[PO-L1] Poster Session 1

[P1-66] Molecular dynamics study on temperature and loading rate dependence of nano-indentation pop-in load

^○Yuji Sato¹, Shuhei Shinzato¹, Takahito Ohmura², Shigenobu Ogata^1,3 (1.Department of Mechanical Science and Bioengineering, Osaka University, Japan, 2.Research Center for Structural Materials, National Institute for Materials Science, Japan, 3.Center for Elements Strategy Initiative for Structural Materials (ESISM), Kyoto University, Japan)

Nano-indentation test is commonly used to investigate mechanical properties of materials in nano-scale. In nano-indentation test, a displacement burst behavior of indenter, “pop-in”, can be usually observed. Pop-in is considered to be attributable to dislocation nucleation phenomena, thus pop-in can be associated with incipient plasticity in materials. It is well-known that the pop-in occurs when a shear stress along a slip system beneath the indenter reaches near theoretical shear strength. However, the temperature and loading rate dependency of pop-in load is still unclear. In this study, using atomistic simulation with EAM interatomic potentials, we computed stress dependent activation energy of homogeneous dislocation nucleation event in BCC Fe and Ta under actual complex stress condition beneath a spherical indenter. Based on the computed activation energy and stochastic modeling method, temperature and loading-rate dependent probability distribution of the critical indentation load was successfully predicted. Eventually, we compared the atomistic predictions with experiments, and confirmed validity of our atomistic modeling.