Degradation diagnostic equipment, degradation diagnostic method program, computer program product, recording medium

Abstract

To obtain a deterioration diagnostic device that can non-destructively diagnose the corrosion of objects whose surfaces may corrode. [Solution] The deterioration diagnostic device is a deterioration diagnostic device comprising at least one processor, wherein the processor measures the change in intensity of light of a specific frequency propagating through the object while rotating the polarization of the light, and evaluates the thickness of the corrosion formed on the object based on the rotation angle of the measured polarization of the light and the intensity of the light.

Description

[Technical Field]

[0001] The present disclosure relates to a deterioration diagnosis apparatus, a deterioration diagnosis method program, a computer program product, and a recording medium . [Background Art]

[0002] Patent Document 1 discloses a non-destructive inspection apparatus that detects defects in wood or the like having a fibrous structure by irradiating the wood or the like with electromagnetic waves. The conventional technology disclosed in Patent Document 1 performs transmission or reflection imaging in a substance using polarized electromagnetic waves, thereby obtaining transmission characteristics reflecting the anisotropy inside the substance. This makes it possible to detect the grain direction of wood and detect structural defects such as the presence or absence of wormholes, dead knots, cracks, and rot in wood. [Prior Art Document] [Patent Document]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2008-268164 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Here, for example, when corrosion progresses on the surface of a catenary used in railway lines and causes thickness reduction, the strength of the catenary decreases, and as a result, the catenary may break. In order to prevent such breakage, introduction of a method for non-destructively diagnosing the progress of deterioration of catenaries is required. However, the conventional technology disclosed in Patent Document 1 does not premise deterioration diagnosis of an object such as a catenary whose surface may corrode. Therefore, there is room for improvement in non-destructively diagnosing an object whose surface may corrode.

[0005] An object of the present disclosure is to obtain a deterioration diagnosis apparatus, a deterioration diagnosis method program, a computer program product, and a recording medium that non-destructively diagnose an object whose surface may corrode. [Means for solving the problem]

[0006] A first aspect of the technology of the present disclosure is a degradation diagnostic device comprising at least one processor, wherein the processor measures a change in the intensity of light of a specific frequency propagating through an object while rotating the polarization of the light, and evaluates the thickness of corrosion formed on the object based on the measured rotation angle of the polarization of the light and the intensity of the light.

[0007] A second aspect of the technology of the present disclosure is a degradation diagnostic device of the first aspect, wherein the processor measures the change in intensity when a specific device automatically rotates the polarization of the light.

[0008] A third aspect of the technology of this disclosure is a degradation diagnostic device of the second aspect, wherein the processor measures the change in intensity when the specific device rotates the polarization of the light incident on the object.

[0009] A fourth aspect of the technology of this disclosure is a degradation diagnostic device of the second aspect, wherein the processor measures the change in intensity when the specific device rotates the polarization of the light emitted from the object.

[0010] A fifth aspect of the technology of this disclosure is the degradation diagnostic device of the first aspect, wherein the polarization of the light is S-polarized.

[0011] A sixth aspect of the technology of this disclosure is a degradation diagnostic device of the fifth aspect, wherein the specific frequency is a specific frequency between 10 GHz and 200 GHz.

[0012] A seventh aspect of the technology of this disclosure is a degradation diagnostic device of the sixth aspect, wherein the specific frequency is a frequency between 40 GHz and 140 GHz.

[0013] An eighth aspect of the technology of this disclosure is a deterioration diagnosis method in which a computer performs the following actions: measuring the change in intensity of light of a specific frequency propagating through an object while rotating the polarization of the light, and evaluating the thickness of corrosion formed on the object based on the measured rotation angle of the polarization of the light and the intensity of the light.

[0014] The ninth aspect of the technology of this disclosure is a program that causes a computer to perform the following actions: measure the change in intensity of light of a specific frequency propagating through an object while rotating the polarization of the light, and evaluate the thickness of corrosion formed on the object based on the measured rotation angle of the polarization of the light and the intensity of the light.

[0015] A tenth aspect of the technology of this disclosure is a computer program product that causes a computer to perform the following actions: measure the change in intensity of light of a specific frequency propagating through an object while rotating the polarization of the light, and evaluate the thickness of corrosion formed on the object based on the measured rotation angle of the polarization of the light and the intensity of the light.

[0016] An eleventh aspect of the technology of this disclosure is a computer-readable recording medium on which a program is recorded that causes a computer to perform the following actions: measure the change in intensity of light of a specific frequency propagating through an object while rotating the polarization of the light, and evaluate the thickness of corrosion formed on the object based on the measured rotation angle of the polarization of the light and the intensity of the light. [Effects of the Invention]

