Bioinspired Soft Actuation System Using Shape Memory Alloys

Soft robotics requires technologies that are capable of generating forces even though the bodies are composed of very light, flexible and soft elements. A soft actuation mechanism was developed in this work, taking inspiration from the arm of the Octopus vulgaris, specifically from the muscular hydrostat which represents its constitutive muscular structure. On the basis of the authors’ previous works on shape memory alloy (SMA) springs used as soft actuators, a specific arrangement of such SMA springs is presented, which is combined with a flexible braided sleeve featuring a conical shape and a motor-driven cable. This robot arm is able to perform tasks in water such as grasping, multi-bending gestures, shortening and elongation along its longitudinal axis. The whole structure of the arm is described in detail and experimental results on workspace, bending and grasping capabilities and generated forces are presented. Moreover, this paper demonstrates that it is possible to realize a self-contained octopus-like robotic arm with no rigid parts, highly adaptable and suitable to be mounted on underwater vehicles. Its softness allows interaction with all types of objects with very low risks of damage and limited safety issues, while at the same time producing relatively high forces when necessary

Shape Memory Actuator: thermomechanical training and surface optimization of shape memory wires embedded in a polymeric matrix

In the first part of my work I studied the mechanical and thermal behaviour of NiTi wires and strips in order to find the best training cycle to achieve a good compromise between transformation temperatures, recovery forces and phase reversibility. Other parameters such as the stress-rate and maximum recovery deformations, useful to realize smart composites, were evaluated. DSC and DMTA analyses were performed on NiTi thin strips that were cold rolled with different thickness reductions. DSC is a well-known technique used to find the transformation temperatures of SMAs. Contrary to DSC, DMTA is not a traditional characterization method for shape memory alloys. Therefore, in this work I tried to find a correlation between the results of DSC and DMTA analysis, according to different hardenings induced by cold rolling. In the second part I dealt with the interface bonding optimization between polymer matrices and NiTi wires. Smart composites take advantage of the adhesion between the NiTi wires and the polymer matrix. Their mechanical properties depend strongly on the efficiency of stresses and deformations transfer at the interface between the wires and the surrounding matrix. This way, adhesion must be improved to avoid the degradation or premature failure of the actuation. I focused on the evaluation of the interface strength between NiTi wires and two kinds of thermosetting resins: polyester and vinylester. Different surface treatments were performed on the NiTi wires in order to increase the performance of the wire-resin interface adhesion. In particular, chemical passivation by using acid solution and functionalization by using silane coupling agents, were considered. Pull-out tests were carried out to quantify the improvement of the interface adhesion. Moreover, during my PhD I also dealt with the theoretical modeling of SMA materials and the mechanical behavior of smart composites during activation, but this topic is not discussed in this thesis

A Simulation Method for Design and Development of Magnetic Shape Memory Actuators

