Electron spin resonance apparatus and degradation evaluation method

Abstract

This electron spin resonance device comprises a hollow resonator having a microwave oscillator, a magnet, a modulation coil, and an opening. Microwaves generated by the microwave oscillator resonate in the hollow resonator and are emitted from the opening toward an object being measured that is positioned outside of the opening. The magnet applies a magnetic field to an irradiated surface at which the object being measured is irradiated with the microwaves. The modulation coil modulates either the strength of the magnetic field applied to the irradiated surface at which the object being measured is irradiated with the microwaves, or the frequency of the microwaves.

Description

Technical Field

[0001] The present invention relates to an electron spin resonance apparatus and a deterioration evaluation method. This application claims priority based on Japanese Patent Application No. 2022-001004 filed in Japan on January 6, 2022, and the content thereof is incorporated herein by reference.

Background Art

[0002] An electron spin resonance (ESR) apparatus is a device that can selectively measure free radicals. Electron spin resonance (ESR) apparatuses are used in basic fields of science and medicine, production lines such as semiconductors, and medical fields such as cancer diagnosis.

[0003] For example, Patent Document 1 describes an electron spin resonance apparatus that applies a static magnetic field using a pair of left and right magnetic field gradient coils to a cavity resonator having a cylindrical cavity and applies high-frequency microwaves into the cavity resonator.

[0004] Also, for example, Patent Document 2 describes an electron spin resonance apparatus that sweeps the frequency of microwaves while applying a constant magnetic field with a permanent magnet.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The electron spin resonance apparatus described in Patent Document 1 applies a magnetic field to a sample using a magnetic field gradient coil arranged to sandwich the sample. This is to increase the Q value (Quality factor) of the electron spin resonance apparatus by applying a sufficient magnetic field to the sample. The sample needs to be inserted into the space sandwiched by the magnetic field gradient coils, and the sample size and sample shape are limited. Also, the apparatus described in Patent Document 1 is large and cannot be carried around or the like.

[0007] Patent Document 2 describes that a small electron spin resonance apparatus can be realized by using a permanent magnet and a spiral inductor. On the other hand, in the apparatus described in Patent Document 2, the measurement object needs to be arranged at a position surrounded by the spiral inductor, and the applicable sample size and sample shape are limited. Also, Patent Document 2 does not describe that the electron spin resonance apparatus itself can be carried around and measurements can be performed at the carried location.

[0008] The present disclosure has been made in view of the above problems, and an object thereof is to provide an electron spin resonance apparatus and a degradation evaluation method that are portable and can measure a measurement object of any shape.

Means for Solving the Problems

[0009] The present disclosure provides the following means to solve the above problems.

[0010] (1) The electron spin resonance apparatus according to the first aspect includes a microwave oscillator, a magnet, a modulation coil, and a cavity resonator having an aperture. The microwave generated by the microwave oscillator resonates in the cavity resonator and is irradiated from the aperture toward a measurement object located outside the aperture. The magnet applies a magnetic field toward the irradiation surface of the measurement object irradiated with the microwave. The modulation coil modulates the intensity of the magnetic field or the frequency of the microwave applied toward the irradiation surface of the measurement object.

[0011] (2) The electron spin resonance apparatus according to the above embodiment has 10 in the penetration region that is irradiated and penetrated by the microwaves. 11 This method may also be used for the aforementioned measurement target that contains spins of 1 / g or more.

[0012] (3) The electron spin resonance apparatus according to the above embodiment may also be used when the object to be measured is a carbon fiber composite material.

[0013] (4) In the electron spin resonance apparatus according to the above embodiment, the modulation coil may sweep the magnetic field within a range of ±2mT with respect to 319.5mT.

[0014] (5) The electron spin resonance apparatus according to the above embodiment may be portable and can be installed on a measurement target of any shape.

[0015] (6) The electron spin resonance apparatus according to the above embodiment may have a plurality of units. Each of the plurality of units includes the microwave oscillator, the magnet, the modulation coil, and the cavity resonator.

[0016] (7) In the plurality of units of the electron spin resonance apparatus according to the above embodiment, some units may share at least one of the microwave oscillator, the magnet, and the modulation coil.

[0017] (8) The degradation evaluation method according to the second embodiment comprises a detection step of irradiating the object to be measured with microwaves and applying a magnetic field to the irradiation surface of the object to be measured to which the microwaves are irradiated, and detecting the number of spins of the object to be measured by electron spin resonance, and an evaluation step of evaluating the degradation of the object to be measured from the number of spins.

[0018] (9) The degradation evaluation method according to the above embodiment may further include a preparation step before the detection step, in which a reference sample having the same configuration as the object to be measured is used to determine in advance the relationship between the degradation of the reference sample and the spin number of the reference sample.

