Sheet for enhancing stress luminescence intensity, method for enhancing stress luminescence intensity, and method for measuring stress luminescence intensity

Abstract

Provided are a sheet for enhancing stress luminescence intensity, a method for enhancing stress luminescence intensity, and a method for measuring stress luminescence intensity. The present disclosure pertains to: a sheet for enhancing stress luminescence intensity, which is provided with an aluminum-containing layer and a stress luminescence layer, the stress luminescence layer comprising a coating film of a composition containing a stress luminescence material; a method for enhancing stress luminescence intensity; and a method for measuring stress luminescence intensity. According to the present disclosure, provided are a sheet for enhancing stress luminescence intensity, a method for enhancing stress luminescence intensity, and a method for measuring stress luminescence intensity, with which it is possible to obtain, even in an object comprising an iron-based material, a luminescence intensity comparable to that of an object comprising an aluminum-based material.

Description

Technical Field

[0001] The present invention relates to a sheet for enhancing stress luminescence intensity, and also relates to a method for enhancing stress luminescence intensity and a method for measuring stress luminescence intensity. Background Art

[0002] It is known that a method of visualizing the strain state of an object, etc., is performed by placing a stress luminescent material that emits light by mechanical stimulation of a force (tension, compression, displacement, friction, impact, etc.) applied from the outside on the surface of the object ("Safety Management Monitoring System of Structures Using Stress Luminescent Bodies", November 9, 2009, Industrial Research Institute Magazine; "Visualization of Mechanical Behavior of 6061 Aluminum Alloy During Deformation Using Stress Luminescent Materials", Shimadzu Review, Vol. 79[1·2], 2022, K. Kanamaru, et al.; "InSitu Quantitative Measurement of Stress Distribution in Tensile SpecimenUsing a Detachable Mechanoluminescence Film”,Materials Transactions,Vol.64,2023,p.527-534). When a load is applied to an object, the object deforms and the stress luminescent body also deforms, and the stress luminescent body emits light. Based on the luminescence intensity of the stress luminescent body, the stress generated in the object can be measured. As a stress luminescent material, a composition containing aluminum oxide is known (Japanese Patent Publication No. 2015-67780). Summary of the invention

[0003] As an application field of stress luminescent materials, one can cite the visualization of stress / strain states of metal materials under load. However, in the measurement of stress and strain generated in an object using stress luminescent materials, the luminescence intensity of the stress luminescent body tends to be easily affected by the material of the object. Figure 3 As shown in FIG. 1 , when the object is made of an iron-based material, the luminescence intensity tends to be lower than when the object is made of an aluminum-based material. For the iron-based materials that are generally used, the low luminescence intensity is a problem when considering the wide application of stress luminescent materials. Figure 3 The description is as described later.

[0004] An object of the present disclosure is to provide a stress luminescence intensity enhancing sheet, a method for enhancing stress luminescence intensity, and a method for measuring stress luminescence intensity that can achieve a luminescence intensity comparable to that of an object made of an aluminum-based material even in an object made of an iron-based material.

[0005] A first aspect of the present disclosure is a stress luminescence intensity enhancing sheet including an aluminum-containing layer and a stress luminescence layer, where the stress luminescence layer includes a coating film of a composition containing a stress luminescent material (hereinafter also referred to as a composition for forming a stress luminescence layer).

[0006] A second aspect of the present disclosure is a method for enhancing stress luminescence intensity, which is a method for enhancing the stress luminescence intensity of a stress luminescence layer formed on a first surface of an object, and an aluminum-containing layer is provided between the first surface of the object and the stress luminescence layer.

[0007] The above and other objects, features, aspects, and advantages of the present invention will become apparent from the following detailed description of the present invention understood in association with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic cross-sectional view showing the stress luminescence intensity enhancing sheet of the present embodiment.

[0009] Figure 2 It is a schematic cross-sectional view showing the cross-section when the stress luminescence intensity enhancing sheet is pasted on an object.

[0010] Figure 3 It is a graph showing the stress luminescence intensity of an iron-based material and an aluminum-based material.

[0011] Figure 4 It is a schematic cross-sectional view showing the stress luminescence intensity enhancing sheet of the present embodiment.

[0012] Figure 5 It is a schematic cross-sectional view showing the cross-section when the stress luminescence intensity enhancing sheet is pasted on an object.

[0013] Figure 6 It is a schematic cross-sectional view showing the cross-section when the stress luminescence intensity enhancing sheet is pasted on an object.

[0014] Figure 7 It is a schematic cross-sectional view showing the cross-section when the stress luminescence intensity enhancing sheet is pasted on an object.

[0015] Figure 8 It is a schematic cross-sectional view showing the cross-section when the stress luminescence intensity enhancing sheet is pasted on an object.

[0016] Figure 9 It is a flowchart illustrating the measurement method of the present embodiment.

[0017] Figure 10 This is a diagram showing a structural example of the measuring device used in the measuring method of the present embodiment.

[0018] Figure 11 This is a diagram showing the luminescence intensity measured in the examples and comparative examples.

