research

Transverse wrinkles usually occur in a uniaxially tensile elastic membrane and will be smoothed upon excess stretching. This instability-restabilization response (isola-center bifurcation) can originate from the nonlinear competition between stretching energy and bending energy. Here, we find a crucial factor, the curvature, which can control effectively and precisely the wrinkling and smoothing regimes. When the sheet is bent, the regime of wrinkling amplitude versus membrane elongation is narrowed, with local wrinkling instability coupled with global bending.

Directional solidification of Al-11 at % Cu is investigated by molecular dynamics (MD) simulations utilizing second nearest neighbor modified embedded atom method (2NN-MEAM) interatomic potential. The condition for directional solidification is produced by imposing dissimilar temperatures at the model boundaries along the [1 0 0] solidification direction to create a temperature gradient. During solidification, the solid-liquid front travels through the Al-Cu liquid along the [1 0 0] direction towards the high temperature end.

A criterion for the mean stress effect correction in the shift factor approach for variable amplitude life prediction is presented for both smooth and notched specimens. The criterion is applied to the simple idea proposed by the authors in a previous note that Gaßner curves can be interpreted as shifted Wöhler curves. The mean stress correction used has been proposed by Smith, Watson and Topper and, more in general, by Walker.

Tensional wrinkles are widely observed in elastic thin films, with mono-orientation of wrinkles being usually perpendicular to the stretching direction. Here, by changing material orthotropic direction, we present orientable wrinkles in uniaxially stretched orthotropic membranes. To quantitatively explore orthotropy-related wrinkles and their morphological evolution, we develop a mathematical model by introducing orthotropic, elastic constitution into the extended F\"oppl-von K\'arm\'an nonlinear plate theory that can describe large in-plane anisotropic deformations.

https://doi.org/10.1016/j.compscitech.2019.107832

Link to author's personalized share link for free access until November 19 2019: https://authors.elsevier.com/a/1ZpgjyZzKoGVz

Abstract:

A postdoc in the area of flexible skin for morphing wings is available at Khalifa University, UAE. 

This is the preprint of an article that will appear in Computational Materials Science (doi.org/10.1016/j.commatsci.2019.109217)

A 3D phase field dislocation dynamics model for body-centered cubic crystals

Xiaoyao Peng (Carnegie Mellon University), Nithin Mathew (Los Alamos National Laboratory), Irene J. Beyerlein (University of California, Santa Barbara), Kaushik Dayal (Carnegie Mellon University), Abigail Hunter (Los Alamos National Laboratory)

Abstract

We report a manufacturing technology, called conformal additive stamp (CAS) printing and show that it can be used to reliably manufacture electronic devices with 3D shapes. Our CAS printing approach employs a pneumatically inflated elastomeric balloon as a conformal stamping medium to pick up pre-fabricated electronic devices and print them onto 3D surfaces to create devices with curvy shapes including electrically small antennas, hemispherical solar cells and smart contact lenses.