高温发汗润滑体单胞接触应力分析模型研究

采用“无限大板”中孤立小孔应力集中方法，建立了一种新的以特征参数λ表征的厚壁单胞体接触应力理论模型;以高温发汗润滑体为对象，采用该模型仿真分析了单胞体在特征参数λ≤0.4情况下的胞内应力分布状态。结果表明：随着外载荷的增大，接触半径逐渐增大，且接触区域的各向应力（绝对值）均逐渐变大；最大剪应力逐渐从胞体表面向胞体内部迁移，其y向最大应力从接触中心逐渐向孔边θ=0和θ=-π,r=r₂处转移,x向最大应力从接触中心逐渐向孔边θ=-π/2,r=r₂处转移；该应力集中区逐渐取代胞体接触表面而成为微裂纹诱发源。λ对胞体接触应力分布也有很大影响：当λ=0.4时，孔穴应力集中区与胞体接触区的y向应力差值最大；当λ=0.1时，两处的x向应力差值最大；当外载荷大于1000N时，λ=0.2的胞体内的最大剪应力具有最小值。

Static Stiffness Research of a Hybrid Machine Tool Based on the Element Stiffness Matrix

This paper addressed the static stiffness of a new heavy hybrid machine tool XNZH2430,which was developed in Tsinghua University based on a 2-DOF translational parallel mechanism.In analysis process, the structure of the machine tool can be represented by a number of nodes and elements.The holistic stiffness matrix of the machine tool was built based on the theory of element stiffness matrix.The stiffness distribution of the machine tool within a certain work space was analyzed.The analysis result indicates that the machine tool has better stiffness performance when the moving platform is close to the symmetric position.When the platform is away from the symmetric position,stiffnesses along the y and z directions are turning worse dramatically.Therefore,the moving platform should stay close to the symmetric position during working process.