Embedded Shape Memory Alloy Research Articles

Vibration analysis of a beam with embedded shape memory alloy wires

In this study, analytical relations for evaluating the exact solution of natural frequency and mode shape of beams with embedded shape memory alloy (SMA) wires are presented. Beams are modeled according to Euler-Bernoulli, Timoshenko and third order beam (Reddy) theories. A relation is obtained for determining the effect of axial load generated by the recovery action of pre-strained SMA wires. By defining some dimensionless quantities, the effect of different mechanical properties on the frequencies and mode shapes of the system are carefully examined. The effect of axial load generated by SMA wires with buckling load and frequency jump is accurately studied.

The post-buckling behavior of the composite plates with embedded shape memory alloy subjected to combined loading using finite element method

Thin composite structures that are used in aerospace applications can be subjected to buckling failure due to combined mechanical and thermal loadings. This paper presents the work on the thermal post-buckling improvement of composite plates previously subjected to mechanical loading. Pre-strained shape memory alloy wires were embedded within laminated composite plate so that the recovery stress that can improve strain energy of the plate can be induced when the wires were heated. A geometric non-linear finite element formulation of the shape memory alloy composite plate and its source codes were developed. The formulation is based on total strain for the case of mechanical loading and incremental strain for the case of thermal loading. Using the codes, post-buckling paths were determined for quasi-isotropic and anti-symmetric cross-ply composite plates. It was found that by embedding shape memory alloy wires within composite plates, thermal post-buckling paths can be improved significantly even after the degradation of the thermal buckling resistance of composite plates due to the application of the mechanical loading.

Design and fabrication of a bat-inspired flapping-flight platform using shape memory alloy muscles and joints

This work focuses on the development of a concept for a micro-air vehicle (MAV) based on a bio-inspired flapping motion that is generated from integrated smart materials. Since many smart materials have their own biomimetic characteristics and the potential to be highly efficient, lightweight, and streamlined, they are ideal candidates for use in structural or actuator components in MAVs. In this work, shape memory alloy (SMA) actuator wires are used as analogs for biological muscles, and super-elastic SMAs are implemented as flexible joints capable of large bending angles. While biological organisms have an intrinsic sensing array composed of nerves, the SMA wires also provide self-sensing by virtue of a phase-dependent resistance change. Study of the biology and flight characteristics of natural fliers concluded that the bat provides an ideal platform for SMA muscle wires because of its comparatively low wingbeat frequency and superb maneuverability. A first-generation prototype is built to further the understanding of fabricating Nature’s designs. The engineering design is then improved further in a second-generation prototype that combines 3D printing and new techniques for embedding SMA wires and shaping SMA joints for improved robustness, reproducibility, and lifetime. These prototypes are on display at the North Carolina Museum of Natural Science’s Nature Research Center, which has the goal of bridging the gaps between biology and engineering.

Numerical simulation and verification of a curved morphing composite structure with embedded shape memory alloy wire actuators

Shape memory alloys have been actively studied in various fields in an attempt to utilize their high energy density. In particular, shape memory alloy wire-embedded composites can be used as load-bearing smart actuators without any additional manipulation, in which they act like a hinge joint. A shape memory alloy wire-embedded composite is able to generate various deformation behaviors via the combination of its shape memory alloy and matrix materials. Accordingly, a study of the various design parameters of shape memory alloy wire-embedded composites is required to facilitate the practical application of smart structures. In this research, a numerical simulation of a shape memory alloy wire-embedded composite is used to investigate the deformation behavior of a composite panel as a function of the composite width per shape memory alloy wire, composite thickness, and the eccentricity of the shape memory alloy wire. A curved morphing composite structure is fabricated to confirm the results of the numerical simulation. The deformation of the shape memory alloy wire-embedded composite panel is determined by measuring its radius of curvature. The simulated deformation behaviors are verified with the experimental results. In addition, an analysis of the deformation and internal stress of the composites is carried out. It can be used to obtain guidelines for the mechanical design of shape memory alloy wire-embedded composite panels.

Effect of Shape Memory Alloy Wires on Natural Frequency of Plates

In last decades, smart materials have developed extensively, and have become an important topic for re- searchers in different areas. SMA is a good candidate for active control of the smart composite structures. In this study, numerical-based analysis for evaluating the natural frequencies and mode shapes of the plate with embedded shape memory alloy wires are presented. Plates are modelled in according to classical plate theory (CPT) as well as first-order shear de- formation plate theory (FSDT). Also, SMA wires are modelled as a beam. The effect of axial load generated by SMA wires due the change of temperature on the natural frequencies is accurately studied.

