Woodruff School of Mechanical Engineering
COE/Structural Mechanics Seminar
Micromechanics of Magnesium Gleaned from Multi-scale Experiments and Modeling
Prof. Shailendra Joshi
Department of Mechanical Engineering, National University of Singapore
Friday, July 26, 2013 at 3:00:00 PM
MRDC Building, Room 4211
Dr. Surya Kalidindi
Magnesium (Mg) is a potential candidate for structural applications ranging from fuel-intensive automotive sector to biomedical components, due to attractive properties such as low mass density (~ 35 % lighter than aluminum), high damping capacity and excellent biocompatibility. There has been a renewed emphasis toward developing novel Mg microstructures with enhanced mechanical characteristics through a variety of techniques such as structural and microstructural miniaturization, nano-reinforced composites, and several more. This talk presents our on-going experimental and computational efforts toward designing strong and ductile Mg microstructures by interrogating the fundamental mechanics of this low symmetry HCP material. First, we present a novel hierarchical nano-composite where the pure Mg matrix hosts a dilute fraction of reinforcement that is itself a composite at a finer scale. These hierarchical Mg configurations exhibit significant enhancement in the strength and ductility over their monolithic counterpart. We briefly discuss the length-scales involved in these highly heterogeneous microstructures and their influence on the macroscopic characteristics. Next, motivated by the overarching need to understand the microscopic underpinnings of the macroscopic behaviors in Mg, we discuss a crystal plasticity model that incorporates constitutive descriptions for the slip and twinning mechanisms and interactions thereof. In particular, the model emphasizes the differences between tension and compression twin evolution characteristics and their roles in the slip and twin hardening. The computational results are compared with the macroscopic and microscopic characteristics observed in different experiments on single and polycrystalline specimens. Finally, we present some of our recent results from the molecular dynamics simulations that enable insight into developing improved coarse-grained constitutive descriptions for slip and twinning.
Shailendra Joshi is an Assistant Professor in Mechanical Engineering at the National University of Singapore (NUS). Prior to joining NUS, he was a post-doctoral fellow (2005-2008) in the Department of Mechanical Engineering at The Johns Hopkins University. He earned his PhD in Civil Engineering from Indian Institute of Technology-Bombay in 2002. After a short stint as a visiting scientist at University of Stuttgart (2002), he worked as a research engineer at GE-India Technology Center in Bangalore, India (2003-2005). His current research focuses on the computational and experimental mechanics of strengthening and failure in advanced materials over a range of length- and time-scales to enable designing light-weight materials with impressive mechanical behaviors. He is an editorial board member of Materials Science and Engineering - A, an Elsevier journal. Shailendra enjoys playing amateur squash.
Refreshments will be served.