A high-cycle fatigue life test method and device for a thin-walled impact-locked structure

Abstract

The application discloses a high-cycle fatigue life test method and device for a thin-wall impact locking structure, relates to the technical field of thin-wall impact locking structures, and aims at solving the problems that there is currently a lack of a test method for the mechanical properties of a locking structure after large plastic deformation, and test pieces used in existing thin-wall tests are prone to breaking. The method comprises the following steps: obtaining a first target loading load and a second target loading load; the test piece is in a cantilever beam structure; based on the first target loading load, an initial plastic strain force loading treatment is performed on the test piece by using a test device, so that a target test piece is obtained; and based on the second target loading load, a high-cycle fatigue test is performed on the test piece by using the test device. The high-cycle fatigue life test method for the thin-wall impact locking structure provided by the application is not prone to breaking, and can realize the fatigue life test of a locking structure after large plastic deformation.

Description

Technical Field

[0001] This invention relates to the field of thin-walled stamping locking structure technology, and in particular to a high-cycle fatigue life test method and apparatus for a thin-walled stamping locking structure. Background Technology

[0002] The engine turbine assembly extensively uses anti-loosening locking parts to assemble and lock fasteners, seals, and other structures. During the assembly process, the locking structure undergoes significant local plastic deformation. Under engine operating conditions, the structure is subjected not only to mechanical vibration loads but also to fluid excitation forces generated by medium pulsation. Under these vibration loads, the structure is at risk of fatigue failure, which seriously affects the service safety of the turbopump and the engine. Therefore, a detailed assessment of the fatigue life of such structures is necessary.

[0003] Currently, there is no performance testing method for locking structures after large plastic deformation. Furthermore, conventional thin plate fatigue testing methods cannot control the magnitude of plastic strain during testing due to excessive plastic strain, making the test pieces prone to fracture.

[0004] Therefore, there is an urgent need for a high-cycle fatigue life test method and apparatus for thin-walled stamping locking structures. Summary of the Invention

[0005] The purpose of this invention is to provide a high-cycle fatigue life test method and apparatus for thin-walled stamped locking structures, which solves the current lack of mechanical property test methods for locking structures after large plastic deformation, and the problem that the test pieces used in existing thin-walled tests are prone to fracture.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a high-cycle fatigue life test method for a thin-walled stamped locking structure, comprising:

[0008] Obtain the first target loading load and the second target loading load of the test specimen; the test specimen is a cantilever beam structure, the cantilever beam structure includes a fixed block and a cantilever structure installed on the side of the fixed block and flush with the upper surface of the fixed block, the thickness of the cantilever structure is the same as the thickness of the thin-walled structure of the target locking structure;

[0009] Based on the first target loading load, the test piece is subjected to initial plastic strain loading using a test device to obtain the target test piece; the first target loading load brings the cantilever structure closer to the fixed block;

[0010] Based on the second target loading load, the test device is used to conduct a high-cycle fatigue test on the test piece; the second target loading load moves the cantilever structure away from the fixed block.

[0011] Optionally, the test piece further includes an evaluation component; the evaluation component is a structure disposed at the connection between the fixed block and the cantilever structure, the evaluation component is a rounded corner structure, the fixed block and the cantilever structure are integrally formed, the fixed block is a cubic structure, and a first through hole is provided along the height direction of the fixed block; the upper and lower surfaces of the cantilever structure are provided with limiting bosses, and the limiting bosses are disposed at the end away from the fixed block.

[0012] Optionally, the testing device includes a fixing clamp and a loading end. The fixing clamp includes a first clamping rod with external threads and a support structure. The first clamping rod is a cylindrical structure. The longitudinal section of the support structure is L-shaped. The support structure includes a cylindrical base and a semi-cylindrical protrusion disposed at one axial end of the cylindrical base. The semi-cylindrical protrusion is provided with a fixing groove that penetrates the semi-cylindrical protrusion in a direction perpendicular to the axial direction of the semi-cylindrical protrusion. The size of the end face of the fixing groove is the same as the size of the side of the fixing block connected to the cantilever structure. A second through hole is provided in the axial direction of the semi-cylindrical protrusion that penetrates the semi-cylindrical protrusion and communicates with the fixing groove. The diameter of the second through hole is the same as that of the first through hole. The loading end includes a second clamping rod with external threads and a pressure head. The second clamping rod and the pressure head are connected in a T-shape.

