Method for analyzing strength of automobile spare tire lifter bracket

Abstract

The present application relates to a kind of automobile spare tire elevator support strength analysis method, comprising determining analysis working condition;Determine the maximum acceleration load that spare tire elevator system is subjected to under static strength condition;Determine the vertical acceleration load that spare tire elevator system is subjected to under vertical fatigue condition;Simulate fixed base and wheel hub, frame, spare tire elevator upper support, elevator's wheel axle, spare tire elevator lower support;Combined with actual establishment the contact relationship of each component;According to actual preset chain initial tension, calculate the contact pressure intensity of spare tire elevator lower support and wheel hub under chain tensioning condition;Determine whether the preset tension of chain is reasonable;Calculate the stress distribution of spare tire elevator support under static strength condition;Determine whether support meets static strength requirement;Calculate the stress distribution of spare tire elevator support under vertical fatigue condition;Obtain support fatigue safety factor;Determine whether support meets fatigue strength requirement.Method is detailed, objective, and checking efficiency is high.

Description

Technical Field

[0001] This invention belongs to the technical field of spare tire lifter brackets, and specifically relates to a method for strength analysis of automotive spare tire lifter brackets. Background Technology

[0002] A spare tire lifter is a mechanical device that secures and controls the raising and lowering of the spare tire. The spare tire lifter bracket refers to the metal support that connects the spare tire lifter to the vehicle frame or the spare tire; it is mostly a thin-walled metal structure. The upper bracket of the spare tire lifter connects to the vehicle frame, and the lower bracket clamps and secures the spare tire to the frame via a tensioned chain. The structural strength of the spare tire lifter bracket plays a crucial role in ensuring the safe and reliable fixation of the spare tire to the vehicle.

[0003] Currently, there is no method for finite element simulation analysis of spare tire lifter brackets. This results in insufficient clarity and detail in the analysis conditions and specific analysis methods for this type of bracket, making it impossible to objectively analyze and predict the static strength and fatigue strength performance of this type of bracket structure. In particular, when the chain pre-tension is too low, the spare tire may become loose, wobble, and generate noise during driving. Furthermore, the lower bracket of the spare tire lifter is prone to damage due to continuous friction and impact with the wheel hub, affecting the strength of the spare tire lifter bracket and the reliability of the system. The prediction of the structural strength performance of the spare tire lifter bracket is currently completed during vehicle road durability testing, which is a lengthy process. Moreover, since the road conditions used in road tests vary, the prediction results contain a certain degree of randomness and chance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for strength analysis of automotive spare tire lifter brackets, so as to solve the problem of rapid and reliable finite element simulation analysis of spare tire lifter brackets.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for strength analysis of a car spare tire lifter bracket includes the following steps:

[0007] A. Determine the analysis conditions based on actual user usage and testing data;

[0008] B. Based on the vehicle load, axle load transfer, and previous load data, determine the maximum acceleration load on the spare tire lifter system under static strength conditions; at the same time, obtain the preset initial chain tension of the spare tire lifter system.

[0009] C. Based on the vehicle load, axle load transfer, and previous load data, determine the vertical acceleration load on the spare tire lifter system under vertical fatigue conditions.

[0010] D. Use three-dimensional elements to simulate the fixed base and wheel hub. Since the specific shape and elasticity of the spare tire body have little impact on the strength of the analyzed bracket, the mass of the spare tire body is equivalently assigned to the wheel hub, and the frame is simulated using two-dimensional elements.

[0011] E. Use two-dimensional units to simulate the upper support of the spare tire lifter, use three-dimensional units to simulate the wheel axle of the spare tire lifter, and use two-dimensional units to simulate the lower support of the spare tire lifter.

[0012] F. Locate the tangent point between the chain tensioning section and the axle; locate the center point of the bolt hole on the lower support of the spare tire lifter, and establish a spring unit at this point to simulate the helical spring at the bottom of the spare tire lifter. The stiffness of the spring unit is given according to the actual stiffness of the helical spring; use rope units to simulate the chain tensioning section, connect the spring unit at the tangent point between the chain tensioning section and the axle and the center point of the bolt hole on the lower support of the spare tire lifter, ignoring the natural hanging part of the chain, and connect the spring unit to the periphery of the center bolt hole on the lower support of the spare tire lifter using rigid units;

[0013] G. Establish the contact relationships of each component according to the actual situation;

[0014] H. Apply preload to the rope unit according to the actual preset initial chain tension and calculate the chain tension condition. Analyze whether the contact pressure between the lower bracket of the spare tire lifter and the wheel hub is greater than the threshold. If it is greater than the threshold, the preset chain tension is reasonable; if it is less than the threshold, the preset chain tension is unreasonable, and the preset tension needs to be increased and this step recalculated.

