Modeling of Stress Concentrations in SMA Components Considering Plastic and Viscoplastic Yielding
The compact actuation solutions provided by shape memory alloys (SMAs) continue to be explored by engineers and designers in the aerospace industry. However, the response of this material at stress concentrations such as fastener installations has not been widely studied. This work describes the theoretical constitutive models and numerical implementation required to analyze the coupled evolution of both recoverable and irrecoverable inelastic strains in SMA bodies that include stress concentrations. The irrecoverable strains can be induced by high local stresses at conventional temperatures, where they are rate-independent. They can also be induced by moderate local stresses at higher temperatures, where they are rate-dependent. SMA components are being designed for use in each of these conditions, and thus it is important that analytical tools accounting for both be developed. This work addresses both rate-independent and rate-dependent evolution of irrecoverable strains in SMAs. After review of the mathematical models, two example analyses are considered, one in which the stress concentration is represented by a crack tip, and another where it is represented by a circumferential notch in a cylindrical tensile specimen. These analyses demonstrate the importance of considering the coupled evolution of inelastic strains, both recoverable and irrecoverable. Copyright 2009 by the American Institute of Aeronautics and Astronautics, Inc.
name of conference
50th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference