A high-cycle fatigue acceleration test method

Abstract

The application provides a high-cycle fatigue acceleration test method, and relates to the technical field of high-cycle fatigue test.The high-cycle fatigue acceleration test method comprises the following steps: obtaining a finite element model; wherein the finite element model is constructed according to the three-dimensional structure of a test piece; calculating a pre-load magnitude by using the SN curve of the finite element model and the test piece; pre-testing the test piece according to the pre-load magnitude to obtain a pre-high-cycle fatigue life; wherein the pre-high-cycle fatigue life is the life of the test piece when fatigue damage occurs; obtaining an acceleration load by using the pre-high-cycle fatigue life; and performing a high-cycle fatigue test on the test piece according to the acceleration load, thereby accelerating the test speed of the high-cycle fatigue test and achieving the high-cycle fatigue test in a short time.The high-cycle fatigue acceleration test method can improve the accuracy of the obtained acceleration load, thereby achieving the purpose of improving the test accuracy of the acceleration test.

Description

Technical Field

[0001] This invention relates to the field of high-cycle fatigue testing technology, and more specifically, to a method for accelerated high-cycle fatigue testing. Background Technology

[0002] In mechanical structures, fatigue failure is one of the main failure modes, directly related to operational safety and determining service life. For example, in aircraft structures, due to the complex and variable loads in their operating environment and the repetitive cyclic nature of these loads, the structure is at risk of fatigue failure. Therefore, the strength design of structures needs to specify requirements for fatigue performance to ensure that the structure will not experience fatigue failure within the specified service life or that fatigue failure will not lead to catastrophic consequences. To demonstrate that a structure meets fatigue design requirements, current methods generally involve directly verifying the structure's fatigue performance through relevant fatigue tests, or obtaining the relationship between the fatigue life of the material or a portion of the structure and the load (SN curve) through testing, and then using simulation calculations to show that all structures meet the fatigue requirements.

[0003] One characteristic of fatigue performance is that, under identical loads, testing equipment, and testing conditions, different test specimens will not achieve the same fatigue life; rather, they will exhibit a certain degree of dispersion within a specific range. Another characteristic is that load and fatigue life are often negatively correlated; that is, the smaller the load, the longer the fatigue life. In fatigue testing, the fatigue performance of the test specimen is typically assessed by applying real fatigue loads and conducting a real number of cyclic tests. Therefore, under conditions of low load, high fatigue life, and low load frequency, fatigue failure often takes a very long time to occur. The dispersion of fatigue life in stacked structures makes the failure time even more difficult to estimate, resulting in long and unpredictable testing times.

[0004] Accurately determining the fatigue failure location and fatigue life of a structure with low time cost is a significant and challenging problem. Currently, accelerated testing is an effective method for achieving this goal, utilizing accelerated formulas for load conversion. These formulas can equate "low load - high cycle number" points to "high load - low cycle number" points using the material's S&N curve. However, factors such as potential fatigue dispersion in the material structure and calculation inaccuracies can affect the accuracy of accelerated testing. Therefore, improving the accuracy of accelerated testing is a crucial research direction in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a high-cycle fatigue accelerated testing method that can improve the accuracy of accelerated testing.

[0006] Embodiments of the present invention can be implemented in the following ways:

[0007] A high-cycle fatigue accelerated testing method, the high-cycle fatigue accelerated testing method comprising:

[0008] Obtain a finite element model; wherein the finite element model is constructed based on the three-dimensional structure of the test specimen;

[0009] The preload magnitude is calculated using the finite element model and the SN curve of the test specimen;

[0010] The test specimen is subjected to a pre-test according to the preload level to obtain the pre-high cycle fatigue life; wherein, the pre-high cycle fatigue life is the life of the test specimen when fatigue failure occurs.

[0011] Accelerated loads are obtained by utilizing the pre-high-cycle fatigue life;

[0012] The high-cycle fatigue test is performed on the test specimen under the accelerated load to speed up the high-cycle fatigue test.