The systems/products and their design processes have become more and more complicated due to the fact that their requirements in terms of function, durability, reliability and energy efficiency have been increased significantly and that their leading time has to be short and their materials cost has to be low. To meet these requirements, individual parts and subsystems have to offer increased functionality and efficiency themselves. It has been found that smart materials, such as piezo ceramics or various shape memory alloys as well as less known dielectric elastomers or magnetic shape memory alloys, offer ideal preconditions to fulfil such requirements. Among the various shape memory alloys, the Magnetic Shape Memory (MSM) alloy is a kind of smart material that can elongate and contract in a magnetic field. Based on the MSM alloy a new type of smart electromagnetic actuators have been designed and developed. This kind of actuator exhibits the features above. Typically, the MSM material is a monocrystalline Ni-Mn-Ga alloy, which has the ability to change its size or shape very fast and many million times repeatedly. State-of-the-art alloys are able to achieve a magnetic field induced strain of up to 12%. The magneto-mechanical characteristic of MSM alloys is being constantly improved. However, as far as the author is aware, there are no efficient and commercially available tools for engineers to design MSM-based actuators. To achieve this, simulation tools for design are indispensable. This thesis is dedicated to this task. In this PhD thesis, new design and simulation techniques for MSM-based actuators have been studied. In particular, three simulation methods have been proposed. These three methods extend standard magneto-static FEM simulation techniques by taking into account the magneto-mechanical coupling and the magnetic anisotropy of the MSM materials. They differ in terms of the necessary a priori alloy characterisation (i.e., measurement effort), computational complexity and consequent computing time. The magneto-mechanical characteristics of the MSM material are a necessary and fundamental ingredient for this type of simulation. However, the characterisation of the MSM materials is a very challenging task and requires specific modifications to standard measurement approaches. So, in this thesis, some specific measurement methods of the magneto-mechanical characteristics of the MSM materials have been proposed, designed and developed. It is described how existing measurement instruments can be modified to measure the unique magneto-mechanical characteristics of MSM, so they are applicable and with practical values. Various tests have been carried out to validate the new methods and the necessary characterisations of the properties of MSM materials have been performed, such as the measurement of the permeability of MSM under a defined stress during elongation. The new measurement results have been analysed and the findings have been used to design and develop the simulation methods. The three simulation methods can be used to predict and optimise the current-elongation behaviour of an MSM element under the load of a mechanical stress while excited by a magnetic field. Extensive experiments have been carried out to validate these three simulation methods. The results show that the three methods are relatively simple but, at the same time, very effective means to model, predict and optimise the properties of an MSM actuator using finite element tools. In addition, the experiment results have also shown that the simulation methods can be used to gain some deep insights into the magneto-mechanical interaction between the MSM element and the electromagnetic actuator. In this thesis an evolutionary algorithm which works together with the simulation methods has been developed to achieve individual optimised solutions in very short times. In summary, from the experiment results, it has been found that the measurements and simulation methods proposed and developed in this thesis; enable designers to perform simulations for a high-quality actuator design based on the magneto-mechanical properties of MSM alloys. This is the first time that a MSM can be characterised for simulation purposes in a fast and precise way to predict MSM and electromagnetic actuator interactions and identify and optimise the design parameters of such actuators. However, these simulation methods are strongly dependent on the measurement of the magneto-mechanical characteristics of magnetic shape memory alloys, whose precision can be further improved. To reach commercial success as well higher precision in the simulation prediction, further achievements in the field of material science (e.g. smoothness of mechanical curves) are also necessary

Simultaneous use of shape memory alloys and permanent magnets in multistable smart structures for morphing aircraft applications

