A method for analyzing the strength of a transmission housing

Abstract

Embodiments of the present application provide a method for analyzing the strength of a gearbox housing, the method comprising: constructing a housing finite element model, the housing finite element model comprising thread bottom features corresponding to each threaded hole on the gearbox housing; setting a threaded friction contact constraint of the housing finite element model; loading at least one load on the housing finite element model, performing a finite element simulation operation, and obtaining a stress nephogram of the housing finite element model; and performing static strength analysis and fatigue strength analysis of the gearbox housing according to the stress nephogram. The technical solution of the embodiments of the present application can analyze the strength of the threaded hole, detect the reliable durability of the threaded hole, and thus complete the strength analysis of the gearbox housing.

Description

Technical Field

[0001] This application relates to the field of finite element simulation technology, and more specifically, to a strength analysis method for a gearbox housing. Background Technology

[0002] In the field of gearbox simulation design, there is currently no method for verifying the strength of threaded holes; only other areas of the housing have been verified. Threaded holes connecting gearbox mounting brackets typically employ a boss structure, and the diameter and other morphological features of this boss structure affect the stiffness of the threaded hole. If the threaded hole stiffness is low, the threads are highly susceptible to deformation under high stress due to external loads, leading to stress changes and eventually fatigue failure over time.

[0003] Therefore, those skilled in the art urgently need a strength analysis method for gearbox housings that can analyze the strength of threaded holes and test the reliability and durability of threaded holes, thereby completing the strength analysis of gearbox housings. Summary of the Invention

[0004] The embodiments of this application provide a strength analysis method for a gearbox housing, which can at least to a certain extent analyze the strength of threaded holes, detect the reliability and durability of threaded holes, and thus complete the strength analysis of the gearbox housing.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] According to one aspect of the embodiments of this application, a strength analysis method for a gearbox housing is provided. The method includes: constructing a finite element model of the housing, the finite element model of the housing including the root features of each threaded hole on the gearbox housing; setting thread friction contact constraints for the finite element model of the housing; applying at least one load to the finite element model of the housing, performing finite element simulation calculations to obtain a stress cloud diagram of the finite element model of the housing; and performing static strength analysis and fatigue strength analysis of the gearbox housing based on the stress cloud diagram.

[0007] In some embodiments of this application, the construction of the shell finite element model, which includes the root features of each threaded hole on the gearbox shell, includes: establishing at least one local model of the threaded hole based on the root features of each threaded hole on the gearbox shell; converting each local model of the threaded hole into a hexahedral finite element model; meshing other areas of the gearbox shell to generate a tetrahedral finite element model; and combining each hexahedral finite element model and the tetrahedral finite element model to construct the shell finite element model.

[0008] In some embodiments of this application, based on the aforementioned scheme, the step of converting the local model of each threaded hole into a hexahedral finite element model includes: dividing the local model of each threaded hole along the axial plane, performing mesh generation for each threaded hole section, and generating a hexahedral finite element model corresponding to each threaded hole section.

[0009] In some embodiments of this application, based on the aforementioned scheme, the step of meshing each threaded hole section and generating a hexahedral finite element model corresponding to each threaded hole section includes: meshing each threaded hole section, rotating and stretching the mesh of each threaded hole section along the threaded hole axis into a hexahedron, and generating a hexahedral finite element model corresponding to each threaded hole section.

[0010] In some embodiments of this application, setting the thread friction contact constraint of the shell finite element model includes: setting the thread friction contact constraint of the shell finite element model using the Langron multiplier method.

[0011] In some embodiments of this application, the loading of at least one load onto the housing finite element model includes: loading a thread preload load onto the housing finite element model, the thread preload load being used to characterize the force load between each bolt and its corresponding threaded hole; loading a suspension condition load onto the housing finite element model, the suspension condition load being used to characterize the force load on the bolts and threaded holes used for suspension on the gearbox housing; and loading a suspension vibration load onto the housing finite element model, the suspension vibration load being used to characterize the vibration load on the bolts and threaded holes used for suspension on the gearbox housing in at least one direction.

