A method and system for evaluating the mechanical fatigue of high-voltage cables laid on bridges

Abstract

The present invention discloses a method and system for mechanical fatigue assessment of high-voltage cables laid on bridges, which relates to the field of cable fatigue assessment. Currently, there is a lack of a cable fatigue assessment method for factors such as bridge expansion and vibration. The present invention includes the following steps: setting a test cable on a mobile test platform, collecting sensor data to obtain the bending, tensile, and compressive stresses of the cable; repeatedly collecting data by moving a movable box to simulate the stress conditions of the cable; conducting a slicing test on the cable to measure the elongation at break of the cable sheath and insulation; combining the sensor data and the fatigue characteristics of the cable material to fit the shape parameter and scale parameter of the Weibull joint distribution, and predicting the fatigue life, failure probability, and mechanical failure risk of the cable based on the fitting results, so as to determine whether the cable has fatigue failure. Through the combination of the test platform and the Weibull distribution model, this technical solution accurately assesses the mechanical fatigue of high-voltage cables laid on bridges and improves the accuracy of cable life prediction.

Description

Technical Field

[0001] The present invention relates to the field of cable fatigue assessment, and particularly to a method for mechanical fatigue assessment of high-voltage cables laid on bridges. Background Art

[0002] When laying high-voltage cables on bridges, the cables need to withstand the expansion and contraction of the bridge structure and dynamic loads. Due to the differences in the materials and geometric structures of bridges, the amount of expansion and contraction varies among different types of bridges. According to the existing bridge observation data, the expansion and contraction amount of suspension bridges is usually 1 to 2 meters, while that of steel truss bridges is about 1 meter. Therefore, during the process of laying bridge cables, effective measures must be taken to absorb the stress caused by the expansion and contraction of the bridge to prevent the cables from being pulled apart or overly bent.

[0003] Especially in flexible structure bridges such as suspension bridges and cable-stayed bridges, when the truss structures of the central span and the two side spans bear heavy loads, obvious deflection will occur, which leads to the contraction or elongation of the ends of the bridge trusses. Over time, due to the action of dynamic loads, the bridge will generate periodic expansion and contraction and vibration. These factors together cause the cables to bend, stretch and creep during use.

[0004] In this case, the cables not only need to consider their own thermal expansion and contraction, but also must cope with the expansion and contraction and bending of the bridge structure. For long-span bridges, the amount of expansion and contraction of the bridge itself may be very large. If corresponding expansion and contraction absorption measures are not taken, the cables may be overly stretched or bent. When the bridge contracts, the cables will bear excessive bending, resulting in local bending exceeding its limit, which may then cause cable damage. And when the bridge stretches, the cables may bear excessive tension. Especially due to the differences in the elastic moduli of the various layers of the cables and the bridge, it may lead to the failure stress of the cable metal sheath and insulation layer, thus affecting the service life of the cables.

[0005] Due to the mechanical fatigue caused by the expansion and contraction and creep of the bridge to the cables, especially problems such as the fracture of the cable metal sheath and the breakdown of the insulation layer, it directly affects the long-term reliability and safety of the cables. At present, there is still a lack of assessment methods for the mechanical fatigue of high-voltage cables laid on bridges, and there are no mature technical means to effectively predict the mechanical fatigue of cables caused by factors such as expansion and contraction, vibration, etc. during the operation of bridges. Therefore, there is an urgent need to develop an effective assessment method to predict the fatigue failure risks that bridge cables may face during long-term operation, so as to provide a scientific basis for the design, maintenance and replacement of cables. Summary of the Invention

[0006] The technical problem to be solved and the technical task proposed by the present invention are to improve and refine the existing technical solutions, and provide a method and system for mechanical fatigue assessment of high-voltage cables laid on bridges, so as to achieve the purpose of assessing the mechanical fatigue of cables laid on bridges. To this end, the present invention adopts the following technical solutions.

[0007] A method for mechanical fatigue assessment of high-voltage cables laid on bridges, comprising the following steps:

[0008] 1) Install a plurality of hinge connection devices and fixing devices on the test cable, with the hinge connection devices and fixing devices arranged alternately. Install the test cable on a mobile test platform, which includes multiple sections of boxes. The first section of the box is fixed, and the remaining boxes can move left and right. Each box is provided with a suspension point. The cable is connected to the hinge through the hinge connection device and suspended on the suspension point at the top of the box. The fixing device is fixedly connected to the side wall of the box, and the hinge connection device on the test cable is higher than the fixing device, thus forming a test cable arranged in a snake shape. A plurality of first sensors are provided on the test cables on both sides of the middle hinge connection device, and second sensors are provided at both ends of the hinge;

[0009] 2) Collect the information of the first sensors and the second sensors to obtain the initial bending stress, tensile stress, and compressive stress of the test cable.

[0010] 3) Move the movable box, collect the information of the first sensors and the second sensors to obtain the stress condition of the test cable. Repeatedly move the movable box and continuously collect the sensor information until the set number of movements is reached;

[0011] 4) Conduct a slicing test on the cable, measure the elongation at break of the cable sheath and insulation, and combine the collected sensor data. Based on the fatigue characteristics of the cable material, fit the shape parameter and scale parameter of the Weibull joint distribution, and then use the fitting result to predict the fatigue life, failure probability, and mechanical failure risk of the cable, and judge whether the cable has fatigue failure.

