A positive design method for preventing the dislodging of a shock absorber sleeve

Abstract

The present application belongs to the technical field of vehicle simulation and relates to a positive design method for preventing the disengagement of a shock absorber sleeve; under the condition of defining the design target of the sleeve pull-out force, based on the test data of the sleeve pull-out force bench, in combination with the finite element model of the shock absorber fork, sleeve and bolt assembly, the real friction coefficient between the shock absorber fork and the sleeve is calibrated, the finite element model is corrected, the pull-out force of the sleeve is calculated based on the corrected finite element model by using the load displacement curve method, the bolt pre-tightening force is back calculated, the appropriate standard bolt is matched, the positive design is realized, the problem that the simulation result of the sleeve pull-out force is small and leads to design redundancy is solved, the problem that the simulation result of the sleeve pull-out force is large in simulation and leads to the disengagement of the sleeve in the vehicle test is solved, and the simulation result of the sleeve pull-out force is more accurate.

Description

Technical Field

[0001] This invention belongs to the technical field of vehicle simulation methods, specifically relating to a forward design method for preventing shock absorber sleeve detachment. Background Technology

[0002] After the shock absorber fork and sleeve are assembled and the bolts are pre-tightened, the sleeve should meet a certain pull-out force requirement, meaning that during the vehicle's lifespan, the sleeve should not detach from the shock absorber when the suspension bounces. The current design method involves designers using empirical matching of standard bolts based on the sleeve pull-out force load target, simulation engineers establishing a finite element model of the shock absorber, sleeve, and bolt assembly, inputting empirical values ​​of the friction coefficient between the shock absorber fork and sleeve, simulating various performance indicators such as sleeve pull-out force and static strength of the shock absorber assembly, and finally verifying the results through testing. However, the current simulation calculation and design method has two problems: 1. When simulating the sleeve pull-out force, the empirical friction coefficient is input, and the magnitude of the friction coefficient greatly affects the simulation results. If the friction coefficient is set too low in the simulation, the simulated sleeve pull-out force will be too low, leading to design redundancy in order to achieve the sleeve pull-out force design target; if the friction coefficient is set too high in the simulation, the simulated sleeve pull-out force will be too high, potentially causing the sleeve to detach during vehicle testing; 2. The design method based on empirical matching of standard bolts lacks a basis. Summary of the Invention

[0003] To overcome the above problems, this invention provides a forward design method for preventing shock absorber sleeve pull-out. Under the condition of clearly defining the design target for the shock absorber sleeve pull-out force, based on the results of bench tests on the sleeve pull-out force, and combined with the finite element model of the shock absorber fork, sleeve, and bolt assembly, the actual friction coefficient between the shock absorber fork and sleeve is calibrated. While correcting the finite element model, this data serves as an accumulation of friction coefficient data, continuously improving the virtual verification method for the shock absorber sleeve pull-out force. Based on the corrected finite element model of the shock absorber, sleeve, and bolt assembly, the load-displacement curve method is used to calculate the sleeve pull-out force. Using the sleeve pull-out force load as the design target, the bolt preload is calculated inversely. Based on the inversely calculated preload of the screw brush, a suitable standard bolt is matched to achieve the forward design.

[0004] A forward design method for preventing shock absorber sleeve detachment includes the following:

[0005] The first step is to define the target pull-out force load of the shock absorber sleeve.

[0006] Based on the measured load spectrum of the axial force of the shock absorber in the previous generation model, the peak value of the axial force on the shock absorber when the suspension bounces down is determined. The peak value of the load is multiplied by a safety factor of 1.2 to obtain the design load for the shock absorber to prevent pull-out, i.e., the design load of the cylinder pull-out force; or it is greater than 20 times the unsprung weight load of the newly developed model to obtain the design load for the shock absorber to prevent pull-out.

[0007] The second step is to establish a finite element model of the shock absorber fork, sleeve, and bolt assembly.

[0008] The third step is to build a test bench for the pull-out force of the damper sleeve and measure the pull-out force of the sleeve under different bolt preloads.

[0009] The fourth step is to adjust the friction coefficient between the sleeve and the shock absorber fork based on the finite element model of the shock absorber fork, sleeve and bolt assembly established in the second step, and simulate the sleeve pull-out force under different bolt preloads.

[0010] Fifth, compare the simulation results of the sleeve pull-out force in the fourth step with the test results in the third step, adjust the friction coefficient between the damper fork and the sleeve until the simulation results of the sleeve pull-out force in the fourth step are consistent with the test results in the third step, and record the calibrated true friction coefficient.

