress-stimulated luminescent film with excitation light;
applying a tensile force to the specimen;
Photographing at least the predetermined region of the test piece when the tensile force is applied using a photographing device with a frame rate of 60 fps or less ;
detecting a time waveform of the tensile force applied to the test piece;
displaying a luminescent image of the stress-stimulated luminescent film photographed by the photographing device,
The displaying step includes displaying the luminescent image superimposed on the time waveform of the tensile force applied to the test piece,
The stress luminescence measurement method , wherein the luminescence images include at least one luminescence image corresponding to at least one stable period in the time waveform of the tensile force . 4. The stress-stimulated luminescence measuring method according to claim 1, wherein the step of forming the stress-stimulated luminescent film includes a step of forming a stress-stimulated luminescent film having a thickness of 5 μm or less . The mechanoluminescence measurement method according to any one of claims 1 to 3 , wherein the step of displaying further includes a step of coloring and displaying pixels whose luminescence intensity is equal to or higher than a predetermined value in the luminescence image. . The step of forming the stress-stimulated luminescent film includes:
refining the stress-stimulated luminescent material having monoclinic particles;
mixing the finely divided stress-stimulated luminescent material and a solvent;
applying a mixture of the mechanoluminescent material and the solvent to the surface of the test piece;
The mechanoluminescent measurement method according to any one of claims 1 to 5 , comprising the step of drying the applied mixture. The applying step includes:
arranging a plate-like body in which a plurality of through holes are arranged in a mesh shape on the surface of the test piece;
filling the plurality of through holes with the mixture by applying the mixture to the plate-like body;
The mechanoluminescent measurement method according to claim 6 , comprising the step of transferring the mixture onto the surface of the test piece. The stress-stimulated luminescent material according to claim 6, wherein the step of refining the stress-stimulated luminescent material includes the step of accommodating the stress-stimulated luminescent material in a chamber together with a grinding medium, and circulating the stress-stimulated luminescent material and the grinding medium within the chamber. Luminescence measurement method . 7. The mechanoluminescent measuring method according to claim 6, wherein the step of reducing the particles includes the step of accommodating the mechanoluminescent material in a mill and forming a concentric swirling vortex by a high-pressure jet stream inside the mill. A mechanoluminescent measuring device for measuring stress generated in a test piece when a tensile force is applied,
A stress-stimulated luminescent film having a film thickness of 40 μm or less is formed on a predetermined region of the surface of the test piece,
a testing machine for applying the tensile force to the test piece;
a light source for irradiating the stress-stimulated luminescent film with excitation light;
an imaging device that photographs at least the predetermined region of the test specimen at a frame rate of 60 fps or less when the tensile force is applied;
a display unit that displays a luminescent image of the stress-stimulated luminescent film taken by the imaging device superimposed on the time waveform of the tensile force applied to the test piece;
The luminescence image includes a luminescence image corresponding to the time point when the test piece transitions from an elastic deformation region to a plastic deformation region, at least one luminescence image corresponding to at least one peak in the time waveform of the tensile force, and the A stress-stimulus luminescence measurement device comprising at least one of at least one luminescence image corresponding to at least one stable period in a time waveform of tensile force . The stress-stimulated luminescent measuring device according to claim 10 , wherein the stress-stimulated luminescent film has a thickness of 5 μm or less.

Images