Method and device for evaluating multi-axle fatigue life of welding structure of intermediate shaft of gearbox
By constructing a finite element model and using a multi-axis fatigue assessment method, the fatigue life of the intermediate shaft welded structure of the gearbox can be accurately predicted, solving the problem of inaccurate prediction in the existing technology and improving the reliability and life of the gearbox of heavy-duty vehicles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGAN UNIV
- Filing Date
- 2022-09-27
- Publication Date
- 2026-05-22
AI Technical Summary
Existing technologies have problems with inaccurate prediction when evaluating the multiaxial fatigue life of welded intermediate shaft structures in gearboxes, especially under complex multiaxial stress conditions, making it difficult to accurately predict their fatigue life.
A finite element model was constructed, and boundary conditions and load spectrum loads were added. The fatigue cycle number and fatigue life of the weld structure were determined by the multiaxial fatigue assessment method. The fatigue life assessment model of the intermediate shaft weld structure was established by the multiaxial structural stress method, including plotting the load path curve, determining the effective stress range and non-proportionality, and calculating the equivalent stress range and fatigue cycle number.
Accurate prediction of multi-axis fatigue life of the intermediate shaft welded structure of the gearbox was achieved, which improved the reliability and service life of the gearbox transmission system of heavy-duty vehicles and optimized the structural design of welded components.
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Figure CN116306065B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of fatigue life prediction of welded structures, and more specifically, to a method and apparatus for multi-axis fatigue life assessment of a welded structure of a gearbox intermediate shaft. Background Technology
[0002] Heavy-duty vehicles operate in harsh environments, and the randomness of loads and complexity of road conditions during actual operation place their internal structures under complex stress states. As a key component of the transmission system in heavy-duty vehicles, the gearbox needs to meet high speed ratios and high torque requirements, which places high demands on the reliability of its internal components. In practice, the welded structure of the gearbox intermediate shaft bears multiaxial stress, with fatigue failure being the primary failure mode. This severely restricts further improvements in the power density of dual intermediate shaft transmissions. Therefore, conducting multiaxial fatigue life assessments of the intermediate shaft welded structure is of significant reference value for improving the reliability of heavy-duty vehicle gearbox transmission systems, extending their service life, and optimizing the structure of welded components.
[0003] Currently, multiaxial fatigue failure assessment generally builds upon uniaxial fatigue assessment by equating the complex multiaxial stress state to a single scalar value, and then using relevant criteria for multiaxial fatigue life assessment to predict the fatigue life of the structure. However, this method suffers from inaccurate life prediction. Summary of the Invention
[0004] To overcome at least one deficiency in the prior art, this application provides a method and apparatus for evaluating the multi-axis fatigue life of a gearbox intermediate shaft welded structure.
[0005] In a first aspect, embodiments of this application provide a method for evaluating the multi-axis fatigue life of a welded structure for a gearbox intermediate shaft, including:
[0006] Construct a finite element model of the welded structure; add boundary conditions to the finite element model, including load spectrum loads applied to the welded structure and intermediate shaft constraint conditions, the load spectrum loads include multiple gear loads of the gearbox;
[0007] For each load setting, determine the number of fatigue cycles for the weld structure under each load setting, including:
[0008] Draw the load path curve based on the finite element model;
[0009] The cyclic path and effective stress range for each half-cycle are determined based on the load path curve.
[0010] The non-proportional degree for each half-cycle is determined based on the cyclic path for each half-cycle.
[0011] The equivalent stress range for each half-cycle is determined based on the effective stress range and non-proportional coefficient for each half-cycle.
[0012] The fatigue cycle number of the weld structure is determined based on the equivalent stress range and SN curve under each half-cycle. The fatigue cycle number of the weld structure includes the fatigue cycle number of the weld structure under each half-cycle.
[0013] The fatigue life of the welded structure is determined by the number of fatigue cycles of the welded structure under each set of load levels.