[0019] Figure 12 This is a diagram showing the luminescence intensity measured in the examples and comparative examples. Detailed Embodiment

[0020] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the same or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

[0021] <Structure of Stress Luminescence Intensity Enhancement Sheet>

[0022] Refer to Figure 1 to describe a structural example of the stress luminescence intensity enhancement sheet of the present embodiment.

[0023] Figure 1 This is a schematic cross-sectional view showing a cross-section in the thickness direction of the stress luminescence intensity enhancement sheet 10 of the present embodiment. The stress luminescence intensity enhancement sheet 10 is adhered to an object (not shown) and is used to measure the stress generated in the object when a force (such as a load, etc.) is applied to the object.

[0024] As Figure 1 shown, the stress luminescence intensity enhancement sheet 10 includes an aluminum-containing layer 11 and a stress luminescence layer 12. The stress luminescence layer 12 contains a coating film of a composition for forming a stress luminescence layer.

[0025] As Figure 2 shown, the stress luminescence layer 12 is joined to the object 100 via the aluminum-containing layer 11. The luminescence intensity of the stress luminescence layer 12 increases in proportion to the magnitude of the applied force. When a force is applied to the object 100, the object 100 deforms equally with the stress luminescence layer 12 and the aluminum-containing layer 11, so that the stress generated in the object 100 due to the deformation can be imaged (visualized) by the luminescence of the stress luminescence layer 12.

[0026] The stress luminescence layer 12 may be disposed in direct contact with the aluminum-containing layer 11. For example, it may also be disposed on the aluminum-containing layer 11 via a substrate or an adhesive layer. The aluminum-containing layer 11 may be disposed in direct contact with the object 100. For example, it may also be disposed on the aluminum-containing layer 11 via an adhesive layer. For example, the aluminum-containing layer 11 can be formed by directly forming a coating film of a composition containing aluminum particles on the object 100, and then the stress luminescence layer 12 can be formed by directly forming a coating film of a composition for forming a stress luminescence layer on the aluminum-containing layer 11, thereby forming the stress luminescence intensity enhancement sheet 10.

[0027] The stress luminescence intensity enhancement sheet according to the present disclosure can achieve a luminescence intensity comparable to that of an object made of an aluminum-based material even in an object made of an iron-based material.

[0028] Figure 3 The luminescence intensity of the stress luminescence material is shown when a stress luminescence sheet [layer structure having a stress luminescence layer / resin substrate / adhesive layer] is adhered to an object made of an iron-based material (SUS430) and an object made of an aluminum-based material (A6061), and a uniaxial tensile test is performed under the same conditions (crosshead speed: 2, 5, 10 mm / min and load up to 1.6 kN). As Figure 3 shown, the aluminum-based material shows a luminescence intensity about three times higher than that of the iron-based material. Even considering that the elastic moduli of A6061 and SUS430 are about 70 GPa and 200 GPa respectively, the difference in the above luminescence intensity is large. It is presumed that there is a desensitizing effect of the iron-based material on the stress luminescence material or a sensitizing effect of the aluminum-based material. Considering that the stress luminescence sheet is formed by means of the adhesive layer and the resin substrate, such a desensitizing effect or sensitizing effect is at least not masked by the total thickness of the adhesive layer and the resin substrate. Therefore, the present inventors have completed a stress luminescence intensity enhancement sheet having an aluminum-containing layer and a stress luminescence layer for the purpose of masking the desensitizing effect derived from the iron-based substrate or obtaining a sensitizing effect due to the material itself. By using aluminum, which is a softer raw material than the iron-based material, it is also possible to follow the deformation of the substrate of the iron-based material.

[0029] The stress luminescence intensity enhancement sheet according to the present disclosure can increase the luminescence intensity of the stress luminescence material used in an object made of an iron-based material to 2.5 times. At this time, the luminescence intensity of the stress luminescence material increases following the increase of stress-strain within the elastic range of SUS430 and shows good consistency even in repeated tests.

[0030] The object 100 can be, for example, an object specified in Japanese Industrial Standard (JIS) Z-2201 "Tensile Test Specimens for Metallic Materials". The iron-based material can be, for example, high-purity iron, steel, stainless steel, etc. As stainless steel, for example, SUS430, etc. can be cited. The aluminum-based material can be, for example, pure aluminum, aluminum alloy. As aluminum alloy, for example, A6061, etc. can be cited.

[0031] The stress luminescence material is a material in which an element serving as a luminescence center is dissolved in the framework of an inorganic crystal (base material). Representative materials include strontium aluminate (SrAl 2 O 4 ) doped with europium. In addition, there are zinc sulfide, barium titanate-calcium, calcium aluminate-yttrium, etc. doped with transition metals or rare earths. In the present embodiment, a well-known material can be used as the stress luminescence material.

[0032] The stress luminescence material is in powder form and can be composed of ceramic particles with a micron-sized particle diameter. In recent years, synthesis of stress luminescence particles with a particle diameter of about 2 - 3 μm has been carried out. By pulverizing the synthesized stress luminescence particles, a stress luminescence material with a small particle diameter can be generated. Particles with a monoclinic crystal structure do not change their crystal structure even when pulverized, so it is possible to suppress aggregation of the particles after pulverization without impairing the stress luminescence ability. For example, by pulverizing stress luminescence particles with a particle diameter of about 2 - 10 μm, a stress luminescence material with a particle diameter of about 1.3 - 4 μm can be generated.

