An experimentally validated thermomechanical actuation model for shape memory alloy (SMA) actuators undergoing non proportional cyclic loading, fully coupled with the evolution of plastic strains is developed. The model is numerically implemented in a form suitable for finite element analysis. Material characterization of SMA actuators is also performed in this research effort. Emphasis is given on the effect of plastic strains on the properties of SMA actuators. The data collected during the characterization is utilized to calibrate the thermomechanical SMA model. After the model is calibrated, different loading cases are investigated, including non-proportional loading paths. Finally, the fatigue life of SMA actuators is also investigated. A test frame for fatigue experiments is developed and numerous fatigue tests are performed.

This book provides a systematic approach to realizing NiTi shape memory alloy actuation, and is aimed at science and engineering students who would like to develop a better understanding of the behaviors of SMAs, and learn to design, simulate, control, and fabricate these actuators in a systematic approach. Several innovative biomedical applications of SMAs are discussed. These include orthopedic, rehabilitation, assistive, cardiovascular, and surgery devices and tools. To this end unique actuation mechanisms are discussed. These include antagonistic bi-stable shape memory-superelastic actuation, shape memory spring actuation, and multi axial tension-torsion actuation. These actuation mechanisms open new possibilities for creating adaptive structures and biomedical devices by using SMAs.

Written by leading experts in the field, this book highlights an authoritative and comprehensive introduction to thermo-mechanically coupled cyclic deformation and fatigue failure of shape memory alloys. The book deals with: (1) experimental observations on the cyclic deformation and fatigue failure in the macroscopic and microscopic scales; (2) molecular dynamics and phase-field simulations for the thermo-mechanical behaviors and underlying mechanisms during cyclic deformation; (3) macroscopic phenomenological and crystal plasticity-based cyclic constitutive models; and (4) fatigue failure models. This book is an important reference for students, practicing engineers and researchers who study shape memory alloys in the areas of mechanical, civil and aerospace engineering as well as materials science.

This short monograph presents an analysis and design methodology for shape memory alloy (SMA) components such as wires, beams, and springs for different applications. The solid-solid, diffusionless phase transformations in thermally responsive SMA allows them to demonstrate unique characteristics like superelasticity and shape memory effects. The combined sensing and actuating capabilities of such materials allows them to provide a system level response by combining multiple functions in a single material system. In SMA, the combined mechanical and thermal loading effects influence the functionality of such materials. The aim of this book is to make the analysis of these materials accessible to designers by developing a "strength of materials" approach to the analysis and design of such SMA components inspired from their various applications with a review of various factors influencing the design process for such materials.

Although considerable work has been performed to understand the key mechanisms of Shape Memory Alloy (SMA) behavior, little of this work follows a standard testing protocol, quantifies a conditioning methodology, or develops data appropriate for design of SMA actuators. One major issue that limits the ability of the material from being used directly as an actuator is the large, non-recoverable strains likely to accrue in the material during each training cycle, mechanical or thermal. When mechanical or thermal cycling is performed, a hysteresis curve develops and reaches a steady state strain recovery response. At the point where permanent plastic strain stops growing, or saturates, the SMA has been successfully trained. The focus of this work is oriented toward SMAs in general, but all testing and experimentation was carried out on Nickel-Titanium (NiTi) alloys. The experimentation and testing was performed on a combination of 4 different sizes and 3 different NiTi alloy compositions. Thermomechanical testing was performed to determine critical values to describe the stress-temperature phase space of the materials and parameters to model the applied stress and transformation strain relationship. All material size and alloy combinations were tested in the as-received, or as-machined, and fully annealed state. The results of the training and actuation strain characterization process developed in this work shows that the samples that experienced Transformation Induced Plasticity (TRIP), greater than 2% during the training process and exhibit Two-Way Shape Memory (TWSM) after being fully trained, share a very similar applied stress versus transformation strain curve. This curve is modeled by the Back Stress formulation derived from the Gibbs Free Energy constitutive model by Bo & Lagoudas. The design space created by the Back Stress formulation, recrystallization temperature, and training stress allows SMA materials to be characterized and implemented as stable 1-D actuators. This research formalized a thermomechanical training and characterization method for uniaxial SMA actuators by addressing the interaction between processing, recoverable and non-recoverable deformation. Using various sizes and NiTi alloy combinations, this research develops and evaluates a method to train and characterize a diverse range of SMAs through a set of thermomechanical and physical property measurements.

New contributions to the cyclic plasticity of engineering materials Written by leading experts in the field, this book provides an authoritative and comprehensive introduction to cyclic plasticity of metals, polymers, composites and shape memory alloys. Each chapter is devoted to fundamentals of cyclic plasticity or to one of the major classes of materials, thereby providing a wide coverage of the field. The book deals with experimental observations on metals, composites, polymers and shape memory alloys, and the corresponding cyclic plasticity models for metals, polymers, particle reinforced metal matrix composites and shape memory alloys. Also, the thermo-mechanical coupled cyclic plasticity models are discussed for metals and shape memory alloys. Key features: Provides a comprehensive introduction to cyclic plasticity Presents Macroscopic and microscopic observations on the ratchetting of different materials Establishes cyclic plasticity constitutive models for different materials. Analysis of cyclic plasticity in engineering structures. This book is an important reference for students, practicing engineers and researchers who study cyclic plasticity in the areas of mechanical, civil, nuclear, and aerospace engineering as well as materials science.

Intelligent Materials and Structures provides exceptional insights into designing intelligent materials and structures for special applications in engineering. The author introduces the fundamental materials science involved in research endeavors and simultaneously reviews the current state-of-the-art of intelligent materials and structures. Separate chapters are devoted to the thorough examination of theory and application of laminated composite materials, Piezoelectricity, Shape Memory Alloys, Electro- and Magnetorheological fluids as well as Magneto- and Electrostrictive materials. Each chapter contains numerous equations and figures describing theories, models and behavior of the intelligent material discussed. Special attention is paid to applications of intelligent materials to various structures in the aerospace and medical sector, piezoelectric motors as well as piezoelectric and electromagnetic energy harvesting. Contents: Introduction to Intelligent Materials and Structures Laminated Composite Materials Piezoelectricity Shape Memory Alloys Electrorheological and Magnetorheological Fluids Magnetostrictive and Electrostrictive Materials Applications of Intelligent Materials in Structures Energy Harvesting using Intelligent Materials Index