Method for detecting fatigue damage and system for detecting fatigue damage

Abstract

To easily grasp the degree of a fatigue damage of a tower-like structure.SOLUTION: The method for detecting a fatigue damage includes: grasping the relation of stress in a stress focus part as a part of a tower-like structure where stress is focused and a top displacement; measuring the top displacement on the basis of information from an acceleration sensor set in the tower-like structure; and outputting information on the fatigue damage degree for each direction around the tower-like structure on the basis of the grasped relation between the stress and the top displacement and the measured top displacement.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fatigue damage detection method and a fatigue damage detection system.

Background Art

[0002] Patent Document 1 describes a support damage detection system including: an acquisition means for acquiring vibration information caused by the support itself shaking due to natural wind hitting the support; a storage means for storing the vibration information or conversion information of the vibration information; a grasping means for grasping the historical change of the natural frequency from the vibration information or the conversion information; and an output means for outputting information regarding the abnormality of the support from the grasped historical change.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Tower-shaped structures such as wind power generation devices and chimneys may suffer fatigue damage due to stress applied by vibration or the like. For example, when wind continues to blow on a tower-shaped structure, Karman vortices are generated on the downstream side of the tower-shaped structure. For example, when the generation cycle of the Karman vortices matches the natural period of the tower-shaped structure, resonance occurs for some reason, and fluctuating stress is applied to the tower-shaped structure by the vibration. Due to this, it is assumed that fatigue damage occurs in the tower-shaped structure. An object of the present invention is to make it easier to grasp the degree of fatigue damage of a tower-shaped structure.

Means for Solving the Problems

[0005] The invention according to claim 1 is a fatigue damage detection method that grasps the relationship between the stress and the top displacement at the stress concentration location where stress concentrates in the tower-like structure, measures the top displacement based on the information from the acceleration sensor installed in the tower-like structure, and outputs information regarding the fatigue damage degree for each circumferential direction of the tower-like structure based on the grasped relationship between the stress and the top displacement and the measured top displacement. The invention according to claim 2 is the fatigue damage detection method according to claim 1, wherein the relationship between the stress and the top displacement is grasped by finite element analysis. The invention according to claim 3 is the fatigue damage detection method according to claim 2, wherein the relationship between the stress and the top displacement is grasped at a circumferential direction angle of a predetermined resolution. The invention according to claim 6 is the fatigue damage detection method according to claim 1, wherein the information from the acceleration sensor is measured on two axes that are orthogonal to each other in the horizontal direction orthogonal to the axial direction of the tower-like structure. The invention according to claim 8 is the fatigue damage detection method according to claim 1, wherein the information regarding the fatigue damage degree for each circumferential direction of the tower-like structure at the stress concentration location is displayed in a circular shape. The invention according to claim 10 is the fatigue damage detection method according to claim 1, which outputs the stress waveform at the stress concentration location based on the grasped relationship between the stress and the top displacement and the measured top displacement, and outputs the information regarding the fatigue damage degree based on the output stress waveform. The invention according to claim 12 is the fatigue damage detection method according to claim 1, wherein the fatigue damage degree is calculated based on a fatigue design curve. The invention according to claim 14 is the fatigue damage detection method according to claim 1, wherein the remaining life is calculated from the maximum value of the fatigue damage degree for each circumferential direction of the tower. The invention according to claim 9 includes one or more processors. The one or more processors obtain the relationship between the stress and the top displacement at the stress concentration location where stress concentrates in the tower structure, and information regarding the acceleration measured by the acceleration sensor installed in the tower structure. Based on the obtained relationship between the stress and the top displacement and the information regarding the acceleration, the fatigue damage detection system outputs information regarding the fatigue damage degree for each circumferential direction of the tower structure. The invention according to claim 10 is the fatigue damage detection system according to claim 9, wherein the one or more processors obtain the information regarding the acceleration within a predetermined period and output the information regarding the fatigue damage degree for each circumferential direction of the tower structure within the predetermined period.

