Reasons for the fracture of a less－leaf spring used in a certain touring car

During the reliability road test of a certain touring car, it was found that the less－leaf spring had broken. The cause of the fracture of the less－leaf spring was anlayzed by macroscopic observation, chemical composition analysis, hardness testing, metallographic examination, scanning electron microscopy analysis. The results show that there were local folds on the surface of the less－leaf spring. During the road test, stress concentration was generated on its surface, which promoted the initiation and propagation of cracks, ultimately led to the fracture of the less－leaf spring.