A lateral vibration and axial superposition fatigue test device

Abstract

The present invention belongs to the field of fatigue testing of plate test pieces, and particularly relates to a lateral vibration and axial superposition fatigue test device. The superposition fatigue test device includes: an upper clamping assembly, a lower clamping assembly, and an excitation assembly. The upper clamping assembly and the lower clamping assembly are used to clamp the test piece and are connected to the fatigue testing machine through a pin shaft. The fatigue testing machine provides an axial actuation mode to the test piece. The excitation assembly includes an excitation rod and an exciter. An installation hole is provided on the working section of the test piece. The first end of the excitation rod passes through the installation hole of the test piece and is fixed by a bolt. The excitation rod is perpendicular to the test piece. The exciter provides a lateral actuation mode of a set mode to the test piece through the excitation rod. In the present invention, the axial stress is concentrated on the working section of the test piece. The working section simultaneously bears the superposition of the axial conventional fatigue load and the lateral vibration fatigue load, realizing the multi-axis life estimation under non-proportional loading.

Description

Technical Field

[0001] The present invention belongs to the field of fatigue testing of plate test pieces, and particularly relates to a lateral vibration and axial superposition fatigue test device. Background Technique

[0002] During the service process of civil helicopters, there are working conditions where local vibration fatigue loads and conventional fatigue loads are superimposed on some important components, that is, there is a multi-axial fatigue situation in these components. The multi-axial fatigue estimation methods are mainly based on three criteria: The first is the maximum principal stress / strain criterion. This criterion believes that even in a multi-axial stress state, the damage of the material is mainly caused by the maximum principal stress (principal strain), and has nothing to do with other factors. The second is the von Mises equivalent stress / strain criterion. This criterion believes that in a multi-axial stress and strain state, the damage of the material is mainly controlled by the von Mises equivalent stress and strain. The third is the Tresca maximum shear stress / shear strain criterion. This theory simply attributes the damage to be only controlled by the maximum shear stress / shear strain. For the case of proportional loading, these criteria are effective and simple to use. However, in the case of non-proportional loading, especially when the hydrostatic pressure affects the fatigue life, the above criteria cannot give good prediction results. Therefore, these equivalent strain / stress theories cannot be well applied to the multi-axial life estimation under non-proportional loading.

[0003] In the actual engineering application process, the fatigue life of important components of helicopters is often in a multi-axial fatigue state under non-proportional loading. Thus, in order to systematically study the fatigue life of important components of helicopters under the action of vibration fatigue loads and conventional fatigue loads, a lateral vibration and axial conventional superposition fatigue test method needs to be designed. Summary of the Invention

[0004] In order to estimate the multi-axial life of the vibration fatigue load and the conventional fatigue load superposition condition under non-proportional loading of a plate test piece, the present invention provides a lateral vibration and axial conventional superposition fatigue test method.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] By means of a lateral vibration and axial superposition fatigue test device, a lateral vibration and axial superposition fatigue test device, characterized in that it is used to measure or pre-test the multi-axial fatigue life of a test piece, the test piece includes a first clamping section and a second clamping section, and a working section disposed between the first clamping section and the second clamping section, the lateral vibration and axial superposition fatigue test device includes:

[0007] The upper clamping assembly is used to clamp the first clamping section of the test piece and is connected to the first actuator of the fatigue testing machine through a pin shaft. The fatigue testing machine provides an axial actuation method to the test piece;

[0008] The lower clamping assembly is used to clamp the second clamping section of the test piece and is connected to the second actuator of the fatigue testing machine through a pin shaft. The fatigue testing machine provides an axial actuation method to the test piece;

[0009] The excitation assembly includes an excitation rod and an exciter. An installation hole is provided on the working section of the test piece. The first end of the excitation rod passes through the installation hole of the test piece and is fixed by a bolt. The excitation rod is perpendicular to the test piece. The exciter provides a lateral actuation method of a set mode to the test piece through the excitation rod.

