Bolt fatigue testing device and method with additional bending moment and clamping interference coupling

Abstract

The present application relates to the technical field of bolt fatigue testing, and provides a bolt fatigue testing device and method that couples additional bending moment with clamping interference, including driving the movement of a symmetrical fixture by actuators at both ends of a support frame, wherein the countersunk hole of the fixture body cooperates with the inclined pressure surface of the wedge-shaped slider to form a preset angle to simulate the additional bending moment generated by the bolt assembly angle; the interference slider applies dynamic interference through the interference hole with adjustable eccentricity to reproduce the interference effect of the clamped parts. The pad serves as an intermediate carrier to ensure bidirectional load transfer, and the circumferentially distributed load sensors collect bolt force data in real time. During the test, the controller drives the actuator to alternately load according to the gradient cycle strategy, and the data processing terminal fuses the load data with the angle of the inclined pressure surface to calculate the preload and bending moment, and realizes the simulation of real working conditions through dynamic coupling control. Ultimately, the defects of ignoring additional bending moment, interference effect and dynamic load control in traditional testing are solved, and the fatigue performance of bolts under composite stress is accurately evaluated.

Description

Technical Field

[0001] The present application relates to the technical field of bolt fatigue testing, and in particular to a bolt fatigue testing device and method with additional bending moment and clamping interference coupling. Background Art

[0002] The contents of this section merely provide background information related to this application and may not constitute prior art.

[0003] With the rapid development of the new materials industry, the field of mechanical engineering is placing higher demands on the reliability of bolted joints. Fatigue resistance has become a key metric in new materials-related services, posing a challenge to traditional fatigue testing techniques. In particular, in the design and analysis of bolted joints, traditional testing equipment often struggles to accurately simulate the complex loads found in actual operating conditions. The new materials industry's increasingly stringent requirements for testing accuracy have made the development of more advanced fatigue assessment methods even more urgent.

[0004] In the prior art, for example, publication number CN102507319A discloses a bolt fatigue testing device comprising an upper fixture, an upper spherical cap clamp, an upper fixture base, a test bolt, a lower fixture base, a lower spherical cap clamp, and a lower fixture. This bolt fatigue testing device is used for axial fatigue testing of bolts. By providing a centering device and a bolt fixing device, it effectively prevents the effects of additional bending moment, bolt loosening, and additional torsional stress during the axial fatigue test, which can lead to abnormal bolt fracture and affect the test results.

[0005] However, these devices, along with other existing technologies, suffer from three key technical deficiencies. Regarding load simulation, their single axial load loading mode fails to replicate the additional bending moment effects (which can account for 30%-50% of the axial stress) generated by eccentric assembly, flange deflection, or vibration inertia forces in actual working conditions, resulting in systematic deviations between the test stress spectrum and the actual stress state. Regarding interference effects, the rigid fixture fixation method fails to account for local deformation and dynamic redistribution of contact pressure in the connected components, and lacks the ability to simulate stress redistribution and dynamic friction and wear caused by sheet warping. This results in deviations of more than 25% between the test data and the actual failure mode. Regarding the dynamic coupling mechanism, the static load ratio (R=0.1) and constant preload loading method adopted by the current ISO standard are significantly inadequate. They fail to account for the synergistic effects of preload relaxation and dynamic bending. The preload dispersion (±15%) caused by hydraulic or torque wrench loading significantly affects test accuracy. Furthermore, the inability to simulate the additional bending moment introduced by installation deviations (such as flange unevenness) ultimately leads to fatigue life prediction errors exceeding 50%.

[0006] The essence of these technical limitations lies in the lack of multi-physics field coupling simulation capabilities in existing devices. Specifically, the test system separates the axial force, bending moment, and interference effects of the clamped parts. This makes it difficult to reproduce typical failure characteristics such as the tail folding cracks of aircraft engine bolts in a vibration environment, and it cannot accurately reflect the real-time interaction between preload attenuation and dynamic external loads. More seriously, the design of the rigid fixture combined with the open-loop control system completely ignores the interference effect of the connected parts on the bolts. This distortion of the working condition seriously restricts the application value of the test device in the evaluation of high-reliability bolted connections in wind power, aerospace, and other fields. Summary of the Invention

[0007] In order to solve the above technical problems, the purpose of this application is to provide a bolt fatigue testing device and method that couples additional bending moment with clamping interference. By simulating the dual effects of initial pre-tightening additional bending moment and dynamic interference of clamped parts, the actual service conditions of the bolt are reproduced, and real-time coupling control of preload-external load is realized. It aims to solve the problem of test result deviation caused by ignoring additional bending moment, interference effect of clamped parts and insufficient dynamic load control in traditional bolt fatigue tests.

