变速器壳体低周疲劳优化设计

Transmission Housing Low-cycle Fatigue Optimization Design

目的分析变速器壳体驻车耐久试验的失效根本原因,对变速器壳体进行低周疲劳优化设计。方法首先排查壳体的化学成分、铸造质量,排除材料和工艺引起失效问题的可能性,然后通过有限元方法分析驻车轴孔的最大拉应变、驻车工况壳体变形、轴孔接触区域。根据局部应变分布特征,提出驻车轴修形的优化方案,并且根据壳体材料的低周疲劳参数,确定Coffin-Manson模型,并根据该模型预测壳体驻车轴孔优化前后的疲劳寿命。结果驻车轴孔的最大拉应变高达0.95%,确定应变过大是导致壳体失效的根本原因。驻车轴度修形的优化方案将最大拉应变降低到0.40%,塑性应变占比由42%降低到5%,疲劳寿命的预测值由原来的175次提高到7980次,满足试验循环次数1000次的要求,最终优化物理样机通过了驻车耐久试验验证。结论使用的Coffin-Manson模型参数能准确地预测变速器壳体的低周疲劳寿命,驻车轴小角度修形优化方案能够有效解决局部应变过大的失效问题,具有一定的工程参考意义。

This paper aims to find out the root cause of the failure of transmission housing park lock test issue and optimize the low cycle fatigue life of transmission housing.Firstly,checked the housing chemical component and cast quality,excluded the material and casting quality issue.And then analyzed the housing strain is up to 0.95%,confirmed the root cause of the housing crack is big strain amplitude.Finally,according to the housing system deformation and contact area results of finite element method model,proposed a proposal of shaft modification,confirmed the Coffin-Manson model according to housing material low-cycle fatigue parameters,predicted the fatigue life of the housing.The shaft sharp modification proposal decreased the strain to 0.40%,plastic strain occupancy rate decreased from 42%to 5%.The predicted fatigue life of the housing increased from 175 cycles to 7980 cycles,which can fulfill the 1000 cycles requirement,and the physical samples had passed the test.The Coffin-Manson model parameters used in this paper can predict the low cycle fatigue life of transmission housing accurately,the shaft modification proposal can solve local big strain failure issue effectively,which is significance to engineering.