Finite element analysis of the hottest SGB rear ax

SGB type rear axle finite element analysis

Abstract: in this paper, in the development process of SGB type rear axle, it is found that the local strength of the axle is insufficient after the test, and we have improved this situation. We use ANSYS Workbench finite element analysis software to calculate, analyze and compare the improved rear axle, and also make a tentative analysis of the fatigue life of the rear axle

key words: axle improvement finite element

1 preface

in order to adapt to the increasingly fierce market competition and meet the different needs of different customers, it is the goal of every company to quickly develop high cost-effective products that meet the market demand. Therefore, CAE technology has been more and more widely used in many enterprises

sgb rear axle is a newly developed rear axle of our company. In the product test, the bridge was partially cracked. This paper is not only the analysis and improvement of the problem, but also the fatigue life analysis has always been the difficulty of CAE analysis. Because there are many process factors that actually affect the fatigue life, the calculated life value is difficult to coincide with the test life value. This paper also makes some tentative analysis to provide reference for the further improvement of the bridge

2 Establishment of finite element model

in order to get accurate calculation results, the simplification of finite element model must be very close to the actual structure. According to the characteristics of the rear axle, we simplified the axle. In order to reduce the amount of calculation, some parts that have little impact on the analysis results were omitted; The bridge is divided by solid lattice. The simplified finite element model has 749486 nodes and 234506 elements, as shown in Figure 1. The improvement plan drawn up according to the actual situation is shown in Figure 2

3 constraints and loads

3.1 constraints

the boundary conditions of the bridge are mainly treated on the casings on both sides

3.2 load

the stress of the axle is relatively complex, but after careful analysis, the load on the rear axle is mainly bending, torsion, lateral and thermal insulation materials and longitudinal loads for refrigerators. The bending load mainly comes from the weight of the vehicle body. The torsional load produces the influence of the uneven road surface on the wheels, resulting in the torsion of the axle. The lateral and longitudinal loads mainly come from the influence of the vehicle on the axle when turning, accelerating and decelerating

4 calculation condition classification

in this paper, the following five conditions are used to simulate the corresponding test process of the rear axle:

condition 1 (vertical alternating torsion condition): simulate the situation that two wheels are one high and one low when the car is driving on uneven roads

condition 2 (longitudinal acceleration bending condition): simulate the stress condition of the rear axle during acceleration

condition 3 (longitudinal deceleration bending condition): simulate the stress condition of the rear axle during deceleration

condition 4 (lateral turning condition): simulate the stress condition of the rear axle when turning

5 calculation results and result analysis

5.1 static analysis results of the original structure

the calculation shows that the stress value at the root of the beam and the connection between the longitudinal beam and the casing is large. See the stress nephogram of each working condition for the specific results

working condition 1: it can be seen from the stress distribution nephogram that the part with large stress appears at the connection between the beam and the longitudinal beam, which is basically consistent with the part with cracks in the experiment. The part with the shortest fatigue life also appears here

working condition 2: according to the stress distribution nephogram, the maximum stress and the shortest service life appear at the connection between the longitudinal beam and the casing, and the stress at the connection between the transverse beam and the longitudinal beam is also large The strength and fatigue life of other parts basically meet the requirements

working condition 3: from the stress distribution cloud map, it can be found that the maximum stress and the shortest service life also appear at the connection between the casing and the longitudinal beam, and the connection stress between the transverse beam and the longitudinal beam is also large The strength and fatigue life of other parts basically meet the detailed requirements of concrete block flexural strength test

working condition 4: it can be found from the stress distribution nephogram that the stress value at the loading position is large, but the maximum stress and the shortest fatigue life still appear at the connection between the beam and the longitudinal beam

the strength calculation shows that the parts with large structural stress under various working conditions mainly appear at the root of the beam, which is basically consistent with the parts with cracks in the experiment. Therefore, the insufficient strength of the root of the beam is the main reason for the cracking of the axle

5.2 improvement scheme and calculation results

according to the experimental and calculation analysis results, in order to improve the stress situation at the connection between the beam and the longitudinal beam, we have made the following improvements: add stiffeners on both sides of the connection between the beam and the longitudinal beam. Improvements are shown in Figure 2

5.3 comparison of maximum stress value before and after improvement

because this paper adopts linear analysis, and in the process of geometric model transmission, there are local sharp corners of the model due to the time relationship, which is not well handled, so the result value is large, and the actual structure will not have such a large stress value. Therefore, we only evaluate the change of maximum stress value before and after improvement to judge whether the improvement scheme is effective and feasible. The maximum stress values before and after the improvement are shown in the following table:

5.4 comparison of fatigue life values before and after the improvement

from the above table, we can see that the maximum stress value of the improved structure is much lower than that of the original structure, the maximum stress value of torsion often occurs in actual work is significantly reduced, and the fatigue life is doubled. At the same time, the improved structure has no early cracking phenomenon during the test, It shows that the improved structure is effective and feasible

6 conclusion

due to the geometric sharp corners left during modeling, there will be different degrees of stress concentration in local areas during analysis and calculation. Therefore, the maximum stress value and fatigue life value of the axle are only for reference and customer-centered innovative service and supply: it is only used as a basis to judge whether the improvement scheme is effective

through the analysis of SGB rear axle with ANSYS Workbench finite element software, this paper shows the practicability of finite element technology in the structural design and improvement of automotive components. With the continuous development of finite element technology in the automotive field, it is bound to play a more and more extensive role in the future development, design and improvement

[References]

[1] caizhiwu, Chen Jie, Shi Yingming, "analysis and Research on the rear axle housing of a certain type of vehicle", 2004ansys Chinese user papers (end)