SHAPE-MEMORY ALLOYS - MACROMODELLING AND NUMERICAL SIMULATIONS OF THESUPERELASTIC BEHAVIOR

Shape-memory alloys show features not present in materials traditional ly used in engineering; as a consequence, they are the basis for innov ative applications. A review of the available literature shows a deart h of computational tools to support the design process of shape-memory -alloy devices. A major reason is that conventional inelastic models d o not provide an adequate framework for representing the unusual macro behavior of shape-memory materials. The present work focuses on a new family of inelastic models, based on an internal-variable formalism an d known as generalized plasticity. Generalized plasticity is adopted h erein as framework for the development of one- and three-dimensional c onstitutive models for shape-memory materials. The proposed constituti ve models reproduce some of the basic features of shape-memory alloys, such as superelasticity, different material behavior in tension and c ompression, and the single-variant-martensite reorientation process. F or isothermal conditions the implementation of the model in a finite-e lement scheme and the form of the algorithmically consistent tangent a re discussed in detail. Numerical simulations of typical tests perform ed on shape-memory materials (e.g. uniaxial Loading, four-point bendin g and three-point bending tests) are presented and compared with avail able experimental data. Based on the overall developments, it appears that the proposed approach is a viable basis for the development of an effective computational tool to be used in the simulation of shape-me mory-alloy devices.