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The focus of this paper is the study and thermomechanical characterization of High Temperature Shape Memory Alloys (HTSMAs) at different stress levels and temperatures ranging from 300 to 500°C. The stability of the material response under cyclic actuation is also investigated. The observations deduced from the tests are presented in detail. In order to investigate the above issues a Ti 50 Pd 40 Ni 10 HTSMA was used. The alloy was fabricated by a vacuum arc melting technique, followed by casting and hot rolling. A high temperature experimental setup was developed on a load frame to test the material at high temperatures under constrained actuation conditions. Certain key observations on the material response, in terms of recoverable strains under various applied total strains and actuation stress levels, and cyclic thermomechanical behavior are presented.

An instrument to estimate the dynamic properties of articular cartilage in vivo is proposed. Through the use of a mechanical indenter adapted from in vitro testing methods and an ultrasound data acquisition system, a time constant for articular cartilage can be obtained. Dynamic lumped parameter models of articular cartilage and the instrument were developed using bond graph techniques for evaluating the feasibility of microfabricating the tool. Simulation results showed that a characteristic time constant for cartilage reswelling could be measured using the probe. Measurement protocols were designed to isolate fluid resistance and cartilage stiffness. Scaling the size of the instrument down lowered the amplitude of the forces required to indent the cartilage and reduced the length of the time the surgeon would need to hold the instrument in a single position in order to perform a test.

Numerical calculations of the droplet dispersion in a conical spray burner are presented. A commercial CFD code, FLUENT, is used to execute the numerical calculations. The burner has the shape of a cone, which is offset in four places. These four gaps allow for secondary air injection into the burner region, and provide a high level of swirl. The fuel spray, together with coaxial primary air, in both co-swirl (primary air swirling in the same direction as the secondary air), and counter-swirl configuration are introduced at the base of the burner. Results indicate that the counter-swirl configuration leads to uneven fuel distribution and local pockets of high stoichiometry. Increasing the swirl ratio between the primary and secondary stream enhances the central recirculation region that is likely to promote flame stability, but adversely affects the mixing and fuel distribution. Increasing air to fuel flow momentum ratio leads to low droplet dispersion but higher turbulent level.