Multifunctional SMArt composite material for in situ NDT/SHM and de-icing

The past few decades have seen significant growth in the development and application of multifunctional media for the enhancement of material properties, thermo-mechanical and sensing properties. This research work reports a novel approach in which a multifunctional material, herein referred to as SMArt composite, can be employed as a structural health monitoring system for strain sensing and damage detection (SMArt sensing and SMArt thermography), but also as an embedded ice protection tool for structural applications (referred as SMArt de-icing). Such a material, obtained by embedding shape memory alloy (SMA) wires within traditional carbon reinforced plastic composites, relies on the possibility of using the wires both to increase the mechanical properties of composites panels and to exploit their intrinsic electrothermal properties. The electrical resistance variation and the internal power resistive heating source provided by the SMA network, enable a built in and fast assessment of the strain distribution and in situ damage visualization via thermographic imaging. The efficiency of these techniques was experimentally validated on a number of SMArt composite laminates with single and multiple internal defects at various depths. The results showed that strain sensing and damage detection were achieved with high spatial resolution and accuracy, without the need to use large external heaters or complex signal processing techniques.

Aeroelastic characteristics of cantilever wing with embedded shape memory alloys

In this paper, the effect of embedded shape memory alloy (SMA) wires on the natural frequency, flutter, limit cycle oscillation (LCO) amplitude and aeroelastic stability margin of a rectangular cantilever wing are investigated. Wings are modeled in accordance to classical plate theory (CPT) as well as first-order shear deformation plate theory (FSDT) and large deflection Von Karman plate theory. The effects of pre-strain, temperature and number of SMA wires on aeroelastic characteristics are considered. Significant improvements in aeroelastic behaviors due to the in-plane load of the SMA wires are obtained.

Bending analysis of soft core sandwich plates with embedded shape memory alloy wires using three-dimensional finite element method

In this article, bending behavior of the sandwich plates with embedded shape memory alloy wires in their face sheets is studied. Three-dimensional finite element method is used for constructing and analyzing the sandwich plates with flexible core and two stiff face sheets. Some important points such as continuity conditions of the displacements, satisfaction of inter-laminar transverse shear stresses, conditions of zero transverse shear stresses on the upper and lower surfaces and in-plane and transverse flexibility of the soft core are considered for the accurate modeling of the sandwich plate. Solutions for bending analysis of shape memory alloy wire-reinforced sandwich plates under various transverse loads are presented and the effects of plate dimensions, shape memory alloy wires diameter, boundary conditions and shape memory alloy wires embedding positions are studied. Comparison of the present results in special case with those of the three-dimensional theory of elasticity and some plate theories confirms the accuracy of the proposed model. According to the obtained numerical results, the local behavior of the sandwich plate in bending against various loading conditions was significantly improved by employing the shape memory alloy wires in the face sheets.

Low‐velocity impact response in composite plates embedding shape memory alloy wires

AbstractIn this work, the behavior of hybrid composite plates, embedding superelastic shape memory alloy (SMA) wires, subjected to low‐velocity impacts was studied. The impact experiments were performed on glass reinforced thermoset composite plates containing 1% by volume of superelastic thin wires (0.1 mm of diameter) of a SMA. The specimens were impacted with instrumented drop weight impact equipment: different dropping heights were used to attain impact energies from 1 to 500 J. The shape and size of damaged area were analyzed using two nondestructive inspection methods: (1) light scattering under back illumination was used to observe minor damages such as matrix cracks and fiber matrix debonding and (2) the size and shape of large damages such as delaminations were evaluated by infrared thermography. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Special issue on smart materials and structures

