Shape Memory Alloys: Alloy Behavior
Sponsored by: MS&T Organization
Program Organizers: Mohammad Elahinia, University of Toledo
Tuesday 2:00 PM
October 18, 2011
Room: D242/243
Location: Greater Columbus Convention Center
Session Chair: Walter Anderson, University of Toledo
2:00 PM Student
Development of Simulation Tools for Analysing the Actuation of Smart Materials: Velaphi Msomi1; Kazeem Sanusi2; Graeme Oliver1; Oscar Philander1; 1Cape Peninsula University of Technology; 2Stellenbosch University
In order to predict the hinge-moments produced by smart material actuation as well as the strength of smart material components, a reliable material model needs to be developed for each smart material. This material model can then be used in the finite element analysis of structures containing smart actuators. These could either be embedded actuators or linkages made of smart material. In this paper we show a developed thermo-mechanical model that can be used for modelling NiTi Shape Memory Alloy material. The developed constitutive model can be utilized to analyze simple and complex structures/shapes. It was developed based on the approach by Liang and Rogers. The phase transformation occurring in the SMA microstructure and the temperature variation are treated as internal variables for this model. The simulated results are presented and analyzed.
2:20 PM
Mechanical Properties of High Strength NiTiHfPd Shape Memory Alloys: Haluk Karaca1; Burak Basaran1; Emre Acar1; Ronald Noebe2; 1UNIVERSITY OF KENTUCKY; 2NASA
Near equiatomic NiTi (49-51 at% Ni) has been the workhorse of shape memory alloy (SMA) applications due its excellent ductility and shape memory properties. Though, it can only operate below 100 C, has limited strength (< 700 MPa) and unstable cyclic-behavior at high stress and temperatures. Higher strength shape memory alloys could be employed in the oil-gas, aerospace and automotive industries as linear actuators, connectors, sealants, flow control devices, actuation tubes, and moving or morphing inlet/exhaust configurations. In this study, shape memory and superelasticity properties of NiTiHfPd SMAs as functions of heat-treatment temperature and time will be revealed to prove that their transformation temperatures can be adjusted by aging to range from cryogenic to elevated temperatures (-200 to 100 C). We also show that NiTiHfPd possess the ability to operate under extremely high stress levels (~2 GPa), exhibit large damping capacity and generate several times higher work output than NiTi.
2:40 PM Student
The Effect of Boundary Condition on the Torsional Profile of the NiTi Superelastic Wires: Zohreh Karbaschi1; Ehsan Izadi1; Mohammad Elahinia1; 1The University of Toledo
The torsional behavior of shape memory alloys has been investigated in various studies. However, the effect of the boundary condition has not been taken into account. The goal of this study is to investigate the effect of boundary condition on the torsional behavior of superelastic NiTi wires. To this end a torsional model was developed in MATLAB by which the effect of different boundary conditions was modeled. Tensile and torsional tests were performed on NiTi wires under various boundary conditions and the torque-angle profile of the experiments were compared with model’s prediction. Two different boundary conditions were investigated, first the wires were subjected to pure torsional loading in which the axial movement was allowed and second, the wires were fixed at both ends. Experimental results indicated significant variation in the torsional behavior of the alloy as the boundary condition changed. The model’s prediction showed good agreement with the experimental results.