A MODEL FOR SIMULATION OF FRICTION PHENOMENON BETWEEN DIES AND WORKPIECE

Based on the interaction of asperities and upperbound approach a mathematical model for simulation of friction phenomenon between dies and workpiece is proposed.Optimizing the mathematical model with respect to several variables it is found that in addition to adhering, tearing, ploughing, etc., asperities workpiece can move wave-like along the surface layer and under certain circumstances they may disappear. If the asperities wavily move along the surface layer the friction coefficient depends on the geometry of asperities. However,the bonding strength of asperities has no significant influence on friction coefficient. The depth of the plastic deformation layer is related to the geometry of asperities, too.The soundness of the prerequisite of the proposed model and some analytical results were verified by experiments.     

快速路交通微分系统的脉冲迭代学习策略研究

针对快速路交通微分系统,结合该交通系统具有明显的重复性和周期性等特点,设计了一种脉冲迭代学习策略,并建立了迭代学习误差的收敛性条件.其次,利用λ范数和脉冲Gronwall不等式等方法证明了算法的收敛性.结合脉冲控制与学习控制的特点,该方法的优点在于容易实现和经济环保,且能有效地达到控制目的.最后,通过数值仿真实证进一步说明所设计控制方法的有效性.     

A model for simulation of friction phenomenon between dies and workpiece

Based on the interaction of asperities and upperbound approach a mathematical model for simulation of friction phenomenon between dies and workpiece is proposed. Optimizing the mathematical model with respect to several variables it is found that in addition to adhering, tearing, ploughing, etc., asperities workpiece can move wave-like along the surface layer and under certain circumstances they may disappear. If the asperities wavily move along the surface layer the friction coefficient depends on the geometry of asperities. However, the bonding strength of asperities has no significant influence on friction coefficient. The depth of the plastic deformation layer is related to the geometry of asperities, too. The soundness of the prerequisite of the proposed model and some analytical results were verified by experiments.Department of Materials Engineering, Northwestern Polytechnical UniversityThis is a project of the cooperative program between the Department of Materials Engineering of Northwestern Polytechnical University of the People's Republic of China and the Institute for Metal Forming at Lehigh University of the United States of America.     

模具与工件之间摩擦过程的一个模型*

本文中以刚性微凸体与可变形微凸体的相互作用模拟金属压力加工过程中模具与工件之间的摩擦过程,并用上限法分析所提出的模型.将数学模型进行多变量最优化处理后发现,金属压力加工过程中,除了可能发生工件上的微凸体与模具上的微凸体相互粘结、撕裂和犁沟等现象外,工件上的微凸体可能沿工件表面波浪式前进,形成塑性波,也可能被辗平而消失.在形成塑性波的条件下,摩擦系数与微凸体几何形状有关.但微凸体的连结强度对摩擦系数影响不大.微凸体的几何形状对工件表面下的塑性变形层的深度有显著的影响.实验结果证实了本文所提出的模型的前提的正确性以及部分理论分析结果.