research

Robert Lipton's picture

Dynamic Brittle Fracture as a Small Horizon Limit of Peridynamics

Overview: The peridynamic formulation is a
spatially nonlocal derivative free model for simulating problems of free crack
propagation.Material points interact through short-range forces and the
formulation allows for discontinuous deformations. Here the short-range forces
are initially elastic and soften beyond a critical relative displacement. We
upscale this peridynamic model to find the macroscopic (a.k.a. small horizon)
limit. It is shown that the limiting macroscopic evolution has bounded energy
given by the bulk and surface energies of brittle fracture mechanics. The
macroscopic evolution corresponds to the simultaneous evolution
of the fracture surface and linear elastic displacement away from the crack


Curvature effect on nitinol aortic stent

high i am a student doing a project on curvature effect on thoracic stent. I want to curve the nitinol stent in abaqus. I am using RSURFU and doing static analysis. But am not able to curve it. Also when using implicit dynamic analysis with quasi static apllication my KE is high and comparable to IE. So can any body help me. Crimping and expansion is not a problem.

 


J integrale evalution on Abaqus

Good mourning, i am using Abaqus software to inverstigate a crack propagation problem using Abaqus, in this regards i have created a seam crack iner the geometrie which is a plate  under a plane stress condition, my problem is how to mesh around the crack tip in order to have a regular mesh around the crack tip so i can evaluate J integral for multiple contours, the Abaqus documentation mention the swept meshing technique but i coudn't find something about a 2D problem since the sweapt meshing technique nead to mesh a section and swept it over the rest of the body, and in 2d problem we have eages, so how to use it 'some basics rules' in order to creat a regular mesh around the crack tip, i am waiting for any answer from you guys, thank you


ABAQUS Post processing

I have modeled a pile which was made to penetrate at a constant rate (Displacement controlled loading) into the soil. The steps were divided into geostatic, contact and Applied load steps. After the program runs successfully, i am facing difficulty in extracting the results.

 I want to plot the load vs. displacement curve at the bottom of the pile.  After i have summed up all the nodal forces at the bottom of the pile, the total load was coming quite less as compared to the applied Load/Displacement.

Kindly suggest me, how to compute the Load vs.  Displacement curve from displacement controlled loading at pile base.

 

Thanking you,

Tanmoy Kr. Deb


ABAQUS Analysis

How to differentiate between the analysis of a "hollow pile with closed top and an open end" with "vented top and open ended pile".

 

After applying compressive load at both the pile tops (closed and vented), i have obtained/observed that the vented pile is offering higher resistance to penetration as compared to closed top pile.

 

 The sequence of steps i have followed are Geostatic, Contact and Compressive loading respectively. How to Model/Analyze the hollow pile with vented top so that it offers lesser resistance as compared to hollow pile with Closed top.

 


Ansys Mechanical: Anisotropic Hyperelasticity Material Model

I am currently researching the
fluid-structure interaction (FSI) of fistula and av-grafts in the region
of the brachial artery in dialysis patients. I will be using ANSYS
Mechanical and FLUENT as the coupling offered is strong/implicit which
is necessary for my model. I'm having some trouble implementing the
anisotropic hyperelastic material model for the artery. This material is
in the 'Special Hyperelastic Materials' section and thus needs to be
inputed through command snippets. I get a solution, but it is not behaving as it should because my command snippet material is being ignored..

My issues are the following:


Stochastic modeling of damage evolution in composites under environmental ageing

Stochastic modeling of damage evolution in composites under environmental ageing

R. Rahman, A. Haque, Z. Wu

Journal of Engineering Mathematics

April 2013, Volume 79, Issue 1, pp 153-166

Abstract


Daniel Kiener's picture

Detwinning in full view: Twins, seen as dark areas in the left image, disappear upon tensile loading (right image).

Detwinning in full view: Twins, seen as dark areas in the left image, disappear upon tensile loading (right image).

Reversible cyclic deformation mechanism of gold nanowires by twinning–detwinning transition evidenced from in situ TEM

http://www.nature.com/ncomms/2014/140108/ncomms4033/full/ncomms4033.html


Micromechanics of Composites

Hi,

Can somebody suggest me a good book for micromechanical modeling of composites?

Thanks 


Abrasive Simulation

Hi,

I'm trying to do simulation on Abrasive sand paper. I want to calculate the amount of material removed from the workpiece after some  number cycles.

 Can any one help me how can I start this simulation in abaqus.

