JP5164086B2 - Method and apparatus for detecting distortion of an object - Google Patents

Description

  The present invention relates to a method and apparatus for detecting distortion of an object using an optical technique. More specifically, the present invention relates to a method for visualizing and detecting a strain distribution of an object using structural color change due to tensile stress, and an apparatus therefor.

  Conventionally, a method using a strain gauge, a method using an optical technique, and a method using a piezoelectric material are known for measuring the strain of an object. Among them, examples of the optical method include a photoelastic method, a photoplastic method, a light interference method, a caustics method, a speckle interference method, a holographic interference method, a moire method, and a lattice method. In particular, the moire method and the lattice method are widely used for strain measurement because they are simple. There is a technique for measuring the amount of deformation of an object using moire fringes due to differences in the amount of secondary electrons generated (see, for example, Patent Document 1). There is also a technique for visualizing strain distribution using a piezoelectric material (see, for example, Patent Document 2).

FIG. 10 is a flowchart for measuring the amount of deformation of an object according to the prior art. Each process will be described.
Step S1010: A model grid is configured by disposing a substance having a secondary electron generation amount different from that of the sample on the sample surface with two or more kinds of linear densities. Such a model grid is formed by vapor deposition and electron beam, lithography, or laser interferometry.
Step S1020: The model grid formed in Step S1010 is irradiated with a particle beam at two or more kinds of line densities. As a result, two or more types of moire fringes due to the difference in the amount of secondary electrons generated are formed.
Step S1030: The deformation amount of the sample is measured using the formed moire fringes. Specifically, the amount of deformation can be obtained by measuring the gap or the angle shift in the moire fringes with different contrasts obtained in step S1020.

  According to the method shown in FIG. 10, a composite model grid is formed by the above process. As a result, it is possible to measure the overall deformation amount and the deformation amount of the minute portion.

FIG. 11 is a schematic diagram of a strain distribution display device according to the prior art.
The strain distribution display device includes an electroluminescence sheet (EL sheet) 1100 and a piezoelectric material 1110. The EL sheet 1100 is sandwiched between the back electrode 1120 and the surface electrode 1130. The piezoelectric material 1110 is sandwiched between the back electrode 1120 and the electrode 1140. Such a strain distribution display device is disposed on the surface of the object 1170 via an adhesive 1150, and the surface electrode 1130 is connected to the surface of the object 1170 by electric wiring 1160.

  When a load is applied to the object 1170 and a strain distribution is generated, a charge corresponding to the strain distribution is generated on the surface of the piezoelectric material 1110 on the EL sheet 1100 side. The generated charges are collected by the back electrode 1120 of the EL sheet 1100 and guided to the EL sheet 1100, and the region where the back electrode 1120 of the EL sheet 1100 is attached emits light. The light emission intensity of the EL sheet 1100 increases in proportion to the magnitude of distortion of the object 1170. As described above, if the strain distribution display device shown in FIG. 11 is used, the strain distribution of the object 1170 can be visualized by the intensity of the emission intensity of the EL sheet 1100.

JP 2000-155104 A JP 2003-302204 A

However, the technique described in Patent Document 1 or the technique using the lattice method needs to previously form a lattice pattern or a fringe pattern (model grid) serving as a marker on the target object surface. A technique for forming such a fine marker on the surface of an object (for example, lithography) is generally expensive, requires a complicated process, and it is difficult to form a large area. Current technology limits the millimeter to centimeter size. In addition, in order to visualize the strain distribution, a special display device such as an optical microscope, a scanning electron microscope, or a laser device is required, which is not simple.
On the other hand, although the technique described in Patent Document 2 can visualize the strain distribution without separately providing a special display device, the strain distribution display device as shown in FIG. 11 is formed in a large area. It is difficult.
Accordingly, an object of the present invention is to provide a method and an apparatus for easily detecting a deformation amount due to distortion of an object over a large area.
It is a further object of the present invention to provide a method and apparatus for easily detecting the amount of deformation due to distortion of an object over a large area by visual observation semi-quantitatively.

A method for detecting distortion of an object according to the present invention is a step of applying a detection film to the object, wherein the detection film is arranged periodically between particles having a first interplanar spacing and between the particles. A step of irradiating the object with light through the detection film using an optical fiber, the light being irradiated perpendicularly to the surface of the object ; The light is white light, and a step of receiving the light reflected by the particles in the detection film using the optical fiber and a spectrophotometer, wherein the object is not distorted. In the case where the light reflected by the particles having the first surface interval is received and the object is distorted, the predetermined relationship is satisfied from the first surface interval according to the distortion. The second surface interval changed to Receiving the light reflected by the particles, moving the light relative to the object, and detecting distortion of the object from the received light, Calculating a strain amount of the object from the second surface interval obtained from the wavelength of the reflected light and the first surface interval, and visualizing the strain amount and / or strain distribution. This achieves the above object.

The particles may be selected from the group consisting of polystyrene particles, PMMA particles and silica particles.
The elastic body may be silicone rubber or artificial rubber.

  In the light receiving step, when the object is distorted, the difference ΔD between the first surface distance and the second surface distance is expressed by the relationship | (λ2−λ1) /2n|≧0.1. Λ1 is the wavelength of the light reflected by the particles having the first face spacing, and λ2 is reflected by the particles having the second face spacing. The wavelength of the light may be n, and n may be a refractive index of the detection film.

The object may be selected from the group consisting of metals, plastics, composite materials and plastic ceramics.
The predetermined relationship may be a relationship in which a tensile change rate in the longitudinal direction of the object is proportional to a change amount from the first surface interval.

