Plasticity

Hi all,

      I doing modelling on soft clay behaviour which exhibit softening behaviour during constant strain loading. Here i followed a non-associated flow rule for better prediction of dilation . For the case of non-associated flow rule yield function and plastic potential function should not same i clear in that , my doubt is that we can use two different surface for yield and plastic potential function (eg: linear surface as yield surface and elliptical surface as plastic potential )? 

Hello,

I am trying to derive/find an analytical expression
for the torsion of a round bar made of an heterogeneous material. But I just do
not seem to find any solution available in the literature other than for a
homogeneous material, which can be find in any theory of plasticity book (e.g.
Theory of Plasticity, 3rd Ed., J. Chakarabarty, pp. 132-136).

Dear all,

Is there any one of you know a material model which can reflect the orthotropic , hysteresis, and load ratio dependence behaviors? 

Every helps would be highly appreciated.

Kindest regards,

Ken

Dear Colleagues,

I would like to invite to you to submit an abstract to the mini-symposium on 'Cyclic Plasticity Models for Sheet Metal Forming' at the 9th International Conference on Numerical Simulation of 3D Sheet Metal Forming Processes (NUMISHEET) to be held at Melbourne - Australia January 6-10, 2014 (http://www.numisheet2014.org). 

Dear Colleagues,

The new deadline for abstract (plain text, 400 word limit) submission is now January 28, 2013.

The 4th conference "Nonlinear Dynamics -2013" will be held from 19 until 22 June, 2013 in Sevastopol (Ukraine).

Conference web-site: https://sites.google.com/site/ndkhpi2013/home

The conference is organised by:

In this paper, dislocation climb is incorporated in a two-dimensional discrete dislocation dynamics model. Calculations are carried out for polycrystalline thin films, passivated on one or both surfaces. Climb allows dislocations to escape from dislocation pile-ups and reduces the strain-hardening rate, especially for fully passivated films. Within the framework of this model, climb modifies the dislocation structures that develop during plastic deformation and results in the formation of pile-ups on slip planes that do not contain any dislocation sources.

Now I am doing some work about nanotwinned copper, and don't understand what's the nature of "detwinning". 

Could any disappearance of the original nanotwin structure and the formation of a single grain or a new twin structure with TBs in a different orientation and/or with different TB spacing be called detwinning?

While reading the article

"An alternative approach to finite plasticity based on material isomorphisms " (1999) by Prof. Bertram, the first thing that attracted my attention was the quote [by Prof. Naghdi (late)]:

 “there is some degree of disagreements on nearly all of the main constitutive ingredients and features of plasticity in the presence of finite deformation... Some of the issues of disagreements are of basic and fundamental importance.”

Hi,

I'm presently working on implementing anisotropic yield criteria in LSDYNA as UMAT.

I understand from the LSDYNA documents that effective plastic strain is a default history variable.  So when we code, can we omit the update of effective plastic strain as a history variable? If so, where is it stored and how is it retrieved during post-processing ?