research

Adhesion is a key factor in many tribological processes, especially wear. We generalize a recent formulation for the indentation of a multilayered material using an efficient integral transform method, to the case of adhesion, using a simple energetic transformation in the JKR regime. Then, we specialize the study for the geometry of the Surface Force Apparatus, which consists of two thin layers on a substrate, where the intermediate layer is softer than the other two. We find the pull-off force under "force control" (i.e.

Formation of solidification defects and their evolution in uniaxial tensile deformation of solidified polycrystalline aluminum (Al) were investigated by molecular dynamics (MD) simulations. First, solidification process was simulated both isothermally and with different quench rates. At the initial stages of nucleation, coherent twin boundaries and/or fivefold twins formed depending on the quench rate or the undercooling temperature. The solidified polycrystalline Al consisted of randomly distributed grains, twin boundaries, and vacancies.

In this paper we formulate the problems of nonlinear and linear elastodynamic transformation cloaking in a geometric framework. In particular, it is noted that a cloaking transformation is neither a spatial nor a referential change of frame (coordinates); a cloaking transformation maps the boundary-value problem of an isotropic and homogeneous elastic body (virtual problem) to that of an anisotropic and inhomogeneous elastic body with a hole surrounded by a cloak that is to be designed (physical problem).

https://doi.org/10.1016/j.matdes.2018.04.022

Highlights

Prashant K. Jha and Robert Lipton

Computer Methods in Applied Mechanics and Engineering, 2019. 

https://doi.org/10.1016/j.cma.2019.03.024

Highlights

1. Well-posedness of a general nonlinear state based peridynamic models.

2. A priori numerical convergence rate for finite difference approximations of state based peridynamic models.

3. Numerical verification of convergence rate for samples with growing cracks.

I hope some of you may find this work interesting. We show, analytically and numerically, that strain gradient plasticity predicts the existence of an inner elastic field adjacent to the crack tip, reminiscent of a dislocation-free zone. The fact that elastic strains dominate plastic strains near the crack tip implies a paradigm-shift with respect to previous crack tip asymptotic studies in plasticity and gradient plasticity, which neglect elastic strains. 

Emilio Martínez-Pañeda, Norman A. Fleck

I would like to share our recent work published in Nature Communications.

Matthew P. O'Donnell, Jonathan P. Stacey, Isaac V. Chenchiah, Alberto Pirrera

Abstract