This Thesis considers the simultaneous use of shape memory alloys and permanent magnets for achieving multistable smart structures aiming towards morphing applications. Motivation for this approach lies in the poor energetic efficiency of shape memory alloys, which can void system-level benefits provided by morphing technologies. Multistability can therefore be adopted to prevent continuous operation of shape memory alloy actuators. Objectives of the study involve the combination of shape memory alloys and permanent magnets in new geometrical arrangements to achieve multistable behavior; the development of a numerical modeling procedure that is able to simulate the multi-physics nature of the studied systems; and the proposal of a geometric arrangement for morphing applications that is based on a repeating pattern of unit cells which incorporate the combined use of shape memory alloy wires and permanent magnets for multistability. The proposed modeling strategy considers a geometrically nonlinear beam finite element; a thermo-mechanical constitutive behavior for shapememoryalloys;theinteractionofcuboidalpermanentmagnetswitharbitraryorienta- tions; and node-to-element contact. Experiments are performed with three distinct systems, including a proof-of-concept beam, a three cell morphing beam metastructure, and a morphing airfoil prototype with six unit cells. Results show that the combination of shape memory alloys and permanent magnets indeed allows for multistable behavior. Furthermore, the dis- tributedactuationcapabilitiesofthe morphingmetastructureallowforsmoothandlocalized geometrical shape changes.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCNPq - Conselho Nacional de Desenvolvimento Científico e TecnológicoTese (Doutorado)Esta Tese considera o uso simultâneo de ligas com memória de forma e ímãs permanentes para a obtenção de estruturas inteligentes multiestáveis, com vistas a sua aplicação em aeronaves de geometria variável. A motivação para tal abordagem reside na baixa eficiência energética associada às ligas com memória de forma, a qual pode eliminar benefícios oriundos de tecnologias relacionadas a geometria variável. Multiestabilidade pode, desta forma, ser adotada para prevenir operação contínua de atuadores baseados em ligas com memória de forma. Objetivos do estudo envolvem a combinação de ligas com memória de forma e ímãs permanentes em novos arranjos geométricos para a obtenção de comportamento multiestável; o desenvolvimento de um procedimento de modelagem numérica que pode simular a natureza multifísica dos sistemas estudados; e a proposição de um arranjo geométrico para aplicações que envolvem geometria variável, o qual é baseado num padrão repetitivo de células unitárias que incorporam o uso combinado de ligas com memória de forma e ímãs permanentes para mul- tiestabilidade. A estratégia de modelagem proposta considera um elemento finito de viga com não-linearidades geométricas; um modelo constitutivo termomecânico para ligas com memória de forma; a interação entre ímãs permanentes cúbicos com orientação arbitrária; e contato entre elemento-e-nó no contexto de elementos finitos. Experimentos são realizados com três sistemas distintos, incluindo uma viga para prova de conceito, uma metaestrutura do tipo viga com geometria variável composta por três células unitárias, e um protótipo de aerofólio com geometria variável composto por seis células unitárias. Resultados mostram que a combinação de ligas com memória de forma e ímãs permanentes permite a obtenção de comportamento multiestável. Além disso, a característica de atuação distribuída das metaestruturas com geometria variável permite alterações de forma suaves e localizadas

Development of novel micropneumatic grippers for biomanipulation

Microbjects with dimensions from 1 μm to 1 mm have been developed recently for different aspects and purposes. Consequently, the development of handling and manipulation tools to fulfil this need is urgently required. Micromanipulation techniques could be generally categorized according to their actuation method such as electrostatic, thermal, shape memory alloy, piezoelectric, magnetic, and fluidic actuation. Each of which has its advantage and disadvantage. The fluidic actuation has been overlooked in MEMS despite its satisfactory output in the micro-scale. This thesis presents different families of pneumatically driven, low cost, compatible with biological environment, scalable, and controllable microgrippers. The first family demonstrated a polymeric microgripper that was laser cut and actuated pneumatically. It was tested to manipulate microparticles down to 200 microns. To overcome the assembly challenges that arise in this family, the second family was proposed. The second family was a micro-cantilever based microgripper, where the device was assembled layer by layer to form a 3D structure. The microcantilevers were fabricated using photo-etching technique, and demonstrated the applicability to manipulate micro-particles down to 200 microns using automated pick-and-place procedure. In addition, this family was used as a tactile-detector as well. Due to the angular gripping scheme followed by the above mentioned families, gripping smaller objects becomes a challenging task. A third family following a parallel gripping scheme was proposed allowing the gripping of smaller objects to be visible. It comprises a compliant structure microgripper actuated pneumatically and fabricated using picosecond laser technology, and demonstrated the capability of gripping microobject as small as 100 μm microbeads. An FEA modelling was employed to validate the experimental and analytical results, and excellent matching was achieved

Issues in the design of shape memory alloy actuators

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002."June 2002."Includes bibliographical references (p. 93-96).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.This thesis considers the application of shape memory alloy (SMA) actuators for shape control of the undertray of a sports car. By deforming the shape of the structure that provides aerodynamic stability to the car, we expect to improve the overall performance of the vehicle by adapting its aerodynamics according to the vehicle speed. We then develop a methodology for designing SMA actuators in this application. The methodology is based on the integration of the different models involved: mechanical, thermal, and electrical. The constraints imposed on the device are also incorporated. Unfortunately, the analysis predicts an actuation time that is too slow for this particular application. Still, we use our assembled model to sketch the expected characteristics of SMA actuators. A significant result is that the actuation time is a function of the amount of energy the active material has to provide, and that there is a necessary trade-off between the mass of actuators and the actuation time. In particular, the expected energy density may have to be decreased to achieve acceptable actuation times. Finally, we propose a way to estimate a priori the suitability of SMA actuators for a particular application.by Stéphane Lederlé.S.M

