JP2014115219A - Strain/stress measuring method of structure and strain/stress sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noncontact-type strain/stress measuring method capable of measuring the strain or stress in static and dynamic pulling/compression directions with high accuracy, and determining each directionality thereof.SOLUTION: A strain/stress sensor including an oxide-based ceramics formed by adding 0.1-10 atom% (preferably 0.3-6.0 atom%) of Mn to AlO, in which an emission wavelength, when irradiating excitation light, fluctuates according to the intensity of a strain/stress, and a fluctuation direction of the emission wavelength is different according to the direction of the strain/stress, is installed on a structure. The strain/stress sensor is irradiated with an exciting light to undergo fluorescence emission, and the emission wavelength is measured by wavelength measuring means; and an amount and direction of emission wavelength change with respect to a reference emission wavelength, when a strain/stress does not act on the structure, are measured, to thereby measure the static or dynamic strain or stress generated in the structure, and to determine its directionality. The strain/stress sensor can be a bulk body formed by sintering the oxide-based ceramics.

Description

  The present invention relates to a non-contact strain / stress measurement technique capable of measuring and detecting strain or stress generated in a structure using light. Specifically, a strain / stress measurement method using a fluorescent material made of an oxide-based ceramic whose emission wavelength fluctuates when irradiated with excitation light according to the magnitude of applied strain / stress, and used for this The present invention relates to a strain / stress sensor.

  Understanding the physical quantities acting on the structure is important for the safe use of the structure, and a variety of monitoring techniques have been developed. As sensors for measuring physical quantities acting on the structure, sensors for various physical quantities such as displacement, strain, force, acceleration, or torque are used. As a principle of these sensors, there are many cases where the above-mentioned various physical quantities are converted into strain and measured by the strain sensor. That is, a strain sensor that can measure strain and stress fields can be a basic device that can be applied to monitoring various physical quantities.

  As a strain sensor for measuring a strain / stress field, a sensor employing an electrical method such as a strain gauge or a piezoelectric film, and an optical fiber sensor as an optical method have been developed. However, as a problem common to these conventional strain sensors, an electrical / optical signal line (cable or conductor) is required between the strain sensor and the measurer, so-called contact type (wired) measurement. Is the premise. This not only costs the arrangement of the signal lines, but also restricts the measurement location and measurement target. Therefore, there are Patent Documents 1 to 3 as so-called non-contact (wireless) strain sensors using a stress-stimulated luminescent material that emits light when a dynamic stress is applied. In Patent Document 1 to Patent Document 3, a stress light-emitting material utilizes the characteristic that the “intensity” of light emission increases in proportion to the magnitude of stress. Specifically, it is possible to measure the generation, size, distribution, etc. of strain / stress by applying a stress luminescent material to a structure, etc., and measuring the luminescence intensity from the stress luminescent material. Yes. Stress-stimulated luminescent materials emit light using the dynamic change of stress as an energy source, and change the emission intensity in response to dynamic strain / stress, so that no external electrical or optical energy supply is required. Can be cited as an advantage.

On the other hand, the present applicant has also proposed Patent Document 4 as a non-contact type strain / stress sensor that measures displacement of a structure by measuring light emission “wavelength” instead of light emission “intensity”. In the strain / stress sensor of Patent Document 4, the emission wavelength when irradiated with excitation light varies depending on the magnitude of strain / stress, and the variation direction of the emission wavelength varies depending on the direction of strain / stress, It is made of oxide ceramics in which 0.1 to 3.0 at% Eu is added as a luminescent center ion to MAl ₂ O ₄ (M = Sr, Ca, or Ba).

Non-Patent Document 1 discloses a fluorescent material made of an oxide ceramic in which the wavelength of light emission (photoluminescence) when irradiated with excitation light according to the magnitude of applied stress is varied. . In the oxide ceramics here, Cr ³⁺ is added as a luminescent center ion in Al ₂ O ₃ . There is Non-Patent Document 2 as an analysis technique of stress distribution using this phenomenon. Non-Patent Document 2 proposes a method for detecting stress based on a change in emission wavelength of Cr ³⁺ added Al ₂ O ₃ generated at the interface between the thermal barrier coating and the metal substrate.

