Plasticity

Harold S. Park's picture

SES 2011: Minisymposium on Mechanics of Crystalline and Composite Nanostructures

Dear Colleagues:

We would like to invite you to submit an abstract for the upcoming 2011 Annual Technical Meeting of the Society of Engineering Sciences (SES 2011), to be held October 12-14, 2011, at Northwestern University in Evanston, Illinois (http://ses2011.org/).  The area of the minisymposium is "Mechanics of Crystalline and Composite Nanostructures", and we anticipate having a diverse and well-respected group of theoreticians and experimentalists give presentations on this subject.  Abstracts can be submitted by going to the following conference website:

http://ses2011.org/submit_abstracts.php

where our minisymposium is labeled 3.1.  We look forward to seeing you at Northwestern in the fall of 2011!


Plotting the Johnson-Cook strength model

I'm trying to plot the stress-strain curve described by the Johnson-Cook strength (and eventually damage) models. The strength model is defined as:

σ=[A+Bεn][1+C ln(ε_dot*)][1-T*m]

where A, B, C, n, and m are material constants, ε_dot* is the non-dimensionalized strain rate, and T* is the homologous temperature where T*=(T-T0)/(Tmelt-T0)

To calculate the thermal softening (term in the last bracket of the J-C model), I need to determine the increase in temperature related to an increase in stress (and strain). I'm using the following equation:

ΔT=∫ Χ (σ/(ρ*cp)) dε


Variable Elasticity (Young) Modulus

I need to simulate a sheet forming but I must consider the variation of Young modulus with plastic strain.

Has anybody tried this? How can I implement a function for this? I have never worked with UMAT / VUMAT.

Thank you. 


A fundamental question in thermodynamics for rate-independent plasticity

Hi everyone!


Kejie Zhao's picture

Large Plastic Deformation in High-Capacity Lithium-ion Batteries

Evidence has accumulated recently that a high-capacity electrode of a lithium-ion battery may not recover its initial shape after a cycle of charge and discharge.  Such a plastic behavior is studied here by formulating a theory that couples large amounts of lithiation and deformation.  The homogeneous lithiation and deformation in a small element of an electrode under stresses is analyzed within nonequilibrium thermodynamics, permitting a discussion of equilibrium with respect to some processes, but not others.  The element is assumed to undergo plastic deformation when the stresses reach a yield condition.  The theory is combined with a diffusion equation to analyze a spherical particle of an electrode being charged and discharged at a constant rate.  When the charging rate is low, the distribution of lithium in the particle is nearly homogeneous, the stress in the particle is low, and no plastic deformation occurs.  When the charging rate is high, the distribution of lithium in the particle is inhomogeneous, and the stress in the particle is high, possibly leading to fracture and cavitation. 


Amit Acharya's picture

Characterization of residual stress fields in nonlinear elasticity; a question posed by Sebastien Turcaud

In the post

 http://www.imechanica.org/node/9509

Sebastien Turcaud asks the question (my interpretation) of the characterization of  all possible residual elastic distortion fields on a given configuration (interpreted as the current configuration). If one in addition introduces a reference configuration then the deformation gradient w.r.t. this reference is known and depending upon how one defines 'eigendeformation' in nonlinear elasticity, corresponding eigendformation fields to the residual elastic distortion fields can be determined. Such eigendeformation fields can contain fields arising from plastic deformation, non-uniform thermal expansion etc.


Jianyu Huang's picture

Surface mediated plasticity in sub-10-nm-sized gold crystals

Nature Communications 1, Article number:144 | DOI:10.1038/ncomms1149

Although deformation processes in submicron-sized metallic crystals are
well documented, the direct observation of deformation mechanisms in
crystals with dimensions below the sub-10-nm range is currently lacking.
Here, through in situ high-resolution transmission electron
microscopy (HRTEM) observations, we show that (1) in sharp contrast to
what happens in bulk materials, in which plasticity is mediated by
dislocation emission from Frank-Read sources and multiplication, partial
dislocations emitted from free surfaces dominate the deformation of


Lee Margetts's picture

Soil Mechanics and Fossil Dinosaur Trackways

My PhD student Peter Falkingham (who graduated 15 December 2010) has published some interesting papers on Dinosaur Trackways. These might be of interest to those teaching Soil Mechanics, to give some examples that might be more stimulating than foundation design or traditional geotechnical engineering.

