Journal of Intelligent Material Systems and Structures OnlineFirst, published on May 30, 2007 as doi:10.1177/1045389X07077592 Constitutive Model of Shape Memory Alloys for Asymmetric Quasiplastic Behavior

ABSTRACT: A simple constitutive model of shape memory alloys for analyses of tension–compression quasiplastic behavior is derived. Here, three martensitic variants are considered; namely, thermal-induced, tensile stress-induced, and compressive stress-induced martensitic variants. Reorientation from one variant to another variant is assumed to take place according to a reorientation energy criterion based on grain-based micromechanics. Stress–strain hysteresis loops for a bar under tension–compression cyclic loading are simulated and they are compared with available experimental data. Results show that this constitutive model can capture asymmetric stress–strain behavior for tension and compression and a strain rate effect on stress–strain–temperature relationship quite well

Deformation of a Beam with Partially Debonded Piezoelectric Actuators

A linear and a non-linear mathematical models for analyzing the deformation behavior of a beam with a pair of partially debonded piezoelectric actuators are developed on the basis of the Timoshenko beam theory. Effect of buckling is considered in the linear model, where the debonded actuator region is assumed to generate the Euler buckling load when the axial force in the region is larger than the load. The static behavior of the beam is investigated for extension and bending deformation. When the actuator debonds from its edge, the performance deteriorates; in contrast, the debonding in the middle of the actuator does not show any performance degradation until the debonded region buckles. The deformation behavior obtained from the linear model has been found to have good agreement with that from the non-linear model. The non-linear analysis shows that after the buckling the debonded actuator region maintains an axial force of the order of the Euler buckling load of a fix�fix column for the extending actuation, although for the bending actuation, it retains nearly 75% of the Euler buckling load. Further, the strain distribution in the debonded region shows that the buckling may occur before cracks begin in the actuator