[0012] Through installing a plurality of sensors on the test cable and combining the fatigue characteristics of the cable material, this technical solution can monitor the stress state (including bending, tensile, and compressive stresses) of the cable under actual working conditions in real time. Through the collected sensor data, the fatigue problems that may occur in the cable during long-term operation can be accurately predicted, making the prediction of the fatigue life more accurate and avoiding the errors in predicting the life through experience and assumptions in the past.

[0013] Model and evaluate the fatigue failure of cables using the Weibull combined distribution model. The Weibull distribution is a probability distribution widely used in life prediction and reliability analysis, which can provide detailed failure probability and risk analysis for parts such as cable sheaths and insulation layers. By fitting the shape parameter and scale parameter of the Weibull distribution, the mechanical failure risk of cables can be evaluated more scientifically, which is crucial for early identification of potential problems.

[0014] The present invention combines factors such as actual bridge expansion and temperature change on a simulation platform to conduct stress tests on cables under real working conditions. By moving the test platform multiple times, the mechanical loads and stress changes experienced by the cables during actual use are simulated, making the evaluation results more in line with the actual working conditions, rather than just the single load conditions in the laboratory environment. This method can truly reflect the fatigue behavior of bridge cables during actual use.

[0015] Based on accurate fatigue life prediction, maintenance and replacement plans can be formulated in advance before the cables suffer serious damage or fatigue failure, thus avoiding the safety hazards and high maintenance costs brought by sudden cable damage or fracture, significantly improving the operation reliability of the cables, extending their service life, and reducing the risk of unexpected shutdowns and damage.

[0016] This technical solution not only considers the overall failure of the cables, but also conducts slice tests on the cable sheaths and insulation layers respectively to measure the elongation at break. Precise predictions are made for the fatigue failure of different components, providing a scientific basis for design optimization and subsequent maintenance.

[0017] By repeatedly moving the box body and collecting sensor information multiple times, the periodic stress changes suffered by the cables during actual use can be simulated, avoiding the accidental errors that may exist in single measurements and ensuring the reliability of the evaluation results. Repeated tests can better reflect the fatigue cumulative effect that the cables may experience during long-term use, and thus make a more accurate prediction of the safety and life of the cables.

[0018] This technical solution realizes the fatigue test of cables under different working environments through the left-right movement of the box body and different stretching and compression simulations. It effectively simulates the actual stress conditions of the cables under bridge expansion and the influence of the external environment.

[0019] Through a systematic evaluation method, there is no need for overly complex theoretical derivations or a large amount of on-site test data. Only by combining known material properties and sensor data, the fatigue life and failure probability of the cables can be accurately evaluated, thus simplifying the complexity and workload of cable fatigue evaluation and improving work efficiency.

[0020] As a preferred technical means: the moving test platform is provided with three sections of box bodies, and the second section of box body and the third section of box body apply tensile force or thrust synchronously through a hydraulic workstation.

[0021] By means of a mobile test platform with three sections of boxes, the telescopic deformation of cables on bridges can be accurately simulated. The second section of the box and the third section of the box apply tensile or thrust forces synchronously through a hydraulic workstation, enabling a highly restored process of stretching and compressing the cables. This simulation process is closer to the actual working conditions, making the test results reflect the stress conditions of the cables in the real bridge environment.

[0022] The hydraulic workstation can accurately control the applied tensile and thrust forces, ensuring that the change rate and amplitude of the forces conform to the stress fluctuations of the cables under actual working conditions. By applying tensile and thrust forces synchronously, the mechanical responses (such as bending, stretching, compressing, etc.) experienced by the cables on the simulation platform can be made more real. This synchronous control helps to more accurately capture the fatigue characteristics and mechanical failure process of the cables.

[0023] The synchronous control of the hydraulic system makes the applied forces more uniform and controllable, avoiding inconsistencies caused by external factors (such as human operation errors). By precisely controlling the tensile or thrust force applied each time, the repeatability and consistency of the test can be ensured, thereby obtaining more stable and reliable test data. This is crucial for fatigue life prediction.

[0024] Since bridges usually experience periodic telescoping (such as temperature changes, load changes, etc.), the hydraulic workstation can simulate this dynamic telescoping process and, through the design of three sections of boxes, simulate various deformation modes of the cables (such as bending, stretching, and compressing). It can more comprehensively consider the stress changes of the cables under multiple loads and reflect the real fatigue process of the cables.

[0025] By adjusting the hydraulic workstation, the telescoping requirements of different types of bridges can be met. Whether it is a short bridge or an extremely long bridge, the specific telescoping process can be simulated by adjusting the parameters of the hydraulic system (such as pressure, stroke, etc.). This flexibility ensures that the test platform can be applied to various bridge structures, further improving the versatility of this technical solution.

[0026] Since the forces applied by the hydraulic workstation can be accurately controlled and adjusted, combined with the arrangement of sensors on the cables, the stress conditions of the cables under different stress conditions (such as tensile stress, bending stress, compressive stress, etc.) can be comprehensively monitored, providing high-quality data support for subsequent fatigue assessment.

[0027] The hydraulic system can accurately control the periodic changes in the applied load, which is suitable for long-term fatigue tests. Through multiple and long-term cyclic loading, the repeated telescoping loads borne by the cables on the bridges are simulated, thereby providing more data support for the fatigue life prediction of the cables.

[0028] The automatic control system of the hydraulic workstation can accurately achieve the predetermined loading / unloading process, reducing the manual operation errors that may occur in the test and ensuring the accuracy of the experimental data. Compared with the traditional mechanical loading method, the hydraulic system can complete a large number of loading / unloading cycles in a short time, and can accurately control the applied tensile force and thrust force, significantly improving the test efficiency. In addition, the hydraulic system can stably repeat the loading, reducing the time for manual setting and adjustment and saving the experimental cycle.

