Temperature Of Shape Memory Alloy Research Articles

Experimental free vibration and tensile test results of a five-layer sandwich plate by comparing various carbon nanostructure reinforcements with SMA

Considering to need for the sensitive and destructive industries for high stiffness and low weight, an experimental free vibration and tensile test results of a five-layer sandwich plate by comparing various carbon nano structures reinforcements with SMA is discussed. The effect of various reinforcements, including carbon nanostructures (carbon nanotubes (CNT), carbon nanorods (CNRs), Graphene platelets (GPLs)) and nitinol shape memory alloy (SMA) wire on the vibration behavior of a five-layer sandwich plate with a foam core is investigated. The purpose and novelty of this work are to compare the effect of different reinforcements on the vibrations of a five-layer plate so that by using this comparison, one can choose the best reinforcements according to the needs of the desired industry and more suitable economic conditions. Considering a 1 % weight fraction of epoxy resin, GPLs, CNTs, and CNRs increase Young's modulus of face sheets by 30 %, 25 %, and 5.8 %, respectively. In this work, a five-layer sandwich structure model can be suggested, and numerically analyzed. The special advantage novelty of this research compared to previous research is the construction of this five-layer model. This is a simple modeling structure for the construction and preliminary examination of structures with five layers experimentally. Also, the composite structure is made by the vacuum pump method, which does not have the disadvantages of the manual method, and the method is completely optimal. At first, the Young's and shear moduli of unidirectional glass fiber (UGF) are calculated by performing a tensile test. To examine all aspects of the construction of five-layer structures during construction, in this article first, the face sheets are made separately using resin, UGF, and various reinforcements, and then the layers of face sheets and the cores are connected using glue. In the following, the equations of motion for the sandwich plate are derived using refined first-order shear deformation theory (RFSDT) by employing Hamilton's principle. Using the Halpin-Tsai equation and the extended rule of mixture, the mechanical properties of the reinforced composite face sheets are obtained. According to the Brinson model, the constitutive equations of the SMA are presented. The influence of various parameters such as side ratio, thickness ratio, weight fraction of CNRs, CNTs, GPLs and SMA wire, fiber angle, and temperature changes on dimensionless fundamental frequency is also represented. Also, the natural frequency of orthotropic plates by considering reinforcements is higher than that without considering reinforcements. By increasing the aspect ratio (a/h), the dimensionless natural frequency increases, while the natural frequency decreases. For two-layer square angular asymmetric laminated sheets (-θ/θ), the minimum dimensionless natural frequency occurred at the fiber placement angle approximately equal to 26 and 64°. The highest frequency is related to the sandwich plate in that its face sheets have higher strength and stiffness because it is placed further from the middle plane. Also, the highest frequency is related to the sandwich plate, whose face sheets are reinforced with GPLs.

Development of a Self-Regulating Solar Shading Actuator Based on the Thermal Shape Memory Effect

In the field of adaptive building technologies, this research introduces the development of a self-regulating solar shading actuator that utilizes the thermal shape memory effect. The study focuses on addressing the actuator’s performance under diverse environmental conditions. Thermal simulations were carried out during the development of the individual components of the actuator and for the prediction of specific switching temperatures. The investigation includes an analysis of the sunshade’s response to varying environmental conditions, emphasizing its effectiveness on clear summer days and identifying challenges during overcast periods. The critical coordination between the solar collector and the shape memory alloy (SMA) wire is examined, shedding light on the impact of SMA temperature dynamics on the actuation performance. Through the integration of simulation data and real-world measurements, the study validates the thermal model for the solar collector, establishing the robustness of the system’s operation. This research work contributes significantly to the development of intelligent actuators and outlines the importance of validation of SMA-based applications under real conditions.