  The first inter-surface distance D1 is designed to be 300 / n <D1 (nm) ≦ 400 / n with respect to the tensile strain of the object, or 200 / with respect to the compressive strain of the object. n ≦ D1 (nm) <300 / n, where n may be the refractive index of the detection film.

The first inter-surface distance D1 is designed to be 400 / n (nm) with respect to the tensile strain of the object, or 200 / n (nm) with respect to the compressive strain of the object. Where n may be the refractive index of the detection film.

The spectrophotometer may be a reflective spectrophotometer.

An apparatus for detecting strain of an object to which a detection film according to the present invention is applied includes a particle having a first surface interval, and an elastic body that fills a gap between the particles, the detection film being periodically arranged. Including a light source and an optical fiber that irradiates light on the surface of the object through the detection film, wherein the light is white light, and an optical system in the detection film through the optical fiber. A light receiving means for receiving the light reflected by the particles, and when the object is not distorted, receives the light reflected by the particles having the first spacing and A spectrophotometer that receives the light reflected by the particles having a second interplanar spacing changed so as to satisfy a predetermined relationship from the first interplanar spacing according to the strain when distortion occurs. And a light receiving means including the light relative to the object And a control means for controlling the operation of the optical system, the operation of the light receiving means, and the operation of the movement means, wherein the control means is configured such that the light is perpendicular to the surface of the object. And controls the operation of the optical system so that the data on the first surface interval is stored in advance and the data on the wavelength of the reflected light received by the light receiving means is stored. calculating a storage unit, on the basis of the stored in the storage unit the data relating to the first lattice spacing and the data relating to the second surface spacing, the strain amount and / or strain distribution occurring on the object And a display means for displaying the strain amount and / or strain distribution, thereby achieving the above object.

The particles may be selected from the group consisting of polystyrene particles, PMMA particles and silica particles.
The elastic body may be silicone rubber or artificial rubber.

  In the light receiving means, when the object is distorted, a difference ΔD between the first surface distance and the second surface distance is a relationship | (λ2−λ1) /2n|≧0.1. Where λ1 is the wavelength of the light reflected by the particles having the first spacing and λ2 is reflected by the particles having the second spacing. The wavelength of light, and n may be the refractive index of the detection film.

The object may be selected from the group consisting of metals, plastics, composite materials and plastic ceramics.
The predetermined relationship may be a relationship in which a tensile change rate in the longitudinal direction of the object is proportional to a change amount from the first surface interval.

The spectrophotometer may be a reflection type spectrometer.

The method according to the present invention is simple because it is only necessary to apply to the object a detection film that includes periodically arranged particles having the first interplanar spacing and an elastic body that fills the gaps between the particles. In addition, such a detection film can be easily manufactured in a large area and can be applied over a wide range of objects. When the object is distorted, the light reflected by the particles having the second surface spacing changed according to the distortion is received. A strain distribution can be detected based on the reflected light. In particular, when the reflected light has a wavelength in the visible light region, the strain distribution can be visually detected as a structural color change of the detection film. It is also possible to determine the strain amount distribution semi-quantitatively from the detected structural color.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart illustrating a method for detecting distortion of an object according to the present invention.
FIG. 2 is a schematic diagram illustrating the principle of detecting distortion of an object according to the present invention.

  A state 200 indicates a state before the stress is applied to the object (initial length L) 220, and a state 210 indicates a state after the stress is applied to the object 220. Using these states 200 and 210, each step will be described.

  Step S110: The detection film 230 is applied to the object 220. Here, the detection film 230 includes particles 240 having a first inter-surface distance D1 and elastic bodies 250 that fill gaps between the particles 240, which are periodically arranged.

  Such particles 240 are also called colloidal particles, and are selected from the group consisting of polystyrene particles, PMMA particles (polymethylmethacrylate particles) and silica particles, for example. Moreover, the composite particle which combined these materials may be sufficient. The composite particles are configured by combining two or more different materials (materials). For example, one material is encapsulated with the other material to form one particle, Means that one material penetrates into the other material to form one particle, or different hemispherical materials combine to form one particle.

The first surface interval D1 is a distance where light (for example, visible light) satisfies the Bragg reflection condition. In detail,
Relationship D1 = λ1 / 2n (1)
Meet. Here, λ1 is the wavelength of the light reflected by the particles 240 having the first interplanar distance D1, and n is the refractive index of the detection film 230. It should be noted that such relationship (1) holds when the incident angle of the incident light with respect to the particles is vertical. As will be described later, when the strain is visually detected semi-quantitatively, λ1 is 400 ≦ λ1 (nm) ≦ 800, that is, the first inter-surface distance D1 (nm) is 200 / n ≦. The detection film 230 is designed so that D1 (nm) ≦ 400 / n. By designing in this way, the structural color in the initial state before compressive stress or tensile stress is applied to the object 220 can be visually observed.

  When a tensile stress is applied to the object 220, the detection film 230 is preferably designed so that the first surface distance D1 (nm) satisfies 300 / n <D1 (nm) ≦ 400 / n. . More preferably, the detection film 230 is designed so that the first inter-surface distance D1 is D1 (nm) = 400 / n. By designing in this way, it is possible to maintain a wide detection range of the strain amount of the object 220 due to the tensile stress detected visually.

Similarly, when compressive stress is applied to the object 220, the detection film 230 is preferably set so that the first inter-surface distance D1 (nm) is 200 / n ≦ D1 (nm) <300 / n. Designed. More preferably, the detection film 230 is designed so that the first inter-surface distance D1 is D1 (nm) = 200 / n. By designing in this way, it is possible to maintain a wide detection range of the strain amount of the object 220 due to the compressive stress detected visually. In this specification, it should be noted that the values 200 / n, 300 / n, and 400 / n of the first interplanar spacing D1 (nm) each include a range of about ± 10 nm.

