Download or read book Thermomechanical Training and Characterization of Shape Memory Alloy Axial Actuators written by Marcus Patrick Becker and published by . This book was released on 2010 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Shape Memory Alloy Actuators written by Mohammad H. Elahinia and published by John Wiley & Sons. This book was released on 2016-01-19 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Thermo mechanical Characterization of Shape Memory Alloy Torque Tube Actuators written by Andrew Christian Keefe and published by . This book was released on 1999 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermomechanical Modeling and Analysis of Flexible Structures with Shape Memory Alloy Actuators written by Steven Gongming Shu and published by . This book was released on 1996 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermomechanical Behavior of High temperature Shape Memory Alloy Ni Ti Pd Pt Actuators written by Douglas E. Nicholson and published by . This book was released on 2011 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: To date the commercial use of shape memory alloys (SMAs) has been mostly limited to binary NiTi alloys with transformation temperatures approximately in the -100 to 100°C range. In an ongoing effort to develop high-temperature shape memory alloys (HTSMAs), ternary and quaternary additions are being made to binary NiTi to form NiTi-X (e.g., X: Pd, Pt, Au and Hf) alloys. Stability and repeatability can be further increased at these higher temperatures by limiting the stress, but the tradeoff is reduced work output and stroke. However, HTSMAs operating at decreased stresses can still be used effectively in actuator applications that require large strokes when used in the form of springs. The overall objective of this work is to facilitate the development of HTSMAs for use as high-force actuators in active/adaptive aerospace structures. A modular test setup was assembled with the objective of acquiring stroke, stress, temperature and moment data in real time during joule heating and forced convective cooling of Ni19.5Ti50.5Pd25Pt5 HTSMA springs. The spring actuators were evaluated under both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Recognizing that evolution in the material microstructure results in changes in geometry and vice versa in HTSMA springs, the objective of the present study also included assessing the contributions from the material microstructural evolution, by eliminating contributions from changes in geometry, to overall HTSMA spring performance. The finite element method (FEM) was used to support the analytical analyses and provided further insight into the behavior and heterogeneous stress states that exist in these spring actuators. Furthermore, with the goal of improving dimensional stability there is a need to better understand the microstructural evolution in HTSMAs that contributes to irrecoverable strains. Towards this goal, available Ni29.5Ti50.5Pd20 neutron diffraction data (from a comparable HTMSA alloy without the solid solution strengthening offered by the Pt addition) were analyzed. The data was obtained from in situ neutron diffraction experiments performed on Ni29.5Ti50.5Pd20 during compressive loading while heating/cooling, using the Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory. Specifically, in this work emphasis was placed on neutron diffraction data analysis via Rietveld refinement and capturing the texture evolution through inverse pole figures. Such analyses provided quantitative information on the evolution of lattice strain, phase volume fraction (including retained martensite that exists above the austenite finish temperature) and texture (martensite variant reorientation and detwinning) under temperature and stress. Financial support for this work from NASA's Fundamental Aeronautics Program Supersonics Project (NNX08AB51A), Subsonic Fixed Wing Program (NNX11AI57A) and the Florida Center for Advanced Aero-Propulsion (FCAAP) is gratefully acknowledged. It benefited additionally from the use of the Lujan Neutron Scattering Center at Los Alamos National Laboratory, which is funded by the Office of Basic Energy Sciences (Department of Energy) and is operated by Los Alamos National Security LLC under DOE Contract DE-AC52-06NA25396.

Download or read book Design of Shape Memory Alloy SMA Actuators written by Ashwin Rao and published by Springer. This book was released on 2015-05-08 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book A Fundamental Characterization of Shape Memory Alloy Actuators for Use in Hand Protheses written by Mark Anthony Thrasher and published by . This book was released on 1991 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cryogenic Shape Memory Alloy Actuators for Spaceport Technologies written by Jennifer L. Lemanski and published by . This book was released on 2005 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shape memory alloys (SMAs) possess the unique ability to change their shape by undergoing a solid-state phase transformation at a particular temperature. The shape change is associated with a large strain recovery as the material returns to its "remembered" shape. Their ability to act as both sensor and actuator has made them an attractive subject of study for numerous applications. SMAs have many characteristics which are advantageous in space-related applications, including generation of large forces associated with the strain recovery, smooth and controlled movements, large movement to weight ratio, high reliability, and spark-free operation. The objective of this work is the further development and testing of a cryogenic thermal conduction switch as part of NASA funded projects. The switch was developed to provide a variable conductive pathway between liquid methane and liquid oxygen dewars in order to passively regulate the methane temperature. Development of the switch concept has been continued in this work by utilizing Ni-Ti-Fe as the active SMA element. Ni-Ti-Fe exhibits the shape memory effect at cryogenic temperatures, which makes it well suited for low temperature applications. This alloy is also distinguished by an intermediate phase change known as the rhombohedral or R-phase, which is characterized by a small hysteresis (typically 1-2 deg C) and offers the advantage of precise control over a set temperature range. For the Ni-Ti-Fe alloy used, its thermomechanical processing, subsequent characterization using dilatometry and differential scanning calorimetry and implementation in the conduction switch configuration are addressed. This work was funded by grants from NASA KSC (NAG10-323) and NASA GRC (NAG3-2751).

Download or read book Thermomechanical Modeling and Experimentation for SMA Actuators Under Cyclic Loading written by and published by . This book was released on 2002 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Smart Structures Theory written by Inderjit Chopra and published by Cambridge University Press. This book was released on 2014 with total page 925 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on smart materials and structures, which are also referred to as intelligent, adaptive, active, sensory, and metamorphic. The ultimate goal is to develop biologically inspired multifunctional materials with the capability to adapt their structural characteristics, monitor their health condition, perform self-diagnosis and self-repair, morph their shape, and undergo significant controlled motion.

Download or read book Shape Memory Alloy Actuators written by Burcu Dönmez and published by . This book was released on 2011-11 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization and Modeling of Transformation Induced Fatigue of Shape Memory Alloy Actuators written by Olivier Walter Bertacchini and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The main focus of this research is the transformation induced fatigue behavior of shape memory alloy (SMA) actuators undergoing thermally induced martensitic phase transformation. The recent development of aerospace applications employing shape memory alloys (SMAs) has expanded the need for fatigue life characterization and modeling. Lightweight, compact and with a great work output, SMAs are ideal materials for actuated structural components. However, fatigue life becomes a key factor in applications such as commercial airplanes. Therefore, it is necessary to not only perform fatigue testing but also to investigate the causes of fatigue failure. As a new class of materials, SMAs have unique characteristics and require novel test methodologies to conduct repeatable and reliable fatigue testing. For this research, two materials are being investigated: TiNiCu and Ni-rich NiTi. The experiments performed on the first selected alloy, i.e. TiNiCu SMA, explore three major parameters: the applied stress level, the amount of actuation, and the corrosive nature of the environment. Experimental results show that SMAs undergoing transformation induced fatigue exhibit a low-cycle fatigue behavior and the measurement of the accumulated plastic strain at failure is associated to a Manson-Coffin type failure criterion. Investigations conducted on the post-mortem microstructure showed evidence of a multiphysical coupling between corrosion and cyclic phase transformation, from which a novel cyclic damage mechanism is proposed and explained using the micromechanical shear lag model accounting for actuation and accumulated plastic strains. Thereafter, based upon the identified failure mechanism and considering damage accumulation through crack formation, a stress renormalization procedure is proposed in combination with the Miner's rule to predict the reduction of number of cycles to failure due to cyclic phase transformation and corrosion. A direct method is first presented and the predictions show good agreement with experimental results. However, both corrosion and corrosion-free fatigue data are required. Therefore, a new approach is proposed: the inverse Miner's rule, which requires corrosion fatigue data only to predict corrosion-free life. The new and attractive properties of the selected second alloy, i.e. Ni-rich NiTi SMA, have revived the motivation of the aerospace industry to design SMA actuators. One particular property is cyclic stability generated by precipitation hardening mechanism using precipitates. However, are also precipitates due to high Nickel content (60 wt.% or 55 at.%). Parameters such as processing, heat treatments, size effects, surface quality and environment are investigated. Thermomechanical response and fatigue life are discussed and the greatest impact is found to come from specimen surface quality. Finally, a detailed fractography presents the different microstructural aspects of the fatigue damage and concludes to a precipitation driven fatigue failure mechanism cause by precipitates.