Stochastic FEM-based thermal buckling of SMA fiber-reinforced composite laminated plate using polynomial chaos

This research investigates the statistics in terms of mean and coefficient of variance of thermal buckling temperature of shape memory alloy (SMA) fiber-reinforced composite laminated plate using polynomial chaos (PC). The basic mathematical formulation is adopted based on Co finite element method (FEM) in conjunction with secant function-based shear deformation theory. The uncertain input system properties in material and geometrical parameters are modeled as random variables. The effects of SMA fiber and location, pre-strain, loading, modes, temperature distribution, modulus ratio, fiber orientation, length-to-thickness ratio, aspect ratio, and various boundary conditions on the statistics of critical temperature are analyzed. The small amount of random change in input system parameters significantly affects the variance and reliability of SMA fiber-reinforced composite laminated plate thermal buckling temperature under uniform and non-uniform temperature variations. The present PC simulation’s results are compared with independent Monte Carlo simulation and those existing in the literature.

Design and Analysis of a Novel Variable Stiffness Continuum Robot With Built-in Winding-Styled Ropes

Continuum robots driven by rods have a wide range of applications, such as detection and maintenance tasks in unstructured environments. However, their inherent nature of flexibility also limits their function. Thus, variable stiffness mechanisms for continuum robots have consistently attracted the attention of researchers in recent years. In this letter, a winding-styled rope inspired by snakes’ behavior is first built into the constraint disk of a rod-driven continuum robot. Combined with shape memory alloy (SMA) spring, the winding ropes perform a variable stiffness or ‘lock’ function by adjusting the friction between the ropes and rods. A maximum static friction is up to 2 times the spring tension according to the test results. Based on the fitting relationship between SMA spring tension and friction, the established kinetostatics model can predict the manipulator configuration. Furthermore, comparative experiments proved that the stiffness change is mainly caused by the proposed mechanism. By controlling the temperature of SMA, the variable stiffness of the manipulator is achieved. The C-shape has a maximum stiffness of 0.03505 N/mm and that this shape has a maximum stiffness increase of 300%.

Study of Variable Thickness Magnetorheological Transmission Performance of Electrothermal Shape Memory Alloy Squeeze

This paper designs a new composite transmission device for improving the transmission torque by squeezing magnetorheological fluid (MRF) with an electrothermal shape memory alloy (SMA) spring. Based on the finite element method, a numerical analysis of the magnetic circuit and magnetic field distribution of the magnetorheological (MR) transmission is presented, as well as a theoretical derivation and calculation of the squeezing force output by the electrothermal SMA spring and the transfer torque of the variable thickness MR transmission. In addition, the output characteristics of the electrothermal SMA spring at different temperatures are analyzed, as are the torque characteristics of the variable thickness MR transmission. The research shows that the electrothermal SMA springs exhibit a highly non-linear squeezing force output during the temperature rise, and the increase in current affects the martensite phase transition quality, and thus the phase transition temperature. The squeezing force generated by the springs increases significantly when the temperature is within the martensitic phase transformation interval, with a maximum squeezing force of 318.43 N when the SMA temperature reaches 100 °C. The proposed variable thickness MR transmission can increase the maximum torque by 4.88 times under SMA spring squeezing force, and its maximum transmitted torque is increased from 15.08 to 73.56 N·m. By squeezing the MRF with an electrothermal SMA spring, the torque of the variable thickness MR transmission can be increased quickly and effectively.

A Variable Length, Variable Stiffness Flexible Instrument for Transoral Robotic Surgery

Transoral robotic surgery (TORS) in upper aerodigestive tract remains challenging due to the rigidity and insufficient workspace of existing instruments, and inappropriate balance between compliance and stiffness in flexible instruments. In this letter, a flexible surgical robotic instrument, featuring a shape memory alloy (SMA)-based continuously variable length bending joint (CVLBJ), was developed for TORS. The integration of the CVLBJ allows bending length adjustment, leading to enhanced distal workspace compared to traditional fixed length flexible instruments. The instrument also exhibits variable stiffness capability via the length variation of the CVLBJ and the SMA temperature variation. The quasi-static, kinematics, and stiffness model were developed to evaluate quantitatively the instrument workspace and stiffness range. The instrument was experimentally characterized and shown to provide a range of bending configurations suitable for the easily accessible oropharynx and the less accessible larynx, and stiffness range between 0.21 N/m and 1.83 N/m that is sufficiently large for tissue manipulation tasks. The instrument was also demonstrated to be capable of accurate motion tracking, given significant payload and 3D trajectory references. The proposed CVLBJ-integrated flexible instrument offers the variable length and variable stiffness properties missing in existing instruments that could potentially improve the clinical outcomes of TORS.