[0015] I. Under static strength conditions, based on the analysis in step H, apply the acceleration load from step B to the model and calculate the stress distribution of the spare tire lifter bracket.

[0016] J. Take the stress distribution of the spare tire lifter bracket under each static load condition obtained in step I, and refer to the mechanical properties of the bracket material. If the maximum stress on the spare tire lifter bracket is less than the threshold, the bracket is determined to meet the static strength requirements; otherwise, if the maximum stress on the spare tire lifter bracket is greater than the threshold, the bracket is determined to not meet the static strength requirements.

[0017] K. Under vertical fatigue conditions, based on the analysis in step H, apply the acceleration load from step C to the model and calculate the stress distribution of the spare tire lifter bracket.

[0018] L. Using the stress distribution obtained in step K as the upper and lower limits respectively, input them into the fatigue calculation software, and refer to the mechanical properties of the support material to obtain the fatigue safety factor of the support; if the fatigue safety factor is greater than the threshold, the fatigue strength of the support is determined to meet the requirements; otherwise, if the fatigue safety factor is less than the threshold, the fatigue strength of the support is determined to not meet the requirements.

[0019] Further, step A specifically includes the following steps:

[0020] A1. Define the static strength conditions of the spare tire lifter bracket, including: vertical, longitudinal, and lateral conditions;

[0021] A2. Define the fatigue strength condition of the spare tire lifter bracket, namely: fatigue condition in the vertical direction.

[0022] Further, step B specifically includes the following steps:

[0023] B1. Determine the maximum acceleration load on the spare tire lifter bracket system under vertical operating conditions;

[0024] B2. Determine the maximum acceleration load on the spare tire lifter support system under longitudinal working conditions;

[0025] B3. Determine the maximum acceleration load on the spare tire lifter support system under lateral operating conditions.

[0026] Further, step C specifically includes the following steps:

[0027] C1. Determine the maximum acceleration load in the vertical upward direction that the spare tire lifter support system is subjected to under vertical fatigue conditions.

[0028] C2. Determine the maximum downward acceleration load that the spare tire lifter support system experiences under vertical fatigue conditions.

[0029] Further, in step E, the upper support of the spare tire lifter is the front and rear housing parts of the spare tire lifter.

[0030] Further, in step F, the tangent point is the tangent point between the tensioned part of the chain and the wheel axle; the simulated chain is specifically a rope unit simulating the tensioned part of the chain; the connected tangent point is the tangent point connecting the tensioned part of the chain and the wheel axle.

[0031] Further, step I specifically includes the following steps:

[0032] I1. Vertical working condition: Apply the acceleration load determined in step B1 to the system and calculate the stress distribution of the support.

[0033] I2. Longitudinal working condition: Apply the acceleration load determined in step B2 to the system and calculate the stress distribution of the support.

[0034] I3. Lateral load case: Apply the acceleration load determined in step B3 to the system and calculate the stress distribution of the support.

[0035] Furthermore, step K specifically includes the following steps:

[0036] K1, Vertical fatigue upward working condition, apply the acceleration load determined in step C1 to the system, and calculate the stress distribution of the support;

[0037] K2, Vertical fatigue downward working condition, apply the acceleration load determined in step C2 to the system, and calculate the stress distribution of the support.

[0038] Furthermore, the stress distribution of the support obtained in steps K1 and K2 in step K is taken as the upper and lower limits, respectively.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] This invention discloses a strength analysis method for automotive spare tire lifter brackets, clarifying the finite element simulation analysis method for spare tire lifter brackets. It can clearly, comprehensively, and objectively predict the static and fatigue strength performance of this type of bracket. The method considers the impact of insufficient chain tension on the structural strength and system reliability of the bracket. This method can significantly improve the efficiency of verifying the structural strength performance of spare tire lifter brackets and shorten the cycle; at the same time, it can largely replace testing, avoiding the randomness and chance of road test results. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 Spare tire lifter system structure diagram;

[0043] Figure 2 Spare tire lifter structural diagram;

[0044] Figure 3 Finite element model diagram of the spare tire lifter system;

[0045] Figure 4 Finite element model of spare tire lifter;

[0046] Figure 5 Flowchart for strength analysis of spare tire lifter bracket.

