Thermoelectric Shape Memory Alloy Actuators and the Issue of Thermomechanical Coupling

In this work, we mode1 a thermoelectric shape memory alloy(SMA) actuator as part of a research effort to design high-force, high-frequency SMA actuators. Cyclic phase transformation in a SMA layer is achieved by alternately heating/cooling using the thermoelectric Peltier effect. The thermal and mechanical fields during phase transformation are, in general, highly coupled and the extent of this coupling in the light of different mechanical boundary conditions is examined. The primary parameters of design interest are the frequency response and the evolution of the actuation stress. The analysis resulting from the formulated boundary value problem indicates that thin SMA layers(6 µm thick), under partial transformation, are capable of delivering frequencies of about 30 Hz at peak stresses of about 145 Mpa

Constitutive Modeling of Phase Transformation and Plastic Yield in SMAs: Application to the S3T-RoundRobin

In collaboration with other researchers contributing to the S3T-RoundRobin effort, this work presents analytical results as generated using the model of Hartl and Lagoudas (Hartl and Lagoudas, 2009; Hartl et al., 2009). The model, which is based on continuum thermodynamics and inspired by experimental findings, is briefly summarized. Its calibration to the current experimental results is described and predictions generated by the implemented model are compared to the shared data. Some inaccuracies are observed in the uniaxial responses, though good agreement is demonstrated overall, especially with regard to the non-proportional tension-torsion experiments

An investigation on hybrid interface using on-line monitoring experiment and finite element analyses

In this work, the hybrid interface between metal and thermosetting polymer matrix composite was studied via experimental and numerical investigations. Hybrid laminates, whose constituents are aluminum foil, carbon fabric and epoxy matrix, were manufactured using the vacuum assisted resin transfer molding process. Chromic anodization was used to treat the surfaces of the aluminum foil prior to fabricating the hybrid laminates. The mode-I dominated delamination behavior was studied using the double cantilever beam tests at both room (25oC) and elevated (60oC) temperatures. Distributed strain profiles were measured on both the top and bottom of the specimen using Rayleigh backscattering fiber optics technique. Finite element analysis was performed to assist with the analysis and interpretation of experimental results. Load-displacement and strain profiles measured from experiments were compared with values obtained numerically. Good agreements between the experimental and numerical results were observed.Aerospace Structures & MaterialsAerospace Engineerin