  The elastic body 250 may be silicone rubber or artificial rubber. The artificial rubber can be, for example, a polydimethyl silicone elastomer. Such a detection film 230 can be manufactured using, for example, the technique described in Japanese Patent Application No. 2004-204109 filed earlier. Briefly summarized, a monodisperse polystyrene particle (PS) suspension is prepared, the suspension is cast on a substrate to obtain a colloidal crystal, and then a liquid elastic material is poured into the elastic material between the colloidal crystal particles. Manufactured by filling the body. According to the object of the present invention and this technique, the detection film 230 can be applied from several tens of centimeters to a metric size, and thus can be easily measured in a large area as compared with the conventional case.

  Here, the object 220 capable of detecting a change due to strain may be arbitrary as long as the detection film 230 is applicable, but is preferably selected from the group consisting of metal, plastic, composite material, and plastic ceramic. For example, specific examples of the object 220 include polyester and polyvinyl chloride, but are not limited thereto. The thickness of the object 220 may be arbitrary as long as the detection film 230 is applicable.

  As described above, when the first inter-surface distance D1 is in the range of 200 / n ≦ D (nm) ≦ 400 / n, the initial structural color of the applied detection film 230 (that is, the object is strain-deformed). Indicating the previous state) is observed. It is desirable to visually confirm the observed structural color. In this case, the structural color obtained by observation is preferably determined with reference to the color index of the detection film. Here, the color index is obtained by associating a color generated by intentionally applying strain to a detection film made of the same detection film material with a distortion amount. By using the color index in this way, it is possible to facilitate the semi-quantitative calculation of the amount of distortion due to the structural color change.

  When the first inter-surface distance D1 is 400 / n <D1 (nm) or D1 (nm) <200 / n, the initial structural color of the detection film 230 is visually observed. Can not. In this case, the first surface distance D1 may be determined in advance using a spectrum meter such as a reflection spectrum spectrometer. Data obtained in this way may be recorded. As a matter of course, if the value of the first surface distance D1 is known in advance (that is, when the detection film 230 having a known structural color is used), the structural color of the detection film 230 is visually confirmed, and the spectrometer It is not necessary to determine the first surface interval D1 using

  2 shows a case where stress is applied to the object 220 after the detection film 230 is applied to the object 220, but the structural color of the detection film 230 to be applied in advance is recorded as data. Alternatively, the detection film 230 may be applied after applying stress to the object 220 if it is confirmed visually.

Step S120: The object 220 is irradiated with light through the detection film 230. The light can be white light, for example, using a light source such as an optical fiber. Preferably, the light is incident so as to be perpendicular to the object 220. Thereby, the received light intensity can be improved. The detection intensity decreases as the angle of the light with respect to the object 220 becomes lower than 90 ° (vertical). This is because the intensity of the detected spectrum is reduced and / or a peak shift of the spectrum occurs.

Step S130: The light (reflected light) reflected by the particles 240 in the detection film 230 is received. The reflected light may be received directly by visual observation, or a spectrum meter such as a reflection spectrum spectrometer may be used. Further, a digital camera, a CCD camera, an optical microscope, or a combination thereof may be used. Here, the reception of the reflected light includes determining the structural color of the detection film 230 using a color index when the structural color is detected visually. In the case of detecting a structural color with higher accuracy, it includes acquiring spectral data or the like using a spectrum meter or the like. The spectrometer may be an ultraviolet / visible / near infrared spectrometer.

  When the object 220 is not distorted, the reflected light is received by the particles 240 having the first inter-surface distance D1. The wavelength of the reflected light in this case is the same as the wavelength of the light reflected by the particle 240 in the state 200 of FIG. Thereby, it can be determined that the object 220 is not deformed by distortion.

Reference is again made to FIG. A state 210 indicates a case where the object 220 is distorted. When the object 220 is distorted, the light reflected by the particles 240 having the second surface distance D2 changed so as to satisfy the predetermined relationship from the first surface distance D1 according to the strain is received. It is assumed that the overall length in the longitudinal direction of the object 220 is extended from the initial length L by L + ΔL due to the stress applied to the object 220. Due to the distortion of the object 220, the surface interval of the particles 240 changes from D1 to D2. The changed second surface distance D2 also satisfies the Bragg reflection condition. That is,
Relationship D2 = λ2 / 2n (2)
Meet. Here, λ2 is the wavelength of the light reflected by the particles 240 having the second inter-surface distance D2, and n is the refractive index of the detection film 230. It should be noted that like the relationship (1), such a relationship (2) holds when the incident angle of incident light on the particle is vertical. The predetermined relationship between the change in the surface spacing of the particles 240 and the change in the overall length of the object 220 is that the tensile change rate in the longitudinal direction of the object 220 (ie, the direction of the overall length L) is the amount of change in the surface spacing. A relationship proportional to ΔD (that is, | D2−D1 |) is satisfied.

Considering the above, in order to detect the structural color change of the detection film 230 caused by the distortion of the object 220 using a spectrum meter or the like, the first surface distance D1 and the second surface distance of the detection film 230 are used. What is D2?
Relation | D2-D1 | ≧ 0.1, that is, relation | (λ2-λ1) /2n|≧0.1 (3)
As long as The peak shift amount of the Bragg reflection caused by the difference in surface spacing can correspond to the wavelength resolution of a standard device such as a spectrometer. In addition, if a distribution is seen in the structural color, it can be confirmed that a strain distribution is generated in the object 220.