[0013] Optionally, the step of applying initial plastic strain force to the test specimen using a testing device based on the first target loading load to obtain the target test specimen further includes:

[0014] The test piece is placed in the fixing slot, and the test piece and the fixing fixture are fixed with bolts so that the upper surface of the cantilever structure of the test piece is flush with the upper surface of the fixing slot.

[0015] The fixing clamp is fixed to the fixed end chuck of the testing machine by means of the first clamping rod;

[0016] The loading end is fixed to the loading end clamp of the testing machine by the second clamping rod, so that the pressure head contacts the upper surface of the cantilever structure and the pressure head is parallel to the cantilever structure, thus completing the installation of the testing device.

[0017] Optionally, the first target loading load is displacement, and the initial plastic strain loading treatment of the test specimen using a testing device based on the first target loading load to obtain the target test specimen includes:

[0018] The loading end is controlled by the testing machine to move downward at a constant speed until the displacement reaches the first target loading load. Then, the loading end is controlled to move upward at a constant speed until the pressure head separates from the cantilever structure and stops, thus obtaining the target test piece.

[0019] Optionally, the second target load is displacement, and based on the second target load, the high-cycle fatigue test of the test piece using the test apparatus includes:

[0020] In the test apparatus, the target test piece is rotated 180° so that the upper surface of the cantilever structure is flush with the lower surface of the fixing slot, and the target test piece is fixed to the fixing fixture.

[0021] The loading end head is fixed to the loading end chuck of the testing machine by the clamping rod, and the pressure head is kept in contact with and parallel to the lower surface of the cantilever structure of the target test piece;

[0022] The loading end is controlled by the testing machine to move downward at a constant speed until the displacement reaches the second target loading load. Then, the loading end is controlled to move upward at a constant speed until the pressure head separates from the cantilever structure, thus completing one fatigue test.

[0023] The fatigue test is performed cyclically at a preset loading frequency until the test piece fractures, thus completing the high-cycle fatigue test.

[0024] Optionally, obtaining the first target loading load and the second target loading load of the test specimen includes:

[0025] Numerical simulation was used to simulate two opposing compressive bending processes on the test piece of the test device to obtain simulation data;

[0026] Based on the simulation data and the target plastic stress, the first target loading load and the second target loading load are determined on the test specimen.

[0027] Optionally, the numerical simulation method is used to simulate two opposing compressive bending processes on the test piece of the test device, and the simulation data obtained includes:

[0028] Construct a numerical model of the experimental setup;

[0029] Based on the numerical model, the cantilever structure is loaded according to the first preset displacement to simulate the downward bending process of the cantilever structure under pressure, and the first relationship curve between the plastic strain of the test component and the compressive displacement of the cantilever structure is obtained.

[0030] Based on the numerical model, the cantilever structure is subjected to reverse loading according to the second preset displacement to simulate the upward bending process of the cantilever structure under reverse pressure, and a second relationship curve between the plastic strain of the test component and the reverse pressure displacement of the cantilever structure is obtained.

[0031] Optionally, the target locking structure includes an annular cylinder and a thin-walled structure integrally formed with the annular cylinder. The thin-walled structure is annular and is disposed at one end of the annular cylinder along its axial direction. The inner diameter of the thin-walled structure is the same as the outer diameter of the annular cylinder. A connecting component is provided at the connection between the thin-walled structure and the outer side of the annular cylinder. The connecting component has a rounded corner structure and is disposed along the circumference of the annular cylinder. The rounded radius of the testing component is the same as the rounded radius of the connecting component.

[0032] Compared with existing technologies, this invention provides a high-cycle fatigue life test method for a thin-walled impact locking structure, comprising: obtaining a first target loading load and a second target loading load on the test piece; based on the first target loading load, using a testing device to perform initial plastic strain loading on the test piece to obtain a target test piece; the first target loading load brings the cantilever structure closer to the fixed block; based on the second target loading load, using a testing device to perform a high-cycle fatigue test on the test piece; and the second target loading load moves the cantilever structure away from the fixed block. This application can realize fatigue life testing of structures after large plastic deformation, providing support for the safety and reliability of structural service. The test piece using a cantilever beam structure utilizes local stress concentration to ensure that the test piece can meet large plastic stress without fracture. The cantilever structure can simulate the thin-walled structure of the target locking structure, accurately reproducing the state of the target locking structure in actual use where one end is fixed and the other end is stressed. Furthermore, the initial plastic strain loading treatment on the test piece can simulate the plastic deformation experienced during assembly of the target locking structure, ensuring the validity of the test data. Based on this, the high-cycle fatigue life test is conducted, making the test more accurate.