[0013] Optionally, the step of calculating the preload magnitude using the finite element model and the SN curve of the test specimen includes:

[0014] The stress level corresponding to the preset test life is determined based on the SN curve;

[0015] The load magnitude corresponding to the stress level is calculated using the finite element model, and this load magnitude is the preload magnitude.

[0016] Optionally, the step of calculating the preload magnitude using the finite element model and the SN curve of the test specimen includes:

[0017] Frequency response analysis was performed using the finite element model to obtain the first stress level under the initial load magnitude.

[0018] The high-cycle fatigue life at the first stress level was obtained based on the SN curve.

[0019] The preload level is calculated based on the initial load level, the high-cycle fatigue life at the first stress level, the preset test life, and the preset acceleration index.

[0020] Optionally, the step of calculating the preload level based on the initial load level, the high-cycle fatigue life at the first stress level, and the preset test life to obtain a preset acceleration index includes:

[0021] The preload magnitude is calculated using a first acceleration formula, which is as follows:

[0022] (L1 / L0) k0=N0 / N1

[0023] Wherein, k0 is the preset acceleration index; L0 is the initial load level; L1 is the preload level; N0 is the high-cycle fatigue life under the first stress level; and N1 is the preset test life.

[0024] Optionally, the step of obtaining accelerated load using the pre-high-cycle fatigue life includes:

[0025] Frequency response analysis was performed using the finite element model to obtain the first stress level under the initial load magnitude.

[0026] The high-cycle fatigue life at the first stress level was obtained based on the SN curve.

[0027] The corrected acceleration index is obtained based on the pre-high-cycle fatigue life, the preload magnitude, the initial load magnitude, and the high-cycle fatigue life at the first stress level.

[0028] The accelerated load is obtained based on the modified acceleration index, the preset test life, the initial load level, and the high-cycle fatigue life under the first stress.

[0029] Optionally, the corrected acceleration exponent is calculated using a second acceleration formula, which is as follows:

[0030] (L1 / L0) k1 =N0 / N2

[0031] Wherein, k1 is the corrected acceleration index; L0 is the initial load level; L1 is the preload level; N0 is the high-cycle fatigue life under the first stress level; and N2 is the pre-high-cycle fatigue life.

[0032] The acceleration load is calculated using a third acceleration formula, which is as follows:

[0033] (L2 / L0) k1 =N0 / N1

[0034] Wherein, L2 is the acceleration load; N1 is the preset test life.

[0035] Optionally, the steps to obtain a finite element model include:

[0036] A model is created based on the three-dimensional structure of the test piece to obtain an initial finite element model;

[0037] The initial finite element model is modified to obtain the final finite element model.

[0038] Optionally, the step of modifying the initial finite element model includes modal correction, the modal correction step including:

[0039] Calculate the natural modes of the initial finite element model in the free state and the natural modes in the installed state to obtain the first natural mode data;

[0040] The natural modes in the free state and the natural modes in the installed state of the test specimen are obtained by using the hammer impact method to obtain the second natural mode data;

[0041] The initial finite element model is corrected based on the first intrinsic modal data and the second intrinsic modal data.

[0042] Optionally, the modification of the initial finite element model includes modifications to the stiffness, mass, and damping parameters of the initial finite element model;

[0043] The stiffness correction of the initial finite element model includes: adjusting the elastic modulus of the material, the stiffness of the connecting elements, and / or setting the boundary conditions;

[0044] The quality correction of the initial finite element model includes: adjusting the density of the material and / or the mass of the connecting elements;

[0045] The correction of the damping parameters of the initial finite element model includes adjusting the damping ratio.

[0046] Optionally, the step of modifying the initial finite element model further includes vibration response correction, wherein the vibration response correction step includes:

[0047] Using the preset load of the test piece as input, frequency response analysis is performed on the initial finite element model to obtain the first response data;

[0048] The test piece is subjected to a vibration response test under a preset load to obtain second response data;

[0049] The structural damping of the initial finite element model is corrected based on the first response data and the second response data.

