Meso-Scale Plasticity and Deformation Processing

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Meso-Scale Plasticity and Deformation Processing Henry T. Y. Yang, University of California, Santa Barbara, CA Srinivasan Chandrasekar, Purdue University, West Lafayette, IN A recently 'discovered' phenomenon with important consequences for plastic deformation at the meso-scale (0.1-10 mm) is strain gradient plasticity, which refers to the collective effects of strain gradient on flow behavior of materials. The discovery of strain gradient plasticity has its origins in measurements, which show that materials display strong size effects in their mechanical response when the characteristic length scale associated with non-uniform plastic deformation is small. Two novel techniques are explored for estimating the flow stress-strain curves of metals and alloys in the presence of strain gradients. The first of these involves simulation and measurement of meso-scale indentation to study the variation of hardness with indenter apical angle. A unique aspect of this approach is the use of cone indenters with different apical angles to impose a wide, but controlled, range of strains and strain gradients in a solid. The second technique involves a study of material response in quasi-static, meso-scale machining where strain gradients are even more intense than in indentation. Here, meso-scale machining is a vehicle for estimating the constitutive stress-strain curve. The research is intended to provide fundamental insights into meso-scale plasticity phenomena; develop and validate techniques for estimating meso-scale flow stress data of relevance to deformation processing; and generate detailed stress-strain data for multi-scale modeling of materials processing operations. These should facilitate the development of sustainable materials processing systems that operate at a high level of efficiency, while creating products of enhanced quality.