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Fracture Mechanics Parameters Calculation

I'm working on Fracture Mechanics of Gravity dams using ANSYS Software.

Chiqun Zhang's picture

Finite element approximation of the fields of bulk and interfacial line defects

Chiqun Zhang            Amit Acharya            Saurabh Puri

A generalized disclination (g.disclination) theory [AF15] has been recently introduced that goes beyond treating standard translational and rotational Volterra defects in a continuously distributed defects approach; it is capable of treating the kinematics and dynamics of terminating lines of elastic strain and rotation discontinuities. In this work, a numerical method is developed to solve for the stress and distortion fields of g.disclination systems. Problems of small and finite deformation theory are considered. The fields of a single disclination, a single dislocation treated as a disclination dipole, a tilt grain boundary, a misfitting grain boundary with disconnections, a through twin boundary, a terminating twin boundary, a through grain boundary, a star disclination/penta-twin, a disclination loop (with twist and wedge segments), and a plate, a lenticular, and a needle inclusion are approximated. It is demonstrated that while the far-field topological identity of a dislocation of appropriate strength and a disclination-dipole plus a slip dislocation comprising a disconnection are the same, the latter microstructure is energetically favorable. This underscores the complementary importance of all of topology, geometry, and energetics in understanding defect mechanics. It is established that finite element approximations of fields of interfacial and bulk line defects can be achieved in a systematic and routine manner, thus contributing to the study of intricate defect microstructures in the scientific understanding and predictive design of materials. Our work also represents one systematic way of studying the interaction of (g.)disclinations and dislocations as topological defects, a subject of considerable subtlety and conceptual importance [Mer79, AMK17].

Feedback-Accelerated Picard Iteration for Orbit Propagation and Lambert’s Problem

This paper presents a new Feedback-Accelerated Picard Iteration method for solving long-term orbit propagation problems and perturbed Lambert’s problems. This method is developed by combining the collocation method and the variational iteration method over large-time-steps. The resulting iterative formulae are explicitly derived so that they can be directly adopted to solve problems in orbital mechanics. Several typical orbit regimes incorporating high-order gravity and air drag force are used to demonstrate the application of the proposed method in orbit propagation.

kolman's picture

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids

 

September 17-21 2018

 

Institute of Thermomechanics, The Czech Academy of Sciences, Prague, Czech Republic

 

The 2nd International Conference on Advanced Modelling of Wave Propagation in Solids intends to concentrate on topics such as:

Zhengwei Li's picture

Harnessing Surface Wrinkling-Cracking Patterns for Tunable Optical Transmittance

Optical devices and systems with tunable optical transmittance have recently attracted great interest due to their wide range of applications. However, the reported methods of realizing tunable optical transmittance still suffer from complex fabrication processes, high cost, unstable materials or low tuning range. In this study, we report a simple, cheap, and highly effective approach to achieve large tuning range of optical transmittance through harnessing surface wrinkling-cracking patterns on PDMS films.

Ali Ramazani's picture

Molecular dynamics study of phonon transport in graphyne nanotubes

We determine the thermal conductivities of a, b, and g graphyne nanotubes (GNTs) as well as of carbon
nanotubes (CNTs) using molecular dynamics simulations and the Green-Kubo relationship over the
temperature range 50e400 K. We find that GNTs demonstrate considerably lower thermal conductivity
than CNTs with the same diameter and length. Among a (alpha), b (beta), and g (gama)-GNTs, g-GNT has the highest thermal
conductivity at all temperatures. By comparing the phonon transport properties of GNTs with CNTs, we

Abaqus Python : reading odb file for field frame data

Hi,

I am running a python script to do some post processing on Abaqus odb file. While running it on Abaqus/Explicite output file I found it was taking more than usual time. And after timing the run I got the surprise that the most time consuming thing what just to read the time value for each frame. I have the script below.

def main():

odb=openOdb('F:/Scripting/.../.../Example.odb') 

Journal Club for September 2017: Some recent developments in constitutive modeling of glassy polymers

The physics of glassy materials is a fascinating area of research. On one hand, the statistical mechanics understanding of their behavior is an active and exciting area of research. On the other hand, it is still quite challenging to develop and calibrate predictive constitutive models that reproduce all the observed behaviors. Many of the physical aspects the thermo-mechanics and ageing behavior of glasses are what actually make their constitutive modeling complex.

ryvkin's picture

Postdoc/PhD position in Computational (solid and structural) Mechanics in Tel Aviv University

Recently developed mathematical tools based on the discrete Fourier transform will enable modeling of fracture phenomenon in materials with periodic hierarchical microstructure.

The postdoc position is for one or two years, and PhD is a usual Phd program.  More info on the project is in attached file.

Giorgio Carta's picture

Gyro-elastic beams for the vibration reduction of long flexural systems

The paper presents a model of a chiral multi-structure incorporating gyro-elastic beams. Floquet–Bloch waves in periodic chiral systems are investigated in detail, with the emphasis on localization and the formation of standing waves. It is found that gyricity leads to low-frequency standing modes and generation of stop-bands. A design of an earthquake protection system is offered here, as an interesting application of vibration isolation. Theoretical results are accompanied by numerical simulations in the time-harmonic regime.