Effects of the Invention

[0006] According to the inventions of claims 1 and 9, it is possible to more easily grasp the fatigue damage degree of the tower structure. According to the invention of claim 2, it is possible to more specifically grasp the relationship between the stress and the top displacement. According to the invention of claim 3, it is possible to calculate the fatigue damage degree at an arbitrary circumferential direction angle. According to the invention of claim 4, it is possible to obtain the acceleration at an arbitrary circumferential direction angle. According to the invention of claim 5, it is possible to easily grasp the fatigue damage degree at each circumferential direction angle. According to the invention of claim 6, it is possible to grasp the fatigue damage degree by using the stress waveform at the stress concentration location. According to the invention of claim 7, it is possible to calculate the fatigue damage degree based on the allowable number of repetitions for each stress range. According to the invention of claim 8, it is possible to calculate the remaining life of the tower structure to better conform to the actual situation. According to the invention of claim 10, it is possible to grasp the fatigue damage degree of the tower structure within a predetermined period.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. <Configuration of Fatigue Damage Detection System> FIG. 1 is a diagram showing a configuration example of a fatigue damage detection system 1 according to the present embodiment. The fatigue damage detection system 1 includes a center device 10 that functions as a server, a tower-like structure 40, a detection device 50 that is attached to the tower-like structure 40 and acquires information related to acceleration as vibration information generated in the tower-like structure 40, a communication device 60 that is connected to the detection device 50 via a wired or wireless network and acquires information related to acceleration from the detection device 50, and a terminal device 70 that manages the tower-like structure 40. The center device 10, the communication device 60, and the terminal device 70 are connected via a wired or wireless network 90.

[0009] The center device 10 acquires information related to the relationship between the stress applied to a stress concentration point, which is a site where stress is concentrated in the tower-like structure 40, and the top displacement. Further, the center device 10 acquires information related to the acceleration measured by the detection device 50 installed in the tower-like structure 40. Then, based on the acquired information, the center device 10 outputs information related to the fatigue damage degree for each circumferential direction of the tower-like structure 40. The center device 10 is realized, for example, by a computer. Each function executed by the center device 10 may be realized by a single computer or by distributed processing by a plurality of computers.

[0010] The tower-like structure 40 is, for example, a structure that extends long in the vertical axial direction and includes functional structures, for example, at the top or in the middle of the axial direction. Examples of the tower-like structure 40 include a chimney and a wind power generation device. Further, as shown in FIG. 1, the detection device 50 is installed, for example, at the top of the tower-like structure 40. The detection device 50 includes an acceleration sensor 51 (see FIG. 3) and measures the acceleration at the installed portion of the tower-like structure 40. The detection device 50 transmits information related to the measured acceleration to the communication device 60, and the communication device 60 transmits the acquired information related to the acceleration to the center device 10. The detection device 50 and the communication device 60 are communicably connected via a wired or wireless network.

[0011] The communication device 60 may be installed, for example, at the base of the tower-like structure 40, or may be installed in another building near the tower-like structure 40. The detection device 50 and the communication device 60 may each be provided with means for storing information regarding acceleration, or either one of them may be provided with the storage means. The detection device 50 and the communication device 60 may have a relationship of a slave device and a master device. As the tower-like structure 40 to be detected by the fatigue damage detection system 1 according to the present embodiment, various other tower-like structures can be included.

[0012] The terminal device 70 is, for example, a personal computer (PC) of an organization that manages the tower-like structure 40, a PC managed by a wind power generation company, or the like. Each company, organization, etc. grasps and manages the state of the tower-like structure 40 owned by itself based on the information obtained from the center device 10. The terminal device 70 is realized, for example, by a computer, a tablet-type information terminal, or other information processing devices.

[0013] The network 90 is an information communication network that undertakes communication between each system and device. The type of the network 90 is not particularly limited as long as data can be transmitted and received, and it may be, for example, the Internet, a LAN (Local Area Network), a WAN (Wide Area Network), or the like. The communication line used for data communication may be wired, wireless, or a combination of these. Also, a configuration in which each device is connected via a plurality of networks or communication lines may be adopted.