[0047] In the diagram: 1. Frame; 2. Spare tire body; 3. Wheel hub; 4. Mounting base; 5. Upper bracket of spare tire lifter; 6. Chain tensioning part; 7. Lower bracket of spare tire lifter; 8. Chain base; 9. Chain hanging part; 10. Coil spring; 11. Axle; 12. Rope unit; 13. Spring unit. Detailed Implementation

[0048] The present invention will be further described below with reference to embodiments:

[0049] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0050] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0051] like Figures 1-5 As shown, the strength analysis method for the automotive spare tire lifter bracket of the present invention includes the following steps:

[0052] 1. Determine the analysis conditions based on actual user usage and testing.

[0053] 11. Define the static strength conditions of the spare tire lifter bracket, including: vertical, longitudinal, and lateral conditions;

[0054] 12. Define the fatigue strength condition of the spare tire lifter bracket, namely: fatigue condition in the vertical direction.

[0055] 2. Based on the vehicle load, axle load transfer, and previous load data, determine the maximum acceleration load on the spare tire lifter system under static strength conditions.

[0056] 21. Determine the maximum acceleration load on the spare tire lifter support system under vertical operating conditions;

[0057] 22. Determine the maximum acceleration load on the spare tire lifter support system under longitudinal operating conditions;

[0058] 23. Determine the maximum acceleration load on the spare tire lifter support system under lateral conditions.

[0059] At the same time, the initial chain tension preset by the spare tire lifter system is obtained.

[0060] 3. Based on the vehicle load, axle load transfer, and previous load data, determine the vertical acceleration load on the spare tire lifter system under vertical fatigue conditions.

[0061] 31. Determine the maximum upward acceleration load that the spare tire lifter support system experiences under vertical fatigue conditions.

[0062] 32. Determine the maximum downward acceleration load that the spare tire lifter support system experiences under vertical fatigue conditions.

[0063] 4. The fixed base 4 and wheel hub 3 are simulated using three-dimensional elements. Since the specific shape and elasticity of the spare tire body 2 have little impact on the strength of the analyzed bracket, the mass of the spare tire body 2 is equivalently assigned to the wheel hub 3. The frame 1 is simulated using two-dimensional elements.

[0064] 5. Simulate the upper support 5 (front and rear housings of the spare tire lifter) using two-dimensional elements. Simulate the wheel axle 11 of the spare tire lifter using three-dimensional elements. Simulate the lower support 7 of the spare tire lifter using two-dimensional elements.

[0065] 6. Locate the tangent point between the chain tensioning section 6 and the axle 11; locate the center point of the bolt hole on the lower support 7 of the spare tire lifter, and establish a spring unit 13 at this point to simulate the helical spring 10 at the bottom of the spare tire lifter. The stiffness of the spring unit 13 is given according to the actual stiffness of the helical spring 10; use a rope unit 12 to simulate the chain tensioning section 6, and connect the spring unit 13 at the tangent point between the chain tensioning section 6 and the axle 11 and the center point of the bolt hole on the lower support 7 of the spare tire lifter, ignoring the natural drooping portion 9 of the chain. Connect the spring unit 13 to the periphery of the center bolt hole on the lower support 7 of the spare tire lifter using rigid units.

[0066] 7. Establish the contact relationships of each component according to the actual situation.

[0067] 8. Apply preload to rope unit 12 according to the actual preset initial chain tension. Calculate the chain tension condition and analyze whether the contact pressure between the lower support 7 of the spare tire lifter and the wheel hub 3 is greater than the threshold. If it is greater than the threshold, the preset chain tension is reasonable; if it is less than the threshold, the preset chain tension is unreasonable, and the preset tension needs to be increased and this step recalculated.

[0068] 9. Under static strength conditions, based on the analysis in step 8, apply the acceleration load from step 2 to the model and calculate the stress distribution of the spare tire lifter bracket.

[0069] 91. In the vertical working case, apply the acceleration load determined in step 21 to the system and calculate the stress distribution of the support.

[0070] 92. Longitudinal working condition: Apply the acceleration load determined in step 22 to the system and calculate the stress distribution of the support.

[0071] 93. Lateral load case: Apply the acceleration load determined in step 23 to the system and calculate the stress distribution of the support.

[0072] 10. Based on the stress distribution of the spare tire lifter bracket under each static load condition obtained in step 9, and referring to the mechanical properties of the bracket material, if the maximum stress on the spare tire lifter bracket is less than the threshold, then the bracket is determined to meet the static strength requirements; otherwise, if the maximum stress on the spare tire lifter bracket is greater than the threshold, then the bracket is determined to not meet the static strength requirements.

