Sharif Digital Repository

In this article, the one-dimensional phenomenological constitutive model originally proposed by Brinson for shape memory alloys is improved to predict asymmetric behavior in tension and compression. We propose an approach that decomposes stress-induced martensite volume fraction into two parts, one in tension and one in compression. Results of numerical examples show reasonable agreement with experimental data. Moreover, we implement the proposed model in a user-defined material subroutine in the nonlinear finite element software ABAQUS/Standard as a two-dimensional Euler-Bernoulli beam element. We simulate several beam problems and a shape memory alloy staple. Regarding the results, the... 

The quasi-static and strain-controlled fatigue characteristics of ZK60 extrusion have been investigated along three different directions: the extrusion direction (ED), the radial direction (RD), and 45° to the extrusion direction (45°). The quasi-static response showed symmetric behavior for the samples tested along RD and 45° whereas the ED samples manifested completely asymmetric behavior. Although the ED samples exhibited longer fatigue lives than the RD and 45° in the high cycle fatigue, the fatigue lives in the low cycle fatigue regime were similar. The texture measurement indicated a sharp basal texture along ED, explaining its asymmetric behavior. Higher tensile mean stress and less... 

Spin-transfer torque magnetic RAMs (STT-MRAMs) are the most promising alternative for static random-access memories in large last-level on-chip caches due to their higher density and near-zero leakage power. However, the reliability of STT-MRAMs is threatened by high probability of read disturbance and write failure. Both read disturbance and write failure, which cause a soft error in the cache cells, have an asymmetric behavior. Read disturbance occurs only in STT-MRAM cells storing '1' value, and write failure error rate in a → 1 transition is much higher than that in a 1 → 0 transition. In this paper, we propose Read/write Error-rate Aware Coding Technique (REACT) to improve the... 

The governing equations of the first-order shear deformation plate theory for FG circular plates are reformulated into those describing the interior and edge-zone problems. Analytical solutions are obtained for axisymmetric and asymmetric behavior of functionally graded circular plates with various clamped and simply-supported boundary conditions under mechanical and thermal loadings. The material properties are graded through the plate thickness according to a power-law distribution of the volume fraction of the constituents. The results, which are in closed form and suitable for design purposes, are verified with known results in the literature. It is shown that there are two... 

Based on the first-order shear deformation plate theory with von Karman non-linearity, the non-linear axisymmetric and asymmetric behavior of functionally graded circular plates under transverse mechanical loading are investigated. Introducing a stress function and a potential function, the governing equations are uncoupled to form equations describing the interior and edge-zone problems of FG plates. This uncoupling is then used to conveniently present an analytical solution for the non-linear asymmetric deformation of an FG circular plate. A perturbation technique, in conjunction with Fourier series method to model the problem asymmetries, is used to obtain the solution for various clamped...