柴油机气缸盖高应力梯度部位多轴应力状态分析研究-动力机械及工程专业论文 word格式.docx

值,确定了气缸盖高应力梯度部位。基于动态响应分析计算得到的节点应力结果,依据 X、Y、Z 三坐标轴的应力单位矢量分别计算得到高应力梯度部位所在节点处三个主应力在每一坐标轴上的方向角,以此来表征主应力方向。通过计算爆发压力及其附近时刻的主应力方向来分析研究高应力梯度部位的主应力方向随时间变化而呈现的多轴应力状态特征,为气缸盖非比例多轴疲劳寿命预测提供理论支撑。
关键词:柴油机,气缸盖,应力梯度,多轴应力状态,动态响应分析
The Multiaxial Stress State Analysis Research on High Stress Gradient Position of Diesel Engine Cylinder Head
Abstract
As one of the key parts of the bustion engine, cylinder head bears periodic function of the bolt force, the gas pressure and the heat thermal load, leading to the periodic changes in stress and deformation. To cylinder head, the multiaxial stress state of high stress gradient position has a great effect on its fatigue failure. In order to solve this problem, the structure statics and dynamic response analysis are conducted based on finite element theory, and multiaxial stress state characteristics of high stress gradient parts is detailedly researched , which provides support for the non-proportional multiaxial fatigue life prediction.
The three-dimensional geometry solid models of cylinder head, cylinder sleeve, cylinder block, bolts and other parts are built with Pro/E software, then they are imported into the professional meshing software ANSA to set materials and properties for each part and select rational unit types and unit size according to there respective structural features for meshing , and ten contact pairs are defined between parts such as cylinder head and cylinder head gasket, cylinder head and bolts, cylinder block and cylinder sleeve, Valve seat ring and cylinder head and the finite element grid model posite structure pleted under the premise of ensuring the calculation accuracy. Boundary conditions including constraints, the bolt preloaded force and the breakout pressure are exerted on the grid model in the finite element analysis software ANSYS, and static calculation is carried out in three working conditions which are preloaded force, preloaded-breakout pressure and preloaded-breakout pressure overload