[0019] (10) In the deterioration evaluation method according to the above aspect, the preparation step includes a step of obtaining a critical value by dividing the number of spins of the reference sample at the time when the load at which the reference sample breaks is applied by the number of spins of the reference sample before the load is applied. The evaluation step includes a step of fitting a graph with the horizontal axis being the number of times of applying a load (N) to the measurement object and the vertical axis being the normalized number of spins (N spin (N) / N spin (0)) to the following formula (1), and a step of substituting the critical value into the left side of the following formula (1) and estimating the number of times of applying a load at which the measurement object reaches destruction. N spin (N) / N spin (0)=Alog 10 (N + 1)+1…(1) In formula (1), N spin (N) is the number of spins of the measurement object after N times of loads are applied, and N spin (0) is the number of spins of the measurement object before the load is applied, and A is a constant.

[0020] (11) In the deterioration evaluation method according to the above aspect, the preparation step may include a step of fitting a graph with the horizontal axis being the number of times of applying a load (N) to the reference sample and the vertical axis being the normalized number of spins (N’ spin (N) / N’ spin (0)) to the following formula (2). N’ spin (N) / N’ spin N’ 10 (0)=A’log In formula (2), N’ spin (N) is the number of spins of the reference sample after N times of loads are applied, and N’ spin (0) is the number of spins of the reference sample before the load is applied, and A’ is a constant.

[0021] (12) In the deterioration evaluation method according to the above aspect, the evaluation step may include an estimation step of substituting the number of spins detected in the detection step into N’ spin (N) in the formula (2) and estimating the number of times of the load applied to the measurement object.

[0022] (13) In the deterioration evaluation method according to the above embodiment, the preparation step may include a step of determining the number of times a load is applied that causes damage to the reference sample, and the evaluation step may include a step of determining the remaining life of the measurement target by subtracting the number of times a load has been applied to the measurement target estimated in the estimation step from the number of times a load is applied that causes damage to the reference sample.

[0023] (14) In the above embodiment of the degradation evaluation method, the object to be measured may also be a carbon fiber composite material. [Effects of the Invention]

[0024] The electron spin resonance apparatus according to the above embodiment is portable and can measure objects of any shape. Furthermore, the degradation evaluation method according to the above embodiment can evaluate the degradation of the object using electron spin resonance. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic cross-sectional view of an electron spin resonance apparatus according to the first embodiment. [Figure 2] This is an illustrative diagram illustrating the measurement principle of the electron spin resonance apparatus according to the first embodiment. [Figure 3] This is a first flowchart of the deterioration evaluation method according to the first embodiment. [Figure 4] This is a second flowchart of the deterioration evaluation method according to the first embodiment. [Figure 5] This is a schematic perspective view of an electron spin resonance apparatus according to the first modified example. [Figure 6] This is a schematic perspective view of an electron spin resonance apparatus relating to the second modified example. [Figure 7] This is an illustrative diagram of the measurement sample for Experimental Example 1. [Figure 8] These are the measurement results for Experimental Example 1. [Figure 9] This is a graph of the original data of the ESR signal obtained in Experimental Example 2. [Figure 10]This is a graph of the original ESR signal data obtained in Experimental Example 2, integrated once. [Figure 11] This graph shows the dependence of the number of spins on the number of loads obtained in Experimental Example 2. [Figure 12] This graph shows the dependence of the ESR full width at half maximum, obtained in Experimental Example 2, on the number of load cycles. [Figure 13] This graph shows the dependence of the number of spins on the number of loads obtained in Experimental Example 3. [Figure 14] This is the result of fitting a graph showing the dependence of the number of spins on the number of loads. [Modes for carrying out the invention]

[0026] The present embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may be enlarged for convenience to clearly illustrate the features of the present invention, and the dimensional ratios of each component may differ from those in reality. The materials, dimensions, etc., exemplified in the following description are examples only, and the present invention is not limited to them. It can be implemented with appropriate modifications without altering its essence.

[0027] Figure 1 is a schematic cross-sectional view of the electron spin resonance apparatus 10 according to the first embodiment. The electron spin resonance apparatus 10 is used to evaluate the state of the object to be measured 1.

[0028] The electron spin resonance apparatus 10 comprises, for example, a microwave oscillator 11, a magnet 12, a modulation coil 13, and a cavity resonator 14. The electron spin resonance apparatus 10 is connected to a power supply 15 and a detection device 16 when in use.

[0029] The microwave oscillator 11 generates microwaves M when connected to the power supply 15. The power supply 15 is, for example, a high-frequency power supply. Any known microwave oscillator can be used as the microwave oscillator 11. The frequency of the microwaves M is not particularly limited, but for example, the frequency of the microwaves M is 9 GHz.

[0030] The cavity resonator 14 is located at a position where microwaves M generated by the microwave oscillator 11 reach it. The microwaves M generated by the microwave oscillator 11 reach the cavity resonator 14. Inside the cavity resonator 14 is a cavity 14A. There is also an aperture 14B in a part of the cavity resonator 14. The microwaves M resonate in the cavity 14A and are emitted to the outside through the aperture 14B. The microwaves M emitted from the aperture 14B irradiate at least a part of the object to be measured 1. Hereinafter, the surface of the object to be measured 1 that is irradiated with microwaves M will be referred to as the irradiated surface. The object to be measured 1 is located opposite the aperture 14B. The aperture 14B is, for example, a circle with a diameter of 3 cm.

