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Korozijsko ponašanje legure CuAlNi u 0,5 mol dm-3 H2SO4 otopini otopini ispitano je elektrokemijskim metodama kao što su mjerenje potencijala otvorenog strujnog kruga, linearna i potenciodinamička polarizacija i ciklička voltametrija. Ispitivanja su provedena u deaeriranoj 0,5 mol dm-3 H2SO4 pri temperaturama elektrolita od 20 i 40 stupnjeva C. Nakon polarizacijskih ispitivanja površine elektroda ispitane su svjetlosnim i elektronskim mikroskopom dok je elementarni sastav u pojedinim točkama površine odreĎen EDS analizom. Ispitivanjem se utvrdilo da u H2SO4 otopini dolazi do interkristalne korozije CuAlNi legure čiji intenzitet raste s povećanjem temperature elektrolita. The corrosion behavior of CuAlNi alloy in 0,5 mol dm-3 H2SO4 solution was examined by electrochemical methods such as open circuit potential measurement, linear and potentiodynamic polarization, and cyclic voltammetry. Investigations were performed in deaerated 0,5 mol dm-3 H2SO4 at electrolyte temperatures 20 and 40 degrees C. After polarization testing, the electrode surfaces were examined by light and electron microscope, while the elemental composition at individual points of the alloy surface was determined by EDS analysis. Investigations have shown that in H2SO4 solution an intercrystalline corrosion of CuAlNi alloy occurred whose intensity increases with increasing electrolyte temperature.

U radu je provedeno ispitivanje korozijskog ponašanja traka legure CuAlMn (Al 10,4%, Mn 7,4%) koje su dobivene metodom brzog hlađenja (engl. melt spinning method) u 0,9% NaCl otopini deaeriranoj s Ar (pH = 7,4) na temperaturama od 10 o C, 24 o C, i 50 o C. Mjerenja su provedena elektrokemijskim metodama kao što su mjerenje potencijala otvorenog strujnog kruga, metodom linearne polarizacije te potenciodinamičke polarizacije. Korodirane površine elektroda pregledane su optičkim mikroskopom te je na njima provedena SEM/EDS analiza. Rezultati elektrokemijskih ispitivanja su pokazali da povišenjem temperature elektrolita dolazi do porasta gustoće korozijske struje i do smanjenja vrijednosti polarizacijskog otpora. Snimke površine optičkim i elektronskim mikroskopom nakon polarizacijskih ispitivanja pokazale su da povećanjem temperature elektrolita dolazi i do većih oštećenja površine. Investigation of corrosion behaviour of CuAlMn alloy ribbons (Al 10.4 wt.%, Mn 7.4 wt.%) made by melt spinning methods in 0.9% NaCl solution deaerated with Ar (pH=7.4) on temperatures of 10 o C, 24 o C, 37 o C, 50 o C was performed. Measurements have been carried out by electrochemical methods such as monitoring the open circuit potential, linear polarization and potentiodynamic polarization method. The corroded surfaces of the electrode were examined by an optical microscope, and a SEM/EDS analysis was performed. The results of the electrochemical investigation have shown that elevation of the electrolytic temperature results in the increase in corrosion current density and decrease in polarization resistance values. Light and electron microscopy surface images after polarization investigation have shown that increase in electrolyte temperature results in higher surface corrosion damages.