Non-Patent Document 3 discloses a fluorescent material made of an oxide-based ceramic whose emission wavelength fluctuates when irradiated with excitation light in accordance with a given hydrostatic pressure (isotropic compressive stress). Has been. In the oxide-based ceramics here, 1% of Eu ²⁺ is added as a luminescent center ion in SrAl ₂ O ₄ or CaAl ₂ O ₄ .

JP 2004-85483 A Japanese Patent Laid-Open No. 2005-307998 Table 2006-85424 JP 2011-127992 A

J. He, and D. R. Clarke, "Determination of the Piezospectroscopic Coefficients for Chromium-Doped Sapphire", J. Am, Ceram, Soc., 78 (5), 1347-1353 (1995) Kawasaki Heavy Industries, Ltd., "Leading research on damage measurement technology by fluorescence spectroscopy in aircraft engine maintenance" New Energy and Industrial Technology Development Organization, 2006 results report C. E. Tyner and H. G. Drickamer, "Studies of Luminescence Efficiency of Eu2 + Activated Phosphors as a function of Temperature and High Pressure", J. Chem, Phys., 67 (9), 4116-4122 (1977)

  Patent Documents 1 to 3 are strain sensors using a stress light-emitting material that enables non-contact monitoring of strain / stress fields that do not require a signal line. However, in Patent Documents 1 to 3, since the dynamic strain / stress distribution and the like are measured by measuring the light emission intensity of the stress light-emitting material, there are the following problems. In other words, the light emission intensity in the stress luminescent material not only simply depends on the magnitude of the stress or strain, but also greatly depends on the rate at which the stress or strain changes. Therefore, even if a stress-stimulated luminescent material is applied to a certain structure and a distribution of luminescence intensity is obtained, it is information that reflects the magnitude of strain and stress, or the rate of change thereof. It is difficult to determine what the object is being diagnosed. In addition, some stress-stimulated luminescent materials have a light emission intensity that is reduced by repeated stress, and it is difficult to obtain stable characteristics. Furthermore, when the stress or strain does not change, the light emission phenomenon stops, so static strain / stress sensing is impossible as it is. In order to diagnose these static strains / stresses, it is necessary to continuously monitor data from the initial no-stress state and continuously accumulate data on the changes. Have a challenge.

  On the other hand, Patent Document 4 does not have the above-described problem because the displacement of the structure is measured by irradiating the excitation light to emit light and measuring the change in the emission wavelength. However, such strain / stress sensors are also required to have higher strain sensitivity.

Since the techniques of Non-Patent Document 1 and Non-Patent Document 2 utilize the fact that the emission wavelength of the fluorescent material itself changes according to the stress, there is no problem as described above. That is, it is possible to detect changes in the emission wavelength not only for dynamic strain / stress but also for static strain / stress, and since the entire fluorescent material surface emits light, it can be measured from the surface of the structure being measured. What is necessary is just to catch luminescence. However, the wavelength shift amount in the Cr ³⁺ added Al ₂ O ₃ is a change from 14429Cm ^-3 (wavelength 693.19Nm) against compressive stress of 1GPa 14426cm ^-3 to (wavelength 693.05Nm), stress Sensitivity (amount of wavelength shift per unit stress of 1 GPa) is 0.14 nm / GPa. When the Young's modulus of Al ₂ O ₃ is 335 GPa, the compressive strain for 1 GPa is 0.3%, and when the amount of wavelength shift per unit strain (1%) is defined as strain sensitivity, the strain in Cr ³⁺ added Al ₂ O ₃ is The sensitivity is 0.47 nm /%. As described above, the Cr ^{3 +} -added Al ₂ O ₃ described in Non-Patent Document 1 and Non-Patent Document 2 can detect not only dynamic strain / stress but also a change in emission wavelength with respect to static strain / stress. However, the strain sensitivity and stress sensitivity are low. If these strain sensitivity and stress sensitivity can be further improved, various advantages such as improved detection accuracy, shorter measurement time, and lower cost can be expected.

