Molecular Dynamics Simulation of Normal Contact Characteristics Between Nanoscale Rough Surfaces
The use of precision instruments facilitates the miniaturization of mechanical components,enhancing their efficiency and performance.Deformation at contact interfaces composed of mechanical components essentially derives from the interaction between nanosized asperities.Under external loading conditions,the presence of these nanosized asperities on rough interfaces can significantly reduce the actual contact area compared to the nominal area,leading to the localized stress concentration within the contact region.Similarly,contact parameters such as the normal contact force,contact pressure,and deformation directly impact the operational lifespan of mechanical components.Establishing an equivalent mechanical model for rough interfaces is a prerequisite to elucidate the underlying deformation mechanisms governing contact behaviors at the nanoscale.Therefore,understanding the normal contact behavior between nanoscale rough interfaces under various external loading conditions is crucial.At the nanoscale,the dispersion of atoms leads to the breakdown of the continuum mechanics theory.However,studies investigating the mapping relationship between the nanoscale roughness morphology and contact parameters are limited.In addition,very little information is available on the dynamic variations in the contact parameters of nanoscale rough interfaces under different applied loads.Furthermore,the application of the finite element method is restricted to microcontact processes and does not encompass contact analysis at the nanoscale.With advancements in computer technology,molecular dynamics has emerged as a widely employed approach for investigating nanoscale contact behaviors.The normal contact behaviors between nanoscale rough interfaces have been investigated through molecular dynamics simulations.First,random rough surfaces are constructed by applying an inverse Fourier transform to the surface power spectral density function,thereby establishing a molecular dynamics model for normal contact between nanoscale rough copper-diamond interfaces.Subsequently,the dynamic process of normal contact between nanoscale rough interfaces is simulated at an atomic scale.The dynamic variations in key parameters such as the normal contact force,actual contact area,and interface equivalent deformation are analyzed under various external loads.Finally,comprehensive simulations are conducted to study the normal contact process between nanoscale rough interfaces with varying surface roughness,inducing the establishment of a mapping relationship between the equivalent deformation and actual contact area.The results provide a qualitative understanding of the normal contact characteristics of nanoscale rough interfaces.The applied load shows a positive correlation with the normal contact force,actual contact area,and contact deformation when the surface roughness remains constant.This finding is consistent with the observed characteristics of interfaces featuring micron-scale roughness.Under identical loads,the surface roughness of the contact interfaces increases,resulting in reduced resistance to the deformation of nanosized asperities and facilitating deformation.This results in a decrease in the number of atoms in contact as well as a reduction in both the magnitude of the normal contact force and the size of the effective contact area.At the nanoscale,surface morphology significantly influences interatomic forces.As the contact interface becomes smoother,the interaction force between the atoms intensifies,leading to a wider fluctuation in the normal contact parameters such as the normal contact force and actual contact area.The actual contact area of the nanoscale rough interfaces exhibits a power-law mapping relationship with the equivalent deformation under external loading.Moreover,larger surface roughness leads to a smaller contact area.Normal contact analysis of nanoscale rough interfaces reveals variations in key parameters,including the normal contact force,actual contact area,and equivalent deformation under an external load.The establishment of a mapping relationship between the surface morphology and contact parameters not only offers a theoretical framework for investigating micro-nano scale contact behaviors but also provides invaluable support for enhancing the interface characteristics of precision instruments.
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