[0031] The magnet 12 applies a magnetic field H toward the object to be measured 1. The magnet 12 applies a magnetic field H toward the irradiation surface of the object to be measured 1 that is irradiated with microwaves M. The magnet 12 is positioned, for example, opposite the object to be measured 1. The magnet 12 is, for example, a permanent magnet.

[0032] The modulation coil 13 changes, for example, the strength (magnetic flux density) of the magnetic field H applied from the magnet 12 to the irradiation surface of the object to be measured 1. The modulation coil 13 may also change the frequency of the microwave M. The modulation coil 13 includes, for example, a first modulation coil that determines the reference of the applied magnetic field, and a second modulation coil that sweeps the strength of the magnetic field within a certain range from the reference magnetic field strength.

[0033] The first modulation coil sets the strength of the magnetic field H applied to the object to be measured 1 from the magnet 12 to the resonant magnetic field H0. For example, if the object to be measured 1 is a carbon fiber composite material, the resonant magnetic field H0 is 319.5 mT. The second modulation coil sweeps the magnetic field within a certain range with respect to the resonant magnetic field H0. If the object to be measured 1 is determined, it is not necessary to widen the sweep width of the magnetic field. For example, the second modulation coil sweeps within a range of ±2 mT with respect to the resonant magnetic field H0. The sweep width may also be within a range of ±1 mT with respect to the resonant magnetic field H0. If the object to be measured 1 is determined, the sweep width may be narrow. In other words, the modulation coil 13 does not need to sweep the magnetic field over a wide range and can be miniaturized.

[0034] The detection device 16 includes, for example, a detector 16A, an amplifier 16B, and a computer 16C. Detector 16A detects electron spin resonance (ESR) signals. Detector 16A is, for example, a crystal diode detector. Amplifier 16B amplifies the electron spin resonance signals. Computer 16C is, for example, a computer. Computer 16C is used for analyzing electron spin resonance signals. Computer 16C includes, for example, a recording area for recording detected data and a signal processing area for analyzing detected data.

[0035] Figure 2 is an illustrative diagram illustrating the measurement principle of the electron spin resonance apparatus 10 according to the first embodiment.

[0036] As shown in Figure 2, when a load is applied to the object being measured 1, the state of the object being measured 1 changes. When a load is applied to the object being measured 1, for example, the intermolecular forces between polymer chains change, polymer chains are broken, the cross-linking structure is destroyed, and stress changes occur in the interfiber interface bonds. For example, when polymer chains are broken, radicals are generated at the cut surface, causing spin sp (unpaired electrons) to be generated within the object being measured 1.

[0037] In a magnetic field, a spin sp splits into a β spin parallel to the magnetic field and an α spin antiparallel to the magnetic field due to the Zeeman effect. The energy difference between the α spin and the β spin increases proportionally to the magnetic field strength. This energy difference ΔE is the energy of the microwave M (hv=gμ). B When the electron spin matches H0), it absorbs microwave M and transitions to a higher level. An electron spin resonance signal is observed during this level transition. The electron spin resonance signal is, for example, the absorption spectrum of microwave M. In this procedure, the electron spin resonance apparatus 10 evaluates the state of the object being measured 1.

[0038] Here, the measurement principle of the electron spin resonance apparatus 10 was explained using the example of fixing the microwave M and sweeping the magnetic field strength, but it is also possible to fix the magnetic field strength and sweep the frequency of the microwave M.

[0039] The object to be measured 1 is, for example, one that has a high concentration of spin. For example, the object to be measured 1 is irradiated with microwave M and penetrates into a penetration region 2, and 10 11 Contains spins of 10 or more particles / g. Measurement target 1 has 10 in penetration area 2. 15 Preferably, it contains spins of 10 or more per gram. 17 It is more preferable to include spins of 10 or more per gram, 20 It is even more preferable that the spins contain more than 1 / g. If the measurement target 1 is limited to a substance having a high concentration of spins, high sensitivity is not required for the electron spin resonance apparatus 10. Therefore, the electron spin resonance apparatus 10 according to this embodiment can be miniaturized and its configuration simplified.

[0040] Penetration region 2 is the range through which microwave M can penetrate. Penetration region 2 is expressed as the product of "the area irradiated by microwave M" and "the depth to which microwave M penetrates." In measurement target 1, the area irradiated by microwave M is the area opposite aperture 14B. Therefore, the area irradiated by microwave M in measurement target 1 is approximately the same as, for example, the area of ​​aperture 14B. The area irradiated by microwave M is the same as the area of ​​the irradiated surface. Also, the depth to which microwave M penetrates in measurement target 1 is approximately 1 cm. That is, penetration region 2 is, for example, 10 cm. 3 It's a matter of degree.

[0041] Measurement target 1 is, for example, a carbon fiber composite material. Carbon fiber composite materials include, for example, CFRP (Carbon Fiber Reinforced plastics) and CFRTP (Carbon Fiber Reinforced Thermoplastics). CFRP is a reinforced plastic in which carbon fibers are used as the reinforcing material and thermosetting resin as the base material. CFRTP is a reinforced plastic in which carbon fibers are used as the reinforcing material and thermoplastic resin as the base material. Due to the difference in thermal shrinkage rates between carbon fibers and resin, carbon fiber composite materials are prone to internal stress during manufacturing. Therefore, carbon fiber composite materials have a high concentration of spin even in an unloaded state before a load is applied. Carbon fiber composite materials are used in aircraft, automobiles, etc.

