基于热弹塑性理论的内燃机结合部法向负荷

Normal Load of Internal Combustion Engine Junction Based on Fractal Theory of Thermal Elasto-Plastic Contact

针对目前机械零部件接触关系建模普遍采用光滑表面,而没有考虑表面粗糙度影响的问题,基于各向异性分形几何理论的热弹塑性法向接触力学模型,以多参数为自变量,建立了粗糙表面热弹塑性接触扩展分形模型.从常物性和变物性两方面,分别计算得到内燃机缸盖-缸垫结合部法向负荷理论值,并与缸盖-缸垫-机体-螺栓四体三维热弹性接触有限元简化模型计算得到的仿真值进行比较和分析.结果表明:在靠近两排气门间的缸口处,是否考虑材料变物性对计算结果有较大影响;零部件接触表面粗糙度对法向负荷等接触状态具有影响,目前常用的光滑表面有限元建模计算所得结果与实际情况存在偏差.

Based on normal mechanics model of thermal elasto-plastic contact adopting anisotropic fractal geometrical theory,three parameters were used as argument,then the extended fractal model of thermal elasto-plastic contact of rough surfaces was established for the problem of ignoring the effect of surface roughness in mechanical parts modeling.The theoretical values of normal load in the internal combustion engine cylinder head-cylinder head gasket joints were calculated with constant properties and variable properties,respectively.Then,these theoretical values were analyzed and compared with simulation values which resulted from the four-body contact simplified model composed of cylinder head-cylinder head gasket-engine block-bolts.The results clearly show that in the cylinder ring near the two exhaust valves,whether considering the variable properties or not has a significant impact on the results.Contact surface roughness has an impact on the normal contact load.The results calculated from smooth surface finite element modeling has great deviation from the actual situation.