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mohsenzaeem's picture

Competing mechanisms between dislocation and phase transformation in plastic deformation of single crystalline yttria-stabilized tetragonal zirconia nanopillars

Molecular dynamics (MD) is employed to investigate the plastic deformation mechanisms of single crystalline yttria-stabilized tetragonal zirconia (YSTZ) nanopillars under uniaxial compression. Simulation results show that the nanoscale plastic deformation of YSTZ is strongly dependent on the crystallographic orientation of zirconia nanopillars. For the first time, the experimental explored tetragonal to monoclinic phase transformation is reproduced by MD simulations in some particular loading directions.

Journal Club for September 2016: Developments and challenges in miniaturized in situ experiments – Towards small-scale fracture mechanics

Small-scale mechanics, especially in situ in electron microscopes, is what I enjoy spending my time with. Within this monthly journal club topic on iMechanica, I would like to give a quick recapitulation of what happened in micromechanics, of course with special emphasis to in situ techniques, over the last years to set the stage. Subsequently, we should revisit some longstanding issues before turning towards recent developments in the field of fracture testing.

likask's picture

Solver for h-div and h-curl space

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Hello, 

MoFEM can solve div and curl problems. We have abrbitrary polynomial order on tets/triangles and edges for L2 H1 HCURL and HDIV spaces. You can use Gauss-Lobatto or Legrenge base. It is a great solution for developing magneto-mechanical problems and couple problems in general. MoFEM is open and free code C++ code.  We need help with preconditioner, see below.

Postdoctoral Associate

            The University of Notre Dame, Center for Shock Wave-processing of Advanced Reactive Materials (C-SWARM), is seeking a highly qualified candidate for the postdoctoral associate position in the area of computational mechanics/physics with emphasis on chemically reactive solids. C-SWARM is center of excellence established by National Nuclear Security Administration (NNSA) whose primary focus is on the emerging field of predictive science.

Narasimham's picture

Prescribing Surface Strains to change Gauss curvature

Prescribing  Surface Strains to change Gauss curvature

To change Gauss curvature K of a surface we need to strain each differential shell element by virtue of Egregium theorem ( K is invariant if strain is zero in isometry mappings).

cemalbasaran's picture

A Nobel Prize worthy paper, unifying Mechanics and Thermodynamics with a mathematical basis

I highly recommend this paper to any mechanician who is familiar with the scientific efforst in the last 150 years to unify mechanics and thermodynamics. Sosnoskiy and Sherbakov and several others from the Russian Academy of Sciences listed in the Acknowledgemnsts have achieved it. Congratulations.

Sosnovskiy, L. Sherbakov, S.,”Mechanothermodynamic Entropy and Analysis of Damage State of Complex Systems”, Entropy, 2016, 18, 268.

cemalbasaran's picture

A Nobel prize worthy paper, unifying Mechanics and Thermodynamics with a Mathematical Basis

I highly recommend this paper to any mechanician who is familiar with the scientific efforst in the last 150 years to unify mechanics and thermodynamics. Sosnoskiy and Sherbakov and several others from the Russian Academy of Sciences listed in the Acknowledgemnsts have achieved it. Congratulations.

Sosnovskiy, L. Sherbakov, S.,”Mechanothermodynamic Entropy and Analysis of Damage State of Complex Systems”, Entropy, 2016, 18, 268.

Plasticity model in Abaqus to capture the continues plastic strain of granular material under triaxial cyclic loading?

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I am working on modelling ballast aggregates under triaxial loading. Confining pressure applied in the intermediate and minor principal direction and cyclic compression load applied in the major principal axis direction. I wanted to capture the continues plastic strain (PS) with cycles (N). My test results show that the PS increase with N up to about 10,000 cycles and the rate of strain slowly diminish for later cycles and almost stay constant after N=100,000. What available model in Abaqus can be used to get this behaviour. I have to run my analysis at least for 10,000 cycles.

A Unification of the Concepts of Variational Iteration, Adomian Decomposition and Picard Iteration method; and a Local Variational Iteration Method

This paper compares the variational iteration method (VIM), the Adomian decomposition method (ADM) and the Picard iteration method (PIM) for solving a system of first order nonlinear ordinary differential equations (ODEs). A unification of the concepts underlying these three methods is attempted by considering a very general iterative algorithm for VIM. It is found that all the three methods can be regarded as special cases of using a very general matrix of Lagrange multipliers in the iterative algorithm of VIM.

chang-tsan.lu's picture

A Comparison of the Elastic Properties of Graphene- and Fullerene-Reinforced Polymer Composites: The Role of Filler Morphology and Size

A recently published paper in mechanical properties of graphene polymer nanocomposites via MD simulations, by Chang-Tsan Lu, Asanka Weerasinghe, Dimitrios Maroudas and Ashwin Ramasubramaniam.

pourmatin's picture

Multiscale real-space quantum-mechanical tight-binding calculations of electronic structure in crystals with defects using perfectly matched layers

<p>We consider the scattering of incident plane-wave electrons from a defect in a crystal modeled by the time-harmonic Schrödinger equation. While the defect potential is localized, the far-field potential is periodic, unlike standard free-space scattering problems. Previous work on the Schrödinger equation has been almost entirely in free-space conditions; a few works on crystals have been in one-dimension. We construct absorbing boundary conditions for this problem using perfectly matched layers in a tight-binding formulation.