Utjecaj toplinske obrade legure CuAlMn na korozijsko ponašanje u 0,1 %, 0,9 % i 1,5 % otopini NaCl ispitan je elektrokemijskim metodama kao što su mjerenje potencijala otvorenog strujnog kruga, metodom linearne i potenciodinamičke polarizacije. Nakon polarizacijskih mjerenja elektrodna površina je ispitana optičkim mikroskopom te je provedena i SEM/EDS analiza. Rezultati ispitivanja su pokazali da toplinski obrađeni uzorci pokazuju nešto pozitivniju vrijednost potencijala u odnosu na lijevani uzorak. Povećanjem koncentracije kloridnih iona dolazi do stabilizacije potencijala pri nešto negativnijim vrijednostima za sve ispitivane uzorke CuAlMn. Gustoća korozijske struje nešto je manja, a polarizacijski otpor veći za toplinski obrađene uzorke u odnosu na uzorak lijevane legure bez toplinske obrade. Na mikroskopskim snimkama površine nakon polarizacijskih mjerenja se može vidjeti hrapava površina elektroda uslijed odvijanja korozijskih procesa. Povećanje koncentracije elektrolita dovodi do povećanja oštećenja površine elektroda. Ispitivanja pretražnom elektronskom mikroskopijom pokazala su da je površina prekrivena isprekidanim slojevima korozijskih produkata, kao i pukotinama i kanalićima koji su nastali njihovim otapanjem. Elementarna analiza površine metodom energetski disperzivne rendgenske spektroskopije pokazala je da se korozijski produkti sastoje od aluminijeva i manganova oksida i klorida čiji se postotak razlikuje u ovisnosti od mjesta na kojoj je provedena analiza. Značajno manji sadržaj bakra na površini nađen je na površini kaljenog uzorka CuAlMn legure u odnosu na površinu uzorka lijevane CuAlMn legure bez toplinske obrade. The influence of heat treatment of CuAlMn alloy on corrosion behavior in 0.1%, 0.9% and 1.5% NaCl solution was studied by electrochemical methods such as measuring the open circuit potential, linear and potentiodynamic polarization. After polarization measurements the electrode surfaces was examined by optical microscope and also with SEM/EDS analysis. The results of the investigations have shown that the heat treated samples have a slightly more positive values of the open circuit potential compared to the as cast sample. Concentration increasing of chloride ions results in potential stabilization at slightly negative values for all CuAlMn alloy samples. Values of the corrosion current density are slightly smaller and the polarization resistance values are higher for the heat treated samples compared to the sample of as cast alloy without heat treatment. The microscopic analysis of the electrode surfaces after the polarization measurements, have show the rough surfaces due to corrosion processes. Increasing the electrolyte concentration leads to an increase in electrode surface damage. Examination by scanning electron microscopy showed that the surface was covered with interlaced layers of corrosion products, as well as cracks and ducts formed by their dissolution. Elemental surface analysis by energy dispersive X-ray spectroscopy showed that corrosive products consist of aluminum and manganese oxides and chlorides, the percentage of which differs depending on the site where the analysis was performed. Significantly lower copper content on the surface was found on the surface of the annealing CuAlMn alloy sample surface relative to the surface of the cast CuAlMn alloy without heat treatment.

Korozijsko ponašanje CuAlMnTi traka dobivenih brzim hlađenjem ispitano je u 0,9% NaCl otopini pri temperaturama10, 24, 37 i 50 o C. Također je ispitan i utjecaj pH vrijednost elektrolita na koroziju traka CuAlMnTi legure u 0,9 % NaCl otopini pH vrijednosti 3,4, 5,4 i 7,4. Mjerenja su provedena elektrokemijskim metodama kao što su praćenje potencijala otvorenog strujnog kruga, metodama linearne i potenciodinamičke polarizacije. Rezultati ispitivanja su pokazali da povećanje temperature elektrolita i sniženje pH vrijednosti dovodi do negativiranja vrijednosti korozijskog potencijala, porasta gustoće korozijske struje i smanjenja vrijednosti polarizacijskog otpora što ukazuje na veći korozijski napad na CuAlMnTi leguru. Na snimkama površine koje su dobivene svjetlosnim mikroskopom vidljiva su oštećenja površine uslijed korozijskog procesa, koja se povećavaju s povišenjem temperature elektrolita i sniženjem pH vrijednosti otopine. Jamičasta korozija vidljiva je nakon polarizacijskog ispitivanja pri 50 o C. SEM snimke su potvrdile negativan utjecaj povišenja temperature i sniženja pH vrijednosti elektrolita na koroziju CuAlMnTi legure. EDS analizom utvrđena je prisutnost svih legirnih elemenata na površini, ali se njihov postotak smanjuje osobito sniženjem pH vrijednosti elektrolita. Bakar i aluminij se najprije otapaju s površine a zatim mangan, dok se postotak Ti značajnije ne mijenja uslijed korozijskih procesa što potvrđuje njegovu izrazitu korozijsku otpornost. The corrosion behavior of CuAlMnTi alloy ribbons obtained by rapid cooling was assayed in 0.9% NaCl solution at temperatures of 10, 24, 37 and 50 o C. The influence of different pH value of electrolyte on corrosion of CuAlMnTi alloy ribbons in 0.9% NaCl (pH = 3.4, 5.4 and 7.4) was also investigated. Measurements were performed by electrochemical methods such as monitoring the open circuit current potential, linear and potentiodynamic polarization methods. The results of the measurements have shown that the increase in temperature of the electrolyte and the decrease of pH value leads to a change of corrosion potential values in negative direction, a rise in corrosion current density values, and a decrease in polarization resistance values, indicating a higher corrosion attack on CuAlMnTi alloy. Surface images obtained by a light microscope show surface damages due to the corrosion process, which are increased by elevation of the electrolyte temperature and by lowering the pH of the solution. Pitting corrosion is visible after a polarization test at 50 o C. Results of SEM investigations confirmed the negative influence of temperature elevation and lower electrolyte pH on CuAlMnTi alloy corrosion. By EDS analysis, the presence of all alloying elements on the surface was determined, but their percentage decreased, especially by lowering the pH of the electrolyte. Copper and aluminum first dissolve from the surface and then manganese, whereas the percentage does not significantly change due to corrosion processes, which confirms its marked corrosion resistance.