[0042] The electron spin resonance apparatus 10 is small, lightweight, and portable. Furthermore, since the electron spin resonance apparatus 10 applies the magnetic field H and microwave M in the same direction, it is not necessary to sandwich the object to be measured 1 between the sources of the magnetic field H or microwave M. Therefore, there are no restrictions on the size or shape of the object to be measured 1, and objects of any shape can be measured. For example, even if the object to be measured 1 is an airplane, the state of the object to be measured 1 can be evaluated by facing the aperture 14B of the electron spin resonance apparatus 10 to the measurement point.

[0043] Next, a method for evaluating the degradation of a measurement target using the electron spin resonance apparatus 10 according to this embodiment will be described. Figure 3 is a first flowchart of the degradation evaluation method according to the first embodiment.

[0044] A degradation evaluation method includes, for example, a preparation step S1, a detection step S2, and an evaluation step S3. Preparation step S1 is performed in advance before evaluating the actual object to be measured 1. Detection step S2 and evaluation step S3 involve measuring the actual object to be measured 1.

[0045] Preparation step S1 includes, for example, a reference sample preparation step S11, a reference sample measurement step S12, a load application step S13, a lifetime measurement step S14, and a critical value calculation step S15. Preparation step S1 is performed before detection step S2. In preparation step S1, the relationship between the degradation of the reference sample and the electron spin resonance signal (ESR signal) of the reference sample is determined in advance using a reference sample with the same configuration as the object to be measured 1.

[0046] In the reference sample preparation step S11, a reference sample is prepared. The reference sample shall consist of the same material as the sample to be measured 1. For example, the reference sample is a sample prepared under the same conditions as the sample to be measured 1. The reference sample may be, for example, a carbon fiber composite material. The size of the reference sample does not need to match that of the sample to be measured 1; it may be any size.

[0047] In the reference sample measurement step S12, electron spin resonance analysis is performed on the reference sample. The reference sample measurement step S12 is performed before applying a load to the reference sample and after a predetermined number of load applications. The reference sample measurement step S12 may be performed using, for example, the electron spin resonance apparatus 10 described above, or using a known electron spin resonance apparatus. Since the size of the reference sample is not a factor, the measurement can also be performed using a conventional electron spin resonance apparatus in which the sample is placed in a cavity where microwaves resonate.

[0048] In the load application step S13, a load is applied to the reference sample. For example, the reference sample is stretched in one direction. The cycle of applying and releasing a load to the reference sample is considered one cycle, and the load is applied to the reference sample multiple times. The reference sample measurement step S12 is performed at regular intervals after a certain number of load applications.

[0049] In the life measurement process S14, the number of load applications required to cause failure of the reference sample is determined. There are two patterns of failure of the reference sample: delamination and complete fracture. Delamination is the occurrence of in-plane cracks within the reference sample, while complete fracture means that the reference sample completely breaks. In the life measurement process S14, for example, the number of load applications required to cause delamination and the number of load applications required to cause complete fracture are determined.

[0050] In the critical value calculation step S15, at least one of the normalized spin number at the time of delamination and the normalized spin number at the time of complete failure is determined. The number of load cycles until failure is N. max And the spin number of the reference sample at that time is N' spin (N max ) Let's assume N' spin (N max ) to N' spin The value obtained by dividing by (0) is the normalized spin number at the point of destruction, and will be referred to as the critical value below. N' spin(0) is the spin number of the reference sample before load application. The critical value represents how many times the spin number increases from the initial state when the load is applied until fracture occurs. For example, when the critical value is 1.85 (the spin number becomes 1.85 times), delamination occurs, and when the critical value is approximately 2.0 times (the spin number becomes approximately 2 times), complete fracture may occur.

[0051] In detection step S2, the actual object to be measured 1 is measured. Detection step S2 includes a measurement step S21 in which the object to be measured 1 is actually measured, and a load application step S22 in which a load is applied to the object to be measured 1.

[0052] The measurement step S21 may be performed before applying a load to the object to be measured 1, and after applying a predetermined number of loads. The measurement step S21 is performed, for example, using the electron spin resonance apparatus 10 described above. In the measurement step S21, microwaves M and a magnetic field H are applied to the object to be measured 1, and the electron spin resonance signal of the object to be measured 1 is detected by electron spin resonance.

[0053] In the measurement process S21, the intensity of the magnetic field H may be fixed and the frequency of the microwave M may be swept, or the frequency of the microwave M may be fixed and the intensity of the magnetic field H may be swept. Here, we will explain using the case where the frequency of the microwave M is fixed and the intensity of the magnetic field H is swept as an example.

[0054] First, the electron spin resonance apparatus 10 is set up so that its aperture 14B faces the object to be measured 1. Because the electron spin resonance apparatus 10 is small and portable, it can be set up even for large objects to be measured 1, such as airplanes or automobiles.