FIG. 3 is a graph showing the relationship between the surface spacing and the structural color.
In general, when 200 / n ≦ D2 (nm) ≦ 400 / n is satisfied, the reflected light has a wavelength in the visible light region, and a change due to strain of the detection film 230 can be detected as a structural color by visual observation. In the graph, n represents the average refractive index of the detection film 230, and n = 1.5 (a model of cubic close-packed particles) was used. If the second surface interval D2 is in the range of 130 nm to 270 nm, it can be seen that the reflected light has a wavelength in the visible light region.

Reference is again made to FIG.
Step S140: The distortion of the object 220 is detected from the light (reflected light) received in Step 130.
In step 130, the structural color after the change of the detection film 230 is determined using the color index, and the structural color of the detection film 230 before the distortion change of the object 220 is determined by the color index, or the structure color is determined in advance. When the detection film 230 having a known color is used, the distortion amount of the object 220 is calculated semi-quantitatively from the distortion amount value indicated by the color index.

More specifically, the first surface distance D1 is in the range of 200 / n ≦ D1 (nm) ≦ 400 / n, and the second surface distance D2 after the change is also 200 / n ≦ D2 (nm). ) If it is within the range of 400 / n, the amount of distortion can be determined semi-quantitatively by the color index. Further, when the first inter-surface distance D1 (nm) = 400 / n, the amount of strain due to a tensile stress of about 200 / n (= ΔD) nm at the maximum can be visually determined semi-quantitatively. Since strain due to tensile stress exceeding 200 / n (= ΔD) nm or strain due to compressive stress cannot be visually observed, step 130 may be performed again using a spectrum meter or the like. Similarly, when the first inter-surface distance D1 (nm) = 200 / n, the strain amount due to the compressive stress of about 200 / n (= ΔD) nm at the maximum can be visually determined semi-quantitatively. . Since strain due to compressive stress exceeding 200 / n (= ΔD) nm or strain due to tensile stress cannot be observed visually, step 130 may be performed again using a spectrum meter or the like.

  On the other hand, when a spectrum meter is used to receive reflected light in step S130, the amount of distortion of the object is quantitatively calculated based on the obtained spectrum data. Specifically, based on FIG. 3, the second surface distance D2 is obtained from the wavelength of the reflected light. Next, since the tensile change rate in the longitudinal direction of the object 220 (that is, the direction of the overall length L) is proportional to the amount of change ΔD (that is, | D2−D1 |) of the surface interval, the change of the object 220 is changed. The amount ΔL is obtained. As a result, the amount of distortion of the object 220 is calculated. Note that the obtained calculation result may be visualized as a strain distribution of the object 220 using a display device or the like. At this time, the strain amount and strain distribution may be calculated using a control means such as a central processing unit.

  It should be noted that detecting the distortion of the object 220 includes detecting that the object 220 is not distorted. Specifically, when there is no change in the color index, the amount of distortion of the object 220 is calculated as 0, and it is detected that the object 220 is not distorted. Further, when the change amount ΔL of the object 220 is 0 by the spectrum meter, it is detected that the object 220 is not distorted.

  The method for detecting the distortion of the object of the present invention has been described above with reference to FIG. Note that step S120 may further include a step of moving light relative to the object 220. In this case, the light may be fixed and the object 220 may be moved, or the object 220 may be fixed and the light may be moved. Thereby, it is possible to detect the strain distribution and the strain change amount of the object 220 over a wide range.

Next, an apparatus for detecting distortion of an object according to the present invention will be described.
FIG. 4 is a schematic diagram of an apparatus for detecting distortion of an object according to the present invention.
The apparatus 400 detects the distortion of the sample 410 formed of the object 220 to which the detection film 230 described with reference to FIG. 2 is applied. The apparatus 400 includes an optical system 420 that irradiates light onto the surface of the object 220 through the detection film 230, and a light receiving unit 450 that receives light reflected by the particles 240 in the detection film 230.

  The optical system 420 includes a light source 430 and an optical fiber 440 such as a fiber probe. The light source 430 emits white light. The optical fiber 440 causes the light of the light source 430 to enter the sample 410. At this time, the light from the optical fiber 440 is preferably incident so as to be perpendicular to the surface of the sample 410. Thereby, the detection intensity can be improved.

The light receiving means 450 can be, for example, a spectral spectrometer such as a reflective spectral spectrometer, an optical microscope, a digital camera, a CCD camera, or a combination thereof. The light receiving means 450 receives the light reflected by the particles 240 in the detection film 230 via the optical fiber 440. When the object 220 is not distorted, the light receiving unit 450 receives the light reflected by the particles 240 having the first surface distance D1 described with reference to FIG. On the other hand, when the object 220 is distorted, the light reflected by the particles 240 having the second inter-surface distance D <b> 2 changed according to the distortion of the object 220 is received.

  When the light receiving means 450 is a spectrospectrometer, the received light can be visualized as spectrum data. When the light receiving means 450 is a digital camera, the measurement range can be visualized as image data. If spectral data or image data obtained by the detection film 230 before deformation due to distortion of the object 220 is acquired in advance, the distortion of the object 220 can be detected by comparing with the data after detection.

  The apparatus 400 may further include a moving unit 460 that moves light from the optical system 420 relative to the sample 410, and a control unit 470 that controls operations of the optical system 430, the light receiving unit 450, and the moving unit 460. .

  The moving means 460 may move the sample 410 while fixing the light from the optical system 420, or may move the light from the optical system 420 while fixing the sample 410. The movement by the moving means 460 may be performed manually or automatically by the control unit 470.

  The control unit 470 may include a storage unit 480 that stores data obtained by the light receiving unit 450 and a calculation unit 490 that performs calculation using the data stored in the storage unit 480.

