汽车变速器输入轴断裂失效分析

Fracture Failure Analysis of the Input Shaft of Automotive Transmission

某经渗碳淬火热处理的汽车变速器输入轴在行驶过程中断裂,采用断口宏微观分析、低倍酸蚀检验、硬度测试、渗碳层深度测定、金相检验、SEM断口分析及直读光谱成分分析等方法对输入轴断裂原因进行了分析。结果表明:样品断裂形式包括脆性断裂和疲劳断裂两种,断裂源均位于输入轴主副轴连接沟槽区域;样品主副轴连接沟槽区域的应力集中(机加工刀痕加剧了应力集中),是样品发生两种断裂失效形式的重要原因;行驶过程中的强受力,促进了脆性断裂失效的发生;非金属夹杂物在样品轴外表层的聚集,尤其在外表皮下的存在,加剧了应力集中,促进了断裂失效的发生。

A carburizing and quenching heat-treated automotive transmission input shaft breaks during driving, the cause of the input shaft fracture is analyzed by means of fracture macroscopic analysis, low-level acid corrosion test, hardness test, carburized layer depth measurement, metallographic examination, SEM fracture analysis and direct reading spectral composition analysis.The results show that the fracture forms of the sample include brittle fracture and fatigue fracture. The fracture sources are located in the main and auxiliary axis connecting groove region of the input shaft;the stress concentration of the sample primary and secondary shafts connected to the groove region（machined tool marks exacerbate the stress concentration） is an important reason for the two failure modes of the sample; the strong force during driving promotes the occurrence of brittle fracture failure; the accumulation of non-metallic inclusions on the outer surface of the sample shaft, especially under the outer skin, exacerbates stress concentration and promotes fracture failure.