[0014] In one embodiment, plotting the load path curve based on the finite element model includes:
[0015] The stress of the welded structure is obtained based on the finite element model;
[0016] Determine the normal structural stress and in-plane shear structural stress at the weld of the welded structure based on the stress of the welded structure.
[0017] Load path curves are plotted based on the normal structural stress and in-plane shear structural stress at the weld.
[0018] In one embodiment, determining the fatigue life of the welded structure based on the number of fatigue cycles of the welded structure under each set of load increments includes:
[0019] The degree of damage to the weld structure is determined by the number of fatigue cycles of the weld structure under each half-cycle of each gear load.
[0020] The fatigue life of a welded structure is determined based on the degree of damage to the weld structure.
[0021] In one embodiment, the degree of weld structure damage is determined based on the number of fatigue cycles of the weld structure under each half-cycle of each load setting, including:
[0022]
[0023] Where D represents the degree of damage to the weld structure, and N ij Let n be the number of fatigue cycles of the weld structure under the k-th half-cycle of the i-th gear load. i denoted as the fatigue cycle number of the weld structure under the i-th load group obtained from the bench fatigue accelerated test, where M is the number of load groups and P is the number of half cycles of the i-th load group.
[0024] In one embodiment, the non-proportional degree for each half-cycle is determined based on the cyclic path for each half-cycle, using the following formula:
[0025]
[0026] Among them, g NPk The nonproportional degree in the k-th half-cycle, Let (r, θ) be the cyclic path in the kth half-cycle. The polar coordinates of a point in R k For loop path The distance between the two endpoints is half.
[0027] In one embodiment, the equivalent stress range for each half-cycle is determined based on the effective stress range and non-proportional coefficient for each half-cycle, using the following formula:
[0028] Δσ NPk =Δσ ek (1+αg NPk )
[0029] Where, Δσ NPk Let Δσ be the range of equivalent stress during the k-th half-cycle. ek Let g be the effective stress range in the kth half-cycle. NPk α represents the nonproportional degree in the kth half-cycle, and α is the material sensitivity coefficient.
[0030] In one embodiment, the number of fatigue cycles of the weld structure is determined based on the equivalent stress range and the SN curve for each half-cycle, using the following formula:
[0031]
[0032] Where, N k C represents the number of fatigue cycles of the weld structure in the kth half-cycle. d ΔS is a constant, h is a constant; NPk The range of multiaxial equivalent structural stresses under the k-th half-cycle:
[0033]
[0034] Where, Δσ NPk Let t be the equivalent stress range under the kth half-cycle, t be the thickness of the base plate of the weld structure, m be the long crack propagation index, and I(r) be the dimensionless function of the bending load ratio r.
[0035] Secondly, embodiments of this application provide a multi-axis fatigue life assessment device for a gearbox intermediate shaft welded structure, comprising:
[0036] The finite element model building module is used to build the finite element model of the welded structure. Boundary conditions are added to the finite element model, including the load spectrum load applied to the welded structure and the intermediate shaft constraint conditions. The load spectrum load includes multiple gear loads of the gearbox.
[0037] The fatigue cycle determination module determines the number of fatigue cycles for the weld structure under each load setting.
[0038] The fatigue cycle number determination module is also used for: plotting load path curves based on the finite element model; determining the cycle path and effective stress range for each half-cycle based on the load path curves; determining the non-proportional stress for each half-cycle based on the cycle path for each half-cycle; determining the equivalent stress range for each half-cycle based on the effective stress range and non-proportional stress for each half-cycle; and determining the fatigue cycle number of the weld structure based on the equivalent stress range for each half-cycle and the SN curve. The fatigue cycle number of the weld structure includes the fatigue cycle number of the weld structure for each half-cycle.
[0039] The fatigue life determination module determines the fatigue life of the welded structure based on the number of fatigue cycles under each gear load. Thirdly, embodiments of this application provide a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the aforementioned multi-axis fatigue life evaluation method for the intermediate shaft welded structure of a gearbox.