[0008] The purpose of this application is achieved through the following technical solutions:

[0009] In a first aspect, the present invention provides a bolt fatigue testing device with additional bending moment and clamping interference coupling, comprising:

[0010] A support frame, with actuators provided on both ends of the support frame;

[0011] Two clamps, each clamp is connected to an actuator, and each clamp includes a clamp head and a main body, one end of the clamp head is connected to the actuator, and the other end of the clamp head is connected to the main body, and the end of the main body away from the clamp head is provided with a countersunk hole for the bolt to be tested to pass through, and a slide groove is provided on both sides of the countersunk hole;

[0012] A wedge-shaped slider has a central hole in the middle for the bolt to be tested to pass through, and first sliders are provided on both sides of the wedge-shaped slider, and the first sliders are transitionally matched with the corresponding slide grooves; the side of the wedge-shaped slider close to the actuator is a diagonal pressure surface, and a preset angle is formed between the diagonal pressure surface and the horizontal plane. The preset angle is used to simulate the actual bolt assembly deflection angle, and the side of the wedge-shaped slider away from the actuator abuts against the bottom surface of the countersunk hole;

[0013] An interference slider is provided with an interference hole in the middle for the bolt to be tested to pass through. The interference amount of the interference hole on the bolt to be tested is controlled by adjusting the eccentricity of the interference hole. Second sliders are provided on both sides of the interference slider, and the second sliders are transitionally matched with the corresponding slide grooves.

[0014] The backing plate is arranged between the two fixtures; the backing plate is provided with a through hole for the bolt to be tested to pass through; the two fixtures are respectively arranged on both sides of the backing plate;

[0015] Load sensors, with multiple load sensors evenly distributed circumferentially around the bolt to be measured. After the actuator pulls two fixtures, pressure is applied to the bolt to be measured, and the load sensors acquire the real-time load data of the bolt to be measured.

[0016] Further, the support frame includes a base, a connecting member, and multiple support members provided on the base. Each support member is parallel to each other, and the base is connected to the connecting member through multiple support members. Actuators are respectively provided on the base and the connecting member.

[0017] Further, it further includes a fixing bolt. The connecting member is slidably connected to each support member, and threaded holes are provided at both ends of the connecting member. The fixing bolt passes through the threaded hole and abuts against the connecting member.

[0018] Further, the main body is in a "hui" character shape.

[0019] Further, the number of load sensors is four, and the four load sensors are evenly distributed circumferentially around the side wall of the bolt to be measured.

[0020] Further, it further includes: a load collector, a data processing terminal, a controller, and a power source that are electrically connected in sequence; the input end of the load collector is connected to the load sensor, and the power source is connected to the actuator; the load collector transmits the load data of the load sensor to the data processing terminal; the data processing terminal processes the load data and sends a feedback signal to the controller, and the controller controls the power source to drive the actuator to move.

[0021] Further, the power source includes one of a hydraulic cylinder, a pneumatic cylinder, or a driving motor.

[0022] In a second aspect, the present invention provides a bolt fatigue test method for coupling additional bending moment and clamping interference, which is applied to a bolt fatigue test device for coupling additional bending moment and clamping interference as in the first aspect. The method includes:

[0023] Select a preset included angle and eccentricity that meet the test requirements, and start the bolt fatigue test device;

[0024] In response to the start signal, the controller controls the power source to drive the actuator to work according to a preset strategy; the preset strategy sets the maximum value of the test based on the maximum load of the bolt to be measured, and alternately cycles and loads between the maximum value and the minimum value according to a preset gradient; the cycling mode includes: the first mode starts from the minimum value, increases to the maximum value through gradient increase, and then decreases back to the minimum value through gradient decrease; or the second mode starts from the maximum value, decreases to the minimum value through gradient decrease, and then increases back to the maximum value through gradient increase;

[0025] After the actuator starts working, the load acquisition instrument transmits the load data of the load sensor to the data processing terminal; the data processing terminal substitutes the load data and the preset angle into the preset formula to calculate the preload force and bending moment data;

[0026] Within the preset number of cycles, if the calculated preload force and bending moment are lower than the preset proportion of the initial value, the test is judged to have met the requirements; otherwise, the test is judged to have failed to meet the requirements.