  The storage unit 480 may be a memory, for example. In addition to the obtained data, the storage unit 480 previously stores spectral data of the detection film 230 having various first surface distances D1 and / or tensile changes in the longitudinal direction of the object 220 by the various detection films 230. The relationship between the rate and the change amount ΔD of the surface interval can be stored. The calculation unit 490 can be, for example, a central processing unit (CPU). The calculation unit 490 calculates a strain amount and / or a strain distribution based on the data stored in the storage unit 480. The control unit 470 may further include display means such as a display, and may visualize the calculation result.

  The control unit 470 also controls the intensity of light emitted from the optical system 420, the wavelength of the light, the light diameter, the timing, etc., and the light receiving means 450 receives the light reflected by the sample 410 and receives the received light. It is possible to control so that the data based on the data is transmitted to the storage unit and the moving unit 460 moves the light from the optical system 420 relative to the sample 410.

Next, the operation of the apparatus 400 will be described.
The control unit 470 controls the optical system 420 to emit light toward the portion of the sample 410 to be measured. The light emitted from the light source 430 is incident on the sample 410 via the optical fiber 440. The light (reflected light) reflected by the particles 240 in the detection film 230 is received again by the light receiving means 450 through the optical fiber 440. The light receiving unit 450 transmits the obtained data to the storage unit 480.

  The control unit 470 controls the moving unit 460 to move the light from the optical system 420 relative to the sample 410 so that the light from the optical system 420 enters a place to be further measured. The subsequent operations are the same as the above-described series of operations, and are therefore omitted. Thereafter, the light receiving means 450 obtains all the data to be measured, and the data is stored in the storage unit 480.

  The calculation unit 490 calculates the strain amount and / or strain distribution based on the data stored in the storage unit 480. In detail, since it is the same as that of step S140 demonstrated with reference to FIG. 1, it abbreviate | omits.

  The control unit 470 can visualize the obtained result as a numerical value and / or a two-dimensional mapping image.

  The apparatus 400 according to the present invention can be effective when the structural color change of the detection film 230 cannot be visually detected, and can detect the distortion of the object 220 to which the arbitrary detection film 230 is applied with high accuracy.

  The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

The relationship between the wavelength change of reflected light (peak shift amount) and the strain change rate of the object was investigated. A vinyl chloride resin (PVC, VSS-HS-220S, Sumitomo Bakelite Co., Ltd.) was used as the object 220 (FIG. 2), and a detection film 230 (FIG. 2) was applied on the vinyl chloride resin to prepare a sample. Here, the area of the polyvinyl chloride substrate to which the detection film 230 was applied was 350 mm ² , and the thickness of the vinyl chloride resin was 0.5 mm, which was transparent. Polystyrene particles (average particle size 202 nm) were used as the particles 240 (FIG. 2) of the detection film 230, and polydimethyl silicone elastomer was used as the elastic body 250 (FIG. 2).
When the sample immediately after production was irradiated with white light, the detection film 230 showed a red structural color. As a result of measurement using a spectroscopic device, the wavelength of reflected light was 665 nm. Thereby, it turned out that the 1st surface distance D1 (FIG. 2) of a polystyrene particle is about 222 nm.

  Next, tensile stress was applied at a rate of 0.1 mm / min while the sample was heated to 90 ° C. and held. A tensile stress was applied to the sample using a stretcher. Each time the sample was extended by a certain amount, the reflection spectrum was measured, and the relationship between the wavelength change of reflected light (peak shift amount) and the elongation of the object was examined. The measurement was performed 8 times in total, including the measurement before applying the tensile stress. A reflection spectroscopic device (USB2000 Miniature Fiber Optic Spectrometer, Ocean Optics, US) was used for the microspectroscopic spectrum measurement.

  FIG. 5 is a graph showing the relationship between (A) microspectroscopy spectrum and (B) peak shift amount and sample elongation according to Example 1.

  FIG. 5A shows only the first five measurement results among the eight measurement results in order to avoid complication of the graph. It was confirmed that the wavelength of the reflected light shifts to the lower wavelength side as the tensile stress application time of the vinyl chloride resin of the sample becomes longer (that is, the sample extends). The relationship between the peak shift amount and the elongation percentage of the sample was determined from this microspectroscopic spectrum. The elongation percentage of the sample was obtained from the value indicated by the uniaxial stage. This value corresponds to obtaining the total length L (FIG. 2) of the sample before the tensile stress and the total length L + ΔL (FIG. 2) at each point after the tensile stress.

From FIG. 5B, it was found that the peak shift amount of the reflected light wavelength and the elongation rate of the vinyl chloride resin satisfy a proportional relationship. This is because the peak shift of the wavelength of the reflected light depends on the surface distance D of the particles 240 (FIG. 2) in the detection film 230 (FIG. 2), and thus the amount of change ΔD (| D2-D1 of the surface distance). |) Is equal to the elongation percentage of the vinyl chloride resin. Accordingly, the amount of strain deformation (plastic deformation amount) of the object can be easily obtained from the change in the structural color change of the detection film 230. As described above, from FIG. 5, the elongation rate (ΔL / L) of the detection film 230 and the change amount ΔD of the inter-surface spacing are
Relation ΔD = K (ΔL / L) (4)
It turns out that it satisfies. Here, K is a coefficient specific to the sample. In the case of the sample detection film 230 in Example 1, K≈1.5 (nm /%).

  Therefore, if the relationship between the elongation percentage of the sample and the peak shift amount when the various detection films 230 are applied is known, the structure color change (that is, the peak shift amount) of the detection film 230 is semi-quantitatively visually. It can be seen that the amount of change (elongation) of the sample can be known. In addition, when the peak shift amount is detected using a spectrophotometer, the amount of change (elongation rate) of the sample can be known quantitatively.