[0040] Thirdly, embodiments of this application provide a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the above-described method for evaluating the multi-axis fatigue life of the intermediate shaft welded structure of a gearbox.
[0041] Fourthly, embodiments of this application provide a computer program product, including a computer program / instruction, which, when executed by a processor, implements the aforementioned method for evaluating the multi-axis fatigue life of the intermediate shaft welded structure of a gearbox.
[0042] Compared with the prior art, this application has the following beneficial effects: The multiaxial fatigue life assessment method for the intermediate shaft welded structure of the gearbox in this application constructs a finite element model of the welded structure, uses the finite element model to determine the multiaxial stress components and load paths at the critical points of each gear; for the load paths corresponding to each gear, it determines the equivalent stress range considering the load paths of each gear; based on the equivalent stress range considering the load paths of each gear and the main SN curve, it determines the fatigue cycle number and fatigue damage degree of each gear of the welded structure, and finally determines the fatigue life of the welded structure. By using the multiaxial structural stress method to establish a multiaxial fatigue life assessment model for the intermediate shaft welded structure and performing fatigue life analysis, the fatigue life of the structure can be predicted more accurately. Attached Figure Description
[0043] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings, which, together with the detailed description below, are incorporated in and form part of this specification. In the drawings:
[0044] Figure 1 A flowchart illustrating a method for evaluating the multi-axis fatigue life of a gearbox intermediate shaft welded structure according to an embodiment of this application is shown.
[0045] Figure 2 A schematic diagram of the welded structure and the constructed finite element model according to an embodiment of this application is shown;
[0046] Figure 3 A schematic diagram showing multiple sets of loads added to a finite element model of a welded structure according to an embodiment of this application is shown.
[0047] Figure 4 A schematic diagram of the finite element model of the intermediate shaft constraint welded structure according to an embodiment of this application is shown;
[0048] Figure 5 A schematic diagram of the load path curve PQ plotted from a finite element model according to an embodiment of this application is shown;
[0049] Figure 6 The loop path PQ under the first half-cycle according to an embodiment of this application is shown;
[0050] Figure 7 The loop path RR* under the second half-cycle according to an embodiment of this application is shown;
[0051] Figure 8 A plot of multiaxial fatigue test data according to an embodiment of this application is shown;
[0052] Figure 9 The normal structural stress σ according to an embodiment of this application is shown. s A schematic diagram of in-plane shear stress;
[0053] Figure 10 A schematic diagram of the load path curve AB according to an embodiment of this application is shown;
[0054] Figure 11 A schematic diagram of the loop path AB in the first half-cycle according to an embodiment of this application is shown;
[0055] Figure 12 A schematic diagram of the loop path BA under the second half-cycle according to an embodiment of this application is shown;
[0056] Figure 13 A structural block diagram of a multi-axis fatigue life assessment device for a gearbox intermediate shaft welded structure according to an embodiment of this application is shown. Detailed Implementation
[0057] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of the actual embodiments are described in the specification. However, it should be understood that many embodiment-specific decisions can be made in the development of any such actual embodiment to achieve the developer’s specific objectives, and these decisions may vary as the embodiments differ.
[0058] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the device structure closely related to the solution according to this application is shown in the accompanying drawings, while other details that are not closely related to this application are omitted.
[0059] It should be understood that this application is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, embodiments may be combined with each other, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in one embodiment, where feasible.
[0060] Figure 1 A flowchart illustrating a multi-axis fatigue life assessment method for a gearbox intermediate shaft welded structure according to an embodiment of this application is shown. The method begins in step S110, constructing a finite element model of the welded structure; Figure 2 A schematic diagram of the welded structure and its finite element model is shown, where the left image represents the welded structure and the right image represents the finite element model. Boundary conditions are added to the finite element model, including load spectrum loads applied to the welded structure and intermediate shaft constraints. The load spectrum includes the loads of the gearbox at different gear positions. Here, multiple sets of gear loads measured by a dynamometer (or actual load) can be uniformly applied along the tooth width to the point where the tooth surface coincides with the pitch circle, such as... Figure 3 As shown.