[0027] Furthermore, the preset formula includes:

[0028] ,

[0029] ,

[0030] in, is the preload force, is the transverse cross-sectional area of ​​the bolt, is the elastic modulus of the bolt, 、 、 and The strain data obtained by the four load sensors are: is the bending moment, is the thickness of the clamped part, The preset angle.

[0031] In a third aspect, the present invention provides a bolt fatigue testing system with additional bending moment and clamping interference coupling, which is applied to a bolt fatigue testing device with additional bending moment and clamping interference coupling as in the first aspect, and the system comprises:

[0032] A start module is used to select a preset angle and eccentricity that meet the test requirements and start the bolt fatigue test device;

[0033] The cyclic test module is configured to control the power source to drive the actuator to operate according to a preset strategy after the controller receives a start signal. The preset strategy sets a maximum test value based on the maximum load of the bolt to be tested, and alternately cycles the load between the maximum and minimum values ​​according to a preset gradient. The cyclic modes include: a first mode starting with the minimum value, gradually increasing to the maximum value, and then decreasing back to the minimum value; or a second mode starting with the maximum value, gradually decreasing to the minimum value, and then increasing back to the maximum value.

[0034] The calculation module is used for, after the actuator is working, the load acquisition instrument transmits the load data of the load sensor to the data processing terminal; the data processing terminal substitutes the load data and the preset angle into the preset formula to calculate the preload force and bending moment data;

[0035] The test judgment module is used to determine that the test meets the requirements if the calculated preload force and bending moment are lower than the preset ratio of the initial value within the preset number of cycles; otherwise, it is determined that the test fails to meet the requirements.

[0036] In summary, the technical solutions of the embodiments of the present application have at least the following advantages and beneficial effects:

[0037] The present invention drives the movement of the clamp by actuators at both ends of the support frame. The clamp body cooperates with the wedge-shaped slider and the interference slider through the countersunk hole and the slide groove structure to form a composite clamping system. The inclined pressure surface of the wedge-shaped slider simulates the assembly deflection angle at a preset angle to generate additional bending moment, and the eccentric interference hole of the interference slider adjusts the amount of bolt interference; the pad serves as an intermediate carrier to ensure that the clamps on both sides apply pressure synchronously, and the circumferentially distributed load sensors collect the bolt force data in real time. During the test, the actuator applies dynamic load according to the preset gradient cyclic loading strategy. The data processing terminal calculates the preload and bending moment values ​​based on the inclined pressure surface angle and the sensor data, and determines the fatigue life of the bolt by the degree of mechanical performance attenuation within the number of cycles. Its core principle is to integrate geometric deflection simulation, dynamic interference adjustment and multi-dimensional load feedback to achieve coupled simulation of preload and external load under service conditions, effectively making up for the defects of neglecting bending moment, lacking interference effect and insufficient dynamic control in traditional tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic structural diagram of a bolt fatigue testing device with additional bending moment and clamping interference coupling provided by the present invention;

[0039] Figure 2 This is a schematic diagram of the connection of the device for bolt load data processing and bolt load control in the present invention;

[0040] Figure 3 Schematic diagram of the interference between the initial pre-tightening additional bending moment and the clamped part in the present invention;

[0041] Figure 4 for Figure 3 sectional view of

[0042] Figure 5 This is a schematic diagram of the structure of the present invention when the clamp is located at the top;

[0043] Figure 6 This is a schematic diagram of the structure of the present invention when the clamp is located at the bottom;

[0044] Figure 7 Schematic diagram of the structure of the wedge-shaped slider in the present invention;

[0045] Figure 7a Schematic diagram of a wedge-shaped slider in the present invention with a predetermined angle between the oblique pressure surface and the horizontal plane;

[0046] Figure 8 Schematic diagram of the structure of the interference slider in the present invention;

[0047] Figure 8a Schematic diagram of the eccentricity of the interference hole of the interference slider in the present invention;

[0048] Figure 9 A flowchart of a bolt fatigue test method coupled with additional bending moment and clamping interference provided by the present invention;

[0049] Figure 10 This is a schematic diagram of a bolt fatigue test system with additional bending moment and clamping interference coupling provided by the present invention.

