Miter gate structure fatigue test loading device and test method

Abstract

The invention belongs to the field of hydraulic engineering structure safety, and particularly relates to a miter gate structure fatigue test loading device and a test method.The miter gate structure fatigue test loading device comprises a test platform base provided with a to-be-tested model test piece and loading action equipment; the loading action equipment comprises a rigid reaction frame and an actuator; the hydraulic oil cylinder platform is used for providing a power source for applying force to the actuator; the power source control system is used for controlling the hydraulic oil cylinder platform; the industrial cooling-water machine is used for circularly cooling hydraulic oil in the hydraulic oil cylinder platform; the stroke limit switch controller is used for setting and controlling the stroke of a piston rod of the actuator and regulating and controlling the thrust; the stroke reciprocating counter is connected with the stroke limit switch controller and is used for automatically recording the complete reciprocating pushing times of the actuator; according to the method, the finite element analysis result of the prototype structure serves as direct input of the physical test model, support is provided for design and loading control of the physical test model, and high-fidelity reproduction of the stress state of the actual working condition is achieved.

Description

Technical Field

[0001] This invention belongs to the field of structural safety in water conservancy engineering, and specifically relates to a fatigue testing loading device and testing method for a herringbone gate structure. Background Technology

[0002] Miter gates in ship locks are the most widely used due to their simple structure, clear stress distribution, rapid opening and closing, and significant advantages in adapting to high water heads. However, as a high-head, large-span, thin-walled steel structure, miter gates commonly suffer from structural fatigue damage after long-term service. Cracks initiate and propagate at stress concentration points, which may eventually lead to structural failure, seriously threatening the navigation efficiency of the ship lock and the flood control safety of the hub.

[0003] In existing technologies, research on fatigue of miter gate structures mainly relies on the following three methods: First, by establishing a refined finite element model of the miter gate, stress distribution cloud maps can be effectively calculated, and the maximum stress point can be located. Although this method can reveal the mechanical behavior of the structure well, it is essentially a calculation of an idealized mathematical model and cannot accurately simulate the microscopic defects of the material itself, welding residual stress, and the real crack initiation and propagation laws under long-term loads. The reliability of its results still needs to be verified through physical model tests or practice. Second, prototype online monitoring, that is, installing sensors on existing miter gates for long-term real-time monitoring. Although this method can obtain real structural response data, it is a kind of "passive" ex-post monitoring. It can only alarm after cracks have appeared and propagated to a certain extent, and cannot proactively assess its fatigue resistance during the structural design or modification stage. In addition, the monitoring cycle is long and costly, and it cannot test under extreme working conditions or destructive situations. Thirdly, traditional physical model tests: Currently, fatigue tests conducted in laboratories mostly use standard specimens or extremely simplified structural models. The compilation of their load spectra is often based on theoretical estimations or simplified assumptions, and fails to use real stress fields verified by finite element analysis as input. Therefore, it is difficult to truly and reliably reflect the crack initiation and propagation laws of key parts of the prototype structure.

[0004] These technologies have significant limitations, specifically: numerical simulations cannot realistically reproduce the material fatigue failure process; prototype monitoring is passive and has an excessively long cycle; and traditional physical model tests suffer from load spectrum distortion, leading to a severe disconnect between the test conditions and actual conditions, resulting in low confidence levels and an inability to provide accurate and effective guidance for engineering practice. Therefore, there is an urgent need for a loading device and method for fatigue testing of miter gates that can highly reproduce complex actual stress states, effectively accelerate the testing process, and provide reliable results. This would provide a scientific basis and technical support for the safety assessment of miter gate fatigue performance and the formulation of preventative maintenance strategies. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art by proposing a fatigue test loading device and test method for a herringbone gate structure, so as to improve the reliability and efficiency of the analysis of crack initiation and propagation laws of herringbone gates.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a fatigue testing loading device for a herringbone gate structure, comprising: The test platform base, the test model specimen, and the loading device are located on the test platform base. The test model specimen is fixed on the test platform base. The loading device applies force to the test model specimen through the slide rail component to simulate the stress environment of the miter gate. The loading device includes a rigid reaction frame and an actuator. The rigid reaction frame is fixed on the test platform base, and the actuator is located on the side of the rigid reaction frame facing the test model specimen. A hydraulic cylinder platform, connected to an actuator via pipes, is used to provide a power source for the force applied by the actuator; The power source control system is used to control the hydraulic cylinder platform; Industrial chillers are used to connect the inlet and outlet water pipes to the cooling circuit of the hydraulic cylinder platform for circulating cooling of the hydraulic oil in the hydraulic cylinder platform. The travel limit switch controller is installed above the cylinder of the actuator to set and control the piston rod stroke of the actuator and adjust the piston rod thrust. The stroke reciprocating counter is connected to the stroke limit switch controller and is used to automatically record the number of complete reciprocating strokes of the actuator; As a further preferred option, the fatigue test loading device for the miter gate structure also includes: Strain gauge sensors are uniformly attached to the back of the test specimen to monitor the stress on the specimen in real time. A hydraulic sensor is installed in the hydraulic circuit of the actuator to monitor and provide feedback on the actuator's output thrust in real time.

