速度对聚四氟乙烯摩擦系数影响的分子动力学模拟  

Effect of velocity on polytetrafluoroethylene friction coefficient using molecular dynamics simulaiton

作　　者：潘登 刘长鑫[1,2] 张泽洋 高玉金[3] 郝秀红 Pan Deng;Liu Chang-Xin;Zhang Ze-Yang;Gao Yu-Jin;Hao Xiu-Hong(School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China;Aviation Key Laboratory of Science and Technology on Generic Technology of Self-Lubricating Spherical Plain Bearing, Yanshan University, Qinhuangdao 066004, China;AGC Automotive (China) Co., Ltd., Qinhuangdao 066004, China)

机构地区：[1]燕山大学机械工程学院,秦皇岛066004 [2]燕山大学自润滑关节轴承共性技术航空科技重点实验室,秦皇岛066004 [3]旭硝子汽车玻璃(中国)有限公司,秦皇岛066004

出　　处：《物理学报》2019年第17期215-224,共10页Acta Physica Sinica

基　　金：国家自然科学基金青年科学基金(批准号:51605418);河北省自然科学基金青年科学基金(批准号:E2016203206)资助的课题~~

摘　　要：基于分子动力学方法建立了双层聚四氟乙烯(polytetrafluoroethylene,PTFE)摩擦模型,研究了不同速度下PTFE的摩擦过程.通过分析不同速度下接触区内下层PTFE分子键长、键角、分子形状的变化及接触过程中摩擦力和正压力的变化,从微观角度研究了速度对PTFE摩擦系数的影响.研究结果表明:随着速度的增加,接触区内PTFE粒子间的键长变短,键角变小,分子链沿x;方向的变形量增加.变形后的PTFE分子产生的回弹力导致上、下层PTFE分子间相互作用力增加,从而增加了摩擦力.当速度进一步增大时,接触区内下层PTFE粒子间的键长和键角多处于平衡位置,分子链沿x方向的变形量减小.这很可能是由于接触区内下层PTFE分子沿速度方向倾斜,使上、下层PTFE分子趋于平行滑动,从而降低了摩擦力.不同速度下正压力几乎保持不变.因此,当上层PTFE所受外载荷固定时,摩擦系数随着速度的增加先增大后减小,临界速度为1.2 m/s,这与实验研究结果一致.Velocity is an important factor affecting the friction coefficient of polymers.Polytetrafluoroethylene(PTFE),as a typical self-lubricating polymer,has attracted extensive attention because of its low friction coefficient.Currently,the friction coefficient of PTFE is investigated usually by using experimental method.The experimental study which is limited by the functionality and precision of the apparatus is inaccessible to the exploration of the microscopic tribological mechanism of PTFE.Therefore,the coarse-grained molecular dynamics simulation method is adopted in this study.In the coarse-grained model,one PTFE molecule is simplified into ten beads,including two end beads and eight backbone beads.The non-bonding and bonding interactions between beads are described by using Lennard-Jones(L-J)and multi-centered Gaussian-based potential.In order to investigate the effect of velocity on the friction coefficient of PTFE at an atomic level,we build a two-layer PTFE friction model by using the coarse-grained molecular dynamics simulation method.To directly compare the experimental results with the simulation results,we set,the value of the externally applied load and the range of the velocities that match each other as closely as possible.The mechanism of how the velocity affects PTFE friction coefficient is obtained at an atomic level through analyzing the bond length distribution,bond angle distribution,the deformation of the bottom PTFE molecules within the contact area,and the friction force and normal force as a function of simulation time.The simulation results show that,the bond length and bond angle decrease,the deformation of the bottom PTFE molecules along the x-direction and the friction force increase with velocity increasing.This is because the bounce back caused by the deformed PTFE molecules enhances the friction force.The severer the deformation,the larger the friction force will be.However,when the velocity exceeds a critical velocity,the bond length and bond angle increase,the deformation of the bot

关 键 词：聚四氟乙烯 摩擦 速度 分子动力学 

分 类 号：TQ317[化学工程—高聚物工业]