[0050] Icons: 1. Bolt to be tested; 2. Load sensor; 3. Fixture; 4. Countersunk hole; 5. Slide; 6. Support frame; 7. Chuck; 8. Connector; 9. Base; 10. Support; 11. Fixing bolt; 12. Wedge-shaped slider; 13. Center hole; 14. First slider; 15. Inclined pressure surface; 16. Interference slider; 17. Interference hole; 18. Second slider; 19. Bending surface; 20. Pad; 21. Actuator; 22. Test machine platform; 23. Load acquisition instrument; 24. Data processing terminal; 25. Controller. DETAILED DESCRIPTION

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0052] Example 1:

[0053] like Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 As shown, an embodiment of the present application proposes a bolt fatigue testing device with additional bending moment and clamping interference coupling, comprising:

[0054] The support frame 6, which serves as the basic structure of the entire test device, is set on the test machine body 22 and firmly supports the two actuators 21. The multiple actuators 21 are respectively installed at both ends of the support frame 6 (i.e. Figure 1 The upper and lower ends of the clamp are responsible for providing power to drive the clamp 3 to perform tension or compression operations to simulate the force changes of the bolt under different working conditions. This structural design ensures the stability and safety of the test process.

[0055] Two clamps 3, such as Figure 5 and6 As shown, each clamp 3 is connected to an actuator 21, and each clamp 3 includes a chuck 7 and a main body, one end of the chuck 7 is connected to the actuator 21, and the other end of the chuck 7 is connected to the main body to form a whole; the end of the main body away from the chuck 7 is provided with a countersunk hole 4 for the bolt 1 to be tested to pass through, and a slide groove 5 is provided on both sides of the countersunk hole 4 to facilitate the installation and sliding of the wedge slider 12 or the interference slider 16; wherein, the main body is designed in the shape of a "U" character; the countersunk hole 4 is located at the center of the side of the "U"-shaped main body away from the actuator 21, ensuring that the force acting on the bolt 1 to be tested is located at the center of the main body, thereby reducing the eccentricity error. Specifically, the "U"-shaped main body design makes the bolt 1 to be tested more uniform when subjected to force, reducing the stress concentration problem caused by improper structural design. The design of the slide groove 5 facilitates the flexible adjustment of the wedge slider 12 and the interference slider 16 to adapt to bolts of different specifications and test requirements. This structural design improves the accuracy and flexibility of the test.

[0056] It should be noted that the two clamps 3 have the same structure and their sizes can be adjusted as needed.

[0057] Wedge-shaped slider 12, such as Figure 7 and Figure 7a As shown, a central hole 13 for the bolt 1 to be tested to pass through is provided in the middle of the wedge-shaped slider 12, and first sliders 14 are provided on both sides of the wedge-shaped slider 12, and the first sliders 14 are transitionally matched with the corresponding slide grooves 5; the side of the wedge-shaped slider 12 close to the actuator 21 is a ramp pressure surface 15, and a preset angle is formed between the ramp pressure surface 15 and the horizontal plane. The preset angle is used to simulate the actual bolt assembly deflection angle, and the side of the wedge-shaped slider 12 away from the actuator 21 abuts against the bottom surface of the countersunk hole 4, and an additional bending moment is generated by the extrusion action of the ramp pressure surface 15.

[0058] The wedge-shaped slider 12 simulates the additional bending moment caused by eccentricity during actual bolt assembly. By adjusting the angle between the oblique pressure surface 15 and the horizontal plane, the magnitude of the additional bending moment can be precisely controlled, thereby simulating the complex stress conditions of the bolt. This simulation method improves the authenticity and accuracy of the test and facilitates more accurate assessment of the fatigue performance of the bolt.