Transformation temperature and corrosion behavior of porous NiTi and NiTiCu shape memory alloy

The present research work deals with the fabrication of porous NiTi and NiTiCu shape memory alloy (SMA) by powder metallurgy process. These SMAs have number of applications in medical and space industries. The transformation temperature of both SMAs is measured by differential scanning calorimetry (DSC). Corrosion behavior is measured by potentiodynamic polarization curve in the presence of artificial saliva (pH value 7.4). Result shows that transformation temperature decreases by 8 °C to 10 °C after copper addition. Also, the corrosion current density decreases for NiTiCu, which exhibit more corrosion resistant than equi-atomic NiTi alloy. The corrosion current density of NiTiCu is less than NiTi by a factor of 31.

Development of a torsional theory for radially functionally graded porous shape memory alloy circular bars

This work develops a novel torsional theory for a radially functionally graded (FG) porous shape memory alloy (SMA) circular bar. Prior to the theoretical development, the effective three-dimensional (3D) phenomenological constitutive model for SMAs with high porosity is proposed. To help derive successfully the theory, the pure shear-driven material parameters in the effective model are expressed in the cubic polynomial. Subsequently, the torsional theory for radially FG porous SMA circular bar is derived considering the evolution of effective phase evolution in the bar. This phase evolution consideration guarantees the accuracy of the developed theory. Indeed, the soundness of effective constitutive model is confirmed by 3D finite element method (FEM) simulation of porous SMA structure in Abaqus using the well-established ZM’s model for dense SMAs. Specifically, the simulating results in terms of the shear stress-shear strain response obtained from two prediction methods considering a variation of SMA volume fraction and temperature are in good agreement. Furthermore, accuracy of torsional theory is validated by 3D FEM simulation using the 3D effective constitutive model with a good agreement observed. It is found that the superelasticity of the bar can be enhanced by increasing the gradient index and decreasing the temperature and wall thickness.

Shape control and design of aeronautical configurations using shape memory alloy actuators

The paper proposes an efficient methodology that allows to design smart deformable aeronautical configurations that are able to achieve pre-defined target shapes by adjusting the temperature of Shape Memory Alloy (SMA) actuators. SMA-based actuation finds extensive application in morphing concepts which are adopted in aeronautics to enhance the aerodynamic performance by continuously varying the geometry of the wing. A novel robust algorithm, developed for predicting the nonlinear response of the SMA-structure interaction problem is presented. The algorithm is coupled with an optimization method in order to predict the optimal structural and operational parameters with respect to target shapes of the controlled configuration. The design methodology presented in this study selects the design parameters of the problem at hand, i.e. the location of the actuators and the operating temperature, for given loading conditions. The proposed methodology is validated and demonstrated with three case studies, including the design of a real-world aeronautical configuration.

Multi-link endoscopic manipulator robot actuated by shape memory alloys spring actuators controlled by a sliding mode

