Finite element simulation and multifactor failure analysis of an important stepped shaft fracture events

Abstract

Aiming at a fracture event of an important stepped shaft parts, ABAQUS finite element method was used to simulate and analyze. The results show that the stress concentration is serious at the step where shaft fracture occurs. The maximum stress occurs at the R2 transition corner. The maximum stress value under the most unfavorable condition is 319.9MPa, which exceeds the yield strength limit of the material. Scanning Electron Microscope and X-ray Energy Spectrum analysis shows that fracture of the shaft is a fatigue fracture initiated by multiple sources. Design analysis states clearly that the initiation is mainly related to the small turning radius of the step, which causes the stress concentration factor increase. At the same time, the shoulder height is higher which cause the sudden change of the section size, and will aggravate the stress concentration effect. Furthermore, machining quality analysis indicates that the rough surface with micro-defects due to out of control of metalworking may be the origin of fatigue crack initiation. Heat Treatment process quality analysis indicates that improper control of the quenching and tempering process has a negative impact on the initiation of the crack. Working conditions analysis shows that the actual load state, which exceeds the L2 intermediate level of the design standard load spectrum, accelerating the fatigue damage of mechanical parts.