[0010] In the above-mentioned lateral vibration and axial superposition fatigue test device, a support base is provided below the exciter. The height and direction of the exciter can be adjusted through the support base and fixed by a locking nut after the height position of the exciter is adjusted in place.

[0011] In the above-mentioned lateral vibration and axial superposition fatigue test device, the first actuator of the fatigue testing machine includes a first hydraulic chuck. The first hydraulic chuck clamps a first mounting rod, and the first mounting rod is connected to the upper clamping assembly;

[0012] In the above-mentioned lateral vibration and axial superposition fatigue test device, the second actuator of the fatigue testing machine includes a second hydraulic chuck. The second hydraulic chuck clamps a second mounting rod, and the second mounting rod is connected to the lower clamping assembly;

[0013] In the above-mentioned lateral vibration and axial superposition fatigue test device, the second hydraulic chuck is arranged on the base plate of the fatigue testing machine. A track is provided on the base plate, and the second hydraulic chuck can slide within the track.

[0014] In the above-mentioned lateral vibration and axial superposition fatigue test device, the position of the installation hole of the test piece is the center point of the working section;

[0015] In the above-mentioned lateral vibration and axial superposition fatigue test device, the excitation rod is connected to the installation hole through a nut, and a buffer pad is provided between the test piece and the nut;

[0016] In the above-mentioned lateral vibration and axial superposition fatigue test device, the buffer pad is a silica gel pad or a flat washer.

[0017] In the above-mentioned lateral vibration and axial superposition fatigue test device, the test device further includes a test parameter adjustment assembly. The test parameter adjustment assembly includes an axial actuation adjustment part and a lateral actuation adjustment part.

[0018] In the above lateral vibration and axial superposition fatigue test device, the axial actuation adjustment member adjusts the stress and test frequency of the fatigue testing machine, and the lateral actuation adjustment member adjusts the force value and test frequency of the excitation assembly.

[0019] In the above lateral vibration and axial superposition fatigue test device, the axial actuation adjustment member adjusts the maximum stress of the fatigue testing machine to be 0.7 to 0.9 times the yield strength of the test piece;

[0020] In the above lateral vibration and axial superposition fatigue test device, the axial actuation adjustment member adjusts the test frequency of the fatigue testing machine to be 0.5 to 0.7 times the natural frequency of the test piece.

[0021] In the above lateral vibration and axial superposition fatigue test device, the axial actuation method adopts stress control with a stress ratio R = 0.8; the lateral actuation method adopts force value control with a stress ratio R = -1.

[0022] In the above lateral vibration and axial superposition fatigue test device, the test piece is a 7050-T7451 sheet. The numerical value of the axial force in the axial actuation method is selected as 360 - 550 Mpa, 10 - 70 Hz; the numerical value of the lateral force in the lateral actuation method is selected as 0 - 120 N, 50 - 70 Hz.

[0023] In the above lateral vibration and axial superposition fatigue test device, the test device further includes a temperature control assembly. The temperature control assembly includes a temperature measuring member and a blower. The temperature measuring member is placed at the working section of the test piece to measure the temperature of the working section of the test piece. The blower is arranged facing the working section. When the temperature measured by the temperature measuring member exceeds 60 °C, the cooling air volume provided by the blower is increased.

[0024] In the above lateral vibration and axial superposition fatigue test device, the test device further includes a test stop control assembly. When the test piece breaks or the test frequency changes by more than ±5% or the test piece is intact but the number of cycles reaches 1×10 6 times, the test stop control assembly controls the fatigue testing machine and the excitation assembly to stop acting.

[0025] By means of the above technical solutions, the present invention has at least the following advantages:

[0026] 1) Through the combined action of the upper clamping assembly and the lower clamping assembly, the present invention concentrates the axial stress on the working section of the test piece, and superimposes lateral vibration on the working section, so as to enable the working section to simultaneously bear the superposition of the axial conventional fatigue load and the lateral vibration fatigue load. Under the superposition of the two loads, the maximum stress of the test piece should be located in the working section, and the multi-axial life under non-proportional loading is estimated by fitting formulas.