[0014] FIG. 2 is a diagram showing an example of the hardware configuration of the center device 10 according to the present embodiment. The terminal device 70 also has a similar configuration. The center device 10 is composed of a computer device 20 such as a desktop PC or a notebook PC, and a database (DB) 30 in which various acquired information is stored. The computer device 20 of the center device 10 includes a control unit 21 which is a CPU (Central Processing Unit) that controls the entire device, a memory 22 such as a RAM (Random Access Memory) used as a work area during calculations, and a storage unit 23 which is a storage device such as an HDD (Hard Disk Drive) or a semiconductor memory used for storing programs and various setting data. It also has a communication unit 24 that transmits and receives data via a network 90. Furthermore, it has an operation unit 25 such as a keyboard, a pointing device, and a touch panel that receives input operations from the user, a display unit 26 composed of a liquid crystal display that displays images, text information, etc. to the user, and a display control unit 27 that controls the display unit 26. Note that each hardware does not necessarily have a single housing. Also, there is a mode in which a database (DB) 30 is integrally provided in the computer device 20. The database (DB) 30 may also be connected to the computer device 20 via the network 90.

[0015] <Functional configurations of the detection device 50 and the communication device 60> FIG. 3 is a diagram showing a functional configuration example of the detection device 50 and the communication device 60 according to the present embodiment. The detection device 50 has an acceleration sensor 51 capable of detecting acceleration in multiple axial directions. This acceleration sensor 51 is a sensor capable of measuring two axes, an x-axis and a y-axis, which are orthogonal to each other, in the horizontal direction orthogonal to the axial direction of the tower-like structure 40, for example. In the present embodiment, the acceleration sensor 51 is installed at the top of the tower-like structure 40 to measure the acceleration at the top of the tower-like structure 40 obtained by wind vibration. Note that the position where the acceleration sensor 51 is installed is not limited to the top of the tower. As long as it can measure two axes, an x-axis and a y-axis, which are orthogonal to each other, in the horizontal direction orthogonal to the axial direction of the tower-like structure 40, it may be installed at other positions of the tower-like structure 40.

[0016] Further, the detection device 50 includes an acceleration information storage unit 52 that stores information regarding the detected acceleration, and an acceleration information output unit 53 that outputs information regarding the acceleration to the communication unit 54. The detection device 50 also includes a communication unit 54 that communicates with the communication device 60 and transmits information regarding the acceleration, and a power supply unit 55 that incorporates a battery and supplies power to the detection device 50. As the power supply unit 55, for example, a built-in battery such as a lithium-ion battery or a solar cell can be used.

[0017] The communication device 60 includes a communication unit 61 that transmits and receives data to and from the center device 10 and the detection device 50. The communication unit 61 receives information regarding the acceleration from the detection device 50 and transmits the information regarding the acceleration to the center device 10. The communication device 60 also includes an acceleration information storage unit 62 that stores the information regarding the acceleration acquired from the detection device 50, and an acceleration information output unit 63 that outputs the information regarding the acceleration to the communication unit 61. Note that the functions of the detection device 50 and the communication device 60 may be realized by a single device, or the detection device 50 may be configured to communicate directly with the center device 10.

[0018] <Functional Configuration of Center Device 10> FIG. 4 is a diagram showing a functional configuration example of the center device 10 according to the present embodiment. Each function is realized through the execution of a computer program by the computer device 20. The center device 10 includes an acceleration information acquisition unit 11 that acquires information regarding the acceleration from the communication device 60 via the communication unit 24, and an acceleration information conversion unit 12 that converts the acquired information regarding the acceleration into a displacement waveform and outputs it. The acceleration information acquisition unit 11 acquires, for example, an acceleration waveform as information regarding the acceleration. The acceleration information conversion unit 12 converts the acquired acceleration waveform into spectrum information by performing a Fourier transform on the acceleration waveform. Then, after performing filtering, double integration is performed, and an inverse Fourier transform is performed to convert the acceleration waveform into a displacement waveform. Note that the information regarding acceleration is vibration information acquired by various sensors. Although acceleration is the main aspect, other relevant aspects include various characteristics related to vibration such as velocity, position displacement, and strain time history waveforms, as well as numerical values of these characteristics. Also, the format of the information is not particularly limited.

