Thermo - Mechanical Responses of Metals in Small Scale on the Fast Transient Process
Danial Faghihi (ICES - UT Austin), George Voyiadjis (Louisiana State University)
Plasticity at Different Length Scales
Mon 4:20 - 5:40
CIT 219
A higher-order gradient framework is developed in this work accounting for the size and rate effect responses of small volume metallic compounds (e.g. crystal, thin film). The effect of interface (e.g. Grain boundary) on the thermo-mechanical behavior is also included into the formulation, by considering a yield-like higher order boundary condition that allows the interface flow and hardens independently from the bulk materials. The framework is provided based on the decomposition of the mechanical state variables into energetic and dissipative counterparts to address the thermal and mechanical behavior of the metals with small volumes and in the transient time. The highly nonlinear and stiff nature of the micro-force balance partial differential equation is then solved numerically using a commercial finite element code. In this regard, a user element subroutines is developed including additional degrees of freedoms to calculate the gradient values. Using this numerical capability, the major characteristics of the theory are revealed by studying the size and rate effect of crystal structure under various loading. Moreover, the model calculations is compared with the micro-scale test measurements conducted on thin films to investigate the capability of the present framework to capture the main characteristics of the small scale metals.