[0033] Pulverization of the stress luminescence material can be carried out using a known pulverization device. However, the stress luminescence material has low water resistance and may deteriorate due to heating, resulting in a reduction in stress luminescence ability. Therefore, it is preferable to use a pulverization device that can cause the particles to collide with each other at high speed for pulverization. The pulverization conditions are not particularly limited and can be set considering the particle diameter and particle size distribution of the stress luminescence material before pulverization, etc.

[0034] The stress luminescence layer 12 can be a coating film of a composition for forming a stress luminescence layer formed in direct contact with the aluminum-containing layer 11, or can also be adhered to the aluminum-containing layer 11 as a stress luminescence sheet described later with the second adhesion layer described later. The thickness of the stress luminescence layer 12 can be, for example, 10 μm or less, and from the viewpoints of luminescence intensity and stress change capture ability, it is preferably 3 μm or more and 7 μm or less.

[0035] The composition for forming a stress luminescence layer may contain a solvent in addition to the stress luminescence material. The solvent may contain a film-forming resin. The solvent may contain additives such as a solvent, a dispersant, a filler, and a thickener as needed. By pulverizing the stress luminescence material in a slurry state dispersed in the solvent, the stress luminescence material and the solvent can be mixed. The pulverization method is not particularly limited, and for example, a roll mill or a ball mill can be used.

[0036] The content of the stress luminescence material in the composition for forming a stress luminescence layer can be appropriately adjusted. For example, relative to the solvent mainly composed of a film-forming resin, the stress luminescence material can be set to 150 PHR (150 parts of stress luminescence material relative to 100 parts of solvent). The content of the stress luminescence material can be, for example, 60% by mass based on the mass of the composition for forming a stress luminescence layer.

[0037] The content of the stress luminescence material in the composition for forming a stress luminescence layer is preferably 20% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more. When the content of the stress luminescence material is less than 20% by mass, the particle interval of the stress luminescence material particles becomes larger, and the stress transmitted to the stress luminescence layer escapes into the solvent, so the stress luminescence ability sometimes tends to decrease.

[0038] When the stress luminescence layer 12 is formed in direct contact with the aluminum-containing layer 11, examples of the method for forming the stress luminescence layer 12 include a method of printing a coating containing a stress luminescent material on the aluminum-containing layer 11 and drying it. Printing of the stress luminescence layer 12 can be performed using, for example, screen printing or inkjet printing.

[0039] The aluminum-containing layer 11 can be, for example, a coating film of a composition containing an aluminum foil and aluminum particles. The thickness of the aluminum foil can be, for example, 1 μm or more and 20 μm or less. The coating film of the composition containing aluminum particles can be, for example, 0.5 μm or more and 10 μm or less. The composition containing aluminum particles can be, for example, an aluminum coating.

[0040] When the aluminum-containing layer 11 is a coating film of a composition containing aluminum particles, the coating film of the composition containing aluminum particles can be formed in direct contact with an object. When the aluminum-containing layer 11 is an aluminum foil, the aluminum foil can be pasted to an object with a first bonding layer described later.

[0041] The shape of the stress luminescence intensity enhancing sheet 10 in plan view (the shape when observed from the thickness direction) can be, for example, rectangular, or can be oblong or square.

[0042] Figure 4 The stress luminescence intensity enhancing sheet 20 shown also has a first bonding layer 13 on the side of the aluminum-containing layer 11 opposite to the stress luminescence layer 12. The stress luminescence intensity enhancing sheet 20 sequentially includes a stress luminescence layer 12, an aluminum-containing layer 11, and a first bonding layer 13. As Figure 5 shown, the stress luminescence intensity enhancing sheet 20 can be pasted to an object 100 with the first bonding layer 13.

[0043] When observing the stress luminescence intensity enhancing sheet 20 from the thickness direction, it is preferable that the entire stress luminescence layer 12 overlaps the first bonding layer 13. Thus, when pasting the stress luminescence intensity enhancing sheet 20 to an object, the entire stress luminescence layer 12 can be joined to the object using the first bonding layer 13. By causing the stress generated in the object to propagate to the entire stress luminescence layer 12, a luminescence pattern reflecting the distribution of the stress generated on the surface of the object can appear.

[0044] The thickness of the first bonding layer can be, for example, 1 μm or more and 35 μm or less. The smaller the thickness of the first bonding layer 13, the smaller the distance between the object and the stress luminescence layer 12, and even a minute stress generated in the object can propagate to the stress luminescence layer 12. Therefore, a change in a minute stress generated on the surface of the object can be imaged.

[0045] The first bonding layer 13 can be, for example, an adhesive layer or an adhesive agent layer. The thickness of the adhesive layer can be, for example, 10 μm or more and 35 μm or less, preferably 5 μm or more and 25 μm or less. The adhesive layer can contain, for example, an acrylic adhesive or a polyurethane-based adhesive, etc., but does not contain nickel. The adhesive agent layer can contain, for example, a cyanoacrylate-based adhesive, etc. The thickness of the adhesive agent layer can be, for example, 1 μm or more and 10 μm or less.