[0033] Secondly, the present invention also provides a high-cycle fatigue life testing device for a thin-walled stamped locking structure, which is applied to the high-cycle fatigue life testing method of the thin-walled stamped locking structure. The testing device includes at least: a test piece, the test piece being a cantilever beam structure, the cantilever beam structure including a fixed block and a cantilever structure installed on the side of the fixed block and flush with the upper surface of the fixed block, the thickness of the cantilever structure being the same as the thickness of the thin-walled structure of the target locking structure;

[0034] The testing apparatus is used to perform initial plastic strain loading on the test specimen and to conduct high-cycle fatigue tests on the test specimen.

[0035] Compared with the prior art, the beneficial effects of the high-cycle fatigue life testing device for a thin-walled stamping locking structure provided by the present invention are the same as the beneficial effects of the high-cycle fatigue life testing method for a thin-walled stamping locking structure described in the above technical solution, and will not be repeated here. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 A schematic diagram of the target locking structure provided by the present invention;

[0038] Figure 2 A schematic diagram of the test piece for a high-cycle fatigue life testing device with a thin-walled stamping locking structure provided by the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of the fixing clamp provided by the present invention;

[0040] Figure 4 This is a schematic diagram of the structure of the loading end provided by the present invention;

[0041] Figure 5 A flowchart of a high-cycle fatigue life test method for a thin-walled stamping locking structure provided by the present invention;

[0042] Figure 6 A schematic diagram of the loading of the test apparatus during the initial plastic strain loading treatment of the test specimen provided by the present invention;

[0043] Figure 7 This is a schematic diagram of the loading of the test apparatus for high-cycle fatigue testing provided by the present invention.

[0044] Figure label:

[0045] 11-Thin-walled structure, 12-Connecting component, 13-Annular cylinder, 21-Fixing block, 211-First through hole, 22-Cantilever structure, 221-Limiting protrusion, 23-Assessment component, 31-First clamping rod, 32-Supporting structure, 321-Cylinder base, 322-Semi-cylindrical protrusion, 323-Fixing slot, 324-Second through hole, 41-Second clamping rod, 42-Pressure head. Detailed Implementation

[0046] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0047] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0048] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0049] After undergoing large plastic deformation, the tensile, fatigue, and other mechanical properties of thin-walled locking structures will change to some extent. This leads to a lack of relevant performance data when assessing the fatigue life of the structure, and the results obtained by using general performance data have large errors. At present, there are no corresponding standard specifications for testing the material properties after large plastic deformation. Most tests are designed and tested based on engineering experience. For some simple tests, traditional test specimens can meet the requirements. However, for tests under certain complex conditions, conventional test methods are no longer applicable, and new test structures and test methods need to be considered.

[0050] The locking structures widely used in turbopump assemblies undergo significant plastic deformation during assembly, exhibiting marked tensile-compressive asymmetry. This results in a large strain gradient within the structure, with localized plastic strains approaching or even exceeding the material's elongation at fracture. While introducing the same initial plastic strain during material fatigue performance testing can ensure data validity, conventional thin-plate fatigue testing methods present significant challenges due to the excessive plastic strain. These challenges include the inability to control the strain magnitude and a high risk of specimen fracture, posing a major obstacle to experimental testing.

[0051] To address the aforementioned problems, this invention provides a high-cycle fatigue life testing method and apparatus for thin-walled stamped locking structures. It designs a test specimen capable of undergoing fatigue testing after large plastic deformation, and uses corresponding testing methods to conduct high-cycle fatigue life tests on structures after large plastic deformation, providing support for the safety and reliability of the structure in service. The following description is in conjunction with the accompanying drawings.

[0052] See Figure 1 The target locking structure is a thin-walled indentation locking structure. The target locking structure includes an annular cylinder 13 and a thin-walled structure 11 integrally formed with the annular cylinder 13. The thin-walled structure 11 is annular and is located at one end of the annular cylinder 13 along its axial direction. The inner ring diameter of the thin-walled structure 11 is the same as the outer ring diameter of the annular cylinder 13. A connecting component 12 is provided at the connection between the thin-walled structure 11 and the outer side of the annular cylinder 13. The connecting component 12 has a rounded corner structure and is arranged along the circumference of the annular cylinder 13.

