A High-Accuracy Fatigue Analysis of Vehicle Differential Case Based on Cumulative Damage Theory under Approximate Actual Load Conditions 2020-01-1325

In recent years, with the rapid development of automobile industry, especially the vigorous promotion of new energy vehicles, CAE simulation analysis technology plays an increasingly important role.

Differential is a key component of vehicle drive line system, its main function is to meet the different demands of the wheels on both sides when turning. The differential is composed of differential case, planetary gears, planetary gear shaft and half-shaft gears. Because of complex working conditions and poor stress environment, fatigue damages are easily occurred on these components. If the fatigue life of differential can be predicted by simulation analysis technology, it will provide a basis for vehicle design, which will reduce the cost of practical test. In addition, the structure can be optimized by simulation analysis, so as to improve its performance and fatigue life.

However, the structure of differential is complex, and it is difficult to analyze its fatigue life. Therefore, this study proposes a feasible fatigue life simulation method for differential case. In this method, the multi-body dynamic model of the full vehicle driveline system is first established to ensure the correct transmission of force and displacement. Then the rotation position of the input shaft is equally divided into 18 parts around the circumference. Under the pre-defined input torque, the force analysis of the differential case at each position can be carried out. These calculated transient results are then combined into a rotation cycle load for the fatigue life analysis of the differential case. Then the stress analysis of the differential case under the rotation cycle load is carried out with the finite element method. With the calculated stress, the transient fatigue life analysis can be carried out to calculate cumulative damage and fatigue life of differential case.