某星形活塞发动机主连杆多轴疲劳强度分析

Multiple-Axle Fatigue Analysis of a Star Engine Master Conrod

为评估某航空星形活塞发动机主连杆结构强度,建立曲柄连杆机构运动学和动力学分析模型,得到主连杆载荷特性。建立了考虑结构接触非线性因素的主连杆应力计算有限元模型,通过由模拟装置得到的实测应力数据对模型进行了标定,进而计算得到整个工作循环内的动态应力场。结果表明:副连杆引起的附加弯矩是影响主连杆杆身危险部位应力过高的主导因素。在此基础上,考虑结构表面工艺状态等因素的影响,基于临界平面法对主连杆多轴疲劳强度进行了校核。结果表明:该连杆杆身与大头过渡区域处疲劳安全系数较低,计算危险点与实际疲劳裂纹位置一致。

To assess the master conrod structural strength of a star engine, a kinematic and dynamic analysis models of the crank-conrod mechanism was established and the load characteristics was obtained. The finite element model considering structure nonlinear factors was calibrated by the measured stress data from the simulant, and then used to calculate dynamic stress field over the entire operating cycle. The analysis results show that the additional bending moment from slave conrod is the main factor which causes the stress of the dangerous part of master conrod shank to be too high. And then considering the impact of structural factors such as surface technology, the multiple-axle fatigue of master conrod was assessed based on the critical plane approach. The results show that the fatigue safety factor of the transition region between the conrod shank and the big end is relatively low, which has been confirmed by the actual fatigue crack.