research

Stress analysis of composite cylindrical shells with an elliptical cutout  

Erkan Oterkus & Erdogan Madenci & Michael P. Nemeth

This paper presents an anharmonic lattice statics analysis of 180 and 90 domain walls in tetragonal ferroelectric perovskites. We present all the calculations and numerical examples for the technologically important ferroelectric material PbTiO3. We use shell potentials that are fitted to quantum mechanics calculations. Our formulation places no restrictions on the range of the interactions. This formulation of lattice statics is inhomogeneous and accounts for the variation of the force constants near defects.

The simple extension tear test-piece also referred to as the trousers sample is widely used to study crack propagation in rubber. The corresponding energy release rate, called tearing energy for rubber materials, was first established by Rivlin and Thomas (Rupture of rubber. I. Characteristic energy for tearing. J. Polym. Sci., 10:291–318, 1953); a second derivation was proposed later by Eshelby (The calculation of energy release rates. In G. C. Sih, H. C. van Elst, and D. Broek, editors, Prospects of Fracture Mechanics, 69–84, Leyden, Noordhoff, 1975).

All metallic, hollow sandwich cylinders having ultralight two-dimensional prismatic cores are optimally designed for maximum thermo-mechanical performance at minimum mass. The heated cylinder is subjected to uniform internal pressure and actively cooled by forced air convection. The use of two different core topologies is exploited: square- and triangular-celled cores. The minimum mass design model is so defined that three failure modes are prevented: facesheet yielding, core member yielding, and core member buckling.

Dr. Jun Lou and Dr. Junlan Wang are co-editing a special issue on Nanomechanics and Nanostructured Multifunctional Materials: Experiments, Theories, and Simulations for Journal of Nanomaterials, an open access journal. Papers on latest developments on all aspects of nanomechanics and nanostructured materials are welcome. Deadline for manuscript submission is September 01, 2007.

 

For more details, please check JNM website

Apply for NSF fellowships to attend 1-week long workshop on cell mechanics, July 31-Aug 3, 2007.

Check out www.ccm.uiuc.edu  

Depolarization field and misfit strain are two important factors that may greatly influence the properties of ferroelectric thin films. The effect of depolarization field on polarization states of single-domain ferroelectric thin films with nonequally biaxial in-plane misfit strains are studied in the present work by numerically solving three coupled Euler-Lagrange equations, which are derived from the minimization of total free energy.