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Plasticity

Amit Acharya's picture

Plasticity implies the Volterra formulation: an example

 A demonstration through an example is given of how the Volterra dislocation formulation in linear elasticity can be viewed as a (formal) limit of a problem in plasticity theory. Interestingly, from this point of view the Volterra dislocation formulation with discontinuous displacement, and non-square-integrable energy appears as a large-length scale limit of a smoother microscopic problem. This is in contrast to other formulations using SBV functions as well as the theory of Structured deformations where the microscopic problem is viewed as discontinuous and the smoother plasticity formulation appears as a homogenized large length-scale limit.

Emilio Martínez Pañeda's picture

Crack Growth Resistance in Metallic Alloys: The Role of Isotropic Versus Kinematic Hardening

We have always modelled crack propagation under monotonic/static loading in metals assuming isotropic hardening. However, we show that anisotropic/kinematic hardening effects play a significant role due to non-proportional straining with crack advance; the isotropic hardening idealization leads to steady state fracture toughness predictions that could be 50% lower. I hope that some of you find this work interesting.

Emilio Martínez-Pañeda, Norman A. Fleck. Crack Growth Resistance in Metallic Alloys: The Role of Isotropic Versus Kinematic Hardening. 

rajan_prithivi's picture

Isotropic & Kinematic hardening

This video gives a basic overview of the most fundamental hardening models of plasticity, which are the isotropic and kinematic hardening

 

Hope this helps!

- Prithivi

18-month post-doctorate position at SRMP, CEA/Saclay, France, starting from April 2018

Title of the project: Ab initio modelling of interactions between dislocations and solutes in body-centered cubic metals

Research area: Solid State Physics, Materials Science

Summary of the project:

Jabar's picture

Fracture mechanism in notched metal

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G'day all

Having a metal element with a notch like crack (assume sharp one, exhibits plasticity),  what are the actual fracture mechanism (the phases the crack goes through) in the total fatigue-life. 

please comment on these scenarios:

1- crack initiation life calculated from the (S-N, e-N), then using LEFM/EPFM to determine the cycles for the crack propagation to failure...

Q/ how to find the crack length between the two phases, I mean from which stresses and at which crack length we start the crack propagation life estimation.

ABAQUS - the influence of changing kinematic and cycling hardening parameters

Choose a channel featured in the header of iMechanica: 

Hello,

 

I have recently done a simple hourglass model to check the influence of hardening parameters in Abaqus. The reason was the effects of the parameters' change in bigger models were a bit surprising, therefore I needed to investigate the reason using some simpler model. Please see file 1.

 

After performing tension/compression cycles I got results as shown in files 2, 3, 4 and 5. Please note that only the hardening parameter in the description changes, the other three stays the same for each series.

 

rajan_prithivi's picture

Basics of plasticity theory in 6 min

This video explains the very fundamental points with regard to plasticity theory. It covers the following -

 

1) Why study plasticity ?

2) Additive decomposition of strain

3) stress and strength

4) Yield condition , flow rule & hardening rule

 

-Prithivi

Bin Liu's picture

How to Realize Volume Conservation During Finite Plastic Deformation

Volume conservation during plastic deformation is the most important feature and should be realized in elastoplastic theories. However, it is found in this paper that an elastoplastic theory is not volume conserved if it improperly sets an arbitrary plastic strain rate tensor to be deviatoric. We discuss how to rigorously realize volume conservation in finite strain regime, especially when the unloading stress free configuration is not adopted in the elastoplastic theories.

WaiChing Sun's picture

WCCM Mini-symposium 1701: Computational Geomechanics

Dear colleagues:

We invite you to present a talk within the Computational Geomechanics mini-symposium (Session ID: 1701) at the World Congress on Computational Mechanics (WCCM XIII) in New York City from July 22-27th, 2018. The call for abstracts will be open between October 15 and December 31, 2017. The mini-symposium description is provided below.

Session Description:

Postdoc seeking in field of Mechanical or Materials Science Engineering

My name is Lifei Wang, from China. I am 28 years old, and I have been finished my P.H.D degree in July 2015.   Now I'm looking for a postdoc research position in the field of Mechanical or Material Science Engineering. 

Multi-scale finite element modeling of magnesium medical devices

<p>Applications are invited from suitably qualified candidates for two full-time Postdoctoral Researcher positions on the finite element simulation of magnesium orthopaedic implants. These three year fixed term positions are funded through a US-Ireland R&amp;D Partnership Programme involving collaboration between the SFI Centre for Research in Medical Devices (Cúram), the NSF Engineering Research Centre Revolutionizing Metallic Biomaterials (RMB, USA), and the Nanotechnology and Integrated Bioengineering Centre (NIBEC, Northern Ireland).

Haoran Wang's picture

Nanoscale Mechanics of the Solid Electrolyte Interphase on Lithiated-Silicon Electrodes

Hello Imechanica community, we have just published our study on the mechanics of SEI in Li-ion batteries. Please find the abstract and link as below. 

 

Abstract:

Multi-scale finite element modelling of magnesium medical devices

Applications are invited from suitably qualified candidates for two full-time Postdoctoral Researcher positions on the finite element simulation of magnesium orthopaedic implants. These three year fixed term positions are funded through a US-Ireland R&D Partnership Programme involving collaboration between the SFI Centre for Research in Medical Devices (Cúram), the NSF Engineering Research Centre Revolutionizing Metallic Biomaterials (RMB, USA), and the Nanotechnology and Integrated Bioengineering Centre (NIBEC, Northern Ireland).

Interested candidates should send a CV to patrick.mcgarry@nuigalway.ie

The start date for both positions is September-November 2017.

Nonlinear programming and closest point return plasticity

New article:  Nonlinear programming and closest point return plasticity http://www.parresianz.com/mechanics/plasticity/algorithm/primal-dual-closest-point-return/

This article tries to justify the use of backward Euler stress updates.

-- Biswajit

Sharlotte Kramer's picture

Sandia Fracture Challenge: Survey

The Sandia Fracture Challenge (SFC) was issued in December 2016, and the SFC supplemental information became available in February 2017.  The predictions are due July 15th, 2017.  We would appreciate feedback from you regarding the Challenge prior to the return of the predictions.   Please email Sharlotte Kramer (slkrame@sandia.gov) and Brad Boyce (blboyce@sandia.gov) with (1) your intent to participate in this SFC and/or (2) any comments you may have on the Challenge.

Sharlotte Kramer's picture

Sandia Fracture Challenge Update

Supplemental information for the third Sandia Fracture Challenge (SFC) is now available!  We have compiled the supplemental information promised in the original information packet and some additional information based on questions we received from participants.  The supplemental information includes electron backscatter diffraction (EBSD) data on the Challenge geometry, additional base material tests, raw DIC images and examples of DIC analyses of base material tests, and additional boundary condition information.

Drucker Prager Plasticity model

Hi All,

I am trying to code the Drucker prager plasticity model for the 2D plane strain case using consistent tangent modulus. I am using C++, therefore I would appreciate if anyone could share relevant materials which I could use and preferrably for the 2D case so it is not unnecessarily complicated.

 

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