[0061] Intermediate shaft constraint conditions could be, for example, restricting the translational degrees of freedom in the X and Z directions of the intermediate shaft and bearing assembly surfaces to prevent radial runout of the intermediate shaft structure, while retaining its rotational degree of freedom in the Y direction to simulate the rotation of the intermediate shaft within the bearing; restricting the translational degree of freedom in the Y direction of the intermediate shaft end face to prevent axial runout of the intermediate shaft, such as... Figure 4 As shown.
[0062] Then, in step S120, for each set of load increments, the number of fatigue cycles of the weld structure under each set of load increments is determined, including:
[0063] Plot the load path curve based on the finite element model. Figure 5 A schematic diagram of the load path curve plotted based on the finite element model is shown.
[0064] The cyclic path and effective stress range for each half-cycle are determined based on the load path curve. Here, the multi-axis cycle counting (PDMR) method can be used to process the load path curve to obtain the cyclic path and effective stress range for each half-cycle. Figure 5 Taking the load path curve shown as an example, the cyclic path and effective stress range under two half cycles are obtained using the multi-axis cycle counting (PDMR) method. The specific steps are as follows:
[0065] a: Search the entire stress plane to find the effective stress range Δσ between any two points on the load path curve. e1 Here, the straight-line distance is from point P to point Q, such as... Figure 6 As shown.
[0066] b: In order to ensure that the instantaneous static distance from point P to point Q increases monotonically at any time, a virtual load path (RR*) is set. R is called the turning point and R* is called the design turning point.
[0067] c: Statistical effective stress range Δσ e (1) The path length corresponding to (the straight-line distance from point P to point Q), i.e., path PRR * The length of -Q is: Among them, RR * This is a virtual path, which can be used to navigate from R to R. * The distance is used for evaluation, and the rest are the actual paths.
[0068] By removing the paths that have already been analyzed and repeating steps a through c, the second effective stress range Δσ can be determined. e2 (R to R) * (straight-line distance), such as Figure 7 As shown. The corresponding path length is calculated as follows:
[0069] The cyclic paths and effective stress ranges for the two half-cycles are shown in Table 2:
[0070] Table 2
[0071]
[0072] The non-proportional degree for each half-cycle can be determined based on the cyclic path for each half-cycle using the following formula:
[0073]
[0074] Among them, g NPk The nonproportional degree in the k-th half-cycle, Let (r, θ) be the cyclic path in the kth half-cycle. The polar coordinates of a point in R k For loop path The distance between the two endpoints is half.
[0075] Based on the effective stress range and non-proportional coefficient under each half-cycle, the equivalent stress range under each half-cycle can be determined using the following formula:
[0076] Δσ NPk =Δσ ek (1+αg NPk )
[0077] Where, Δσ NPk Let Δσ be the range of equivalent stress during the k-th half-cycle. ek Let g be the effective stress range in the kth half-cycle. NPk The nonproportional coefficient is given by α, which is the material sensitivity coefficient, plotted based on multiaxial fatigue test data. Figure 8 In the reference loop number N Ref Under the same conditions, the effective stress range Δσ under proportional loading is obtained. e (A) Effective stress range Δσ under non-proportional loading e (B) The formula for calculating the value of α can be expressed as:
[0078]
[0079] The fatigue cycle number of the weld structure is determined based on the equivalent stress range and SN curve for each half-cycle. The fatigue cycle number of the weld structure includes the fatigue cycle number of the weld structure in each half-cycle, and can be determined using the following formula:
[0080]
[0081] Where, N k C represents the number of fatigue cycles of the weld structure in the kth half-cycle. d The constant is related to the material and stress ratio, while h is a constant. Based on numerous fatigue tests, the ASME standard provides C under different probability distributions. d The parameters h, the main SN curve generation table at the weld toe (steel) is shown in Table 3, and the main SN curve generation table at the weld root (steel) is shown in Table 4, where σ is the standard deviation:
[0082] Table 3
[0083]
[0084]
[0085] Table 4
[0086]
[0087] ΔS NPk The range of multiaxial equivalent structural stresses under the k-th half-cycle:
[0088]
[0089] Where, Δσ NPk Let t be the equivalent stress range under the kth half-cycle, t be the thickness of the base plate of the weld structure, m be the long crack propagation index, which is generally taken as 3.6, and I(r) be the dimensionless function of the bending load ratio r, which can be obtained by numerical fitting.