[0019] Further, the center device 10 includes a finite element analysis unit 13 that performs finite element analysis using a three-dimensional model of the tower-like structure 40, and a stress-displacement correlation information acquisition unit 14 that acquires correlation information indicating the relationship between the stress and the top displacement at the stress concentration location of the tower-like structure 40 from the analysis results. Finite element analysis is a simulation method that divides an object into a finite number of elements, performs analysis for each element, and derives the final solution by summarizing them. The finite element analysis unit 13 inputs the amount of displacement applied to the top portion of the three-dimensional model and estimates the stress applied to the stress concentration location according to the input displacement amount. The finite element analysis is performed at a circumferential angle of the tower with a predetermined resolution, and the relationship between the stress applied to the stress concentration location of the tower-like structure 40 and the top displacement is grasped for each circumferential angle of the tower. The stress-displacement correlation information acquisition unit 14 acquires the relationship between the stress applied to the stress concentration location of the tower-like structure 40 and the top displacement from the results of the finite element analysis. Note that finite element analysis is an example of a simulation method and is not limited thereto. It may also be configured to obtain the relationship between stress and displacement by other simulation methods. Also, in the present embodiment, since the detection device 50 is installed at the top of the tower-like structure 40 as shown in FIG. 1, the finite element analysis unit 13 inputs the amount of displacement applied to the top portion of the three-dimensional model. The position at which the displacement amount is input to the three-dimensional model is changed according to the position at which the detection device 50 is installed on the tower-like structure 40.

[0020] Further, the center device 10 has a displacement waveform conversion unit 15 that converts the displacement waveform output by the acceleration information conversion unit 12 into a stress waveform and outputs it based on the acquired correlation information. The displacement waveform conversion unit 15 converts the displacement waveform output by the acceleration information conversion unit 12 into stress time history data by matching it with the correlation information indicating the relationship between the stress and the displacement acquired by the stress-displacement correlation information acquisition unit 14.

[0021] Further, the center device 10 includes a fatigue design curve acquisition unit 16 that acquires a fatigue design curve for the tower-like structure 40 via the communication unit 24, and a fatigue design curve storage unit 17 that stores the acquired fatigue design curve. The fatigue design curve is a curve created based on an experiment in which a fatigue load is applied to the target structure, and indicates the allowable number of repetitions until the structure undergoes fatigue failure when vibrations within a certain stress range are repeatedly applied to the target structure. Fatigue failure is a phenomenon in which cracks, fractures, etc. occur in a stress load state below the tensile strength when a constant stress is applied over a long period of time.

[0022] Further, the center device 10 includes a fatigue damage degree calculation unit 18 that calculates the fatigue damage degree based on the stress waveform output by the displacement waveform conversion unit 15 and the fatigue design curve stored in the fatigue design curve storage unit 17. The fatigue damage degree calculation unit 18 counts the number of cycles for each stress range from the stress waveform over a predetermined entire observation period, and calculates the fatigue damage degree based on the fatigue design curve. Further, the center device 10 includes an output unit 19 that outputs information regarding the fatigue damage degree calculated by the fatigue damage degree calculation unit 18 to the communication unit 24. The information regarding the fatigue damage degree is transmitted to the terminal device 70 via the communication unit 24 and is displayed on the display unit 74 (see FIG. 5) of the terminal device 70.

[0023] <Functional Configuration of Terminal Device 70> FIG. 5 is a diagram showing a functional configuration example of the terminal device 70 according to the present embodiment. The terminal device 70 includes a communication unit 71 that communicates with an external device and transmits and receives data, and a fatigue damage degree acquisition unit 72 that acquires information regarding the fatigue damage degree from the center device 10 via the communication unit 71. Further, the terminal device 70 includes an output unit 73 that outputs information regarding the fatigue damage degree acquired by the fatigue damage degree acquisition unit 72 to the display unit 74, and a display unit 74 that displays the output information.

[0024] Next, the fatigue damage detection process of the tower-shaped structure 40, which is executed by the fatigue damage detection system 1 according to the present embodiment, will be described.

[0025] <Processing in the detection device 50 and the communication device 60> FIG. 6 is a flowchart showing the flow of processing performed by the detection device 50 and the communication device 60. In FIG. 6, first, the acceleration sensor 51 of the detection device 50 measures the acceleration of the tower-shaped structure 40 (step S101). In the present embodiment, the acceleration sensor 51 is installed at the top of the tower-shaped structure 40. With this acceleration sensor 51, the acceleration at the top of the tower can be measured in the two x-axis and y-axis directions, each orthogonal to the axial direction of the tower-shaped structure 40 and orthogonal to each other, which are horizontal directions. The acceleration sensor 51 measures the acceleration at a predetermined resolution in the circumferential direction of the tower at a predetermined circumferential angle.