[0050] Optionally, the preset load of the test specimen is a sinusoidal load spectrum, and the step of conducting a vibration response test on the test specimen according to the preset load includes:

[0051] A frequency sweep test is performed on the test piece to obtain the inherent frequency of the test piece in its current installation state;

[0052] The test specimen is excited using the natural frequency as the excitation frequency and the load at the excitation frequency as the input to obtain the second response data.

[0053] Optionally, the step of correcting the initial finite element model before the vibration response correction further includes modal correction; after the step of performing a frequency sweep test on the test specimen to obtain the natural frequencies of the test specimen in the current installation state, it further includes:

[0054] The natural frequency obtained by the frequency sweep test is compared with the natural frequency of the test piece in the installed state obtained in the modal correction step to obtain the deviation between the two.

[0055] If the deviation is within the preset range, it indicates that the current installation state is consistent with the installation state in the modal correction step, and the natural frequency obtained by the frequency sweep test is used as the excitation frequency.

[0056] If the deviation is outside the preset range, it indicates that the current installation state is inconsistent with the installation state in the modal correction step. After adjusting the state of the test piece, the frequency sweep test is performed again until the deviation is within the preset range.

[0057] Optionally, the preset load of the test specimen is a random load spectrum, and the step of conducting a vibration response test on the test specimen according to the preset load includes:

[0058] The test piece is excited with the frequency band range and amplitude specified by the preset load to obtain the second response data.

[0059] The beneficial effects of the high-cycle fatigue accelerated testing method provided by the embodiments of the present invention include:

[0060] This invention provides a method for accelerated high-cycle fatigue testing, comprising: acquiring a finite element model; wherein the finite element model is constructed based on the three-dimensional structure of the test piece; calculating the preload magnitude using the SN curve of the finite element model and the test piece; performing a pre-test on the test piece according to the preload magnitude to obtain a pre-high-cycle fatigue life; wherein the pre-high-cycle fatigue life is the life of the test piece when fatigue failure occurs; obtaining an accelerated load using the pre-high-cycle fatigue life; and performing a high-cycle fatigue test on the test piece according to the accelerated load, thereby accelerating the high-cycle fatigue test speed and achieving completion of the high-cycle fatigue test in a shorter time. The accelerated high-cycle fatigue testing method provided by this invention can improve the accuracy of the obtained accelerated load, thereby achieving the goal of improving the accuracy of the accelerated test. Attached Figure Description

[0061] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related properties or features may have the same or similar reference numerals.

[0062] Figure 1 A flowchart illustrating the steps of a high-cycle fatigue accelerated testing method according to one aspect of the present invention is shown.

[0063] Figure 2 A flowchart of a high-cycle fatigue accelerated testing method according to one aspect of the present invention is shown. Detailed Implementation

[0064] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0065] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," "outer," or "vertical" appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0066] At the same time, it should be noted that the terms "first" and "second" are used only for distinguishing descriptions and should not be interpreted as indicating or implying relative importance.

[0067] In the description of this invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an integral connection, or a detachable connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components, etc. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] The following is an explanation of the terms that may be mentioned in the embodiments of the present invention:

[0069] Fatigue: The change in properties of metallic materials under repeated stress or strain.

[0070] High-cycle fatigue: When the cyclic stress level is low, elastic strain plays a dominant role, resulting in a longer fatigue life, which is called high-cycle fatigue.

[0071] Fatigue strength: The load value at which a structure fails due to fatigue.

[0072] Fatigue life: The number of load cycles required for a structure to fail due to fatigue.

[0073] SN curve: A curve reflecting the relationship between fatigue stress S and fatigue life N.

[0074] Acceleration index: Used to quantitatively characterize the level of change of the experimental magnitude designed to shorten the experimental cycle compared to the original magnitude.

