Differential case fatigue strength analysis method and apparatus

Abstract

The embodiment of the application provides a kind of differential mechanism shell fatigue strength analysis method and device, belong to differential mechanism shell fatigue strength technical field.The method includes confirming the loading position of the load applied to the differential mechanism shell;According to the confirmed loading position, FEA analysis is carried out to obtain a stress nephogram;Select dangerous point in the stress nephogram;Linear scaling is carried out on the dangerous point under different working conditions to obtain the corresponding maximum stress and minimum stress;According to the corrected equal-life fatigue curve, the fatigue limit and the maximum allowable stress are obtained;According to the fatigue limit and the maximum allowable stress, the S-N curve is fitted;According to the fitted S-N curve, the cumulative damage is calculated;The differential mechanism shell fatigue strength analysis method and device correct the equal-life fatigue curve, which can improve the reliability of simulation and reduce the failure rate of parts.

Description

Technical Field

[0001] This invention relates to the field of differential housing fatigue strength technology, and specifically to a method and apparatus for analyzing the fatigue strength of a differential housing. Background Technology

[0002] The differential is the last link in the torque transmission of a new energy vehicle reducer. It is the component that transmits the largest torque in the reducer, requiring it to have high static strength and fatigue strength. As a result, many manufacturers often design differentials to be too large and heavy, taking up more space and hindering the lightweighting of new energy vehicles. The weight of the differential housing often accounts for more than 70% of the total weight of the differential assembly. Therefore, the simulation and prediction of the differential housing strength has become a key part of the lightweighting of new energy vehicle differentials. Static strength simulation is very mature and can predict the static strength failure of parts very well. However, the simulation of fatigue strength is more labor-intensive and more difficult to achieve accuracy.

[0003] Existing methods are relatively convenient for calculating differential housing damage under single-load conditions. However, when there are multiple load conditions and multiple different stress ratios, the calculation becomes more complex. At this time, a large number of calculations are required to obtain the symmetrical cyclic stress level and SN curve, making this method quite time-consuming and labor-intensive; for average stress less than 0, stress ratio Cases less than -1 and greater than 1 cannot be evaluated. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for analyzing the fatigue strength of a differential housing. This method and apparatus can improve the reliability of simulation, reduce the failure rate of parts, and improve work efficiency.

[0005] To achieve the above objectives, embodiments of the present invention provide a method and apparatus for fatigue strength analysis of a differential housing, comprising: Identify the loading position where the load is applied to the differential housing; Based on the confirmed loading location, perform FEA analysis to obtain stress contour plots; Select the critical point in the stress cloud diagram; The critical points are linearly scaled under different working conditions to obtain the corresponding maximum and minimum stresses; The fatigue limit and maximum allowable stress are obtained from the modified equal-life fatigue curve. The SN curve is obtained by fitting the fatigue limit and the maximum allowable stress. The cumulative damage is calculated based on the fitted SN curve.

[0006] Optionally, identifying the loading location where a load is applied to the differential housing includes: The loading position is determined according to the preset angle of load application, wherein the angle of load application is 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315°.

[0007] Optionally, selecting critical points in the stress cloud diagram includes: Select the point of maximum tensile stress in each of the stress cloud diagrams; In the remaining stress cloud diagrams, determine the maximum compressive stress point corresponding to the maximum tensile stress point; Select the point of maximum compressive stress in each of the stress cloud diagrams; In the remaining stress cloud diagrams, determine the maximum tensile stress point corresponding to the maximum tensile stress point.

[0008] Optionally, the critical point can be linearly scaled under different working conditions to obtain the corresponding maximum and minimum stresses, including: Keep the relative positions of the danger points unchanged.