[0029] As a preferred technical means: both ends of the test cable are fixedly connected to the first box body and the third box body through fixing devices respectively; there are two fixing devices and one hinge connection device on the test cable located on the first box body, and there is one fixing device and one hinge connection device on the test cables of the second box body and the third box body.

[0030] By respectively arranging fixing devices on the first box body and the third box body, and having fixing devices at both ends of the test cable, it can ensure that the cable is stably fixed on the test platform during the test, avoiding inaccurate testing caused by cable sliding or position change. It helps to ensure the uniform force on the test cable and clear force transmission, so that the collected data is more reliable.

[0031] Arranging two fixing devices and one hinge connection device on the test cable of the first box body can provide more degrees of freedom during the force application process, enabling the cable to flexibly bend and deform during the telescopic process. It simulates the real response of the cable when it is stressed in an actual bridge, especially at the expansion joint where the cable may bend and stretch.

[0032] Setting the hinge connection device not only allows the cable to swing freely when stressed, but also can simulate the mechanical behaviors such as rotation, twisting and bending of the cable when it is stressed in an actual bridge. The hinge design provides a fulcrum, making the deformation of the cable more in line with the actual situation and helping to analyze the mechanical properties of the cable under different load conditions. This design better simulates the complex force application process of the cable during the actual operation of the bridge.

[0033] Having one fixing device and one hinge connection device on the cables of the second box body and the third box body can ensure a smoother force transition of the cable between the box bodies. Through the combination of the hinge connection and the fixing device, the cable can smoothly transfer the force change between each test section, thus avoiding inaccurate test results caused by sudden force change or uneven force transmission.

[0034] Multiple fixing devices and hinge connection devices are provided on the cable, enabling the cable to generate different bending stresses and tensile / compressive stresses at different positions, thus facilitating the arrangement of sensors at different test points to obtain more detailed stress data. This is crucial for evaluating the fatigue conditions of the cable at different parts, enabling multi-point monitoring, and providing more comprehensive data support for fatigue life prediction and fault diagnosis.

[0035] The arrangement of the fixing devices and hinge connection devices at both ends of the cable can be flexibly adjusted according to the specific structure of the bridge. On different types of bridges (such as suspension bridges, cable-stayed bridges, etc.), the fixing and connection methods of the cable can be adjusted as needed to better simulate the stress conditions of the cable on different bridge structures. This flexibility enables this solution to be applicable to a variety of different bridge cable test scenarios.

[0036] By setting multiple fixing devices and hinge connection devices, it is possible to effectively simulate the repeated stretching, bending, etc. of the cable in the actual environment, thus comprehensively evaluating the fatigue performance of the cable. It helps to evaluate whether the cable will be damaged, cracked, or suffer other mechanical failures under different working conditions, and thus make accurate judgments on the service life, maintenance cycle, and replacement time of the cable.

[0037] The fixing devices and hinge connection devices make the test equipment more stable and easy to operate. During the test process, the cable does not need to be frequently adjusted or re-arranged, the operation process is more simplified, and the test efficiency can be improved. At the same time, the system has a high degree of automation, reducing the influence of human operation, and helping to improve the accuracy and repeatability of the test results.

[0038] Combined with the arrangement of the fixing devices and hinge connection devices, this solution can accurately capture the stress changes of the cable under different tensile, bending, and compressive conditions. Combining the data collected by the sensors, accurate fatigue assessment can be carried out. Through multi-point stress measurement, the fatigue characteristics of the cable material are evaluated, and finally, through mathematical models such as the Weibull distribution, the prediction accuracy of the mechanical fatigue life, fault probability, and risk of the cable is improved.

[0039] As a preferred technical means: A plurality of first sensors are provided on the surface of the test cable inside and between the two fixing devices on both sides of the suspension point of the second box body, and the first sensors located between the two fixing devices are closely attached to the outer circumference of the cable through cable clamps.

[0040] Sensors are installed in the critical areas of the cable (i.e., the cable surface between the fixing devices on both sides of the suspension point of the second - section box body), which not only monitor the force conditions at the highest point but also at the lowest point, and can more accurately monitor the stress changes of the cable during the force - bearing process. These areas are highly sensitive areas where the cable is stressed. The arrangement of sensors helps to capture the local stress conditions when the cable bends, stretches or compresses, ensuring the high precision of the monitoring data. The first sensor between the two fixing devices is closely attached to the outer circumference of the cable through a cable clamp, which can ensure the close contact between the sensor and the cable surface, thus improving the accuracy of data collection. The close contact between the cable surface and the sensor can avoid signal loss or errors caused by poor contact, enhancing the reliability of stress measurement.

[0041] By arranging sensors on the cable surface between the two fixing devices, the tensile, compressive or bending stresses on the cable in this area can be accurately measured. Timely identification of possible local stress concentration or deformation of the cable can be achieved, avoiding cable damage or failure.

[0042] By arranging multiple sensors in the critical force - bearing areas of the cable and combining with the fatigue characteristics of the cable material, the shape parameters and scale parameters of the Weibull joint distribution can be more accurately fitted, thus improving the prediction accuracy of the cable fatigue life and mechanical failure risk. It helps to optimize the cable design and maintenance strategies and extend the service life of the cable.

[0043] The sensor is closely attached to the outer surface of the cable, which can provide accurate data feedback when there are slight changes in the force on the cable. It increases the sensitivity to detect cable fatigue damage, can timely detect the fatigue damage accumulated during the long - term use of the cable, provides a basis for early repair or replacement, and reduces the accident risk of bridge facilities.