[0007] As a further preferred option, the fatigue test loading device for the herringbone gate structure also includes a wireless dynamic acquisition instrument and a data processing terminal. The signals from the strain gauge and hydraulic sensor are recorded in real time by the wireless dynamic acquisition instrument and transmitted to the data processing terminal. The received signals are calculated, displayed and stored by the DHDAS dynamic signal acquisition and analysis system software on the data processing terminal, and the accurate values ​​of the stress of the specimen and the thrust of the actuator are obtained in real time.

[0008] The present invention provides a fatigue testing method for a herringbone gate structure, characterized by comprising the following steps: Step 1: Prototype finite element analysis. Based on the geometric and material parameters of the original herringbone gate, a three-dimensional finite element simulation model is established to simulate its mechanical response under circulating hydrodynamic load. Stress analysis is performed through the finite element simulation model to determine the stress distribution of the herringbone gate and extract the location of the maximum bending stress to obtain the maximum stress value. Step 2: Physical test model design. Based on the long-term immersion area at the bottom of the gate (the area subjected to water force load) and the stress distribution determined by the finite element analysis at the bottom of the gate, key parts (the rear flange of the gate, which is the area of ​​maximum bending stress concentration) are selected to make model specimens. To ensure the actual response of the structure under long-term load, the width, height and material properties of the model specimens are strictly consistent with the prototype.

[0009] Step 3. Design and construction of the loading device, including: The cyclic testing unit includes: an actuator, a rigid reaction frame, a test model specimen, and a slide rail assembly mounted on a test platform base; the actuator is used to apply circulating hydrodynamic loads simulating actual working conditions; the rigid reaction frame provides stable support for the actuator; the test model specimen is manufactured and determined according to step 2, with its tail end fixed to the platform base by high-strength welding, and its front bottom supported on the slide rail, so as to reproduce the actual stress state under reciprocating loading; The system power unit includes: a power source, a power source control system, and a cooling system connected in sequence; the power source can be any of a hydraulic cylinder, a pneumatic cylinder, or a drive motor; the power source control system is responsible for the start and stop operation of the actuator; and the cooling system ensures heat dissipation and stability during long-term operation. The monitoring and control unit includes: a travel limit switch controller mounted above the actuator for adjusting the thrust magnitude; a travel reciprocating counter connected to it for recording the number of actuations; stress sensors (either strain gauge or piezoresistive) evenly distributed on the back of the specimen for real-time monitoring of the specimen stress state; a thrust sensor (either hydraulic or piezoelectric) for real-time monitoring of the thrust value; and a data acquisition unit that synchronously acquires stress and thrust signals, transmits them to a data processing terminal via a signal bridge for calculation, and obtains the actual specimen stress and actuator thrust values. The test judgment unit includes: the data processing terminal compares the calculation results with the benchmark preset value determined in step 1; if the maximum stress value and the thrust value are close to the preset range, the test is judged to meet the requirements; otherwise, the test is judged to fail.

[0010] Step 4: Accelerated fatigue testing and online monitoring. With the support of the cooling system, the loading device can operate continuously for 24 hours. As a further preferred option, in step 4, under the condition of maintaining the preset stress level unchanged, fatigue can be further accelerated by increasing the load frequency; a multi-method collaborative monitoring approach is adopted to track crack behavior in real time: using a high-frequency camera and digital image correlation technology, the initiation and propagation path of cracks on the test specimen surface is continuously monitored; combined with dye penetrant testing agent to develop and assist in the identification of cracks, and vernier calipers are used to accurately measure the crack length on the test specimen surface.