[0009] Optionally, the fatigue limit and maximum allowable stress can be obtained from the modified equal-life fatigue curve, including: Draw the Haigh diagram according to formula (1). (1) in, The tensile strength of the differential housing is... The horizontal axis of the Haigh graph is... y is the vertical axis of the Haigh plot. The fatigue limit is defined in the Haigh diagram, and the fatigue limit value is 0.5. ; Draw rays in the Haigh diagram according to formulas (2) to (4). , , (2) , , (3) , , (4) in, The slope The stress ratio of the Haigh diagram; Rotate the Haigh graph counterclockwise by 45°, and adjust the horizontal axis. and vertical axis The central axis serves as the new longitudinal axis , will be with the vertical axis The vertical line serves as the new horizontal axis. To obtain the life fatigue curve to be corrected; Randomly select a point A in the life fatigue curve diagram to be corrected; Plot the constant life fatigue curves according to formulas (5) to (8). (5) (6) (7) (8) in, The line connecting point A to the origin. The angle between the ray and the ray in formula (4), For connecting lines On the horizontal axis Projection on The horizontal axis of the equal-life fatigue curve is [value]. The vertical axis represents the constant life fatigue curve. Connection point and point ( , in order to take lifespan as The lifespan line, and ; Connection point and , in order to take lifespan as Equal life line; According to formula (9), the connection point and points As a correction curve, (9) in, The yield strength of the differential housing; Lifespan is Equal lifetime line, correction curve, horizontal axis and vertical axis The region formed serves as the range of infinite fatigue life. Connection point and points The lifetime of the region with average stress less than 0 is taken as Equal life line; Connection point and , to serve as a correction curve for the region where the average stress is less than 0; The correction curve for the region where the average stress is less than 0, and the horizontal passing point. straight line, horizontal axis and vertical axis The region formed serves as the infinite fatigue life range of the region where the average stress is less than 0. Based on formulas (1) and (9), the inflection point coordinates (10), (11), and (12) of the infinite fatigue life range are determined.

[0010] (10) (11) (12) When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (13) and (14), respectively. (13) (14) in, The fatigue limit is mentioned above. The maximum allowable stress; When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (15) and (16), respectively. , (15) (16) When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (17) and (18), respectively. (17) (18) When the stress ratio or hour, The fatigue limit and maximum allowable force are determined according to formulas (19) and (20), respectively. (19) , (20).

[0011] Optionally, the analysis method includes: When it is necessary to quickly plot the fatigue limit and maximum allowable stress, determine the stress ratio. Scope; In stress ratio When the stress is greater than or equal to -1 and less than or equal to 1, and the maximum stress is greater than 0, the ray formed by the point of impact within the region and the origin is compared with the lifetime of... The intersection of the life lines is taken as the maximum allowable stress. The ray and the lifetime are The intersection of the lifespan lines is taken as the fatigue limit. ; In stress ratio When the value is less than -1 or greater than 1, the ray is compared with a lifetime of The intersection of the life lines is directed towards the vertical axis. The resulting projection serves as the fatigue limit. The ray and the lifetime are The intersection of the life lines is directed towards the vertical axis. The resulting projection is used as the maximum allowable stress. .

[0012] Optionally, the SN curve obtained by fitting the fatigue limit and the maximum allowable stress includes: According to the fatigue limit point ( ) and the maximum allowable stress point ( Determine the SN curve ,in, , .

[0013] Optionally, based on the fitted SN curve, the cumulative damage is calculated as follows: The cumulative damage is calculated according to formula (21). ,(twenty one) in, For the cumulative damage, This represents the actual number of cycles under operating conditions. The lifespan corresponding to the isochronous lifespan line closest to the point of application within the corrected infinite fatigue life range.

[0014] On the other hand, the present invention also provides a differential housing fatigue strength analysis apparatus, the apparatus including a processor configured to perform the analysis method as described above.

