Nitinol Shape Memory Alloy Wire Research Articles

Friction testing of tube-guided electrically heated Nitinol shape-memory alloy wires

In this study, a test scenario for the friction testing of electrically heated shape-memory alloy (SMA) wires against polymer surfaces was developed. As alloy, Nickel-Titanium (Nitinol, NiTi) was specially selected due to its high working capacity, the good corrosion resistance and the quick actor response at low bias forces. As the materials in contact with the actuator must resist friction forces and elevated temperatures up to 200 °C, a combination with high performance polymers is preferable. In many applications, the actuators use redirections to enhance the actuator capabilities or enable the use in complex structures. To better understand and compare the tribological properties of Nitinol against various polymer materials, it was needed to manufacture a customized testing device.

Shape Memory Hybrid Composites for Aerospace Applications

Shape memory alloys (SMAs) are smart materials that have the ability to recover large strain. The shape memory and superelasticity in these alloys is due to stress induced martensitic transformation that strongly depends upon the phase transformation temperatures. These alloys are being investigated for a number of applications due to their remarkable properties such as improved impact and damage resistance, vibration damping, seismic damping, shape morphing and crack closure properties. In this work, these alloys were integrated in fiber reinforced polymers (FRPs) to develop hybrid composite structures that can benefit from both fiber strength and intrinsic properties of SMAs resulting in weight efficient smart materials with better mechanical properties. The experimental investigation on impact performance of nitinol SMAs wire reinforced glass fiber composites (GFRP) showed 18% increase in toughness, as compared to steel wire reinforced glass fiber composites. In this paper, the effect of shape memory alloys wires in composite materials and their targeted applications especially for aerospace industry is presented.

Nitinol wire-reinforced GLAREs as a novel impact resistant material: An experimental study

Glass-fiber-reinforced aluminum layers (GLARE) are one of the excellent impact resistant materials, benefited from both the metal and glass fibers properties. Owing to their high impact damping properties, the shape memory alloys have been also considered as useful materials for arming the conventional impact-exposed materials. In the present paper, the shape memory wires were integrated with GLARE laminate and its response to the Charpy low-velocity impact was experimentally studied. The current study is aimed to determine the effects of three parameters (pre-strain percentage of shape memory alloy (SMA), glass fibers angle and the location of SMA wires within the novel fiber metal laminate) for the first time. Hybrid GLARE specimens of this study were planned by Taguchi design of experiments (DOE) method and contained Nitinol shape memory alloy wires. The results showed that the pre-strain and the angle of glass fibers are the most effective parameters on the impact energy absorption at accepted levels of confidence. Regarding the innovations in the construction of this type of impact-resistant hybrid composites, this study could be used in design of aerospace bodies.

Characterization and Behavior Study of Nitinol Shape Memory Alloy Wire for Effective and Efficient Use in Soft Robotics as an Actuator

Soft Robotics is an emerging field due to high degree of freedom, their soft and delicate interaction, almost no vibration during operations etc. are some among many reasons, why scientists and researchers got attracted towards this field. Nitinol is commonly used in soft robotics and easily available Shape Memory Alloy (SMA) actuator. In present investigation, the authors attempted to understand the characteristics and behaviour of Nitinol SMA Actuator wire with change in various parameters such as length, diameter, current, and temperature. Moreover, it is investigated, how resistance, power consumption, force developed, hysteresis, and displacement changing takes place with current passing through the wire and corresponding temperature developed. Various experiments are performed and based on the results and findings related to the selection of wires for specific requirement have been discussed and suggestions were made for the use of the SMA actuator efficiently and effectively.

Electrical and thermal characteristics of nitinol wires for linear heat detectors

In this work were investigated the modifications of electrical and thermal properties that occur with the phase changes (M→A) during heating a Nitinol shape memory alloy wire for using it as a linear heat detector. The investigations were made using three Nitinol wires with different diameters (1; 0.1 and 0.075 mm). For the thermal characterization we used differential scanning calorimetry (DSC Netzsch 200 Maia) using two different heating rates and for resistivity a milliohmmeter (Extech 380560) and a thermocouple. The results were analyzed from the point of sensitivity of the smart element in order to be used as heat variation detector.