[0017] According to this disclosure, a deterioration diagnostic device, a deterioration diagnostic method program, a computer program product, and a recording medium are obtained for non-destructively diagnosing objects whose surfaces may corrode. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a diagram showing an example configuration of a deterioration diagnosis system 100 including a deterioration diagnosis device 200 according to an embodiment of this disclosure. [Figure 2A]FIG. 2A is a diagram showing a configuration example of the reflecting mirror 204. [Figure 2B] FIG. 2B is a diagram showing a configuration example of the reflecting mirror 204. [Figure 3A] FIG. 3A is a diagram showing a hardware configuration example of the deterioration diagnosis apparatus 200. [Figure 3B] FIG. 3B is a diagram showing functional blocks of the deterioration diagnosis apparatus 200 according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram showing the relationship between the intensity of terahertz waves of three types of frequencies with different values (terahertz intensity) and the number of corrosion days. [Figure 5] FIG. 5 is a diagram for explaining the consideration of the skin effect of the object 300. [Figure 6] FIG. 6 is a diagram for explaining the consideration of the skin effect of the object 300. [Figure 7] FIG. 7 is a diagram for explaining the consideration of the skin effect of the object 300. [Figure 8] FIG. 8 is a diagram showing the permittivity of the corroded material 300a with respect to terahertz waves. [Figure 9] FIG. 9 is a diagram for supplementing an example of a waveguide. [Figure 10] FIG. 10 is a diagram showing detected intensity when the rotation angle of the polarization plane (polarization angle) is changed in the deterioration diagnosis system 100 shown in FIG. 1. [Figure 11] FIG. 11 is a diagram showing detected intensity when the rotation angle of the polarization plane (polarization angle) is changed in the deterioration diagnosis system 100 shown in FIG. 1. [Figure 12] FIG. 12 is a diagram for supplementing the reflection and absorption of terahertz waves on a metal surface. [Figure 13] FIG. 13 is a diagram for supplementing the reflection and absorption of terahertz waves on a metal surface. [Figure 14] FIG. 14 is a diagram for explaining the relationship among the thickness of rust, the rotation angle of the polarization plane, and the propagation intensity. [Figure 15] FIG. 15 is a flowchart for explaining the operation of the deterioration diagnosis apparatus 200 of the present disclosure. [Modes for carrying out the invention]

[0019] (Premise) Conductors such as railway overhead lines and electrical wiring for public facilities are used in various locations both domestically and internationally, and in some cases, these conductors may be in use for more than 30 years without being replaced. To replace such deteriorated conductors efficiently, it is effective to diagnose the deterioration of the conductors, but currently, it is difficult to properly diagnose the deterioration of conductors. This can make reuse difficult, as it may involve collecting long lengths of conductors and, if no deterioration is found after diagnosis, re-laying the conductors. Furthermore, in the case of electrical cables that are covered with, for example, polyvinyl chloride (PVC), if the cable is deteriorating, the PVC must be removed, and in particular, PVC is difficult to dispose of, so it may need to be landfilled, resulting in a lot of waste in terms of cost and environmental impact. It should be noted that the material used to cover electrical cables is not limited to PVC, and may also include, for example, high-density polyethylene. On the other hand, there are many railway overhead lines that have been left unreplaced for decades or more, and the risk of railway accidents cannot be ruled out. In the current situation where there is no technology to properly inspect electrical cables and other conductors, the time and manpower costs increase when many iron materials need to be replaced. Furthermore, when replacement work is performed at high places or in confined spaces, the conductors are inspected visually, making it difficult to obtain evidence of conductor deterioration. Power companies and railway companies, in particular, which use many conductors in their infrastructure, recognize the need for technology that can be used on-site and quantitatively diagnose the deterioration of conductors (iron wires, steel wires, copper wires, etc.) non-destructively. As a quantitative evaluation in deterioration diagnosis, it is desirable to be able to determine the degree of deterioration by, for example, how much the output energy has decreased relative to the energy input to the conductor. However, since there are many possible causes of conductor deterioration, and many other factors besides conductor deterioration, such as the surrounding environment and weather conditions, can also be considered, it is difficult to conclude that changes due to output energy are due to deterioration. Therefore, it is also desirable to be able to obtain qualitative changes as a separate phenomenon due to the presence or absence of conductor deterioration or corrosion products (corrosive materials). Therefore, it may be necessary to be able to obtain multiple parameters for the phenomena caused by degradation, in addition to the decrease in output energy, and to be able to clearly define the boundaries between them.

[0020] (Summary of the invention) The present inventors have found that the above problems can be solved by the deterioration diagnostic device, deterioration diagnostic method, etc., described below. The deterioration diagnostic device of this disclosure focuses on the fact that the characteristics (polarization angle - detection intensity) of terahertz waves or terahertz light (hereinafter referred to as terahertz waves), which are a type of electromagnetic wave, propagating through a conductor correlate with the corrosion state of the surface of the conductor (rust thickness, rust depth, etc.), and is configured to diagnose the deterioration state of the conductor. This makes it possible to know the corrosion state on the conductor. For example, if the thickness of the conductor decreases due to corrosion, the strength of the conductor decreases. For example, if the cross-sectional area is halved, the strength is halved. Therefore, depending on the strength setting of the conductor's use, it is possible to estimate and determine the timing of conductor replacement from the state of the corrosion layer formed on the conductor. As a method for detecting the corrosion state of the conductor, the degree of decrease in the intensity of the detected terahertz waves and the polarization rotation state can be used. As terahertz waves propagate over long distances through conductors, their output decreases. However, because terahertz waves propagate easily through corroded layers, the degree of output decrease is reduced. Therefore, by evaluating this degree, the progression of corrosion can be quantitatively assessed. In addition to the decrease in output, changes in polarization originating from metal oxides were observed in devices that control the polarization of radio waves and light. The degree of corrosion can be evaluated by observing the change in polarization depending on the amount of metal oxides. Furthermore, phenomena have been observed where terahertz waves do not propagate for certain polarization states, or where the terahertz waves attenuate so rapidly that they are difficult to detect with normal inspection (diagnosis). These phenomena do not change simply due to the distance between the light source and detector, and are therefore not thought to originate from phenomena other than degradation. Therefore, the degradation diagnostic method disclosed in this disclosure can be used as a method to detect only the degradation status of materials such as conductors, without being affected by the decrease in output energy due to the distance to the measurement target, the surrounding conditions, etc., through inspection (diagnosis) using this information.

