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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.

Elastic-plastic analysis by 4 nodes isoparametric finite element. Theory Mises

 The relationship between the strains and stresses will be considered based on the premise that for every increment of load deformation occurs, consisting of two parts - the elastic and plastic

 The program of calculation by finite element method

http://www.studinfo.esy.es/pl.pdf

Lazuardi Pujilaksono's picture

Fatigue crack propagation

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Hi, I'm trying to perform a supposedly-simple experiment on fatigue crack propagation of UHMWPE. I use a compact-tension specimen on a servopulser hidraulic testing machine. I will try to do the experiment on a fix Pmax with a varied force ratio (R) from 0.1 to 0.5. I'm having trouble in deciding the maximum force Pmax. How does one decide the amount of force applied for FCP testing? Calculation steps and so on.

Arash_Yavari's picture

Compatible-Strain Mixed Finite Element Methods for 2D Compressible Nonlinear Elasticity

In this paper, using the Hilbert complexes of nonlinear elasticity, the approximation theory for Hilbert complexes, and the finite element exterior calculus, we introduce a new class of mixed finite element methods for 2D nonlinear elasticity -- compatible-strain mixed finite element methods (CSFEM). We consider a Hu-Washizu-type mixed formulation and choose the displacement, the displacement gradient, and the first Piola-Kirchhoff stress tensor as independent unknowns. We use the underlying spaces of the Hilbert complexes as the solution and test spaces.

How to know the element number within an hetval subroutine

Hi everybody

I'm a new user of abaqus and I'm trying to describe the heat generation in a changing phase thermoset polymer using abaqus user subroutine HETVAL. I need for my computations the current element number (in such a way that I can find the adjacent elements in the connectivity matrix).

Does anyone have any suggestion?

Thank you

Amir Nasirmanesh's picture

Eigenvalue buckling analysis of cracked functionally graded cylindrical shells in the framework of the extended finite element method

Hi everybody

My new paper on the buckling behavior of cracked FGM shells has been published in the Composite Structures.

I would be very happy to answer any further question.

I attached the pdf file of the paper to this blog.

kshitij_gaikar's picture

Simulation of moving wheel on the rail?

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Hi Guys,

mohamedlamine's picture

Publication

Hi all,

I am pleased to post the references of my recent paper entitled :

"CONTRIBUTION TO BRIDGE DAMAGE ANALYSIS" Mohammed Lamine MOUSSAOUI, Abderrahmane KIBBOUA, Mohamed CHABAAT

APPLIED MECHANICS AND MATERIALS Journal,

Volume 704 (2015) pp 435-441

DOI: 10.4028/www.scientific.net/AMM.704.435

 

N.B: The equation (7) has been reviewed with:

[P2](nxg)=[[I](nxn)| [0](nxf)]

and is available at:

Does internal heat transfer attribute work with VUMAT subroutine?

I am running J-C plasticity VUMAT subroutine and trying to club inbuilt heat transfer attributes for temperature update, but it's not working. I would appreciate if someone can advise me if there any way to club inbuilt heat transfer with VUMAT or I have to write separate subroutine? 

Thanks & Regards,

Abhishek

Jinxiong Zhou's picture

Soft mobile robots driven by foldable dielectric elastomer actuators

A cantilever beam with elastic hinge pulled antagonistically by two dielectric elastomer (DE) membranes in tension forms a foldable actuator if one DE membrane is subject to a voltage and releases part of tension. Simply placing parallel rigid bars on the prestressed DE membranes results in enhanced actuators working in pure shear state. We report design, analysis, fabrication and experiment of soft mobile robots that are moved by such foldable DE actuators.

Post-Doc position within the International Research Training Group "Integrated Engineering of continuous-discontinuous long fiber reinforced polymer structures” (DFG GRK 2078)

The international research training group "Integrated Engineering of continuous-discontinuous long fiber reinforced polymer structures” offers one post-doc position at Karlsruhe Institute of Technology (KIT). Discontinuous long fiber reinforced polymer structures with local continuous fiber reinforcements represent an important class of lightweight materials. This class of materials has a significant potential for energy savings due to the high specific stiffness and strength as well as the variety of design options in diverse technical applications, e.g., in vehicle construction.