[0011] As a further preferred option, the measurement frequency is dynamically adjusted according to the crack development stage; high-frequency monitoring is implemented in the early stage of crack initiation, and after the crack has stably expanded, the measurement can be performed once every 1000 to 2000 cycles based on the number of actuations recorded by the stroke counter.

[0012] This invention uses the finite element analysis results of the prototype structure as direct input to the physical test model, providing support for the design and loading control of the physical test model and achieving high-fidelity reproduction of the stress state under actual working conditions. The model specimen maintains the same width, height, and material properties as the prototype and is derived from the stress distribution of the real structure. Combined with load sensors to collect stress data in real time, it effectively overcomes the problem of load distortion in traditional simplified models, making the crack initiation and propagation patterns closer to engineering reality. Furthermore, the combination of a cooling system ensuring 24-hour uninterrupted operation and an adjustable load frequency effectively accelerates fatigue testing. This method significantly shortens the test cycle, reduces energy consumption and cost, and provides a feasible path for rapid evaluation of structural fatigue performance. Finally, the comprehensive application of high-frequency visual monitoring and penetrant testing enables the tracking of the entire crack initiation and propagation process. The loading device and method are not only applicable to miter gates but can also be extended to the fatigue performance evaluation of other large welded steel structures subjected to cyclic loads (such as lock valves and large pressure vessels), showing broad engineering application prospects. Attached Figure Description

[0013] Figure 1 This is a stress distribution cloud map for finite element analysis; Figure 2 Here is a schematic diagram of the test specimen, where a is a plan view and b is a cross-sectional view; Figure 3 This is a schematic diagram of the overall structure of the experimental loading device of the present invention; Figure 4 These are stress and thrust monitoring graphs, where a is the stress variation graph and b is the thrust variation graph. Figure 5 This is a diagram showing the overall distribution of stress levels at each measuring point; Figure 6 Diagram showing the location of crack initiation; Figure 7The images show a comparison of crack changes, where a is the initial state image and b is the change image after 60,000 loading cycles. Figure 8 This is a schematic diagram of the test method flow of the present invention; Figure reference numerals: 1. Test model specimen; 2. Test platform base; 3. Slide rail component; 4. Hydraulic cylinder platform; 5. Actuator; 6. Rigid reaction frame; 7. Power source control system; 8. Industrial chiller; 9. Stroke limit switch controller; 10. Stroke reciprocating counter; 11. Strain gauge sensor; 12. Hydraulic sensor; 13. Wireless dynamic acquisition instrument; 14. Data processing terminal. Detailed Implementation

[0014] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0015] The present invention provides a fatigue testing loading device and method for a herringbone gate structure, characterized by comprising the following specific steps: Step 1: Prototype finite element analysis. Based on the geometric and material parameters of the prototype herringbone gate, a three-dimensional finite element simulation model is established to simulate its mechanical response under circulating hydrodynamic load. Stress analysis is performed through the finite element simulation model to determine the stress distribution and extract the location of the maximum bending stress, thereby obtaining the maximum stress value.

[0016] Step 2: Physical test model design. Based on the long-term immersion area at the bottom of the gate (subject to circulating hydrodynamic loads) and the stress distribution determined by finite element analysis at the bottom of the gate, a key section (the rear flange of the gate, the area of ​​maximum bending stress concentration) is selected to fabricate a model specimen. To ensure the realistic response of the structure under long-term loads, the width, height, and material properties of the model specimen are strictly consistent with the prototype.

[0017] Step 3. Design and construction of the loading device, including: The cyclic testing unit includes: an actuator mounted on the test platform base, a rigid reaction frame, a test model specimen, and a slide rail assembly. The actuator is used to apply circulating hydrodynamic loads simulating actual working conditions; the rigid reaction frame provides stable support for the actuator; the test model specimen is manufactured and determined according to step 2, with its tail end fixed to the platform base by high-strength welding, and its front bottom supported on the slide rail, so as to reproduce the actual stress state under reciprocating loading.

[0018] The system power unit includes a power source, a power source control system, and a cooling system connected in sequence. The power source can be any of a hydraulic cylinder, a pneumatic cylinder, or a drive motor. The power source control system is responsible for starting and stopping the actuator, while the cooling system ensures heat dissipation and stability during long-term operation.