Chiqun Zhang's picture

Computational modeling of tactoid dynamics in chromonic liquid crystals

Chiqun Zhang            Amit Acharya            Noel J. Walkington            Oleg D. Lavrentovich

Motivated by recent experiments, the isotropic-nematic phase transition in chromonic liquid crystals is studied. As temperature decreases, nematic nuclei nucleate, grow, and coalesce, giving rise to tactoid microstructures in an isotropic liquid. These tactoids produce topological defects at domain junctions (disclinations in the bulk or point defects on the surface). We simulate such tactoid equilibria and their coarsening dynamics with a model using degree of order, a variable length director, and an interfacial normal as state descriptors. We adopt Ericksen's work and introduce an augmented Oseen-Frank energy, with non-convexity in both interfacial energy and the dependence of the energy on the degree of order. A gradient flow dynamics of this energy does not succeed in reproducing some simple expected feature of tactoid dynamics. Therefore, a strategy is devised based on continuum kinematics and thermodynamics to represent such features. The model is used to predict tactoid nucleation, expansion, and coalescence during the process of phase transition. We reproduce observed behaviors in experiments and perform an experimentally testable parametric study of the effect of bulk elastic and tactoid interfacial energy parameters on the interaction of interfacial and bulk fields in the tactoids.

Meisam. Asgari's picture

Theoretical and experimental constitutive modelling of soft materials at the nano scale: Cylindrical micellar filaments

We present theoretical and experimental descriptions of the elasticity of cylindrical micellar filaments using micro-mechanical and continuum theories, and Atomic Force Microscopy. Following our micro-mechanical elasticity model for micellar filaments [Asgari, Eur. Phys. J. E 2015, 38(9)], the elastic bending energy of hemispherical end caps is found. The continuum description of the elastic bending energy of a cylindrical micellar filament is also derived using constrained Cosserat rod theory.

Ruobing Bai's picture

Localized Deformation in Plastic Liquids on Elastomers

Dear Colleagues,

Attached please find our recent paper “Localized Deformation in Plastic Liquids on Elastomers”.

Title: Localized Deformation in Plastic Liquids on Elastomers

Authors: Xavier P. Morelle, Ruobing Bai and Zhigang Suo

FINITE ELEMENTS IN PLASTICITY: D. R. J. OWEN E. HINTON - Source Code

Choose a channel featured in the header of iMechanica: 

Hello Everyone,

 

Does any one have the source code of this book.

 

FINITE ELEMENTS IN PLASTICITY: Theory and Practice by D. R. J. OWEN & E. HINTON .

 

I need it to understand the plasticity implementation in FEA.

 

Please mail me at ravi.iitroorkee@gmail.com

 

Thanks

Ravi

ahmedettaf's picture

A new hybrid numerical scheme for modeling elastodynamics in unbounded media with near-source heterogeneities

The Finite Difference (FD) and the Spectral Boundary Integral (SBI) methods have been used extensively to model spontaneously propagating shear cracks in a variety of engineering and geophysical applications. In this paper, we propose a new modeling approach, in which these two methods are combined through consistent exchange of boundary tractions and displacements. Benefiting from the flexibility of FD and the efficiency of spectral boundary integral methods, the proposed hybrid scheme will solve a wide range of problems in a computationally efficient way.

Flavio Stochino's picture

Eigenerosion for static and dynamic brittle fracture

In contrast to many numerical methods, the eigenerosion approach yields a convenient description of fracture handled in the postprocessing part of a Finite Element Analysis (FEA). Its fully energetic formulation avoids the introduction of extra degrees of freedom to model fracture propagation. Following previous works on eigenerosion, in this publication, a modified formulation of eigenfracture it is introduced, where it is distinguished between compression and tension loaded state.

Alejandro Ortiz-Bernardin's picture

Veamy: an extensible object-oriented C++ library for the virtual element method

This paper summarizes the development of an object-oriented C++ library for the virtual element method (VEM) named Veamy, whose modular design is focused on its extensibility. The two-dimensional linear elastostatic problem has been chosen as the starting stage for the development of this library. In contrast to the standard finite element method, the VEM in two dimensions uses polygonal finite element meshes.

msaeidi's picture

High thermal conductivity through simultaneously aligned polyethylene lamellae and graphene nanoplatelets

The effect of simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP) on thermal conductivity (k) of PE-GnP composites is investigated. Measurements reveal a large increase of 1100% in k of the aligned PE-GnP composite using 10 weight% GnPs relative to unoriented pure PE. Rate of increase of k with applied strain for the pure PE-GnP composite with 10 wt% GnP is found to be almost a factor of two higher than the pure PE sample, pointing to the beneficial effect of GnP alignment on k enhancement.

Wenbin Yu's picture

Time to Register for 2017 American Society for Composites Annual Conference at Purdue

Dear Colleagues, if you are interested in the state-of-the-art R&D in composite materials, you might want to attend the American Society for Composites Anuual Meeting at Purdue (10/22-25, 2017). The registeration is open at https://cdmhub.org/groups/asc2017/registration

marco.paggi's picture

Identification of higher-order continua equivalent to a Cauchy elastic composite

Dear Mechanician,

A novel method for the identification of higher-order continua equivalent to a Cauchy composite has been published, as a result of the collaboration between the following two ERC projects:

http://erc-instabilities.unitn.it

http://musam.imtlucca.it/CA2PVM.html

Full paper:

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