[0046] A release substrate can also be provided on the side of the first bonding layer 13 opposite to the aluminum-containing layer 11 side. The surface of the release substrate has an adhesive force that can be peeled off, and it can be a flexible film configured to be peelable from the first bonding layer 13. As the release substrate, for example, a film formed of a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, a polyolefin-based resin such as polypropylene or polyethylene, a polycarbonate-based resin, a polystyrene-based resin, an acrylic resin, etc. can be used. The release substrate is peeled off and removed when the stress luminescence intensity enhancing sheet 20 is adhered to an object.

[0047] Figure 6 The stress luminescence intensity enhancing sheet 30 shown includes a stress luminescence sheet 16, and the stress luminescence sheet 16 includes a stress luminescence layer 12, a substrate 14, and a second bonding layer 15. The stress luminescence sheet 16 is adhered to the aluminum-containing layer 11 by means of the second bonding layer 15 and adhered to the object 100 by means of the first bonding layer 13. The stress luminescence intensity enhancing sheet 30 sequentially includes a stress luminescence layer 12, a substrate 14, a second bonding layer 15, an aluminum-containing layer 11, and a first bonding layer 13.

[0048] As Figure 7 shown, the stress luminescence intensity enhancing sheet 30 can be formed by adhering the aluminum-containing layer 11 to the object 100 by means of the first bonding layer 13 and then adhering the stress luminescence sheet 16 to the aluminum-containing layer 11 by means of the second bonding layer 15.

[0049] In the stress luminescence intensity enhancing sheet 30, the aluminum-containing layer 11 can be an aluminum foil, or can also be a coating film of a composition containing aluminum particles.

[0050] As Figure 8 shown, the stress luminescence intensity enhancing sheet 30 can also be formed by adhering the stress luminescence sheet 16 to the aluminum-containing layer 11 by means of the second bonding layer 15, and then adhering the aluminum-containing layer 11 to the object 100 by means of the first bonding layer 13.

[0051] The substrate 14 can be, for example, a flexible film. As the flexible film, for example, a film formed of a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, a polyolefin-based resin such as polypropylene or polyethylene, a polycarbonate-based resin, a polystyrene-based resin, an acrylic resin, etc. can be used.

[0052] The stress luminescence sheet 16 can be formed, for example, by forming a second bonding layer 15 on a release substrate, then forming a stress luminescence layer 12 on a base material 14, and then pasting the surface of the second bonding layer 15 opposite to the release substrate on the side of the base material 14 opposite to the stress luminescence layer 12.

[0053] As a method for forming the second bonding layer 15, a method such as printing a coating containing an acrylic adhesive or a polyurethane-based adhesive on the release substrate can be used. For example, screen printing or inkjet printing can be used for printing the second bonding layer 15.

[0054] As a method for forming the stress luminescence layer 12, a method such as printing a composition for forming a stress luminescence layer on the base material 14 can be used. For example, screen printing or inkjet printing can be used for printing the stress luminescence layer 12.

[0055] <Method for enhancing stress luminescence>

[0056] A method for enhancing the stress luminescence intensity of the present embodiment will be described. The method for enhancing the stress luminescence intensity is a method for enhancing the stress luminescence intensity of a stress luminescence layer formed on a first surface of an object, and includes a step of providing an aluminum-containing layer between the object and the stress luminescence layer.

[0057] According to the method for enhancing the stress luminescence intensity of the present disclosure, by using the sheet for enhancing stress luminescence intensity of the present disclosure, even in an object made of an iron-based material, a luminescence intensity comparable to that of an object made of an aluminum-based material can be obtained. For the object, the stress luminescence layer, and the aluminum-containing layer, the description in the above sheet for enhancing stress luminescence intensity is applicable.

[0058] As a method for providing an aluminum-containing layer between the object and the stress luminescence layer, for example, the following methods can be cited. First, it is formed by pasting an aluminum foil to the object by means of a bonding layer, or by directly coating a composition containing aluminum particles on the object. Then, as Figure 7 shown, a stress luminescence sheet sequentially including a coating film of a composition for forming a stress luminescence layer, a base material, and a second bonding layer is pasted on the formed aluminum-containing layer by means of a second bonding layer. Or, it can also be formed by directly printing a coating film of a composition for forming a stress luminescence layer on the formed aluminum-containing layer.

[0059] As another example of the method for providing an aluminum-containing layer between the object and the stress luminescence layer, as Figure 5 and Figure 8 shown, a method of pasting a stress luminescence intensity enhancing sheet 30 including a stress luminescence layer 12, an aluminum-containing layer 11, and a first bonding layer 13 on a first surface of an object 100 with the aluminum-containing layer 11 on the object 100 side by means of the first bonding layer 13 can be cited.