[0021] (Details of the invention) Embodiments of this disclosure will be described below with reference to the attached drawings. To facilitate understanding of the description, the same reference numerals are used for the same components in each drawing whenever possible, and redundant explanations are omitted.

[0022] Figure 1 shows an example configuration of a deterioration diagnosis system 100 including a deterioration diagnosis device 200 according to an embodiment of this disclosure. The deterioration diagnosis system 100 may use electromagnetic waves of a specific frequency to non-destructively and non-contactually diagnose the state of corrosion occurring on the surface of an object 300.

[0023] Electromagnetic waves of a specific frequency may be interpreted as waves or light of a specific frequency. Specifically, electromagnetic waves of a specific frequency may be interpreted as waves or light of a specific frequency that propagate through space at the speed of light while the electric and magnetic fields influence each other. Electromagnetic waves of a specific frequency may have properties intermediate between radio waves and light waves, and may be interpreted as possessing both the penetrating properties of radio waves and the directional properties of light waves. A specific frequency may be interpreted as a specific value (frequency) in the frequency range intermediate between radio waves and light waves, for example, within the band from 10 GHz to 10 THz. Electromagnetic waves of a specific frequency may be interpreted as terahertz waves, terahertz light, etc. In the following explanation, for convenience, electromagnetic waves of a specific frequency may be referred to as terahertz waves or terahertz light.

[0024] The object 300 can be interpreted as a long member on which corrosion may occur on the surface, and may include, for example, members made of metal, copper, silver, aluminum, brass, etc. The object 300 may include not only solid members without cavities in the cross-section, but also hollow members with cavities in the cross-section. Specifically, the object 300 may include trolley wires, suspension wires, building cables, reinforcing bars, pipes, etc.

[0025] The trolley wire can be interpreted as a contact wire that contacts a pantograph installed on a moving body such as a railway vehicle or bogie, and supplies power to these moving bodies via the pantograph. The suspension wire can be interpreted as a wire installed above the trolley wire and used to suspend the trolley wire using a hanger.

[0026] Construction cables may include, for example, cables connecting the main towers of a suspension bridge, and cables supporting the structural elements of a building (such as flooring and roofing materials). Reinforcement bars may be interpreted as metal members used to provide strength, durability, etc., to concrete structures. Piping may include metal liquid pipes, gas pipes, etc., on which corrosion may occur on the surface.

[0027] Diagnosing the state of corrosion non-destructively and non-contact can be interpreted as evaluating the thickness of the corrosive material 300a formed on the surface of the object 300. Specifically, diagnosing the state of corrosion non-destructively and non-contact can be interpreted as measuring the change in intensity of light of a specific frequency propagating through the object while rotating the polarization of the light, and evaluating the thickness of the corrosive material 300a formed on the object based on the rotation angle of the measured polarization of the light and the intensity of the light. Light of a specific frequency can be interpreted as electromagnetic waves of a specific frequency.

[0028] The surface of object 300 may be interpreted as the radially outer surface (outer circumferential surface) of object 300 if object 300 is a solid structure. The surface of object 300 may be interpreted as at least one of the radially outer surface (outer circumferential surface) and the radially inner surface (inner circumferential surface) of object 300 if object 300 is a hollow structure.

[0029] The deterioration diagnosis system 100 may include a deterioration diagnosis device 200, an irradiator 201, a jig 202, a reflector 203, a reflector 204, a jig 205, and a detector 206.

[0030] (Irradiator 201) The irradiator 201 may irradiate the object 300 with terahertz waves generated by the light source via the jig 202. The light source may be a Gunn diode, an INPAT diode, or the like, that oscillates at a fixed frequency. However, the light source is not limited to these, and any device capable of generating terahertz waves is acceptable.

[0031] (Jig 202) The jig 202 may rotate the polarization of the terahertz waves output from the irradiator 201 in order to evaluate the thickness of the corroded material 300a. The jig 202 may rotate the polarization plane of the terahertz waves from 0° to 360° according to control commands output from the degradation diagnosis device 200. For example, the jig 202 may change the polarization angle of the terahertz waves at specific intervals, such as 5°, 10°, 15°, etc. The jig 202 may be configured integrally with the irradiator 201.

[0032] (Reflector 203) The reflecting mirror 203 can be interpreted as a mirror that reflects and transmits terahertz waves, whose polarization angle has been changed by the jig 202, to the object 300. The reflecting mirror 203 is, for example, a rectangular (square-shaped) plate-shaped mirror. The reflecting mirror 203 only needs to be capable of reflecting and transmitting terahertz waves, whose polarization angle has been changed by the jig 202, to the object 300, and its shape is not limited to a rectangular (square-shaped) plate.