[0075] First Implementation Method

[0076] Figure 1 This is a flowchart illustrating the steps of the high-cycle fatigue accelerated testing method provided in this embodiment. Figure 2 This is a flowchart of the high-cycle fatigue accelerated testing method provided in this embodiment. Please refer to the attached document. Figure 1 and Figure 2 This embodiment provides a high-cycle fatigue accelerated testing method, which can quickly and accurately perform high-cycle fatigue testing on test pieces. In this embodiment, the test piece is the air intake bulkhead in the nacelle of an aero-engine. It is understood that in other embodiments, this high-cycle fatigue accelerated testing method can also be used to perform high-cycle fatigue testing on other metal components.

[0077] Specifically, the high-cycle fatigue accelerated testing method provided in this embodiment includes:

[0078] S01: Obtain the finite element model.

[0079] The finite element model is constructed based on the three-dimensional structure of the test piece to be subjected to high-cycle fatigue testing.

[0080] High-cycle fatigue is generally caused by vibration. Vibration refers to the cyclic motion of a structure, which also includes stress cycles; therefore, structural vibration often leads to fatigue failure. Solving for or obtaining the vibration response of the structure, and combining it with the SN curve, to obtain the high-cycle fatigue life of the structure is an effective technical approach. With the rapid development of computers, commercial computing software can perform calculations on increasingly large datasets, making the finite element method (FEM) widely used. Therefore, using the FEM to solve for the vibration response of a model has become a commonly used calculation method. To improve the accuracy of the calculation results, this invention also modifies the finite element model when obtaining it. Specifically, the steps for obtaining the finite element model include:

[0081] S11: Model the three-dimensional structure of the test piece to obtain the initial finite element model.

[0082] Specifically, a model is constructed based on the three-dimensional structure of the test piece, and the constructed model is meshed and boundary conditions are established to ensure that the initial finite element model can be used for subsequent simulation calculations.

[0083] S12: Modify the initial finite element model to obtain the final finite element model.

[0084] By modifying the initial finite element model and using the modified model as the finite element model for subsequent simulation calculations, the accuracy of the calculations can be improved.

[0085] In this embodiment, the step of correcting the initial finite element model includes modal correction, which includes:

[0086] S131: Perform modal calculations.

[0087] The natural modes in the free state and the natural modes in the installed state of the initial finite element model are calculated to obtain the first natural mode data.

[0088] S132: Conduct modal testing.

[0089] Modal tests were conducted on the test specimen using the hammer impact method to obtain the natural modes of the test specimen in the free state and the natural modes in the installed state, thereby obtaining the second natural mode data.

[0090] S133: Modal correction of the initial finite element model is performed using the first and second intrinsic modal data.

[0091] Specifically, by comparing the first intrinsic modal data and the second intrinsic modal data, the initial finite element model is corrected so that the calculated first intrinsic modal data of the corrected model are closer to the second intrinsic modal data, thereby improving accuracy.

[0092] Furthermore, the modifications made to the initial finite element model include:

[0093] Stiffness Correction: Stiffness correction can be achieved by adjusting the elastic model of the model material, the stiffness of connecting elements, and / or the boundary conditions. Specifically, stiffness correction can be achieved by adjusting one or more of the following: the elastic model of the model material, the stiffness of connecting elements, and the boundary conditions. Connecting elements refer to components such as rivets and bolts. For example, these can be rivets and bolts used to connect the test specimen during installation, or rivets and bolts used to connect different parts within the test specimen. In the finite element model, this component can be simulated using spring elements and mass points.

[0094] Mass Correction: Mass correction can be achieved by adjusting the density of the model material and / or the mass of the connecting elements. Specifically, it can be achieved by adjusting both the density of the model material and the mass of the connecting elements simultaneously, or by adjusting only one of the density of the model material and the mass of the connecting elements.

[0095] Damping parameter correction: Damping parameter correction can be achieved by setting the damping ratio of the model.

[0096] In this embodiment, the step of correcting the initial finite element model further includes vibration response correction, which includes:

[0097] S141: Frequency response analysis.

[0098] Using the preset load of the test specimen as input, frequency response analysis is performed on the initial finite element model to obtain the first response data.