[0027] 2) By further defining the parameters of the axial actuation and the lateral actuation, and applying the lateral actuation mode after the axial actuation mode is stable, the present invention can avoid the situation that the test piece breaks at the beginning of the superimposed fatigue test.

[0028] The above description is only an overview of the technical solution of the present invention. In order to be able to more clearly understand the technical means of the present invention and implement it in accordance with the content of the specification, the following takes the preferred embodiments of the present invention and combines with the drawings to elaborate in detail as follows. Brief Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of the lateral vibration and axial superimposed fatigue test device of the present invention. Detailed Description of the Preferred Embodiments

[0030] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following combines with the drawings and preferred embodiments to elaborate in detail on the specific implementation manners, structures, features and effects of the present invention according to the application.

[0031] As Figure 1 shown, the lateral vibration and axial superimposed fatigue test device of the present invention is used to measure or pre-test the multi-axial fatigue life of the test piece 4. The test piece 4 includes a first clamping section and a second clamping section, and a working section provided between the first clamping section and the second clamping section. The lateral vibration and axial superimposed fatigue test device includes:

[0032] An upper clamping assembly 3 for clamping the first clamping section of the test piece 4 and connected to the first actuator of the fatigue testing machine through a pin shaft 3. The fatigue testing machine provides an axial actuation mode to the test piece 4;

[0033] A lower clamping assembly 5 for clamping the second clamping section of the test piece 4 and connected to the second actuator of the fatigue testing machine through a pin shaft 3. The fatigue testing machine provides an axial actuation mode to the test piece 4;

[0034] The excitation assembly includes an excitation rod 8 and an exciter 10. An installation hole is provided on the working section of the test piece 4. The first end of the excitation rod 8 passes through the installation hole of the test piece 4 and is fixed by bolts. The excitation rod 8 is perpendicular to the test piece 4. The exciter 10 provides a lateral actuation method of a set type to the test piece 4 through the excitation rod 8.

[0035] A support base 9 is provided below the exciter 10. The height and direction of the exciter 10 can be adjusted through the support base 9, and after the height position of the exciter 10 is adjusted in place, it is fixed by a lock nut.

[0036] When the present invention is specifically implemented, in order to concentrate the stress on the working section of the test piece 4, it is necessary to determine a reasonable specimen form of the test piece 4 through finite element analysis to ensure that the stress is concentrated on the working section of the test piece 4.

[0037] The upper clamping assembly 3 and the lower clamping assembly 5 of the present invention are connected to the fatigue testing machine through a pin shaft 3. The pin shaft 3 does not restrict its rotational freedom, so as to ensure that the test piece 4 and the axial force are on the same straight line and avoid additional bending moments on the test piece 4 caused by axial loads.

[0038] The first actuator of the fatigue testing machine includes a first hydraulic chuck 1. The first hydraulic chuck 1 clamps a first mounting rod 2, and the first mounting rod 2 is connected to the upper clamping assembly 1;

[0039] The second actuator of the fatigue testing machine includes a second hydraulic chuck 6. The second hydraulic chuck 6 clamps a second mounting rod, and the second mounting rod is connected to the lower clamping assembly 5;

[0040] The second hydraulic chuck is arranged on the base plate 7 of the fatigue testing machine. A track is provided on the base plate 7, and the second hydraulic chuck can slide within the track.

[0041] The position of the installation hole of the test piece 4 is the center point of the working section;

[0042] The excitation rod 8 is connected to the installation hole through a nut, and a buffer pad is provided between the test piece 4 and the nut; the excitation rod 8 is fixed by the nut. The main function of the buffer pad is to prevent the test piece 4 from rigid contact with the nut and cause erosion fatigue. Preferably, the buffer pad is a silica gel pad or a flat washer.