  Next, using the results of FIG. 5, the amount of change in the object when the detection film 230 of Example 1 was applied to various objects was measured.

FIG. 6 is a schematic diagram of an experiment according to Example 2 and a photograph of a digital camera.
A polyester (mylar) film was used as the object 220 (FIG. 2), and the detection film 230 (FIG. 2) was applied on the polyester film to prepare a sample 500. Here, the area of the polyester film to which the detection film 230 was applied was 450 mm ² , and the thickness of the polyester film was 25 μm and was transparent. Since the detection film 230 is the same as that of the first embodiment, the description thereof is omitted.

  When the sample 600 immediately after production (ie, before applying stress) was irradiated with white light, the detection film 230 showed a red structural color. As a result of measurement using a spectroscopic device, the wavelength of reflected light was 615 nm. In the above formula (1), when n = 1.5, it was found that the first interplanar spacing D1 (FIG. 2) of the polystyrene particles was 205 nm. Next, after a cut was made in the sample 600, a tensile stress was applied in the longitudinal direction (indicated by an arrow) of the sample 600 (also referred to simply as plastic deformation in this specification). After plastic deformation, the sample 600 was irradiated with white light, and the sample 600 was visually observed and photographed using a digital camera.

  As shown in the digital camera photograph of FIG. 6, the region 610 was a region where tensile stress was concentrated and deformed. The region 620 shows the same red structural color as that of the sample 600 immediately after fabrication, and no distortion or deformation due to tensile stress was observed. A region 630 is in the vicinity of the region 610 and has a yellow to green structural color, and strain and deformation due to tensile stress were confirmed.

  Next, in order to investigate the region 610 of the sample 600 in more detail, microspectroscopy was performed. The microspectroscopic measurement was performed using the same apparatus as in Example 1.

  FIG. 7 is a diagram showing (A) a CCD camera photograph and (B) a microspectroscopic spectrum of a sample according to Example 2.

In FIG. 7A, the vicinity of the region 610 in FIG. 6 was magnified 50 times using an optical microscope and photographed with a CCD camera. In the CCD camera photograph of FIG. 7A, from the upper right to the lower left, changes in the structural color of the detection film 23 are confirmed from red (near spot 1), yellow (near spot 2), and green (near spot 3). It was.
Next, in order to quantitatively determine the amount of distortion deformation, the reflection spectral spectrum at each of the spots 1 to 3 was measured using a reflection spectrometer.

The spectra 1, 2 and 3 in FIG. 7B are the spectral spectra of the spots 1, 2 and 3, respectively. The wavelengths of reflected light from the spectra 1, 2 and 3 were 615 nm, 580 nm and 560 nm, respectively. The area of spot 1 was the same as the wavelength of the reflected light immediately after sample preparation. From this, the second surface distance D2 _s1 in the spot 1 is the same as the first surface distance D1 before applying the tensile stress (that is, D2 _s1 = D1 = 205 nm), and the polyester film is distorted and deformed. I found out. From the wavelength of the reflected light of the spot 2, it was found that the second interplanar distance D2 _s2 in the spot 2 was about 193 nm. As a result, the change amount ΔD _s2 of the interplanar spacing was about 12 nm. Similarly, from the wavelength of the reflected light of the spot 3, the second interplanar distance D2 _s3 in the spot 3 was 187 nm, and the variation ΔD _s3 of the interplanar distance was about 18 nm. When the above equation (4) is applied to the values of the obtained change amounts ΔD _s2 and ΔD _{s3 of} the interplanar spacing, the elongation rates with respect to the spot 1 are about 8% and about 13%, respectively.

  In the case of the microscopic light used in this example, the image was magnified 50 times, and the spectrum was measured through an optical fiber having a diameter of 200 μm. Therefore, a spot having a diameter of 4 μm on the sample is measured. Thus, the mapping image of the deformation area could be visualized as a structural color image with a spatial resolution of 5 μm or less.

  FIG. 8 is a diagram showing (A) an experimental schematic diagram, (B) a digital camera photograph, and (C) a microspectroscopic spectrum according to Example 3.

A sample 800 was prepared by using a polyvinyl chloride substrate as the object 220 (FIG. 2) and applying the detection film 230 (FIG. 2) on the polyvinyl chloride substrate. Here, the area of the polyvinyl chloride substrate to which the detection film 230 is applied is about 400 mm ² , and the thickness of the polyvinyl chloride substrate is 0.
It was 5 mm and was black. Since the detection film 230 is the same as that of the first embodiment, the description thereof is omitted.

  When the sample 800 immediately after production was irradiated with white light, the detection film 230 showed a red structural color. As a result of measurement using a spectroscopic device, the wavelength of reflected light was 630 nm. Thereby, it turned out that the 1st surface distance D1 (FIG. 2) of a polystyrene particle is 210 nm. Next, as shown in the left diagram of FIG. 8A, the sample 800 was heated to a temperature of 150 ° C., and a tensile stress was applied at a rate of about 1 mm / min in the longitudinal direction (indicated by an arrow). Using the same stretcher as in Example 1, a tensile stress was applied until the elongation of the polyvinyl chloride substrate reached 3 mm, and the sample 800 was deformed. This temperature should just be more than the softening point temperature of a polystyrene particle and a polyvinyl chloride board | substrate. The left figure of FIG. 8 (B) shows a digital camera photograph immediately before the temperature rise and the tensile stress are applied. The structural color was red and was confirmed to be uniform.