[0011] Step 6: Replace the sleeves and damper forks with different materials and repeat steps 2 to 5 to accumulate the true friction coefficients between the sleeves and damper forks of different materials, and correct the finite element model based on the true friction coefficients.

[0012] Step 7: Based on the modified finite element model, using the sleeve pull-out force design load obtained in Step 1 as the target, simulate the bolt preload required when the sleeve pull-out force is the target load.

[0013] Step 8: Match a suitable standard bolt based on the bolt preload obtained from the simulation;

[0014] After matching the standard bolts, apply bolt preload to the finite element model of the shock absorber fork, sleeve and bolt assembly. In addition to verifying whether the sleeve pull-out force meets the requirements, it can also further verify whether the shock absorber fork meets the strength requirements.

[0015] The ninth step is to conduct bench tests and vehicle load-bearing system durability tests.

[0016] In step one, the measured load spectrum of the axial force of the shock absorber of the previous generation model was obtained by simulation based on the whole vehicle virtual test field technology.

[0017] In step three, six sets of shock absorber fork, sleeve and bolt assembly samples are designed. In the six sets of samples, the sleeve and shock absorber fork hole diameter interference of each set of assemblies are consistent, the bolt preload of each pair of assemblies is consistent, and the values ​​of the three bolt preloads are different. The sleeve pull-out force under different bolt preloads is measured by bench test.

[0018] In step four, the bolt preload torque is set to 180 NM, 190 NM, and 200 NM respectively. The lower point of the damper fork is constrained, and a forced displacement is applied to the upper point of the sleeve along the axial direction of the damper. The simulation yields the reaction force-displacement relationship curve with the displacement of the upper point of the sleeve as the abscissa and the sleeve pull-out force as the ordinate under different bolt preload torques.

[0019] In the sixth step, the finite element model is modified by replacing the friction coefficient between the sleeve and the damper fork in the finite element model with the actual friction coefficient obtained.

[0020] The method for obtaining the bolt preload required in the seventh step is as follows: After the friction coefficient between the sleeve and the damper fork is corrected to the true friction coefficient, a bolt preload is first applied, and then a sleeve pull-out force is obtained through simulation. When this pull-out force is less than the target load, a larger bolt preload is applied, and the sleeve pull-out force is obtained through simulation again, until the sleeve pull-out force obtained by simulation is consistent with the target load. The corresponding bolt preload is the required bolt preload.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] This invention, under the condition of clearly defining the design target of the shock absorber sleeve pull-out force, uses bench test data of the sleeve pull-out force and combines it with the finite element model of the shock absorber fork, sleeve and bolt assembly to calibrate the true friction coefficient between the shock absorber fork and sleeve. While correcting the finite element model, it also accumulates friction coefficient data to continuously improve the virtual verification method of the shock absorber sleeve pull-out force. Based on the corrected finite element model of the shock absorber, sleeve and bolt assembly, the load-displacement curve method is used to calculate the sleeve pull-out force. Taking the sleeve pull-out force load as the design target, the bolt preload is calculated inversely. Based on the calculated preload of the screw brush, a suitable standard bolt is matched to achieve forward design.

[0023] This invention solves the problem of design redundancy caused by underestimating the sleeve pull-out force simulation results; and the problem of sleeve detachment during vehicle testing caused by overestimating the sleeve pull-out force simulation results; the simulation results of sleeve pull-out force are more accurate. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0025] Figure 1 This is a flowchart of the present invention.

[0026] Figure 2 This is a schematic diagram of the finite element model of the shock absorber fork assembly of the present invention.

[0027] Figure 3 This is the load-displacement curve of the upper point on the sleeve when the friction coefficient is 0.2 and the torque is 180 NM.

[0028] Figure 4 This is a graph showing the relationship between the coefficient of friction and the sleeve pull-out force when the torque is 180 NM according to the present invention. Detailed Implementation

[0029] 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.

[0030] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0033] Example 1

[0034] like Figure 1 As shown, a forward design method for preventing shock absorber sleeve detachment includes the following:

[0035] The first step is to define the target pull-out force load of the shock absorber sleeve.

[0036] Based on the measured load spectrum of the axial force of the shock absorber in the previous generation model, the peak value of the axial force on the shock absorber when the suspension bounces down is determined. The peak value of the load is multiplied by a safety factor of 1.2 to obtain the design load for the shock absorber to prevent pull-out, i.e., the design load of the cylinder pull-out force; or it is greater than 20 times the unsprung weight load of the newly developed model to obtain the design load for the shock absorber to prevent pull-out.

