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Dimensionnement d'éléments simples en alliage à mémoire de forme

Abstract : Shape memory properties were first observed in metals more than fifty years ago. The metals exhibiting these properties (superelasticity, one and two way memory effects, ...) are called Shape Memory Alloys (SMA). Despite the potentiality of these alloys and the amount of patents, successful industrial and commercial applications remain exceptions. This can be explained by the lack of design tools able to dimension correctly SMA elements. Even if a lot of study were conducted to describe the behavior of SMA, very few work have been done considering these alloys as mechanical elements where the stress distribution is in many cases, inhomogeneous. In this work, structure calculations are performed with these materials; At first a modeling of the behavior of SMA is developed. This inelastic behavior depends strongly on the temperature and exhibits an hysteresis. The non symmetry between tensile and compressive tests observed experimentally is also taken into account through the definition of a non symmetric transformation criterion. From this criterion, an associated flow rule is obtained to describe the SMA behavior. Hysteretic effects are accounted introducing a kinematical hardening parameter. Considering the geometry of the most common elements made of SMA, structure calculation is performed into the framework of beam theory. To determine the response of SMA structures, an incremental formulation of Bresse integrals is used taking account of the coexistence of transforming zones and elastic ones during the loading and the unloading process. The results obtained by this way are successfully compared with experimental ones performed on superelastic springs and beams made of copper based SMA. Material parameters required for the computation are experimentally determined using tensile test and calorimetric measurements. An extension to thermomechanical loading also presented in this study
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Yves Gillet. Dimensionnement d'éléments simples en alliage à mémoire de forme. Autre. Université Paul Verlaine - Metz, 1994. Français. ⟨NNT : 1994METZ051S⟩. ⟨tel-01776802⟩

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