[0059] Interference slider 16, such as Figure 8 and Figure 8a As shown, an interference hole 17 is provided in the middle of the interference slider 16 for the bolt 1 to be tested to pass through, and the nut of the bolt 1 to be tested is in contact with the bending surface 19 of the interference slider 16; the interference amount of the interference hole 17 on the bolt 1 to be tested is controlled by adjusting the eccentricity of the interference hole 17; second sliders 18 are provided on both sides of the interference slider 16, and the second sliders 18 are transitionally matched with the corresponding slide grooves 5 to ensure that the interference slider 16 can be stably fixed, while also ensuring that it can slide and adjust.

[0060] The design of the interference slider 16 simulates the interference effect of the clamped component on the bolt. In actual assembly, factors such as surface unevenness, material deformation, and assembly errors can interfere with the bolt, affecting the bolt's stress state. By adjusting the eccentricity of the interference hole 17, the magnitude of this interference effect can be quantified, thereby more realistically simulating the bolt's stress conditions in actual assembly, thereby improving the accuracy and reliability of the test.

[0061] The backing plate 20 is placed between the two clamps 3. The backing plate 20 is provided with a through hole for the bolt 1 to be tested to pass through. The two clamps 3 are respectively placed on both sides of the backing plate 20. The presence of the backing plate 20 is intended to compensate for the thickness difference of the actual clamped parts, ensuring the consistency and accuracy of the test.

[0062] Load sensors 2, multiple load sensors 2, are evenly distributed circumferentially around the bolt 1 under test. When the actuator 21 pulls the two clamps 3, pressure is applied to the bolt 1 under test. The load sensors 2 acquire real-time load data on the bolt 1 under test. Four load sensors 2 are evenly distributed circumferentially around the sidewall of the bolt 1 under test. This distribution of load sensors 2 enables comprehensive and accurate monitoring of load changes on the bolt 1 under test during stress loading, providing reliable data support for fatigue life prediction. Real-time monitoring and feedback of load data also enables precise control of the test process, further improving test accuracy and reliability.

[0063] Furthermore, the support frame 6 includes a base 9, a connecting member 8 and a plurality of supporting members 10 arranged on the base 9. Each supporting member 10 is parallel to each other. The base 9 is connected to the connecting member 8 through the plurality of supporting members 10. Actuators 21 are respectively provided on the base 9 and the connecting member 8.

[0064] Specifically, the base 9 serves as a basic load-bearing platform, which is fixed on the test machine table 22, and the overall stability is ensured by multi-point fixing. The connecting member 8 serves as the upper load-bearing structure, forming a rigid connection frame with the base 9 to ensure the centering accuracy of the two actuators 21; multiple parallel supports 10 form a uniform force network between the base 9 and the connecting member 8. This parallel arrangement can effectively disperse dynamic loads, avoid stress concentration, and enable the load generated by the actuator 21 to be transmitted to the fixture 3 system without distortion.

[0065] Furthermore, it also includes a fixing bolt 11, the connecting member 8 is slidably connected to each support member 10, and threaded holes are provided on both ends of the connecting member 8. The fixing bolt 11 passes through the threaded holes and abuts against the connecting member 8.

[0066] Specifically, the connector 8 and each support member 10 are slidably connected via precision slide rails, allowing the connector 8 to freely move along the axial direction of the support member 10. Internally threaded holes are symmetrically machined at both ends of the connector 8. After the fixing bolts 11 are screwed into these threaded holes, their ends form mechanical contact with the outer surfaces of the support members 10. When the fixing bolts 11 are tightened, a normal compressive force is generated between the bolt ends and the support members 10, rigidly locking the connector 8 in a preset position on the support members 10 through the combined action of static friction and mechanical constraints. When the fixing bolts 11 are loosened, the bolt ends break away from rigid contact with the support members 10, releasing the sliding constraint between the connector 8 and the support members 10 and allowing the connector 8 to be infinitely adjusted along the axis of the support members 10.