[0012] In some embodiments of this application, the step of performing static strength analysis of the gearbox housing based on the stress cloud diagram includes: obtaining material mechanical property parameters of the gearbox housing, the material mechanical property parameters being used to characterize the mechanical properties of the material used to manufacture the gearbox housing; and performing static strength analysis of the gearbox housing based on the stress cloud diagram and the material mechanical property parameters.

[0013] In some embodiments of this application, based on the foregoing scheme, the static strength analysis of the gearbox housing according to the stress cloud diagram and the material mechanical property parameters includes: comparing the stress magnitude at each point in the stress cloud diagram with the material mechanical property parameters; and completing the static strength analysis of the gearbox housing based on the comparison results of the stress magnitude at each point and the material mechanical property parameters.

[0014] In some embodiments of this application, the fatigue strength analysis of the gearbox housing based on the stress cloud diagram includes: obtaining the material mechanical property parameters of the gearbox housing, the material mechanical property parameters being used to characterize the mechanical properties of the material used to manufacture the gearbox housing; calculating the fatigue safety factor of the finite element model of the housing based on the material mechanical property parameters and the stress cloud diagram; and performing fatigue strength analysis of the gearbox housing based on the fatigue safety factor.

[0015] In some embodiments of this application, based on the foregoing scheme, the step of performing fatigue strength analysis of the gearbox housing according to the fatigue safety factor includes: obtaining a standard fatigue safety factor, comparing the fatigue safety factor with the standard safety factor; and completing the fatigue strength analysis of the gearbox housing based on the comparison result of the fatigue safety factor and the standard safety factor.

[0016] Based on the above solution, the technical solution provided in this application has at least the following advantages and advancements:

[0017] In this application, a finite element model of the housing, including the root features of each threaded hole, is constructed. Finite element simulation is then performed to obtain the stress cloud diagram of the housing finite element model. Based on the stress cloud diagram, static strength analysis and fatigue strength analysis of the gearbox housing are performed. This can effectively improve the modeling accuracy of the housing finite element model and make it more consistent with the actual situation. In addition to static strength analysis, this application also performs fatigue strength analysis, which can analyze the strength of the gearbox housing during use and simulate the fatigue condition of the gearbox housing after it is loaded into the vehicle, making the strength analysis more comprehensive.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0020] Figure 1 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown;

[0021] Figure 2 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown;

[0022] Figure 3 A simplified diagram of the thread geometry model is shown;

[0023] Figure 4 A simplified diagram of a conventional threaded hole geometry is shown.

[0024] Figure 5 A simplified diagram of a parallel threaded hole model according to one embodiment of this application is shown;

[0025] Figure 6 A partial model diagram of a threaded hole according to one embodiment of this application is shown;

[0026] Figure 7 A schematic diagram of a threaded hole mesh is shown in one embodiment of this application;

[0027] Figure 8 A road load spectrum according to one embodiment of this application is shown;

[0028] Figure 9 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown;

[0029] Figure 10 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown;

[0030] Figure 11 A stress cloud diagram is shown in one embodiment according to this application;

[0031] Figure 12 A comparative schematic diagram of a reinforced shell finite element model is shown in one embodiment of this application;

[0032] Figure 13 The stress cloud diagram after strengthening is shown in one embodiment of this application;

[0033] Figure 14 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown;

[0034] Figure 15 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown;

[0035] Figure 16 An SN curve is shown in one embodiment according to this application;

[0036] Figure 17 A schematic diagram of fatigue failure of a gearbox threaded hole according to one embodiment of this application is shown;

[0037] Figure 18A cloud diagram showing the distribution of the safety factor of the threaded hole according to one embodiment of this application is illustrated;

[0038] Figure 19 A cloud map showing the distribution of the safety factor of a threaded hole according to one embodiment of this application is shown. Detailed Implementation

[0039] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0040] Please see Figure 1 .