[0060] Next, the method for measuring the stress luminescence intensity will be described. The method for measuring the stress luminescence intensity includes the above-described method for enhancing the stress luminescence intensity. As Figure 9 shown, the method for measuring the stress luminescence intensity may have a stress luminescence intensity enhancement step (S10), a step of irradiating excitation light (S20), a step of extinction (S30), a step of applying a load (S40), a step of photographing stress luminescence (S50), and a step of calculating stress (S60). The stress luminescence intensity enhancement step (S10) is performed by the above-described method for enhancing the stress luminescence intensity.

[0061] Figure 10 FIG. is a diagram showing a structural example of a measuring device 200 used for the method for measuring the stress luminescence intensity. The measuring device 200 can be used to measure the stress when a tensile load is applied to an object 220. A stress luminescence intensity enhancement sheet is pasted on the object 220.

[0062] As Figure 10 shown, the measuring device 200 is configured to include a tensile testing machine 240, a control device 260, a photographing device 270, a light source 230, a driving device 232, a control device 280, and a storage device 290. At least the tensile testing machine 240, the photographing device 270, and the light source 230 in the measuring device 200 are provided in a dark room.

[0063] The tensile testing machine 240 is a device for applying a tensile load to the object 220 to measure mechanical properties such as the tensile strength, yield point, elongation, and shrinkage of the object 220. For example, as the tensile testing machine 240, a precision universal testing machine (product name: Autograph AG-Xplus, manufactured by Shimadzu Corporation) can be used.

[0064] The tensile testing machine 240 has a workbench 241, a crosshead 242, a pair of screws 244, 246, an upper clamp 248, a lower clamp 250, and a load sensor 252. The pair of screws 244, 246 are vertically provided on the workbench 241 so as to be rotatable in a vertical direction. The pair of screws 244, 246 are composed of ball screws.

[0065] The crosshead 242 is connected to each of the screws 244, 246 by a nut (not shown). The crosshead 242 is configured to be movable in the vertical direction along the pair of screws 244, 246. A load mechanism (not shown) for raising and lowering the crosshead 242 is loaded in the workbench 241.

[0066] The upper clamp 248 is connected to the crosshead 242 and clamps the upper end portion of the object 220. The lower clamp 250 is connected to the workbench 241 and clamps the lower end portion of the object 220. The interval L1 between the upper clamp 248 and the lower clamp 250 can be 120 mm. During the tensile test, the tensile testing machine 240, while clamping both end portions of the object 220 by the upper clamp 248 and the lower clamp 250, raises the crosshead 242 according to the control of the control device 260, thereby applying a tensile force to the object 220.

[0067] The load cell 252 is a sensor for detecting the test force that is the tensile load applied to the object 220. The load cell 252 outputs a signal representing the detected test force to the control device 260.

[0068] The control device 260 is communicatively connected to the tensile testing machine 240 and controls the tensile action performed by the tensile testing machine 240. The control device 260 accepts user operations such as setting operations and execution instruction operations of various parameters including the test conditions of the tensile test, and controls the load mechanism according to the accepted user operations. The control device 260 further receives various signals including the output signal of the load cell 252 and the signal representing the displacement amount of the crosshead 242 from the tensile testing machine 240, and analyzes data such as the detected value of the test force.

[0069] The control device 260 includes a processor such as a CPU (Central Processing Unit), memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), an interface circuit for connecting peripheral devices, and a display unit 262. By the processor executing the tensile test program stored in the memory, the above various functions are realized.

[0070] The display unit 262 displays various information based on the signals input to the control device 260. For example, during the execution of the tensile test, the display unit 262 displays the test force detected by the load cell 252. In addition, the display unit displays the displacement amount representing the displacement (stroke) of the crosshead 242.

[0071] The light source 230 is disposed opposite to the object 220 and is configured to irradiate the stress luminescence layer of the stress luminescence intensity enhancement sheet on the object 220 with excitation light. The light source 230 is, for example, a blue LED (Light Emitting Diode). Receiving the excitation light irradiated from the light source 230, the stress luminescence layer of the stress luminescence intensity enhancement sheet transitions to the excited state. The number of the light sources 230 is not limited.

[0072] The driving device 232 supplies power for driving the light source 230 and controls the on / off of the light source 230. The driving device 232 can control the light quantity of the excitation light irradiated from the light source 230, the irradiation time of the excitation light, and the like.

[0073] The photographing device 270 is configured to include at least a specified area of the object 220 in the photographing field of view. The photographing device 270 includes an optical system such as a lens and a photographing element. The photographing element generates a photographed image by converting the light incident from the object 220 through the optical system into an electrical signal.

[0074] The control device 280 controls the photographing operation performed by the photographing device 270 and the driving of the light source 230 performed by the driving device 232. The control device 280 is connected to the control device 260 of the tensile testing machine 240 through the communication line 215. The control device 280 exchanges data with the control device 260 through the communication line 215, whereby the tensile testing machine 240, the photographing device 270, and the light source 230 can be comprehensively controlled. The communication between the control device 280 and the control device 260 can also be achieved through wireless communication. It should be noted that, in the present embodiment, the control device 280 of the light source 230 and the photographing device 270 is separately provided from the control device 260 of the tensile testing machine 240, but the control device 280 and the control device 260 may also be integrated.