[0044] By simultaneously monitoring the stress changes at multiple key positions of the cable with multiple sensors, the stress distribution of the cable during the entire test process can be more comprehensively analyzed. Combining with the acquisition of real - time data, adjustments and optimizations can be made immediately during the force - bearing process of the cable, thus improving the real - time performance and response ability of the test.

[0045] As an optimal technical means: the length of the hinge is 0.5 - 1.5 meters; the working stroke of the hydraulic workstation is 0.5 - 1.5 meters; the length of the box body is 4 - 10 meters. By reasonably setting the hinge length, hydraulic working stroke and box - body length, not only the accuracy, reliability and controllability of the test are improved, but also the test requirements of different cables can be flexibly adapted. The overall scheme optimizes the test process, improves the representativeness and efficiency of the test, and ensures more accurate prediction of the cable fatigue life and failure risk.

[0046] As a preferred technical measure: the Weibull joint distribution function is used to conduct a probability assessment of the mechanical failure of the cable. Among them, the Weibull distribution function of the mechanical failure of the protective layer is:

[0047] ;

[0048] The Weibull distribution function of the mechanical failure of the insulation is:

[0049] ;

[0050] In the formula: is the shape parameter of the protective layer, is the scale parameter of the protective layer; is the shape parameter of the insulation layer, is the scale parameter of the insulation layer;

[0051] The fatigue life assessment is carried out according to the shape parameter and scale parameter obtained by fitting the test data.

[0052] This technical solution respectively models the mechanical failures of the cable sheath, insulation and cable body, and combines the Weibull distribution functions of the sheath and insulation parts with the joint distribution function of the overall cable failure, ensuring a comprehensive assessment of the overall performance of the cable; better understanding the aging and damage conditions of each component of the cable during actual use, so as to conduct a more comprehensive risk assessment. Using the Weibull joint distribution function to conduct a probability assessment of the mechanical failure of the cable, through accurately fitting the shape parameter and scale parameter, it can provide a reliable prediction for the fatigue life and failure risk of the cable. It not only comprehensively considers the failure characteristics of each part of the cable, but also can accurately model according to the test data, significantly improving the scientificity and accuracy of the assessment.

[0053] As a preferred technical measure: in step 4), the number of repeated movements is 30 times, corresponding to 30 times of bending stress changes and 60 times of bending stress borne by the metal sheath during 30 years of operation.

[0054] By setting the number of repeated movements to 30 times, the bending stress changes experienced by the cable and the bending stress borne by the metal sheath during 30 years of operation are simulated. This makes the test closer to the actual stress conditions of the cable during actual use, reflects the stress changes and fatigue accumulation that the cable may encounter during many years of operation, and thus can more accurately evaluate the long-term reliability and fatigue life of the cable.

[0055] Another object of the present invention is to provide a mechanical fatigue assessment system for high-voltage cables laid on bridges. A mechanical fatigue assessment system for high-voltage cables laid on bridges includes:

[0056] A mobile test platform, which is composed of multiple boxes. The multiple boxes include at least one fixed box and at least two movable boxes, and the movable boxes can reciprocate along the axial direction of the platform;

[0057] Hinge connection devices and fixing devices, which are alternately arranged on the test cable to fix the test cable in a snake shape on the mobile test platform;

[0058] A sensor device, which includes multiple first sensors and multiple second sensors. The first sensors are installed on both sides of the hinge connection device in the middle of the test cable, and the second sensors are installed at both ends of the hinge, respectively used to collect the bending stress, tensile stress and compressive stress of the cable;

[0059] A control unit, which is used to control the movement of the movable box, record the measurement data of the sensors, and evaluate the fatigue life of the cable according to the measurement data;

[0060] A slicing test device, which is used to conduct a slicing test on the cable, measure the elongation at break of the cable sheath and insulation, and feed back the elongation at break data to the control unit;

[0061] A data analysis unit, which is used to fit the shape parameter and scale parameter of the Weibull joint distribution function based on the measurement data and the elongation at break data, and predict the fatigue life and failure probability of the cable.

[0062] This system installs the cable in a snake shape through the mobile test platform, hinge connection devices and fixing devices, and combines multiple sensors to real-time collect the stress data of the cable at different positions, which can more comprehensively simulate the dynamic mechanical changes and environmental stresses suffered by the cable in practical applications such as bridges, and improve the authenticity and effectiveness of the test.

[0063] The system collects the bending stress, tensile stress and compressive stress of the cable through sensors, combines the slicing test to measure the elongation at break of the cable sheath and insulation, and uses the Weibull joint distribution model to predict the fatigue life and failure probability. This makes the cable fatigue assessment more accurate, helps to accurately judge the usage status and remaining life of the cable, so as to give early warning and formulate maintenance plans.

[0064] The control unit of the system can accurately control the reciprocating motion of the movable box, simulate the long-term stress situation of the cable, and record the sensor data in real time. The data analysis unit can obtain more scientific cable fatigue assessment results through the processing and fitting of these data, and further enhance the reliability of the assessment by combining the elongation at break data, avoiding the errors brought by a single test method.

[0065] The system is designed considering the actual working conditions of long-term cable operation. By repeatedly simulating the stress changes of the cable during long-term use, the fatigue life prediction is made more consistent with the actual service life of the cable.

