某柴油机连杆疲劳强度分析和结构优化

Fatigue Strength Analysis and Structural Optimization of the Connecting Rod in a Diesel Engine

应用有限元分析软件ANSYS Workbench 14.0对某柴油机连杆的预紧工况、受拉工况和受压工况进行了有限元分析,得到了各工况下连杆的应力分布,并进一步对连杆的疲劳强度进行了分析。根据分析结果,对连杆小头油孔位置进行了改进;确定了设计变量为连杆小头与杆身的过渡圆角和靠近连杆小头横截面内的倒角,约束连杆的质量,以连杆等效应力最小为优化目标,进行优化分析。优化后的连杆无论在最大拉伸工况,还是在最大压缩工况,最大等效应力均有所降低,疲劳安全系数提高了5%,质量减少了2.8%,满足设计要求。

The fatigue strength of＇the connecting rod in a diesel engine is calculated and its structure is optimized based on the finite element analysis. Firstly, according to the design requirement and the force analysis, the basic design size of the connecting rod is determined. Secondly, the stress distribution of the connecting rod under different conditions is ob- tained by finite element analysis using software ANSYS Workbench 14.0 According to the analysis results, the position of the oil hole in the small head of the connecting rod is modified. By determining the transition fillet radius between the small head and the rod body and the chamfering radius of the cross section near the small end as the design variables, and limiting the mass of the connecting rod, the optimization is carried out to obtain the minimal equivalent stress. After the optimization, the maximum equivalent stresses of the connecting rod in both the maximum tensile condition and the maximum compression condition are reduced. The fatigue safety factor is improved by 5 %, and the mass of the connecting rod is decreased by 2.8%. These results have met the design requirement.