[0043] The test device further includes a test parameter adjustment assembly. The test parameter adjustment assembly includes an axial actuation adjustment member and a lateral actuation adjustment member.

[0044] The axial actuation adjustment member adjusts the stress and test frequency of the fatigue testing machine, and the lateral actuation adjustment member adjusts the force value and test frequency of the excitation assembly.

[0045] The lateral vibration and axial superposition fatigue test device of the present invention. The acting position of the lateral vibration is obtained through finite element simulation analysis so as to effectively apply a load to the working section of the test piece 4. Specifically, when preparing the test piece 4 in a set style, finite element simulation is carried out on the test piece 4, so as to determine the specific position of the applied load on the one hand, and on the other hand, the form of the test piece 4 and the natural frequency of the test piece 4 can also be determined.

[0046] In order to avoid the premature fracture of the test piece 4, during the specific implementation, we adjust the relationship between the axial load and the lateral vibration fatigue load to explore the load corresponding to the target fatigue life of the test.

[0047] Specifically, the axial actuator adjusts the maximum stress of the fatigue testing machine to be 0.7 - 0.9 times the yield strength of the test piece 4, and the axial actuator adjusts the test frequency of the fatigue testing machine to be 0.5 - 0.7 times the natural frequency of the test piece 4.

[0048] The axial actuation method adopts stress control with a stress ratio R = 0.8; the lateral actuation method adopts force value control with a stress ratio R = -1.

[0049] In a specific embodiment of the present invention, the test piece 4 is a 7050 - T7451 plate. The value of the axial force of the axial actuation method is selected to be 360 - 550 Mpa and 10 - 70 Hz; the value of the lateral force of the lateral actuation method is selected to be 0 - 120 N and 50 - 70 Hz.

[0050] The test device further includes a temperature control component. The temperature control component includes a temperature measuring element and a blower. The temperature measuring element is placed at the working section of the test piece 4 for measuring the temperature of the working section of the test piece 4. The blower is arranged facing the working section. When the temperature measured by the temperature measuring element exceeds 60 °C, the cooling air volume provided by the blower is increased.

[0051] The test device further includes a test stop control component. When the test piece breaks, or the test frequency changes by more than ±5%, or the test piece is intact but the number of cycles reaches 1×10 6 When it reaches, the test stop control component controls the fatigue testing machine and the excitation component to stop acting.

[0052] The raw material of the test piece in this embodiment is 7050-T7451 plate (L*T*S: 1250×355×88.9 mm). It is cut into pieces by band saw and by wire cutting to prepare plates (L*T*S: 122×32×5 mm) for processing the test piece. In specific implementation, the design of the test piece for the superposition of lateral vibration and axial fatigue refers to the standard HB 5277-84 "Vibration Fatigue Test Method for Engine Blades and Materials" for design. To achieve lateral loading, mounting holes are added at the center of the cantilever beam, and at the same time, the width dimension of the test piece is increased accordingly. After the test piece is processed, all test pieces are inspected using a universal tool microscope, the working surface of the test piece is inspected using an optical instrument, and the key dimensions are measured. The inspection of the test piece is strictly carried out according to the requirements of the drawing. The actual dimensions of the test piece are within the drawing tolerance range, the surface roughness meets the drawing requirements, and there are no scratches, detectable cracks or obvious defects.

[0053] Specifically, the length of the test piece is 120±0.2 mm, the width of the test piece is 30±0.2 mm, the thickness of the test piece is 3±0.05 mm, the diameter of the mounting hole is 5.5, two strain gauges are arranged on both sides of the mounting hole, and the distance between the two strain gauges is 14±1 mm.