[0066] The data analysis unit combines the slice test and stress test data for analysis, deeply evaluates the mechanical failure of the cable using the fitted Weibull distribution parameters, provides accurate remaining life and failure probability information, and provides a regular assessment report for the power company to optimize the life cycle management of the cable.

[0067] As a preferred technical means: The mobile test platform includes three sections of boxes, and the second and third sections of boxes apply tensile or thrust forces synchronously through a hydraulic workstation.

[0068] As a preferred technical means: The length of the hinge connection device is 0.5 - 1.5 meters. The fixing device is fixedly connected to the side wall of the box. The cable is connected to the suspension point at the top of the box through the hinge connection device; the working stroke of the hydraulic workstation is 0.5 - 1.5 meters, which is used to simulate the thermal expansion and contraction process of the bridge and provide corresponding tensile and compressive forces for the cable; the length of the box is 4 - 10 meters, and each box is provided with a suspension point. The cable is connected to the suspension point through the hinge device.

[0069] By applying tensile or thrust forces synchronously through the hydraulic workstation, it is possible to simulate the stress changes borne by the cable during the thermal expansion and contraction process of the bridge, enabling the experimental platform to accurately reproduce the working state of the bridge cable in different temperature environments, thereby more realistically evaluating the fatigue life and failure risk of the cable. The introduction of the hydraulic workstation can flexibly apply precise tensile and thrust forces during the test, further enhancing the dynamic loading capacity of the experiment. This enables the cable to simulate the actual stress during long-term use during the force application process, ensuring a comprehensive evaluation of the cable's performance under different environments and conditions.

[0070] The system adopts a three-section box design. Each box is provided with a suspension point, and the cable is fixed to the suspension point through the hinge connection device, which can simulate the serpentine arrangement of the cable and further restore the mechanical performance during actual operation. The length of the box is 4 - 10 meters, providing sufficient space for long-term fatigue testing while avoiding test limitations due to too small space.

[0071] The second and third sections of boxes apply tensile or thrust forces synchronously through the hydraulic workstation, ensuring that the movement and mechanical forces of the two boxes are synchronized, and avoiding inaccurate signal interference caused by asynchronous movement. This design improves the accuracy of the experiment, makes the stress changes more in line with the actual situation, and can more effectively evaluate the performance of the cable during long-term use.

[0072] This technical solution can conduct mechanical tests at multiple stress points (connected by different suspension points and hinge connection devices) by precisely controlling the stress state of the cable, improving the accuracy and reliability of the experiment. It helps to conduct a more comprehensive cable fatigue test under different working conditions, ensuring that the evaluation results are more accurate and scientific.

[0073] Beneficial effects: By combining the test platform and the Weibull distribution model, this technical solution realizes the precise evaluation of the mechanical fatigue of high-voltage cables laid on bridges. It improves the accuracy of cable life prediction, effectively reduces the costs of maintenance and replacement, and reduces the risk of sudden cable failures. Through a comprehensive analysis of cable fatigue failures, the present invention provides an important theoretical basis and practical guidance for the design, use, and maintenance of cables. Specifically:

[0074] 1. By installing multiple sensors on the test cable and combining with the fatigue characteristics of the cable material, this technical solution can monitor the stress state of the cable (including bending, tensile, and compressive stresses) under actual working conditions in real time. Based on the sensor data collected, it is possible to accurately predict the fatigue problems that may occur during the long-term operation of the cable, making the prediction of fatigue life more accurate and avoiding the errors in predicting life through past experience and assumptions.

[0075] 2. The Weibull joint distribution model is used to model and evaluate the fatigue failure of the cable. The Weibull distribution is a probability distribution widely used in life prediction and reliability analysis, which can provide detailed failure probability and risk analysis for parts such as cable sheaths and insulation layers. By fitting the shape parameter and scale parameter of the Weibull distribution, the mechanical failure risk of the cable can be evaluated more scientifically, which is crucial for identifying potential problems in advance.

[0076] 3. The present invention combines factors such as actual bridge expansion and temperature changes on the simulation platform to conduct stress tests on the cable under real working conditions. By moving the test platform multiple times, it simulates the mechanical loads and stress changes experienced by the cable during actual use, making the evaluation results more in line with the actual working conditions, rather than just the single load condition in the laboratory environment. This method can truly reflect the fatigue behavior of bridge cables during actual use.

[0077] 4. This technical solution not only considers the overall failure of the cable, but also conducts slice tests on the cable sheath and insulation layer respectively to measure the elongation at break. It makes accurate predictions for the fatigue failures of different components, providing a scientific basis for design optimization and subsequent maintenance.

[0078] 5. By repeatedly moving the box body and collecting sensor information multiple times, it is possible to simulate the periodic stress changes suffered by the cable during actual use, avoid the accidental errors that may exist in single measurement, and ensure the reliability of the evaluation results. Repeated tests can better reflect the fatigue cumulative effect that the cable may experience during long-term use, and thus make a more accurate prediction of the cable's safety and lifespan.

[0079] 6. This technical solution realizes the fatigue test of the cable under different working environments through the left-right movement of the box body and different stretching and compression simulations. It effectively simulates the real stress conditions of the cable under bridge expansion and the influence of the external environment.

[0080] 7. Through a systematic evaluation method, there is no longer a need for overly complex theoretical derivations or a large amount of on-site test data. Only by combining known material properties and sensor data can the fatigue life and failure probability of the cable be accurately evaluated, thereby simplifying the complexity and workload of cable fatigue evaluation and improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 is the working principle diagram of the present invention.

[0082] Figure 2 is the schematic diagram of the installation of the first sensor of the present invention.

