Initial Investigation in Actuator Design Using High Temperature Shape Memory Alloy

摘要

The need for shape memory alloys (SMA) with high transformation temperatures is urgent. SMA actuators may then be designed that will demonstrate two important attributes: (ⅰ) actuation in a high temperature environment and (ⅱ) high actuation frequency in a moderate temperature environment. Copper-Aluminum-Nickel (CuAlNi) single crystal alloy is a promising candidate due to favorable characteristics such as wide range of transformation temperatures, large actuation stress and strain, and lack of plastic deformation under cyclic loading. These characteristics point to the possibility that CuAINi single crystal high temperature SMA (HTSMA) actuators can be developed that will demonstrate the attributes mentioned above. An initial investigation of these possibilities is carried out computationally by analyzing a HTSMA-actuated airfoil. An existing rate-independent thermomechanical model is calibrated to describe the CuAINi material behavior. Time-dependent thermomechanically-coupled parametric studies are carried out to yield information about the airfoil stroke (trailing edge deflection), the actuation energy required and the actuation frequency possible for cyclic actuation, all as a function of transformation temperatures. For comparison purposes, a similar parametric study is also carried out for NiTi polycrystalline SMA. The analysis indicates that a CuAINi HTSMA actuated airfoil will demonstrate a cooling time two to six times lower than its NiTi SMA counterpart.