Session: 02-03-01: Studies in Aerospace Structural Dynamics

Paper Number: 108295

108295 - Nonlinear Response of Contact Interface With Nanoscale Fractal Roughness Under Harmonic Excitation for Jointed Structures 

Numerous contact interfaces exist between mechanical components of jointed structures. For aerospace structures with precision mechanical parts, the roughness of the contact surface varies from microscale to nanoscale and exhibits self-similarity characteristics. Based on the micro-asperity contact model, the nonlinear dynamics of the micro-roughness contact interface have been studied extensively. However, the dynamic behaviors of contact interfaces with nanoscale roughness are difficult to obtain since the available methods are restricted to micron-scale roughness.

 

Considering the nanoscale fractal roughness of the surface morphology, the present work provides a theoretical method for analyzing the nonlinear response of contact interface under harmonic excitation by combining the molecular dynamics simulation with the multi-scale method. Firstly, the contact interface of the jointed structure is simplified as the contact between a nanoscale rough surface and a rigid plane. The surface morphology with nanoscale fractal roughness is constructed from the atomic level by controlling the fractal dimension and the fractal roughness simultaneously. Secondly, based on the molecular dynamic simulation, the three-dimensional contact model of the nanoscale roughness interface is established, and the fitting relationship between the normal contact force and the equivalent deflection is obtained. Thirdly, the mathematical equation of the contact vibration of the rough interface is proposed, and the multi-scale method combined with the Taylor series is employed to solve the nonlinear differential equation analytically. Finally, variation of the natural frequency with the initial displacement is studied, and the amplitude-frequency response of the rough contact interface under harmonic excitation is revealed.

 

Results show that jointed structures with nanoscale rough morphology exhibit nonlinearity in contact dynamic behaviors. The natural frequency of the rough interface is affected by initial deflections rather than an internal property. 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. Therefore, surface morphology with nanoscale fractal roughness plays a non-negligible role in the dynamical analysis of precision aerospace structures.

Presenting Author: Yunyun Sun Wuhan University

Presenting Author Biography: Dr. Yunyun Sun received the B.E. degree and Ph.D. degree in mechanical engineering from University of Science and Technology Beijing in 2014 and 2020, respectively. She is currently an associate researcher at School of Power and Mechanical Engineering, Wuhan University. Her main research interests are friction, contact mechanics, and contact dynamics of mechanical structures from micro to the nanoscale.

Authors:

Yunyun Sun Wuhan University
Bing Wu Wuhan University
Shijing Wu Wuhan University
Hongguang Li Shanghai Jiao Tong University