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Ali Ramazani's picture

Correlation between 2D and 3D flow curve modelling of DP steels using a microstructure-based RVE approach

Since real specimens deform three-dimensionally, 2D modeling approaches cannot predict the flow curve of the material precisely. The predicted flow curves obtained from 2D modeling can, however, be correlated to the 3D ones by introducing a correlation factor, We quantified by the stress ratio (σ3D/σ2D) based on the 2D and 3D RVE calculations for DP600 steels with various martensite phase fractions (Vm=0–50%) at different equivalent plastic strains varying from εpeq=0 to 0.1.

karelmatous's picture

A nonlinear manifold-based reduced order model

A new perspective on model reduction for nonlinear multi-scale analysis of heterogeneous materials. In this work, we seek meaningful low-dimensional structures hidden in high-dimensional multi-scale data.

Rates of bond breaking between myosin and actin at different nucleotide states are systematically extracted for the first time

Recently, unusually high detachment rates of a myosin from actin were reported with a force spectroscopy technique. Here, we show that these high rates may be due to the coupling between bond breaking and state transition. Based on a kinetic model for single myosin, rates of bond breaking between myosin and actin at different nucleotide states are systematically extracted for the first time. Our results clearly indicate that myosins may adopt much higher transition rates than bond breaking rates at different nucleotide states at relatively low forces.

Problem in understanding table in VUHARD

 Hello all,

I am trying to write damage model using isotropic hardening given in Abaqus example. But in VUHARD section some table is given like "syield=table(1, nvalue)" and eqpl1=table(2,k1+1). I dont understand what does it mean and where to put these values? If anyone can explain, it will be a great help.

Thanks 

Abhishek

how can I see subroutine requested output in ABAQUS odb display?

Hello all, 

Can anyone please tell me that how can I see subroutine requested output in ABAQUS odb display? I am able to print some results in .log file but I want to see results in odb display. Is it possible? 

Thanks in advance 
Abhishek

shreeram111's picture

UMAT Non linear Viscoelasticity - Algorithm verification?

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Hello everybody,

           My task is to write a UMAT for Non-linear Viscoelasicity based on Schapery's model in ABAQUS. I have coded the routine, but I am still not able to predict correct response. I tried to debug it as much as I can. I understand that it would be difficult for anybody to understand my code. So, I have attached a flowchart (pdf) of the whole algorithm that I follow. It would be nice if you could check that and correct me if I am wrong.

Thanks in advance for your time and consideration

Regards

Shree

Single Element Test(boundary conditions)

Dear All,

 

I want to do some single element tests for a plane stress quadratic element with bi-linear shape functions(like the plane 42 element in ANSYS).

 

What I am not sure about is what boundary conditions should be applied to the single element in this case. I also want to apply a prescribed displacement as the loading. (I would like to first try to do these single element simulations in Ansys and then with my own developed codes, hopefully the results will conform, as sort of a basic validation of my own developed code)

 

Ali Ramazani's picture

Development and application of a microstructure-based approach to characterize and model failure initiation in DP steels using XFEM

We develop a microstructure-based model to characterize and model failure initiation in DP steels using an extended finite element method (XFEM) to simulate martensite cracking on the mesoscale combined with representative volume element (RVE) modeling. A mini tensile test with digital image correlation (DIC) analysis is linked to local SEM analysis to identify the local strain at which failure is initiated.

chiqun's picture

A non-traditional view on the modeling of nematic disclination dynamics

Chiqun Zhang          Xiaohan Zhang         Amit Acharya          Dmitry Golovaty          Noel Walkington

Nonsingular disclination dynamics in a uniaxial nematic liquid crystal is modeled within a mathematical framework where the kinematics is a direct extension of the classical way of identifying these line defects with singularities of a unit vector field representing the nematic director. It is well known that the universally accepted Oseen-Frank energy is infinite for configurations that contain disclination line defects. We devise a natural augmentation of the Oseen-Frank energy to account for physical situations where, under certain conditions, infinite director gradients have zero associated energy cost, as would be necessary for modeling half-integer strength disclinations within the framework of the director theory. Equilibria and dynamics (in the absence of flow) of line defects are studied within the proposed model. Using appropriate initial/boundary data, the gradient-flow dynamics of this energy leads to non-singular, line defect equilibrium solutions, including those of half-integer strength. However, we demonstrate that the gradient flow dynamics for this energy is not able to adequately describe defect evolution. Motivated by similarity with dislocation dynamics in solids, a novel 2D-model of disclination dynamics in nematics is proposed. The model is based on the extended Oseen-Frank energy and takes into account thermodynamics and the kinematics of conservation of defect topological charge. We validate this model through computations of disclination equilibria, annihilation, repulsion, and splitting. We show that the energy function we devise, suitably interpreted, can serve as well for the modeling of equilibria and dynamics of dislocation line defects in solids making the conclusions of this paper relevant to mechanics of both solids and liquid crystals.