[0090] Then, in step S130, the fatigue life of the weld structure is determined based on the number of fatigue cycles of the weld structure under each set of load levels.
[0091] The multi-axis fatigue life assessment method for the intermediate shaft welded structure of the gearbox in this application addresses the fatigue failure problem of the weld area of the intermediate shaft structure of the gearbox in heavy-duty vehicles under cyclic loads. It establishes a fatigue life assessment model for the intermediate shaft welded structure using the multi-axis structural stress method and performs fatigue life analysis, which can predict the fatigue life of the structure relatively accurately.
[0092] In one embodiment, plotting the load path curve based on the finite element model includes:
[0093] The stress of the welded structure is obtained from the finite element model; the normal stress and in-plane shear stress at the weld are determined based on the stress. Here, the stress of the welded structure, including the normal stress σ at the weld, can be extracted from the finite element model using Fe-safe software or manually. s In-plane shear stress τ s
[0094] Load path curves are plotted based on the normal structural stress at the weld and the in-plane shear structural stress. Here, the load path curve is based on the normal structural stress σ at the weld. s In-plane shear stress τ s In the structural stress plane The load path curve is plotted within the range, where β is a material parameter, and for steel, the value of β is 3.
[0095] In one embodiment, determining the fatigue life of the welded structure based on the number of fatigue cycles of the welded structure under each set of load increments includes:
[0096] The degree of weld damage, D, is determined based on the number of fatigue cycles of the weld structure under each half-cycle of each load group; the fatigue life of the weld structure is determined based on the degree of weld damage.
[0097] In this embodiment, the degree of damage D to the weld structure can be determined using the following formula:
[0098]
[0099] Where, N ij Let n be the number of fatigue cycles of the weld structure under the k-th half-cycle of the i-th gear load. i denoted as the fatigue cycle number of the weld structure under the i-th load group obtained from the bench fatigue accelerated test, where M is the number of load groups and P is the number of half cycles of the i-th load group.
[0100] The fatigue life h of a welded structure can be determined using the following formula:
[0101]
[0102] Where D represents the degree of damage to the weld structure, and t represents the loading time of the load spectrum load, in minutes.
[0103] Example 1
[0104] The multi-axis fatigue life assessment method for the intermediate shaft welded structure of the gearbox in this embodiment includes:
[0105] 1) Establish a realistic finite element model of the intermediate shaft of the gearbox, including the weld seam. The mesh density should be selected appropriately based on the specific situation, such as... Figure 2 As shown;
[0106] 2) Add boundary conditions to the finite element model, and apply multiple gear loads (gears 1-6) of the load spectrum measured by the dynamometer (or actual load) evenly along the tooth width to the point where the tooth surface coincides with the pitch circle, such as... Figure 3 As shown, the load experiment spectrum (reasonably amplified results) of this example is shown in Table 5;
[0107] Table 5
[0108]
[0109] The translational degrees of freedom in the X and Z directions of the intermediate shaft and bearing assembly surface are restricted to prevent radial movement of the intermediate shaft structure, while retaining its rotational degree of freedom in the Y direction to simulate the rotation of the intermediate shaft within the bearing; the translational degree of freedom in the Y direction of the intermediate shaft end face is restricted to prevent axial movement of the intermediate shaft. Constraints are applied as follows: Figure 4 As shown in the figure. The maximum stress values at the weld root and weld toe in the weld area under cyclic loading at each gear position are shown in Table 6. The solution was obtained using Ansys software.