[0033] The reflecting mirror 204 can be interpreted as a mirror that reflects and transmits terahertz waves that have passed through the object 300 toward the jig 205. The reflecting mirror 204 may be, for example, a parabolic mirror, specifically a mirror with a bowl-shaped concave curved surface, a so-called ellipsoidal mirror.

[0034] (Modification 1 of the reflector 204) The reflecting mirror 204 may be a rectangular (square-shaped) plate-shaped mirror, as shown in Figure 2A. By using the reflecting mirror 204 shown in Figure 2A in the deterioration diagnosis system 100, the introduction cost of the deterioration diagnosis system 100 can be reduced compared to using a mirror with a special shape as the reflecting mirror 204.

[0035] (Modified example 2 of the reflector 204) The reflector 204 may be a mirror with a notch CO formed on one of its four sides, as shown in Figure 2B. The material of the reflector 204 shown in Figure 2B is, for example, aluminum. It is known that terahertz waves do not propagate across the entire outer surface of the suspension wire, which is an example of an object 300, in a cross section perpendicular to the extension direction of the suspension wire, but rather propagate in a specific region R on the outer surface of the suspension wire. As shown in Figure 2B, any point in the region R between the first end 301 of the object 300 and the second end 302 on the opposite side of the first end 301 of the object 300 may be inserted into the notch CO of the reflector 204, and the outer surface of the inserted object 300 may be brought into contact with the wall surface WS forming the notch CO, that is, the wall surface WS forming a concave recess. By using a mirror with a notched CO, the corrosion state of the object to be inspected (object 300) can be inspected without having to disconnect one end (second end 302) of the object from the existing equipment.

[0036] The reflector 203 shown in Figure 1 may be configured in the same way as the reflector 204 shown in Figure 2B. This allows the corrosion condition of the object 300 to be easily inspected without having to disconnect the other end of the object 300 on the reflector 203 side (the first end 301 shown in Figure 2B) from the existing equipment. If both the reflector 203 and the reflector 204 shown in Figure 1 are configured in the same way as the reflector 204 shown in Figure 2B, the corrosion condition of the object 300 can be easily inspected without having to disconnect the object 300 from the existing equipment, making it even easier to inspect the corrosion condition of the object 300.

[0037] (Jig 205) Returning to Figure 1, the jig 205 may, for example, be equipped with a waveguide called a horn antenna having a polarization function, and rotate the polarization of the terahertz waves reflected by the reflector 204. The jig 205 may rotate the polarization plane of the terahertz waves from 0° to 360° by a control command output from the degradation diagnosis device 200. For example, the jig 205 may change the polarization angle of the terahertz waves at specific angle intervals, such as 5°, 10°, 15°, etc. The jig 205 may be configured integrally with the detector 206. In addition to the waveguide described above, the jig 205 may also be equipped with a patch antenna, which is a type of planar antenna having a simple structure in which a metal plate (conductor) is arranged on a substrate. Patch antennas are small and lightweight, have low manufacturing costs, and many have linear polarization, but circular polarization is also possible, and they are widely used in the field of communications (Wi-Fi, GPS, satellite communications) and radar.

[0038] The detector 206 detects the intensity of terahertz waves whose polarization plane has been rotated by the jig 205. As mentioned above, a Schottky barrier diode can be used as the detector.

[0039] The degradation diagnostic device 200 may, for example, measure the polarization angle of the terahertz wave, the intensity of the terahertz wave output to the object 300, and the intensity of the terahertz wave transmitted through the object 300 and input, and record the corresponding values ​​of the intensity of the terahertz wave output to the object 300 and the input terahertz wave for each of several polarization angles with different values. The degradation diagnostic device 200 may record the corresponding values ​​of the polarization angle of the terahertz wave and the detected intensity of the terahertz wave for both P-polarization (horizontal polarization, parallel polarization) and S-polarization (vertical polarization). The degradation diagnostic device 200 may use this information (detection intensity, polarization angle, etc.), that is, use the terahertz wave transmitted to the object 300 via the reflector 203, and then passed from the object 300 through the reflector 204 and detector 206 to evaluate the thickness of the corrosion formed on the object 300. Details of the configuration of the degradation diagnostic device 200 will be described later.

[0040] Next, the hardware configuration of the degradation diagnostic device 200 will be described with reference to Figure 3A. Figure 3A is a diagram showing an example of the hardware configuration of the degradation diagnostic device 200. The degradation diagnostic device 200 may include an input / output interface (I / F) 1, memory 2, and a processor 3. These may be connected via a bus 4 for communication.

[0041] The input / output interface 1 may receive, for example, information indicating the intensity of terahertz waves emitted from the irradiator 201 and information indicating the intensity of terahertz waves detected by the detector.

[0042] Memory 2 may store a degradation diagnosis program 2a for controlling the degradation diagnosis device 200. The processor 3 may execute specific processing by expanding the degradation diagnosis program 2a. The functions realized by the degradation diagnosis program 2a will be explained with reference to Figure 3B.

[0043] Figure 3B is a diagram showing the functional block of a degradation diagnosis device 200 according to an embodiment of this disclosure. The degradation diagnosis device 200 may include a measurement unit 31, an evaluation unit 32, and a control unit 33. These functions may be realized by the processor 3 shown in Figure 3A executing a degradation diagnosis program 2a.