[0037] The second step is to establish a finite element model of the shock absorber fork, sleeve, and bolt assembly.

[0038] Considering material nonlinearity, contact nonlinearity, interference fit between the sleeve and the damper fork, and bolt assembly preload, a finite element model of the damper fork, sleeve, and bolt assembly is established, such as... Figure 2 As shown;

[0039] The third step is to build a test bench for the pull-out force of the damper sleeve and measure the pull-out force of the sleeve under different bolt preloads.

[0040] The fourth step is to adjust the friction coefficient between the sleeve and the shock absorber fork based on the finite element model of the shock absorber fork, sleeve and bolt assembly established in the second step, and simulate the sleeve pull-out force under different bolt preloads.

[0041] Fifth, compare the simulation results of the sleeve pull-out force in the fourth step with the test results in the third step, adjust the friction coefficient between the damper fork and the sleeve until the simulation results of the sleeve pull-out force in the fourth step are consistent with the test results in the third step, and record the calibrated true friction coefficient.

[0042] Step 6: Replace the sleeves and shock absorber forks with different materials and repeat steps 2 to 5 to accumulate the actual friction coefficients between the sleeves and shock absorber forks of different materials. Then, modify the finite element model based on the actual friction coefficients to provide an accurate virtual verification method for subsequent forward design.

[0043] In this experiment, the sleeve is made of steel and the shock absorber fork is made of cast aluminum. The true friction coefficient between steel and cast aluminum obtained through steps two to five is a single value. When both the sleeve and the shock absorber fork are made of aluminum, steps two to five are repeated using the same simulation and experimental methods to obtain the true friction coefficient between aluminum and aluminum.

[0044] Step 7: Based on the modified finite element model, using the sleeve pull-out force design load obtained in Step 1 as the target, simulate the bolt preload required when the sleeve pull-out force is the target load.

[0045] Step 8: Match a suitable standard bolt based on the bolt preload obtained from the simulation;

[0046] After matching the standard bolts, apply the bolt preload force F to the finite element model of the shock absorber fork, sleeve and bolt assembly. In addition to verifying whether the sleeve pull-out force meets the requirements, it can also further verify whether the shock absorber fork meets the strength requirements.

[0047] The ninth step is to conduct bench tests and vehicle load-bearing system durability tests.

[0048] In step one, the measured load spectrum of the axial force of the shock absorber of the previous generation model was obtained by simulation based on the whole vehicle virtual test field technology.

[0049] In step three, six sets of shock absorber fork, sleeve and bolt assembly samples are designed. In the six sets of samples, the interference fit between the sleeve and the shock absorber fork hole diameter of each assembly is consistent, the bolt preload of each pair of assemblies is consistent, and the values ​​of the three bolt preloads are different. The sleeve pull-out force under different bolt preloads is measured by bench test (lower point constraint of the shock absorber assembly, upper point connection to the actuator, and pulling the sleeve upward).

[0050] In step four, the bolt preload torque is set to 180 NM, 190 NM, and 200 NM respectively. The lower point of the damper fork is constrained, and a forced displacement is applied along the axial direction of the damper at the upper point of the sleeve (the center point of the top surface of the sleeve). Simulations are used to obtain the reaction force-displacement relationship curves with the displacement of the upper point of the sleeve as the abscissa and the sleeve pull-out force as the ordinate under different bolt preload torques. Figure 3 The figure shows the reaction force-displacement relationship curve of the point on the damper sleeve when the friction coefficient is 0.2 and the preload torque is 180 NM. The peak load of the curve, i.e. the sleeve pull-out force, is 41942 N.

[0051] In step five, after multiple simulations, such as Figure 4 As shown: Plot the relationship between friction coefficient as the abscissa and sleeve pull-out force as the ordinate. As the friction coefficient increases, the sleeve pull-out force also increases. Further adjust the friction coefficient between the damper fork and the sleeve until the simulation result of sleeve pull-out force in the fourth step is consistent with the experimental result in the third step. Finally, calibrate the true friction coefficient between the damper fork and the sleeve.

[0052] In the sixth step, the finite element model is modified by replacing the friction coefficient between the sleeve and the damper fork in the finite element model with the actual friction coefficient obtained.

[0053] The method for obtaining the bolt preload required in the seventh step is as follows: After the friction coefficient between the sleeve and the damper fork is corrected to the true friction coefficient, a bolt preload is first applied, and then a sleeve pull-out force is obtained through simulation. When this pull-out force is less than the target load, a larger bolt preload is applied, and the sleeve pull-out force is obtained through simulation again, until the sleeve pull-out force obtained through simulation is consistent with the target load. The corresponding bolt preload is the required bolt preload F.

