汽车悬架螺旋弹簧断裂分析

Fracture Analysis of Automotive Suspension Coil Spring

前悬架螺旋弹簧在台架试验进行到9万次时发生断裂,为找出断裂原因,对断裂螺旋弹簧进行了断口分析、化学成分分析和显微组织分析;随后对同批次的弹簧进行疲劳性能试验和刚度性能试验;对制造螺旋弹簧同批次的钢丝进行了力学性能分析。结果表明,断裂螺旋弹簧的断裂属单向弯曲大应力疲劳断裂,裂纹起源于螺旋弹簧侧表面缺陷处。螺旋弹簧在成分、显微组织、力学性能、疲劳性能、刚度性能等方面均满足设计要求。分析表明,螺旋弹簧选材合理,制造工艺流程合理,设计余量充足,断裂的根本原因是弹簧侧表面缺陷存在导致应力集中,在外载荷作用下发生大应力疲劳断裂。

The automotive suspension coil spring fractured, about 9 ×104 times, in process of bench test. The reason of fractured spring was analyzed by the following methods such as fractrogaphy, chemical analysis, microstructure inspection,fatigue test, and static stiffness test and so on. Subsequent, the steel wire with the same batch of the broken spring were analyzed in mechanical properties. The results show that the fracture appearance of the coil spring is the single bending fatigue fracture with high nominal stresses concentration, the cracks originate from the defect of coil spring side surface. The result of the chemical analysis,microstructure observation and fatigue test etc, can satisfy the requirements of the design.Comprehensive analysis shows that the selection of the material, design of coil spring, manufacturing process are reasonable.The root cause of the fracture is the defect which is damaged in service, existing on the side surface, resulting stresses concentration by applied load.