[0044] (Measurement unit 31) The measurement unit 31 may measure the change in intensity (terahertz intensity) of light of a specific frequency (terahertz wave, terahertz light) propagating through the object 300 while rotating the polarization of the light.

[0045] (Another configuration example of the measurement unit 31 1) The measurement unit 31 may measure the change in the intensity of light of a specific frequency when a specific device (e.g., a jig 205) automatically rotates the polarization of light of a specific frequency. In this case, the measurement unit 31 may record the polarization angle and the intensity of light of the specific frequency in correspondence. This eliminates the need to manually set the polarization angle and the need to record the terahertz intensity for each set angle, thereby shortening the time required for degradation diagnosis.

[0046] (Another configuration example of the measurement unit 31 2) The measurement unit 31 may measure the change in intensity of light of a specific frequency when a specific device (e.g., jig 202) automatically or manually rotates the polarization of light of a specific frequency incident on the object 300. At this time, the measurement unit 31 may record the polarization angle and the intensity of light of the specific frequency in correspondence. This allows for rotation of the polarization of terahertz waves incident on the object 300 without rotating the polarization of the terahertz waves emitted from the object 300 on the jig 205 side, thus enabling more flexible deterioration diagnosis of the object 300.

[0047] (Other configuration examples of the measurement unit 31 3) The measurement unit 31 may measure the change in intensity of light of a specific frequency when a specific device (e.g., jig 205) automatically or manually rotates the polarization of light of a specific frequency emitted from the object 300. This allows for rotation of the polarization of terahertz waves emitted from the object 300 without rotating the polarization of the terahertz waves incident on the object 300 on the jig 202 side, thus enabling more flexible deterioration diagnosis of the object 300.

[0048] (Evaluation section 32) The evaluation unit 32 may evaluate the thickness of corrosion formed on the object based on the rotation angle of the polarization of the measured light of a specific frequency (e.g., terahertz waves, terahertz light) and the intensity of the light of a specific frequency. The evaluation unit 32 may, for example, refer to a table that associates multiple polarization rotation angles of terahertz waves with different values, multiple intensities of terahertz waves with different values, and the thickness of corrosion with different values, and evaluate the thickness of corrosion by calculating the thickness of corrosion corresponding to the measured rotation angle of the terahertz wave and the measured intensity of the terahertz wave.

[0049] (Control Unit 33) The control unit 33 may, for example, control at least one of the fixtures 202 and 205 to rotate the polarization plane of the terahertz waves from 0° to 360°. At this time, information regarding the polarization angle may be shared with the evaluation unit 32. This allows the evaluation unit 32 to evaluate the thickness of the corroded material in real time using the polarization angle and the corresponding intensity of the terahertz waves.

[0050] Next, referring to Figures 4 to 14, the principle, operation, and effects of deterioration diagnosis of the object 300 by the deterioration diagnosis device 200 will be explained.

[0051] Figure 4 shows the relationship between the intensity of terahertz waves at three different frequencies (terahertz intensity) and the number of days required for corrosion. The vertical axis in Figure 4 represents terahertz intensity, and the horizontal axis represents the number of days required for corrosion. Figure 4 shows the terahertz intensity when piano wire is used as a sample of 300 objects. The thick solid line represents the terahertz intensity at 140 GHz, the regular solid line represents the terahertz intensity at 100 GHz, and the dashed line represents the terahertz intensity at 40 GHz.

[0052] The terahertz intensity at 40 GHz shows a constant value even as corrosion progresses, for example from 0 to around 14 days (2 weeks), and then tends to increase slightly. This indicates that when the corrosion period is short, the difference in terahertz intensity at 40 GHz is not very noticeable. However, because the frequency is relatively low, it is thought that the terahertz intensity tends to increase once corrosion is definitely occurring.

[0053] The terahertz intensity at 100 GHz tends to increase as the number of corrosion days increases. At 100 GHz, the terahertz intensity is strongest and most stable relative to the number of days elapsed.

[0054] Furthermore, the terahertz intensity at an even higher 140 GHz tends to increase as the number of days of corrosion progresses, for example from day 0 to around 7 days (about one week), but then remains constant, and then shows a slight tendency to decrease after about 20 days. Overall, there is a tendency for the detected terahertz intensity to increase as the corrosion of the sample progresses. Thus, the terahertz intensity is unstable at 140 GHz. This is thought to be because the wavelength becomes shorter as the frequency increases, and as the number of days increases, light scattering increases, and the propagation intensity of terahertz waves decreases.

[0055] Based on these measurement results, it is considered that terahertz waves around 100 GHz are suitable for predicting the corrosion state of object 300, that is, for understanding the trend of terahertz intensity.

[0056] Here, we will examine the skin effect of the object 300 with reference to Figures 5 to 7. The skin effect can be interpreted as the phenomenon in which, as electromagnetic waves propagate through the object 300, the further away from the surface of the object 300 the electromagnetic waves become, as shown in Figure 5. The skin depth δ at which electromagnetic waves concentrate can be expressed by equation (1). δ=1 / √(πfμσ)=√(ρ / πfμ)···(1) f: frequency ρ: resistivity of the conductor σ: Conductivity of a conductor μ: Permeability of the conductor

[0057] As shown in Figures 6 and 7, it can be seen that the skin depth δ of object 300 decreases as the frequency of electromagnetic waves increases. In particular, in the frequency band above 100 GHz, the skin depth δ becomes very small, so it is thought that the skin effect alone cannot explain the changes in terahertz intensity mentioned above. Therefore, we will consider the waveguide effect.