[0026] Next, the acceleration information storage unit 52 stores information regarding the measured acceleration (step S102). Here, in the acceleration information storage unit 52, as information regarding the acceleration, for example, an acceleration waveform that is time history data of the acceleration is stored. Next, the acceleration information output unit 53 outputs information regarding the acceleration to the communication device 60 via the communication unit 54 (step S103). The acceleration information output unit 53 outputs information regarding the acceleration measured in a predetermined period to the communication device 60.

[0027] Next, the communication unit 61 of the communication device 60 acquires information regarding the acceleration (step S104). The communication unit 61 acquires the time history data of the acceleration measured in a predetermined period, which is stored in the acceleration information storage unit 52 of the detection device 50. Next, the acceleration information storage unit 62 stores the acquired information regarding the acceleration (step S105). In the acceleration information storage unit 62, as information regarding the acceleration, for example, an acceleration waveform that is time history data of the acceleration is stored. Next, the acceleration information output unit 63 outputs information regarding acceleration to the center device 10 via the communication unit 61 (step S106). The acceleration information output unit 63 outputs information regarding the acceleration measured during a predetermined period to the center device 10. The predetermined period is determined in consideration of, for example, the change in wind conditions for each season, and is, for example, one year. The predetermined period may be set longer than one year or shorter.

[0028] The acceleration information output unit 63 may output information regarding acceleration to the center device 10 periodically, or may be configured to output in response to an instruction from the center device 10 or the terminal device 70. Further, the information regarding acceleration may be stored in a portable memory device, and the information may be acquired by the center device 10 via the memory device.

[0029] <Processing in the center device 10> FIG. 7 is a flowchart showing the flow of processing performed by the center device 10. In FIG. 7, first, the acceleration information acquisition unit 11 of the center device 10 acquires information regarding acceleration from the communication device 60 via the communication unit 24 (step S201). The acceleration information acquisition unit 11 acquires an acceleration waveform, which is time history data of the acceleration measured during a predetermined period and stored in the acceleration information storage unit 62 of the communication device 60.

[0030] Next, the acceleration information conversion unit 12 converts the acquired acceleration waveform into a displacement waveform and outputs it (step S202). In the conversion, first, the acceleration information conversion unit 12 converts the acceleration waveform into spectrum information by performing Fourier transform. Next, filtering is performed on the spectrum information to remove noise components excluding high-frequency and low-frequency components. Thereafter, double integration is performed, and an inverse Fourier transform is performed to obtain a displacement waveform.

[0031] FIG. 8 is a diagram showing an example of the processing result performed by the acceleration information conversion unit 12. FIG. 8(a) is an example of the acceleration waveform before conversion, where the horizontal axis is time (sec) and the vertical axis is acceleration (mm / S2 ) is shown. FIG. 8(b) shows an example of a displacement waveform converted from an acceleration waveform by Fourier transform, double integration, and inverse Fourier transform. The horizontal axis represents time (sec), and the vertical axis represents displacement (mm).

[0032] In the present embodiment, the acceleration waveform is converted into a displacement waveform by the acceleration information conversion unit 12 of the center device 10, but it is not limited to this. For example, the detection device 50 or the communication device 60 may have a function of converting information related to acceleration into information related to a displacement waveform. In this case, information related to the displacement waveform converted by the detection device 50 or the communication device 60 is output to the center device 10 and used for the fatigue damage degree calculation process in the center device 10.

[0033] Next, the finite element analysis unit 13 performs finite element analysis using a three-dimensional model of the tower-like structure 40 (step S203). The finite element analysis unit 13 inputs the amount of displacement applied to the top portion of the three-dimensional model and estimates the stress applied to the stress concentration location according to the input amount of displacement. The finite element analysis is performed at a circumferential angle of the tower with a predetermined resolution, and the relationship between the stress applied to the stress concentration location of the tower-like structure 40 and the top displacement is grasped for each circumferential angle of the tower. The three-dimensional model may be generated, for example, based on information regarding the shape of the tower-like structure 40, or may be generated based on three-dimensional image data of the tower-like structure 40.