Modelling of Tensile Behaviour of NiTinol SMA Wire by Finite Element Analysis

Shape Memory Alloys (SMA) are used in diverse engineering and medical applications capitalizing on their sensing and actuation capabilities. This is attributed to the high magnitude of recovery strain and recovery stress that they are capable of generating. But shape memory alloys exhibit complex behaviour in the presence of electrical and magnetic fields as well as mechanical stress. Their behaviour in these domains is to be rightly and comprehensively understood if these are to be used in these applications. Over the years finite element analysis has proved to be a powerful tool for studying the behaviour of SMAs under different conditions and has therefore been applied in many important applications. In this paper an attempt has therefore been made to understand the behaviour of an equiatomic NiTi alloy wire under mechanical stress by finite element analysis using commercially available software MSC Marc.Simulation of an SMA wire with 0.5 mm diameter and 351 mm length was carried out in uniaxial tension by finite element analysis. The simulation involves three stages: geometric modelling using the software MSC.Patran. Finite element modelling also uses the same software, and finally arriving at the solution using the software MSC.Marc.The finte element model is created by meshing the geometric model using Element type Tetmesh4. Boundary conditions are then applied using MSC Mentat software followed by arriving at the solution using Auricchio model. The stress-strain behaviour of the equiatomic NiTinol wire under simple uniaxial tensile loading at different temperatures was simulated.

Determination of Transformation Temperatures of SMAs by Varying the Force Using Dead Weight Method

Shape-memory material is an alloy that “Remembers” its original shape and that when deformed to its Pre-deformed shape when heated. Phase transformation temperature is one of the most important parameters for the shape memory alloys. In this present work phase transformation temperature is measured by the dead weight method and compared with standard Differential scanning calorimetry (DSC) method. The objective of this paper is to study the microstructure of the Shape memory alloy (SMA) wire, determining the Phase Transformation temperature of NiTinol alloy i.e. Marteniste start (Ms), Martensite finish (Mf), Austenite Start (As), Austenite finish (Af) by a Dead Weight method and also studying the stress-strain behavior with variation of Temperatures to show the Shape memory effect in the NiTinol SMA wire.

Effect of Variation in Applied Force on Transformation Temperatures of NiTinol SMAs

Shape Memory Alloys (SMA) are promising materials for actuation in space applications, because of the relatively large deformations and forces that they offer. However, their complex behaviour and interaction of several physical domains (Electrical, Thermal and Mechanical), the study of SMA behaviour is a challenging field. Phase transformation temperature is one of the most important parameters for the shape memory alloys (SMAs). In this present work, a novel method of determining transformation temperatures is carried out which uses dead weight. The SMA NiTinol wire was applied with force and maintained constant throughout the experiment and at the same time it was heated up slowly until a temperature of approximately 80°C with direct current. The direct current was then slowly decreased to cool down the temperature of the NiTinol wire. All the phase transformation temperatures for NiTinol SMA wire were obtained. A variation in transformation temperatures are recorded with variation in applied force, which is an important aspect calls for attention before using the material in any application. In the present work, it has been investigated and reported in detail.

Validation of Nitinol SMA Characteristics Using Finite Element Analysis and Closed Form Solutions

Shape Memory Alloys (SMA) are promising materials for actuation in space applications, because of the relatively large deformations and forces that they offer. However, their complex behaviour and interaction of several physical domains (electrical, thermal and mechanical), the study of SMA behaviour is a challenging field. Present work aims at correlating the Finite Element (FE) analysis of SMA with closed form solutions and experimental data. Though sufficient literature is available on closed form solution of SMA, not much detail is available on the Finite element Analysis. In the present work an attempt is made for characterization of SMA through solving the governing equations by established closed form solution, and finally correlating FE results with these data. Extensive experiments were conducted on 0.3mm diameter NiTinol SMA wire at various temperatures and stress conditions and these results were compared with FE analysis conducted using MSC.Marc. A comparison of results from finite element analysis with the experimental data exhibits fairly good agreement.

607 ニチノール形状記憶合金極細線の応力ひずみ挙動(機械材料とシミュレーションII)

607 ニチノール形状記憶合金極細線の応力ひずみ挙動(機械材料とシミュレーションII)

Development of Composite Optical Bench Structures on a Satellite Considering Launch and Space Environments

Satellite structural components must be able to withstand various loading and environments that will experience during integration, tests, transportation, launch, and on-orbit operation. A polymeric composite optical bench that fixes delicate optical payloads such as a camera or a telescope was developed based on static strength, thermal deformation, and vibration. The optical bench consists of composite sandwich panels with and without a hole and composite struts with end fittings. In this paper, the optimum stacking sequence of the composite optical bench was calculated to minimize severe thermal deformations during orbital operation using a genetic algorithm and the finite element analysis. Then, the optimum design is evaluated whether it withstands launch loads (high inertia, vibration, etc.), that are not usually significant compared to orbital thermal loadings, or not. The thermal deformation of sandwich panels was minimized at the stacking sequence of [0/±45]s and that of composite struts was lowest at the angle of [02/90]s. There was no buckling in the compressive loading. By vibration analysis, the natural frequencies of the composite components were much higher than aluminum structures (i.e., sandwich panel: 10.7%; strut: 27.79%) and the stiffness condition expected was satisfied. Then, a composite optical bench was fabricated for tests and all analyses results were verified by structural testing. There were good correlations between two results. To increase the structural stiffness, several Nitinol shape memory alloy wires installed on it and the natural frequencies were measured.