Amit Acharya's picture

A microscopic continuum model for defect dynamics in metallic glasses

Amit Acharya                       Michael Widom

Motivated by results of the topological theory of glasses accounting for geometric frustration,
we develop the simplest possible continuum mechanical model of defect dynamics in metallic
glasses that accounts for topological, energetic, and kinetic ideas. The model is aimed towards
the development of a microscopic understanding of the plasticity of such materials. We discuss
the expected predictive capabilities of the model vis-a-vis some observed physical behaviors of
metallic glasses.

SavanRGowda's picture

Abaqus Fortran Subroutine

Hi Everyone,

I have now managed to run the fortran code, but it won't assign the values that I want to assign to the U(1) variable from the TXT file.

In the attached file I have the Fortran file that I am working on, the input file Subroutine1 (save it as .inp file to open in Abaqus) and the pressure file that contains the nodes and the corresponding pressure values which I want to assign through DISP Subroutine. The code below

      SUBROUTINE DISP(U,KSTEP,KINC,TIME,NODE,NOEL,JDOF,COORDS)

ahmed.hussein's picture

Surface roughness evolution during early stages of mechanical cyclic loading

The effect of crystal size and initial dislocation density on surface roughness evolution in FCC single crystals during the early number of cycles of mechanical cyclic loading is investigated using three dimensional discrete dislocation dynamics simulations. Crystals having size less than 2 μm show early development of surface slip localization, while larger ones show a more uniform distribution of surface steps. The surface roughness is found to increase with increasing number of loading cycles with larger crystals showing a high roughening rate compared to smaller crystals.

Post-doctoral fellow at University of California San Francisco Medical Center and San Francisco VA

The Cardiac Biomechanics Laboratory at the University of California San Francisco Medical Center (UCSF) Division of Cardiothoracic Surgery and San Francisco VA Medical Center is seeking a hard working, motivated post-doctoral fellow to participate in biomedical engineering research involving the ascending thoracic aortic aneurysms (aTAA).  The post-doctoral fellow should be motivated to be on a career track to become an academic professor.  Our lab is NIH funded to investigate the biomechanics of aortic aneurysms and currently has 2 postdoctoral fellows, and are seeking a 3rd.  The goals ar

Shaoxing Qu's picture

Journal Club Theme of March 2016: When mechanics meets medicine in the new age

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Shaoxing Qu

Department of Engineering Mechanics, Zhejiang University, China

Introduction

Applied Mechanics Division – Haythornthwaite Foundation Research Initiation Grants 2016

With funding from the Haythornthwaite Foundation, the Executive Committee (EC) of the Applied Mechanics Division (AMD) of ASME is pleased to announce the establishment of the Haythornthwaite Research Initiation Grant Program, targeting university faculty engaged in research in theoretical and applied mechanics that are at the beginning of their academic careers. Applicants must hold a tenure‐track appointment at the rank of Assistant Professor at a US university on October 1, 2016, and must not be more than 5 years beyond receipt of their doctoral degree at the time the award is made.

jorgegdiaz's picture

SIF analytic Solution (Mode I and/or II) for Tubes

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I was wondering if anyone knows of an analytic Solution for KI and/or KII in tubes.

I´ve seen an infinite number of equations, shape functions, FEM simulations, standards, etc. But one closed solution for tubes?, an analog to Williams series but for cilindirical surfaces?

I am trying to fit experimental displacement data to Williams series. I´ve done it succesfully for flat specimens (kind of easy actually). But now, we have to do the same for tubes. When cracks are long, you can´t approximate the tube surface to an infinite plate anymore.

ahmedettaf's picture

Dynamic friction in sheared fault gouge: implications of acoustic vibration on triggering and slow slip†

Friction and deformation in granular fault gouge are among various dynamic interactions associated with seismic phenomena that have important implications for slip mechanisms on earthquake faults. To this end, we propose a mechanistic model of granular fault gouge subject to acoustic vibrations and shear deformation. The grain-scale dynamics is described by the Shear-Transformation-Zone theory of granular flow, which accounts for irreversible plastic deformation in terms of flow defects whose density is governed by an effective temperature.

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