[0110] Table 6
[0111] 1st gear 2nd gear 3rd gear 4 gears 5 gears 6 gears Weld root stress / MPa 354.4 223.8 355.7 282.0 221.7 177.2 Weld toe stress / MPa 174.5 137.3 218.2 173.0 136.0 108.7
[0112] 3) Use Fe-safe software or manually extract the stress of the welded structure from the finite element model, including the normal structural stress σ at the weld. s In-plane shear stress τ s Here, the extracted stress is at the weld toe and weld root weld line, such as... Figure 9 As shown;
[0113] 4) Taking the structural stress at the weld root of grade 3 as an example, synthesize the load path curve. For example... Figure 10 As shown.
[0114] 5) Taking the structural stress at the weld root of grade 3 as an example, the PDMR multi-axis cyclic counting method is used for processing. Figure 10 The load path curve can be obtained Figure 11 The cyclic path shown is the first half-cycle. Figure 12 The cyclic path during the second half-cycle is shown. The counting results are summarized in Table 7:
[0115] Table 7
[0116]
[0117] 6) Taking the first half-cycle in 5) as an example, calculate the nonproportional degree g. NP1 :
[0118]
[0119] That is, the non-proportional coefficient of the AB path in the first half-cycle is 0.24. Similarly, using the same calculation method, the non-proportional coefficient of the BA path in the second half-cycle is 0.12907. The effective stress range at the weld root under various load conditions and the non-proportional coefficients under each half-cycle are shown in Table 8.
[0120] Table 8
[0121]
[0122] 7) Based on the nonproportional degrees in Table 8 and 6), combined with the formula Δσ NPk =Δσ ek (1+αg NPk The equivalent stress range at the weld root of the intermediate shaft welded structure under two and a half cycles of loads from level 1 to level 6 was calculated.
[0123] 8) According to The range of multiaxial equivalent structural stress for each half-cycle under loads 1-6 is obtained;
[0124] 9) According to Calculate the number of fatigue cycles of the weld structure under each half-cycle of loads 1-6;
[0125] 10) Calculate the degree of damage to the weld structure based on the number of fatigue cycles of the weld structure under each half-cycle of loads 1-6. Where, n i Let N be the number of fatigue cycles of the weld structure under the i-th load setting obtained from the bench fatigue accelerated test, where n1 = 2903.2, n2 = 7397.2, n3 = 6000, n4 = 12000, n5 = 25000, and n6 = 57000. ij The fatigue cycle number of the weld structure under the k-th half-cycle of the i-th load group.
[0126] 11) Calculate the fatigue life h of the welded structure based on the degree of weld damage D, as shown in Table 9:
[0127] Table 9
[0128]
[0129] Where t is the loading time of the load spectrum load, in minutes. In this embodiment, t = 94.8722 minutes. As can be seen from Table 9, the predicted fatigue life at the weld root is 52.5 hours, and at the weld toe is 110.5 hours. The fatigue life at the weld root is much lower than that at the weld toe, with a difference of about 50%, which is consistent with the range of differences in the currently known multiaxial fatigue test data at the weld root and weld toe.
[0130] Meanwhile, the results of the accelerated fatigue test on the bench showed that the fatigue life at the weld root was 47.4 hours, which deviated from the fatigue test value by 9.6%, verifying the accuracy of the fatigue assessment results. This indicates that it is correct and feasible to use the relevant criteria of the multiaxial structural stress method to conduct multiaxial fatigue life assessment of the intermediate shaft welded structure of the heavy-duty vehicle gearbox.