[0083] Figure 3 is the schematic diagram of the installation of the second sensor of the present invention.

[0084] In the figure: 1. Box body; 2. Suspension point; 3. Hinge; 4. Hinge connection device; 5. Fixing device; 6. Test cable; 7. First sensor; 8. Second sensor; 9. Cable clamp; 10. Bolt; 11. Cable sheath; 12. Insulation layer; 13. Hydraulic workstation; 14. Steel pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0085] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings of the specification.

[0086] Embodiment 1:

[0087] A method for mechanical fatigue evaluation of high-voltage cables laid on bridges, comprising the following steps:

[0088] S1: Install multiple hinge connection devices 4 and fixing devices 5 on the test cable 6. The hinge connection devices 4 and the fixing devices 5 are arranged alternately, and install the test cable 6 on the mobile test platform. The mobile test platform includes multiple sections of boxes 1, where the first section of the box 1 is fixed, and the remaining boxes 1 can move left and right. Each box 1 is provided with a suspension point 2. The cable is connected to the hinge 3 through the hinge connection device 4 and suspended on the suspension point 2 at the top of the box 1. The fixing device 5 is fixedly connected to the side wall of the box 1, and the hinge connection device 4 on the test cable 6 is higher than the fixing device 5, thereby forming a test cable 6 arranged in a snake shape. On the test cable 6 on both sides of the middle hinge connection device 4, multiple first sensors 7 are provided, and second sensors 8 are provided at both ends of the hinge 3;

[0089] In this embodiment, three sections of boxes 1 are adopted. The first section of the box 1 is fixed, and the second section of the box 1 and the third section of the box 1 are synchronously applied with tensile force or thrust through the hydraulic workstation 13. By setting three sections of boxes 1 and using the hydraulic workstation 13 to synchronously apply tensile force or thrust, this technical solution can accurately simulate the stress situation of the cable during the actual bridge expansion and contraction process, comprehensively evaluate the fatigue performance of the cable, reduce experimental errors, and provide an efficient and accurate method for evaluating the mechanical fatigue of the cable.

[0090] Both ends of the test cable 6 are fixedly connected to the first section of the box 1 and the third section of the box 1 through the fixing device 5 respectively; among them, two fixing devices 5 and one hinge connection device 4 are provided on the test cable 6 located in the first section of the box 1, and one fixing device 5 and one hinge connection device 4 are provided on the test cable 6 of the second section of the box 1 and the third section of the box 1. Through the design of setting multiple fixing devices 5 and hinge connection devices 4 at both ends of the test cable 6, the real stress situation of the cable in the bridge environment can be effectively simulated, ensuring the stability, uniform stress and smooth stress transition of the cable during the test process.

[0091] Multiple first sensors 7 are provided on the surface of the test cable 6 inside and between the two fixing devices 5 on both sides of the suspension point 2 of the second section of the box 1. Among them, the first sensors 7 located between the two fixing devices 5 are closely attached to the outer circumference of the cable through the cable clamp 9. As Figure 2 shown, in this embodiment, the cable clamp 9 adopts the method of butt joint and is fixed at both ends with bolts 10 to fix the first sensor 7 on the test cable 6. The outermost layer of the test cable 6 is the cable sheath 11, the middle layer is the insulating layer 12, and the innermost layer is the conducting wire core. The first sensor 7 is closely attached to the outside of the cable sheath 11.

[0092] As Figure 3 shown, the second sensor 8 is arranged between the suspension point 2 of the second section of the box 1 and the hinge 3.

[0093] In this embodiment, the length of the hinge 3 is 1 meter; the working stroke of the hydraulic workstation 13 is 1 meter; and the length of the box body 1 is 6 meters. By reasonably setting the length of the hinge 3, the hydraulic working stroke, and the length of the box body 1, not only the accuracy, reliability, and controllability of the test are improved, but also the test requirements of different cables can be flexibly adapted. The overall solution optimizes the test process, enhances the representativeness and efficiency of the test, and ensures more accurate prediction of the cable fatigue life and failure risk.

[0094] S2: Collect the information of the first sensor 7 and the second sensor 8 to obtain the initial bending stress, tensile stress, and compressive stress of the test cable 6.

[0095] S3: Move the movable box body 1, collect the information of the first sensor 7 and the second sensor 8 to obtain the stress condition of the test cable 6, repeatedly move the movable box body 1 and continuously collect the sensor information until 30 times are reached.

[0096] During the test, in the first step, measure the stress values of the cable in the expansion joint section under normal conditions; in the second step, compress and measure the stress values at each place; in the third step, stretch and measure the stress values at each place; in the fourth step, swing and measure the torsional stress values at each place.

[0097] Considering that the cable operates on the bridge for more than 30 years, there is a maximum elongation in winter and a maximum compression in summer every year. When there is the maximum elongation, the cable bears tensile stress, and the bending radius can basically meet the bending requirements. However, the metal sheath wrinkles of the cable will produce a single bend, and the expansion compensation device and the fixed transition section cable also bear a single stress change at the same time; when there is the maximum compression, the bending radius of the cable may be less than the specified value, the cable metal sheath bears another bend, and the transition point also bears a single stress change. Therefore, the cable must satisfy 30 times of bending stress changes during 30 years of operation, and the bending stress borne by the metal sheath should reach 60 times. Therefore, 30 complete measurements need to be carried out as a whole.