[0067] The system further includes: a load acquisition device 23, a data processing terminal 24, a controller 25, and a power source, which are electrically connected in sequence. The input end of the load acquisition device 23 is connected to the load sensor 2, and the power source is connected to the actuator 21. The load acquisition device 23 transmits the load data from the load sensor 2 to the data processing terminal 24. The data processing terminal 24 processes the load data and sends a feedback signal to the controller 25. The controller 25 controls the power source to drive the actuator 21 to move. The controller 25 is disposed within the base 9.

[0068] Specifically, the input end of the load acquisition instrument 23 is connected to the load sensor 2, and is used to collect and transmit the load data of the load sensor 2 to the data processing terminal 24 in real time; its working principle is to convert the analog signal output by the load sensor 2 into a digital signal, and perform preliminary filtering processing to eliminate external noise interference, thereby ensuring the accuracy and integrity of the load data.

[0069] After receiving the load data from the load acquisition instrument 23, the data processing terminal 24 performs processing including signal analysis, data filtering or comparison operations with preset test parameters, and then sends the generated feedback signal to the controller 25; its working principle relies on the built-in algorithm to evaluate the bolt stress state in real time and generate control instructions to achieve dynamic adjustment and adaptive control of the test load, avoiding the lag of manual intervention and improving the accuracy and efficiency of the test.

[0070] Based on the feedback signal sent by the data processing terminal 24, the controller 25 outputs control instructions to drive the power source to work, and then drives the actuator 21 to move; its working principle is to use preset control logic to adjust the output parameters of the power source to ensure that the action of the actuator 21 accurately matches the test requirements, reducing the test error caused by manual control deviation, thereby improving the reliability and repeatability of simulating complex stress conditions of the bolt.

[0071] The power source is directly connected to the actuator 21 and can be selected from one of a hydraulic cylinder, a pneumatic cylinder or a drive motor. For example, a hydraulic cylinder can output linear thrust through fluid pressure, a pneumatic cylinder uses compressed gas to drive reciprocating motion, or a drive motor converts rotational torque into linear displacement; its working principle is to provide adjustable power output according to the instructions of the controller 25 to simulate the tensile or compressive load of the bolt under different working conditions, thereby enhancing the versatility and flexibility of the device and being able to adapt to a variety of bolt specifications and test conditions.

[0072] Example 2:

[0073] Based on the same inventive concept, Figure 9 As shown, the present invention provides a bolt fatigue test method with additional bending moment and clamping interference coupling, which is applied to a bolt fatigue test device with additional bending moment and clamping interference coupling in embodiment 1. The method includes:

[0074] S101, select a preset angle and eccentricity that meet the test requirements, and start the bolt fatigue test device.

[0075] Specifically, a preset angle between the oblique pressure surface 15 of the wedge-shaped slider 12 and the horizontal plane is selected. This angle, when driven by the actuator 21, utilizes the principle of inclined plane mechanics to generate an additional bending moment perpendicular to the bolt axis, thereby quantitatively replicating the effects of assembly eccentricity in real-world bolts. Simultaneously, the eccentricity of the center of the interference hole 17 of the interference slider 16 relative to the bolt axis is adjusted, enabling the eccentric structure to generate controllable radial compression when the bolt passes through, directly quantifying and simulating the clamping interference stress caused by surface irregularities or assembly deformation of the clamped component. Once this angle is selected, the bolt fatigue test apparatus is activated and begins operation.

[0076] S102, in response to the start signal, the controller 25 controls the power source to drive the actuator 21 to work according to a preset strategy; the preset strategy sets the maximum value of the test based on the maximum load of the bolt 1 to be tested, and alternately cycles the load between the maximum value and the minimum value according to a preset gradient; the cycle mode includes: the first mode starts with the minimum value, and the gradient increases to the maximum value and then decreases back to the minimum value; or the second mode starts with the maximum value, and the gradient decreases to the minimum value and then increases back to the maximum value.

[0077] Specifically, controller 25 outputs a pulse-width modulated signal or current command to the power source, which is then converted into linear thrust or reciprocating displacement, driving actuators 21 at both ends to perform synchronous pulling or compressive actions. Actuators 21 drive the main body of clamp 3 through a rigid connection, causing the oblique pressure surface 15 of wedge-shaped slider 12 to generate an oblique compressive action with the bottom surface of countersunk hole 4. This oblique mechanical decomposition effect generates a quantitative additional bending moment on the axis of the bolt 1 to be tested. Simultaneously, interference slider 16 applies radial compression through the eccentric hole, precisely quantifying the clamping interference stress coupling effect.