[0075] The control device 280 includes a processor such as a CPU, memories such as a ROM and a RAM, an interface circuit for connecting peripheral devices, and a display unit 282. The display unit 282 displays various information based on the signals input to the control device 280. For example, the display unit 282 can display the data input from the control device 260 through the communication line 215 (the test force detected by the load cell 252 and the displacement amount indicating the displacement (stroke) of the crosshead 242, etc.). In addition, the display unit 282 can display an image (luminescence image) of the stress luminescent layer photographed by the photographing device 270. The display unit 282 can display the luminescence image photographed by the photographing device 270 in real time.

[0076] The storage device 290 is a non-volatile storage device that stores a stress measurement program executed by the CPU of the control device 280, the data exchanged between the control device 280 and the control device 260, and the image data photographed by the photographing device 270.

[0077] In the step of irradiating the excitation light (S20), the stress luminescent layer becomes an excited state by irradiating the excitation light from the light source 230 onto the surface of the object 220.

[0078] Next, an extinction process (S30) is performed. In this process (S30), the light source 230 is stopped and the object is put on standby until the luminescence intensity of the excited stress luminescent layer stabilizes.

[0079] Next, a step of applying a load (S40) is performed. In this process (S50), a tensile load is applied to the object 220 by driving the tensile testing machine 240. As the conditions of the tensile test, the tensile speed and the maximum load are set.

[0080] Next, a process of photographing stress luminescence (S50) is performed. In this process (S50), a predetermined area of the object 220 is photographed by the photographing device 270. That is, the luminescence of the stress luminescent layer is photographed using the photographing device 270. The photographing device 270 uses, for example, an industrial camera, and the frame rate is set to 1 fps to photograph the stress luminescent layer.

[0081] Next, a process of calculating stress (S60) is performed. In this process (S60), the stress generated in the object 220 is measured using the luminescence image photographed by the photographing device 270 in the process of photographing stress luminescence (S50).

[0082] Specifically, the image data (moving image data) photographed by the photographing device 270 is intercepted in units of frames. Then, for the luminescence image of one frame, the luminescence intensity within the ROI (Region Of Interest) is calculated. Using the calculated value of the luminescence intensity within the obtained ROI and the standard curve data (a function representing the relationship between the luminescence intensity and the stress) pre-stored in the storage device 290, the stress generated in the ROI is calculated.

[0083] It should be noted that when a plurality of ROIs are set on the surface of the object 220, the stress generated within each ROI is calculated. Then, based on the position information of each ROI and the calculated value of the stress, the stress distribution on the surface of the object 220 is calculated.

[0084] The calculated value of the stress within the ROI is stored in the storage device 290 in association with one frame of the luminescence image. That is, data representing the stress generated in the object 220 due to the tensile load at the timing of obtaining one frame of the luminescence image is saved in the storage device 290. By observing the data at each timing in the obtained order, the temporal change of the stress caused by the tensile load can be evaluated.

[0085] It should be noted that in the above measurement method, a structural example of pasting a stress luminescence intensity enhancement sheet on a part of the object 220 is described. However, it may also be a structure in which stress luminescence intensity enhancement sheets are pasted on multiple parts of the object 220. In this case, after simultaneously irradiating excitation light to multiple stress luminescence intensity enhancement sheets, while applying a load to the object 220, the stress luminescence of the multiple stress luminescence intensity enhancement sheets is photographed. Based on the luminescence intensity of the stress luminescence layer in the multiple stress luminescence intensity enhancement sheets, the stress distribution of multiple parts of the object 220 can be obtained.

[0086] Hereinafter, the present invention will be described in more detail by way of examples.

[0087] [Examples]

[0088] [Tensile test]

[0089] The Figure 10 shown test system was set under darkroom conditions, and test piece objects with stress luminescence intensity enhancement sheets prepared in the examples and comparative examples were set. Then, as an excitation process for accumulating energy in the stress luminescence layer, blue light was irradiated for 60 seconds, and then it was kept in the dark for 120 seconds. Then, the luminescence intensity was recorded at a crosshead speed of 5 mm / min until a load of 1.6 kN (256 MPa) was applied. The test results of each test piece object with a stress luminescence intensity enhancement sheet twice are shown in Figure 11 and 12 .

[0090] [Preparation of composition 1 for forming stress luminescence layer]

[0091] SrAl 2 O 4 -based stress luminescence particles (ML-032, Sakai Chemical Industry Co., Ltd., D50 = 3.3 μm, D90 = 5.2 μm, luminescence wavelength: λ = 520 - 530 nm) were pulverized with a jet mill (D50 = 1.6 μm, D90 = 2.1 μm), and a transparent ink containing a polyurethane resin, a curing agent, and a solvent was mixed therein to prepare composition 1 for forming a stress luminescence layer.

[0092] [Fabrication of stress luminescence sheet 1]

[0093] As a substrate, a commercially available polyester sheet having a peelable adhesive layer (t = 59 μm, adhesive force: 0.25 N / 25 mm: JIS Z0237) on one side was prepared. Composition 1 for forming a stress luminescence layer was screen-printed on the side of the polyester sheet (210 × 297 mm) opposite to the peelable adhesive layer side using a #500 stainless steel mesh, and it was dried to form a stress luminescence layer with a thickness of 5 μm, thereby fabricating a detachable stress luminescence sheet 1.

