Multi-scale simulation of nanoindentation

Lingqi Yang, Purdue University

Abstract

In this thesis, two types of contact problems are studied by different methods. In the first, a multi-scale model enables investigation of the effect of surface roughness on adhesive contact. Molecular dynamics simulation captures the atomic-scale effects of individual asperities while a finite element model captures the micro-scale contact mechanics. The relationship between force and distance predicted by the atomistic model is introduced into the finite element model through non-linear hysteretic springs which will be assigned random lengths and distribution to form the rough surface over the finite element model. The multi-scale model predicts how the energy loss, quantified by the hysteresis loop formed by loading and unloading data, is affected by indentation depth and surface roughness. The other contact problem is a practical engineering problem of multiple asperities with random radii and distribution in a contact with a rigid plate that is analyzed via a 2-D finite element model. The solution starts with the investigation of single asperity where the numerical results are verified by the analytical solution of the Hertzian theorem. Then the number of asperities is increased and the load required for a full contact of those asperities is calculated. The results reveal a linear relationship between the load and the number of asperities. In summary, this thesis has presented a detailed analysis on introducing the atomic simulation results into a finite element model. In addition, a much larger engineering model is also built to extend our work for a better understanding of multi-scale simulation of nanoindentation.

Degree

M.S.E.

Advisors

Martini, Purdue University.

Subject Area

Mechanical engineering|Nanotechnology

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