[0055] Next, the microwave oscillator 11 is connected to the power supply 15 to generate microwaves. The microwaves M generated by the microwave oscillator 11 resonate within the cavity 14A and are irradiated onto the object to be measured 1 through the opening 14B.

[0056] Next, in this state, the intensity of the magnetic field H generated from the magnet 12 is swept using the modulation coil 13. When the energy difference ΔE between the α spin and β spin caused by the magnetic field H matches the energy of the microwave M, absorption of the microwave M occurs. Since the intensity of the magnetic field H at which absorption of microwave M occurs can be confirmed in a prior study, the sweep range of the magnetic field H intensity can be narrow. For example, if the measurement target 1 is a carbon fiber composite material, absorption of microwave M occurs at 319.5 mT, so the magnetic field is swept within a range of ±2 mT from 319.5 mT.

[0057] The microwave M reflected by the object being measured 1 is detected by the detector 16A of the detection device 16. At a predetermined magnetic field strength, the microwave M is absorbed by the object being measured 1, and therefore the absorption spectrum of the microwave M is obtained.

[0058] In the load application step S22, a load is applied to the object to be measured 1. One cycle consists of applying and releasing the load to the object to be measured 1, and the load is applied to the object to be measured 1 multiple times. The measurement step S21 is performed every certain number of load applications.

[0059] Next, in evaluation step S3, the data detected in detection step S2 is analyzed, and the degradation of the measurement target 1 is evaluated based on the detected spin number of the measurement target 1. Evaluation step S3 is performed, for example, on the computer 16C of the detection device 16. Evaluation step S3 includes, for example, a graphing step S31, a fitting step S32, and a lifetime estimation step S33.

[0060] First, the number of spins included in the measurement target 1 is determined each time the measurement process S21 is performed. The number of spins in the measurement target 1 can be determined from the absolute value of the integrated intensity obtained by integrating the original signal detected by the electron spin resonance apparatus 10 twice.

[0061] In graphing step S31, the horizontal axis represents the number of times the load is applied to the object being measured 1 (N), and the vertical axis represents the normalized spin number of the object being measured 1 (N). spin (N) / N spin Create a graph with (0). spin(N) is the number of spins of the object being measured 1 after the load has been applied N times, spin (0) is the number of spins (N) of the object to be measured before load application. spin (0)) The number of spins of the object to be measured before load application (N spin (0)) depends on the material of the object being measured 1, so by normalizing it, the material dependence can be eliminated and the spin state that occurs when a load is applied can be extracted.

[0062] In fitting step S32, the prepared graph is fitted. The fitting is performed using the following formula (1). N spin (N) / N spin (0) = A log 10 (N+1)+1…(1) In equation (1), A is a constant.

[0063] In the life estimation process S33, the critical value obtained in the critical value calculation process S15 is substituted into the left side of equation (1). For example, 1.85 is substituted when determining the number of loads until delamination occurs, and 2.0 is substituted when determining the number of loads until complete failure occurs. The constant A can also be determined from graph fitting. Therefore, by substituting these values, the only variable is N, and the number of load applications N until the measurement target 1 fails (delamination or complete failure) can be estimated.

[0064] Up to this point, we have described a first method for estimating the lifespan of the object to be measured 1, but the method for estimating the lifespan is not limited to this example. Figure 4 is a second flowchart of the degradation evaluation method according to the first embodiment.

[0065] The degradation evaluation method based on the second flowchart includes, for example, a preparation step S1', a detection step S2', and an evaluation step S3'. The preparation step S1' is a preparatory step performed in advance before evaluating the actual measurement target 1. The detection step S2' and the evaluation step S3' are actual measurement steps in which the actual measurement target 1 is measured.

[0066] Preparation step S1' includes, for example, a reference sample preparation step S11, a reference sample measurement step S12, a load application step S13, a lifetime measurement step S14, and an analysis step S16. The reference sample preparation step S11, the reference sample measurement step S12, the load application step S13, and the lifetime measurement step S14 are the same as in the first flow.

[0067] In analysis step S16, the relationship between the number of loads applied to the reference sample and the electron spin resonance signal of the reference sample measured in reference sample measurement step S12 is analyzed. Analysis step S16 includes, for example, a graphing step S17 and a fitting step S18.

[0068] In graphing step S17, the horizontal axis represents the number of times the load was applied to the reference sample (N), and the vertical axis represents the normalized spin number of the reference sample (N'). spin (N) / N' spin Create a graph with (0). N' spin (N) is the spin number of the reference sample after N loads have been applied, and N' spin (0) is the spin number (N) of the reference sample before load application. spin (0))

[0069] In fitting step S18, the prepared graph is fitted. The fitting is performed using the following equation (2). N' spin (N) / N' spin (0) = A'log 10 (N+1)+1…(2)

[0070] In equation (2), A' is a constant. The graph produced in graphing step S17 differs depending on the load level S. The load level S is the maximum load P max Standard load P t This is obtained by dividing by the (initial damage confirmation load). By performing fitting process S18, the constant A' for each load level S can be determined.