[0078] In addition, the preset strategy is to set the maximum load value based on the ultimate bearing parameters of the bolt 1 to be tested, and simulate the actual service load spectrum through the gradient cyclic loading mechanism. The specific operation includes two cycle modes: the first mode starts from the minimum value, increases step by step to the preset maximum value, and then decreases the gradient back to the minimum value; the second mode performs the maximum-minimum-maximum cycle in reverse. This gradient cycle uses the material hysteresis effect and damage accumulation principle to make the bolt withstand the full spectrum stress amplitude changes within the preset period. Compared with the traditional single amplitude loading, it can better expose the multi-axis fatigue failure characteristics. The gradient change process is achieved by the controller 25 to adjust the power source output pressure or speed in real time, avoiding the instantaneous impact caused by the step load, ensuring that the coupling force of the interference slider 16 and the wedge slider 12 is smoothly transmitted to the bolt 1 to be tested, and improving the mapping accuracy between the test condition and the real assembly environment.

[0079] S103, after the actuator 21 starts working, the load acquisition device 23 transmits the load data of the load sensor 2 to the data processing terminal 24; the data processing terminal 24 substitutes the load data and the preset angle into the preset formula to calculate the preload force and bending moment data.

[0080] The preset formula is:

[0081] (1)

[0082] (2)

[0083] in, is the preload force, is the transverse cross-sectional area of ​​the bolt, is the elastic modulus of the bolt, 、 、 and The strain data obtained by the four load sensors are: is the bending moment, is the thickness of the clamped part, The preset angle.

[0084] S104: Within a preset number of cycles, if the calculated preload force and bending moment are lower than a preset ratio of the initial values, it is determined that the test meets the requirements; otherwise, it is determined that the test fails to meet the requirements.

[0085] Based on the same inventive concept, Figure 10 As shown, the present invention provides a bolt fatigue test system with additional bending moment and clamping interference coupling, which is applied to a bolt fatigue test device with additional bending moment and clamping interference coupling in embodiment 1. The system includes:

[0086] A starting module 201 is used to select a preset angle and eccentricity that meet the test requirements and start the bolt fatigue test device;

[0087] The cyclic test module 202 is configured to control the power source to drive the actuator 21 to operate according to a preset strategy after the controller 25 receives a start signal. The preset strategy sets a maximum value for the test based on the maximum load of the bolt 1 to be tested, and alternately cycles the load between the maximum value and the minimum value according to a preset gradient. The cyclic modes include: a first mode starting with the minimum value, increasing the gradient to the maximum value, and then decreasing the gradient back to the minimum value; or a second mode starting with the maximum value, decreasing the gradient to the minimum value, and then increasing the gradient back to the maximum value.

[0088] The calculation module 203 is used to transmit the load data of the load sensor 2 to the data processing terminal 24 after the actuator 21 is working. The data processing terminal 24 substitutes the load data and the preset angle into the preset formula to calculate the preload force and bending moment data.

[0089] The test judgment module 204 is used to determine that the test meets the requirements if the calculated preload force and bending moment are lower than the preset ratio of the initial value within the preset number of cycles; otherwise, it is determined that the test fails to meet the requirements.