[0099] Specifically, the preset load can be obtained by conducting load tests on the test piece, by consulting materials such as manuals, or by obtaining it based on past experience.

[0100] S142: Vibration response test.

[0101] Vibration response tests are conducted on the test specimen under a preset load to obtain second response data.

[0102] Specifically, when conducting vibration response tests on test specimens, the vibration response tests must be performed according to the type of preset load.

[0103] In some embodiments, the preset load is a sinusoidal load spectrum, and the steps of conducting a vibration response test on the test specimen according to the preset load include:

[0104] A frequency sweep test is performed on the test specimen to obtain its natural frequency in the current installation state; this natural frequency is used as the excitation frequency, and the test specimen is excited according to the load under the excitation frequency as input to obtain the second response data.

[0105] Furthermore, since the vibration response test requires subsequent excitation operations based on the natural frequency obtained from the frequency sweep test, and the natural frequency in the installation state needs to be obtained by hammering in step S132, in order to ensure that the current installation state of the test piece during the frequency sweep test is consistent with the installation state of the test piece in step S132, after the step of performing a frequency sweep test on the test piece to obtain the natural frequency of the test piece in the current installation state, the vibration response test in this manner also includes:

[0106] The natural frequencies obtained from the frequency sweep test are compared with the natural frequencies of the test specimen in the installed state obtained in the modal correction step to obtain the deviation between the two. The natural frequencies of the test specimen in the installed state obtained in the modal correction step are the same as the natural frequencies in the installed state obtained when performing step S132.

[0107] If the deviation is within the preset range, it indicates that the installation state of the test piece (i.e., the current installation state mentioned above) is consistent with the installation state in the modal correction step when the frequency sweep test is performed. At this time, the natural frequency obtained by the frequency sweep test can be used as the excitation frequency to obtain the second response data.

[0108] If the deviation is outside the preset range, it indicates that the installation state of the test piece (i.e., the current installation state mentioned above) is inconsistent with the installation state in the modal correction step when performing the frequency sweep test. At this time, the state of the test piece needs to be adjusted (i.e., the current installation state needs to be changed) and the frequency sweep test should be performed again until the deviation is within the preset range.

[0109] Optionally, the preset range includes, but is not limited to, setting it to 1% of the inherent mode in the installation state during the modal correction step. It is understood that in some other embodiments, the specific value of the preset range can also be set as needed.

[0110] In some embodiments, the preset load on the test specimen is a random load spectrum, and the steps of conducting a vibration response test on the test specimen according to the preset load include:

[0111] The test specimen is excited with a preset load and a specified frequency band and amplitude to obtain the second response data.

[0112] S143: Correct the damping of the initial finite element model based on the first response data and the second response data.

[0113] Specifically, by comparing the first response data and the second response data, the initial finite element model is corrected so that the first response data calculated by the corrected model is closer to the second response data, thereby improving accuracy.

[0114] Thus, the initial finite element model, after modal correction and vibration response correction, becomes the finite element model, which can be used to perform subsequent steps. It should be noted that in this embodiment, the initial finite element model underwent both modal correction and vibration response correction. It is understood that in other embodiments, modal correction or vibration response correction may be performed only, depending on the requirements.

[0115] S02: Calculate the preload level using the finite element model and the SN curve of the test piece.

[0116] The SN curve of the test specimen can be obtained according to conventional SN curve acquisition methods, or it can be obtained according to existing literature. The acquisition process will not be described in the embodiments of the present invention.

[0117] The steps for calculating the preload magnitude using a finite element model and the SN curve of the test specimen include:

[0118] S21: Use the finite element model to perform frequency response analysis to obtain the first stress level under the initial load magnitude.

[0119] Using the initial load magnitude L0 as input, frequency response analysis is performed on the finite element model to obtain the first stress level S0. The initial load magnitude is the initial load magnitude among the preset loads used in the above steps.

[0120] S22: High-cycle fatigue life at the first stress level is obtained using the SN curve.