[0034] FIG. 9 is a diagram showing an example of a three-dimensional model 41 of the tower-like structure 40 used for finite element analysis. The three-dimensional model 41 is a model for estimating the stress applied to the stress concentration location 43 when a displacement U is applied to the top portion 42, and outputs the relationship between the top displacement applied to the top portion 42 and the stress applied to the stress concentration location 43. The stress concentration location is a part where stress is concentrated, and a part where the shape changes such as a notch or a step corresponds to it. When there are a plurality of stress concentration locations 43, the stress is estimated for each of them. In addition, in cases where the stress concentration point 43 cannot be estimated from the shape, etc., it may be configured to identify the stress concentration point 43 by analysis. In this case, when a displacement U is applied to the top of the tower 42, the stress applied to each part of the three-dimensional model 41 can be estimated, and the stress concentration point 43 can be identified.

[0035] The finite element analysis unit 13 inputs the amount of displacement to be applied to the top of the tower 42. The finite element analysis unit 13 applies displacements to the top of the tower 42 so as to gradually increase at the circumferential angles of the tower with a predetermined resolution. The predetermined resolution is an angle equal to or greater than a certain resolution required for calculating the fatigue life for each circumferential direction of the tower structure 40. For example, displacements are applied every 2 degrees. The fatigue life of the tower structure 40 is calculated based on the maximum value among the fatigue damage degrees calculated for each circumferential direction of the tower. Therefore, the higher the resolution is set, the more accurately the fatigue life of the tower structure 40 can be calculated. Then, the finite element analysis unit 13 estimates the stress applied to the stress concentration point 43 according to the input displacement amount.

[0036] Returning to FIG. 7, next, the stress-displacement correlation information acquisition unit 14 acquires correlation information indicating the relationship between the stress and the top displacement at the stress concentration point of the tower structure 40 based on the result of the finite element analysis (step S204). The stress-displacement correlation information acquisition unit 14 acquires correlation information indicating the relationship between the stress and the top displacement at the stress concentration point of the tower structure 40 from the terminal device 70. FIG. 10 is a diagram showing an example of the relationship between the top displacement applied to the top of the tower 42 and the stress applied to the stress concentration point 43. The horizontal axis represents the top displacement (mm), and the vertical axis represents the stress range (MPa). In the example shown in FIG. 10, it can be understood that there is a linear correlation between the top displacement (mm) and the stress range (MPa).

[0037] Next, the displacement waveform conversion unit 15 converts the displacement waveform output by the acceleration information conversion unit 12 into a stress waveform and outputs it (step S205). FIG. 11 is a diagram showing an example of the processing result performed by the displacement waveform conversion unit 15. FIG. 11(a) is an example of the displacement waveform before conversion, where the horizontal axis represents time (sec) and the vertical axis represents displacement (mm). FIG. 11(b) shows an example of the stress waveform converted from the displacement waveform, where the horizontal axis represents time (sec) and the vertical axis represents stress (MPa). The displacement waveform conversion unit 15 converts the displacement waveform into a stress waveform based on the correlation information indicating the relationship between the stress at the stress concentration location and the apex displacement. The displacement waveform conversion unit 15 can, for example, convert the displacement into the corresponding stress by fitting the displacement waveform to the graph shown in FIG. 10, and obtain the stress waveform at the stress concentration location.

[0038] Next, the fatigue design curve acquisition unit 16 acquires a fatigue design curve for the tower-shaped structure 40 (step S206). The fatigue design curve is a curve showing the allowable number of repetitions until the structure undergoes fatigue failure when vibrations in each stress range are repeatedly applied to the target structure. For example, in this embodiment, the fatigue design curve acquisition unit 16 acquires a curve created based on an experiment in which a fatigue load is applied to the tower-shaped structure 40 to be measured. FIG. 12 is a diagram showing the fatigue design curve for the tower-shaped structure 40. The horizontal axis represents the allowable number of repetitions (Cycle), and the vertical axis represents the stress range (MPa). In the example shown in FIG. 12, the tower-shaped structure 40 undergoes fatigue failure when vibrations with a stress range of 350 MPa are applied 12,800 Cycles. Also, the tower-shaped structure 40 undergoes fatigue failure when vibrations with a stress range of 21 MPa are applied 10,000,000 Cycles. The acquired fatigue design curve is stored in the fatigue design curve storage unit 17 (step S207).