[0041] Figure 1 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown, as follows: Figure 1 As shown, the method may include steps S101-S104:

[0042] Step S101: Construct a finite element model of the housing, which includes the root features of each threaded hole on the gearbox housing.

[0043] Step S102: Set the thread friction contact constraint of the shell finite element model.

[0044] Step S103: Apply at least one load to the shell finite element model, perform finite element simulation calculation, and obtain the stress cloud diagram of the shell finite element model.

[0045] Step S104: Based on the stress cloud diagram, perform static strength analysis and fatigue strength analysis on the gearbox housing.

[0046] In this application, a finite element model of the housing, including the root features of each threaded hole, can be constructed and finite element simulation calculations can be performed to obtain the stress cloud diagram of the housing finite element model. Then, based on the stress cloud diagram, static strength analysis and fatigue strength analysis of the gearbox housing can be performed, which can effectively improve the modeling accuracy of the housing finite element model and make it more in line with the actual situation. In addition, in addition to static strength analysis, this application also performs fatigue strength analysis, which can analyze the strength of the gearbox housing during use and simulate the fatigue condition of the gearbox housing after it is loaded into the vehicle, making the strength analysis more comprehensive.

[0047] Please see Figure 2 .

[0048] Figure 2A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown, as follows: Figure 2 As shown, in step S101, the construction of the housing finite element model, which includes the root features of each threaded hole on the gearbox housing, may include steps S201-S203:

[0049] Step S201: Based on the root features of each threaded hole on the gearbox housing, establish at least one local model of the threaded hole, and convert each local model of the threaded hole into a hexahedral finite element model.

[0050] Step S202: Mesh the other areas of the gearbox housing to generate a tetrahedral finite element model.

[0051] Step S203: Combine each hexahedral finite element model and the tetrahedral finite element model to construct a shell finite element model.

[0052] In this application, bolt holes are typically represented by cylindrical surfaces in the geometric model of a gearbox housing. To verify the reliability of the threads, a realistic geometric model of the threads must be constructed. A thread is a helical, continuous, raised portion with a specific cross-section formed on the surface of a cylindrical or conical substrate. For example, please refer to... Figure 3 , Figure 3 A simplified diagram of the thread geometry model is shown, as follows: Figure 3 As shown, a thread can include five elements: tooth profile, nominal diameter, number of threads, pitch, and direction of rotation.

[0053] Among them, the thread profile: the outline shape of the thread in the cross-sectional area passing through the thread axis is called the thread profile. According to the cross-sectional shape of the thread, it can be divided into triangular thread, trapezoidal thread, rectangular thread, sawtooth thread and other special-shaped thread.

[0054] Nominal diameter: The nominal diameter is the diameter that represents the thread size, and it is divided into major diameter, pitch diameter and minor diameter.

[0055] Number of threads: A thread formed along a single helix is ​​called a single-start thread, and a thread formed by two or more helices that are equidistant from each other along the axial direction is called a multi-start thread.

[0056] Pitch: Pitch refers to the axial distance between two corresponding points on the pitch line of two adjacent threads.

[0057] Direction of rotation: refers to the direction in which the thread is screwed in.

[0058] Real thread threads are helical in shape, making mesh construction complex and time-consuming. Existing thread mesh construction methods only retain features such as tooth profile, nominal diameter, number of lines, and pitch, and the bolt and threaded hole have a tight fit, such as... Figure 4As shown, Figure 4 A simplified geometric model of a conventional threaded hole is shown. Due to the influence of the nonlinear contact algorithm in the finite element analysis software, the nodal stresses on the contact surface are not considered. Therefore, the tight contact between the threaded hole and the bolt makes it impossible to accurately obtain stress information on the thread.