[0053] See Figures 2-4 The present invention provides a high-cycle fatigue life testing device for a thin-walled stamping locking structure, comprising a test piece, a fixing fixture, and a loading end, such as... Figure 2 As shown in (a), the test piece is a cantilever beam structure, which includes a fixing block 21 and a cantilever structure 22 installed on the side of the fixing block 21 and flush with the upper surface of the fixing block 21. The fixing block 21 and the cantilever structure 22 are integrally formed. The fixing block 21 has a cubic structure and a first through hole 211 through the fixing block 21 along the height direction. The first through hole 211 is a threaded hole. A limiting protrusion 221 is provided at the end of the cantilever structure 22 away from the fixing block 21. The limiting protrusion 221 includes a protrusion provided on the upper surface of the cantilever structure and a protrusion provided on the lower surface of the cantilever structure. The thickness of the cantilever structure 22 is the same as the thickness of the thin-walled structure 11 of the target locking structure; as Figure 2As shown in (b), the test piece also includes a test component 23, which is a structure located at the connection between the fixed block 21 and the cantilever structure 22. The test component 23 has rounded corners, and its length is the same as that of the cantilever structure. The rounded radius of the test component is the same as that of the connecting component of the target locking structure. The cantilever structure is used to bear the initial plastic strain load and fatigue load and transfer the load to the test component. The limiting boss is used to limit the load during the test and prevent the test piece from slipping. It should be noted that the upper surface of the fixed block, the upper surface of the cantilever structure, and the lower surface of the test piece are designed according to... Figure 2 (a) shows the corresponding upper and lower surfaces when the structure is positioned as shown. The height direction of the fixed block is perpendicular to the cantilever structure.

[0054] In practical applications, the test piece is manufactured as a whole. A cantilever structure is machined on the right side of the fixed end by cutting. The upper and lower surfaces of the cantilever structure are machined, and a limiting boss is left at the right end. The lower surface of the connection between the cantilever structure and the fixed end is rounded to form the test component. A first through hole is machined at the center of the fixed end, which runs through the upper and lower surfaces of the fixed end for fixing with the fixing fixture.

[0055] like Figure 3 As shown, the fixing fixture includes a support structure 32 and a first clamping rod 31 with external threads. The first clamping rod 31 is a cylindrical structure. The longitudinal section of the support structure 32 is L-shaped. The support structure 32 includes a cylindrical base 321 and a semi-cylindrical protrusion 322 disposed at one axial end of the cylindrical base 321. The first clamping rod 31 is disposed at the other axial end of the cylindrical base 321. The area of ​​the cylindrical base 321 away from the first clamping rod 31, excluding the semi-cylindrical protrusion 322, is the test area, which is used to provide test space for initial plastic strain loading treatment and high cycle fatigue test. The semi-cylindrical protrusion 322 is provided with a fixing groove 323 that passes through the semi-cylindrical protrusion 322 along a first direction. The fixing groove is used to install the test piece. The first direction is perpendicular to the axial direction of the semi-cylindrical protrusion. The size of the end face of the fixing groove 323 is the same as the size of the side of the fixing block that is connected to the cantilever structure 22. The semi-cylindrical protrusion 322 is also provided with a second through hole 324 that passes through the semi-cylindrical protrusion along a second direction and communicates with the fixing groove 323. The second direction is the axial direction of the semi-cylindrical protrusion. The diameter of the second through hole 324 is the same as that of the first through hole 211. The two form a corresponding relationship. The test piece and the fixing fixture are fixed by bolts.

[0056] like Figure 4 As shown, the loading end includes a pressure head 42 and a second clamping rod 41 with external threads. The second clamping rod 41 and the pressure head 42 are connected in a T-shape. The loading end can be formed by machining and welding two cylinders.

[0057] In the above structure, the first clamping rod and the support are connected by welding, while the support is manufactured as a single piece. The fixing fixture is used to clamp the test specimen and fix it during the test, while the loading end is used for loading during the test. The fixing fixture has reserved space for clamping the test specimen and the test area, ensuring that it can adapt to the loading methods of commonly used fatigue testing equipment. The indenter is used to apply the initial plastic strain load and the fatigue load.

[0058] The aforementioned testing apparatus is used to perform initial plastic strain loading on the test specimen and to conduct high-cycle fatigue tests on the test specimen.