The technique of Non-Patent Document 3 also uses the fact that the emission wavelength of the fluorescent material itself changes according to the hydrostatic pressure (isotropic stress), and thus does not have the above problems. That is, it is possible to detect a change in the emission wavelength with respect to static stress. However, this document only describes the response of the emission wavelength to isotropic compressive stress under hydrostatic pressure. In the deformation of general structures, such a stress field is rarely expected, and deformation in one or two dimensions is almost all, and responsiveness not only in the compression direction but also in the tensile direction is essential. It is. Therefore, it is judged that the material system described in this document (Eu ²⁺ added as a luminescent center ion in SrAl ₂ O ₄ or CaAl ₂ O ₄ ) can be practically used as a strain / stress sensor for structures. Can not.

  Therefore, the present invention solves the above-mentioned problem, and can measure not only dynamic but also static strain or stress and its directionality (tensile direction or compression direction) with higher sensitivity at any timing. It is an object of the present invention to provide a contact-type strain / stress measurement method and a strain / stress sensor used therefor.

As a means for that purpose, the present invention changes the emission wavelength when the excitation light is irradiated according to the magnitude of strain / stress applied to the structure, and the direction of strain / stress (tensile strain / stress Fluorescent material whose emission wavelength varies depending on compression strain / stress), that is, 0.1 to 10 at% (preferably 0.3 to 6.0 at%) of Mn is added to Al ₂ O ₃ as an emission center ion. The strain / stress sensor made of the oxide-based ceramics is installed, and the strain / stress sensor is irradiated with excitation light at an arbitrary timing to emit fluorescence, and the emission wavelength at this time is measured by the wavelength measuring means and measured in advance. The amount of change in emission wavelength relative to the reference emission wavelength and the direction of change (change to short wavelength side or change to long wavelength side) are measured in a state where no strain or stress is applied to the structure. So that the structure Flip was the measurement of static and dynamic strain or stress performing the determination of the direction (or tensile direction or compression direction), it may propose strain and stress measurement method of the structure.

In this oxide ceramic (fluorescent material) in which Mn is added to Al ₂ O ₃ , a light emission phenomenon is caused when electrons excited between the electron orbits of the emission center (Mn) ions or in the defect level transition. In this light emission phenomenon, the energy state between electron orbitals or defect levels changes due to the change of the ligand field due to the strain and stress acting on the crystal structure of Al ₂ O ₃ , which changes the light emission characteristics. The principle of doing is applied. Then, in a state where strain or stress in the tensile or compressive direction is applied to the fluorescent material, fluorescence is emitted as a light emission phenomenon in the excitation-recombination process of electrons by photoluminescence (excitation light irradiation). The concept is that a light emission wavelength corresponding to the strain / stress distribution can be obtained even in a static strain / stress field.

  The strain / stress sensor may be bonded to the surface of the structure as a bulk body obtained by sintering the oxide ceramic. The bulk body is a three-dimensional shape having a certain thickness such as a plate shape (flaky shape) or a lump shape, and the specific shape is not particularly limited. The stress acting on the structure can be measured based on the Young's modulus of the structure that is the object to be measured from the amount of strain obtained by the strain / stress sensor.

Also, a strain / stress sensor that is installed in a structure and measures strain or stress generated in the structure, and the emission wavelength varies when excitation light is irradiated according to the magnitude of the strain / stress. And 0.1 to 10 at% (preferably 0.3 to 6.0 at%) of Mn as a luminescent center ion is added to Al ₂ O ₃ , and the direction of fluctuation of the emission wavelength varies depending on the direction of strain and stress. A strain / stress sensor made of an oxide-based ceramic can also be proposed. The strain / stress sensor may be a bulk body obtained by sintering the oxide ceramics.

The strain / stress sensor of the present invention is made of an oxide ceramic that is a fluorescent material obtained by adding 0.1 to 10 at% (preferably 0.3 to 6.0 at%) of Mn to Al ₂ O ₃ . The shift amount of the emission wavelength with respect to the reference emission wavelength according to the magnitude of strain / stress is large. Therefore, according to the strain / stress sensor using this fluorescent material, the strain or stress in the structure can be measured with high accuracy. It is also advantageous for shortening the measurement time and reducing the cost. Further, in the strain / stress sensor of the present invention, the direction of the emission wavelength shift is changed depending on the strain / stress application direction of tension / compression, and one-dimensional or two-dimensional strain / It has been found for the first time that it exhibits responsiveness to a stress field, which enables deformation diagnosis in an actual structure. That is, it is possible to reliably measure static and dynamic strains or stresses in the compression direction as well as the tensile direction generated in the structure. Moreover, it is possible to determine the directionality, that is, whether the strain / stress in the tensile direction or the strain / stress in the compression direction.

