Modeling bending response of shape memory alloy wires/beams under superelastic conditions - A two species thermodynamic Preisach approach

Ashwin Rao — 2013-06-10

In this paper, a model to capture the pure bending response of shape memory alloys (SMA) beams/wires under superelastic conditions is constructed by combining thermodynamics principles along with preisach models. The model is formulated directly using experimentally measurable quantities “Bending Moment and Curvature” rather than evaluating the same from stress resultants by integration as commonly followed in literature. Following Doraiswamy et al. (2011), the key idea here is in separating the elastic and the dissipative part of the hysteritic response with a Gibbs potential based formulation and thermodynamic principles. The preisach model is then employed in capturing the dissipative part of the entire thermoelastic response. Such an approach can simultaneously include both thermal and mechanical loading in the same framework and

one can easily simulate complex temperature dependent superleastic responses. The model results are compared with experiments performed on SMA wires/beams at di erent

temperatures as reported in the literature for NiTi and CuZnAl material systems.

Numerical Solution of Many-body Wave Scattering Problem and Creating Materials with A Desired Refraction Coefficient

Nhan Thanh Tran — 2013-12-31

Wave scattering by many small particles with impedance boundary condition and creating material with a desired refraction coefficient are studied. The acoustic wave scattering problem is solved asymptotically and numerically under the assumptions $ka \ll 1, \zeta_m = \frac{h(x_m)}{a^\kappa}, d = O(a^{\frac{2-\kappa}{3}}), M = O(\frac{1}{a^{2-\kappa}}), \kappa \in (0,1)$, where $k = 2\pi/\lambda$ is the wave number, $a$ is the radius of the particles, $d$ is the distance between neighboring particles, $M$ is the total number of the particles embedded in a bounded domain $D \subset \RRR$, $\zeta_m$ is the boundary impedance of the m\textsuperscript{th} particle, $h \in C(D)$ is a given arbitrary function which satisfies Im$h \le 0$, $x_m \in D$ is the position of the m\textsuperscript{th} particle, and $1 \leq m \leq M$. Numerical results are presented for which the number of particles equals $10^4, 10^5$, and $10^6$.

The International Journal of Structural Changes in Solids

Modeling bending response of shape memory alloy wires/beams under superelastic conditions - A two species thermodynamic Preisach approach

Numerical Solution of Many-body Wave Scattering Problem and Creating Materials with A Desired Refraction Coefficient