The aim of this study was to design and evaluate a prototype of a snake-like endoscopic manipulator robot (SLEMR) and its corresponding automatic controller based on the first order sliding mode theory. The SLEMR was controlled with a set of actuators made of shape memory alloys (SMA). The SLEMR device was constructed with a sequential arrangement of links interconnected by a two degree-of-freedom joint. A parallel agonist–antagonist configuration of actuators was implemented to move each joint. The physical relation between temperature and elongation in SMA forced the execution of the movement in the joint. Elongation–temperature model of the SMA actuator served to get a feasible bound of velocity for each joint. Each pair of SMA actuators was controlled by a first order sliding mode controller. This control design solved the tracking trajectory problem for each joint in the SLEMR because of its robustness against uncertainties and external perturbations. The control action was projected into a feasible implementable set of pulse-width modulated signals which was used to regulate the temperature of the corresponding SMA actuator. The controller designed in this study was experimentally validated in a SLEMR made up by a tridimensional printing technique. The control strategy induced the successful trajectory tracking for all the joints in the SLEMR simultaneously. This characteristic of the control design also enforces the tracking of a reference position by the tip of the final link of the SLEMR. An image acquisition system was used to determine the position of the final actuator in the SLEMR. The effectiveness of the controller proposed in this study was confirmed by the evaluation of the tracking error of the final actuator which approached to a bounded region (less than 1.0 mm) near the origin in a finite-time (0.5 s).

Adaptive tuned mass damper with shape memory alloy for seismic application

When the characteristics of the main structure are changed, tuned mass damper (TMD) is easy to meet off-tuning problem. The object of this study is to develop a TMD with shape memory alloy (SMA) to reduce the vibration caused by off-tuning under seismic excitations. By materials characterisation of SMA, when the working temperature rises from −40 °C to 65 °C, the stiffness increases and the equivalent damping ratio drops. The SMA-based TMD was installed on a steel frame and tested under earthquake loading. The results show the SMA-based TMD is able to reduce the seismic response in the range of 34.09–47.77% at the tuned condition. However, by changing the main structural mass, the TMD was easy to be off-tuned. To retune the TMD, the SMA was heated and cooled for the TMD to resonate with the natural frequency of the main structure. When the SMA is cooled, the peak and RMS accelerations can be effectively reduced by up to 23.98% and 35.51%, respectively. It was found that the SMA-based TMD performs well if the frequency change of the main structure is in the same order. But when the temperature of SMA is increased higher than 19 °C, the damping ratio of SMA decreases, which causes a less effectiveness in reducing the vibration. In the future, the combinations of multiple SMA bars in TMD should be studied, and the applications of SMAs with higher phase transformation temperature can be investigated to improve the sensitivity while heating.

Re-tuning an off-tuned tuned mass damper by adjusting temperature of shape memory alloy: Exposed to wind action

To reduce the wind-induced vibration of building structures, tuned mass damper (TMD) is a widely used approach. However, the off-tune of TMD can cause larger excessive vibration to the structure. In this study, shape memory alloy (SMA) is employed in TMD for retuning. At first, the dynamic properties of SMA-based TMD were characterised by free vibration at between −40 °C and 65 °C. It is found the stiffness increased and damping reduced with rising temperature. Next, the SMA-based TMD was applied to a steel frame structure under wind excitations. The wind action was generated by autoregressive models method and input by a shaking table. The results present the wind-induced vibration can be attenuated effectively by installing a SMA-based TMD. By changing the main structural mass, the TMD was easy to be off-tuned and the structural response was increased. By means of cooling SMA to retune the TMD, the response of the system can be reduced effectively. However, the effect of heating SMA was relatively small. The increase of damping capacity by combing multiple SMA bars and the applications of SMAs with higher phase transformation temperatures are important to be further investigated in TMD, so as to improve the effectiveness of heating SMA.

Bending and buckling analysis of sandwich Reddy beam considering shape memory alloy wires and porosity resting on Vlasov's foundation