Smart materials and structures are inspired in nature and try to mimic adaptive characteristics of natural systems. In brief, it is possible to say that smart materials have special properties that couple mechanical and non-mechanical fields, conferring adaptive characteristics. Smart systems and structures use this kind of material as sensors and actuators. In general there are four major groups of smart materials: piezoelectric, shape memory alloys, magnetostrictive materials, electro-magneto rheological fluids. Nowadays, several fields of science and technology are exploiting the remarkable properties of smart systems and structures including bioengineering, aerospace engineering, robotics and vibration/shape control. Therefore, several applications have been developed, giving the increasing importance to this kind of system. In order to consolidate this new design paradigm in Brazil, several research groups from different Brazilian Universities and also international partners created the National Institute of Science and Technology of Smart Structures in Engineering (INCT-EIE) . Moreover, the Brazilian community created the Committee of Smart Materials and Structures of the Brazilian Society of Mechanical Sciences and Engineering (M&EInt/ABCM) . In order to celebrate the consolidation of this area in Brazil, we are producing this Special Issue on Smart Materials and Structures of the Journal of the Brazilian Society of Mechanical Sciences and Engineering. This special issue presents a general overview of the activities of the Brazilian community together with the international partners. Applications of piezoelectric materials and shape memory alloys are mainly discussed in the contributions. Kalamkarov and Savi (2012) presented a review of micromechanical modeling of smart composite structures reinforced by a periodic grid that can exhibit piezoelectric behavior. The asymptotic homogenization is employed. Trindade and Benjeddou (2012) developed a parametric analysis of effective material properties of thickness-shear piezoelectric macro-fibre composites. Finite element homogenization method is employed evaluating the influence of several parameters on material properties. Medeiros et al. (2012) presented a procedure to evaluate effective properties on smart composite materials with piezoelectric fibers. Finite element method is applied for unidirectional periodic piezoelectric composites. Nitzsche (2012) discussed the realization of semi-active actuators employed for application in structural control. The general idea is applied for an actuator using piezoelectric material as adaptive material. Motter et al. (2012) discussed vibration-based energy harvesting employing piezoelectric materials. Different rectifier circuits are of concern, analyzing numerical and experimental results. Abreu et al. (2012) presented a discussion about active vibration control of a cantilever beam using a model-based digital controller and piezoelectric sensor and actuators. The main focus of the paper is the design of the controller, showing experimental results that assure its efficacy. Martins et al. (2012) treated the structural health monitoring for aeronautical applications by using piezoelectric materials. Electromechanical impedance measures are employed to perform nondestructive inspection. The paper discussed a case study of an aluminum aircraft window with satisfactory results. De Paula et al. (2012) investigated the nonlinear dynamics of large-scale space structures with embedded shape memory alloy actuators. The investigation considered an archetypal model composed of a single mass connected by SMA elements. This system has a complex behavior including chaos. The paper discussed some aspects of the system dynamics giving special attention for the influence of geometrical imperfections. Lima et al. (2012) discussed the control of a beam using shape memory alloys as actuators. A PI controller is employed to an experimental rig showing its applicability for the deformation control.

Internal stresses in steel plate generated by shape memory alloy inserts

Neutron strain scanning was employed to investigate the internal stress fields in steel plate coupons with embedded prestrained superelastic NiTi shape memory alloy inserts. Strain fields in steel were evaluated at T=21°C and 130°C on virgin coupons as well as on mechanically and thermally fatigued coupons. Internal stress fields were evaluated by direct calculation of principal stress components from the experimentally measured lattice strains as well as by employing an inverse finite element modeling approach. It is shown that if the NiTi inserts are embedded into the elastic steel matrix following a carefully designed technological procedure, the internal stress fields vary with temperature in a reproducible and predictable way. It is estimated that this mechanism of internal stress generation can be safely applied in the temperature range from −20°C to 150°C and is relatively resistant to thermal and mechanical fatigue. The predictability and fatigue endurance of the mechanism are of essential importance for the development of future smart metal matrix composites or smart structures with embedded shape memory alloy components.

Nonlinear finite element analysis of shape memory alloy (SMA) wire reinforced hybrid laminate composite shells

This study introduces a non-linear finite element analysis approach to the procedure of modeling hybrid laminate composite shells with embedded shape memory alloy (SMA) wire subjected to coupled structural and thermal loading. Numerical analyses of SMA wire reinforced composite laminates were carried out by synergizing the non-linear laminate shell element with Brison's model of the SMA constitutive law. To verify the proposed procedure, the present illustrative applications involve rectangular laminated panels clamped along one side. Analysis results were compared with corresponding experimental results from a prior study. Several test cases that depend on the volume fraction of SMA, temperature, and ply angles are presented to illustrate the highly entangled thermo-mechanical behavior of shape memory alloy hybrid composites (SMAHCs). The results of the numerical analysis show the ability of the suggested procedure to compute the thermo-mechanical behavior of a SMAHC in accordance with the SMA's internal phase transformations induced by stress and temperature variation and demonstrate very good agreement with experimental results.

Thermal Post-Buckling Improvements of Laminated Composite Plates Using the Active Strain Energy Tuning Approach

Shape memory alloy was firstly used commercially as a hydraulic coupling in the Grumman F14A in 1971. It is today used among others to improve structural behaviours such as buckling of composite plates in the aerospace vehicles. In this paper, finite element model and its source code for thermal post-buckling of shape memory alloy laminated composite plates is presented. The shape memory alloy wires induced stress that improved the strain energy, stiffness and thus the buckling behaviour of the composite plates. The finite element formulation catered the combined properties of the composite and shape memory alloys, the addition of the recovery stress and the temperature dependent properties of the shape memory alloys and the composite matrix. This study showed that by embedding shape memory alloy within layers of composite plates, post-buckling behaviours of composite plates can be improved substantially.