Nine papers about fatigue modelling of short fiber composite

Recently, we have published a series of nine papers about modelling fatigue and damage in short fiber composites.  Together, they provide a complete description of modelling of such materials including wavy fiber composites; starting from appropriate homogenization method to component level fatigue simulation. Discussion and feedback on the papers is welcome.

Writing UHYPER for photo-thermal sensitive hydrogels described in the thermodynamic framework?

 Hello

I`d like to write a UHYPER for photo-thermal sensitive hydrogels described in the thermodynamic framework. But the photo-chemical term in the energy equation is 7order greater than the others. The other terms are related to stretch and mixing energy they exist also in the temperature sensitive hydrogels energy equations and their UHYPER is valid.  I have checked all the coefficients, their orders are all correct.

Alejandro Ortiz-Bernardin's picture

A novel impact identification algorithm based on a linear approximation with maximum entropy

Paper Accepted for Publication in Smart Materials and Structures

N. Sanchez, V. Meruane, A. Ortiz-Bernardin, “A novel impact identification algorithm based on a linear approximation with maximum entropy.”

ABSTRACT

Fatigue analysi to get crack initiation life using ABAQUS/CAE

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Dear All,

for LCF analysis to get crack initation life for simple plate with central hole specimen.

I used direct cyclic approach but getting error as o/p "CYCLEINI" is not available for your element type.

with fe-safe fatigue tool i got the crack initiation life but I want to get with Abaqus/CAE only

kindly help me out.

how to obtain the crack initation life using abaqus only.

Thanks in adavance

 

Finite element analysis of beams

In this section, the basic principles of the finite element analysis of beams are considered. Beam given below we will divide into two elements by cutting it at the point A, B, C

 

ABAQUS - Stress Intensity Factor for Single Radial Crack in Thick Walled Cylinder

Hi,

I am trying to analyze the stress intensity factor (SIF) using contour integral of a 2D thick walled cylinder under plane stress with different wall ratios under internal pressure loading only and a single radial crack of varying length in Abaqus.

The wall ratio (inner & outer radius) I am interested in modelling is of ratio 6 (i.e. for inner radius of 1, outer radius is 6).

I have modelled ratios from 1-6 with crack length varying from 0.1-0.9 of the wall thickness. (i.e. for ratio 3, the wall thickness is 2, hence the crack varies from 0.1-0.9 x 2).

ntuecd's picture

Discrete Element Method

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Hallo,

from this month i am going to start my work on Discrete Element Method. I am totally new to this field. Therefore, i am looking for some material which can help me not only to understand the theoretical concept but as well as the programming concept in this field.

 

I will be very thankful if someone have materials related to DEM.

 

Regrads

Braj Bhushan Prasad

Analysis of the adsorption-induced deformation of ordered meso/nanoporous materials

The pore-load modulus of ordered nanoporous materials with surface effects.

Liu, M., Wu, J., Gan, Y., & Chen, C. Q. AIP Adv., 2016, 6(3):813. http://scitation.aip.org/content/aip/journal/adva/6/3/10.1063/1.4945441

A feasibility study of the Master SN curve approach for short fiber reinforced composites

I hope you find our recent work interesting...

A feasibility study of the Master SN curve approach for short fiber reinforced composites

Atul Jain, Wim Van Paepegem, Ignaas Verpoest, Stepan V. Lomov

International Journal of Fatigue; Volume 91, Part 1, October 2016, Pages 264–274

http://www.sciencedirect.com/science/article/pii/S0142112316301591

Highlights

Emilio Martínez Pañeda's picture

Strain gradient plasticity-based modeling of hydrogen environment assisted cracking

I hope some of you may find this work interesting:

Strain gradient plasticity-based modeling of hydrogen environment assisted cracking

Emilio Martínez-Pañeda, Christian F. Niordson, Richard P. Gangloff

Acta Materialia, 117, pp. 321-332

http://www.sciencedirect.com/science/article/pii/S1359645416305183

A pre-print is available at www.empaneda.com

maharshi.kintada's picture

What modifications are to be implemented, if the shear strain of a degenerated shell element is modified with (-2*w/Rxy)?

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I had implemented Degenerated shell element by Ahmad et. al (1970). This element performs very poor in case of geometries like rectangular hyperbolic paraboloidal shells. When I modified the strain vector (only shear strain) with a additional -2*w/Rxy (Sahoo and Chakraborty, J. Strain Analysis (2004)), the solutions are not ok. Can you please suggest me if any other things I should be careful?

UMAT for uniaxial compression (plasticity)test is not converge

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Hello everyone,

I am beginner of UMAT.

I am now modeling the model for uniaxial compression of shape memory alloys based on plasticity model and backward euler method.

My material is in cubic 1*1*1. It seems to be simple problem.

Anyway, I am still not familiar with UMAT and Abaqus.

The problem is I apply load just only in Y-axis and specify the boundary condition as in attached file

I think that it passed the plastic deformation zone and abaqus try to calculate...

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