Blog posts

We develop and demonstrate the first general computational tool for finite deformation static and dynamic dislocation mechanics. A finite element formulation of finite deformation (Mesoscale) Field Dislocation Mechanics theory is presented. The model is a minimal enhancement of classical crystal/J_2 plasticity that fundamentally accounts for polar/excess dislocations at the mesoscale. It has the ability to compute the static and dynamic finite deformation stress fields of arbitrary (evolving) dislocation distributions in finite bodies of arbitrary shape and elastic anisotropy under general boundary conditions. This capability is used to present a comparison of the static stress fields, at finite and small deformations, for screw and edge dislocations, revealing heretofore unexpected differences. The computational framework is verified against the sharply contrasting predictions of geometrically linear and nonlinear theories for the stress field of a spatially homogeneous dislocation distribution in the body, as well as against other exact results of the theory. Verification tests of the time-dependent numerics are also presented. Size effects in crystal and isotropic versions of the theory are shown to be a natural consequence of the model and are validated against available experimental data. With inertial effects incorporated, the development of an (asymmetric) propagating Mach cone is demonstrated in the finite deformation theory when a dislocation moves at speeds greater than the linear elastic shear wave speed of the material.

Paper can be found at link Finite_Deformation_Dislocation_Mechanics.

Laboratory of Ocular Biomechanics, University of Pittsburgh.
We are looking for a highly motivated postdoc to join our team to work on Digital image correlation and Virtual fields modeling. Candidates must have experience in these techniques. Experience analyzing images from optical coherence tomography or microscopy will be an advantage. Experience in ophthalmology or vision science is not required. A solid publication record and evidence of strong writing and presentation skills is required.

Laboratory of Ocular Biomechanics, University of Pittsburgh.

We are looking for a highly motivated postdoc to join our team to study the mechanics of fibrous materials. Candidates must have expertise in the mechanics of materials with long fibers, such as fabrics and textiles, or of soft tissues, such as tendon or heart valves. Experience in multi-scale methods is advantageous. The project has experimental and computational elements, and therefore candidates with experience and/or interests in either will have equal opportunity to be selected. Experience with biological samples or soft tissues is preferred but not required. Similarly, experience in ophthalmology or vision sciences is not required. A solid publication record and evidence of strong writing and presentation skills will be an advantage.

The Design & Uncertainty Quantification group at The University of Iowa, led by Professor Sharif Rahman, is looking for new Ph.D. students, who are capable of and interested in performing high-quality research on uncertainty quantification and stochastic design optimization. The research, supported by U.S. National Science Foundation, requires building a solid mathematical foundation, devising efficient numerical algorithms, and developing practical computational tools, all associated with stochastic analysis and design of complex materials and structures.

I am seeking enthusiastic students and recent graduates to join my group at the University of Missouri - Columbia to work on the nonlinear structural mechanics of folded and 3D printed materials such as origami tessellations and lattices. Positions are available at the level of Graduate Research Assistants and Postdoctoral Fellows. Candidates with background in nonlinear finite element analysis are particularly encouraged to apply.

The Department of Engineering at Aarhus University has a number of open positions as Assistant Professor (tenure track) or Associate Professor at the Section of Mechanical Engineering. The University seeks innovative and visionary engineers/researchers capable of developing the research in Mechanical Engineering.

The positions are available from January 1, 2020 or as soon as possible hereafter.

Research focus

A very interesting recent paper by Dalvi et al. has demonstrated convincingly with adhesion experiments of a soft material with a hard rough material that the simple energy idea of Persson and Tosatti works reasonably well, namely the reduction in apparent work of adhesion is equal to the energy required to achieve conformal contact. We demonstrate here that, in terms of a stickiness criterion, this is extremely close to a criterion we derive from BAM (Bearing Area Model) of Ciavarella, and not very far from that of Violano et al.