[0059] See Figure 5 The present invention also provides a high-cycle fatigue life test method for a thin-walled stamped locking structure, which is implemented by using the above-mentioned thin-walled stamped locking structure for high-cycle fatigue life testing. The test method includes the following steps:

[0060] Step 100: Obtain the first target loading load and the second target loading load of the test specimen;

[0061] The test piece is a cantilever beam structure, which includes a fixed block and a cantilever structure installed on the side of the fixed block and flush with the upper surface of the fixed block. The thickness of the cantilever structure is the same as the thickness of the thin-walled structure of the target locking structure.

[0062] As an alternative approach, step 100 can be implemented based on the following steps:

[0063] Step 110: Simulate two opposite-direction compressive bending processes on the test piece of the test device using numerical simulation to obtain simulation data;

[0064] Specifically, a numerical model of the test device is constructed using finite element software. The numerical model is a finite element model. The simulation process of the cantilever structure bending downward under pressure is as follows: Based on the numerical model, the cantilever structure is loaded according to a first preset displacement to simulate the downward bending process of the cantilever structure under pressure, and the first relationship curve between the plastic strain of the test component and the compressive displacement of the cantilever structure is obtained. The compressive displacement of the cantilever structure is the first preset displacement to which it is loaded. The loading process is as follows: the cantilever structure is slowly pressed downward until the first preset displacement is reached, and the plastic strain force of the test component is measured at this time. The first preset displacement includes multiple preset displacements. The cantilever structure is loaded sequentially to obtain the plastic strain force data corresponding to each first preset displacement. Based on the first preset displacement and the plastic strain force data, curve fitting is performed to obtain the first relationship curve.

[0065] The simulation process of cantilever structure bending upward under compression is as follows: Based on the numerical model, the cantilever structure is subjected to reverse loading according to a second preset displacement to simulate the upward bending process of the cantilever structure under reverse compression, and the second relationship curve between the plastic strain of the test component and the reverse compression displacement of the cantilever structure is obtained. The fitting formula can be any formula with suitable fit.

[0066] The reverse compressive displacement of the cantilever structure is the second preset displacement applied to it. The loading process is as follows: the cantilever structure is slowly pressed upwards until the second preset displacement is reached, and the plastic strain force of the component under test is measured at this point. The second preset displacement includes multiple preset displacements. The cantilever structure is loaded sequentially, and the plastic strain force data corresponding to each second preset displacement is obtained. Based on the second preset displacements and the plastic strain force data, curve fitting is performed to obtain the second relationship curve. The fitting formula can be a quadratic polynomial equation or other formulas with suitable fit.

[0067] In practical applications, since numerical simulation is performed using finite element software, it is only necessary to change the direction of the load applied to the cantilever structure, without changing the direction of the cantilever structure in the test piece.

[0068] Step 120: Determine the first target loading load and the second target loading load to be applied to the test specimen based on the simulation data and the target plastic stress.

[0069] Specifically, the target plastic stress is substituted into the equation corresponding to the first relationship curve to obtain the first target loading load, and the target plastic stress is substituted into the equation corresponding to the second relationship curve to obtain the second target loading load. Both the first and second target loading loads can be either displacement loading or force loading.

[0070] In practical applications, the testing device needs to be assembled before the initial plastic strain loading treatment of the test specimen. Specifically: the test specimen is placed in the fixed slot, and the test specimen and the fixed fixture are fixed by bolts passing through the second through hole and the first through hole, so that the upper surface of the cantilever structure of the test specimen is flush with the upper surface of the fixed slot; the fixed fixture is fixed to the fixed end chuck of the testing machine by the first clamping rod; the loading end head is fixed to the loading end chuck of the testing machine by the second clamping rod, so that the pressure head contacts the upper surface of the cantilever structure and the pressure head is parallel to the cantilever structure, thus completing the installation of the testing device.

[0071] Step 200: Based on the first target loading load, the test piece is subjected to initial plastic strain loading using a test device to obtain the target test piece; the first target loading load brings the cantilever structure close to the fixed block;

[0072] like Figure 6As shown, step 200 specifically includes: controlling the loading end head to move downwards at a uniform speed using the testing machine, causing the cantilever structure to bend downwards under pressure, and the cantilever structure to transfer force to the test component until the displacement reaches the first target loading load; then controlling the loading end head to move upwards at a uniform speed until the pressure head separates from the cantilever structure and stops, thus obtaining the target test piece. The target test piece is then separated from the fixing fixture by removing the bolts, completing the introduction of initial plastic strain.