[0098] S4: Conduct a slicing test on the cable, measure the elongation at break of the cable sheath 11 and the insulation, and combine the collected sensor data. Based on the fatigue characteristics of the cable material, fit the shape parameter and scale parameter of the Weibull joint distribution, and then use the fitting results to predict the fatigue life, failure probability, and mechanical failure risk of the cable, and judge whether the cable has fatigue failure.

[0099] The Weibull joint distribution function is used to evaluate the probability of mechanical failure of the cable. Among them, the Weibull distribution function of the mechanical failure of the protective layer is:

[0100]

[0101] The Weibull distribution function of the mechanical failure of the insulation is:

[0102]

[0103] Wherein: is the shape parameter of the protective layer, is the proportional parameter of the protective layer; is the shape parameter of the insulating layer, is the proportional parameter of the insulating layer;

[0104] The fatigue life is evaluated according to the shape parameters and scale parameters obtained by fitting the test data.

[0105] The Weibull joint distribution function is used to evaluate the probability of cable mechanical failure. By accurately fitting the shape parameters and scale parameters, reliable predictions can be provided for the fatigue life and failure risk of the cable. This method not only comprehensively considers the failure characteristics of each part of the cable, but also can accurately model according to the test data, significantly improving the scientificity and accuracy of the evaluation.

[0106] This technical solution realizes the accurate evaluation of the mechanical fatigue of high-voltage cables laid on bridges by combining the test platform and the Weibull distribution model. It improves the accuracy of cable life prediction, effectively reduces the costs of maintenance and replacement, and reduces the risk of sudden cable failures. Through the comprehensive analysis of cable fatigue failures, the present invention provides important theoretical basis and practical guidance for the design, use and maintenance of cables.

[0107] According to the measured data, calculations and analyses are carried out. When the data is less than the allowable value of the cable, it indicates that the design is okay; when the measured data exceeds the allowable value, it is confirmed whether the cable is damaged (including inside and outside) under such circumstances. If damage occurs, find out the reason.

[0108] The specific achievable effects of this embodiment:

[0109] (1) The fatigue assessment method based on the Weibull joint distribution can more accurately predict the fatigue life of the cable under actual working conditions, thus improving the accuracy of the assessment.

[0110] (2) It can more accurately predict the failure probability and life distribution of the cable in different environments, thus reducing the risks and costs of future maintenance and replacement.

[0111] (3) By more comprehensively considering the fatigue characteristics, this method helps to identify potential problems and risk points in advance and reduce the occurrence of accidents.

[0112] Embodiment 2:

[0113] A mechanical fatigue assessment system for high-voltage cables laid on bridges includes:

[0114] A mobile test platform, such asFigure 2 As shown, the platform is composed of three boxes 1, including one fixed box 1 and two movable boxes 1. The movable box 1 can reciprocate along the axial direction of the platform;

[0115] Hinge connection devices 4 and fixing devices 5. The hinge connection devices 4 and the fixing devices 5 are alternately arranged on the test cable 6 to fix the test cable 6 in a snake shape on the moving test platform;

[0116] Sensor device. The sensor device includes a plurality of first sensors 7 and a plurality of second sensors 8. The first sensors 7 are installed on both sides of the hinge connection device 4 in the middle of the test cable 6, and the second sensors 8 are installed at both ends of the hinge 3, which are respectively used to collect the bending stress, tensile stress and compression stress of the cable;

[0117] Control unit, which is used to control the movement of the movable box 1, record the measurement data of the sensors, and evaluate the fatigue life of the cable according to the measurement data;

[0118] Slice test device, which is used to perform slice tests on the cable, measure the elongation at break of the cable sheath 11 and the insulation, and feed back the elongation at break data to the control unit;

[0119] Data analysis unit, which is used to fit the shape parameter and scale parameter of the Weibull joint distribution function based on the measurement data and the elongation at break data, and predict the fatigue life and failure probability of the cable.

[0120] This system effectively improves the prediction accuracy of the cable fatigue life by accurately simulating the long-term use stress of the cable in the bridge laying environment and comprehensively analyzing in combination with the slice test data. By adopting the Weibull joint distribution model for fatigue assessment, the system can provide a scientific basis for the maintenance, monitoring and replacement of power facilities, reduce the risk of faults, and ensure the long-term stable operation of the power system.

[0121] For the convenience of the movement of the box 1, steel pipes 14 can be installed at the lower part of the box 1 for support, and slide rails are installed at the lower part of the steel pipes 14 for linear movement. The synchronous hydraulic workstation 13 installed at the lower part of the steel pipes 14 of the two movable boxes 1 applies tensile force and pressure to the box 1 to simulate the process of thermal expansion and contraction of the bridge.

[0122] It can be understood that the detailed function implementation of the above platform, device and unit can refer to the introduction in the foregoing method embodiments, and no other elaboration will be made here.

[0123] A method and system for evaluating the mechanical fatigue of high-voltage cables laid on bridges as described above are specific embodiments of the present invention, which have already reflected the substantial features and progress of the present invention. According to actual usage needs, equivalent modifications can be made to its shape, structure, etc. under the inspiration of the present invention, and all are within the protection scope of this solution.