[0019] The monitoring and control unit includes: a travel limit switch controller mounted above the actuator for adjusting the thrust magnitude; a travel reciprocating counter connected to it for recording the number of actuations; stress sensors (either strain gauge or piezoresistive) evenly distributed on the back of the specimen to monitor the stress state of the specimen in real time; a thrust sensor (either hydraulic or piezoelectric) to monitor the thrust value in real time; and a data acquisition instrument that synchronously acquires stress and thrust signals, transmits them to a data processing terminal via a signal bridge for calculation, and obtains the actual specimen stress and actuator thrust values.

[0020] The test evaluation unit includes: a data processing terminal that compares the calculated results with the preset benchmark values ​​determined in step 1. If both the stress and thrust values ​​are close to the preset range, the test is deemed to meet the requirements; otherwise, the test is deemed to have failed. Step 4: Accelerated fatigue testing and online monitoring. With the support of the cooling system, the loading device can operate continuously for 24 hours. During the test, under the condition of maintaining a constant preset stress level, accelerated fatigue can be further achieved by increasing the load frequency. A multi-method collaborative monitoring approach is used to track crack behavior in real time: high-frequency cameras and digital image correlation technology are used to continuously monitor the initiation and propagation path of cracks on the test specimen surface; dye penetrant is used to develop and assist in the identification of cracks, and vernier calipers are used to accurately measure the crack length on the specimen surface. The measurement frequency is dynamically adjusted according to the crack development stage: high-frequency monitoring is implemented in the early stage of crack initiation. After the crack has stably propagated, measurements can be taken every 1000 to 2000 cycles based on the number of strokes recorded by the stroke counter. Example

[0021] This embodiment provides a fatigue test loading device and method for a miter gate structure, taking the downstream right miter gate of the Gezhouba Dam No. 1 gate as an example to specifically illustrate the implementation of the present invention.

[0022] Based on the actual geometric dimensions and material properties (16Mn steel) of the miter gate, a three-dimensional simulation model was established using finite element analysis software. This model simulates the circulating hydrodynamic loads during normal operation. Figure 1 The stress distribution cloud map is provided for finite element analysis. The analysis results show that the structural stress distribution near the bottom gate shaft column is mainly around 100~150MPa, with the rear flange of the gate being the area of ​​maximum bending stress concentration, where the calculated maximum equivalent stress value is approximately 150MPa. Based on this stress result, the equivalent concentrated thrust to be applied to the specimen by the actuator in the physical test model is calculated to be approximately 1350kN. This stress value of 150MPa and the thrust value of 1350kN will serve as the baseline preset values ​​for subsequent physical model tests.

[0023] Based on the stress distribution determined by finite element analysis, a physical experimental model was constructed. Figure 2 This is a schematic diagram of the test specimen. To ensure the authenticity of the mechanical response, the specimen uses the same steel material as the prototype, and its width and height are consistent with the corresponding positions on the prototype, measuring 0.84 × 0.42 m. To minimize the scaling effect of the model and facilitate welding and fabrication, other dimensions are determined based on the principle of similarity and a scaling ratio of 1:3. The specimen length is 2.16 m, and the steel plate thickness is 8 mm. During the specimen fabrication process, it is ensured that the weld quality matches the prototype's process.

[0024] Figure 3 A schematic diagram of the overall structure of the fatigue testing loading device provided by the present invention includes: The prepared test model specimen 1 is installed on the test platform base 2. The tail end of the specimen is fixed to the platform base by high-strength welding, and the front bottom is supported on the slide rail component 3. In this embodiment, a hydraulic cylinder platform 4 provides a power source for the actuator 5, and a rigid reaction frame 6 provides stable support for the actuator. The power source control system 7 is responsible for the start and stop operation of the actuator. To ensure the stability of the device during long-term continuous operation, an industrial chiller 8 is configured, and its inlet and outlet water pipes are connected to the cooling circuit of the hydraulic cylinder platform to circulate and cool the hydraulic oil. The stroke limit switch controller 9 is installed above the actuator cylinder to set and control the stroke of the piston rod and adjust the thrust. The stroke reciprocating counter 10 is connected to the stroke limit switch controller to automatically record the number of complete cycles of the actuator. Strain gauge sensors 11 are evenly pasted on the back of the model specimen to monitor the stress on the specimen in real time. Hydraulic pressure sensors 12 are installed in the hydraulic circuit of the actuator to monitor and provide feedback on the output thrust of the actuator in real time. All sensor signals are recorded in real time by the wireless dynamic acquisition instrument 13 and transmitted to the data processing terminal 14. The received signals are calculated, displayed and stored by the DHDAS dynamic signal acquisition and analysis system software on the terminal, and the precise values ​​of specimen stress (monitored by the variable sensor 11) and actuator thrust (monitored by the hydraulic sensor 12) are obtained in real time.

