Applications Of Shape Memory Alloys Research Articles

The driving characteristics of bidirectional SMA wire actuators - Theoretical modeling and experimental testing

Bidirectional shape memory alloy (SMA) wire actuators play a critical role in driving applications thanks to their characteristics in memory shaping and good overall performance. SMA wire actuators were often studied at a single load type, and there is no comprehensive comparison investigation of different SMA wire actuators in the literature. In this paper, the driving characteristics of four available types of SMA wire actuators, namely, dead-load, biased spring, differential type, and biased superelastic SMA wire actuators are modelled mathematically and then tested in laboratory settings. The characteristics of SMA wire actuators are quantitatively measured and then compared under a range of application scenarios. The output displacement and thermal-electric models of NiTi SMA wires are derived based on the Brinson constitutive model with stress effects in consideration. A customized SMA wire actuator test device is developed to evaluate the theocratical models and benchmark testing four types of SMA wires and their driving characteristics, including structure, design, displacement, response and recovery time, energy efficiency and hysteresis properties. The SMA wire phase transformation characteristics of the four actuators are tested under different activation currents, and then quantitatively compared. In conclusion, this paper adds theoretical and experimental significance to the literature on SMA wire actuators. The reference value on the phase transformation characteristics of SMA wires can be used to guide SMA application in industrial designs and enable theoretical studies in complementary research areas.

Designing a Morphing Wing for Fixed-Wing UAVs By IJISRT

This project report details the original conceptualization, design, and analysis of a morphing wing structure for fixed-wing Unmanned Aerial Vehicles (UAVs). Our approach incorporates an octahedron cell structure coupled with the application of shape memory alloys(SMAs) to facilitate controlled wing morphing. The primary goal is to augment the UAVs aerodynamic efficiency and adaptability to various flight conditions. The octahedron cell structure is employed as the foundational framework, providing a balance between structural integrity andflexibility for shape adjustments. The integration of shape memory alloys, known for their reversible phase transformations, enables precise and efficient control over the morphing process. Through this combination, we aim to optimize the UAVs flight characteristics, including improved efficiency, stability, and maneuver ability. To validate the feasibility and performance of the morphing wing design, Finite Element Analysis (FEA) has been conducted. This computational approach allows for a comprehensive evaluation of the structural integrity and aerodynamic behavior of the morphing wing under diverse loading conditions. The FEAresults offer crucial insights into the structural response, stress distribution, and deformation patterns, guiding the iterative refinement of the design for optimal functionality. This project represents a unique contribution to UAV technology, presenting an original perspective on morphing wing design that harnesses the benefits of octahedron cell structureand shape memory alloys. The insights gained from the FEA analysis provide valuable guidance for the ongoing development and implementation of morphing wing structures in fixed- wing UAVs. This work sets the stage for improved adaptability and performance in a range of operational scenarios, without reliance on external sources or existing research

A fast actuated soft gripper based on shape memory alloy wires

The application of shape memory alloy (SMA) actuated soft grippers is limited by their slow recovery speed. In order to further expand their application range, as one of the solutions to address this limitation, this paper proposes a fast actuated soft gripper based on SMA wire active heat dissipation and elastic rib combination to meet the rapid actuation and recovery. The structure primarily consists of a heat dissipation module capable of winding SMA wire and a soft structure resembling a scorpion tail with embedded supper elastic SMA wire. The geometric structure model, dynamics and SMA constitutive model and finite element model of the soft gripper are established, and the lateral deformation of soft bionic scorpion tail end is analyzed through simulations and experiments. In addition, the force in designed soft gripper tip and its ability to grasp different objects are also studied through experiments. The results show that the addition of a cooling fan increased the recovery rate by about 25%, and the force in soft bionic scorpion tail end can reach about 0.12 N. The designed soft gripper can successfully grasp objects with different softness, shape, size and weight. It lays a theoretical foundation and technical support for the development of soft grippers actuated by SMA in the future.

Recent progress in shape memory alloy reinforced composites: A review of the properties, production, mechanisms involved and functional applications

SMAs are unique materials characterized by their 'Superelasticity' (pseudoelasticity) and 'Shape Memory Effect.' Its unusual properties have led to its use in various fields of science. However, its mechanical advantages are not fully exploited due to its price and lack of data. SMAs are not adopted widely in industries due to the scarcity of manufacturing knowledge. Potential uses for them came in the form of reinforcements in composites. The rapidly growing field focuses on the incorporation of Shape Memory Alloy wires, ribbons, fibres, and powders in polymer or metal matrices. Its effect on static and dynamic material properties is also of great importance, especially when it comes to incorporating it into modern-day applications. Hence, this paper deals with a summary of all those properties. Furthermore, the article touches upon the possible applications of Shape Memory Alloy Reinforced Composites in the real world and their potential scope in the future.

A review on CuAlNi shape memory alloys: Production methods, applications and current trends

Shape Memory Alloys (SMAs) are one sort of shape memory material (SMM) that “remembers” the initial shape when subjected to stimuli like magnetic or thermomechanical changes. Cu-based SMAs in the past decade have emerged successfully as potential materials in various applications such as Sensors, actuators, and high-damping materials. Cu-Al-Ni SMAs have received attention because they are more thermally stable than other Copper-based SMAs. Cu-Al-Ni SMA is an excellent candidate with excellent SME and super-elastic behaviour in the narrow temperature range of 373–473 K. Nickel is added in the binary system of Cu-Al to lower the high transformation temperature and stabilise the austenite phase. This Paper reviews Production Methods, Applications and Current Trends of CuAlNi SMA.