[0073] 11. Under vertical fatigue conditions, based on the analysis in step 8, apply the acceleration load from step 3 to the model and calculate the stress distribution of the spare tire lifter bracket.

[0074] 111. Under the vertical fatigue upward working condition, apply the acceleration load determined in step 31 to the system and calculate the stress distribution of the support;

[0075] 112. Under the vertical fatigue downward condition, apply the acceleration load determined in step 32 to the system and calculate the stress distribution of the support.

[0076] 12. Using the stress distributions of the support obtained in steps 111 and 112 of step 11 as the upper and lower limits, respectively, input them into the fatigue calculation software. Referring to the mechanical properties of the support material, obtain the fatigue safety factor of the support. If the fatigue safety factor is greater than the threshold, the fatigue strength of the support is deemed to meet the requirements; conversely, if the fatigue safety factor is less than the threshold, the fatigue strength of the support is deemed not to meet the requirements.

[0077] The strength analysis method for automotive spare tire lifters of the present invention has the following advantages:

[0078] 1. Working conditions: Static strength and fatigue strength working conditions were considered. The static strength working condition includes three directions: vertical, longitudinal, and lateral; the fatigue strength working condition considers the vertical direction.

[0079] 2. Load considerations: The load considerations for each working condition include not only acceleration load but also the impact of the chain's pre-set tension load on the structural strength of the spare tire lifter bracket.

[0080] 3. Modeling: Two-dimensional elements were used to simulate the spare tire lifter bracket and the frame 1; three-dimensional elements were used to simulate the fixed base 4 and the wheel hub 3, with the spare tire mass being equivalently represented on the wheel hub 3. Spring elements 13 were used to simulate the coil spring 10, with stiffness parameters given according to actual conditions. The spring elements 13 were connected to the periphery of the central bolt hole of the lower bracket 7 of the spare tire lifter using rigid elements. Rope elements 12 were used to simulate the chain tensioning part 6, ignoring the natural drooping part 9 of the chain. The two ends of the rope element 12 were the tangent points of the chain tensioning part 6 and the axle 11, and the center point of the bolt hole of the lower bracket 7 of the spare tire lifter, respectively. The preload of the rope element 12 was given according to the preset chain tension.

[0081] 4. Analysis and evaluation:

[0082] (1) Obtain the contact pressure between the lower bracket 7 of the spare tire lifter and the wheel hub 3 under the chain tensioning condition. If the contact pressure is greater than the threshold, the preset tension of the chain is reasonable. If the contact pressure is less than the threshold, the preset tension of the chain is unreasonable and the preset tension needs to be increased and this step needs to be recalculated.

[0083] (2) Under static strength conditions, obtain the stress distribution of the spare tire lifter bracket. Referring to the mechanical properties of the bracket material, if the maximum stress on the spare tire lifter bracket is less than the threshold, the bracket is determined to meet the static strength requirements; otherwise, if the maximum stress on the spare tire lifter bracket is greater than the threshold, the bracket is determined to not meet the static strength requirements.

[0084] (3) Under fatigue strength conditions, obtain the stress distribution of the spare tire lifter bracket under vertical fatigue upward and vertical fatigue downward conditions. Use these two stress distributions as the upper and lower limits, respectively, and input them into the fatigue calculation software. Refer to the mechanical properties of the bracket material to obtain the fatigue safety factor of the bracket. If the fatigue safety factor is greater than the threshold, the fatigue strength of the bracket is determined to meet the requirements; otherwise, if the fatigue safety factor is less than the threshold, the fatigue strength of the bracket is determined to not meet the requirements.

