73 research outputs found
Homogenization in magnetic-shape-memory polymer composites
Magnetic-shape-memory materials (e.g. specific NiMnGa alloys) react with a
large change of shape to the presence of an external magnetic field. As an
alternative for the difficult to manifacture single crystal of these alloys we
study composite materials in which small magnetic-shape-memory particles are
embedded in a polymer matrix. The macroscopic properties of the composite
depend strongly on the geometry of the microstructure and on the
characteristics of the particles and the polymer.
We present a variational model based on micromagnetism and elasticity, and
derive via homogenization an effective macroscopic model under the assumption
that the microstructure is periodic. We then study numerically the resulting
cell problem, and discuss the effect of the microstructure on the macroscopic
material behavior. Our results may be used to optimize the shape of the
particles and the microstructure.Comment: 17 pages, 4 figure
FEM simulation of the Nitinol wire
In recent years, one of the most promising new actuator technologies is based on the use of Shape Memory Alloys (SMA). The main challenge for the application of devices that use these materials is the hysteresis in the phase transition they suffer during actuation. Finite element analysis (FEA) is an important aid in the simulation of mechanical properties and thermal fields in actuators. Dynamic simulations give in many cases enough information without the necessity of building a prototype. We have used ABAQUS to simulate a Nitinol wire used in a micropositioning actuator. The model parameters, not given by the supplier but required by the FEA program, have been obtained by thermal and mechanical characterization of the material used. The output force is computed and compared with the measurements
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