[0073] Step 300: Based on the second target loading load, the test device is used to conduct a high-cycle fatigue test on the test piece; the second target loading load moves the cantilever structure away from the fixed block.

[0074] Step 300 specifically includes: rotating the target test piece 180° in the testing device so that the upper surface of the cantilever structure is flush with the lower surface of the fixing slot, and fixing the target test piece to the fixing clamp. The testing device after installation is as follows: Figure 7 As shown; the loading end is fixed to the loading end clamp of the testing machine by the clamping rod, and the indenter is kept in contact with and parallel to the lower surface of the cantilever structure of the target test piece; the loading end is controlled by the testing machine to move downward at a uniform speed until the applied displacement reaches the second target loading load, and the loading end is controlled to move upward at a uniform speed until the indenter separates from the cantilever structure, completing one fatigue test; the fatigue test is repeated according to the preset loading frequency, that is, the steps of controlling the loading end to move downward at a uniform speed until the applied displacement reaches the second target loading load, controlling the loading end to move upward at a uniform speed until the indenter separates from the cantilever structure are repeated until the cantilever structure of the test piece fractures, completing the high-cycle fatigue test.

[0075] As can be seen from the above structure and method, this application ensures the validity of test data by introducing a uniformly distributed initial plastic strain. The magnitude of the applied load is obtained more accurately and conveniently through numerical simulation. The initial plastic strain introduction and fatigue load loading can be realized by using a fixed fixture and a loading end, thereby realizing the fatigue life test of the structure after large plastic deformation, providing support for the safety and reliability of the structure in service. Among them, the test piece of this application adopts a cantilever beam structure, which utilizes local stress concentration to enable the test piece to meet large plastic stress without fracture. The cantilever structure can simulate the thin-walled structure of the target locking structure, and accurately reproduce the state of the target locking structure in actual use where one end is fixed and the other end is stressed. Furthermore, the test piece is first subjected to initial plastic strain loading treatment, which can simulate the plastic deformation experienced by the target locking structure during assembly, ensuring the validity of the test data. On this basis, high-cycle fatigue life test is carried out, and the test is more accurate.

[0076] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0077] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A method of testing the high-cycle fatigue life of a thin-walled impact-locked structure, characterized by, include: Obtain the first and second target loading loads on the test specimen; The test piece is a cantilever beam structure, which includes a fixed block and a cantilever structure installed on the side of the fixed block and flush with the upper surface of the fixed block. The thickness of the cantilever structure is the same as the thickness of the thin-walled structure of the target locking structure. Based on the first target loading load, the test piece is subjected to initial plastic strain loading using a test device to obtain the target test piece; the first target loading load brings the cantilever structure closer to the fixed block; Based on the second target loading load, the test device is used to conduct a high-cycle fatigue test on the test piece; the second target loading load moves the cantilever structure away from the fixed block. The test piece also includes an evaluation component; the evaluation component is a structure disposed at the connection between the fixed block and the cantilever structure, the evaluation component is a rounded corner structure, the fixed block and the cantilever structure are integrally formed, the fixed block is a cubic structure, and a first through hole is provided through the fixed block along the height direction of the fixed block; a limit protrusion is provided at the end of the cantilever structure away from the fixed block; The testing apparatus includes a fixing fixture and a loading end. The fixing fixture includes a first clamping rod with external threads and a support structure. The first clamping rod is a cylindrical structure. The longitudinal section of the support structure is L-shaped. The support structure includes a cylindrical base and a semi-cylindrical protrusion disposed at one axial end of the cylindrical base. The semi-cylindrical protrusion is provided with a fixing groove that penetrates the semi-cylindrical protrusion in a direction perpendicular to the axial direction of the semi-cylindrical protrusion. The size of the end face of the fixing groove is the same as the size of the side of the fixing block connected to the cantilever structure. A second through hole is provided in the axial direction of the semi-cylindrical protrusion that penetrates the semi-cylindrical protrusion and communicates with the fixing groove. The diameter of the second through hole is the same as that of the first through hole. The loading end includes a second clamping rod with external threads and a pressure head. The second clamping rod and the pressure head are connected in a T-shape. The second target load is displacement. Based on the second target load, the high-cycle fatigue test of the test piece using the test apparatus includes: In the test apparatus, the target test piece is rotated 180° so that the upper surface of the cantilever structure is flush with the lower surface of the fixing slot, and the target test piece is fixed to the fixing fixture. The loading end head is fixed to the loading end chuck of the testing machine by the second clamping rod, and the pressure head is kept in contact with and parallel to the lower surface of the cantilever structure of the target test piece; The loading end is controlled by the testing machine to move downward at a constant speed until the displacement reaches the second target loading load. Then, the loading end is controlled to move upward at a constant speed until the pressure head separates from the cantilever structure, thus completing one fatigue test. The fatigue test is performed cyclically according to a preset loading frequency until the test piece fractures, thus completing the high-cycle fatigue test.