  Since the strain / stress measurement method of the structure of the present invention is a non-contact type measurement method using the light emission phenomenon of the fluorescent material, such as multi-point measurement in a large structure having a wide range of diagnosis targets, such as high places and access control areas, etc. High-precision measurement is possible even for diagnostic objects that are difficult or impossible with contact-type sensors, such as measurement in hazardous locations, measurement in a vacuum, and measurement in a high-speed rotating body. In addition, due to the nature of light that can be condensed and diverged, it is possible to select an arbitrary sensing area from the micro area of the measurement point, and to improve the accuracy of strain and stress distribution diagnosis in the plane by two-dimensional scanning. It is also effective for speeding up.

  In addition, since strain or stress is measured by the amount of change (shift) in the fluorescence emission wavelength when irradiated with excitation light, not only dynamic strain and stress fields as in the prior art, but also static strain and stress fields. Strain or stress can be measured. That is, the strain or stress can be measured not only at the moment when the stress is applied but also after the stress is applied. Since the wavelength change due to the strain / stress in the static strain / stress field is measured, there is no influence of the strain / stress change rate unlike the dynamic strain / stress field, and the strain or stress can be accurately measured. In addition, since it emits light whenever it is irradiated with excitation light, there is no need to constantly observe it like dynamic strain / stress, and strain or stress can be measured at any timing. In addition, since the present invention detects a change in emission wavelength based on a change in the structure of the fluorescent material, the spatial resolution can be narrowed by condensing light compared to the case of using a grating, and the detection direction of emission is also limited. I do not receive it.

  By adopting a form in which the strain / stress sensor of the present invention is attached to the surface of a structure as a bulk body, the manufacturing is easy, the restrictions on the object are small, and the workability is good. When affixing to a structure, it is necessary to consider the heat resistance at the adhesive interface, but this can be solved by making the strain / stress sensor into a thin piece, and the strain followability and limit value It is also advantageous for expansion.

It is a schematic diagram which shows the mechanism of the strain / stress measurement method. It is a schematic diagram of the mechanism which gives a compressive strain. It is a schematic diagram of the mechanism which gives a tensile strain. It is a graph which shows the shift direction of PL emission spectrum at the time of giving compression distortion. It is a graph which shows the relationship between the magnitude | size of a compressive strain, and the shift amount of PL emission spectrum accompanying this. It is a graph which shows the relationship between the magnitude | size of a tensile strain and the shift amount of PL emission spectrum accompanying this.

  In the present invention, the emission wavelength varies when the excitation light is irradiated according to the applied strain / stress, and the emission wavelength varies according to the direction of the strain / stress (tensile direction or compression direction). A fluorescent material made of oxide ceramics with different directions is used as a strain / stress sensor to measure dynamic or static strain or stress when stress acts on a structure. In the following description, fluorescence emission due to excitation light irradiation may be referred to as PL emission.

The fluorescent material used in the strain / stress sensor of the present invention is a material in which Mn is added to Al ₂ O ₃ . In other words, does not consist MnAl ₂ O ₄ single phase, it has a crystal structure in which the Al ₂ O ₃ phase and MnAl ₂ O ₄ phase are mixed. The amount of Mn added is 0.1 to 10 at%, preferably 0.3 to 6.0 at%, more preferably 4.0 to 6.0 at%. This is because the strain / stress sensitivity decreases if the amount of Mn added is too large or too small. When the amount of Mn added is 4.0 to 6.0 at%, the strain / stress sensitivity is the highest.

Moreover, it is also preferable to add H ₂ BO ₃ to the oxide ceramics as an additive for further improving strain / stress sensitivity. The addition amount may be about 0.5 to 5.0 at%, preferably about 1.0 to 3.0 at%.