Claims

1. A method for evaluating the mechanical fatigue of high-voltage cables laid on bridges, characterized in that It includes the following steps: 1) Install a plurality of hinge connection devices (4) and fixing devices (5) on the test cable (6). The hinge connection devices (4) and the fixing devices (5) are arranged alternately. Install the test cable (6) on the mobile test platform. The mobile test platform includes multiple sections of boxes (1), where the first section of the box (1) is fixed, and the remaining boxes (1) can move left and right. Each box (1) is provided with a suspension point (2). The cable is connected to the hinge (3) through the hinge connection device (4) and suspended on the suspension point (2) at the top of the box (1). The fixing device (5) is fixedly connected to the side wall of the box (1), and the hinge connection device (4) on the test cable (6) is higher than the fixing device (5), so as to form a test cable (6) arranged in a snake shape. A plurality of first sensors (7) are arranged on the test cable (6) on both sides of the middle hinge connection device (4), and second sensors (8) are arranged at both ends of the hinge (3); 2) Collect the information of the first sensors (7) and the second sensors (8) to obtain the bending stress, tensile stress and compressive stress of the initial test cable (6); 3) Move the movable box (1), collect the information of the first sensors (7) and the second sensors (8) to obtain the force condition of the test cable (6). Repeatedly move the movable box (1) and continuously collect the sensor information until the set number of movements is reached; 4) Conduct a slicing test on the cable, measure the elongation at break of the cable sheath (11) and the insulation, and combine the collected sensor data. Based on the fatigue characteristics of the cable material, fit the shape parameter and scale parameter of the Weibull joint distribution, and then use the fitting result to predict the fatigue life, failure probability and mechanical failure risk of the cable, and judge whether the cable has fatigue failure; Adopt the Weibull joint distribution function to conduct a probability assessment of the mechanical failure of the cable. Among them, the Weibull distribution function of the mechanical failure of the protective layer is: The Weibull distribution function of the mechanical failure of the insulation is: In the formula: is the shape parameter of the protective layer, is the proportional parameter of the protective layer; is the shape parameter of the insulating layer, is the proportional parameter of the insulating layer; Conduct a fatigue life assessment according to the shape parameter and scale parameter obtained by fitting the test data; Both ends of the test cable (6) are fixedly fixed to the first section of the box (1) and the third section of the box (1) through the fixing device (5); among them, there are two fixing devices (5) and one hinge connection device (4) on the test cable (6) located in the first section of the box (1), and the test cable (6) of the second section of the box (1) and the third section of the box (1) is provided with one fixing device (5) and one hinge connection device (4); A plurality of first sensors (7) are arranged on the surface of the test cable (6) inside and between the two fixing devices (5) on both sides of the suspension point (2) of the second section of the box (1). Among them, the first sensors (7) located between the two fixing devices (5) are closely attached to the outer circumference of the cable through the cable clamp (9).

2. The mechanical fatigue assessment method for high-voltage cables laid on bridges according to claim 1, characterized in that: The mobile test platform is provided with three sections of boxes (1), and the second section of the box (1) and the third section of the box (1) are synchronously applied with tensile force or thrust through the hydraulic workstation (13).

3. A mechanical fatigue assessment method for high-voltage cables laid on bridges according to claim 1, characterized in that: The length of the hinge (3) is 0.5 - 1.5 meters; the working stroke of the hydraulic workstation (13) is 0.5 - 1.5 meters; the length of the box (1) is 4 - 10 meters.

4. A method for evaluating the mechanical fatigue of high-voltage cables laid on bridges according to claim 1, characterized in that: In step 4), the number of repeated movements is 30 times, corresponding to 30 times of bending stress changes and 60 times of bending stresses borne by the metal sheath during 30 years of operation.

5. A mechanical fatigue assessment system for high-voltage cables laid on bridges, characterized in that: Adopt a mechanical fatigue assessment method for high-voltage cables laid on bridges according to any one of claims 1-4; the system includes: A mobile test platform, which is composed of a plurality of boxes (1), the plurality of boxes (1) includes at least one fixed box (1) and at least two movable boxes (1), and the movable boxes (1) can reciprocate along the axial direction of the platform; Hinge connection devices (4) and fixing devices (5), the hinge connection devices (4) and the fixing devices (5) are alternately arranged on the test cable (6) to fix the test cable (6) in a snake shape on the mobile test platform; A sensor device, the sensor device includes a plurality of first sensors (7) and a plurality of second sensors (8), the first sensors (7) are installed on both sides of the hinge connection device (4) in the middle of the test cable (6), and the second sensors (8) are installed at both ends of the hinge (3), and are respectively used to collect the bending stress, tensile stress and compressive stress of the cable; A control unit, which is used to control the movement of the movable box (1), record the measurement data of the sensor, and evaluate the fatigue life of the cable according to the measurement data; A slicing test device, which is used to perform a slicing test on the cable, measure the elongation at break of the cable sheath (11) and insulation, and feed back the elongation at break data to the control unit; A data analysis unit, which is used to fit the shape parameter and scale parameter of the Weibull joint distribution function based on the measurement data and the elongation at break data, and predict the fatigue life and failure probability of the cable.

6. The mechanical fatigue evaluation system for high-voltage cables laid on bridges according to claim 5, characterized in that: The mobile test platform includes three boxes (1), and the second and third boxes (1) are synchronously applied with tensile force or thrust through a hydraulic workstation (13).

7. A mechanical fatigue evaluation system for high-voltage cables laid on bridges according to claim 6, characterized in that: The length of the hinge connection device (4) is 0.5-1.5 meters, the fixing device (5) is fixedly connected to the side wall of the box (1), and the cable is connected to the suspension point (2) at the top of the box (1) through the hinge connection device (4); the working stroke of the hydraulic workstation (13) is 0.5-1.5 meters, which is used to simulate the thermal expansion and contraction process of the bridge and provide the corresponding tensile force and pressure for the cable; the length of the box (1) is 4-10 meters, and each box (1) is provided with a suspension point (2), and the cable is connected to the suspension point (2) through a hinge (3) device.

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