[0121] The SN curve is the curve corresponding to the life N and the stress level S. Thus, given a first stress level S0, the high-cycle fatigue life N0 corresponding to the first stress level S0 can be obtained from the SN curve.

[0122] S23: The preload level is calculated based on the initial load level, the high-cycle fatigue life at the first stress level, the preset test life, and the preset acceleration index.

[0123] Specifically, the preset test life can be set according to the test requirements or the application requirements of the test specimen. For example, it can be set to a life of 10 million cycles or 20 million cycles. The preset acceleration index can generally be set to 3 to 5, such as 3, 4 or 5, or other values.

[0124] The process of calculating the preload magnitude based on the initial load magnitude, high-cycle fatigue life at the first stress level, preset test life, and preset acceleration index can be obtained through the first acceleration formula, which is as follows:

[0125] (L1 / L0) k0 =N0 / N1

[0126] Where k0 is the preset acceleration index; L0 is the initial load level; L1 is the preload level; N0 is the high-cycle fatigue life under the first stress level; and N1 is the preset test life.

[0127] S03: Preliminary test.

[0128] A pre-test is conducted on the test specimen according to a preload level L1 to obtain the pre-high-cycle fatigue life, which is the life at which the test specimen will fail due to fatigue. Specifically, a fatigue test is conducted on the test specimen by applying a preset load level L1. The test is stopped and the test time is recorded when the test specimen fails due to fatigue, thereby obtaining the high-cycle fatigue life, which is the pre-high-cycle fatigue life N2.

[0129] S04: Accelerated load is obtained by utilizing the pre-high cycle fatigue life.

[0130] Using the pre-high-cycle fatigue life N2 obtained in step S03, the accelerated load can be calculated. Specifically, the steps for calculating the accelerated load include:

[0131] S41: The corrected acceleration index is obtained based on the pre-high-cycle fatigue life, the preload magnitude, the initial load magnitude, and the high-cycle fatigue life under the first stress level.

[0132] In this embodiment, a second acceleration formula is used to calculate the corrected acceleration index. This second acceleration formula is obtained by substituting the pre-high-cycle fatigue life N2 calculated in step S03 into the first acceleration formula and replacing N1 in the first acceleration formula. Specifically, the second acceleration formula is:

[0133] (L1 / L0) k1 =N0 / N2

[0134] Where k1 is the corrected acceleration index; L0 is the initial load level; L1 is the preload level; N0 is the high-cycle fatigue life under the first stress level; and N2 is the pre-high-cycle fatigue life.

[0135] Since N2 replaces N1 in the second acceleration formula, the acceleration index K can be corrected to obtain the corrected acceleration index k1, while other parameters remain unchanged.

[0136] S42: The accelerated load is obtained based on the modified acceleration index, the preset test life, the initial load level, and the high-cycle fatigue life under the first stress.

[0137] In this embodiment, the acceleration load is calculated using a third acceleration formula. This third acceleration formula is obtained by substituting the corrected acceleration index k1 calculated in step S41 into the first acceleration formula and replacing the k1 obtained in the first acceleration formula. Specifically, the third acceleration formula is:

[0138] (L2 / L0) k1 =N0 / N1

[0139] Where k1 is the corrected acceleration index; L0 is the initial load level; L2 is the accelerated load; N0 is the high-cycle fatigue life at the first stress level; and N1 is the preset test life.

[0140] Since k1 replaces k0 in the third acceleration formula, the load corresponding to the preset test life is corrected when other parameters remain unchanged. The corrected load is the acceleration load L2. The acceleration load L2 obtained in this way is more accurate than the preload magnitude L1 calculated in step S02. This helps to avoid the adverse effects caused by factors such as fatigue dispersion of the structure and inaccuracy of calculation, thereby improving the accuracy of calculation.

[0141] S05: Perform high-cycle fatigue tests on the test specimens based on accelerated loads.