[0059] In step S201, to eliminate this influence, the tooth crest and root features of the thread can be preserved during the modeling process, while the helical thread is optimized into a parallel thread, ensuring the efficiency and accuracy of the thread stress calculation. For example, as... Figure 5 As shown, Figure 5 A simplified diagram of a parallel threaded hole model according to one embodiment of this application is shown.

[0060] In step S201, when establishing at least one local model of a threaded hole, since the geometric features of the thread are much smaller than other features of the shell, in order to ensure the calculation accuracy of the thread position and the overall calculation efficiency, this application cuts the threaded hole from the shell and constructs a local sub-model with the bolt. For example, as... Figure 6 As shown, Figure 6 A partial model diagram of a threaded hole according to one embodiment of this application is shown.

[0061] In step S201, the method of converting the local model of each threaded hole into a hexahedral finite element model may include: dividing the local model of each threaded hole along the axial plane, performing mesh generation for each threaded hole section, and generating a hexahedral finite element model corresponding to each threaded hole section.

[0062] In this application, the method for meshing each threaded hole section and generating a hexahedral finite element model corresponding to each threaded hole section may include: meshing each threaded hole section, rotating and stretching the mesh of each threaded hole section along the threaded hole axis into a hexahedron, and generating a hexahedral finite element model corresponding to each threaded hole section.

[0063] In this application, the local model of each threaded hole can be divided along the axial plane, and the cut threaded hole cross-section is meshed. Dividing lines are used to divide the threaded hole cross-section into different regular regions, and quadrilateral meshes are used to divide the threaded hole cross-section. The crest and root of the threaded tooth have more mesh layers and smaller dimensions to reflect the geometric characteristics of the threaded tooth. Larger geometric surfaces far from the threaded tooth have fewer mesh layers. The nodes at the engagement positions of the bolt and the threaded hole correspond one-to-one to ensure computational accuracy and convergence efficiency. The mesh on the threaded hole cross-section is rotated 360° along the threaded hole axis and stretched into a hexahedron. In this invention, the radial mesh layer count of the threaded hole can be 72. For example, please refer to... Figure 7 , Figure 7 A schematic diagram of a threaded hole mesh is shown in one embodiment of this application.

[0064] In this application, the method for setting the thread friction contact constraint of the shell finite element model may include: setting the thread friction contact constraint of the shell finite element model using the Langron multiplier method.

[0065] In this application, the threaded hole and bolt rely on the friction between the threads to achieve tightening. The gearbox housing design can be optimized by considering the strength of the threaded hole; therefore, the accuracy of the threaded hole strength calculation is crucial. Compared to the entire gearbox housing, the threaded hole has a smaller structural feature, making the convergence of contact calculations in finite element software more difficult. Therefore, the setting of friction constraints is very important. Generally, the penalty function method is used for friction constraints on components. The penalty function method is suitable for most friction analyses, introducing a small reversible slip γ, which improves convergence. However, a large γ value will sacrifice calculation accuracy. This application uses the Lagrange multiplier method, which is suitable for problems requiring a precise description of adhesion-slip behavior.

[0066] In this application, a thread preload load can be applied to the finite element model of the housing, and the thread preload load is used to characterize the force load between each bolt and the corresponding threaded hole.

[0067] In this application, bolt preload is the primary load on the bolt and threaded hole. The maximum and minimum preload of the bolt can be calculated based on factors such as bolt grade, torque control accuracy, and friction coefficient. To address reliability concerns, the maximum bolt preload is used as the thread preload load.

[0068] In this application, a suspension load can be applied to the finite element model of the housing, and the suspension load is used to characterize the force load on the bolts and threaded holes on the gearbox housing used for suspension.

[0069] In this application, the bolt boss at the gearbox mount primarily bears the load of the mount itself. The mount load in this application is obtained through test road spectrum acquisition. After removing test errors such as spikes and mean drift in the load spectrum signal, a usable road spectrum curve is obtained. The ultimate loads in the six positive and negative directions (X, Y, Z) of the vehicle coordinate system can be taken as the mount loads. For example, please refer to... Figure 8 , Figure 8 A road load spectrum according to one embodiment of this application is shown.

