Seminar on Novel approach to characterize the plastic flow under Berkovich and Spherical indentations

Dr K. Eswar Prasad

Assistant Professor 

Department of Metallurgical and Materials Engineering, Indian Institute of Technology Indore

It is well established in the literature that the indentation hardness, H, directly scales with the flow stress of materials. Although this is valid for amorphous and polycrystalline FCC and BCC materials, limited investigations are available to test the validity of this relation for low symmetric hexagonal close-packed materials such as Magnesium and its alloys which exhibit complex plastic flow characteristics. Our uniaxial compression and indentation experiments on Magnesium single crystals of different orientations show that these crystals exhibit similar hardness values despite exhibiting a marked difference in flow stress suggesting that the hardness to strength conversion is not straightforward in these materials. The differences in flow stress values between the different orientations can be explained by Schimd factor analysis but there are no mathematical models available to explain the similarity in hardness between different orientations under Berkovich indentation. We have developed a mathematical framework to investigate the deformation response under the Berkovch indenter which explains the similarity in hardness values between different orientations. I will discuss these results in my presentation.

Dr Eswar is currently an Assistant Professor in the Department of Metallurgical Engineering and Materials Science Engineering at IIT Indore. Prior to joining IIT Indore, he worked as an Assistant Professor at the School of Engineering, Mahindra Ecole Centrale, Hyderabad. He was a postdoctoral fellow in Prof. KT. Ramesh's group at Hopkins Extreme Materials Institute, Johns Hopkins University (JHU) from 2011-2014. Prof. Eswar did his PhD from the Department of Materials Engineering, Indian Institute of Science under the supervision of Prof. U. Ramamurty. His research interests lie in understanding the deformation behavior of materials at different length and time scales.

As a graduate student he carried out experiments (complementary simulations) and investigated the deformation behavior of advanced materials such as bulk metallic glasses, polymer nano-composites, OFHC copper. His PhD thesis titled "Plastic deformation during indentation of amorphous and crystalline materials" addresses the issues like pressure sensitive plastic flow in amorphous materials at room and high temperatures, role of indenter angle on the plastic zone shape and size in strain hardening materials.