Payam Soltani's picture

Tuning of a piezoelectric vibration absorber attached to a damped structure

Tuning of a piezoelectric vibration absorber attached to a damped structure

By : Payam Soltani, Gaetan Kerschen, Gilles Tondreau, Arnaud Deraemaeker

Abstract:

tarkes's picture

Defining perioidc BC for 1 element elastic model for Biaxial pull in ABAQUS

For simplicity in understanding Perioidic BC in ABAQUS, I am trying to implement in a single element elastic model.

Material is elastic. There are two reference points defined Refpoint 1 for x-direction pull and Refpoint 2 for y-direction pull. Please find the attached picture for clarity in the model.

 

I have defined the equations for PBC in ABAQUS as below:

 

x1-x2+Refpoint1=0

y1-y2+Refpoint1=0

 

x3-x4+Refpoint1=0

y3-y4+Refpoint1=0

 

x2-x3+Refpoint2=0

y2-y3+Refpoint2=0

 

Congrui Jin's picture

Elastic Microplane Formulation for Transversely Isotropic Materials

Our recent work investigates the extension of the microplane formulation to the description of transversely isotropic materials such as shale rock, foams, unidirectional composites, and ceramics. Two possible approaches are considered: 1) the spectral decomposition of the stiffness tensor to define the microplane constitutive laws in terms of energetically orthogonal eigenstrains and eigenstresses; and 2) the definition of orientation-dependent microplane elastic moduli.

Microstructure modeling of random composites with cylindrical inclusions having high volume fraction and broad aspect ratio distribution

We proposed a computational methodology for generating microstructure models of random composites with cylindrical or sphero-cylindrical inclusions having high volume fraction and broad aspect ratio distribution. The proposed methodology couples the random sequential adsorption (RSA) algorithm and dynamic finite element (FE) simulations. It uses RSA to generate sparse inclusion assemblies of low volume fraction and subsequently utilizes dynamic FE simulation for inclusion packing to achieve high volume fractions.

shreeram111's picture

Crack tip mesh size - Interface cracks ?

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Hello everybody,

                   I am working on FE Simulation of interface cracks. To this end, I use modified VCCT, CSDEM and other such methods to determine mesh independent strain energy release rate (G) and Mode mixity (ψ). Now I have a fundamental doubt.

Kmomeni's picture

Special issue on "Low-Dimensional Phase Transforming Materials"

A special issue of Journal of Nanomaterials is devoted to "Low-Dimensional Phase Transforming Materials" which obtained significant interests in the recent years. This topic covers a broad range of research such as 

Implicit vs explicit result in damage-mechanics+plasticity model

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Hello experts, I am trying to model the response (damage+plasticity) and compare with commercial FE codes. I chose to follow explicit scheme and compare with available implicit solution. Attached image shows the comparison between implicit (commerical FE software) and explicit (my Python program).

 As it can be observed, near the failure, i.e. applied strain > 0.05, there is a noise in the explicit solution. When I decrease the time step, the noise infact decreases.

(a) Is this noise is a result of explicit procedure ? or some thing wrong with my algorithm ?

Approaching the ideal elastic strain limit in silicon nanowires

In our new paper published on Science Advances, we carefully measured the elastic mechanical properties of individual silicon nanowires by uniaxial tensile straining under both SEM and high-res optical microscope, and demonstrated that high quality VLS–grown single-crystalline Si nanowires with diameters of ~100 nm can be reversibly stretched at room temperature with 10% or more elastic strain, approaching the theoretical limit of silicon. 

hiasala's picture

UEL for Multiphase flow in Abaqus

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Hi Everyone,

Has anyone been able to successfully code a UEL for modelling multiphase flow in rocks in abaqus, I have seen some work by Björn Schümann and checked out some of his references (Holler, 2006) but i have been unable to get this to work. Any ideas or can anyone point me in the right direction ?

 

Thanks

 

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.

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.

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