[0071] In detection step S2', the actual object to be measured 1 is measured. Detection step S2' is performed, for example, using the electron spin resonance apparatus 10 described above. In detection step S2', microwaves M are irradiated onto the object to be measured 1, and a magnetic field H is applied to the irradiation surface of the object to be measured that is irradiated with microwaves M, and the electron spin resonance signal of the object to be measured 1 is detected by electron spin resonance. The detection method in detection step S2' is the same as that of the actual measurement step S21 described above.

[0072] Next, in evaluation step S3', the data detected in detection step S2' is analyzed, and the degradation of the object to be measured 1 is evaluated based on the number of spins of the object to be measured 1 that was detected. Evaluation step S3' is performed, for example, on the computer 16C of the detection device 16. Evaluation step S3' includes, for example, an estimation step S34 for the number of load applications and an estimation step S35 for the lifespan.

[0073] First, the number of spins in the object being measured 1 is determined. The number of spins in object being measured 1 can be determined from the absolute value of the integrated intensity obtained by integrating the original signal detected by the electron spin resonance spectrometer 10 twice.

[0074] Next, in the S34 process for estimating the number of load applications, the spin number of the object to be measured 1 is calculated using the formula (2) N'. spin Substitute this into (N). Also, the number of spins in the initial state (new condition) of the object being measured 1, which was measured in advance, is N' in equation (2). spin Substitute this into (0). The constant A' is determined by finding the load level S applied to the object being measured 1. Substituting the above value into equation (2), the number of times the load was applied to the object being measured 1, N, can be found. In this procedure, the number of times the load was applied to the object being measured 1, N, can be estimated from the electron spin resonance results.

[0075] As mentioned above, in the life measurement step S14, the number of load applications required for the reference sample to fail is determined. The relationship between the number of load applications and the spin number in the reference sample is approximately the same as the relationship between the number of load applications and the spin number in the measurement target 1. Therefore, the number of load applications required for delamination, as determined in the life measurement step S14, is approximately the same as the number of load applications required for delamination in the measurement target 1, and the number of load applications required for complete failure, as determined in the life measurement step S14, is approximately the same as the number of load applications required for complete failure in the measurement target 1.

[0076] Therefore, in the life estimation step S35, the remaining life of the measurement target 1 can be estimated by subtracting the number of times the load was applied to the measurement target 1, which was estimated in the estimation step S34, from the number of times the load was applied to the reference sample, which was determined in the life measurement step S14, until it broke.

[0077] The method using the first flow is highly reliable because it performs fitting using actual measured values. The method using the second flow is suitable for measuring objects whose condition is unknown, as it only requires one measurement of object 1.

[0078] As described above, the electron spin resonance apparatus 10 according to this embodiment does not require a high Q value because it limits the measurement target 1, thus enabling miniaturization and simplification of the configuration. Furthermore, since the electron spin resonance apparatus 10 according to this embodiment applies a magnetic field H and microwaves M from one direction toward the measurement target 1, measurement is possible regardless of the shape and size of the measurement target 1.

[0079] Furthermore, the degradation evaluation method according to this embodiment can evaluate the degradation of carbon fiber composite materials using electron spin resonance. In addition, the degradation evaluation method according to this embodiment can estimate the number of load applications and the remaining lifespan by conducting preliminary studies using a reference sample.

[0080] An example of an electron spin resonance apparatus 10 and a degradation evaluation method has been shown so far. However, the present invention is not limited to this embodiment.

[0081] For example, Figure 5 is a schematic perspective view of an electron spin resonance apparatus 10A according to the first modified example. The electron spin resonance apparatus 10A has a plurality of units U1.

[0082] Each of the multiple units U1 includes a microwave oscillator 11, a magnet 12, a modulation coil 13, and a cavity resonator 14. Each of the microwave oscillator 11, magnet 12, modulation coil 13, and cavity resonator 14 is the same as described above.

[0083] The arrangement of the multiple units U1 is not particularly limited. The multiple units U1 can be arranged, for example, in a line or an array. The multiple units U1 are connected, for example, to a single power supply 15. The high frequency generated by the power supply 15 is branched by wiring and propagated to each microwave oscillator 11.

[0084] The electron spin resonance apparatus 10A according to the first modified example has multiple units U1, so it can measure a wide area at once.

[0085] For example, Figure 6 is a schematic perspective view of an electron spin resonance apparatus 10B according to a second modified example. The electron spin resonance apparatus 10B has a plurality of units U2.

[0086] Each of the multiple units U2 includes a microwave oscillator 11, a magnet 12, a modulation coil 13, and a cavity resonator 14. Each of the microwave oscillator 11, magnet 12, modulation coil 13, and cavity resonator 14 is the same as described above. Some of the multiple units U2 share at least one of the microwave oscillator 11, magnet 12, and modulation coil 13 with other units U2. Figure 6 shows an example in which the magnet 12 is shared by multiple units U2. In this case, the magnets 12 of adjacent units U2 are integrated.

[0087] The electron spin resonance apparatus 10B according to the first modified example has multiple units U2, allowing for measurements over a large area to be taken simultaneously. Furthermore, because the units U2 are connected to each other, it is easy to handle. [Examples]

[0088] (Experimental Example 1) Figure 7 is an illustrative diagram of the measurement sample from Experimental Example 1. In Experimental Example 1, a carbon fiber composite material 31 of a predetermined size was attached to a polyethylene terephthalate (PET) substrate 33 with double-sided tape 32 and sealed in a sample tube 34 with air.