[0142] Using the acceleration load L2 calculated in step S04 as input, a high-cycle fatigue test is performed on the test piece, thereby accurately and quickly obtaining the high-cycle fatigue life of the test piece and assessing whether the test piece can meet the high-cycle fatigue requirements.

[0143] Second Implementation Method

[0144] The present invention also provides a high-cycle fatigue accelerated test method, which has basically the same steps as the high-cycle fatigue accelerated test method provided in the first embodiment above. The similarities will not be repeated. The difference is in the step of calculating the preload level using the finite element model and the SN curve of the test piece.

[0145] Specifically, in this embodiment, the steps of calculating the preload magnitude using the finite element model and the SN curve of the test specimen include:

[0146] S24: Determine the stress level corresponding to the preset test life based on the SN curve.

[0147] After the preset test life, the stress level S1 corresponding to the preset test life N1 can be obtained from the SN curve.

[0148] S25: Calculate the load level corresponding to the stress level using a finite element model.

[0149] The load magnitude corresponding to stress level S1 is calculated by using a finite element model for simulation calculation. This load magnitude corresponding to stress level S1 is used as the preload magnitude L1 applied in the subsequent pre-test.

[0150] In this embodiment, the preload level is calculated using a finite element model, without the need for a preset acceleration index, and therefore without the need for the first acceleration formula.

[0151] Since the subsequent calculation process of step S04 uses the second acceleration formula and the third acceleration formula, the parameter N0 required in the second acceleration formula and the third acceleration formula still needs to be calculated. The step of calculating N0 (i.e., steps S21 and S22 in the first embodiment above) can be performed before using the second acceleration formula and the third acceleration formula. For example, the step of calculating N0 can be performed after step S03 and before step S41.

[0152] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-cycle fatigue accelerated testing method, characterized in that, The high-cycle fatigue accelerated testing method includes: Obtain a finite element model; wherein the finite element model is constructed based on the three-dimensional structure of the test specimen; The preload magnitude is calculated using the finite element model and the SN curve of the test specimen; The test specimen is subjected to a pre-test according to the preload level to obtain the pre-high cycle fatigue life; wherein, the pre-high cycle fatigue life is the life of the test specimen when fatigue failure occurs. Accelerated loads are obtained by utilizing the pre-high-cycle fatigue life; The high-cycle fatigue test is performed on the test specimen under the accelerated load to speed up the high-cycle fatigue test.

2. The high-cycle fatigue accelerated testing method according to claim 1, characterized in that, The steps for calculating the preload magnitude using the finite element model and the SN curve of the test specimen include: The stress level corresponding to the preset test life is determined based on the SN curve; The load magnitude corresponding to the stress level is calculated using the finite element model, and this load magnitude is the preload magnitude.

3. The high-cycle fatigue accelerated testing method according to claim 1, characterized in that, The steps for calculating the preload magnitude using the finite element model and the SN curve of the test specimen include: Frequency response analysis was performed using the finite element model to obtain the first stress level under the initial load magnitude. The high-cycle fatigue life at the first stress level was obtained based on the SN curve. The preload level is calculated based on the initial load level, the high-cycle fatigue life at the first stress level, the preset test life, and the preset acceleration index.

4. The high-cycle fatigue accelerated testing method according to claim 3, characterized in that, The steps for calculating the preload level based on the initial load level, the high-cycle fatigue life at the first stress level, and the preset test life to obtain a preset acceleration index include: The preload magnitude is calculated using a first acceleration formula, which is as follows: (L1 / L0) k0 =N0 / N1 Wherein, k0 is the preset acceleration index; L0 is the initial load level; L1 is the preload level; N0 is the high-cycle fatigue life under the first stress level; and N1 is the preset test life.

5. The high-cycle fatigue accelerated testing method according to claim 1, characterized in that, The steps for obtaining accelerated loads using the pre-high-cycle fatigue life include: Frequency response analysis was performed using the finite element model to obtain the first stress level under the initial load magnitude. The high-cycle fatigue life at the first stress level was obtained based on the SN curve. The corrected acceleration index is obtained based on the pre-high-cycle fatigue life, the preload magnitude, the initial load magnitude, and the high-cycle fatigue life at the first stress level. The accelerated load is obtained based on the modified acceleration index, the preset test life, the initial load level, and the high-cycle fatigue life under the first stress.