[0015] Through the above technical solution, the differential housing fatigue strength analysis method and apparatus provided by the present invention confirms the loading position where the load is applied to the differential housing, performs FEA analysis based on the confirmed loading position to obtain a stress cloud map, selects critical points in the stress cloud map, and linearly scales the critical points under different operating conditions to obtain the corresponding maximum and minimum stresses, obtains the fatigue limit and maximum allowable stress based on the modified equal-life fatigue curve, fits the obtained fatigue limit and maximum allowable stress to obtain the SN curve, and calculates the cumulative damage based on the fitted SN curve. This differential housing fatigue strength analysis method and apparatus modifies the equal-life fatigue curve, which can improve the reliability of the simulation and reduce the failure rate of the parts. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for analyzing the fatigue strength of a differential housing according to an embodiment of the present invention; Figure 2 This is an example diagram of the load-bearing position of the differential housing according to one embodiment of the present invention; Figure 3 This is a flowchart of selecting critical points in a stress cloud diagram according to a method for fatigue strength analysis of a differential housing based on an embodiment of the present invention. Figure 4 This is a flowchart of drawing an infinite fatigue life range according to a method for analyzing the fatigue strength of a differential housing according to an embodiment of the present invention. Figure 5 It is a Haigh diagram drawn according to formula (1) according to an embodiment of the present invention; Figure 6 It is a ray diagram drawn based on a Haigh diagram according to an embodiment of the present invention; Figure 7 This is a Haigh diagram rotated 45° according to one embodiment of the present invention; Figure 8 This is an equal-life fatigue curve diagram according to an embodiment of the present invention; Figure 9 This is a first-corrected equal-life fatigue curve diagram according to an embodiment of the present invention; Figure 10 This is a modified equal-life fatigue curve diagram according to one embodiment of the present invention; Figure 11 This is a flowchart illustrating the method for determining the fatigue limit and maximum allowable stress of a differential housing fatigue strength analysis according to an embodiment of the present invention. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0018] like Figure 1 The diagram shows a flowchart of a method for analyzing the fatigue strength of a differential housing according to an embodiment of the present invention. Figure 1 In this context, the method may include: In step S1, the loading position where the load is applied to the differential housing is confirmed; In step S2, FEA analysis is performed based on the confirmed loading position to obtain a stress contour map; In step S3, select the critical point in the stress cloud diagram; In step S4, the critical point is linearly scaled under different working conditions to obtain the corresponding maximum and minimum stresses; In step S5, the fatigue limit and maximum allowable stress are obtained based on the modified equal-life fatigue curve. In step S6, the SN curve is obtained by fitting the fatigue limit and the maximum allowable stress; In step S7, the cumulative damage is calculated based on the fitted SN curve.

[0019] In such Figure 1 In the method shown, step S1 can be used to determine the loading position for applying a load to the differential housing. Considering that the stiffness of the differential housing is not uniform in the circumferential direction, the loading position for applying a load can be determined by sequentially calculating the loading positions to confirm the angle at which the load is applied. Therefore, in actual operation, this angle can vary depending on the shape of the differential housing. In one example of the invention, when the shape of the differential housing is as follows... Figure 2 In the case shown, the angle at which the load is applied can be, for example, 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315°.

[0020] Step S2 can be used to perform FEA analysis based on the confirmed loading location to obtain a stress contour map. FEA (Finite Element Analysis) is a method of simulating a real physical system (geometry and load conditions) using mathematical approximations. This method uses simple, interacting elements (i.e., units) to approximate a real system with an infinite number of unknowns using a finite number of unknowns. Using this method, combined with the load location calculated in step S1, a stress contour map representing the stress characteristics of the differential housing can be obtained.

[0021] Step S3 can be used to select a critical point in the stress cloud diagram. While there are many methods known to those skilled in the art for selecting this critical point from the stress cloud diagram, in one example of the present invention, considering the simplicity of the method for selecting the critical point, the method may include, for example... Figure 3 The steps are shown. Specifically: In step S11, the point of maximum tensile stress is selected in each stress cloud diagram; In step S12, the maximum compressive stress point corresponding to the maximum tensile stress point is determined in the remaining stress cloud diagrams; In step S13, the point of maximum compressive stress is selected in each stress cloud diagram; In step S14, the maximum tensile stress point corresponding to the maximum tensile stress point is determined in the remaining stress cloud diagrams.

[0022] In one example of the present invention, step S11, obtaining the point of maximum tensile stress, can be achieved by directly selecting the point with the largest tensile stress value in the FEA simulation software. Based on this selected point, the corresponding point of maximum compressive stress (the points of maximum compressive stress and maximum tensile stress have the same number) can be further selected from the remaining stress cloud diagrams according to the selected point's number. The methods for selecting the points of maximum compressive stress and maximum tensile stress in steps S13 and S14 are similar to those in steps S11 and S12, and therefore will not be described further.

[0023] Step S4 can be used to linearly scale the critical points under different working conditions to obtain the corresponding maximum and minimum stresses, so as to extend the stress distribution state under a single working condition to multiple working conditions. To ensure that the extended stress distribution state retains the characteristics of the original stress distribution state, the relative positions of each critical point can be kept unchanged during linear scaling.