[0025] When the loading device starts running, the readings of the strain sensor and hydraulic pressure sensor are observed through the data processing terminal. Control parameters are fine-tuned to ensure that the stress value of the specimen matches the preset finite element value, and that the peak thrust output of the actuator remains stable within the target range. During the verification phase, if the measured stress and thrust values ​​are close to the preset range, the test is deemed to meet the requirements and the debugging is deemed qualified; otherwise, it is deemed unqualified and requires re-debugging. The stress sensor and thrust sensor data calculated in real-time by the data processing terminal indicate (…). Figure 4 The test loading system was very stable, and the stress changes at each measuring point of the model specimen were also very stable. The overall distribution of stress levels at each measuring point is shown in the figure. Figure 5 The maximum stress value was about 150 MPa, and the peak thrust was stable at about 1350 kN, which met the expected values ​​of the test.

[0026] A high-frequency camera combined with digital image correlation technology was used to monitor the crack initiation and propagation on the test specimen surface throughout the entire process. High-frequency monitoring was implemented in the early stage of crack initiation. After the crack stabilized and propagated, measurements were taken every 2000 cycles based on the number of strokes recorded by the stroke counter. During measurement, the machine was stopped and the specimen surface was developed using a dye penetrant tester. The crack length was measured using vernier calipers. In this embodiment, the fatigue test underwent more than 60,000 loading cycles over more than ten days. Considering the 3,000 to 4,000 annual lock cycles of the early No. 1 lock, the cyclic load is equivalent to nearly 20 years of lock cycles.

[0027] Figure 6 The diagram shows the locations of crack initiation. It can be seen that cracks appeared at seven locations in the beam grid: intervals 1-2, 1-5, 1-7, 1-9, 2-5, 2-6, and 2-8, mainly located in areas of relatively high stress. Taking the crack change at location 2-6 under the initial state and after 60,000 loading cycles as an example, [further details are provided]. Figure 7 As shown in the figure, the crack propagation is obvious.

[0028] Table 1 shows the average crack propagation rate. Under a stress level of 150 MPa, the crack propagation rate of the fatigue test in this embodiment was calculated and analyzed, and extrapolated to the prototype at a scale of 1:3. The maximum average crack propagation rate of the prototype herringbone gate is approximately 9.24 mm / 10,000 cycles.

[0029]

[0030] The results verify that the method described in this invention can highly reproduce the actual complex stress state and effectively accelerate the fatigue test process of the herringbone gate, providing a scientific basis and technical support for the safety assessment of its fatigue performance and the formulation of preventive maintenance strategies.

[0031] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A fatigue testing loading device for a herringbone gate structure, characterized in that, include: The test platform base (2), the test model specimen (1) and the loading device are located on the test platform base (2). The test model specimen (1) is fixed on the test platform base (2). The loading device applies force to the test model specimen (1) through the slide rail component (3) to simulate the stress environment of the miter gate. The loading device includes a rigid reaction frame (6) and an actuator (5). The rigid reaction frame (6) is fixed on the test platform base (2), and the actuator (5) is located on the side of the rigid reaction frame (6) facing the test model specimen (1). The hydraulic cylinder platform (4) is connected to the actuator (5) via a pipe and is used to provide a power source for the force applied by the actuator (5); The power source control system (7) is used to control the hydraulic cylinder platform (4). An industrial chiller (8) is used to connect the inlet and outlet water pipes to the cooling circuit of the hydraulic cylinder platform (4) for circulating cooling of hydraulic oil in the hydraulic cylinder platform (4). The travel limit switch controller (9) is installed above the cylinder of the actuator (5) and is used to set and control the piston rod stroke of the actuator (5) and adjust the piston rod thrust. The travel reciprocating counter (10) is connected to the travel limit switch controller (9) and is used to automatically record the number of complete reciprocating pushes of the actuator (5).