[0054] Specifically, the process of the superposition fatigue test is as follows: Before the test, check the key dimensions and appearance quality of the test piece, and fill in the original record sheet; install the test piece and the fixture as required; first set the axial test parameters and turn on the electro-hydraulic servo fatigue testing machine; set the lateral vibration fatigue parameters, and after the axial test runs stably, turn on the lateral exciter; during the test, use an infrared thermometer to measure the temperature of the working section of the test piece. If the temperature exceeds 60°C, it is necessary to increase the cooling air volume to keep the measured temperature of the working section of the test piece within 60°C (that is, control the temperature of the working section within 0~60°C);

[0055] The formal test is carried out by the group method: The 3-level group method is used for testing, and the expected lives are 50,000, 100,000~200,000, and about 300,000~500,000 respectively. At most 5 pieces are tested for each level;

[0056] After the test piece breaks, observe the fracture position and judge whether the fracture position is valid (fracture within the working section is valid data); fill in the original record form;

[0057] After reaching the set stop condition, remove the test piece, take a photo of the test piece, and then store the test piece in a drying dish to preserve the fracture morphology of the test piece.

[0058] The set stop condition is: the test piece breaks; or the test frequency changes by more than ±5%; or when the number of cycles reaches 1×10 6 and the test piece is intact.

[0059] During the specific test process, the test frequency is monitored and displayed in real time. By setting the set frequency value, if the test frequency exceeds the set value, the device will automatically stop the test.

[0060] If the set stop condition is that the test piece breaks, it is necessary to judge whether the fracture position is effective by observing the fracture position. Among them, the fracture position within the working section area of the test piece is effective, and the obtained axial fatigue life and lateral fatigue life are effective data.

[0061] The lateral vibration and axial superposition fatigue test device of the present invention further includes a multiaxial fatigue life prediction component. The prediction component is electrically connected to the fatigue testing machine and the exciter. The prediction component uses the basic parameters of the test piece, the actuation modes of the clamping component and the excitation component as inputs to predict the multiaxial fatigue life. The specific method is as follows: Set the axial actuation mode and the lateral vibration actuation mode as the first test parameters, conduct the superposition fatigue test of the first test type until the set stop condition, and obtain the axial fatigue life and lateral fatigue life of the first test type; Based on the mean values of the axial fatigue life and lateral fatigue life of the first test type as basic data, substitute them into the following formula (1) to solve for the fitting constants k, m, and n;

[0062] (1)

[0063] In the formula:

[0064] is the maximum normal stress on the plane of the maximum shear strain;

[0065] is the yield strength of the material;

[0066] and are the fatigue plasticity coefficient and strength coefficient;

[0067] c is the fatigue plasticity index;

[0068] b is the fatigue strength index;

[0069] N c is the lateral fatigue life;

[0070] N f is the axial fatigue life;

[0071] k, m, n are fitting constants.

[0072] Then, substitute the fitting constants k, m, and n obtained in step 3 into formula (1) to form a fitted formula. Reset the axial actuation mode and the lateral vibration actuation mode to the Nth test parameter, and use the fitted formula to solve for the axial life and the lateral life of the Nth test type, which is the multiaxial fatigue life.

[0073] In specific implementation, the present invention sets three test types, where test type 1 is the first test type, and test types 2 and 3 are the later pre-test types.

[0074] The test type matrix of the present invention is shown in Table 1 below:

[0075] Table 1 Lateral Vibration and Axial Fatigue Superposition Test Matrix

[0076]

[0077] In the present invention, the maximum normal stress is the superposition stress of the axial stress provided by the axial actuation mode and the lateral stress provided by the lateral actuation mode. The equivalent stress calculation formula of the maximum normal stress is: , where is the equivalent stress of the maximum normal stress, is the axial stress, is the lateral stress.

[0078] Among them, the axial stress is much greater than the lateral stress .

[0079] Preferably, the axial stress ≥ 90 times the lateral stress .

[0080] Preferably, the axial stress ≥ 100 times the lateral stress .

[0081] In this embodiment, in the specific calculation process, since the lateral actuation mode uses force value control, when calculating the equivalent stress, first calculate the corresponding stress from the force value of the lateral force. The lateral force of test type 1 / 3 in this embodiment is 120 N, and the corresponding stress is 4 MPa; the stress corresponding to test type 2 is 2 MPa.