[0070] In this application, a suspension vibration load can be applied to the finite element model of the housing, the suspension vibration load being used to characterize the vibration load on the bolts and threaded holes used for suspension on the gearbox housing in at least one direction.

[0071] In this application, to verify the fatigue durability of the threaded hole, a suspension vibration load also needs to be applied. Statistical analysis of the edited road spectrum can be performed to calculate the root mean square value. The magnitudes of the accelerations acting on the gearbox suspension in each direction are shown in Table 1, and this load is defined as the high-cycle fatigue load. Then, a dynamic model of the powertrain is built, and the force load on the suspension bracket is calculated. The high-cycle fatigue analysis conditions of this application are shown in Table 1.

[0072] Table 1 High-cycle fatigue conditions

[0073]

[0074]

[0075] Based on the assembly condition, a high-cycle fatigue condition is then applied to obtain the fatigue stress results under fatigue conditions in various directions.

[0076] Please see Figure 9 .

[0077] Figure 9 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown, as follows: Figure 9 As shown, in step S104, the method for performing static strength analysis of the gearbox housing based on the stress cloud diagram may include steps S901-S902:

[0078] Step S901: Obtain the material mechanical property parameters of the gearbox housing. The material mechanical property parameters are used to characterize the mechanical properties of the material used to manufacture the gearbox housing.

[0079] Step S902: Based on the stress cloud diagram and the material mechanical property parameters, perform static strength analysis on the gearbox housing.

[0080] Please see Figure 10 .

[0081] Figure 10 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown, as follows: Figure 10 As shown, in step S902, the method for performing static strength analysis of the gearbox housing based on the stress cloud diagram and the material mechanical property parameters may include steps S1001-S1002:

[0082] Step S1001: Compare the stress magnitude at various points in the stress cloud diagram with the mechanical property parameters of the material.

[0083] Step S1002: Based on the comparison results of the stress magnitude at various locations and the mechanical property parameters of the material, complete the static strength analysis of the gearbox housing.

[0084] In this application, the failure of metallic materials generally goes through four stages: elasticity, yielding, strengthening, and local deformation, and there are four characteristic points, with the corresponding stresses being the proportional limit, elastic limit, yield limit, and ultimate tensile strength, in that order. However, for gearboxes, the commonly used aluminum alloy material, evaluated based on its elongation after fracture, should be considered a brittle material. Generally, under static strength limit conditions, ensuring the reliability of the threaded hole is that the maximum stress value is less than the ultimate tensile strength is sufficient.

[0085] In this application, the maximum stress of each threaded hole can be determined by the stress cloud diagram, or the location of the maximum stress in the shell finite element model can be determined. By comparing the maximum stress with the strength limit in the material's mechanical properties, it can be predicted whether the current location is prone to material failure, and then corresponding reinforcement optimization can be performed.

[0086] For example, please see Figure 11 , Figure 11 A stress cloud diagram according to one embodiment of this application is shown, such as Figure 11 As shown, the stress values ​​at the root of the threaded hole all exceed the strength limit of the housing material (240 MPa). Stress cloud diagram analysis results indicate that the threaded hole is at risk of failure. After actual fabrication of the gearbox housing, cracks appeared at the corresponding locations, further verifying the accuracy of the technical method presented in this application.

[0087] Therefore, it can be determined that the failure at the threaded hole location is mainly due to insufficient stiffness of the bolt boss. Under the suspension ultimate load, the threaded hole deforms, leading to excessive stress at the thread root. The reliability optimization method for threaded holes primarily targets the areas with poor stiffness, improving their resistance to deformation.

[0088] In this application, the following methods can be used for reinforcement and optimization:

[0089] 1. Increase the wall thickness of the threaded hole boss;

[0090] 2. Add reinforcing ribs to the outside of the threaded hole failure location;

[0091] 3. Thicken the existing reinforcing ribs.