[0131] Based on the same inventive concept as the multi-axis fatigue life assessment method for the welded structure of the intermediate shaft of the gearbox, this embodiment also provides a corresponding multi-axis fatigue life assessment device for the welded structure of the intermediate shaft of the gearbox. Figure 13 A structural block diagram of a multi-axis fatigue life assessment device for a gearbox intermediate shaft welded structure according to an embodiment of this application is shown, including:
[0132] The finite element model construction module 131 is used to construct the finite element model of the welded structure. Boundary conditions are added to the finite element model, including the load spectrum load applied to the welded structure and the intermediate shaft constraint condition. The load spectrum load includes the load of the gearbox under multiple gears.
[0133] The fatigue cycle determination module 132 determines the number of fatigue cycles of the weld structure under each set of load levels.
[0134] The fatigue cycle number determination module 132 is also used for: plotting load path curves based on the finite element model; determining the cycle path and effective stress range for each half-cycle based on the load path curves; determining the non-proportional stress for each half-cycle based on the cycle path for each half-cycle; determining the equivalent stress range for each half-cycle based on the effective stress range and non-proportional stress for each half-cycle; and determining the fatigue cycle number of the weld structure based on the equivalent stress range for each half-cycle and the SN curve, wherein the fatigue cycle number of the weld structure includes the fatigue cycle number of the weld structure for each half-cycle.
[0135] The fatigue life determination module 133 determines the fatigue life of the welded structure based on the number of fatigue cycles of the welded structure under each set of load levels.
[0136] The multi-axis fatigue life assessment device for the intermediate shaft welded structure of the gearbox in this application addresses the fatigue failure problem of the weld area of the intermediate shaft structure of the gearbox in heavy-duty vehicles under cyclic load. It establishes a fatigue life assessment model for the intermediate shaft welded structure using the multi-axis structural stress method and performs fatigue life analysis, which can predict the fatigue life of the structure relatively accurately.
[0137] This application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the above-described method for evaluating the multi-axis fatigue life of the intermediate shaft welded structure of a gearbox.
[0138] This application provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the above-described method for evaluating the multi-axis fatigue life of the intermediate shaft welded structure of a gearbox.
[0139] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.
[0140] In addition, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.
[0141] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.
[0142] The above descriptions are merely various embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for evaluating the multi-axis fatigue life of a welded structure for an intermediate shaft of a gearbox, characterized in that, include: Constructing a finite element model of the welded structure; The finite element model includes boundary conditions, which include load spectrum loads applied to the welded structure and intermediate shaft constraint conditions. The load spectrum loads include multiple gear loads of the gearbox. For each load setting, determine the number of fatigue cycles for the weld structure under each load setting, including: Draw the load path curve based on the finite element model; The cyclic path and effective stress range for each half-cycle are determined based on the load path curve. The non-proportional degree for each half-cycle is determined based on the cyclic path for each half-cycle. The equivalent stress range for each half-cycle is determined based on the effective stress range and non-proportional coefficient for each half-cycle. The fatigue cycle number of the weld structure is determined based on the equivalent stress range and SN curve under each half-cycle, and the fatigue cycle number of the weld structure includes the fatigue cycle number of the weld structure under each half-cycle. The fatigue life of the welded structure is determined based on the number of fatigue cycles of the welded structure under each set of load levels. The process of plotting the load path curve based on the finite element model includes: The stress of the welded structure is obtained based on the finite element model. The normal structural stress and in-plane shear structural stress at the weld of the welded structure are determined based on the stress of the welded structure. Based on the normal structural stress and in-plane shear structural stress at the weld, a load path curve is plotted. The non-proportional degree for each half-cycle is determined based on the cyclic path for each half-cycle, using the following formula: in, The nonproportional degree in the k-th half-cycle, For the cyclic path in the kth half-cycle, ( () is a loop path The polar coordinates of the points in the middle. For loop path The distance between the two endpoints is half.