Korozijsko ponašanje CuAlNi traka dobivenih naglim hlađenjem ispitano je u 0,9 % NaCl otopini (pH = 7,4) pri temperaturama 24, 37 i 50 o C. Također je ispitan i utjecaj koncentracije kloridnih iona na koroziju traka Cu-Al-Ni u 0,1 % i 1,5 % otopini NaCl. Mjerenja su provedena elektrokemijskim metodama kao što su praćenje potencijala otvorenog strujnog kruga, metodama linearne i potenciodinamičke polarizacije. Rezultati ispitivanja su pokazali da povećanje koncentracije kloridnih iona i temperature elektrolita dovodi do porasta gustoće korozijske struje i smanjenja vrijednosti polarizacijskog otpora što ukazuje na veći korozijski napad na CuAlNi leguru. Mikroskopske snimke su ukazale na značajna oštećenja na površini CuAlNi legure uzrokovana jamičastom korozijom. SEM snimke površine CuAlNi elektroda su potvrdile da s povećanjem koncentracije kloridnih iona dolazi do većeg korozijskog napada. EDS analiza ukazala je na dominantan postotak bakra, klora i kisika na površini što ukazuje na formiranje bakrovih oksida i klorida kao glavnih produkata korozije na površini. Mali postotak aluminija ukazuje na njegovu raspodjelu u obliku aluminijeva oksida i klorida u površinskom sloju. The corrosion behavior of the CuAlNi alloy ribbons obtained by rapid solidification was investigated in 0.9 % NaCl solution (pH 7.4) at temperatures of 24, 37 and 50 o C. The influence of chloride ions concentration on corrosion of CuAlNi ribbons has also been investigated in 0.1% and 1.5% NaCl solution. Measurements have been performed by electrochemical methods such as monitoring the open circuit potential, linear and potentiodynamic polarization methods. Results of the investigations have shown that increase in chloride concentration and electrolyte temperature leads to increase the corrosion current density and decrease the polarization resistance values which mean higher corrosion attack on CuAlNi alloy. Microscopic images have shown significant pitting corrosion damages on the CuAlNi alloy surface. Increasing the electrolyte temperature increases the surface damages of the electrode due to more intense corrosion. SEM surface images of CuAlNi electrodes have confirmed that with elevation of chloride concentration a more intense corrosion attack occurs. EDS surface analysis indicated dominant percentage of copper, chlorine and oxygen on the surface, indicating the formation of copper oxide and chloride as the major corrosion products on the surface. The presence of a small percentage of aluminum indicates its distribution in the form of aluminum oxide and chloride in the surface layer.