[0092] For example, please see Figure 12 , Figure 12 A comparative schematic diagram of a reinforced shell finite element model according to one embodiment of this application is shown. For further stress contour plot analysis, please refer to [link to relevant documentation]. Figure 13 , Figure 13 The following is a stress contour plot after strengthening according to one embodiment of this application, such as Figure 13As shown, the root stress at the failure location of the reinforced threaded hole is below the strength limit, and subsequent production verification also proved that the same location no longer appears.

[0093] Please see Figure 14 .

[0094] Figure 14 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown, as follows: Figure 14 As shown, in step S104, the method for performing fatigue strength analysis of the gearbox housing based on the stress cloud diagram may include steps S1401-S1403:

[0095] Step S1401: Obtain the material mechanical property parameters of the gearbox housing. The material mechanical property parameters are used to characterize the mechanical properties of the material used to manufacture the gearbox housing.

[0096] Step S1402: Calculate the fatigue safety factor of the shell finite element model based on the material mechanical property parameters and the stress cloud diagram.

[0097] Step S1403: Perform fatigue strength analysis on the gearbox housing based on the fatigue safety factor.

[0098] Please see Figure 15 .

[0099] Figure 15 A simplified flowchart of a strength analysis method for a gearbox housing according to an embodiment of this application is shown, as follows: Figure 15 As shown, in step S1403, the method for performing fatigue strength analysis of the gearbox housing based on the fatigue safety factor may include steps S1501-S1502:

[0100] Step S1501: Obtain the standard fatigue safety factor and compare the fatigue safety factor with the standard safety factor.

[0101] Step S1502: Based on the comparison results of the fatigue safety factor and the standard safety factor, complete the fatigue strength analysis of the gearbox housing.

[0102] In this application, the fatigue safety factor of the shell finite element model is calculated using the material mechanical property parameters and the stress cloud diagram. By comparing the fatigue safety factor with the standard safety factor, it is possible to predict whether the material fatigue failure is likely to occur at the current location, and then perform corresponding reinforcement optimization.

[0103] In this application, the calculation of the fatigue safety factor requires the material mechanical properties parameters of the shell material, and the specific material mechanical properties can be shown in Table 2.

[0104] Table 2 Mechanical property parameters of shell material

[0105]

[0106] Importing material mechanical property parameters into fatigue software allows the acquisition of the crack initiation life (SN) curve, which is crucial for calculating fatigue safety factors. The basic SN curve of a material provides the crack initiation life of a smooth material under constant amplitude symmetrical cyclic stress. For example, please refer to [link to relevant documentation]. Figure 16 , Figure 16 An SN curve according to one embodiment of this application is shown.

[0107] In this application, there are many factors that affect the SN curve. The standard SN curve is obtained from sample tests, but there are differences between the sample and the actual part, which need to be taken into account in the calculation.

[0108] (1) Stress gradient

[0109] Smooth specimens do not exhibit stress concentration, but actual components may have grooves or gaps, requiring stress concentration and gap correction.

[0110] (2) Dispersion

[0111] Even with the same test materials, experimental results exhibit a certain degree of dispersion. The dispersion is defined as the ratio of the fatigue strength at a 10% survival rate to the fatigue strength at a 90% survival rate.

[0112] (3) Mean stress

[0113] In practice, the stress-time history of a component is usually asymmetrical, meaning that the cyclic characteristic values ​​are different. Therefore, it is necessary to perform an average stress correction on the stress-time history. The purpose of the correction is to convert the actual stress state of the component to the stress ratio state during material testing, based on the equal lifespan principle.

[0114] (4) Size effect

[0115] For tensile and compressive loading, the larger the diameter and the larger the circumference, the greater the probability of weak points appearing, and the more and earlier cracks will appear. Therefore, the fatigue resistance of large-sized components is lower than that of small-sized samples.

