I have some problem in defining the material properties using UMAT. I want to simulate the cubic stress-strain traction-sepration law. Solution doesn't converge after max load is applied (i.e zero slope of stress-strain plot). I am using riks solver. I have written my stress -strain relationship as below in UMAT file. Please tell me how to converge the solution even after zero slope of stress-strain relationship. Can i make my load factor(lambda) negative in riks option.

A graduate student researcher is sought to work on a theoretical and computational aspect of multiscale/ multi-physics material modeling (with an emphasis on biological materials and structures). The project’s envisioned outcome is to a better understanding of the relationship between the small scale physics and structures and the overall macroscopic properties of a material. This research has application in the design of new, smart material, or in the development of treatment for injuries and disease of biological tissues.

Carbon nanotubes as strong fibers in CNT-composites are subjected to large deformations in radial direction. They provide strength as well as structural damping in the composite. Despite being strong in the axial direction, CNTs are rather soft in the radial direction.

Many researchers have already used micromechanical modeling techniques such as Mori-Tanaka (M-T), Self-consistent methods and dilute inclusion models depending on volume fraction and shape of the inclusions, etc., to predict the overall mechanical properties of CNT/polymer composites.  However, we know that at nano scales the phenomenological behavior of material is different in comparison with micro or macro scales. Although the effects of waviness, interactions, agglomeration, etc.

One of the things that I've thought about often in relation to mechanics is:

It has come to our attention that some users cannot post comments using Internet Explorer and Chrome.  We find that Firefox works well.

The research funding environment we are all experiencing is extremely frustrating, and has the potential for long-term damage to academics and the nation. You may be interested in reading the letter to the Wall Street Journal by two Nobel Prize winners, David Baltimore and Ahmed Zewail.

Hi everybody.  My name is Ada. I am a new user on this forum.

I am working with microcantilevers (MCs). Recently I experienced lack of sensitivity. I use  MCs coated with nanostructured gold and I use SAM to attach different biological molecules e.g. Protein A, IgG, antiIgG. Everything was working fine until recently.

Would enybody have any sugestions what might be wrong?

Thanks,

Ada 

Professor Ed Berger, Univeristy of Virginia Mechanical Engineering, is featured in the Chronicle of Higher Education for his use of web technologies and, in particular, "video solutions" for teaching undergraduate mechanics courses.