Given that most applications of shape memory alloys (SMA) are in the wire form, a reduced order model and analysis has been attempted in this paper. It takes into account the fact that the predominant actions are axial (bending inclusive) and torsional. A thermodynamic framework is first developed to simulate the behaviour of the SMA material under thermo-mechanical loading that is a combination of axial and shear stresses arising at a point in a wire due to axial and torsional loads applied to the wire. Since only a few variants relevant to axial-torsion are going to be active in transformation under this kind of loading, a reduced order model that tracks the evolution of four martensite variants and an austenite variant is proposed. It is shown through simulations that these five model parameters amply form a minimal set of model parameters sufficient for simulating response under tension-torsion loading excursions. The model is further applied to the structural member, in this case, a wire of circular cross-section subject to a twist and an axial extension and the capability of the model to simulate the kind of response expected in wires. Incorporation of this model into a large deformation space frame nonlinear analysis will help in the design and analysis of several applications where SMA wire forms are used. � 2014 IOP Publishing Ltd.

Conference of Conference Smart Sensors, Actuators, and MEMS VI ; Conference Date: 24 April 2013 Through 26 April 2013; Conference Code:98305; International audience; Magnetic shape memory alloy (MSMA) is a relatively new kind of smart material. Upon application of a large magnetic field, it exhibits actuation strains up to 10% similar to thermal shape memory alloy (SMA) but shows significantly reduced response time in the millisecond range. Currently, application is restricted by the brittleness of the single crystal material, its nonlinear behaviour and the difficulty to generate and apply a magnetic field around 0.6T in order to exploit the full actuation potential. The focus of this work is on the design of miniaturized magnetic circuits for bulk MSMAs. Various circuit designs are compared such as toroidal and series-parallel shapes. Equivalent circuit as well as finite element simulation is used to increase the magnetic field in a characteristic air gap where the smart material is placed. A symmetrical toroid coil layout with the MSMA element at the center that allows easy integration of the actuator in various applications is described. Static characterization results of this actuator are provided. Using the described magnetic circuit and 5M - MSMA rods with dimensions of 20x2.5x1mm3 , a peak displacement of 0.8mm and a blocked force of 4.5N was obtained. Further design guidelines for such miniaturized actuators are given.

Apart from biological factors, the bone healing process strongly depends on the mechanical properties of the implant applied. The stiffness of the implant influences the micro-motion, one of the most important stimuli of the healing process within the fracture gap. Both, the “ideal” stiffness of an implant as well as the alteration of the mechanical properties over the course of healing are still a topic of research. Apart from biodegradable implants or “fixateur externe”, it is not possible to alter the mechanical properties of the implants without second surgery. A “stiffness alterable” implant might have a positive impact on the healing process, e.g. a shorter healing time, an early ability to bear weight or the avoidance of a follow-on operation. In order to adapt the implant to the actual healing situation, nickel-titanium (NiTi) shape memory alloy (SMA) based implants that exhibit a variable middle piece were developed. Due to contactless induction heating, the transition temperature of the SMA is reached and triggers the one-way shape memory effect (SME). This leads to a slight modification of the second moment of inertia and to an adaption of the bending stiffness of the implant, respectively. Based on laser cutting and welding, NiTi-SMA based implants were manufactured by using thin, commercially available NiTi (thickness: 0.5 and 1.0 mm, transition temperature Af between 55-65 °C) sheets. Depending on the implant design, 4-Point-Bending measurements showed feasible bending stiffness alterations around a range of 50%, with regard to the original stiffness. Thereby, two approaches, increasing the bending stiffness and decreasing the bending stiffness, have been realized. Currently, the implant design is being adapted in order to meet the requirements for human applications. Custom made NiTi-SMA with a transition temperature around 45-50 °C could continue to reduce the impact of the heating process and expand this concept to further medical applications, e.g. compression, anchoring or expansion of implants or devices.