Influence of alloying elements and aging treatment on the phase transformation and shape memory behavior of Cu-Al-Ni shape memory alloys

Nickel-Titanium (Ni-Ti) shape memory alloys (SMAs) have been used in many engineering and medical applications. However, their use is limited, due to their low transformation temperatures, difficulties in processing and high cost of the raw materials. As an alternative material to Ni-Ti alloys, copper-based alloys are successfully being used. Among copper-based SMAs, Cu-Al-Ni alloys are used in a wide range of applications, particularly if high temperatures are required. However, Cu-Al-Ni SMAs also have limitations such as very low ductility and low shape recovery strain. Therefore, this research aims to enhance the ductility and shape memory effect of Cu-Ni-Al by alloying additions and aging heat treatment. The base metal, Cu-Al-Ni, was cast without and with different amounts of the fourth alloying elements, namely, titanium (Ti), manganese (Mn) and cobalt (Co). The modified and unmodified alloys were homogenized and aged at 373 K, 423 K and 523 K for 24 and 48 hours. Phase transformation and microstructural changes were characterized using techniques such as optical microscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), differential scanning calorimetry (DSC), x-ray diffractometry (XRD) and transmission electron microscopy (TEM). The tensile properties and hardness were determined using a universal Instron tensile machine and Vicker‟s hardness test machine, respectively. The shape memory test was performed using a specially designed tensile machine equipped with a heating tape. The results revealed that the alloying elements and aging treatment were found to control the phase morphology, orientations and grain size along with the formation of precipitates, thereby improving the shape memory characteristics, ductility and hardness. The volume fraction, size and distribution of the precipitates are mainly dependent on the type and amount of alloying element as well as the condition of aging treatment. The Cu-Al-Ni with the addition of 0.76 wt. % Ti and age treated showed complete recovery after the shape memory test. This may be attributed to the high volume of X-phase precipitates and grain refinement that led to the restricted mobility of martensite variant interfaces and dislocations. It was found that the alloy with 1.14 wt. % of Co gave the best overall improvement in terms of the transformation temperatures, ductility and shape memory recovery. These improvements were mainly due to the exceptionally high content of the gamma-2 (γ2) phase in the microstructures of the modified alloy. Furthermore, the ductility of the Cu-Al-Ni SMAs increased from 1.65 to 7.0 % when 1.14 wt. % Co was added and the alloy undergone aging treatment where the fracture surfaces showed more ductile features and less brittle cleavages. It was also found that Cu-Al-Ni SMAs with 1.14 wt. % Co obtained full shape recovery after being aged at 523 K for 48 hours