[0089] The carbon fiber composite material 31 used was Toray Industries, Inc.'s T700S [0 / 90_4 / 0] (6 layers). This carbon fiber composite material 31 is CFRP. The carbon fiber composite material 31 was prepared using a sample measuring 10 mm × 150 mm × 1.2 mm. 3 A load was applied multiple times. The load conditions were 950N, 2Hz, R0.1 sine wave.

[0090] Three sample sizes were prepared for measurement: Sample 1, cut to 2mm x 1mm (3.0mg); Sample 2, cut to 2mm x 0.9mm (2.7mg); and Sample 3, cut to 2mm x 0.27mm (0.8mg).

[0091] Then, a magnetic field H was applied from a direction perpendicular to the side of the sample tube 34, and electron spin resonance was performed. The measurement was carried out at room temperature.

[0092] Figure 8 shows the measurement results for Experimental Example 1. Almost no differences were observed in the intensity, g-factor, or ESR linewidth of the ESR signals for Sample 1, Sample 2, and Sample 3. This indicates that the number of spins present in the carbon fiber composite material in its initial state is significantly greater than the number of spins generated at the cut surface due to cutting or other processes. In other words, evaluation is possible regardless of the processing size, and the evaluation of Measurement Target 1 can be performed based on the reference sample.

[0093] (Experimental Example 2) In Experimental Example 2, the dependence of the electron spin resonance signal on the number of loads applied to the carbon fiber composite was evaluated, using the same carbon fiber composite material as in Experimental Example 1.

[0094] The loading conditions applied to the sample were the same as in Example 1, with the number of loading cycles being 0 and 10.3 10 times 4 10 times 5 10 times 6 Each sample was prepared separately.

[0095] Figure 9 is a graph of the original data of the electron spin resonance signal obtained in Experimental Example 2, and Figure 10 is a graph of the original data integrated once. As shown in Figures 9 and 10, the spectrum clearly changed depending on the number of loadings. For example, the ESR signal intensity at the g factor corresponding to the peak of the single-load integrated graph (Figure 10) increased as the number of loadings increased. Also, the ESR full width at half maximum (FMAX) of the single-load integrated graph (Figure 10) narrowed as the number of loadings increased.

[0096] The number of load cycles is 10 6 In the range of less than 1:1 load, the rigidity of the sample did not decrease significantly, and no visible transverse cracks were observed. In other words, material degradation can be detected even under conditions where these obvious degradations are not observed due to the application of weak loads.

[0097] Figure 11 is a graph showing the dependence of the number of spins on the number of loading cycles obtained in Experimental Example 2. As shown in Figure 11, the spin concentration per unit mass of the carbon fiber composite material increased monotonically with increasing loading cycles, and a logarithmic dependence with respect to the number of loading cycles was observed. This is thought to be because, as the carbon fiber composite material fatigues, molecular chain breakage or cross-linking structure failure occurs, generating spins (radicals).

[0098] Figure 12 is a graph showing the dependence of the ESR full width at half maximum (FMAX) obtained in Experimental Example 2 on the number of loading cycles. The ESR FMAX decreased monotonically with increasing loading cycles. The ESR FMAX is a parameter proportional to the interspin magnetic dipole interaction. A decrease in the ESR FMAX means an increase in the average distance between spins. This result is thought to reflect the degradation of the carbon fiber composite material and the increase in internal voids.

[0099] (Experimental Example 3) In Experimental Example 3, the dependence of carbon fiber composites on the spin number load conditions was evaluated using carbon fiber reinforced polymer (CFRP) made with the same thermosetting resin as in Experimental Example 1, and carbon fiber reinforced polymer (CFRTP) made with thermoplastic resin.

[0100] The first sample was subjected to the same conditions as in Experimental Example 2. The load level S for the first sample was set to 0.25. The second sample was a carbon fiber composite material (CFRTP) using thermoplastic resin, and twice the load level of Experimental Example 2 was applied. The load level S for the second sample was set to 0.5.

[0101] Figure 13 is a graph showing the dependence of the number of spins on the number of loads obtained in Experimental Example 3. Regardless of the load level S or the type of carbon fiber composite material, the number of spins tended to increase logarithmically. Figure 14 shows the graph of Figure 13 multiplied by N. spin (N) = a log 10 (N+1)+N spin The graphs were fitted using (0), and all of them were fitted appropriately. [Explanation of symbols]

[0102] 1...Measurement target, 2...Penetration area, 10, 10A, 10B...Electron spin resonance spectrometer, 11...Microwave oscillator, 12...Magnet, 13...Modulation coil, 14...Cavity resonator, 14A...Cavity, 14B...Aperture, 15...Power supply, 16...Detection device, 16A...Detector, 16B...Amplifier, 16C...Computer, 31...Carbon fiber composite material, 32...Double-sided tape, 33...Substrate, 34...Sample tube, S1, S1'...Preparation process S2, S2'... Detection process, S3, S3'... Evaluation process, S11... Reference sample preparation process, S12... Reference sample measurement process, S13, S22... Load application process, S14... Life measurement process, S15... Critical value calculation process, S16... Analysis process, S17, S31... Graphing process, S18, S32... Fitting process, S21... Actual measurement process, S33, S34, S35... Estimation process, U1, U2... Unit