6. The high-cycle fatigue accelerated testing method according to claim 5, characterized in that, The corrected acceleration index is calculated using a second acceleration formula, which is as follows: (L1 / L0) k1 =N0 / N2 Wherein, k1 is the corrected acceleration index; L0 is the initial load level; L1 is the preload level; N0 is the high-cycle fatigue life under the first stress level; and N2 is the pre-high-cycle fatigue life. The acceleration load is calculated using a third acceleration formula, which is as follows: (L2 / L0) k1 N0 / N1 Wherein, L2 is the acceleration load; N1 is the preset test life.

7. The high-cycle fatigue accelerated testing method according to claim 1, characterized in that, The steps to obtain a finite element model include: A model is created based on the three-dimensional structure of the test piece to obtain an initial finite element model; The initial finite element model is modified to obtain the final finite element model.

8. The high-cycle fatigue accelerated testing method according to claim 7, characterized in that, The steps for modifying the initial finite element model include modal correction, which includes: Calculate the natural modes of the initial finite element model in the free state and the natural modes in the installed state to obtain the first natural mode data; The natural modes in the free state and the natural modes in the installed state of the test specimen are obtained by using the hammer impact method to obtain the second natural mode data; The initial finite element model is corrected based on the first intrinsic modal data and the second intrinsic modal data.

9. The high-cycle fatigue accelerated testing method according to claim 8, characterized in that, The corrections made to the initial finite element model include corrections to the stiffness, mass, and damping parameters of the initial finite element model; The stiffness correction of the initial finite element model includes: adjusting the elastic modulus of the material, the stiffness of the connecting elements, and / or setting the boundary conditions; The quality correction of the initial finite element model includes: adjusting the density of the material and / or the mass of the connecting elements; The correction of the damping parameters of the initial finite element model includes adjusting the damping ratio.

10. The high-cycle fatigue accelerated testing method according to claim 7, characterized in that, The step of correcting the initial finite element model further includes vibration response correction, which includes: Using the preset load of the test piece as input, frequency response analysis is performed on the initial finite element model to obtain the first response data; The test piece is subjected to a vibration response test under a preset load to obtain second response data; The structural damping of the initial finite element model is corrected based on the first response data and the second response data.

11. The high-cycle fatigue accelerated testing method according to claim 10, characterized in that, The preset load of the test specimen is a sinusoidal load spectrum. The steps for conducting a vibration response test on the test specimen based on the preset load include: A frequency sweep test is performed on the test piece to obtain the inherent frequency of the test piece in its current installation state; The test specimen is excited using the natural frequency as the excitation frequency and the load at the excitation frequency as the input to obtain the second response data.

12. The high-cycle fatigue accelerated testing method according to claim 11, characterized in that, The step of correcting the initial finite element model before the vibration response correction also includes modal correction; After performing a frequency sweep test on the test specimen to obtain the natural frequency of the test specimen in the current installation state, the method further includes: The natural frequency obtained by the frequency sweep test is compared with the natural frequency of the test piece in the installed state obtained in the modal correction step to obtain the deviation between the two. If the deviation is within the preset range, it indicates that the current installation state is consistent with the installation state in the modal correction step, and the natural frequency obtained by the frequency sweep test is used as the excitation frequency. If the deviation is outside the preset range, it indicates that the current installation state is inconsistent with the installation state in the modal correction step. After adjusting the state of the test piece, the frequency sweep test is performed again until the deviation is within the preset range.

13. The high-cycle fatigue accelerated testing method according to claim 10, characterized in that, The preset load of the test specimen is a random load spectrum. The steps of conducting a vibration response test on the test specimen according to the preset load include: The test piece is excited with the frequency band range and amplitude specified by the preset load to obtain the second response data.

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