[0082] Calculate the equivalent stress of test types 1 and 3 according to Von Mises:

[0083]

[0084]

[0085]

[0086] Calculate the von Mises equivalent stress for test type 2:

[0087]

[0088]

[0089]

[0090] During the test, the axial test frequency will affect the temperature of the test piece. If the frequency is too high, the test piece will overheat, thus affecting the test results. Therefore, it is necessary to limit the axial test frequency to 0.5 - 0.7 times the natural frequency.

[0091] The lateral test frequency should be far from the resonance frequency of the test piece, so as to enable the test to proceed smoothly and avoid the fracture of the test piece caused by resonance.

[0092] The value of the lateral test frequency ≤ the value of the resonance frequency - 30. For example, in the specific embodiment of the present application, when the resonance frequency (swept - frequency resonance frequency is about 100 Hz), the fatigue performance is worse at a lateral frequency of 70 Hz in test type 3 than in test type 1 and test type (lateral test frequency is 50 Hz).

[0093] The present invention obtains the axial fatigue life and lateral fatigue life of the first test type through the first test type. After solving the fitting constants k, m, and n through formula (1), a fitting formula is formed for the multiaxial life estimation under non - proportional loading of axial stress and lateral stress. In this way, it is possible to predict the multiaxial fatigue life of the lateral vibration and axial superposition fatigue test of other test types by obtaining the fitting formula through the test of one test type. Thus, the time for obtaining the multiaxial fatigue life of different types is reduced.

[0094] According to the tensile test, it is known that the elastic modulus of 7050 - T7451 material is 70.55 GPa, and the material yield strength is 466.5 MPa; referring to the data, the shear modulus of the material is 26.9 GPa.

[0095] Referring to LY12CZ material, the fatigue plasticity index c is taken as - 0.654, the plasticity coefficient is 0.137; the fatigue strength index b is taken as - 0.063, and the strength coefficient is 724 MPa.

[0096] Substitute the known parameters into formula (1) to obtain the fitting constants k = - 1, m = - 0.013, n = - 0.0712. Then the fitted formula is written as:

[0097]

[0098] Use the fitted formula to predict the axial life of test type 2 and test type 3. The results are shown in Table 2 below:

[0099] Table 2 Axial life prediction results in the superimposed life

[0100]

[0101] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A lateral vibration and axial superposition fatigue test device, characterized in that For measuring or predicting the multiaxial fatigue life of a test specimen to be tested, the test specimen includes a first clamping section and a second clamping section, and a working section disposed between the first clamping section and the second clamping section. The lateral vibration and axial superposition fatigue test device includes: An upper clamping assembly for clamping the first clamping section of the test specimen and connected to a first actuator of a fatigue testing machine through a pin shaft. The fatigue testing machine provides an axial actuation mode to the test specimen; A lower clamping assembly for clamping the second clamping section of the test specimen and connected to a second actuator of the fatigue testing machine through a pin shaft. The fatigue testing machine provides an axial actuation mode to the test specimen; An excitation assembly including an excitation rod and an exciter. An installation hole is provided on the working section of the test specimen. The first end of the excitation rod passes through the installation hole of the test specimen and is fixed by a bolt. The excitation rod is perpendicular to the test specimen. The exciter provides a lateral actuation mode of a set manner to the test specimen through the excitation rod. The value of the test frequency of the lateral actuation mode ≤ the value of the resonance frequency - 30; A multiaxial fatigue life prediction component. The prediction component is electrically connected to the fatigue testing machine and the exciter. The prediction component takes the basic parameters of the test specimen, the actuation modes of the clamping assembly and the excitation assembly as inputs to predict the multiaxial fatigue life. The specific method is as follows: Set the axial actuation mode and the lateral vibration actuation mode as the first test parameters, conduct a superposition fatigue test of the first test type until a set stop condition is reached, and obtain the axial fatigue life and the lateral fatigue life of the first test type; Based on the average values of the axial fatigue life and the lateral fatigue life of the first test type as basic data, substitute them into the following formula (1) to solve for the fitting constants k, m, and n; （1） Where: is the maximum normal stress on the maximum shear strain plane; is the yield strength of the material; and are the fatigue plasticity coefficient and strength coefficient; c is the fatigue plasticity index; b is the fatigue strength index; N c is the lateral fatigue life; N f is the axial fatigue life; k, m, and n are fitting constants; Substitute the solved fitting constants k, m, and n into formula (1) to form a fitted formula. Reset the axial actuation mode and the lateral vibration actuation mode as the Nth test parameters, and use the fitted formula to solve for the axial life and the lateral life of the Nth test type, which is the multiaxial fatigue life.