The aim of this research is to analyze buckling and bending behavior of a sandwich Reddy beam with porous core and composite face sheets reinforced by boron nitride nanotubes (BNNTs) and shape memory alloy (SMA) wires resting on Vlasov\'s foundation. To this end, first, displacement field\'s equations are written based on the higher-order shear deformation theory (HSDT). And also, to model the SMA wire properties, constitutive equation of Brinson is used. Then, by utilizing the principle of minimum potential energy, the governing equations are derived and also, Navier\'s analytical solution is applied to solve the governing equations of the sandwich beam. The effect of some important parameters such as SMA temperature, the volume fraction of SMA, the coefficient of porosity, different patterns of BNNTs and porous distributions on the behavior of buckling and bending of the sandwich beam are investigated. The obtained results show that when SMA wires are in martensite phase, the maximum deflection of the sandwich beam decreases and the critical buckling load increases significantly. Furthermore, the porosity coefficient plays an important role in the maximum deflection and the critical buckling load. It is concluded that increasing porosity coefficient, regardless of porous distribution, leads to an increase in the critical buckling load and a decrease in the maximum deflection of the sandwich beam.

Development and testing of the re-deployable radiator for deep space explorer

This paper reports the design, fabrication, and testing of a reversible thermal panel breadboard model (RTP-BBM). RTP is a flexible, re-deployable radiator that autonomously controls the temperature of a heat source. It promotes heat dissipation by deploying the radiator surface when the heat source is at a high temperature. Conversely, in a cold case, heat dissipation is conserved by stowing the radiator surface. Herein, deployment/stowing and thermal vacuum tests were conducted herein to evaluate the validity of the design, and model correlations were conducted via thermal analysis. The RTP-BBM comprises high thermal conductivity graphite sheets as the flexible fin, and shape-memory alloys (SMA) as a temperature sensitive passive actuator. The deployment/stowing test was conducted in a thermal constant bath, confirming that the fin was deployed and stowed according to the SMA temperature. However, temperature hysteresis of up to +60 °C was confirmed between heating and cooling cycles. In the thermal vacuum test, power step and power cycle tests were conducted. Results showed that the fin deployed and stowed according to the temperature of the onboard equipment while autonomously regulating the temperature. Additionally, the thermal analysis model correlated with the experimental results, showing good agreement within ±6 °C.

A distributed parametric model of shape memory alloy-based resonant frequency tunable cantilevered PZT energy harvester with tip mass

This paper presents an analytical model of piezoelectric vibration energy harvester consists of shape memory alloy (SMA) plate which can tune the resonant frequency. As the energy harvester should be tuned to excitation frequency to drive the maximum power, the temperature of SMA is varied to tune the natural frequency of the composite beam. In addition to SMA, it also consists of the piezoelectric layer, substructure layer, and tip mass. Using Euler–Bernoulli beam assumption, equations for the frequency response of voltage, current, and power outputs with temperature are obtained. From the parametric study, it is observed that the tuning of natural frequency is 25–26%, for the first three modes of vibration in short- and open-circuit conditions.

Experimental and Numerical Investigation of Mechanical and Thermal Effects in TiNi SMA during Transformation-Induced Creep Phenomena.

(1) The paper presents experimental and numerical results of the TiNi shape memory alloy (SMA) subjected to a modified program of force-controlled tensile loading. The time-dependent development of transformation strain under the constant-force conditions was investigated to describe transformation-induced creep phenomena. (2) Mechanical characteristics of the TiNi SMA were derived using a testing machine, whereas the SMA temperature changes accompanying its deformation were obtained in a contactless manner with an infrared camera. A 3D coupled thermo-mechanical numerical analysis, realized in a partitioned approach, was applied to describe the SMA mechanical and thermal responses. (3) The stress and related temperature changes demonstrated how the transformation-induced creep process started and evolved at various stages of the SMA loading. The proposed model reproduced the stress, strain and temperature changes obtained during the experiment well; the latent heat production is in correlation with the amount of the martensitic volume fraction. (4) It was demonstrated how the transformation-induced creep process occurring in the SMA under such conditions was involved in thermo-mechanical couplings and the related temperature changes.