The PL emission in the fluorescent material causes a light emission phenomenon when electrons excited between electron orbits of the emission center (Mn) ion or in a defect level transition. When such a fluorescent material is used as a strain / stress sensor, in the above luminescence phenomenon, the ligand field changes due to the strain acting on the crystal structure of Al ₂ O ₃ , and thus the electrons of the luminescent center ions. The principle that the energy state between the orbits or the defect level changes and the emission characteristics, that is, the PL emission wavelength fluctuate (shift) by this is applied.

  The strain / stress sensor made of such an oxide ceramic may be a sintered body (bulk body) obtained by firing a ceramic material (starting material). Typically, it can be produced by a known solid phase reaction method in which ceramic raw material powders are mixed and fired. Specifically, various starting materials may be mixed and fired at a temperature lower than the melting point of each starting material to obtain a sintered body. At this time, if necessary, the starting materials are mixed and calcined at a temperature lower than the firing (fired) temperature, and the sintered body after the calcination is pulverized and molded, followed by firing (fired). ) Is preferable. This is because the composition can be made uniform and dense.

At this time, the amount of oxygen vacancies in the base material (Al ₂ O ₃ ) affects not only the shift amount of the PL emission wavelength but also the emission intensity, and when baked in the atmosphere, the PL emission intensity tends to be weakened. Therefore, firing and calcination as necessary are performed in an oxygen-free atmosphere to prevent oxidation. A reducing atmosphere is preferable. This is because, in a reducing atmosphere, oxygen deficiency can be positively introduced into the base material structure, and a valence state of Mn that can easily change the luminescence energy state with respect to changes in the ligand field, or a defect order can be formed. . The oxygen-free atmosphere may be an inert gas such as Ar gas or a nitrogen gas atmosphere. In order to obtain a more preferable reducing atmosphere, an atmosphere in which about 5% hydrogen gas is mixed in an inert gas may be used.

  The shape of the strain / stress sensor made of a bulk body of oxide ceramics is not particularly limited as long as it is a shape that can be installed on a structure, but is preferably in the form of a flake (for example, about 0.1 to 5 mm thick). If it is flake-like, the followability to the strain generated in the structure is good and the workability is also good. Or it can also be set as the three-dimensional bulk body which has fixed thickness. The flaky strain / stress sensor can be directly sintered into a flaky shape, or a bulk material having a certain thickness can be formed into a flaky shape by post-processing such as cutting, cutting, or grinding. A strain / stress sensor made of a bulk body can be installed by adhering to the surface of the structure. At this time, a dent can be provided at an arbitrary part of the structure so as to embed the strain / stress sensor, or it can be installed so as to be sandwiched between two points in the structure. When installed so as to be sandwiched between structures, it is suitable for measurement of compressive stress.

  A method for measuring strain or stress generated in the structure using the strain / stress sensor thus installed will be described. As shown in FIG. 1, when the strain / stress sensor 10 installed in the structure 1 is irradiated with excitation light 11, the strain / stress sensor 10 emits fluorescence. Measure by measuring means. As the excitation light 11 to be irradiated, light having a higher energy (short wavelength) than the emission wavelength is used. Specifically, excitation light having a wavelength of about 250 to 500 nm can be mentioned. The wavelength measuring means is not particularly limited as long as it can measure the wavelength of light, and a known device can be used. A typical example is a spectroscope.

  On the premise of this, first, the reference emission wavelength in a state where the structure 1 is not distorted is measured in advance. The reference emission wavelength may be measured immediately after the strain / stress sensor 10 is installed on the structure 1 or before the strain / stress sensor 10 is installed on the structure 1. Then, after the strain / stress sensor 10 is installed on the structure 1, when the wavelength of the fluorescence emission 12 is measured at an arbitrary timing (after an arbitrary time has elapsed), if the structure 1 is distorted, the fluorescence emission The wavelength of 12 is different from the reference emission wavelength. Therefore, by measuring the emission wavelength change (shift amount) with respect to the reference emission wavelength, the strain generated in the structure 1 can be measured. At this time, depending on the direction of strain, that is, tensile strain or compression strain, the direction of emission wavelength change is reversed (shift to short wavelength side or shift to long wavelength side). Whether the strain is in the tensile direction or the strain in the compression direction can also be determined based on the directionality. Of course, if the structure 1 is not distorted, there is no change in the emission wavelength. Further, since the strain and the stress are in a proportional relationship with the Young's modulus as a proportional constant, the stress can be obtained from the measured strain value. At the same time, it can be determined whether it is tensile stress or compressive stress. It is efficient that the reference emission wavelength is stored in an information processing apparatus connected to the wavelength measuring means, and the reference emission wavelength and the emission wavelength are also compared by the information processing apparatus.