[0039] Next, the fatigue damage degree calculation unit 18 calculates the fatigue damage degree based on the stress waveform and the fatigue design curve (step S208). The fatigue damage degree calculation unit 18 counts the number of cycles for each stress range from the stress waveform over a predetermined observation period. The counting of the number of cycles is performed, for example, by applying a cycle counting method typified by the rainflow method. After counting the number of cycles for each stress range, the fatigue damage degree calculation unit 18 calculates the fatigue damage degree for each stress range based on the fatigue design curve. Then, by adding them together, the fatigue damage degree at the stress concentration location of the tower-like structure 40 is calculated. The fatigue damage degree is calculated by multiplying the number of occurrences of vibration by the reciprocal of the allowable number of repetitions for each stress range.

[0040] For example, consider the case where the number of cycles for each stress range in the entire observation period of the stress waveform output by the displacement waveform conversion unit 15 in step S205 is 1 cycle of vibration with a stress range of 350 MPa and 2 cycles of vibration with a stress range of 21 MPa. From the fatigue design curve shown in FIG. 12, the allowable number of repetitions of vibration with a stress range of 350 MPa is 12,800 cycles, and the fatigue damage degree due to vibration with a stress range of 350 MPa is calculated as 1 / 12,800. Also, the allowable number of repetitions of vibration with a stress range of 21 MPa is 10,000,000 cycles, and the fatigue damage degree due to vibration with a stress range of 21 MPa is calculated as 2 / 10,000,000. Then, by adding these fatigue damage degrees for each stress range, the fatigue damage degree at the stress concentration location of the tower-like structure 40 is calculated as 3133 / 40,000,000.

[0041] Note that the above fatigue damage degree calculation process is repeated at the circumferential direction angle of the tower with a predetermined resolution. The predetermined resolution is an angle equal to or greater than a certain resolution required for calculating the fatigue life of the tower-like structure 40. Also, the fatigue damage degree calculation unit 18 calculates the life until the tower-like structure 40 causes fatigue failure based on the fatigue damage degree. The life until fatigue failure is calculated based on the maximum value among the fatigue damage degrees at the stress concentration locations of the tower-like structure 40 calculated at the circumferential direction angle of the tower with a predetermined resolution. The life until fatigue failure is calculated based on the observation period and the calculated fatigue damage degree.

[0042] For example, consider the case where the fatigue damage degree at the stress concentration point of the tower structure 40 is 1 / 100 during an observation period of one year. The fatigue damage degree calculated based on the fatigue design curve shown in Fig. 12 is an index indicating that fatigue failure occurs when its cumulative value reaches 1. Therefore, when the fatigue damage degree during the one-year observation period is 1 / 100, the life of the tower structure 40 until fatigue failure occurs is calculated to be 100 years by taking the reciprocal of the fatigue damage degree. When 10 years have passed since the tower structure 40 was installed, the remaining life of the tower structure 40 is calculated to be 90 years.

[0043] Next, the output unit 19 outputs information regarding the fatigue damage degree calculated by the fatigue damage degree calculation unit 18 to the communication unit 24 (step S209). Examples of the information regarding the fatigue damage degree include, for example, the fatigue damage degree at the stress concentration point of the tower structure 40, the remaining life of the tower structure 40, and the like. The information regarding the fatigue damage degree is transmitted to the terminal device 70 via the communication unit 24, and the processing in the center device 10 is completed.

[0044] The processing shown in Fig. 7 according to the present embodiment is implemented by a program executed by the center device 10. However, the embodiment is not limited to that mode, and may be implemented in a form in which it is distributed and executed by a plurality of devices, or in a form in which a program is installed and executed in the terminal device 70.

[0045] <Processing in the terminal device 70> Fig. 13 is a flowchart showing the flow of processing performed in the terminal device 70. In Fig. 13, first, the fatigue damage degree acquisition unit 72 of the terminal device 70 acquires information regarding the fatigue damage degree calculated by the fatigue damage degree calculation unit 18 of the center device 10 via the communication unit 71 (step S301). Next, the output unit 73 outputs the acquired information regarding the fatigue damage degree to the display unit 74 (step S302). The display unit 74 displays the information regarding the fatigue damage degree (step S303).