[0024] Step S5 can determine the modified equal-life fatigue curve. While there are various methods known to those skilled in the art for determining this modified equal-life fatigue curve, in one example of the present invention, considering the accuracy requirements of fatigue limit and maximum allowable stress, the method for determining the modified equal-life fatigue curve may include, for example... Figure 4 The steps are shown. Specifically: In step S20, a Haigh diagram is drawn according to formula (1). (1) in, The tensile strength of the differential housing The horizontal axis of the Haigh plot is... y is the vertical axis of the Haigh plot. Let be the fatigue limit in the Haigh diagram, and let the fatigue limit value be 0.5. ; In step S21, rays are drawn on the Haigh diagram according to formulas (2) to (4). , , (2) , , (3) , , (4) in, The slope The stress ratio in the Haigh diagram; Rotate the Haigh graph counterclockwise by 45° and adjust the horizontal axis. and vertical axis The central axis serves as the new longitudinal axis , will be with the vertical axis The vertical line serves as the new horizontal axis. To obtain the life fatigue curve to be corrected; In step S22, a point A is randomly selected from the fatigue curve diagram of the equal life to be corrected; In step S23, equal-life fatigue curves are plotted according to formulas (5) to (8). (5) (6) (7) (8) in, The line connecting point A to the origin. The angle between the ray and the ray in formula (4), For connecting lines On the horizontal axis Projection on The horizontal axis of the equal-life fatigue curve is [value]. The vertical axis represents the constant life fatigue curve. In step S24, the connection point and point ( , in order to take lifespan as The lifespan line, and ; In step S25, the connection point and , in order to take lifespan as Equal life line; In step S26, according to formula (9), the connection point and points As a correction curve, (9) in, The yield strength of the differential housing; In step S27, the lifetime is Equal lifetime line, correction curve, horizontal axis and vertical axis The region formed serves as the range of infinite fatigue life. In step S28, the connection point and points The lifetime of the region with average stress less than 0 is taken as Equal life line; In step S29, the connection point and , to serve as a correction curve for the region where the average stress is less than 0; In step S30, the correction curve for the region with average stress less than 0 and the horizontal passing point are... straight line, horizontal axis and vertical axis The region formed is considered as the infinite fatigue life range of the region where the average stress is less than 0.

[0025] In such Figure 4 In the method shown, the Haigh diagram can be used to represent the relationship between the tensile strength and fatigue limit of the differential housing. In one example of the invention, the Haigh diagram can be as follows: Figure 5 As shown.

[0026] Step S21 can be performed by drawing rays in the Haigh diagram according to formulas (2) to (4), which can be used to represent the stress ratio of the differential housing. In one example of the present invention, the Haigh diagram after drawing rays can be as follows: Figure 6 As shown.

[0027] Step S22 can be used to randomly select a point A in the fatigue curve diagram of the lifespan to be corrected. In one example of the present invention, the Haigh diagram after selecting point A can be as follows: Figure 7 As shown.

[0028] Step S23 can be used to draw an equal-life fatigue curve according to formulas (5) to (8), thereby facilitating subsequent correction of the equal-life fatigue curve. In one example of the present invention, the equal-life fatigue curve can be as follows: Figure 8 As shown.

[0029] Steps S23 and S27 are used to perform a first correction on the equal-life fatigue curve to obtain a corrected curve. In one example of the present invention, the corrected curve after the first correction may be as follows: Figure 9 As shown.

[0030] Steps S28 to S30 are used to perform a second correction on the modified curve to obtain a corrected equal-life fatigue curve. In one example of the present invention, the corrected equal-life fatigue curve may be as follows: Figure 10 As shown.

[0031] On the other hand, step S5 can also be used to obtain the fatigue limit and maximum allowable stress based on the modified equal-life fatigue curve. Specifically, the method for obtaining the fatigue limit and maximum allowable stress may include, for example... Figure 11 The steps are shown. Specifically: In step S40, the inflection point coordinates (10), (11), and (12) of the infinite fatigue life range are determined according to formulas (1) and (9).

