目的 针对柴油机机体和主轴承盖紧固面之间发生的微动疲劳失效现象，探讨微动状态下柴油机硅铝合金机体的裂纹萌生特性及寿命评价方法。方法 建立机体紧固面组合结构有限元模型，计算机体紧固面上的应力/应变历史数据，在此基础上分析机体紧固面的接触状态，探讨摩擦系数及摩擦功对微动疲劳特性的影响。采用多轴疲劳参数（CCB、F、SSI、Ruiz参数）预测了机体微动裂纹萌生位置，对所用参数进行修正，建立适用于机体紧固面的微动疲劳寿命预测模型。结果 预测结果与实验值对比可知，F、SSI参数与实验结果差异较大，CCB和Ruiz参数的寿命预测结果与实验值接近，在2.3倍公差带因子范围内。但由于CCB参数预测的裂纹萌生位置和机体实际断裂位置不符，所以不能用于机体微动疲劳寿命预测。结论 在接触状态突变的区域容易萌生微裂纹，适当增大摩擦系数或者降低摩擦功可以抑制机体的微动疲劳损伤。Ruiz参数预测的机体微动疲劳寿命与实验值最为吻合，用Ruiz参数评估柴油机硅铝合金机体的微动疲劳寿命可以将误差控制在2.3倍公差带因子范围内。

The work aims to discuss crack initiation characteristics and life evaluation method of diesel engine Si-Al alloy block in fretting state in respect of fretting fatigue failure phenomenon between diesel engine block and fastening surface of main bearing cap. The finite element model of the block fastening surface composite structure was built, and stress/strain historical data on fastening surface of the block was analyzed. On this basis, contact state of the fastening surface on the block was analyzed, and influences of friction coefficient and friction work on the fretting fatigue characteristics were discussed. Multi-axis fatigue parameters, CCB, F, SSI and Ruiz, were used to predict crack initiation position of the block. The model was built for predicting the fretting fatigue life of the block by modifying all parameters. Compared with the experimental values, the F and SSI parameters in prediction results differed greatly from those in experimental results. The life prediction results of CCB and Ruiz parameters were close to the experimental values, and fall within a scatter band of 2.3. However, the crack initiation position predicted with CCB parameter was inconsistent with actual fracture position of the block, hence the parameter could not be used to predict fretting fatigue life of the block. Microcracks may easily appear in the contact region subject to sudden change, and fretting fatigue damage can be suppressed by appropriately increasing friction coefficient or decreasing friction work. Fatigue life of the block predicted with Ruiz parameter is in a good accordance with the experimental values. It is feasible to evaluate the fretting fatigue of diesel engine by using Ruiz parameter within a scatter band of 2.3.