Shape-memory-alloys (SMA) present very special features. In particular, because of the austenite-martensite and martensite-austenite transformations, governed by the temperature and the stress state, they can undergo large deformations, showing the so-called superelastic behavior and the shape memory effect. The superelastic behavior occurs when, for a fixed value of the temperature, the material recovers its natural state after a loading-unloading stress cycle. The shape memory effect occurs when an inelastic strain is present after a loading-unloading stress cycle; this in elastic strain can be recovered by a further temperature cycle. Because of the very special material behavior, SMA are successfully adopted in many advanced systems; they are adopted as orthodontic wires, as self-expanding micro-structures in the treatment of blood vessel occlusions, as devices to control the spatial antennas opening, to name a few. Beams, plates and shells represent the most common elements for SMA applications. Several models have been proposed in the last decade to reproduce the SMA constitutive behavior. In fact, different micromechanical and macromechanical approaches are distinguished in the literature in the SMA modeling. In the present paper, a simple SMA model to simulate the superelastic behavior as well as the shape memory effect is proposed. It considers only the transformations from austenite to single variant martensite and from single variant martensite to austenite, taking into account the influence of the temperature in the constitutive relationship. The proposed SMA constitutive law is used in beam elements that neglect or include the transverse shear deformation. The new SMA beam finite elements are formulated using suitable approximation functions. The proposed finite elements are developed within a numerical procedure for the time integration of the SMA constitutive equations. In particular, the developed elements allow the use of SMA material as a reinforcement of elastic beams. Several applications are presented to assess the model and the proposed numerical procedure.
Laminated SMA beams finite elements / S., Marfia; Sacco, E.; Reddy, J. N.. - 1:(2002). ( 5th World Congress on Computational Mechanics Wien (Austria) 7-12 July 2002).
Laminated SMA beams finite elements
SACCO E.
;
2002
Abstract
Shape-memory-alloys (SMA) present very special features. In particular, because of the austenite-martensite and martensite-austenite transformations, governed by the temperature and the stress state, they can undergo large deformations, showing the so-called superelastic behavior and the shape memory effect. The superelastic behavior occurs when, for a fixed value of the temperature, the material recovers its natural state after a loading-unloading stress cycle. The shape memory effect occurs when an inelastic strain is present after a loading-unloading stress cycle; this in elastic strain can be recovered by a further temperature cycle. Because of the very special material behavior, SMA are successfully adopted in many advanced systems; they are adopted as orthodontic wires, as self-expanding micro-structures in the treatment of blood vessel occlusions, as devices to control the spatial antennas opening, to name a few. Beams, plates and shells represent the most common elements for SMA applications. Several models have been proposed in the last decade to reproduce the SMA constitutive behavior. In fact, different micromechanical and macromechanical approaches are distinguished in the literature in the SMA modeling. In the present paper, a simple SMA model to simulate the superelastic behavior as well as the shape memory effect is proposed. It considers only the transformations from austenite to single variant martensite and from single variant martensite to austenite, taking into account the influence of the temperature in the constitutive relationship. The proposed SMA constitutive law is used in beam elements that neglect or include the transverse shear deformation. The new SMA beam finite elements are formulated using suitable approximation functions. The proposed finite elements are developed within a numerical procedure for the time integration of the SMA constitutive equations. In particular, the developed elements allow the use of SMA material as a reinforcement of elastic beams. Several applications are presented to assess the model and the proposed numerical procedure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