[0032] (10) (11) (12) In step S41, the fatigue limit and maximum allowable stress are determined according to formulas (13) to (20). When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (13) and (14), respectively. (13) (14) in, The fatigue limit is mentioned above. The maximum allowable stress; When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (15) and (16), respectively. , (15) (16) When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (17) and (18), respectively. (17) (18) When the stress ratio or hour, The fatigue limit and maximum allowable force are determined according to formulas (19) and (20), respectively. (19) , (20).

[0033] Furthermore, in situations where it is not necessary to precisely obtain the fatigue limit and maximum allowable stress, from such Figure 10 The method for obtaining the fatigue limit and maximum allowable stress using the modified equal-life fatigue curve shown can also be achieved by first determining the stress ratio. The range, and then for the stress ratio The range is used to determine the specific value. Specifically, in terms of stress ratio... When the stress is greater than or equal to -1 and less than or equal to 1, and the maximum stress is greater than 0, the ray formed by the point of impact within the region and the origin is compared with the lifetime of... The intersection of the life lines is taken as the maximum allowable stress. The ray and the lifetime are The intersection of the lifespan lines is taken as the fatigue limit. .

[0034] In stress ratio When the value is less than -1 or greater than 1, the ray is compared with a lifetime of The intersection of the life lines is directed towards the vertical axis. The resulting projection serves as the fatigue limit. The ray and the lifetime are The intersection of the life lines is directed towards the vertical axis. The resulting projection is used as the maximum allowable stress. .

[0035] Step S6 can be used to fit the SN curve based on the fatigue limit and the maximum allowable stress. Specifically, it can be based on the fatigue limit point ( ) and the maximum allowable stress point ( Determine the SN curve ,in, , .

[0036] Step S7 can be to calculate the cumulative damage based on the fitted SN curve. Specifically, the cumulative damage can be calculated according to formula (21). ,(twenty one) in, For cumulative damage, This represents the actual number of cycles under operating conditions. The lifespan corresponding to the isochronous lifespan line closest to the point of application within the corrected infinite fatigue life range.

[0037] On the other hand, the present invention also provides a differential housing fatigue strength analysis apparatus, the apparatus including a processor configured to perform the analysis method as described above.

[0038] Through the above technical solution, the differential housing fatigue strength analysis method and apparatus provided by the present invention identifies the loading position where the load is applied to the differential housing, performs FEA analysis based on the identified loading position to obtain a stress cloud map, selects critical points in the stress cloud map, and linearly scales the critical points under different operating conditions to obtain the corresponding maximum and minimum stresses. The fatigue limit and maximum allowable stress are obtained based on the corrected equal-life fatigue curve, and the SN curve is fitted based on the fatigue limit and maximum allowable stress. The cumulative damage is calculated based on the fitted SN curve. This differential housing fatigue strength analysis method and apparatus corrects the equal-life fatigue curve, which can improve the reliability of the simulation and reduce the failure rate of parts.

[0039] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0040] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1A device that provides the functions specified in one or more boxes.

[0041] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0042] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0043] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0044] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0045] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0046] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0047] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0048] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for fatigue strength analysis of a differential housing, characterized in that, The analytical method includes: Identify the loading position where the load is applied to the differential housing; Based on the confirmed loading location, perform FEA analysis to obtain stress contour plots; Select the critical point in the stress cloud diagram; The critical points are linearly scaled under different working conditions to obtain the corresponding maximum and minimum stresses; The fatigue limit and maximum allowable stress are obtained from the modified equal-life fatigue curve. The SN curve is obtained by fitting the fatigue limit and the maximum allowable stress. Calculate the cumulative damage based on the fitted SN curve; The fatigue limit and maximum allowable stress are obtained from the modified equal-life fatigue curve, including: Draw the Haigh diagram according to formula (1). ，（1） in, The tensile strength of the differential housing is... The horizontal axis of the Haigh graph is... y is the vertical axis of the Haigh plot. The fatigue limit is defined in the Haigh diagram, and the fatigue limit value is 0.