[0090] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A bolt fatigue test device with additional bending moment and clamping interference coupling, characterized in that: Comprising: A support frame, with actuators respectively provided at both ends of the support frame; Two clamps, each clamp is connected to an actuator, each clamp includes a chuck and a main body, one end of the chuck is connected to the actuator, the other end of the chuck is connected to the main body, a counterbore for the bolt to be tested to pass through is provided at the end of the main body away from the chuck, and chutes are respectively provided on both sides of the counterbore; A wedge-shaped slider, a central hole for the bolt to be tested to pass through is provided in the middle of the wedge-shaped slider, first sliders are provided on both sides of the wedge-shaped slider, and the first sliders are in transitional fit with the corresponding chutes; the surface of the wedge-shaped slider close to the actuator is an inclined pressure surface, and a preset angle is formed between the inclined pressure surface and the horizontal plane, and the preset angle is used to simulate the actual bolt assembly deviation angle, and the surface of the wedge-shaped slider away from the actuator abuts against the bottom surface of the counterbore; An interference slider, an interference hole for the bolt to be tested to pass through is provided in the middle of the interference slider, and the interference amount of the interference hole on the bolt to be tested is controlled by adjusting the eccentricity of the interference hole; second sliders are provided on both sides of the interference slider, and the second sliders are in transitional fit with the corresponding chutes; The wedge-shaped slider and the interference slider are respectively arranged in two counterbores; A backing plate, the backing plate is arranged between the two clamps; a through hole for the bolt to be tested to pass through is provided on the backing plate; the two clamps are respectively arranged on both sides of the backing plate; Load sensors, a plurality of load sensors are evenly distributed circumferentially around the bolt to be tested, and after the actuator pulls the two clamps, pressure is applied to the bolt to be tested, and the load sensors acquire the real-time load data of the bolt to be tested.

2. A bolt fatigue testing device with additional bending moment and clamping interference coupling according to claim 1, characterized in that: The support frame includes a base, a connecting member, and a plurality of support members provided on the base, each support member is parallel to each other, the base is connected to the connecting member through the plurality of support members, and actuators are respectively provided on the base and the connecting member.

3. The bolt fatigue testing device with additional bending moment and clamping interference coupling according to claim 2 is characterized in that: It further includes fixing bolts, the connecting member is slidably connected to each support member, threaded holes are provided at both ends of the connecting member, and the fixing bolts pass through the threaded holes and abut against the connecting member.

4. The bolt fatigue testing device with additional bending moment and clamping interference coupling according to claim 1, characterized in that: The main body is in a "return" shape.

5. The bolt fatigue testing device with additional bending moment and clamping interference coupling according to claim 1 is characterized in that: The number of the load sensors is four, and the four load sensors are evenly distributed circumferentially around the side wall of the bolt to be tested.

6. A bolt fatigue testing device with additional bending moment and clamping interference coupling according to any one of claims 1 to 5, characterized in that: It further includes: A load collector, a data processing terminal, a controller, and a power source that are electrically connected in sequence; the input end of the load collector is connected to the load sensor, and the power source is connected to the actuator; The load collector transmits the load data of the load sensor to the data processing terminal; after the data processing terminal processes the load data, it sends a feedback signal to the controller, and the controller controls the power source to drive the actuator to move.

7. The bolt fatigue testing device with additional bending moment and clamping interference coupling according to claim 6, characterized in that: The power source includes one of a hydraulic cylinder, a pneumatic cylinder, or a driving motor.

8. A bolt fatigue test method with additional bending moment and clamping interference coupling, characterized in that: Applied to a bolt fatigue test device for coupling additional bending moment and clamping interference as described in claim 5, the method includes: Select the preset angle and the eccentricity that meet the test requirements, and start the bolt fatigue test device; In response to the start signal, the controller controls the power source to drive the actuator to operate according to a preset strategy; the preset strategy sets a maximum value for the test based on the maximum load of the bolt to be tested, and alternately cycles the load between the maximum value and the minimum value according to a preset gradient; the cycle modes include: a first mode starting with the minimum value, gradually increasing the gradient to the maximum value, and then decreasing the gradient back to the minimum value; or a second mode starting with the maximum value, gradually decreasing the gradient to the minimum value, and then increasing the gradient back to the maximum value; After the actuator starts working, the load acquisition instrument transmits the load data of the load sensor to the data processing terminal; the data processing terminal substitutes the load data and the preset angle into a preset formula to calculate the preload force and bending moment data; Within the preset number of cycles, if the calculated preload force and bending moment are lower than the preset proportion of the initial value, the test is judged to have met the requirements; otherwise, the test is judged to have failed to meet the requirements.

9. A bolt fatigue test method with additional bending moment and clamping interference coupling according to claim 8, characterized in that: The preset formula includes: ， ， in, is the preload force, is the transverse cross-sectional area of ​​the bolt, is the elastic modulus of the bolt, 、 、 and The strain data obtained by the four load sensors are: is the bending moment, is the thickness of the clamped part, The preset angle.

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