Multi-Chip RFID Antenna Integrating Shape-Memory Alloys for Detection of Thermal Thresholds

Low-cost wireless measurement of objects' temperature is one of the greatest expectation of radiofrequency identification technology for the so many applications in cold supply-chain control and safety assessment in general. In this context, the paper proposes a dual-chip UHF tag embedding shape memory alloys (SMA) able to transform the variation of the tagged item's temperature into a permanent change of antenna radiation features. This event-driven antenna is hence able to selectively activate the embedded microchips according to the temperature above or below a given threshold. A general design methodology for the resulting two-ports tag antenna is here introduced and then applied to prototypes able to work at low (around 0°C) and high (80°C) temperatures.

Crack Closure and Shape Restoration Using NiTi Shape-Memory Alloy

Because of the high actuation stress and high recovery strain, NiTi shape-memory alloy (SMA) has been proposed for shape/position control and crack closure in structures for many years. In this paper, we demonstrate the feasibility to use NiTi SMA for not only crack closure, but also shape restoration in a silicon/nanoclay composite beam. Instead of embedding SMA into the beam, we use a piece of external SMA wire so that the expensive NiTi SMA can be reused. In addition, both shape restoration and crack closure can be achieved even when the beam is still in working condition, i.e., with external load applied.

Exploration and evaluation of embedded shape memory alloy (SMA) microvalves for high aspect ratio microchannels

This paper presents a microvalve actuated by shape memory alloy (SMA). This microvalve is designed particularly for controlling high aspect ratio polydimethylsiloxane (PDMS) channels and can be embedded into PDMS based microfluidic chips. This SMA microvalve can be designed either as a normally closed or normally open microvalve. Both designs utilize SMA wires for thermal actuation and operation to open or close microchannel flow. In this work, detailed parametric studies have been performed. The response open time of the normally open microvalve could be as low as 1 s at a flow rate of 4 μL/min, which is very short for a thermomicrovalve.

Thermal Buckling and Post-Buckling Improvements of Laminated Composite Plates Using Finite Element Method

Thermal buckling and thermal post-buckling behaviours of laminated composite plates are improved by embedding shape memory alloy wires within laminates of composite plates. The procedure is to use the recovery stress that is induced when the reverse transformation of the shape memory alloy from martensite to austenite phases is constrained. For aerospace applications where the source of the shape memory alloy heating is the high temperature environment itself, a study is conducted to see the effect of shape memory alloy in improving the thermal buckling and post-buckling of composite plates. Due to the temperature dependent nature of the composite matrix and the shape memory alloy, the finite element formulation developed here is in the incremental form. Solving this non-linear model using the developed in-house source code, critical loads are determined and the post-buckling paths of the shape memory alloy composite plates are traced. This study shows that by embedding the shape memory alloy within composite plates, the thermal buckling and post-buckling behaviours of composite plates can be improved substantially.

A New Method of Wireless Health Monitoring for SMA Composite Structure Based on Micro-Capacitance Measurement

In order to achieve the real-time monitoring internal state of composite specimen embedded shape memory alloy wires, a new wireless monitoring method in which PS021 is used to measure the capacitance change of composite structure is proposed. The micro-capacitance measuring principle of PS021 and the design of hardware and software of system are introduced in detail. The capacitance signal between some two wires of composite structure embedded SMA is measured by the PS021 module, and the measurement data are processed by C8051F330 micro-controller and wirelessly sent to PC by PTR4000. Compared the tested results with that of the high precision LCR meter, experimental results show that the relative error of system is less than 4.5%.

Design of a Flexible Bending Biomimetic Octopus Arm Unit with Embedded SMA Wires

This paper discusses a design of a flexible bending biomimetic octopus arm unit. Firstly, bending function of the octopus arm is analyzed. Secondly, the structure of the arm unit driven by shape memory alloy (SMA) is presented which can realize flexible bending. Meanwhile, mechanical model of the arm unit is established to find the proper parameters of the arm unit. Finally, experiments are carried out to demonstrate the feasibility of the structure.

Residual strength distribution of impacted glass/epoxy laminates with embedded shape memory alloy at low temperature

Abstract This paper evaluated the strength reduction and probabilistic behaviors of the residual flexural strength for impacted glass/epoxy laminates with embedded shape memory alloy (SMA) wires at various temperatures. A series of impact tests were performed on base (glass/epoxy laminates without SMA wires) and SMA laminates (glass/epoxy laminates with embedded SMA wires) at temperatures of 293 K, 263 K and 233 K. Three point flexural tests were then carried out so as to investigate the post-impact strength at the aforementioned temperatures. Strength reduction behavior of impacted laminates could be described by Caprino’s residual strength prediction model. A probabilistic model was developed in order to estimate the variation in residual strength of the impacted laminates with temperature. As the temperature decreased, the variation in residual strength increased due to the embrittlement of the constituent materials of the laminates at lower temperatures. When compared to the base laminates, the SMA laminates exhibited a higher variation in residual strength, especially at lower temperatures.