The Auto Torsion Beam Suspension’s Structure Optimization Based On The Fatigue Life Analysis

In view of the fatigue crack phenomenon of a certain type of auto torsion beam suspension in advance under service condition, this thesis tries to analyze its fatigue and optimize its structure, with an view to improve its fatigue life and solve the problem of fatigue fracture.The torsion beam suspension is composed of middle beam and trailing arms on both sides of the middle beam which connects the vehicle body with a rubber bushing. The suspension itself is relatively simple in structure. There are no extra rod structures and it is relatively easy to install or to dismantle. Installation space is not large and there is less installation point, which will not affect wheels’ movement. The structure itself can absorb torque from the road and acts as anti-roll bar, which add to the stability of suspension. This thesis firstly measures the torsion beam suspension geometry entity, using CATIA to establish 3D model of the suspension, and then establish the finite element model of suspension by processing in front of the finite element software. Based on the space linear elastic mechanics theory, the finite element method is used to analyze the torsion beam suspension. In accordance with the national industry standard, this thesis verifies that the suspension is safe under the three limit conditions of the ultimate torsion, maximum lateral force and impact load.Then this thesis chooses the direct transient response analysis of dynamic response analysis of suspension for FEM analysis. This thesis establishes the simple vehicle dynamics model of the suspension in the dynamic analysis software and get the load process of the suspension and the joints of vehicle body by simulation. This thesis then takes dynamic load simulation on suspension, selects the most appropriate course load as the suspension load boundary conditions by comparing the test results. Transient response analysis is carried out in PATRAN through proper load in suspension, reaching the results of its strain distribution. For the fatigue phenomena of fracture on the suspension,calculated the life of the suspension by fatigue crack initiation or strain analysis method. Finally, this thesis turns the life into mileage and compared it with the actual life of the suspension to verify the accuracy of the analysis.To improve the fatigue life of the suspension, this thesis analyzes the possible causes of its destruction. This thesis makes a research on how the spring hard point location affects the fatigue life of the suspension and optimizes the structure of the suspension so as to improve the fatigue life.