[0054] Example 2

[0055] This method is based on the pull-out force test of the shock absorber fork and sleeve, measuring the bolt tightening torque and sleeve pull-out force data. A finite element model of the shock absorber fork, sleeve, and bolt assembly is established. Simulation methods clarify the relationship between the friction coefficient between the shock absorber fork and sleeve and the sleeve pull-out force; the pull-out force increases with increasing friction coefficient. Based on the finite element model of the shock absorber fork, sleeve, and bolt assembly, and combined with the experimental data of bolt tightening torque and sleeve pull-out force, the friction coefficient between the sleeve and shock absorber fork in the finite element model is adjusted. That is, under the same preload, if the simulated sleeve pull-out force is less than the experimental value, the friction coefficient is increased in the finite element simulation model, thereby increasing the simulated sleeve pull-out force. Finally, the calibration is performed. The true friction coefficient between the sleeve and the shock absorber fork is determined, and the finite element model is further revised. Through data accumulation, the virtual verification method for the shock absorber sleeve pull-out force is improved. A forced displacement is applied to a point on the sleeve, and the displacement and reaction force curves of that point are calculated and output. When the curve reaches its peak and then declines, it indicates that the sleeve has been disengaged, and the peak load of the curve is the sleeve pull-out force. Based on the revised finite element model of the shock absorber fork, sleeve, and bolt assembly, the bolt preload corresponding to the sleeve pull-out force reaching the target load is calculated. Based on the calculated bolt preload, a suitable standard bolt is matched. The latest performance indicators of the shock absorber fork, sleeve, and bolt assembly, such as pull-out force and static strength, are simulated and calculated to achieve forward design. Detailed explanation is as follows:

[0056] The first step is to define the target pull-out force load for the shock absorber sleeve: Based on the measured axial force load spectrum of the shock absorber in the previous generation model, determine the peak axial tensile force on the shock absorber during suspension slump. Multiply the peak load by a safety factor of 1.2 to obtain the design load for the shock absorber sleeve pull-out force. When defining the target pull-out force load for the shock absorber sleeve in a newly developed model, the axial force load spectrum of the shock absorber can also be obtained through simulation using a virtual test track technology for the entire vehicle. The peak load of 1.2 times can be used as the development target for the pull-out force. Alternatively, based on design experience, the sleeve pull-out force load should be greater than 20 times the unsprung weight load of the newly developed model.

[0057] The second step is to establish a finite element model of the shock absorber fork, sleeve, and bolt assembly. This considers material nonlinearity, contact nonlinearity, the interference fit between the sleeve and the shock absorber fork, and bolt preload. The finite element model of the assembly is as follows: Figure 1 As shown;

[0058] The third step involved designing six sets of shock absorber fork assembly specimens. In all six sets, the interference fit between the sleeve and the shock absorber fork bore diameter was kept consistent, and the bolt preload was kept consistent between any two sets of assemblies. The sleeve pull-out force under different preloads was measured using bench testing. The shock absorber assembly specimens are shown below. Figure 2 As shown in the diagram, the shock absorber fork sleeve pull-out force test schematic is as follows: Figure 2 The test data for bolt preload and pull-out force are shown in Table 1;

[0059] Table 1 Test data of bolt preload and sleeve pull-out force

[0060]

[0061] Fourth step: Based on the finite element model of the damper fork, sleeve, and bolt assembly established in the second step, adjust the friction coefficient between the damper fork and sleeve, and set the bolt preload torque to 180 NM, 190 NM, and 200 NM respectively. Constrain the lower point of the damper fork, and apply a forced displacement along the damper axis at the upper point of the sleeve. Simulate to obtain the reaction force-displacement relationship curve at the forced displacement loading point, as shown in the figure. Figure 3 The figure shows the reaction force-displacement relationship curve at a point on the damper sleeve when the friction coefficient is 0.2 and the preload torque is 180 Nm. The peak load of the curve is 41942 N. This has been verified through multiple simulations. Figure 4 As shown: the relationship between different friction coefficients and sleeve pull-out force is plotted. As the friction coefficient increases, the sleeve pull-out force also increases. The friction coefficient between the damper fork and the sleeve is further adjusted until the simulation result of the pull-out force is consistent with the experimental result. Finally, the true friction coefficient between the damper fork and the sleeve is calibrated.

[0062] That is, when the bolt preload is F, the sleeve pull-out force meets the target load value that prevents the sleeve from coming out.

[0063] The sixth step is to adjust the bolt preload to match the standard bolts.