2. The method as described in claim 1, characterized in that, in, The fatigue life of the welded structure is determined based on the number of fatigue cycles of the welded structure under each set of load levels, including: The degree of damage to the weld structure is determined based on the number of fatigue cycles of the weld structure under each half-cycle of each gear load. The fatigue life of the welded structure is determined based on the degree of damage to the weld structure.
3. The method as described in claim 2, characterized in that, in, The degree of damage to the weld structure is determined based on the number of fatigue cycles of the weld structure under each half-cycle of each load group, including: D Where D represents the degree of damage to the weld structure. Let be the number of fatigue cycles of the weld structure under the k-th half-cycle of the i-th load group. denoted as the fatigue cycle number of the weld structure under the i-th load group obtained from the bench fatigue accelerated test, where M is the number of load groups and P is the number of half cycles of the i-th load group.
4. The method as described in claim 1, characterized in that, in, The equivalent stress range for each half-cycle is determined based on the effective stress range and non-proportional coefficient under each half-cycle, using the following formula: in, This represents the equivalent stress range during the k-th half-cycle. The effective stress range under the k-th half-cycle. The nonproportional degree in the k-th half-cycle, This is the material sensitivity coefficient.
5. The method as described in claim 1, characterized in that, in, The fatigue cycle number of the weld structure is determined based on the equivalent stress range and SN curve under each half-cycle, using the following formula: in, Let be the number of fatigue cycles of the weld structure in the k-th half-cycle. It is a constant. h It is a constant; The range of multiaxial equivalent structural stresses under the k-th half-cycle: in, Let t be the equivalent stress range under the kth half-cycle, t be the thickness of the base plate of the weld structure, m be the long crack propagation index, and I(r) be the dimensionless function of the bending load ratio r.
6. A multi-axis fatigue life assessment device for a welded structure of a gearbox intermediate shaft, characterized in that, include: The finite element model building module is used to build finite element models of welded structures. The finite element model includes boundary conditions, which include load spectrum loads applied to the welded structure and intermediate shaft constraint conditions. The load spectrum loads include multiple gear loads of the gearbox. The fatigue cycle determination module determines the number of fatigue cycles for the weld structure under each load setting. The fatigue cycle number determination module is further configured to: plot load path curves based on the finite element model; determine the cycle path and effective stress range for each half-cycle based on the load path curves; determine the non-proportional stress for each half-cycle based on the cycle path for each half-cycle; determine the equivalent stress range for each half-cycle based on the effective stress range and non-proportional stress for each half-cycle; and determine the fatigue cycle number of the weld structure based on the equivalent stress range for each half-cycle and the SN curve, wherein the fatigue cycle number of the weld structure includes the fatigue cycle number of the weld structure for each half-cycle. The fatigue life determination module determines the fatigue life of the welded structure based on the number of fatigue cycles of the welded structure under each set of load levels. The process of plotting the load path curve based on the finite element model includes: The stress of the welded structure is obtained based on the finite element model. The normal structural stress and in-plane shear structural stress at the weld of the welded structure are determined based on the stress of the welded structure. Based on the normal structural stress and in-plane shear structural stress at the weld, a load path curve is plotted. The non-proportional degree for each half-cycle is determined based on the cyclic path for each half-cycle, using the following formula: in, The nonproportional degree in the k-th half-cycle, For the cyclic path in the kth half-cycle, ( () is a loop path The polar coordinates of the points in the middle. For loop path The distance between the two endpoints is half.
7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the multi-axis fatigue life assessment method for the intermediate shaft welded structure of the gearbox as described in any one of claims 1-5.
8. A computer program product, characterized in that, It includes a computer program / instruction that, when executed by a processor, implements the multi-axis fatigue life assessment method for the intermediate shaft welded structure of the gearbox as described in any one of claims 1-5.