[0058] Figure 8 shows the dielectric constant of the corrosive material 300a with respect to terahertz waves. As an example, Figure 8 shows five types of corrosive material 300a and their dielectric constants. For example, the dielectric constant of hemanetite (α-Fe2O3), called "red rust," is 3.8, and that of magnetite (Fe3O4), called "black rust," is 4.8. Such corrosive material 300a forms on the surface of the object 300 with a specific thickness. As the number of corrosion days increases, the amount of these corrosive material 300a formed on the surface of the object 300 increases, and the thickness of the corrosive material 300a increases. As mentioned above, the dielectric constant of hemanetite is low, around 3.8, so it is thought that as the thickness of the corrosive material 300a with a low dielectric constant increases, terahertz waves are more likely to guide near the corrosion layer. In other words, it is thought that the waveguide effect in the object 300 on which the corrosive material 300a is formed is dominant in the change in terahertz intensity. Figure 9 shows an example of an optical fiber that forms an optical waveguide with materials of different refractive indices.

[0059] (Detection intensity when the rotation angle of the plane of polarization is changed) Figures 10 and 11 show the detection intensity when the rotation angle of the polarization plane (polarization angle) is changed in the degradation diagnosis system 100 shown in Figure 1. Figure 10 shows the detection intensity when the polarization angle of a terahertz wave propagating to an object 300 on which no corrosive material 300a has formed on its surface is changed from 0° to 360°. Figure 11 shows the detection intensity when the polarization angle of a terahertz wave propagating to an object 300 on which corrosive material 300a has formed on its surface is changed from 0° to 360°. In each figure, the vertical axis represents the detection intensity, and the horizontal axis represents the polarization angle. Thick solid lines represent S polarization, and normal solid lines represent P polarization. Figures 10 and 11 show data when the polarization is rotated, for example, by a jig 205, in the degradation diagnosis system 100 configured as shown in Figure 1. The following samples are used as the object 300 for measuring these detection intensities. (Sample: Seven strands of 4mm diameter wire bundled together, resulting in a diameter of 11mm and a cross-sectional area of ​​90mm) 2 (A suspension wire with a total length of 300 mm)

[0060] When there is no corrosive material 300a (no rust), as shown in Figure 10, the maximum values ​​of both P-polarized and S-polarized light are shifted by, for example, -30° relative to 180°. The detection intensities of P-polarized and S-polarized light are similar in shape.

[0061] When corrosive material 300a is present (rusted), as shown in Figure 11, the intensity of P-polarized light is hardly detectable even when the polarization angle changes, while the intensity of S-polarized light changes when the polarization angle changes, and its maximum value is shifted by, for example, +30° relative to 180°. It can be inferred that the phase of this S-polarized light changes depending on the thickness of the corrosive layer. In other words, it is thought that when the thickness of corrosive material 300a changes, the phase of S-polarized light also changes accordingly.

[0062] Let's consider the reason why the detection intensity differs between P-polarized and S-polarized light. As shown in Figure 13, the phase of P-polarized light reverses just before it enters the metal surface and immediately after reflection from the metal surface, resulting in a stronger electric field at the metal surface. Therefore, when P-polarized light propagates through a metal surface, for example, through corrosion 300a formed on the surface of an object 300 with a total length of about 300 mm, it is easily absorbed by the corrosion 300a, and the intensity of the P-polarized light is hardly detectable.

[0063] In contrast, as shown in Figure 12, the electric field of S-polarized light cancels out immediately before it enters the metal surface and immediately after reflection from the metal surface. As a result, it is not absorbed by the corrosive material 300a formed on the surface of the object 300, but propagates through the corrosive material 300a formed on the surface of the object 300, and it is thought that the intensity of S-polarized light can be detected.

[0064] Thus, it is thought that the difference in how the electric field is formed on the metal surface causes the intensity of P-polarized light not to be detected, while the intensity of S-polarized light is detected.

[0065] (Phase shift) The phase shift δ that occurs when passing from the air layer through the corrosion layer with refractive index n can be expressed by equation (2). δ = 2Π / λ(ntdcosθt)···(2) λ: Wavelength d: Thickness of the corrosion layer

[0066] According to the principle of ellipsometry, the amplitude reflectance and phase change at a metal surface differ for P-polarized and S-polarized light, so reflected light is generally elliptically polarized. Due to the anisotropy in the in-plane and depth direction (out-of-plane) caused by the layered structure of the corrosive layer, as the thickness of the corrosive layer increases, the plane of polarization rotates according to the difference in dielectric constant.

[0067] Figure 14 illustrates the relationship between rust thickness, polarization plane rotation angle, and propagation intensity. Figure 14 shows the polarization plane rotation angle and propagation intensity for three types of suspension wires with different rust thicknesses, using a new, rust-free suspension wire as a reference. Specifically, with the polarization plane rotation angle of the rust-free suspension wire (A) set to 0°, the relative values ​​of the polarization plane rotation angle and propagation intensity for the three types of suspension wires (B) to (D) with different rust thicknesses are shown.

