Understanding the linear relation between pop-in excursion length and critical force for spherical nanoindentation

ABSTRACT

Pop-in is a widely observed phenomenon in nanoindentation. In this paper, dislocation evolution in pop-in processes is analysed in detail through molecular dynamics (MD) simulations. We found that a large number of dislocations nucleate homogeneously at the initiation of pop-in, followed by extensive dislocation propagation, which is the dominant mode of plastic deformation during pop-in. Moreover, we noted that establishing the correct dislocation evolution mechanisms of pop-in can serve to explain the overshoot phenomenon observed in nanoindentation experiments. Through our MD analysis on the obtained dislocation structures, therefore, we were able to propose a model that can predict the total length of dislocations associated with the plastic processes underneath a spherical indenter. In addition, the Taylor model was used to verify that our proposed dislocation length model sits well with the MD simulated force-displacement curves of nanoindentation. In fact, the MD simulated linear relation between critical force and indentation depth during pop-in is consistent with the Hertzian and Taylor models. Our MD simulations, therefore, can provide significant insight into the experimentally observed pop-in phenomena.

KEYWORDS:

• Nanoindentation
• molecular dynamics
• pop-in
• dislocation structures
• Taylor models

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The financial supports from National Natural Science Foundation of China (NSFC) under grant Nos. 11872139 and 51671039, and Open Project of State Key Laboratory of Superhard Materials (Jilin University) (201905) are appreciated. Ling Zhang wish to thank the financial support of The National Key Research & Development Program of China (No.2016YFB0700403) and Project No. 2020CDJDPT001 supported by the Fundamental Research Funds for the Central Universities.