A distributed parametric model of Brinson shape memory alloy based resonant frequency tunable cantilevered PZT energy harvester

This paper presents, an analytical model of piezoelectric vibration energy harvester consists of Brinson shape memory alloy (SMA) plate which can tune the resonant frequency. As the energy harvester should be tuned to excitation frequency in order to drive the maximum power, the temperature of SMA is varied to tune the natural frequency of the composite beam. In addition to SMA it also consists of piezoelectric layer and substructure layer. Using Euler–Bernoulli beam assumption, the expressions for frequency response of voltage, current and power outputs with temperature are obtained. From parametric study, it is observed that the tuning of natural frequency is 25–26%, for first three modes of vibration in short and open circuit conditions.

Analytical model of functionally graded material/shape memory alloy composite cantilever beam under bending

A new analytical model for a functionally graded material (FGM)/shape memory alloy (SMA) laminated composite cantilever beam subjected to a concentrated tip load is developed. The novelty of this work lays in the analytical modelling of moment-curvature and shear force-shear strain relations, which are derived based on ZM model and Timoshenko’s theory for all stages during loading and unloading. A high-accuracy numerical solution and a three-dimensional finite element analysis (3D FEA) for the composite beam are carried out to validate the analytical solution. The results show very good agreement in each case. The influence of gradient direction, gradient index, temperature, and relative thickness ratio of SMA to functionally graded layer on superelasticity of carbon nanotube (CNT)-epoxy-based-FGM/SMA composite beam is also examined. The results show that the superelasticity of CNT-epoxy FGM/SMA composites increased with an increase in gradient index and decreased with an increase in thickness ratio. The temperature variations induced less effect on the superelasticity of FGM/SMA composites. Furthermore the composite beam with FGM layers having the Young’s modulus graded increasingly in the inward direction exhibits a better superelastic property in comparison with that with FGM layers having the Young’s modulus graded increasingly along the outward direction.

Two Way Stiffness Tuning Of Magnetorheological Elastomer- Shape Memory Alloy Composite

Structural vibration control by tuning structural material modulus through external stimuli is great deal of interest for researchers. Shape memory alloy (SMA) is kind of smart material whose modulus can be varied by changing its temperature. Temperature dependent change in modulus of SMA during phase transformation is stiff and nonlinear which inducts difficulties for getting smooth structural stiffness change to alter its dynamic behavior. This paper deals with the work wherein, SMA is combined with magnetorheological elastomer (MRE) to form composite. MRE is another smart material whose shear modulus consequently stiffness can be changed by exposing it to variable magnetic field. Smart MRE-SMA composite has been studied analytically for stiffness variation by combining Maxwell form of three parameter constitutive viscoelastic material model, model for magnetic field dependent change in shear modulus for anisotropic MRE and temperature dependent modulus of SMA. The composite is fabricated, tested for stiffness change with respect to external stimuli by natural frequency measurement method and the results are compared with analytical study. The result show that the stiffness nonlinearity exists in SMA during transformation phase has been minimized by wisely selecting values of temperature and strength of magnetic field simultaneously. Significant level of smooth stiffness change is achieved by proper tuning of SMA temperature and strength of magnetic field.

Shape memory alloy resistance behaviour at high altitude for feedback control

Many recent aerospace technologies are using smart actuators to reduce the system's complexity and increase its reliability. One such actuator is shape memory alloy (SMA) actuator, which is lightweight, produces high force and large deflection. However, some disadvantages in using SMA actuators have been identified and they include nonlinear response of the strain to input current, hysteresis characteristic that results in inaccurate control and less than optimum system performance, high operating temperatures, slow response and also high requirement of electrical power to obtain the desired actuation forces. It is still unknown if the SMA actuators can perform effectively at high altitude with low surrounding temperature. The work presented here covers the preliminary process of verifying the feasibility of using resistance as feedback control at high altitude for aerospace applications. Temperature and resistance of SMA actuator at high altitude is investigated by conducting an experiment onboard a high altitude balloon. The results from the high altitude experiment indicate that the resistance or voltage drop of the SMA wire is not significantly affected by the low surrounding temperature at high altitude as compared to the temperature of SMA. Resistance feedback control for SMA actuators may be suitable for aerospace applications.