Feedback Control Using Shape Memory Alloy Actuators

Shape memory alloy (SMA) has been considered as an actuator for applications that require large force and displacement. Two factors have hampered the usefulness of such actuators: a hysteretic input-output relation and bandwidth limitations. This paper considers the hysteresis phenomenon from a control point of view. Instead of directly compensating for the hysteresis, which requires an accurate model, we use a closed loop approach which considers the feedback control of the beam strain. A simple lumped temperature and SMA force/displacement model is used for stability analysis. We show that with the SMA wire fixed between rigid surfaces, a proportional force feedback would render the closed loop stable. However, when SMA is coupled to a flexible structure, the resulting system can exhibit instability. We then show that a proportional position feedback is stabilizing, but there would be steady-state error. An adaptation scheme can be further added to remove the steady-state error. The analysis is verified experimentally in a simple experimental setup consisting of a flexible aluminum beam and a Nitinol shape memory alloy wire that applies a bending force to the end of the beam.

Preisach modeling of piezoceramic and shape memory alloy hysteresis

Smart materials such as piezoceramics, magnetostrictive materials, and shape memory alloys exhibit hysteresis, and the larger the input signal the larger the effect. Hysteresis can lead to unwanted harmonics, inaccuracy in open loop control, and instability in closed loop control. The Preisach independent domain hysteresis model has been shown to capture the major features of hysteresis arising in ferromagnetic materials. Noting the similarity between the microscopic domain kinematics that generate static hysteresis effects in ferromagnetics, piezoceramics, and shape memory alloys (SMAs), we apply the Preisach model for the hysteresis in piezoceramic and shape memory alloy materials. This paper reviews the basic properties of the Preisach model, discusses control-theoretic issues such as identification, simulation, and inversion, and presents experimental results for piezoceramic sheet actuators bonded to a flexible aluminum beam, and a Nitinol SMA wire muscle that applies a bending force to the end of a beam.

Development of computer assisted orthosis design and manufacturing system for malformed ears.

Most cases of malformed ears in neonates can be treated by mounting a suitably shaped orthosis. Our objective was to develop a computer-assisted orthosis design and manufacturing system for the treatment of malformed ears. Also, we aimed to manufacture a first experimental orthosis made of nitinol shape-memory alloy wire. First, the target posttherapeutic auricular shape is input from computed tomography scans, and characteristic points and contours are extracted. The shape of the orthosis is then created by tracing the necessary contours automatically. Finally, the orthosis shape data are projected onto one or more approximate planes and autoconverted into numerical control (NC) data for plate groove processing. The nitinol shape-memory alloy wires are inserted in the groove and the shape is memorized by heat treatment. The shape of the manufactured orthosis can be memorized from the generated NC data within 1.0 mm of error. Stahl's ear in a 9-month-old baby was treated 7 months ago by mounting the orthosis manufactured by the system. The developed system allows the design and manufacture of orthoses made of nitinol shape-memory alloy wire for the treatment of malformed ears.

Development of Computer Assisted Orthosis Design and Manufacturing System for Malformed Ears

Most cases of malformed ears in neonates can be treated by mounting a suitably-shaped orthosis. Our objective was to develop a computer-assisted orthosis design and manufacturing system for the treatment of malformed ears. Also, we aimed to manufacture a first experimental orthosis made of nitinol shape-memory alloy wire. First, the target posttherapeutic auricular shape is input from computed tomography scans, and characteristic points and contours are extracted. The shape of the orthosis is then created by tracing the necessary contours automatically. Finally, the orthosis shape data are projected onto one or more approximate planes and autoconverted into numerical control (NC) data for plate groove processing. The nitinol shape-memory alloy wires are inserted in the groove and the shape is memorized by heat treatment.The shape of the manufactured orthosis can be memorized from the generated NC data within 1.0 mm of error. Stahl's ear in a 9-month-old baby was treated 7 months ago by mounting the orthosis manufactured by the system. The developed system allows the design and manufacture of orthoses made of nitinol shape-memory alloy wire for the treatment of malformed ears.