research

Consider a thin dielectric plate with conducting faces: when will it break if a voltage is applied? If it is rigid it will break once its dielectric strength is overcome by the voltage. But what if it is highly stretchable, like the elastomers used for soft actuators, stretchable electronics, or energy harvesters? The precise answer to that question is not known. 

A new class of time-integrators is presented for strongly nonlinear dynamical systems. These algorithms are far superior to the currently common time integrators in computational efficiency and accuracy. These three algorithms are based on a local variational iteration method applied over a finite interval of time.

Paper Accepted for Publication in International Journal for Numerical Methods in Engineering

Consistent and stable meshfree Galerkin methods using the virtual element decomposition

A. Ortiz-Bernardin, A. Russo, N. Sukumar

Abstract

    The stress concentration induced by fretting fatigue was studied with a simple "Crack Analogue" model (CA) by the MIT group of Suresh in the late 1990's, which was then "improved" by the present author to take into account simply both contact loads and bulk stresses loads, and even the case of finite stress concentration in the so-called "Crack Like Notch Analogue" (CLNA) model.

To appear in Journal of Elasticity

A continuum mechanical theory of fracture without singular fields is proposed. The primary
contribution is the rationalization of the structure of a `law of motion' for crack-tips, essentially
as a kinematical consequence and involving topological characteristics. Questions of compatibility
arising from the kinematics of the model are explored. The thermodynamic driving force
for crack-tip motion in solids of arbitrary constitution is a natural consequence of the model.
The governing equations represent a new class of pattern-forming equations.

Highly porous alumina-zirconia ceramics were produced by adding space-holder materials during freeze casting. To increase the strength of porous ceramics, different amounts of nanoadditives (silicon carbide-SiC, silica-SiO₂, and multi-wall carbon nanotubes-CNTs) were added. Space-holder materials were removed by preheating, and solid samples were produced by sintering. Up to 68% porosity was achieved when 40% space-holder was added to the solid load of slurry. Wall thicknesses between pores were more uniform and thinner when nanoadditives were added.