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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Simulation of the thermomechanical behavior of shape memory alloys under multiaxial nonproportional loading
 Lynch, C.S. ; Society of PhotoOptical Instrumentation Engineers SPIE, Bellingham/Wash.: Smart structures and materials 2000  Active materials. Behavior and mechanics : 6  9 March 2000, Newport Beach, USA Bellingham, WA: SPIE, 2000 (Proceedings of SPIE 3992) ISBN: 0819436100 pp.484495 
 Conference "Smart Structures and Materials 2000  Active Materials. Behavior and Mechanics" <2000, Newport Beach/Calif.> 

 English 
 Conference Paper 
 Fraunhofer ITWM () 
Abstract
The paper presents a mathematical description of shape memory alloys within the framework of continuum mechanics, where the spatially multidimensional case is considered. A new simple model is introduced, which correctly describes not only all wellstudied shape memory effects but also the more complex behavior. The key idea is a new set of internal state variables, which are averaged values for a representative volume element of the polycrystalline material. A tensorvalued variable describes the state of orientation of martensite. The relative volume fraction of stress induced martensite is defined by taking a certain tensor norm of this internal variable. A free energy is chosen and thermodynamical forces are derived. These forces are sufficient to define the onset of the phase transitions, so that we do not need to introduce transition surfaces explicitly within the evolution equations. Finite element discretizations for the approximation of the field variables and finite difference approximations for the time integration of local variables are explained.