Download or read book Linear Shape Memory Alloy Thermomechanical Actuators written by Velaphi Msomi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The thermally activated changes in crystal structure in nickel-titanium shape memory alloy (SMA) material, which produces transformation strains of an order of magnitude higher than and opposite to the thermal strains, have been described using different models. Some of these models are defined by cyclic functions (trigonometric functions) which they become complex to control when they are subjected to a wide range of transformation temperatures. This chapter presents an alternative model to better describe the behavior of SMA for a more general temperature range, which an SMA-powered actuator might be subjected to. The proposed model is then implemented to the analysis of one-dimensional (1D) problem oriented to the two-dimensional (2D) space. The simulation results were then graphically compared to the experiment.

Download or read book Fabrication Characterization and Implementation of Actuators Based on Thin Shape Memory Alloy Films written by Meni Kabla and published by . This book was released on 2015 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermomechanical Modeling of Shape Memory Alloy based Microactuators written by Marian Hörsting and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design and Characterization of Acoustic Pulse Shape Memory Alloy Actuators written by Joshua Michael Chambers and published by . This book was released on 2005 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Single crystal Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) are active materials which produce strain when a magnetic field is applied. The large saturation strain (6%) of Ni-Mn-Ga, and material energy density comparable to piezoelectric ceramics make Ni- Mn-Ga an interesting active material. However, their usefulness is limited by the bulky electromagnet required to produce a magnetic field. In this thesis, a novel actuation method is developed for shape memory alloys in their martensitic phase, whereby asymmetric acoustic pulses are used to drive twin boundary motion. Experimental actuators were developed using a combination of Ni-Mn-Ga FSMA single crystals and a piezoelectric stack actuator. In bi-directional actuation without load, strains of over 3% were achieved using repeated pulses (at 100 Hz) over a 30 s interval, while 1% strain was achieved in under 1 s. The maximum strains achieved are comparable to the strains achieved using bi-directional magnetic actuation, although the time required for actuation is longer. No-load actuation also showed a nearly linear relationship between the magnitude of the asymmetric stress pulse and the strain achieved during actuation, and a positive correlation between pulse repetition rate and output strain rate, up to at least 100 Hz. Acoustic actuation against a spring load showed a maximum output energy density for the actuator of about 1000 J/m3, with a peak-to-peak stress and strain of 100 kPa and 2%, respectively.

Download or read book Shape Memory Alloy Engineering written by Antonio Concilio and published by Elsevier. This book was released on 2014-09-25 with total page 449 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shape Memory Alloy Engineering introduces materials, mechanical, and aerospace engineers to shape memory alloys (SMAs), providing a unique perspective that combines fundamental theory with new approaches to design and modeling of actual SMAs as compact and inexpensive actuators for use in aerospace and other applications. With this book readers will gain an understanding of the intrinsic properties of SMAs and their characteristic state diagrams, allowing them to design innovative compact actuation systems for applications from aerospace and aeronautics to ships, cars, and trucks. The book realistically discusses both the potential of these fascinating materials as well as their limitations in everyday life, and how to overcome some of those limitations in order to achieve proper design of useful SMA mechanisms. Discusses material characterization processes and results for a number of newer SMAs Incorporates numerical (FE) simulation and integration procedures into commercial codes (Msc/Nastran, Abaqus, and others) Provides detailed examples on design procedures and optimization of SMA-based actuation systems for real cases, from specs to verification lab tests on physical demonstrators One of the few SMA books to include design and set-up of demonstrator characterization tests and correlation with numerical models