[0068] Four types of samples are used to evaluate the various thicknesses of rust formed on object 300. In the figure, A is a new suspension wire, i.e., object 300 in a rust-free state. In the figure, B, C, and D are suspension wires (A) with simulated rust added. In B, 0.05 mm thick polyimide tape is used as the simulated rust. In C, one sheet of 0.2 mm thick insulating tape is used as the simulated rust. C simulates rust that is thicker than the 0.05 mm thick polyimide tape. In D, instead of one sheet of insulating tape as in C, two sheets of 0.2 mm thick insulating tape are used as the simulated rust.

[0069] This data shows that as the rust thickens, the rotation angle of the polarization plane increases; in other words, as rust progresses, the rotation angle of the polarization plane increases. Therefore, for example, based on the rotation angle (polarization angle) of the S-polarized light mentioned above, it is possible to estimate whether or not rust has formed on the object 300, and also to estimate the thickness of the rust. For example, if the rotation angle of the polarization plane exceeds 30°, the deterioration diagnostic device 200 can determine that a corrosive layer that may affect quality has formed on the object 300.

[0070] For example, by applying the deterioration diagnosis method of this disclosure to a specific section of a newly installed overhead catenary wire on a railway line, the propagation intensity measured while changing the polarization angle can be recorded, and then, for example, several years or more than ten years after the initial measurement, similar measurements can be performed on the same section of deteriorated overhead catenary wire. By comparing the measurement results from when the wire was new with the latest measurement results, it is possible to estimate how much rust has progressed on the overhead catenary wire over the past ten years or so. Furthermore, based on this data, an appropriate replacement cycle for newly laid overhead catenary wires can be set. In addition, for example, if it can be confirmed that the rate of deterioration is progressing faster in a specific section of a railway line than in other sections, the overhead catenary wires in that section can be replaced preventively at regular intervals, while the overhead catenary wires in other sections are not replaced, thereby reducing installation costs, procurement costs, etc.

[0071] Figure 15 is a flowchart illustrating the operation of the degradation diagnostic device 200 of this disclosure. In step S1, the degradation diagnostic device 200 irradiates a terahertz wave, and in step S2, it may measure, for example, the intensity of the terahertz wave irradiated toward the object 300 and the intensity of the terahertz wave after it has propagated through the object 300. In step S3, the degradation diagnostic device 200 may change the polarization angle of the terahertz wave, that is, rotate the polarization of the terahertz wave, while measuring the intensity of the terahertz wave. At this time, the degradation diagnostic device 200 may record the intensity of the terahertz wave (propagation intensity, detection intensity) in association with the polarization angle of the terahertz wave.

[0072] In step S4, the deterioration diagnostic device 200 may, for example, measure the intensity of terahertz waves while rotating the polarization plane of the terahertz waves from 0° to 360°, and repeat the processes from step S2 onward until the measurement is complete. Once the measurement is complete, in step S5, the deterioration diagnostic device 200 may use the measured data to evaluate the rust occurrence status, i.e., the degree of deterioration, of the object 300.

[0073] Furthermore, the deterioration diagnostic device 200 of this disclosure is also applicable to cables covered with a sheathing material. Since cables covered with a sheathing material cannot be visually inspected from the outside without removing the sheathing material, the corrosion state of such cables can be estimated non-destructively by using the deterioration diagnostic device 200 of this disclosure.

[0074] Furthermore, the specific terahertz wave frequency used to evaluate and estimate the thickness of rust should preferably be a specific value (frequency) within the bandwidth of 10 GHz to 10 THz.

[0075] Furthermore, the deterioration diagnostic device 200 of this disclosure may change the value of a specific frequency depending on the type of rust. For example, the deterioration diagnostic device 200 may perform corrosion diagnosis by setting a first frequency (e.g., XGHz) within the band from 10GHz to 10THz as a specific frequency in the case of red rust, and setting a second frequency (e.g., YGHz) different from the first frequency as a specific frequency in the case of black rust.

[0076] Furthermore, the deterioration diagnostic device 200 may change its frequency according to the degree of rust. For example, for red rust of about 0.5 mm, the diagnosis may be performed at X GHz, and for red rust of about 1.5 mm, the diagnosis may be performed at a different frequency, Y GHz. Also, the deterioration diagnostic device 200 may change its frequency according to the material of the object 300. For example, for steel wire, the diagnosis may be performed at X GHz, and for copper wire, the diagnosis may be performed at a different frequency, Y GHz.

[0077] As described above, the deterioration diagnostic device 200 of the present disclosure is a deterioration diagnostic device 200 comprising at least one processor, the processor measuring the change in intensity of light of a specific frequency propagating through the object 300 while rotating the polarization of the light, and evaluating the thickness of the corrosion formed on the object 300 based on the measured rotation angle of the polarization of the light and the intensity of the light.

[0078] Conventional inspection methods have drawbacks in terms of time and labor costs. While methods that diagnose deterioration by measuring changes and attenuation of output are effective for detection because they easily provide quantitative changes, they are also highly susceptible to changes caused by reasons other than the deterioration of the target material. In particular, inspections that utilize changes in output are prone to changes due to the length of the object, the surrounding atmosphere, temperature, etc.