The main objectives of this research work are: the design and the wind tunnel testing of a controller for a new morphing mechanism using smart materials made of Shape Memory Alloy (SMA) for the actuators, and the aero-elasticity studies for the morphing wing. The finally obtained configuration for the controller is a combination of a bi-positional controller (on-off) and a PI (proportional-integral) controller, due to the two phases (heating and cooling) of the SMA wires' interconnection. Firstly, the controller is used for the open loop development step of a morphing wing project, while, further, it is included as an internal loop in the closed loop architecture of the morphing wing system. In the controller design procedure four step are considered: 1) SMA actuators model numerical simulation for different loading force cases; 2) linear system approximation in the heating and cooling phases using Matlab's System Identification Toolbox and the numerical values obtained in the first step; 3) selecting the controller type and its tuning for each of the two SMA actuators' phases - heating and cooling; and 4) integration of the two controllers just obtained into a single controller. For the controller validation three actions are taken: 1) numerical simulation; 2) bench testing; and 3) wind tunnel testing. For the third part of this study, aeroelastic studies, the purpose is to determine the flutter conditions in order to be avoided during wind tunnel tests. These studies show that aeroelastic instabilities for the morphing configurations considered appears at Mach number 0.55, which is higher than the wind tunnel Mach number limit speed of 0.3. © 2011 by Ruxandra Botez., AIAA Atmospheric Flight Mechanics Conference 2011, 8 August 2011 through 11 August 2011, Portland, OR

The paper presents the numerical and experimental validation of an intelligent controller for a new morphing mechanism using smart materials made of Shape Memory Alloy (SMA) for the actuators. A brief presentation of the finally adopted controller architecture precedes its validation exposure consisting in numerical simulations, experimental bench tests, and wind tunnel tests. The Matlab/Simulink software is used to tune the controller through numerical simulation and after that to be experimentally implemented. In the physical model development, two Programmable Switching Power Supplies AMREL SPS 100-33 and a Quanser Q8 data acquisition card are used. The feedback signals in the control loop are provided by two Linear Variable Differential Transformer potentiometers monitoring the actuators' positions. Also, six thermocouples allow supervising of the SMA wires temperatures. In order to obtain the desired skin deflections, the power supplies are controlled using the acquisition card outputs., IASTED International Conference on Applied Simulation and Modelling, ASM 2011, 22 June 2011 through 24 June 2011, Crete

The paper describes the design phase of an intelligent controller for a new morphing mechanism using smart materials made of Shape Memory Alloy (SMA) for the actuators. After a brief presentation of the morphing wing system, the controller purposes are discussed. The morphing system requirements and the behaviour of SMA actuators lead to a fuzzy logic Proportional-Integral- Derivative for the controller architecture. The output error and the change in error are used as controller inputs, while the electrical current is used as command variable (controller output). In the chosen architecture, the inputs and outputs designed membership functions, and the inference rules allow the control of both cooling and heating SMA phases. In this way, the electrical current given by the controller is approximately 0 A for the cooling phase, and have higher values for the heating phase depending by the values of controller inputs. In the fuzzy logic controller input-output mapping, [-1, 1] interval is chosen as the universe for all inputs signals, while the [0, 2.5] interval is used for output signal. Numerical simulations impose a number of three membership functions for each of the two inputs, three membership functions for the output, and five inference rules. The shapes of the inputs membership functions are s-function, π-function, respectively z-function, while the product fuzzy inference and the center average defuzzifier are applied (Sugeno)., IASTED International Conference on Applied Simulation and Modelling, ASM 2011, 22 June 2011 through 24 June 2011, Crete

The paper presents the design of an intelligent actuation control concept, self-tuning fuzzy logic Proportional-Integral-Derivative plus conventional On-Off, for a new morphing mechanism using smart materials made of Shape Memory Alloy (SMA) for the actuators. In this way, two fuzzy inference systems were developed and implemented in the self-tuning fuzzy logic controller. In the design phase, the input-output mappings of the fuzzy models were designed and a final architecture for the hybrid controller was obtained. The shapes chosen for inputs membership functions of both fuzzy inference systems were s-functions, π-functions, respectively z-functions, while the product fuzzy inference and the center average defuzzifier were applied (Sugeno). The obtained controller was numerically and experimentally implemented using the Matlab/Simulink software. Following preliminary numerical simulations which were conducted to tune the controller, an experimental validation was performed: bench tests and wind tunnel tests. Simultaneously, the aerodynamic part of the morphing wing model was validated: optimized airfoils were experimentally validated with the theoretically-determined airfoils obtained earlier. Also, the transition point real time position detection and visualization were realized in wind tunnel tests. © 2011 by Ruxandra Mihaela Botez. Published by the American Institute of Aeronautics and Astronautics, Inc., AIAA Centennial of Naval Aviation Forum 100 Years of Achievement and Progress"", 21 September 2011 through 22 September 2011, Virginia Beach, VA