Plasticity

I have a fundamental question regarding flow rules of finite plasticity models especially those used in soil mechanics. In most of the papers and books, I have seen the usage of an associated flow rule with the plastic potential similar to the yield surface. However, I am unable to understand the means of obtaining a non-associative flow rule. I am using Abaqus with cap plasticity model (modified Drucker Prager Cap model) to simulate powder compaction process.

I am currently running a Quasi-Static compression simulation in Abaqus Explicit using the Johnson-Cook Plasticity option. As the strain gets beyond the elastic range, the stress-strain response begins to oscillate +- 5 MPa around the expected curve. Does anyone know why this is happening and/or how to repair the problem?

Thanks, 

D. Barrett Hardin

Dear Mechanical Engineers,



It's my pleasure to be one of your group. I have a question in Abaqus Explicit and all my friends recommended me to as iMechanica as the explicit Abaqus is more popular to you than us as civil engineers.

Does anyone knows where I can find any paper discuss the existence of potential functinoal for materials that violate the maximum plastic dissipation principle (due to non-convex yield function and/or non-associately fluw rule)?

There will be a mini-symposium entitled "Defects and Microstructure at the Nanoscale and Beyond," at the USNCCM-10 conference in Columbus, OH, July 16 -19, 2009.  This topic is of keen interest to the I-Mechanica community and we hope many of you will join us there. Our goal is to bring together researchers from the mechanics, materials, and physics communities to cross-fertilize research on defect-mediated processes in microstructural evolution, with a focus on both hard and soft materials. 

Hello,