[0064] Step 7: After matching the standard bolts, apply bolt preload F to the finite element model of the shock absorber fork, sleeve and bolt assembly. In addition to verifying whether the sleeve pull-out force meets the requirements, further verify whether the shock absorber fork meets the strength requirements.

[0065] The eighth step is to conduct bench tests and durability tests on the vehicle's load-bearing system.

[0066] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the scope of protection of the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, any person skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention within the scope of the technology disclosed in the present invention. These simple modifications are all within the scope of protection of the present invention.

[0067] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0068] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A forward design method for preventing shock absorber sleeve detachment, characterized in that... Includes the following: The first step is to define the target pull-out force load of the shock absorber sleeve. Based on the measured load spectrum of the axial force of the shock absorber in the previous generation model, the peak value of the axial force on the shock absorber when the suspension bounces down is determined. The peak value of the load is multiplied by a safety factor of 1.2 to obtain the design load for the shock absorber to prevent pull-out, i.e., the design load of the cylinder pull-out force; or it is greater than 20 times the unsprung weight load of the newly developed model to obtain the design load for the shock absorber to prevent pull-out. The second step is to establish a finite element model of the shock absorber fork, sleeve, and bolt assembly. The third step is to build a test bench for the pull-out force of the damper sleeve and measure the pull-out force of the sleeve under different bolt preloads. The fourth step is to adjust the friction coefficient between the sleeve and the shock absorber fork based on the finite element model of the shock absorber fork, sleeve and bolt assembly established in the second step, and simulate the sleeve pull-out force under different bolt preloads. Fifth, compare the simulation results of the sleeve pull-out force in the fourth step with the test results in the third step, adjust the friction coefficient between the damper fork and the sleeve until the simulation results of the sleeve pull-out force in the fourth step are consistent with the test results in the third step, and record the calibrated true friction coefficient. Step 6: Replace the sleeves and damper forks with different materials and repeat steps 2 to 5 to accumulate the true friction coefficients between the sleeves and damper forks of different materials, and correct the finite element model based on the true friction coefficients. Step 7: Based on the modified finite element model, using the sleeve pull-out force design load obtained in Step 1 as the target, simulate the bolt preload required when the sleeve pull-out force is the target load. Step 8: Match a suitable standard bolt based on the bolt preload obtained from the simulation; After matching the standard bolts, apply bolt preload to the finite element model of the shock absorber fork, sleeve and bolt assembly. In addition to verifying whether the sleeve pull-out force meets the requirements, it can also further verify whether the shock absorber fork meets the strength requirements. The ninth step is to conduct bench tests and vehicle load-bearing system durability tests.

2. The forward design method for preventing shock absorber sleeve disengagement according to claim 1, characterized in that... In step one, the measured load spectrum of the axial force of the shock absorber of the previous generation model was obtained by simulation based on the whole vehicle virtual test field technology.

3. The forward design method for preventing shock absorber sleeve disengagement according to claim 1, characterized in that... In step three, six sets of shock absorber fork, sleeve and bolt assembly samples are designed. In the six sets of samples, the sleeve and shock absorber fork hole diameter interference of each set of assemblies are consistent, the bolt preload of each pair of assemblies is consistent, and the values ​​of the three bolt preloads are different. The sleeve pull-out force under different bolt preloads is measured by bench test.

4. The forward design method for preventing shock absorber sleeve disengagement according to claim 3, characterized in that... In step four, the bolt preload torque is set to 180 NM, 190 NM, and 200 NM respectively. The lower point of the damper fork is constrained, and a forced displacement is applied to the upper point of the sleeve along the axial direction of the damper. The simulation yields the reaction force-displacement relationship curve with the displacement of the upper point of the sleeve as the abscissa and the sleeve pull-out force as the ordinate under different bolt preload torques.

5. The positive design method for preventing shock absorber sleeve disengagement according to claim 4, characterized in that... In the sixth step, the finite element model is modified by replacing the friction coefficient between the sleeve and the damper fork in the finite element model with the actual friction coefficient obtained.

6. The forward design method for preventing shock absorber sleeve disengagement according to claim 5, characterized in that... The method for obtaining the bolt preload required in the seventh step is as follows: After the friction coefficient between the sleeve and the damper fork is corrected to the true friction coefficient, a bolt preload is first applied, and then a sleeve pull-out force is obtained through simulation. When this pull-out force is less than the target load, a larger bolt preload is applied, and the sleeve pull-out force is obtained through simulation again, until the sleeve pull-out force obtained through simulation is consistent with the target load. The corresponding bolt preload is the required bolt preload.

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