A New View of Incipient Plastic Instability during Nanoindentation *Supported by the Key Program of the National Natural Science Foundation of China under Grant Nos 11132006 and 11302115. (March 2017)

• Record Type: Journal Article
• Authors: Hu 胡, Jian-Qiao 剑桥; Liu 柳, Zhan-Li 占立; Cui 崔, Yi-Nan 一南; Liu 刘, Feng-Xian 凤仙; Zhuang 庄, Zhuo 茁
• Is Part Of: Chinese physics letters. Volume 34:Number 4(2017:Apr.)
• Publication Date: 2017-03
• Subjects: 61.72.Hh -- 62.20.fq -- 62.20.F-; Physics -- Periodicals; Electronic journals; 530.05
• DOI: 10.1088/0256-307X/34/4/046101
• Languages: English
• ISSNs: 0256-307X

Abstract

Abstract : Whether the dislocation nucleation or the sudden dislocation multiplication dominates the incipient plastic instability during the nanoindentation of initial defect-free single crystal still remains unclear. In this work, the dislocation mechanism corresponding to the incipient plastic instability is numerically investigated by coupling discrete dislocation dynamics with the finite element method. The coupling model naturally introduces the dislocation nucleation and accurately captures the heterogeneous stress field during nanoindentation. The simulation results show that the first dislocation nucleation induces the initial pop-in event when the indenter is small, while for larger indenters, the incipient plastic instability is ascribed to the cooperation between dislocation nucleation and multiplication. Interestingly, the local dislocation densities for both cases are almost the same when the sudden load drop occurs. Thus it is inferred that the adequate dislocations generated by either nucleation or multiplication, or both, are the requirement for the trigger of incipient plastic instability. A unified dislocation-based mechanism is proposed to interpret the precipitate incipient plastic instability.