 Regards,

Satish 


ABQ Python Scripting to create mesh definition without geometry

Dear iMecanica community,

with ABQ I'd like to create a mesh part without an associated geometry using the bottom-up-technique.

I already found the Python commands to add nodes to an orphaned mesh (from an inp-file).

In order to this I must first import an existing part and make node definitions on the orphan mesh part.

Is there a way in ABQ to define nodes, elements, etc. directly using scripting commands without

creating an orphan mesh part (by importing a model)?

I would be glad for any help, thank you very much in advance!

Greetings,

jo-heintz


ICE's Engineering and Computational Mechanics general call for papers!

Dear Colleague,

Engineering and Computational Mechanics is currently looking for papers on the theme of Disaster and Hazard engineering for publication in 2014. Sub-topics include risk analysis and pre-emptive disasters.

Other themes EACM is interested in are: Fluid Structure interaction especially ringing phenomenon; Energy and renewable energy including offshore and waves; and review papers covering the themes in the call for papers.

If you are interested in submitting a paper, please see the call for papers via the link below:

http://www.icevirtuallibrary.com/upload/EACMGeneralCFP.pdf

If you have any questions, please do not hesitate to contact me.


AndreaBergamini's picture

Phononic crystal with adaptive connectivity: A new approach to 'smart' materials

In recent times, mechanical metamaterials and a phononic crystals have attracted the attention of some groups, as they allow to exploit on a larger scale phenomena known from solid state physics, such as the creation of band gaps at certain frequencies. The peculiarity of metamaterials is that their effective properties emerge from the periodic geometric organization of their unit cells rather than from the constituting bulk materials. Furthermore, metamaterials can be built in any size, ranging from the nanometer to the meter scale, and out of any material to suit different needs.


Konstantin Volokh's picture

Navier-Stokes model with viscous strength

In the laminar mode interactions
among molecules generate friction between layers of water that slide with
respect to each other. This friction triggers the shear stress, which is
traditionally presumed to be linearly proportional to the velocity gradient.
The proportionality coefficient characterizes the viscosity of water. Remarkably,
the standard Navier-Stokes model surmises that materials never fail – the transition
to turbulence can only be triggered by some kinematic instability of the flow. This
premise is probably the reason why the Navier-Stokes theory fails to explain


Payam Soltani's picture

Effect of geometric parameters on the stress distribution in Al 2024-T3 single-lap bolted joints- Outstanding Paper Award Winner

 The article entitled “Effect of geometric parameters on the stress distribution in Al 2024-T3 single-lap bolted joints” published in International Journal of Structural Integrity 


nanomechanics

nanomechanics


Amir Abdollahi's picture

Three-dimensional simulation of crack propagation in ferroelectric polycrystals: Effect of combined toughening mechanisms

We simulate the fracture processes of ferroelectric polycrystals in
three dimensions using a phase-field model. In this model, the grain
boundaries, cracks and ferroelectric domain walls are represented in a
diffuse way by three phase-fields. We thereby avoid the difficulty of
tracking the interfaces in three dimensions. The resulting model can
capture complex interactions between the crack and the polycrystalline
and ferroelectric domain  microstructures. The simulation results show
the effect of the microstructures on the fracture response of the
material. Crack deflection, crack bridging, crack branching and
ferroelastic domain switching are observed to act as the main fracture
toughening mechanisms in ferroelectric polycrystals. Our fully 3-D


beenchang's picture

Instability of supersonic crack in graphene

The velocity and instability of crack motion in 2D hexagonal lattice of graphene under pure opening loads
are investigated by atomistic molecular dynamics simulations. The brittle crack along zigzag direction
in a strip can propagate supersonically at even 8.82 km/s under uniform normal loading of edge
displacements. Crack moving straightly at low speeds produces atomically smooth edges, while kinking
occur beyond a critical speed around 8.20 km/s equivalent to 65% of Rayleigh-wave speed in graphene,
which validates previous theoretical predictions of rapid fracture instability in elastodynamics, and
rough and irregular edges with oscillatory overhangs are formed subsequently.


Pawel Woelke's picture

George Z. Voyiadjis inducted into the Polish Academy of Sciences (pictured with Michal Kleiber - September 2013)

George Z. Voyiadjis inducted into the Polish Academy of Sciences (pictured with Michal Kleiber - September 2013)

Please join me in congratulating George Z. Voyiadjis, chair of LSU Department of Civil and Environmental Engineering, on his induction into the Polish Academy of Sciences.


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