5. ; Draw rays in the Haigh diagram according to formulas (2) to (4). ， ， ，（2） ， ， ，（3） ， ， ，（4） in, The slope The stress ratio of the Haigh diagram; Rotate the Haigh graph counterclockwise by 45°, and adjust the horizontal axis. and vertical axis The central axis serves as the new longitudinal axis , will be with the vertical axis The vertical line serves as the new horizontal axis. To obtain the life fatigue curve to be corrected; Randomly select a point A in the life fatigue curve diagram to be corrected; Plot the constant life fatigue curves according to formulas (5) to (8). ，（5） ，（6） ，（7） ，（8） in, The line connecting point A to the origin. The angle between the ray and the ray in formula (4), For connecting lines On the horizontal axis The projection on The horizontal axis of the equal-life fatigue curve is denoted as . The vertical axis represents the constant life fatigue curve. Connection point and point ( , in order to take lifespan as The lifespan line, and ; Connection point and , in order to take lifespan as Equal life line; According to formula (9), the connection point and points As a correction curve, ，（9） in, The yield strength of the differential housing; Lifespan is Equal lifetime line, correction curve, horizontal axis and vertical axis The region formed serves as the range of infinite fatigue life. Connection point and points The lifetime of the region with average stress less than 0 is taken as Equal life line; Connection point and , to serve as a correction curve for the region where the average stress is less than 0; The correction curve for the region where the average stress is less than 0, and the horizontal passing point. straight line, horizontal axis and vertical axis The region formed serves as the infinite fatigue life range of the region where the average stress is less than 0. Based on formulas (1) and (9), the inflection point coordinates (10), (11), and (12) of the infinite fatigue life range are determined. ，（10） ，（11） ，（12） When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (13) and (14), respectively. ，（13） ，（14） in, The fatigue limit is mentioned above. The maximum allowable stress; When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (15) and (16), respectively. ， （15） ，（16） When the stress ratio hour, The fatigue limit and maximum allowable force are determined according to formulas (17) and (18), respectively. ，（17） ，（18） When the stress ratio or hour, The fatigue limit and maximum allowable force are determined according to formulas (19) and (20), respectively. ，（19） ，（20）。 2. The analytical method according to claim 1, characterized in that, The loading locations where loads are applied to the differential housing include: The loading position is determined according to the preset angle of load application, wherein the angle of load application is 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315°.

3. The analytical method according to claim 1, characterized in that, The selection of critical points in the stress cloud diagram includes: Select the point of maximum tensile stress in each of the stress cloud diagrams; In the remaining stress cloud diagrams, determine the maximum compressive stress point corresponding to the maximum tensile stress point; Select the point of maximum compressive stress in each of the stress cloud diagrams; In the remaining stress cloud diagrams, determine the maximum tensile stress point corresponding to the maximum tensile stress point.

4. The analytical method according to claim 1, characterized in that, The critical points are linearly scaled under different operating conditions to obtain the corresponding maximum and minimum stresses, including: Keep the relative position of the danger point unchanged.

5. The analytical method according to claim 1, characterized in that, The analytical method includes: When it is necessary to quickly plot the fatigue limit and maximum allowable stress, determine the stress ratio. Scope; Under stress When the ratio is greater than or equal to -1 and less than or equal to 1, and the maximum stress is greater than 0, the ray formed by the point of impact within the region and the origin is compared with the ray with a lifetime of The intersection of the life lines is taken as the maximum allowable stress. The ray and the lifetime are The intersection of the lifespan lines is taken as the fatigue limit. ; In stress ratio When the value is less than -1 or greater than 1, the ray is compared with a lifetime of The intersection of the life lines is directed towards the vertical axis. The resulting projection serves as the fatigue limit. The ray and the lifetime are The intersection of the life lines is directed towards the vertical axis. The resulting projection is used as the maximum allowable stress. .

6. The analytical method according to claim 1, characterized in that, The SN curves obtained by fitting the fatigue limit and maximum allowable stress include: According to the fatigue limit point ( ) and the maximum allowable stress point ( Determine the SN curve ,in, , .

7. The analytical method according to claim 1, characterized in that, Based on the fitted SN curve, the cumulative damage is calculated as follows: The cumulative damage is calculated according to formula (21). ，（21） in, For the cumulative damage, This represents the actual number of cycles under operating conditions. The lifespan corresponding to the isochronous lifespan line closest to the point of application within the corrected infinite fatigue life range.

8. A fatigue strength analysis device for a differential housing, characterized in that, The device includes a processor configured to perform the analysis method as described in any one of claims 1 to 7.

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