  The measurement object is not particularly limited as long as it is a structure on which stress can act, and includes various structures from large structures to small structure parts. In particular, since the strain / stress measurement method of the present invention is a non-contact measurement method, multipoint measurement in large structures with a wide diagnostic range such as dams and tunnels, steel towers such as radio towers and power transmission towers, high-rise buildings, power generation Suitable for measurements that are difficult or impossible with contact-type sensors, such as measurements in hazardous places such as high places and access control areas, measurements in high-speed rotating bodies such as turbines and motors, and measurements in sealed spaces such as in vacuum. It is.

As a sample for a strain / stress sensor, two types of Al ₂ O ₃ added with 0.5 at% Mn (Example 1) and 5.0 at% added (Example 2) were used. Was further compared with the results of Eu added SrAl ₂ O ₄ in Patent Document 4 (Comparative Example 1) as compared with the conventional.

As starting materials, a-Al ₂ O ₃ (high purity chemical, 99.99%>, ALO12PB) and MnO (high purity chemical, 99.9%>, MNO01PB) powder in stoichiometric composition Weighed to match. Further, 2.0 at% of boric acid H ₃ BO ₃ (manufactured by Kanto Chemical Co., 99.9999%>, 765-1M) was added. These raw materials were mixed with a ZrO ₂ ball in a PET container for 1 hour using ethanol as a dispersion medium. The mixed slurry was extracted from the mixed slurry by dispersing ethanol in an atmosphere at 130 ° C., and sized with a sieve having a mesh size of 250 μm while being pulverized in a mortar. Then, uniaxial press molding was performed at a pressure of 500 kgf / mm ² into a shape of 20 mmφ × 2 mmt. Furthermore, a hydrostatic pressure of 2500 kgf / mm ² was applied to the molded body by CIP treatment. The molded body was directly fired without going through the calcination step. In the firing, the temperature was raised to 1400 ° C. at a rate of temperature rise of 200 ° C./h, the temperature was maintained for 12 hours, and then the furnace cooling rate. The process of lowering the temperature. The atmosphere in this main firing process was Ar in Example 1 and Ar + 4% H _{2 in} Example 2. Finally, the obtained sintered body was processed into a thin piece having a thickness of 0.5 mm to obtain a strain / stress sensor.

  Then, compressive / tensile strain was applied to the strain / stress sensor to examine the wavelength shift of the PL emission spectrum. Specifically, when compressive strain is applied, as shown in FIG. 2, a strain / stress sensor 10 is sandwiched from above and below by a stainless steel plate 1 as a simulated structure, and compressive stress is applied from above and below. The emission wavelength at this time was measured. On the other hand, when tensile strain is applied, as shown in FIG. 3, a strain / stress sensor 10 is bonded to a stainless steel plate 1 having a length of 150 mm, a width of 25 mm, and a thickness of 2 mm as a simulated structure. By grasping and pulling from above and below, tensile strain was also applied to the strain / stress sensor 10, and the emission wavelength at this time was measured. A spectroscope capable of spectrally detecting a wavelength of 200 to 950 nm with a CCD linear image sensor at a time (C10027-1 manufactured by Hamamatsu Photonics) was used as a spectroscope for measuring the emission wavelength. As an excitation light source for irradiating each test piece 100, a UV-LED light source (manufactured by Hamamatsu Photonics, L9610) having an emission wavelength of 365 nm was used.

  As an example showing the operating state of the strain / stress sensor, when the compressive strain is increased (increase to the minus side) in the strain / stress sensor of Example 1, the peak wavelength of the PL emission spectrum is as shown in FIG. It increased to the long wavelength side. Although not shown, the same tendency was shown in Example 2 and Comparative Example 1.

