zur Erlangung des Grades des Doktors der Ingenieurwissenschaften (original) (raw)

Use the Force: Review of High-Rate Actuation of Shape Memory Alloys

Actuators

Typical shape memory alloy actuators provide a unique combination of large stresses and strains that result in work-per-volume larger by more than two orders of magnitude than all other actuation methods that are based on active materials. High-rate actuation of shape memory alloys can provide improved energy efficiency, and shorter response and total actuation times, along with large travel-per-wire-length, with respect to slow-rate SMA applications. In this article, we review the different aspects of high-rate actuation of shape memory alloy wires in the high-driving-force regime. We briefly survey previous experimental results about the kinetics and thermodynamics of the phase transformation in view of its practical implications. New experimental results, regarding energy efficiency, total actuation time, repeatability, and fatigue, are presented and discussed. The paper provides general design guidelines for obtaining high actuator performance, as well as guidelines for selectin...

Experimental Platform for Obtaining Electrical Resistance of a Shape Memory Alloy Actuator

2021

Shape Memory Alloys (SMA) are unique metallic materials with the Shape Memory Effect (SME), which refers to a material’s capacity to recover its original shape through temperature variation subjected to deformations. These alloys are commonly used as actuators to control vibration, deformation, position and have been used in several sectors in the last decades. Therefore, in order to enable a study about the behavior of the electrical resistance of an SMA actuator and the deformation measurement using strain-gauge sensors, an experiment is proposed in this work to be applied to the course of Electronic Instrumentation Laboratory of Electrical Engineering Degree at the Federal University of Campina Grande, Brazil. We used an experimental platform composed of a steel beam and an SMA actuator, and we also developed the necessary electronic system and Human Machine Interface. The experiment consists of activating the actuator by applying electric current and obtaining data corresponding...

Smartflex NiTi Wires for Shape Memory Actuators

Advances in Science and Technology, 2008

Shape memory alloys (SMAs) are active metallic materials classified nowadays as ''smart'' or ''intelligent'' materials. One of their main areas of interest is that of actuators. The use of SMAs in actuators offers the opportunity to develop robust, simple, and lightweight elements that can represent an alternative to electro-magnetic actuators commonly used in several fields of industrial applications, such as automotive, appliances, etc. SAES Getters S.p.A. thanks to its vertically integrated process and to the scientific and quality approach, developed a NiTi-based wires family which can represent a solution for shape memory actuators. In this paper, the mechanical, thermal, and electrical response of these shape memory wires, with diameters ranging from 20 to 500 lm, will be examined and discussed, with particular focus on the design of the actuator. The thermo-mechanical properties have been investigated and measured by several methods. The most common and useful tests for these commercially available wires will be also described.

Functional Characterization of a Novel Shape Memory Alloy

Journal of Materials Engineering and Performance, 2014

ABSTRACT A novel shape memory alloy (SMA) has been developed as an alternative to currently available alloys. This alloy, commercially known by its proprietary brand SMARQ, shows a higher working range of temperatures with respect to the SMA materials used until now in actuators, limited to environment temperatures below 90 A degrees C. SMARQ is a high temperature SMA (HTSMA) based on a fully European material technology and production processes, which allows the manufacture of high quality products, with tuneable transformation temperatures up to 200 A degrees C. Both, material and production processes have been evaluated for its use in space applications. A full characterization test campaign has been completed in order to obtain the material properties and check its suitability to be used as active material in space actuators. In order to perform the functional characterization of the material, it has been considered as the key element of a basic SMA actuator, consisting in the SMA wire and the mechanical and electrical interfaces. The functional tests presented in this work have been focused on the actuator behavior when heated by means of an electrical current. Alloy composition has been adjusted in order to match a transition temperature (As) of +145 A degrees C, which satisfies the application requirements of operating temperatures in the range of -70 and +125 A degrees C. Details of the tests and results of the characterization test campaign, focused in the material unique properties for their use in actuators, will be presented in this work. Some application examples in the field of space mechanisms and actuators, currently under development, will be summarized as part of this work, demonstrating the technology suitability as active material for space actuators.

Tailoring the response time of shape memory alloy wires through active cooling and pre-stress

Journal of Intelligent Material …, 2010

Application of shape memory alloy (SMA) actuators is limited to low frequencies due to slow cooling time especially in the embedded conditions where heat transfer rate is the controlling factor. In this study, we investigate various active cooling techniques and effect of pre-stress to improve the response time of two commercially available SMAs: Flexinol from Dynalloy Inc. and Biometal fiber from Toki Corporation. Flexinol and Biometal fiber of equal length and diameter were found to exhibit different actuation behavior under pre-stress. Time domain force response of SMA actuators was found to be dependent upon the applied prestress, heating rate, and amplitude of applied electrical stimulus. Compared to Biometal fibers, time domain response of Flexinol was found to decrease significantly with increasing pre-stress indicating the difference in transformation behavior. Fluid flow and heat sinking were found to be suitable methods for improving the response time by reducing the cooling cycle from 1.6 s to 0.300.45 s. This is a significant improvement in the actuation capability of SMAs.

Shape Memory Alloy Actuators: A Review

International Journal for Research in Applied Science and Engineering Technology

The Shape memory alloys (SMAs) comes under special class of materials which possesses ability to recover their original shape at some temperatures characteristics. The SMAs are being used in different field in variety of applications. This ability of SMA can be viewed under high applied loads and elastic deformations. In this review paper, the SMA actuators and their applications are discussed. Keywords: SMA, Types of SMA, actuator. I. INTRODUCTION The term ''smart alloy'' was introduced in 1932 and the nomenclature ''shape-memory'' was given in 1941 for polymeric dental material [1, 2, 3]. Shape memory alloys (SMAs) are a unique type of material contains the ability to recover their shape at certain temperature characteristics. These materials are able to regain their original shape, even after reaching large inelastic deformations (near 10%) [1]. The demand for SMAs for engineering applications has been increasing in different fields; such as in industrial applications, automobile industries, aerospace applications, structures and composites, robotics and biomedical applications [4, 5]. Different SMA actuators like wire, compression / tension springs and cantilever had been used in thermal and electrical actuation systems [7, 33]. In this paper, a review on different applications of SMA actuators is presented.

Precise position control using shape memory alloy wires

Turkish Journal of Electrical Engineering Computer Sciences, 2010

Shape memory alloys (SMAs) are active metallic "smart" materials used as actuators and sensors in high technology smart systems . The term shape memory refers to ability of certain materials to "remember" a shape, even after rather severe deformations: once deformed at low temperatures, these materials will stay deformed until heated, whereupon they will return to their original, pre-deformed "learned" shape .

Recent Advancement in Shape Memory Alloy

Shape memory alloys (SMAs) belong to a class of shape memory materials (SMMs), which have the ability to 'memorise' or retain their previous form when subjected to certain stimulus such as thermo mechanical or magnetic variations. SMAs have drawn significant attention and interest in recent years in a broad range of commercial applications, due to their unique and superior properties; this commercial development has been supported by fundamental and applied research studies. This work describes the attributes of SMAs that make them ideally suited to actuators in various applications, and addresses their associated limitations to clarify the design challenges faced by SMA developers. This work provides a timely review of recent SMA research and commercial applications, with over 100 state-of-the-art patents; which are categorized against relevant commercial domains and rated according to design objectives of relevance to these domains (particularly automotive, aerospace, robotic and biomedical). Although this work presents an extensive review of SMAs, other categories of SMMs are also discussed; including a historical overview, summary of recent advances and new application opportunities.