仿生活塞疲劳寿命预测与回归设计
Prediction and Regression Design of Bionic Piston Fatigue Life

针对发动机活塞缸套系统的摩擦损失占发动机机械总功耗的50％的问题,基于贝壳体表条纹形凸脊结构的耐磨损特性,对发动机活塞在气缸内往复运动过程中裙部与缸壁产生周期性碰撞导致的磨损进行了仿生研究。将贝壳体表的结构形态以垂直竖状条纹形式沿活塞轴向贯穿设计于裙部,可起到减磨、卸载集中应力、提高疲劳寿命的效果。通过对标准和仿生活塞进行热？不？耦合有限单元分析,得出了活塞各个部位的应力应变情况,根据曼森和科芬准则得出了仿生活塞各部位疲劳寿命,并对疲劳寿命进行部分正交多项式回归设计,找出了试验水平、因素与疲劳寿命的内在规律。选取最优仿生活塞和标准活塞进行了台架试验和机理分析,发现这种贯穿于裙部的活塞轴向的浅窄大间距条纹可提高活塞疲劳寿命,条纹深度对活塞各个部位的疲劳寿命影响最大,仿生活塞磨损量比标准活塞平均减小41.4％,温度平均降低7％。该结果可为发动机设计和耐磨损研究提供参考。
The frictional loss of piston cylinder jacket system accounts for up to about 50％ of the total mechanical power of engine. Peculiarity of sea shells in standing wear and tear is closely related to the stripe shape and ridge form on their surface. When piston, the main part of an engine, reciprocates within cylinder jacket, skirt and cylinder wall will produce periodic collision and abrasion. We conducted a bionic design on the piston skirt. The form of shell’s surface was designed with vertical stripes through machining grooves along the axial direction of piston skirt in order to reduce attrition, release concentrated stress and improve fatigue life. First, through the thermal？？mechanical coupling finite element analysis on both standard and bionic pistons, we analyzed the strain and stress of every part of the piston. Then we obtained the fatigue life of every part of the bionic piston according to Manson and Coffin formula. A partial orthogonal polynomial regression design on the fatigue life was conducted to find the inherent rules among test level, factors and fatigue life. Optimal bionic piston and standard piston were selected to conduct bench test and mechanism analysis. Results show that the grooves along the axial direction of piston skirt, with shallow or narrow and a large spacing, can improve the fatigue life of pistons. The wear and tear of the bionic piston is decreased by 41.4％, and the average temperature is lowered by 7％ compared with standard piston