research

Elastomers and gels can often deform multiple times their original length. The stretchability is insensitive to small cuts in the samples, but reduces markedly when the cuts are large. This work shows that this transition occurs when the depth of cut exceeds a material-specific length, defined by the ratio of the fracture energy measured in the large-cut limit and the work to rupture measured in the small-cut limit.  This conclusion generalizes a result in the fracture mechanics of hard materials.

http://dx.doi.org/10.1016/j.actamat.2016.10.005

Abstract

Real-time error controlled adaptive mesh refinement in surgical simulation: Application to needle insertion
Link to paper: http://hdl.handle.net/10993/28624

New paper submitted to IJNMBE on the use of a posteriori error indicators for real time mesh adaptation during surgical simulation.

Stéphane Bordas

Permalink: http://legato-team.eu/real-time-erro…edle-insertion

Abstract

This paper presents a design methodology based on a combination of isogeometric analysis (IGA),

level set and point wise density mapping techniques for topology optimization of piezoelectric /

flexoelectric materials. The fourth order partial differential equations (PDEs) of flexoelectricity,

which require at least C 1 continuous approximations, are discretized using Non-Uniform Rational

B-spline (NURBS). The point wise density mapping technique with consistent derivatives is

Soft elastic layers with top and bottom surfaces adhered to rigid bodies are abundant in biological organisms and engineering applications. As the rigid bodies are pulled apart, the stressed layer can exhibit various modes of mechanical instabilities. In cases where the layer’s thickness is much smaller than its length and width, the dominant modes that have been studied are the cavitation, interfacial and fingering instabilities. Here we report a new mode of instability which emerges if the thickness of the constrained elastic layer is comparable to or smaller than its width.

The size- and shape-dependency of the chemo-mechanical behavior of spherical and ellipsoidal nanoparticles in Li-ion battery electrodes are investigated by a stress-assisted diffusion model and 3D finite element simulations. The model features surface tension, a direct coupling between diffusion and elasticity, concentration-dependent diffusivity, and a Butler-Volmer relation for the description of electrochemical reactions that is modified to account for mechanical effects.

Abstract

A finite element software computes the stresses and/or strains sets values at each dynamic iteration step. These values can be plotted on a stress-space giving several failure envelopes. For an isotropic or an homogeneous mixture the Von Mises criterion represents an ideal envelope which may not coincide with the available envelopes but the stresses values can be checked with the material strength.