Nonlinear Response of Contact Interface With Nanoscale Fractal Roughness Under Harmonic Excitation for Jointed Structures

Abstract

Abstract Rough interfaces inevitably exist between precision mechanical parts for aerospace jointed structures. The roughness of the contact surface varies from microscale to nanoscale and exhibits self-similarity characteristics. Since the computational time of molecular dynamics (MD) simulation is generally less than microseconds, the steady-state vibration response of contact interfaces with nanoscale roughness is hard to obtain. Considering the nanoscale roughness of the surface morphology, the present work provides a theoretical method for analyzing the steady-state vibration of contact interface under harmonic excitation by combining the molecular dynamics simulation with the multi-scale method. The surface morphology is constructed from the atomic level, and the contact model of the nanoscale roughness interface is established. The fitting relationship between the normal contact force and the equivalent displacement is obtained. Accordingly, the mathematical equation of the contact vibration of the rough interface is derived. Variation of the natural frequency with the initial displacement is studied, and the amplitude-frequency response of the rough contact interface in steady-state vibration is revealed. Results show that jointed structures with nanoscale rough morphology exhibit nonlinearity in contact behaviors. The natural frequency decreases as the initial deflections deviate from the static equilibrium position. The amplitude jump phenomenon of the rough contact interface is observed under harmonic excitation, and a rougher interface corresponds to a stronger nonlinearity of amplitude-frequency dependence. Reducing the fractal roughness or increasing the fractal dimension of the contact interface may narrow down the excitation frequency range of the main resonance.