  After plastic deformation, the sample 800 was cooled to room temperature. As shown in the right figure of FIG. 8 (A), it was confirmed visually that the constricted portion of the sample 800 was distorted. Here, the region i indicates a region that is considered to have a large amount of strain deformation, and the region ii indicates a region that is considered to have little strain deformation amount. 8B shows a digital camera photograph after plastic deformation. A change in the structural color was confirmed at a position corresponding to the region i in the right diagram in FIG. 8A (indicated by a circle in the right diagram in FIG. 8B). The structural color was yellow to green.

  In the same manner as in Example 2, microspectroscopy was performed for examining in detail the region i of the sample 800 and a specific spot in the region ii. FIG. 8 (C) Photo i is a photograph taken with a CCD camera, with the area i magnified 50 times using an optical microscope. Similarly, a photograph ii in FIG. 8C is a photograph obtained by enlarging the region ii by 50 times using an optical microscope and photographing with a CCD camera. The other measurement conditions of the imaging microspectroscopic light are the same as those in the second embodiment.

The structural color of the photograph i in FIG. 8C shows a clearer green color than the structural color in the region i on the right side of FIG. On the other hand, the structural color of the photo ii in FIG. 8C was the same red color as the structural color of the right region ii in FIG. The spectra i and ii in FIG. 8C show the spectra at specific spots in the region i and the region ii, respectively, and the wavelengths of the reflected light were 545 nm and 630 nm, respectively. Region ii was almost the same as the wavelength of the reflected light immediately after sample preparation (ie, before plastic deformation). From this, the second surface distance D2 _sii in the region ii is
It was the same as the first inter-surface distance D1 (FIG. 1) before plastic deformation, and it was found that the polyvinyl chloride substrate was not strain-deformed. On the other hand, it was found from the wavelength of the reflected light in the region i that the second inter-surface distance D2 _si at a specific spot in the region i is about 182 nm. The change amount ΔD _{si of the} inter-surface spacing is about 28 nm, and when this value is applied to the above equation (4), it was found that the elongation rate of the region ii with respect to the region i is about 19%.

  Note that the heating temperature can be set higher by appropriately selecting the elements of the detection film 230 (FIG. 2) (particles 240 (FIG. 2) and elastic body 250 (FIG. 2)). Such a temperature may be a temperature at which the particles 240 and the elastic body 250 are not thermally decomposed. In Example 3, strain detection was performed after plastic deformation and the sample 800 was cooled to room temperature. However, strain detection may be performed while maintaining the temperature.

  From Example 2 and Example 3, regardless of whether the strain deformation amount of the entire object is in the order of μm or mm, using the method of the present invention, a local and wide-range strain distribution of the object can be obtained. Can be detected. In addition, since light only needs to be reflected by particles in the detection film, it is possible to detect distortion of an object having an arbitrary color including colorless and transparent.

FIG. 9 is a schematic diagram of an experiment according to Example 4, and a diagram showing a microspectroscopic spectrum.
The manufacture of the sample 900 is the same as that in Example 3, and thus the description thereof is omitted. After the sample 900 was cut, tensile stress was applied in the longitudinal direction of the sample 900 (indicated by an arrow) while the temperature was raised. Since it is the same as that of Example 2 except having applied the tensile stress on the same temperature conditions as Example 3, description is abbreviate | omitted.

  The microspectroscopic measurement was performed on the region 910 where the tensile stress was concentrated as shown in the experimental schematic diagram of FIG. The inset in FIG. 9 is a photograph taken with a CCD camera, with the area 910 magnified 50 times with an optical microscope. The structural colors of regions A, B and C were green, yellow and red, respectively.

Next, FIG. 9 shows the result of measuring the reflection spectrum at each of the spots A to C using a reflection type spectroscopic device in order to quantitatively determine the strain deformation amount. The wavelengths of reflected light from the spectra A, B, and C were 565 nm, 590 nm, and 630 nm, respectively. The area of the spot C was the same as the wavelength of the reflected light immediately after the preparation of the sample. From this, the second interplanar distance D2 _sC in the spot C is the same as the first interplanar distance D1 (= 210 nm) before applying the tensile stress, and the polyvinyl chloride substrate is not strain-deformed. I understood. From the wavelength of the reflected light of the spot B, it was found that the second interplanar distance D2 _sB in the spot B was 197 nm. The amount of change ΔD _{sB in the interplanar} spacing was 13 nm. When this value was applied to the above equation (4), the elongation percentage of the spot B with respect to the spot C was about 9%. Similarly, from the wavelength of the reflected light from the spot A, it was found that the second interplanar distance D _sA at the spot A was 188 nm. The amount of change ΔD _{sA in the interplanar} spacing was 22 nm. When this value was applied to the above equation (4), the elongation percentage of the spot A with respect to the spot C was about 15%.

  Similar to Example 2, it was found that the strain deformation of a minute region can be detected even for a thick object.

  As described above, in the first to fourth embodiments, the case where the tensile stress is applied in the longitudinal direction of the object 220 (FIG. 2) has been shown. However, the method of the present invention detects strain even when the object 220 is compressed. Note that you can.

  As described above, by using the method of the present invention, it is possible to easily detect a deformation amount due to distortion of an object over a large area. The method according to the present invention can be employed as a novel evaluation method in the development of new materials. For example, the method of the present invention can be applied to the evaluation of mechanical strength properties and thermoplasticity of novel polymer materials. The method according to the invention can also be useful for monitoring or inspecting plastic deformation of objects. Specifically, it is possible to prevent accidents by easily monitoring plastic deformation of structural materials, etc., and finding signs early.