[0085] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for strength analysis of a car spare tire lifter bracket, characterized in that, Includes the following steps: A. Determine the analysis conditions based on actual user usage and testing. B. Based on the vehicle load, axle load transfer, and previous load data, determine the maximum acceleration load on the spare tire lifter system under static strength conditions; at the same time, obtain the preset initial chain tension of the spare tire lifter system. C. Based on the vehicle load, axle load transfer, and previous load data, determine the vertical acceleration load on the spare tire lifter system under vertical fatigue conditions. D. Use three-dimensional units to simulate the fixed base (4) and the wheel hub (3). Since the specific shape and elasticity of the spare tire body (2) have little impact on the strength of the analyzed bracket, the mass of the spare tire body (2) is equivalently assigned to the wheel hub (3), and the frame (1) is simulated using two-dimensional units. E. Use two-dimensional units to simulate the upper support of the spare tire lifter (5), use three-dimensional units to simulate the wheel axle of the spare tire lifter (11), and use two-dimensional units to simulate the lower support of the spare tire lifter (7). F. Locate the tangent point between the chain tensioning part (6) and the wheel axle (11); locate the center point of the bolt hole of the lower bracket (7) of the spare tire lifter, and establish a spring unit (13) at this point to simulate the helical spring (10) at the bottom of the spare tire lifter. The stiffness of the spring unit (13) is given according to the actual stiffness of the helical spring (10); use a rope unit (12) to simulate the chain tensioning part (6), connect the tangent point between the chain tensioning part (6) and the wheel axle (11) and the spring unit (13) at the center point of the bolt hole of the lower bracket (7) of the spare tire lifter, without considering the natural hanging part (9) of the chain, and connect the spring unit (13) to the periphery of the center bolt hole of the lower bracket (7) of the spare tire lifter with a rigid unit; G. Establish the contact relationships of each component according to the actual situation; H. Apply preload to the rope unit according to the actual preset initial chain tension, calculate the chain tensioning condition, and analyze whether the contact pressure between the lower bracket of the spare tire lifter and the wheel hub is greater than the threshold. If it is greater than the threshold, the preset chain tension is reasonable. If the tension is less than the threshold, the preset tension of the chain is unreasonable, and the preset tension needs to be increased and this step needs to be recalculated. I. Under static strength conditions, based on the analysis in step H, apply the acceleration load from step B to the model and calculate the stress distribution of the spare tire lifter bracket. J. Take the stress distribution of the spare tire lifter bracket under each static load condition obtained in step I, and refer to the mechanical properties of the bracket material. If the maximum stress on the spare tire lifter bracket is less than the threshold, the bracket is determined to meet the static strength requirements; otherwise, if the maximum stress on the spare tire lifter bracket is greater than the threshold, the bracket is determined to not meet the static strength requirements. K. Under vertical fatigue conditions, based on the analysis in step H, apply the acceleration load from step C to the model and calculate the stress distribution of the spare tire lifter bracket. L. Using the stress distribution obtained in step K as the upper and lower limits respectively, input them into the fatigue calculation software, and refer to the mechanical properties of the support material to obtain the fatigue safety factor of the support. If the fatigue safety factor is greater than the threshold, the fatigue strength of the stent is deemed to meet the requirements; conversely, if the fatigue safety factor is less than the threshold, the fatigue strength of the stent is deemed not to meet the requirements.

2. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that, Step A specifically includes the following steps: A1. Define the static strength conditions of the spare tire lifter bracket, including: vertical, longitudinal, and lateral conditions; A2. Define the fatigue strength condition of the spare tire lifter bracket, namely: fatigue condition in the vertical direction.

3. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that, Step B specifically includes the following steps: B1. Determine the maximum acceleration load on the spare tire lifter bracket system under vertical operating conditions; B2. Determine the maximum acceleration load on the spare tire lifter support system under longitudinal working conditions; B3. Determine the maximum acceleration load on the spare tire lifter support system under lateral operating conditions.

4. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that, Step C specifically includes the following steps: C1. Determine the maximum acceleration load in the vertical upward direction that the spare tire lifter support system is subjected to under vertical fatigue conditions. C2. Determine the maximum downward acceleration load that the spare tire lifter support system experiences under vertical fatigue conditions.

5. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that: Step E, the upper bracket (5) of the spare tire lifter is the front and rear housing parts of the spare tire lifter.

6. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that: Step F: The tangent point is the tangent point between the chain tensioning part (6) and the wheel axle (11); the simulated chain is specifically the rope unit (12) simulating the chain tensioning part (6); the tangent point is the tangent point connecting the chain tensioning part (6) and the wheel axle (11).

7. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that, Step I specifically includes the following steps: I1. Vertical working condition: Apply the acceleration load determined in step B1 to the system and calculate the stress distribution of the support. I2. Longitudinal working condition: Apply the acceleration load determined in step B2 to the system and calculate the stress distribution of the support. I3. Lateral load case: Apply the acceleration load determined in step B3 to the system and calculate the stress distribution of the support.

8. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that, Step K specifically includes the following steps: K1, Vertical fatigue upward working condition, apply the acceleration load determined in step C1 to the system, and calculate the stress distribution of the support; K2, Vertical fatigue downward working condition, apply the acceleration load determined in step C2 to the system, and calculate the stress distribution of the support.

9. The method for strength analysis of a car spare tire lifter bracket according to claim 1, characterized in that: The stress distributions of the support obtained in steps K1 and K2 of step K are taken as the upper and lower limits, respectively.

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