2. The method of claim 1, wherein the thin-walled impact-locked structure is a thin-walled structure of a vehicle. The process of applying initial plastic strain force to the test specimen using a testing device based on the first target loading load to obtain the target test specimen further includes: The test piece is placed in the fixing slot, and the test piece and the fixing fixture are fixed with bolts so that the upper surface of the cantilever structure of the test piece is flush with the upper surface of the fixing slot. The fixing clamp is fixed to the fixed end chuck of the testing machine by means of the first clamping rod; The loading end is fixed to the loading end clamp of the testing machine by the second clamping rod, so that the pressure head contacts the upper surface of the cantilever structure and the pressure head is parallel to the cantilever structure, thus completing the installation of the testing device.

3. The method of claim 2, wherein the high cycle fatigue life of the thin-walled impact-locked structure is determined by the following equation: ###0001### where N is the number of cycles to failure, σ is the stress amplitude, σy is the yield strength, and σf is the ultimate tensile strength. The first target loading load is displacement. The initial plastic strain loading treatment of the test specimen using a testing device based on the first target loading load to obtain the target test specimen includes: The loading end is controlled by the testing machine to move downward at a constant speed until the displacement reaches the first target loading load. Then, the loading end is controlled to move upward at a constant speed until the pressure head separates from the cantilever structure and stops, thus obtaining the target test piece.

4. The high-cycle fatigue life test method for the thin-walled stamping locking structure according to claim 1, characterized in that, The acquisition of the first and second target loading loads of the test specimen includes: Numerical simulation was used to simulate two opposing compressive bending processes on the test piece of the test device to obtain simulation data; Based on the simulation data and the target plastic stress, the first target loading load and the second target loading load are determined on the test specimen.

5. The high-cycle fatigue life test method for the thin-walled stamping locking structure according to claim 4, characterized in that, The numerical simulation method was used to simulate two opposing compressive bending processes on the test piece of the test device, and the simulation data obtained included: Construct a numerical model of the experimental setup; Based on the numerical model, the cantilever structure is loaded according to the first preset displacement to simulate the downward bending process of the cantilever structure under pressure, and the first relationship curve between the plastic strain of the test component and the compressive displacement of the cantilever structure is obtained. Based on the numerical model, the cantilever structure is subjected to reverse loading according to the second preset displacement to simulate the upward bending process of the cantilever structure under reverse pressure, and a second relationship curve between the plastic strain of the test component and the reverse pressure displacement of the cantilever structure is obtained.

6. The high-cycle fatigue life test method for the thin-walled stamping locking structure according to claim 1, characterized in that, The target locking structure includes an annular cylinder and a thin-walled structure integrally formed with the annular cylinder. The thin-walled structure is annular and is located at one end of the annular cylinder along its axial direction. The inner diameter of the thin-walled structure is the same as the outer diameter of the annular cylinder. A connecting component is provided at the connection between the thin-walled structure and the outer surface of the annular cylinder. The connecting component has a rounded corner structure and is arranged along the circumference of the annular cylinder. The rounded radius of the testing component is the same as the rounded radius of the connecting component.

7. A high-cycle fatigue life testing apparatus for a thin-walled stamped locking structure, applied to the high-cycle fatigue life testing method for the thin-walled stamped locking structure according to any one of claims 1-6, characterized in that, The test apparatus includes at least: a test piece, which is a cantilever beam structure, the cantilever beam structure including a fixed block and a cantilever structure mounted on the side of the fixed block and flush with the upper surface of the fixed block, the thickness of the cantilever structure being the same as the thickness of the thin-walled structure of the target locking structure; The testing apparatus is used to perform initial plastic strain loading on the test specimen and to conduct high-cycle fatigue tests on the test specimen.

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