2. The fatigue test loading device for a herringbone gate structure according to claim 1, characterized in that, The loading device also includes: A strain gauge sensor (11) is uniformly pasted on the back of the test specimen (1) to monitor the stress on the specimen in real time. A hydraulic sensor (12) is installed in the oil circuit of the actuator (5) to monitor and provide feedback on the output thrust of the actuator (5) in real time.

3. The fatigue test loading device for a herringbone gate structure according to claim 2, characterized in that, The loading device also includes a wireless dynamic acquisition instrument (13) and a data processing terminal (14). The signals of the strain sensor (11) and the hydraulic sensor (12) are recorded in real time by the wireless dynamic acquisition instrument (13) and transmitted to the data processing terminal (14). The received signals are calculated, displayed and stored by the DHDAS dynamic signal acquisition and analysis system software on the data processing terminal (14), and the accurate values ​​of the stress of the specimen and the thrust of the actuator are obtained in real time.

4. A fatigue testing method for a herringbone gate structure, characterized in that, Includes the following steps: Step 1: Prototype finite element analysis. Based on the geometric and material parameters of the original herringbone gate, a three-dimensional finite element simulation model is established to simulate its mechanical response under circulating hydrodynamic load. Stress analysis is performed through the finite element simulation model to determine the stress distribution of the herringbone gate and extract the location of the maximum bending stress to obtain the maximum stress value. Step 2: Physical test model design. Based on the area at the bottom of the gate body that is subjected to water force for a long time, and the stress distribution determined by the finite element analysis at the bottom of the gate body, key parts are cut to make model specimens. In order to ensure the actual response of the structure under long-term load, the width, height and material properties of the model specimens are strictly consistent with the prototype. Step 3. Design and construction of the loading device, including: The cyclic testing unit includes: an actuator, a rigid reaction frame, a test model specimen, and a slide rail assembly mounted on a test platform base; the actuator is used to apply circulating hydrodynamic loads simulating actual working conditions; the rigid reaction frame provides stable support for the actuator; the test model specimen is manufactured and determined according to step 2, with its tail end fixed to the platform base by high-strength welding, and its front bottom supported on the slide rail, so as to reproduce the actual stress state under reciprocating loading; The system power unit includes: a power source, a power source control system, and a cooling system connected in sequence; the power source control system is responsible for the start and stop operation of the actuator, while the cooling system ensures heat dissipation and stability during long-term operation; The monitoring and control unit includes: a travel limit switch controller mounted on top of the actuator to regulate the thrust magnitude; a travel reciprocating counter connected to it to record the number of actuations; stress sensors evenly distributed on the back of the specimen to monitor the stress state of the specimen in real time; a thrust sensor to monitor the thrust value in real time; and a data acquisition instrument to synchronously acquire stress and thrust signals, which are transmitted to the data processing terminal via a signal bridge for calculation to obtain the actual specimen stress and actuator thrust values. The test judgment unit includes: the data processing terminal compares the calculation results with the benchmark preset values ​​determined in step 1; if the maximum stress value and the thrust value are both close to the preset range, the test is judged to meet the requirements; otherwise, the test is judged to fail. Step 4: Accelerated fatigue testing and online monitoring. With the support of the cooling system, the loading device can operate continuously for 24 hours.

5. The fatigue test method for a herringbone gate structure according to claim 4, characterized in that, During the experiment: In step 4, under the condition of maintaining the preset stress level unchanged, fatigue can be further accelerated by increasing the load frequency; a multi-method collaborative monitoring method is used to track crack behavior in real time: using a high-frequency camera and digital image correlation technology, the initiation and propagation path of cracks on the test piece surface is continuously monitored; combined with dye penetrant testing agent to develop and assist in the identification of cracks, and vernier calipers are used to accurately measure the crack length on the test piece surface.

6. The fatigue test method for a herringbone gate structure according to claim 5, characterized in that, During the experiment: the measurement frequency was dynamically adjusted according to the crack development stage; high-frequency monitoring was implemented in the early stage of crack initiation, and after the crack stabilized and expanded, the measurement was performed once every 1000 to 2000 cycles based on the number of actuations recorded by the stroke counter.

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