References below:


CanhLe's picture

Research associate position at University of Sheffield

The successful candidate will work on the EPSRC funded research project 'Ultimate and permissible limit state behaviour of soil-filled masonry arch bridges', which is being undertaken in collaboration with the University of Salford and various industrial partners (Network Rail, ADEPT, the International Union of Railways and Balfour Beatty Rail). This is an exciting opportunity to help develop the next generation of analysis and assessment techniques for masonry arch bridges, thus helping to ensure a sustainable future for structures that continue to form a vitally important part of the rail and regional road networks of the UK and other countries.


S. Beretta's picture

Research assistant and PhD position at PoliMi on micro-plasticity models

In the last decade, different
cyclic plasticity models
, based on the “continuum” approach, have been proposed
in order to account for different mechanical effects (such as ratchetting,
strain range dependence, non-proportional loading and memory effect), [1, 2]. A
disadvantage of this approach is the elevated number of model parameters
introduced in order to correctly predict the material behaviour. The determination
of these parameters, usually difficult and expensive,
is one of the reasons why the modern
constitutive models are not widely used in finite element simulations of


Robin Selinger's picture

APS March Meeting Focus session: "Fracture, Friction, and Deformation Across Length Scales"

Abstracts due Friday, Nov. 19, 2010 

APS March Meeting Focus session: "Tribophysics: Friction, Fracture and Deformation Across Length Scales"

March 21 - 25, 2011, Dallas, Texas
Details at
http://www.aps.org/meetings/march/scientific/focus2.cfm#12.7.3

Invited speakers: Michael Marder (Univ. of Texas); Julia Greer (Caltech)

Organizers: Robin Selinger (Kent State), Jacqueline Krim (NCSU), Noam Bernstein (NRL)


Amit Acharya's picture

Microcanonical Entropy and Mesoscale Dislocation Mechanics and Plasticity

(Journal of Elasticity, Carlson memorial Volume)

A methodology is devised to utilize the statistical mechanical entropy of an isolated, constrained atomistic system to define the dissipative driving-force and energetic fields in continuum thermomechanics. A thermodynamic model of dislocation mechanics is discussed. One outcome is a definition for the mesoscale back-stress tensor and the symmetric, polar dislocation density-dependent, Cauchy stress tensor from atomistic ingredients.


Plasticity Data in Vumat

Hello everyone,

  I am using a VUMAT with isotropic hardening in my three dimensional model. Can someone tell me how is plasticity data passed into this subroutine? In VUMAT for kinematic hardening we define the yield stress and hardening modulus along with E and poisson's ratio in *User Material. I did not find any isotropic hardening VUMAT examples in manual. Do we define the hardening modulus or the yield stress-plastic strain data in isotropic hardening VUMAT? I will be really thankful if anyone can help me.

 

Thank you

Swapnil


Disparity in Simple Shear solution in ABAQUS

Dear All,
We tried to simulate simple shear using ABAQUS and compared it with the analytical solution. To our surprise, even though the equivalent stress and strain matched perfectly, the component stress and strain had a large deviation between the semi analytical and ABAQUS methods. The zero components in the analytical model were calculated to be non-zero in the results of ABAQUS. This paradox could not be understood clearly as whether it is a case of software deficiency or conceptual error. A COMPLETE ANALYSIS OF THE PROBLEM IS ATTACHED AS A REPORT.
 
I have asked for technique support. Their answer was that my strain rate was incorrect for finite deformation. But I do not think so.


Eran Bouchbinder's picture

A new postdoc position is available

A new postdoctoral position in continuum mechanics is available at the Weizmann Institute of Science. Candidates should have a strong background in physics and/or theoretical mechanics, as well as experience with analytical and computational methods for solving partial differential equations. Possible projects include the mechanics of frictional sliding, the mechanics of biomaterials, the mechanics of glassy materials and dislocation-mediated plasticity. Highly motivated candidates are requested to send their CV, publications list and statement of research interests to Dr. Eran Bouchbinder eran.bouchbinder@weizmann.ac.il


vicky.nguyen's picture

Mechanics of Materials: Textbook Recommendation

I will be teaching a sophomore level class  mechanics of materials class.  The class will cover mechanics of basic strength of materials (e.g. beams, pressure vessels), but I also want to teach basic elements of failure mechanics (fracture, fatigue, plasticity, and wear.)  I'm looking for a recommendation of an undergrad mechanics textbook that covers the fracture, fatigue, plasticity, and wear.  The students will have had a statics and mechanics class and their textbook already covers strength of materials.  Thanks.