[0116] (5) Surface finishing

[0117] Fatigue cracks typically initiate on the surface of parts, therefore surface condition has a significant impact on fatigue life. Higher surface finish leads to a longer time for fatigue cracks to form. Residual stress in the surface layer usually influences crack initiation, while residual compressive stress can delay the development of high-cycle fatigue cracks. Surface layer pre-compression can be achieved through processes such as shot peening, cold rolling, and nitriding. Since gearbox housings are castings, their surfaces typically have a dense layer, which improves the safety factor.

[0118] The machining process for threaded holes can be divided into cutting threads and forming threads, and different machining processes have a significant impact on the parameter settings for fatigue calculation of threaded holes.

[0119] Therefore, based on the aforementioned influencing factors, this application can set parameters to ensure the accuracy of threaded hole fatigue calculations. For example, a list of material mechanical property parameters for cast aluminum alloys can be shown in Table 3.

[0120] Table 3 Mechanical property parameters of shell material

[0121] Impact Factor numerical values stress gradient ON Mean stress ON Mean stress adjustment OFF Revised Hager Map OFF Statistical impact ON Survival rate 99.99％ Dispersion 1.4 Surface roughness 60μm Influence of process dimensions 15mm Surface strength coefficient 1.5

[0122] For example, please see Figure 17 , Figure 17 A schematic diagram of fatigue failure of a threaded hole in a gearbox (reduction gearbox) according to one embodiment of this application is shown. The current machining process for the failed threaded hole is cutting, and the fatigue parameters for this threaded hole are set as shown in Table 4.

[0123] Table 4 Mechanical performance parameters of threaded hole cutting process

[0124]

[0125]

[0126] For calculations of the fatigue safety factor, please refer to [link / reference]. Figure 18 , Figure 18 A distribution cloud diagram of the safety factor of a threaded hole according to one embodiment of this application is shown. The standard fatigue safety factor in this application can be set to 1.1. The standard fatigue safety factor can be obtained by statistically analyzing the safety factors of several gearboxes under the same test and taking the lowest safety factor as the evaluation standard. The fatigue analysis results show that the fatigue safety factor of the threaded hole is 0.764, located at the root of the first thread, which coincides with the test failure location, and does not meet the fatigue safety requirements.

[0127] Due to the boundary limitations of the digital model, the threaded hole is optimized without modifying the model. In this application, the machining method for the threaded hole can be changed to an extrusion process. The threaded hole manufactured by the extrusion process will have a dense layer on the surface and residual compressive stress. Taking these factors into account, the fatigue parameters of the threaded hole manufactured by the extrusion process can be set as shown in Table 5.

[0128] Table 5 Mechanical performance parameters of threaded hole cutting process

[0129] Influence factor Thread-cut stress gradient ON Mean stress OFF Mean stress adjustment OFF Revised Hager Map ON Survival rate 99.99％ Dispersion 1.26 Surface roughness OFF Influence of process dimensions OFF Surface strength coefficient 2.2

[0130] Please refer to the following. Figure 19 , Figure 19 A distribution cloud diagram of the threaded hole safety factor according to one embodiment of this application is shown, such as... Figure 19 As shown, after process optimization, the minimum fatigue safety factor of the threaded hole reaches 1.324, located at the root of the first thread. The optimized solution was verified through experiments, demonstrating the feasibility of the process optimization.

[0131] In summary, this application constructs a finite element model of the housing, including the root features of each threaded hole, performs finite element simulation calculations, obtains the stress cloud diagram of the housing finite element model, and then performs static strength analysis and fatigue strength analysis of the gearbox housing based on the stress cloud diagram. This can effectively improve the modeling accuracy of the housing finite element model, making it more consistent with actual conditions. In addition, this application performs fatigue strength analysis in addition to static strength analysis, which can analyze the strength of the gearbox housing during use and simulate the fatigue condition of the gearbox housing after it is loaded into the vehicle, making the strength analysis more comprehensive.

