板料冲压加工数值模拟中接触摩擦问题的研究

在分析汽车覆盖件形状特征及冲压过程接触状态变化的基础上，提出了基于微分几何和参数曲面的外推式逐级扩散搜索新算法，该方法避免了大量重复接触点的判断和点与曲面之间最短距离的计算，提高了搜索效率。用修正的罚函数法和库仑摩擦定律分别对接触点的法向接触力和切向摩擦力进行计算，并根据接触单元的形状实现了接触力从被接触点到接触单元节点的转化。通过算例分析验证了所用方法的可行性和有效性。

RESEARCH ON CONTACT FRICTION IN SHEET FORMING NUMERICAL SIMULATION

A new gradually extrapolating contact searching algorithm is proposed in terms of automobile panels shape feature and transformation of contact situation during sheet forming, which is based on differential geometry and parametric surface. This approach avoids judging plenty of contact coupling points and calculating the shortest distance between point and surface repeatedly. So the searching efficiency is enhanced. The modified penalty function method and coulomb friction law is used for evaluating normal contact force and tangent friction force respectively. In addition, the transformation of the contact force from contact point to nodes of contact elements is accomplished according to their shape. The results of examples verify the feasibility and validity of solution used.