[0079] In contrast, the presence or absence of terahertz wave propagation due to changes in polarization is not affected by such attenuation, and is therefore considered to be a phenomenon that occurs solely depending on the deterioration of the object 300. For this reason, the deterioration diagnostic device 200 of this disclosure, which utilizes this method, can be used to obtain high reliability in diagnosing deterioration. Furthermore, it becomes possible to perform on-site inspections without removing the cable object 300 from the infrastructure and bringing it to an experimental facility, thus saving the trouble of disposal and replacement, and reducing waste.

[0080] The control unit and method described herein may be implemented by a dedicated computer comprising a processor programmed to perform one or more functions embodied by a computer program. Alternatively, the apparatus and method described herein may be implemented by a dedicated computer comprising a processor composed of dedicated hardware logic circuits. Alternatively, the apparatus and method described herein may be implemented by one or more dedicated computers comprising a combination of a processor that executes a computer program and one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0081] The above process can also be implemented using dedicated hardware circuits. In this case, it may be executed on a single piece of hardware or on multiple pieces of hardware.

[0082] In each of the above embodiments, the term "processor" refers to a processor in a broad sense, and includes general-purpose processors (e.g., CPU: Central Processing Unit, etc.) and dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0083] Furthermore, the processor operations in each of the above embodiments may not be performed by a single processor, but may also be performed by multiple processors located in physically separate locations working together. Also, the order of the processor operations is not limited to the order described in each of the above embodiments, and may be changed as appropriate.

[0084] Furthermore, the above program may be provided on a computer-readable non-temporary recording medium such as a USB (Universal Serial Bus) memory, flexible disk, or CD-ROM (Compact Disc Read Only Memory), or it may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable non-temporary recording medium is usually transferred to and stored in memory or storage. This program may also be provided, for example, as a standalone application software, or it may be incorporated into the software of each device as a function of that device.

[0085] The program of this application can be provided as a program product. A program product includes any form of product for providing a program. For example, a program product includes a program provided via a network such as the Internet, and non-temporary computer-readable recording media such as CD-ROMs and DVDs on which the program is stored.

[0086] The following additional information is disclosed regarding the above embodiments. (Note 1) A degradation diagnostic device comprising at least one processor, The aforementioned processor, The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. A deterioration diagnostic device that evaluates the thickness of corrosive material formed on an object based on the rotation angle of the measured polarization of the light and the intensity of the light. (Note 2) The processor is a degradation diagnostic device as described in Appendix 1, which measures the change in intensity when a specific device automatically rotates the polarization of the light. (Note 3) The deterioration diagnostic device described in Appendix 2, wherein the processor measures the change in intensity when the specific device rotates the polarization of the light incident on the object. (Note 4) The deterioration diagnostic device described in Appendix 2, wherein the processor measures the change in intensity when the specific device rotates the polarization of the light emitted from the object. (Note 5) The degradation diagnostic device described in Appendix 1, wherein the polarization of the light is S-polarization. (Note 6) The aforementioned specific frequency is a specific frequency between 10 GHz and 200 GHz, as described in Appendix 5 of the degradation diagnostic device. (Note 7) The aforementioned specific frequency is a frequency between 40 GHz and 140 GHz, as described in Appendix 6 of the degradation diagnostic device. (Note 8) The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A computer-based method for diagnosing deterioration. (Note 9) The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A program that causes a computer to perform a task. (Note 10) The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A computer program product that includes a program that causes a computer to perform a task. (Note 11) The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A computer-readable recording medium on which a program that causes a computer to perform a certain action is recorded. [Explanation of Symbols]

[0087] 1 Input / Output Interface 2 memory 2a Degradation Diagnosis Program 3 processors 4 buses 31 Measurement Unit 32 Evaluation Department 33 Control Unit 100 Deterioration Diagnosis System 200 Deterioration Diagnosis Device 201 Irradiator 202 Jig 203 Reflector 204 Reflector 205 Jig 206 detectors 300 objects 300a Corrosive material 301 First end 302 Second end

Claims

1. A degradation diagnostic device comprising at least one processor, The aforementioned processor, The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. A deterioration diagnostic device that evaluates the thickness of corrosive material formed on an object based on the rotation angle of the measured polarization of the light and the intensity of the light.

2. The degradation diagnostic device according to claim 1, wherein the processor measures the change in intensity when a specific device automatically rotates the polarization of the light.

3. The deterioration diagnostic device according to claim 2, wherein the processor measures the change in intensity when the specific device rotates the polarization of the light incident on the object.

4. The deterioration diagnostic device according to claim 2, wherein the processor measures the change in intensity when the specific device rotates the polarization of the light emitted from the object.

5. The degradation diagnostic device according to claim 1, wherein the polarization of the light is S-polarization.

6. The deterioration diagnostic device according to claim 5, wherein the specified frequency is a specific frequency between 10 GHz and 200 GHz.

7. The deterioration diagnostic device according to claim 6, wherein the specified frequency is a frequency between 40 GHz and 140 GHz.

8. The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A computer-based method for diagnosing deterioration.

9. The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A program that causes a computer to perform a task.

10. The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A computer program product that includes a program that causes a computer to perform a task.

11. The change in intensity of light of a specific frequency propagating through the object is measured while rotating the polarization of the light. Based on the rotation angle of the measured polarization of the light and the intensity of the light, the thickness of the corrosion formed on the object is evaluated. A computer-readable recording medium on which a program that causes a computer to perform a certain action is recorded.

Images