Amit Acharya and Robin J. Knops
(to appear in Journal of Elasticity)
The common practice of ignoring the elastic strain gradient in measurements of geometrically necessary dislocation (GND) density is critically examined. It is concluded that the practice may result in substantial errors. Our analysis points to the importance of spatial variations of the elastic strain field in relation to its magnitude in inferring estimates of dislocation density from measurements.
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.
This paper has appeared in Journal of Applied Physics. You can download it from here .
This classic paper is attached
Full scholarships available at European Commission funded workshop on fracture and damage mechanics in Antalya / TurkeySubmitted by Tuncay Yalcinkaya on Tue, 2012-11-06 10:05.
European Commission' s JRC (Joint Research Centre) is organizing the 2nd workshop on physics based modeling of material properties and experimental observations in collaboration with TOBB University of Economics and Technology. The workshop will be held in Antalya/Turkey on 15-17 May 2013, and the special focus will be fracture and damage mechanics.
The Organizing Committee of the 4th conference ND-2013 is pleased to invite you to participate at the Nonlinear Dynamics Conference to 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:
- National Technical University "KhPI" (Kharkov, Ukraine)
- McGill University (Montreal, Canada)
- Institute of Mechanics, National Academy of Sciences of Ukraine (Kiev, Ukraine)
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.”
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 ?
In addition to the above, What should we enter in the 'NHV' - number of history variables in the input deck? Should we include effective plastic strain or is it suficient to worry only about the additional history variables we enter (assuming we need not update eff. plastic strain as a separate histroy variable )
By Laurence Brassart and Zhigang Suo
A postdoctoral researcher position is available in the area of sheet metal forming, plasticity theory, computational modeling of forming of advanced high strength steels, light-weight alloys at POSTECH (Pohang University of Science and Technology) working under the supervision of Prof. Myoung-Gyu Lee. He/She will also work with Prof. Frederic Barlat who is a world famous scholar in the field of plasticity. Candidates with a strong background in plasticity theory, computational mechanics of sheet metals, failure analysis are highly encouraged to apply. Applicants must provide a detailed CV including experience and qualifications, list of publications, and research plan.
Acharya, A., Jump conditions for GND evolution as a constraint on slip transmission at grain boundaries, Philosophical Magazine, 87(8-9), 1349-1359, 2007 (see attachment)
In my research i am trying to develop a new model for plastic deformation, and i suspect there is a strong similarity between
plasticity and turbulent flow !.
My question is: if there is workd done trying to apply Reynolds decomposition (Reynolds Stress) to the governing equations and solved plasticity problem in Solids?
ANSYS, Inc. has an immediate job opening in Houston, TX for a Technical Services Engineer. This is a full time position.
The job entails providing advanced technical guidance on various aspects of computational Structural Mechanics to clients in industry and academia.
A new paper concerned with Nanoscale analysis of plasticity and fracture of the sheet metal is published in ICCS proceedings and available at:
Full scholarships available at European Commission funded workshop on physically based material modelingSubmitted by Tuncay Yalcinkaya on Thu, 2012-07-19 09:25.
European Commission' s JRC (Joint Research Centre) is organizing a workshop on physics based modeling of material properties and experimental observations in collaboration with METU (Middle East Technical University). The workshop will be held in Ankara on 22-23 October 2012.
Our group at North Carolina State University is hiring PhD students and Post-doctoral Associates in the areas of multiscale modeling, computational mechanics, fracture, and plasticity.
Interested parties should email firstname.lastname@example.org, and send a cv with a few representative publications.
I would like to seek comments on : Room temperature stress relaxation and governing mechanisms that contribute to the plasticity that occurs during this process. As, most of the available work on relaxation is done at elevated temperatures.
Please check more on this thread by hari@
I have also attach papers by Prof Hart and Prof Krempl that did throw some light on this particular subject.
Attached herewith a classical paper by Hart on introducing a concept of constant hardness curves refuting that absolute strain should not be considered as a state variable.
The objective of the workshop, co-organized by Joint Research Centre of the European Commission and Middle East Technical University, is to discuss the present status of physics based constitutive modelling of metallic materials and associated experimental methods.
The Workshop is funded by the European Commission's Integration and Enlargment Programme. There is no cost for attending the Workshop. A limited number of scholarships is available for participants from the target countries (see attached flyer).
Is there a place I can find explained examples or tutorials on how to model user defined creep in ANSYS?
I need to follow the creep law __> effective creep strain (e at time t) = S. T. e^(-H)
S=(a0)^t.(sigma)^(a1) ; T = t^(a2)+(a3).t^(a4)+(a5)t^(a6) ; H = (a7)/[(theta)+273.16]
a0 to a7 are material constants.
I have the experimental data and tried to fit the curve in Ansys to obtain the material constants.
I tried to follow the ansys help file steps. But facing erros messages.
If any one could give me a sample apdl code it would be helpful.
We are pleased to announce the forthcoming Summer
School on “Hardening and Damage of Materials under Finite Deformations:
Constitutive Modeling and Numerical Implementation”, which will take place in
Dortmund, Germany from September 3rd to 7th, 2012 and is organized by Prof.
Dr.-Ing. A. Erman Tekkaya of TU Dortmund and Dr. Tudor Balan of LEM3,