2. The lateral vibration and axial superposition fatigue test device according to claim 1, wherein A support base is provided below the exciter. The height and direction of the exciter can be adjusted through the support base and fixed by a lock nut after the height position of the exciter is adjusted in place.

3. The lateral vibration and axial superposition fatigue test device according to claim 1, wherein The first actuator of the fatigue testing machine includes a first hydraulic chuck. The first hydraulic chuck clamps a first mounting rod, and the first mounting rod is connected to the upper clamping assembly; The second actuator of the fatigue testing machine includes a second hydraulic chuck. The second hydraulic chuck clamps a second mounting rod, and the second mounting rod is connected to the lower clamping assembly; The second hydraulic chuck is disposed on the base plate of the fatigue testing machine. A track is provided on the base plate, and the second hydraulic chuck slides within the track.

4. The lateral vibration and axial superposition fatigue test device according to claim 1, characterized in that the position of the mounting hole of the test piece is the center point of the working section; the excitation rod is connected to the mounting hole through a nut, and a buffer pad is provided between the test piece and the nut; the buffer pad is a silica gel pad or a flat washer.

5. The lateral vibration and axial superposition fatigue test device according to claim 1, characterized in that the test device further includes a test parameter adjustment component, and the test parameter adjustment component includes an axial actuation adjustment component and a lateral actuation adjustment component, the axial actuation adjustment component adjusts the stress and test frequency of the fatigue testing machine, and the lateral actuation adjustment component adjusts the force value and test frequency of the excitation component.

6. The lateral vibration and axial superposition fatigue test device according to claim 5, characterized in that the axial actuation adjustment component adjusts the maximum stress of the fatigue testing machine to be 0.7 to 0.9 times the yield strength of the test piece; the axial actuation adjustment component adjusts the test frequency of the fatigue testing machine to be 0.5 to 0.7 times the natural frequency of the test piece.

7. The lateral vibration and axial superposition fatigue test device according to claim 1, characterized in that the axial actuation method adopts stress control, and the stress ratio R = 0.8; the lateral actuation method adopts force value control, and the stress ratio R = -1.

8. The lateral vibration and axial superposition fatigue test device according to claim 1, characterized in that the test piece is a 7050-T7451 plate, and the numerical value of the axial force in the axial actuation method is selected to be 360 - 550 Mpa, 10 - 70 Hz; the numerical value of the lateral force in the lateral actuation method is selected to be 0 - 120 N, 50 - 70 Hz.

9. The lateral vibration and axial superposition fatigue test device according to claim 1, characterized in that the test device further includes a temperature control component, and the temperature control component includes a temperature measuring element and a blower. The temperature measuring element is placed at the working section of the test piece to measure the temperature of the working section of the test piece. The blower is arranged facing the working section. When the temperature measured by the temperature measuring element exceeds 60 °C, the cooling air volume provided by the blower is increased.

10. The lateral vibration and axial superposition fatigue test device according to claim 1, characterized in that The test device further includes a test stop control component. When the test piece breaks, or the test frequency changes by more than ±5%, or the test piece is intact but the number of cycles reaches 1×10 6 , the test stop control component controls the fatigue testing machine and the excitation component to stop operating.

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