[0094] <Example 1>

[0095] On one side of a SUS430 test piece (JIS13B shape, thickness 0.5 mm), an aluminum foil (foil made by UACJ, thickness 11 μm) was adhered with an adhesive layer (instant adhesive, Kyowa Denki, CC-33A). The peelable adhesive layer of the stress luminescence sheet 1 was pasted on the aluminum foil to fabricate a test piece of a sheet for enhancing stress luminescence intensity, which successively included the stress luminescence sheet 1 / aluminum foil / adhesive layer / SUS430 test piece. A tensile test was conducted on the fabricated test piece of the sheet for enhancing stress luminescence intensity. The measured luminescence intensity is shown in Figure 11 .

[0096] <Example 2>

[0097] An aluminum coating was applied on one side of a SUS430 test piece (JIS13B shape, thickness 0.5 mm) and dried to form an aluminum coating film (thickness 60 - 90 μm). The peelable adhesive layer of the stress luminescence sheet 1 was pasted on this coating film to fabricate a test piece of a sheet for enhancing stress luminescence intensity, which successively included the stress luminescence sheet 1 / aluminum coating film / SUS430 test piece. A tensile test was conducted on the fabricated test piece of the sheet for enhancing stress luminescence intensity. The measured luminescence intensity is shown in Figure 11 .

[0098] <Comparative Example 1>

[0099] The peelable adhesive layer of the stress luminescence sheet 1 was pasted on one side of a SUS430 test piece (JIS13B shape, thickness 0.5 mm) to fabricate a test piece of a sheet for enhancing stress luminescence intensity, which successively included the stress luminescence sheet 1 / SUS430 test piece. A tensile test was conducted on the fabricated test piece of the sheet for enhancing stress luminescence intensity. The measured luminescence intensity is shown in Figure 11 .

[0100] <Comparative Example 2>

[0101] A conductive aluminum tape with an adhesive layer (3M, AL-25BT, thickness 60 μm, aluminum layer thickness 25 μm, containing Ni) was pasted on one side of a SUS430 test piece (JIS13B shape, thickness 0.5 mm). The peelable adhesive layer of the stress luminescence sheet 1 was pasted on the conductive aluminum tape to fabricate a test piece of a sheet for enhancing stress luminescence intensity, which successively included the stress luminescence sheet 1 / conductive aluminum tape / SUS430 test piece. A tensile test was conducted on the fabricated test piece of the sheet for enhancing stress luminescence intensity. The measured luminescence intensity is shown in Figure 11 .

[0102] As Figure 11 shown, higher luminescence intensities were obtained in Examples 1 and 2 compared with Comparative Examples 1 and 2.

[0103] <Example 3>

[0104] On an aluminum foil (aluminum content 99+%, thickness 25 μm, Nilaco, AL-013223), a composition 1 for forming a stress-luminescent layer was screen-printed using a #500 stainless steel mesh, and it was dried to form a stress-luminescent layer with a thickness of 5 to 8 μm, and a sheet for enhancing luminescence intensity was formed. The aluminum foil side of the sheet for enhancing luminescence intensity was joined to a SUS430 test piece by means of an adhesive layer (instant adhesive, Kyowa Electric Industry Co., Ltd., CC-33A), and a test piece with a sheet for enhancing stress-luminescent intensity having a stress-luminescent layer / aluminum foil / adhesive layer / SUS430 test piece in sequence was fabricated. A tensile test was conducted on the fabricated test piece with a sheet for enhancing stress-luminescent intensity.

[0105] <Comparative Example 3>

[0106] For comparison with Example 3, a tensile test was conducted on a test specimen fabricated in the same manner as in Comparative Example 1, and the obtained results are shown in Figure 12 .

[0107] As Figure 12 shown, a higher luminescence intensity was obtained in Example 3 as compared with Comparative Example 3.

[0108] Those skilled in the art will understand that the above-described multiple exemplary embodiments are specific examples in the following manner.

[0109] (Item 1) A sheet for enhancing stress-luminescent intensity according to one mode, which includes an aluminum-containing layer and a stress-luminescent layer, and the aforementioned stress-luminescent layer includes a coating film of a composition containing a stress-luminescent material.

[0110] (Item 2) In the sheet for enhancing stress-luminescent intensity according to Item 1, the aforementioned aluminum-containing layer is an aluminum foil.

[0111] (Item 3) In the sheet for enhancing stress-luminescent intensity according to Item 2, a first bonding layer is further provided on the side of the aforementioned aluminum-containing layer opposite to the aforementioned stress-luminescent layer.

[0112] (Item 4) In the sheet for enhancing stress-luminescent intensity according to Item 1, the aforementioned aluminum-containing layer is a coating film of a composition containing aluminum particles.

[0113] (Item 5) In the sheet for enhancing stress-luminescent intensity according to any one of Items 2 to 4, it includes a stress-luminescent sheet, and the stress-luminescent sheet includes the aforementioned stress-luminescent layer, a base material, and a second bonding layer in sequence, and the aforementioned stress-luminescent sheet is pasted to the aforementioned aluminum-containing layer by means of the aforementioned second bonding layer.

