Research On Normal Contact And Tangential Friction Characteristics Of Nanoscale Asperity

With the widespread application of Micro-Electro-Mechanical Systems(MEMS)in aerospace,precision manufacturing,and other fields,the performance and lifespan of MEMS have become hot topics in mechanical engineering research.The surface roughness of electronic components in MEMS can reach the nanometer level,and analyzing the characteristics of nanoscale asperity is the basis for studying the entire nanoscale roughness interface,thus providing theoretical references for the design and manufacturing of MEMS.In view of the limitations of finite element methods in studying interfaces at the micrometer scale,this paper uses molecular dynamics methods to study the characteristics of nanoscale asperity and establishes a molecular dynamics model of copper-diamond asperity to simulate the contact and friction processes of nanoscale asperity.Considering the influence of the offset effect on the normal contact characteristics of asperity,the variations in contact parameters such as contact force,contact area,atomic structure,atomic displacement,and temperature with normal displacement are analyzed.In the process of tangential friction,the friction process of nanoscale asperity is simulated by changing the temperature and interference distance,and the variations in contact parameters such as friction force,temperature,and atomic displacement with tangential displacement are obtained.Comparing the molecular dynamics simulation with the microscopic roughness peak contact model,laser confocal microscopy is used to perform morphology testing and feature analysis on the polished smooth copper surface,verifying the feasibility of the molecular dynamics model established in this paper.The following conclusions are obtained:(1)The normal contact force,temperature,contact rate,number of atoms with structural changes,and atomic displacement are monotonically increasing with normal displacement.The offset effect affects the contact characteristics of nanoscale asperity,especially when the normal displacement is large,the normal contact force,contact rate,number of atoms with structural changes,and atomic displacement are negatively correlated with the offset rate w.(2)The tangential friction force and temperature vary non-monotonically with tangential displacement.The tangential friction force,temperature variation,and atomic displacement are positively correlated with the interference distance.The friction force is greatly affected by external temperature,while the temperature variable is less affected by external temperature.(3)Factors such as interatomic interaction force,atomic slip,and atomic structure cause the contact behavior of nanoscale asperity to differ from that of microscopic roughness peak contacts.