Extended Skin: Designing Interactive Content for Ubiquitous Computing Materials

Current research is inspired by the impact of digital media on disciplinary division. Sim- ultaneously, recognizes the difficulty of engineering (applied science) to consider the humani- ties as fundamental contributors in the process of making. Steaming from a design perspective, the intersection between art (design) and science, questions if these relations can open per- spectives on the matter of designing within a U.C. context, and fundamentally, introduces the question on how this can be done Furthermore, the motivation for this research arises from considering that innovation in technology is happening in the fields typically identified as engineering. And, despite this, the in-corporation of these inventions in life, considering some discussed exceptions, has not typ- ically been present in the concerns of design action and methods. Therefore, the challenge of current research is to contribute to the realm of ubiquitous computing, routed by design, to some degree aiming to contribute to the field. A deeper analysis into the subject of U.C., there is the realization that there is minority presence of the humanities in the discussion of U.C. (Dourish and Bell, 2011). Technological disruption offers continuous inspiration for design innovation within U.C. Furthermore, the inquiry labeled as “material turn” contextualizes a dialogue between nano- technology and traditional materials. Nanotechnology is applied to project development, while considering a human centred design approach. This focus is present throughout this disserta- tion. The research proposal describes SuberSkin, as a responsive surface that works as a screen. The exploration of aesthetical effects is focused on visual properties – using high con- trast between natural cork colors, dark and light brown. The proposal is highly experimental, and ultimately, aims to explore potential routes on cork research, linked to that of U.C. Thus, recreating and transforming this material into an intelligent surface. In sum, this thesis discusses displacement of disciplines suggested as having a positive impact in interdisciplinary thought and for future design. Therefore a methodology, "research through techne" is presented that illustrates this intention.A presente pesquisa é inspirada pelo impacto exercido pelos media digitais na divisão disciplinar. Simultaneamente, reconhece a dificuldade da engenharia (ciência aplicada) em considerar as humanidades como contribuintes fundamentais no processo de fazer. Partindo de uma perspectiva de design e da interseção entre arte (design) e ciência, questiona-se se essas relações poderão abrir perspectivas na criação no âmbito da Computação Ubíqua. Fun- damentalmente, introduz a questão de como poderá ser feito. A motivação para esta pesquisa decorre de considerar que a inovação tecnológica acontece nas áreas normalmente identificadas como engenharia. E, apesar disso, a incor- poração dessas invenções na vida, considerando as exceções discutidas, normalmente não está presente nas preocupações, ação e métodos de design. Portanto, o desafio da pesquisa é con- tribuir para o domínio da Computação Ubíqua, orientada pelo design. Uma análise mais pro- funda sobre o tema da Computação Ubiqua, constata que há na sua discussão uma presença minoritária das humanidades (Dourish e Bell, 2011). A disrupção tecnológica oferece inspiração contínua para inovação de design, e o mesmo se aplica no âmbito da Computação Ubíqua. Além disso, a pesquisa intitulada como “material turn” contextualiza um diálogo entre a nanotecnologia e os materiais tradicionais. A nanotecnologia é aplicada ao desenvolvimento de projetos, considerando uma abordagem de design centrada no ser humano. Este foco está presente ao longo desta dissertação. O projecto de pesquisa descreve SuberSkin, uma superfície responsiva. A exploração centra-se nos efeitos estéticos da cortiça, recorrendo a um contraste entre as suas cores natu- rais: castanho escuro e claro. A proposta é experimental e, em última análise, visa explorar potenciais linhas de investigação ligando a cortiça à Computação Ubíqua. E assim, recriar e transformar este material numa superfície inteligente. Em suma, esta tese discute o deslocamento disciplinar como tendo um impacto posi- tivo no pensamento interdisciplinar e no futuro da prática do design. Consequentemente, apresenta uma metodologia, "investigação através da techne" que a exemplifica

Advanced Multifunctional Corrosion Protective Coating Systems for Light-Weight Aircraft Alloys—Actual Trends and Challenges

The present chapter is devoted to the recent trends in the field of the advanced corrosion protective layers elaboration. The chapter begins with brief classification of the standard aluminum alloys, remarking their importance for the transport sector, as well as the basic corrosion forms, typical for these alloys. It continues with the basic requirements regarding the elaboration of durable and reliable coating systems and the factors of detrimental effect during the service life time. The concept for passive and active corrosion protection capabilities is remarked as well. After description of the need for multilayered coating systems elaboration, the function of each layer is described beginning from (i) UV light–absorbing exterior layers, (ii) self-repairing reinforced intermediate barrier layers, and (iii) cerium oxide primer layers (CeOPL). The importance and the basic approaches for metallic alloy preliminary treatment are remarked, as well. Finally, the basic concepts and the function of each layer in advanced multilayered coating system are summarized in a special section. The chapter finishes with brief conceptual description of two advanced versatile technological synthesis methods, which enable elaboration of organic/inorganic hybrid polymers and reinforcing nanoparticles