  Subsequently, in order to quantitatively evaluate the shift amount of the PL emission spectrum in Examples 1 and 2 and Comparative Example 1, the wavelength of the PL emission spectrum corresponding to the magnitude of the compressive strain is converted into energy and Gaussian distribution. And the peak position (wavelength) was identified as the central wavelength of the Gaussian distribution. FIG. 5 shows a summary of the relationship between the shift amount of the peak wavelength (vertical axis) and the magnitude of the compressive strain (horizontal axis).

From the slope of the result of FIG. 5, the wavelength change per unit strain (1% strain) in Example 1 is −9.1 nm /%, and the wavelength change per unit strain (1% strain) in Example 2 is −14. 7 nm /%, wavelength change per unit strain (1% strain) in Comparative Example 1 can be estimated as -2.1 nm /%, and Comparative Example 1 made of conventional Eu-added SrAl ₂ O ₄ has low strain sensitivity. On the other hand, it was confirmed that Examples 1 and 2 in which a predetermined amount of Mn was added to Al ₂ O ₃ had high strain sensitivity.

  Next, in order to quantitatively evaluate the shift amount of the PL emission spectrum when tensile strain is applied to the strain / stress sensor, tensile strain is applied to the strain / stress sensor of Example 1 and Comparative Example 1, Similar to the case of compressive strain, the relationship between the shift amount of the peak wavelength of the PL emission spectrum (vertical axis) and the magnitude of the compressive strain (horizontal axis) is summarized. The result is shown in FIG.

  From the results of FIG. 6, when tensile strain was applied to the strain / stress sensor, the PL emission spectrum was shifted in the opposite direction to that when compressive strain was applied. That is, it was confirmed that when tensile strain acts on the strain / stress sensor, the PL emission spectrum shifts to the short wavelength side, contrary to the case of compressive strain. As a result, it has been found that the determination of whether the applied strain is tensile or compression can be accurately detected from the directionality of the wavelength shift. In an actual structure, there are not only a plane to be diagnosed but also a plane having a local ratio, and in such an environment, it is necessary to assume the action of tensile or compressive strain due to bending deformation. Even in such an environment, the fact that the method based on the wavelength shift of the fluorescent material enables accurate detection is very advantageous from the viewpoint of applicability.

Further, from the slope of the result of FIG. 6, the wavelength change per unit strain (1% strain) in Example 1 is −7.9 nm /%, and the wavelength change per unit strain (1% strain) in Comparative Example 1 is − As in the case of compressive strain, in Comparative Example 1 made of conventional Eu-added SrAl ₂ O ₄ , the strain sensitivity is low, whereas M ₂ is included in Al ₂ O _3. It was confirmed that Example 1 added quantitatively had high strain sensitivity.

DESCRIPTION OF SYMBOLS 1 Structure 10 Strain / stress sensor 11 Excitation light 12 Fluorescence emission

Claims (6)

The structure, the emission wavelength when irradiated with excitation light is varied depending on the magnitude of the distortion-stress and variation direction of the emission wavelengths differ depending on the direction of the strain and stress, Mn in Al ₂ O ₃ A strain / stress sensor made of oxide ceramics with 0.1 to 10 at% added,
The strain / stress sensor is irradiated with excitation light to emit fluorescence, the emission wavelength is measured by a wavelength measuring means, and the emission wavelength change amount with respect to a reference emission wavelength in a state in which no strain / stress acts on the structure; A structure strain / stress measurement method for measuring static and dynamic strain or stress generated in a structure and determining its direction by measuring the direction of the change.   The strain / stress measurement method according to claim 1, wherein the amount of Mn added is 0.3 to 6.0 at%.   The strain / stress measurement method for a structure according to claim 1, wherein the strain / stress sensor is formed of a bulk body obtained by sintering the oxide ceramic. A strain / stress sensor for measuring strain or stress in the tensile and compression directions generated in the structure when installed in the structure,
Emission wavelength when irradiated with excitation light is varied depending on the magnitude of the distortion-stress and variation direction of the emission wavelengths differ depending on the direction of the strain and stress, the Mn in the Al ₂ O ₃ 0.1 Strain / stress sensor made of oxide ceramics with 10at% added.   The strain / stress sensor according to claim 4, wherein the amount of Mn added is 0.3 to 6.0 at%. The strain / stress sensor according to claim 4 or 5, comprising a bulk body obtained by sintering the oxide-based ceramic.

Images