Taper Effects on Micropillar Compression: A Discrete Dislocation Dynamics Study
Babak Kondori (Texas A&M University), A. Amine Benzerga (Texas A&M University)
Discrete Dislocation Plasticity
Tue 4:20 - 5:40
RI Hall 108
2D discrete dislocation analyses, enhanced by physically based rules to mimic 3D properties of dislocation activity, are used to investigate the effects of taper angle on pillars deformed under uniaxial compression. Pillars with material properties of Al and a height to diameter aspect ratio of 3:1 were compressed at the same nominal strain rate. The size of the compressed pillars (diameter (D) = 0.4, 0.8, 1.6, 3.2, and 9.6 micron) and taper angle ( = 0, 2, 5, and 10 degree) are the variables in this study. Un-tapered pillars show a strong size effect as the diameter is reduced from 9.6 to 0.4 µm. Investigating the evolution of dislocation density and its relation with the macroscopic flow stress suggests that Taylor hardening breaks down at sub-micron scales. The analyses also show that introduction of taper does not amplify the observed size effect. On the contrary, if the taper is severe it leads to flow stress reduction not enhancement. An interpretation of these trends is offered in terms of buildup of net and effective Geometrically Necessary Dislocation (GND) densities.