[0046] FIG. 14 is a diagram showing an example of display of information regarding the fatigue damage degree on the display unit 74 of the terminal device 70. FIG. 14 shows the fatigue damage degree for each circumferential direction of the tower-shaped structure 40 at the stress concentration location in a circular shape. By showing the fatigue damage degree in a circular shape in this way, the fatigue damage degree at each circumferential direction angle of the tower-shaped structure 40 can be visually grasped. Also, it is possible to easily grasp which circumferential direction angle has a large fatigue damage degree, and based on the fatigue damage degree at that angle, the fatigue life can be grasped. The example shown in FIG. 14 shows the fatigue damage degree in a circular shape for 360 degrees counterclockwise with an arbitrary point on the outer periphery as 0 degrees for the cross-section at the stress concentration location of the tower-shaped structure 40, but it is not limited to this. For example, in accordance with the cross-sectional shape at the stress concentration location of the tower-shaped structure 40, the fatigue damage degree may be shown along the outer periphery. Also, it may be configured to display the remaining life, or it may be configured to be able to switch between the display showing the fatigue damage degree in a circular shape as shown in FIG. 14 and the display showing the remaining life. Further, the terminal device 70 may be configured to display on the display unit 74 the relationship between the tower top displacement applied to the tower top 42 shown in FIG. 10 and the stress applied to the stress concentration location 43.

Explanation of Signs

[0047] 1... Fatigue damage detection system, 10... Center device, 11... Acceleration information acquisition unit, 12... Acceleration information conversion unit, 13... Finite element analysis unit, 14... Stress-displacement correlation information acquisition unit, 15... Displacement waveform conversion unit, 16... Fatigue design curve acquisition unit, 17... Fatigue design curve storage unit, 18... Fatigue damage degree calculation unit, 19... Output unit, 20... Computer device, 40... Tower-shaped structure, 41... Three-dimensional model, 50... Detection device, 51... Acceleration sensor, 52... Acceleration information storage unit, 53... Acceleration information output unit, 54... Communication unit, 55... Power supply unit, 60... Communication device, 61... Communication unit, 62... Acceleration information storage unit, 63... Acceleration information output unit, 70... Terminal device, 71... Communication unit, 72... Fatigue damage degree acquisition unit, 73... Output unit, 74... Display unit, 90... Network

Claims

1. Grasp the relationship between the stress at the stress concentration point where stress concentrates in the tower-like structure and the top displacement, Measure the top displacement based on the information from the acceleration sensors installed on the tower-like structure, A fatigue damage detection method that outputs information on the fatigue damage degree for each circumferential direction of the tower-like structure based on the grasped relationship between the stress and the top displacement and the measured top displacement.

2. The fatigue damage detection method according to Claim 1, wherein the relationship between the stress and the top displacement is grasped by finite element analysis.

3. The fatigue damage detection method according to Claim 2, wherein the relationship between the stress and the top displacement is grasped at the circumferential direction angle of a predetermined resolution.

4. The fatigue damage detection method according to Claim 1, wherein the information from the acceleration sensors is measured on two axes perpendicular to each other in the horizontal direction perpendicular to the axial direction of the tower-like structure.

5. The fatigue damage detection method according to Claim 1, wherein the information on the fatigue damage degree for each circumferential direction of the tower-like structure at the stress concentration point is displayed in a circular shape.

6. Output the stress waveform at the stress concentration point based on the grasped relationship between the stress and the top displacement and the measured top displacement, The fatigue damage detection method according to Claim 1, which outputs information on the fatigue damage degree based on the output stress waveform.

7. The fatigue damage detection method according to Claim 1, wherein the fatigue damage degree is calculated based on a fatigue design curve.

8. The fatigue damage detection method according to Claim 1, wherein the remaining life is calculated from the maximum value of the fatigue damage degree for each circumferential direction.

9. Comprising one or more processors, The one or more processors, Acquire the relationship between the stress and the top displacement at the stress concentration point where stress concentrates in the tower-like structure and the information on the acceleration measured by the acceleration sensors installed on the tower-like structure, A fatigue damage detection system that outputs information on the fatigue damage degree for each circumferential direction of the tower-like structure based on the acquired relationship between the stress and the top displacement and the information on the acceleration.

10. The one or more processors acquire the information on the acceleration in a predetermined period and output the information on the fatigue damage degree for each circumferential direction of the tower-like structure in the predetermined period. The fatigue damage detection system according to Claim 9.

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