20CrMnTi钢拖拉机动力输出轴的断裂失效分析

Fracture Failure Analysis of 20CrMnTi Steel Tractor Power Output Shaft

某拖拉机在田间旋耕作业时,其动力输出轴发生断裂现象。通过断口形貌、化学成分、金相组织与硬度等方面进行综合分析,以探索动力输出轴失效原因。结果表明,动力输出轴的化学成分、金相组织和硬度均符合技术要求,断口中有少量夹杂物;断裂位置为轴头花键和齿轮之间的变径光轴处,断口形貌呈现棘轮花样,为多源扭转疲劳断裂;裂纹源沿台阶方式在轴断面扩展,在交变扭转载荷的反复作用下,由于应力集中而导致断裂。

The power output shaft of a tractor breaks when it was rotating in the field.The fracture morphology,chemical composition,metallographic structure and hardness were comprehensively analyzed to explore the failure reasons of the power output shaft.The results show that the chemical composition,micro structure and hardness of the power output shaft meet the technical requirements,and there are a few inclusions in the fracture.The fracture location is the tapering optical axis between the spline and the gear of the shaft head,and the fracture morphology presents a ratchet pattern.The multi-source torsional fatigue fracture is caused by the crack source spreading along the step mode in the shaft section.Under the repeated action of alternating torsional load,the fracture is caused by the stress concentration.