Claims

1. It comprises a microwave oscillator, a magnet, a modulation coil, and a cavity resonator having an aperture, The microwaves generated by the microwave oscillator resonate in the cavity resonator and are irradiated from the opening toward the object to be measured located outside the opening. The magnet applies a magnetic field toward the irradiation surface of the object to be measured that is irradiated with microwaves, The modulation coil modulates the intensity of the magnetic field or the frequency of the microwave applied toward the irradiation surface of the object to be measured. The measurement target is the penetration region into which the microwave is irradiated and penetrates, 10 １１ Including spins of 1 / g or more, An electron spin resonance apparatus in which the microwave oscillator and the magnet are positioned opposite the object to be measured and do not sandwich the object to be measured.

2. The electron spin resonance apparatus according to claim 1, wherein the object to be measured is a carbon fiber composite material.

3. The electron spin resonance apparatus according to claim 1, wherein the modulation coil sweeps the magnetic field within a range of ±2 mT with respect to 319.5 mT.

4. The electron spin resonance apparatus according to claim 1, which is portable and can be installed on a measurement target of any shape.

5. It has multiple units, The electron spin resonance apparatus according to claim 1, wherein each of the plurality of units includes the microwave oscillator, the magnet, the modulation coil, and the cavity resonator.

6. The electron spin resonance apparatus according to claim 5, wherein some of the multiple units share at least one of the microwave oscillator, the magnet, and the modulation coil.

7. A degradation evaluation method using an electron spin resonance apparatus as described in claim 1, A detection step involves irradiating the object to be measured with microwaves, applying a magnetic field to the irradiation surface of the object to be measured that is irradiated with microwaves, and detecting the electron spin resonance signal of the object to be measured by electron spin resonance. An evaluation step of evaluating the degradation of the object to be measured from the electron spin resonance signal, Prior to the detection step, a preparatory step is performed to determine in advance the relationship between the degradation of the reference sample and the electron spin resonance signal of the reference sample using a reference sample having the same configuration as the object to be measured. The preparation step includes a step of determining a critical value by dividing the spin number of the reference sample at the time a load that causes the reference sample to break is applied by the spin number of the reference sample before the load is applied. The aforementioned evaluation process is, The horizontal axis represents the number of times the load is applied to the object being measured (N), and the vertical axis represents the normalized spin number of the object being measured (N). ｓｐｉｎ (N) / N ｓｐｉｎ The process involves fitting the graph (0)) using the following formula (1), The process includes the step of substituting the critical value into the left side of the following equation (1) to estimate the number of times the load applied to the object to be measured will cause it to break, N ｓｐｉｎ (N) / N ｓｐｉｎ (0) = Alog １０ (N+1)+1…(1) In equation (1), N ｓｐｉｎ (N) is the number of spins of the object being measured after the load has been applied N times, where N ｓｐｉｎ A degradation evaluation method in which (0) is the number of spins of the object to be measured before load application, and A is a constant.

8. A degradation evaluation method using an electron spin resonance apparatus as described in claim 1, A detection step involves irradiating the object to be measured with microwaves, applying a magnetic field to the irradiation surface of the object to be measured that is irradiated with microwaves, and detecting the electron spin resonance signal of the object to be measured by electron spin resonance. An evaluation step of evaluating the degradation of the object to be measured from the electron spin resonance signal, Prior to the detection step, a preparatory step is performed to determine in advance the relationship between the degradation of the reference sample and the electron spin resonance signal of the reference sample using a reference sample having the same configuration as the object to be measured. The preparation process includes a step of fitting a graph with the number of times of applying load (N) to the reference sample on the horizontal axis and the normalized spin number (N' ｓｐｉｎ (N) / N' ｓｐｉｎ (0)) on the vertical axis using the following formula (2). N’ ｓｐｉｎ (N) / N’ ｓｐｉｎ (0)=A’log １０ (N+1)+1…(2) In equation (2), N' ｓｐｉｎ (N) is the number of spins of the reference sample after N loads have been applied, and N' ｓｐｉｎ A degradation evaluation method in which (0) is the spin number of the reference sample before load application and A' is a constant.

9. The evaluation step involves using the number of spins detected in the detection step as N' in formula (2). ｓｐｉｎ The deterioration evaluation method according to claim 8, further comprising an estimation step of substituting (N) to estimate the number of times the load was applied to the object to be measured.

10. The preparation step includes a step of determining the number of times the load applied will cause the reference sample to break. The degradation evaluation method according to claim 9, wherein the evaluation step includes a step of determining the remaining lifespan of the measurement target by subtracting the number of times the load was applied to the measurement target, estimated in the estimation step, from the number of times the load was applied that caused the reference sample to break.

11. The degradation evaluation method according to claim 7, wherein the object to be measured is a carbon fiber composite material.

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