Shabeer Khan's picture

plasticity

Good Time to Everybody, I am working on Thermoplasticity, especially thermoviscoplasticity, will be comparing the results of some basic examples problem worked be Simo and Miehe, modelled in Abaqus with the results of a locally developed code. I am new comer in this excellent forum and I am happy to see myself among a nice community of Mechanicians. I regard all those who are conneted in this form and those who helped in connecting this chain of  Mechanics.

 


Amit Pandey's picture

Evoution of Yield surfaces: Past and Future Trend - Part 2

Continuing on the work from the previous thread posted on

http://imechanica.org/node/9016

 Results are presented on the evolution of subsequent yield surfaces with
finite deformation in a very high work hardening annealed 1100 aluminum
alloy. In Part I [Khan, A.S., Kazmi, R., Stoughton, T., Pandey, A.,
2009a. Evolution of subsequent yield surfaces and elastic constants with
finite plastic deformation. Part 1: a very low work hardening aluminum
alloy (Al-6061–T6511) 25, 1611–1625.] of this paper, similar results are
presented for a very low work hardening aluminum alloy.


A. Amine Benzerga's picture

How do ductile materials fail?

This is a review on ductile fracture committed to the Advances in Applied Mechanics (Vol 44). Part of the review has an educational purpose and, as such, is intended for advanced undergraduates and starting graduate students. The other part is an account of recent research conducted in the field.

Though quite long, the review is by no means exhaustive. As noted in the discussion, many valuable contributions to this field have been left out. The focus was laid on micromechanics-based approaches to connect to microstructural aspects in engineering materials.

 I will try to post the electronic PDF once I get permission from Elsevier. 


johnsmart1987's picture

plasticity induced fatigue crack closure

hi friends am doin my my project on" FEA of plasticity induced crack closure". my specimen size is 80*80 mm. by using symmetry condition i modelled 1/4th of model in ANSYS. therfore i created 40*40 mm plate. with initial crack length of 4mm.means its MT specimen of 80*80mm with 8 mm crack length, by symmetry condition i modelled 40*40 with 4mm crack lenth.


Low cycle fatigue/Ratcheting

Hi viewers,

I am working with  abaqus 6.7 software. I wish to simulate uni-axial tension and compression cyclic analysis. My objective is to predict the response of steel subjected to cyclic load and in particular, to predict ratcheting effect. I am also interested to draw S-N curve, stress-strain curve, ratcheting behaviour, etc. from the result of the analysis. I tried to simulate an axi-symmetric model and job submission is successfully completed. But I am not aware of the fact that how the  results of analysis can be retrieved to draw the above mentioned curves, please specify how the 'no.of cycle' data can be obtained.

 

Pradip 


S-N curve

I am working on plastic behaviour of metal. I am using Abaqus 6.7 for simulation of uniaxial ratcheting of steel under cyclic loading. Modelling and job submission/completion has been done successfully. But I cann't understand  where  the data for Stresses(S) &  number of cycle(N) is strored to draw S-N curve. Please suggest.


concrete damaged plasticity considering strain rate

Hi all,

Concrete is sensitive to strain rate. I want to create a model for a reinforced concrete plane frame. The material model used for concrete is concrete damaged plasticity, and the element type is B21. I want to consider strain rate effects of concrete(strength). The problem is that ABAQUS can not work after considering strain rate effects of concrete when the concrete yields. Can you help me? Thank you in advance.


help about secnd order effect in columns

ello all,

I am an M.S student, my subject in modelling of high strength concrete column under eecentric loading. I made a model of reinforced

 concrete column with in ANSYS by solid65 to represent concrete and link8 for steel.

My model is 200*200*4000 mm, i choose multi., conc.,and elastic linear for concrete, closing crushing for it, for steel bilinear, elastic.

Slenderness ratio (l/d)=20 Although Using large displacement analysis option, model give me very small displacement (less than


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