[0114] (Item 6) In the stress luminescence intensity enhancing sheet according to any one of Items 2 to 4, the stress luminescence layer is formed by directly contacting a coating film of a composition containing the stress luminescent material on the aluminum-containing layer.

[0115] (Item 7) In the stress luminescence intensity enhancing sheet according to Item 3, the first bonding layer is an adhesive layer or a binder layer.

[0116] (Item 8) In the stress luminescence intensity enhancing sheet according to Item 5, the second bonding layer is an adhesive layer or a binder layer.

[0117] (Item 9) Another method for enhancing stress luminescence intensity, which is a method for enhancing the stress luminescence intensity of a stress luminescence layer disposed on an object, includes a step of providing an aluminum-containing layer between the object and the stress luminescence layer.

[0118] (Item 10) In the method for enhancing stress luminescence intensity according to Item 9, the object is an iron-based material.

[0119] (Item 11) In the method for enhancing stress luminescence intensity according to Item 9, the aluminum-containing layer is formed by pasting an aluminum foil on the first surface of the object with a bonding layer, or by coating a composition containing aluminum particles on the object.

[0120] (Item 12) In the method for enhancing stress luminescence intensity according to Item 11, the stress luminescence layer is formed by pasting a stress luminescence sheet including a coating film of a composition containing a stress luminescent material, a substrate, and a second bonding layer in this order on the aluminum-containing layer with the second bonding layer.

[0121] (Item 13) In the method for enhancing stress luminescence intensity according to Item 11, the stress luminescence layer is formed by printing a composition containing a stress luminescent material on the aluminum-containing layer.

[0122] (Item 14) In the method for enhancing stress luminescence intensity according to Item 9, the aluminum-containing layer and the stress luminescence layer are formed by pasting a stress luminescence intensity enhancing sheet including a coating film of a composition containing a stress luminescent material, the aluminum-containing layer, and a first bonding layer on the object with the first bonding layer.

[0123] (Item 15) A method for measuring stress luminescence intensity, which includes the method for enhancing stress luminescence intensity according to Items 9 to 14.

[0124] The embodiments of the present invention have been described, but it should be considered that the embodiments disclosed this time are illustrative in all aspects and not restrictive. The scope of the present invention is represented by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A sheet for enhancing the intensity of stress luminescence, comprising an aluminum-containing layer and a stress luminescence layer, The stress luminescent layer includes a coating film of a composition containing a stress luminescent material.

2. The sheet for enhancing stress luminescence intensity according to claim 1, wherein: The aluminum-containing layer is aluminum foil.

3. The sheet for enhancing stress luminescence intensity according to claim 2, wherein: The aluminum-containing layer further includes a first bonding layer on a side opposite to the stress luminescent layer.

4. The sheet for enhancing stress luminescence intensity according to claim 1, wherein: The aluminum-containing layer is a coating film of a composition containing aluminum particles.

5. The sheet for enhancing the stress luminescence intensity according to claim 2, comprising a stress luminescence sheet, wherein the stress luminescence sheet comprises the stress luminescence layer, a substrate and a second bonding layer in this order, The stress luminescent sheet is bonded to the aluminum-containing layer via the second bonding layer.

6. The sheet for enhancing stress luminescence intensity according to claim 2, wherein: The stress luminescent layer is formed by directly contacting a coating film of a composition containing the stress luminescent material on the aluminum-containing layer.

7. The sheet for enhancing stress luminescence intensity according to claim 3, wherein: The first lamination layer is a pressure-sensitive adhesive layer or an adhesive layer.

8. The sheet for enhancing stress luminescence intensity according to claim 5, wherein: The second lamination layer is a pressure-sensitive adhesive layer or an adhesive layer.

9. A method for enhancing stress luminescence intensity, comprising the step of providing an aluminum-containing layer between the object and the stress luminescence layer.

10. The method for enhancing stress luminescence intensity according to claim 9, wherein: The object is an iron-based material.

11. The method for enhancing stress luminescence intensity according to claim 9, wherein: The aluminum-containing layer is formed by laminating an aluminum foil to the object via an adhesive layer, or by applying a composition containing aluminum particles to the object.

12. The method for enhancing stress luminescence intensity according to claim 11, wherein: The stress luminescent layer is formed by laminating a stress luminescent sheet including a coating film of a composition containing a stress luminescent material, a substrate, and a second laminating layer in this order to the aluminum-containing layer via the second laminating layer.

13. The method for enhancing stress luminescence intensity according to claim 11, wherein: The stress luminescent layer is formed by printing a composition containing a stress luminescent material on the aluminum-containing layer.

14. The method for enhancing stress luminescence intensity according to claim 9, wherein: The aluminum-containing layer and the stress luminescence layer are formed by laminating a coating film including a composition containing a stress luminescence material, the aluminum-containing layer, and a sheet for enhancing stress luminescence intensity of a first laminating layer to the object via the first laminating layer.

15. A method for measuring stress luminescence intensity, comprising the method for enhancing stress luminescence intensity according to claim 9.

Images