Flowchart illustrating a method for detecting distortion of an object according to the present invention. Schematic diagram illustrating the principle of detecting distortion of an object according to the present invention. Graph showing the relationship between face spacing and structural color Schematic diagram of an apparatus for detecting distortion of an object according to the present invention. The figure which shows the relationship between the (A) micro-spectral-light spectrum by Example 1, and (B) peak shift amount, and the elongation rate of a sample. The schematic diagram of experiment by Example 2, and the figure which shows a digital camera photograph (A) CCD camera photograph and (B) micro-spectroscopic spectrum of the sample according to Example 2 (A) Schematic diagram of experiment, (B) Digital camera photograph, and (C) Microspectroscopy spectrum according to Example 3 The schematic diagram of experiment by Example 4, and the figure which shows a microscopic light spectrum Flow chart for measuring the amount of deformation of an object according to the prior art Schematic diagram of conventional strain distribution display device

Explanation of symbols

200 State before stress application 210 State after stress application 220 Object 230 Detection film 240 Particle 250 Elastic body 400 Apparatus 410, 600, 800, 900 Sample 420 Optical system 430 Light source 440 Optical fiber 450 Light receiving means 460 Moving means 470 Control unit 610 , 620, 630, 910 region

Claims (16)

A method for detecting distortion of an object,
Applying a detection film to the object, the detection film comprising: periodically arranged particles having a first inter-surface spacing; and an elastic body filling a gap between the particles;
Irradiating the object with light through the detection film using an optical fiber, wherein the light is irradiated perpendicularly to the surface of the object, and the light is white light; and
The step of receiving the light reflected by the particles in the detection film using the optical fiber and a spectrophotometer, and when the object is not distorted, the first surface interval is provided. When the light reflected by the particles is received and the object is distorted, the object has a second surface interval that is changed from the first surface interval to satisfy a predetermined relationship according to the strain. Receiving the light reflected by the particles; and
Moving the light relative to the object;
A step of detecting distortion of the object from the received light, and calculating a distortion amount of the object from the second surface distance obtained from the wavelength of the reflected light and the first surface distance; And visualizing the strain amount and / or strain distribution.   The method of claim 1, wherein the particles are selected from the group consisting of polystyrene particles, PMMA particles and silica particles.   The method according to claim 1, wherein the elastic body is silicone rubber or artificial rubber.   In the light receiving step, when the object is distorted, the difference ΔD between the first surface distance and the second surface distance is expressed by the relationship | (λ2−λ1) /2n|≧0.1. Λ1 is the wavelength of the light reflected by the particles having the first face spacing, and λ2 is reflected by the particles having the second face spacing. The method according to claim 1, wherein the wavelength is the light, and n is a refractive index of the detection film.   The method of claim 1, wherein the object is selected from the group consisting of metals, plastics, composite materials and plastic ceramics.   2. The method according to claim 1, wherein the predetermined relationship is a relationship in which a tensile change rate in a longitudinal direction of the object is proportional to an amount of change from the first surface interval.   The first inter-surface distance D1 is designed to be 300 / n <D1 (nm) ≦ 400 / n with respect to the tensile strain of the object, or 200 / with respect to the compressive strain of the object. The method according to claim 1, wherein n ≦ D1 (nm) <300 / n, wherein n is a refractive index of the detection film.   The first inter-surface distance D1 is designed to be 400 / n (nm) with respect to the tensile strain of the object, or 200 / n (nm) with respect to the compressive strain of the object. The method of claim 7, wherein n is a refractive index of the detection film.   The method of claim 1, wherein the spectrophotometer is a reflective spectrophotometer. An apparatus for detecting distortion of an object to which a detection film is applied, wherein the detection film includes particles having a first surface interval and an elastic body that fills a gap between the particles, which are periodically arranged. The device is
An optical system including a light source and an optical fiber that irradiates light on the surface of the object through the detection film, and the light is white light;
Light receiving means for receiving the light reflected by the particles in the detection film via the optical fiber, and when the object is not distorted, the particles having the first surface spacing In the case where the reflected light is received and the object is distorted, the particles having the second surface spacing changed from the first surface spacing to satisfy a predetermined relationship according to the strain. A light receiving means including a spectrophotometer for receiving the reflected light;
Moving means for moving the light relative to the object;
Control means for controlling the operation of the optical system, the operation of the light receiving means and the operation of the moving means, the control means,
Controlling the operation of the optical system so that the light is illuminated at right angles to the surface of the object;
A storage unit that stores data related to the wavelength of the reflected light received in advance by the light receiving means, wherein data related to the first surface interval is stored in advance.
Based on the data relating to the second surface spacing between data relating to the first surface interval stored in the storage unit, a calculation unit that calculates the distortion amount and / or strain distribution occurring on the object ,
A display means for displaying the strain amount and / or strain distribution.   The apparatus of claim 10, wherein the particles are selected from the group consisting of polystyrene particles, PMMA particles and silica particles.   The apparatus according to claim 10, wherein the elastic body is silicone rubber or artificial rubber.   In the light receiving means, when the object is distorted, a difference ΔD between the first surface distance and the second surface distance is a relationship | (λ2−λ1) /2n|≧0.1. Where λ1 is the wavelength of the light reflected by the particles having the first spacing and λ2 is reflected by the particles having the second spacing. The apparatus according to claim 10, wherein the device is a wavelength of light, and n is a refractive index of the detection film.   The apparatus according to claim 10, wherein the object is selected from the group consisting of metal, plastic, composite material and plastic ceramic.   The apparatus according to claim 10, wherein the predetermined relationship is a relationship in which a tensile change rate in a longitudinal direction of the object is proportional to a change amount from the first surface interval. The apparatus according to claim 10, wherein the spectrophotometer is a reflective spectrometer.