[0132] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0133] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for strength analysis of a gearbox housing, characterized in that, The method includes: Construct a finite element model of the housing, which includes the root features of each threaded hole on the gearbox housing; Set the thread friction contact constraint for the finite element model of the shell; At least one load is applied to the shell finite element model, and finite element simulation is performed to obtain the stress cloud diagram of the shell finite element model; Based on the stress cloud diagram, static strength analysis and fatigue strength analysis of the gearbox housing are performed. The construction of the housing finite element model includes the thread root features corresponding to each threaded hole on the gearbox housing, including: Based on the root features of each threaded hole on the gearbox housing, at least one local model of the threaded hole is established, and each local model of the threaded hole is converted into a hexahedral finite element model. Mesh the other areas of the gearbox housing to generate a tetrahedral finite element model; By combining the various hexahedral finite element models and the tetrahedral finite element model, a shell finite element model is constructed.

2. The method according to claim 1, characterized in that, The process of converting the local models of each threaded hole into hexahedral finite element models includes: The local model of each threaded hole is divided along the axial plane, and the mesh is generated for each threaded hole section to produce a hexahedral finite element model corresponding to each threaded hole section.

3. The method according to claim 2, characterized in that, The process of meshing each threaded hole cross-section to generate a hexahedral finite element model corresponding to each threaded hole cross-section includes: Mesh each threaded hole section, rotate and stretch the mesh of each threaded hole section along the threaded hole axis into a hexahedron, and generate the hexahedron finite element model corresponding to each threaded hole section.

4. The method according to claim 1, characterized in that, The setting of thread friction contact constraints for the finite element model of the shell includes: The thread friction contact constraint of the shell finite element model is set using the Langron multiplier method.

5. The method according to claim 1, characterized in that, The loading of at least one load onto the shell finite element model includes: A thread preload is applied to the finite element model of the shell. The thread preload is used to characterize the force load between each bolt and the corresponding threaded hole. A suspension load is applied to the finite element model of the housing. The suspension load is used to characterize the force load on the bolts and threaded holes on the gearbox housing used for suspension. A suspension vibration load is applied to the finite element model of the housing, the suspension vibration load being used to characterize the vibration load on the bolts and threaded holes used for suspension on the gearbox housing in at least one direction.

6. The method according to claim 1, characterized in that, The static strength analysis of the gearbox housing based on the stress cloud diagram includes: Obtain the material mechanical property parameters of the gearbox housing, which are used to characterize the mechanical properties of the material used to manufacture the gearbox housing; Based on the stress cloud diagram and the material mechanical property parameters, a static strength analysis of the gearbox housing is performed.

7. The method according to claim 6, characterized in that, The static strength analysis of the gearbox housing based on the stress cloud diagram and the material mechanical property parameters includes: Compare the stress magnitude at various points in the stress cloud diagram with the mechanical property parameters of the material; Based on the comparison results of the stress magnitude at various locations and the mechanical property parameters of the material, the static strength analysis of the gearbox housing is completed.

8. The method according to claim 1, characterized in that, The fatigue strength analysis of the gearbox housing based on the stress cloud diagram includes: Obtain the material mechanical property parameters of the gearbox housing, which are used to characterize the mechanical properties of the material used to manufacture the gearbox housing; The fatigue safety factor of the shell finite element model is calculated based on the material mechanical property parameters and the stress cloud diagram. Based on the fatigue safety factor, a fatigue strength analysis of the gearbox housing is performed.

9. The method according to claim 8, characterized in that, The fatigue strength analysis of the gearbox housing based on the fatigue safety factor includes: Obtain the standard fatigue safety factor and compare the fatigue safety factor with the standard fatigue safety factor; Based on the comparison between the fatigue safety factor and the standard fatigue safety factor, the fatigue strength analysis of the gearbox housing is completed.

Images