A constitutive model of nanoporous NiTi shape memory alloys considering tensile-compressive asymmetry, grain size and porosity

A constitutive model of the macroscopic behaviors of nanoporous Shape Memory Alloys (SMAs) is developed, and the effects of tensile-compressive asymmetry, grain size, and porosity are all considered because the influences of these factors cannot be ignored. A finite-volume, three-phase micromechanical model that contains the grain boundary phase, grain-core phase, and uniformly distributed pores is first given to represent the grains of nanoporous NiTi SMAs. The secant equivalent bulk modulus and shear modulus of the nanoporous NiTi SMAs were calculated by using the extended Mori-Tanaka method. Due to the high plastic yield limit of the grain boundary phase, the grain boundary phase is regarded as the region where no phase change occurs. And the overall phase transformation can be caused by the grain-core phase. The phase transformation is established according to the J2, J3 theory and the von Mises equivalence effect. The martensite volume fraction is represented in this article as a linear interpolation function of equal effectiveness. Based on the strain-hardening behavior, the equivalent stress of nanoporous NiTi SMAs is represented by a power function consisting of transformation onset stress, hardening modulus, equivalent phase change strain, and hardening index. Then, the constitutive model describing the superelastic behavior can be obtained. By comparing the numerical simulation results with the experimental results, it is verified that the constitutive model proposed in this paper can better describe the superelastic behavior of the nanoporous NiTi SMAs. Finally, through numerical simulations, it was found that tensile-compressive asymmetry, grain size, and porosity have significant effects on the superelastic behavior of nanoporous NiTi SMAs. This study will provide a theoretical basis for the application of nanoporous NiTi SMAs.

A comprehensive exploration of shape memory alloys: Fundamentals, structural reinforcements, nano-analysis, machine learning perspective, and emerging applications

Shape memory alloys (SMAs) are widely used across various industries, including medicine, due to their inherent properties such as the shape memory effect, pseudo-elasticity, antigenicity, decomposition, biodegradability, biocompatibility, resistance to corrosion, and wear. This review article aims to cover different aspects of SMAs, including their fundamental concepts such as origin, exceptional properties, fabrication techniques, and structural analysis. Exploring the SMAs at the nanoscale using molecular dynamics analysis and recent studies that integrate machine learning techniques. Finally, the article concludes with a discussion of various applications of SMAs, considering the properties and potential fields of use.

Problems of modeling elements with shape memory alloys of military equipment

Shape memory alloys (SMAs) are used in various fields, including military equipment, to create means with autonomous or improved properties. It can be especially useful in structural elements that are capable of self-healing after deformations or damage as a result of explosions, impacts or other loads that occur during military operations.
 SMAs are materials that have the ability to remember and restore the accumulated deformation under certain conditions. This makes them particularly useful in robotics, where they can be used to create moving parts, sensors, actuators and other components.
 One of the main applications of SMA in robotics is the creation of moving elements. For example, they can be used to create bendable segments in jobs that require flexibility and mobility. SMAs can be used to create manipulators that allow a robot to easily move and perform tasks in different environments. One of the most important properties of SMAs is their ability to retain their shape during deformation. This makes them useful for building sensors that can detect differences in the shape of an object. SMAs can be used to create pressure sensors that respond to a change in shape under the influence of external pressure. These sensors can be used to develop robots that can recognize objects and distinguish them by shape. SMA can also be used to create actuators. Actuators are components that convert electrical, mechanical, or other types of energy into motion. SMA are materials that have the ability to remember and restore the accumulated deformation under certain conditions. This is achieved due to the peculiarities of their microstructure and thermoelastic effect. When SMA is subjected to thermal influence in the temperature zone where it can transition between two states: austenitic (higher temperature) and martensitic (lower temperature), under an existing external load, the phase strain increases, and with the degree of load, the temperature of the beginning and end of the emerging of straine changes. Each of these states has its own crystal structure and characteristics determined by its chemical composition. The article considers the issue of taking into account the shift of characteristic temperatures under the influence of an external load of SMA in terms of the synthetic theory of irreversible deformation and proposes a non-linear formula for finding the characteristic temperatures of metals with memory during loading. The obtained ratio was used to find the proportion of the new phase and the rate of formation of the new phase as a function of the magnitude of the external load, the rate of loading, the absolute temperature, the rate of temperature change and the characteristic temperatures in terms of the effective temperature.

Influence of building directions on the impact properties of NiTi fabricated via laser powder bed fusion

The Charpy impact toughness is a crucial mechanical parameter in the application of materials within the realm of engineering. This study represents the pioneering investigation into the influence of different building directions on the Charpy impact toughness of NiTi shape memory alloys (SMAs) produced via laser powder bed fusion (LPBF). Texture analysis reveals that C0 and C90 exhibit a pronounced <001>// building direction (BA), while C45 demonstrates a strong texture along <110> and <111>. The impact test results demonstrate that C0 exhibits superior impact toughness with an absorbed energy of 12.87 J. The fractured surfaces are examined using the scanning electron microscope (SEM) and transmission electron microscope (TEM). Among them, the electron backscatter diffraction (EBSD) results indicate that the samples with higher geometrically necessary dislocation (GND) and kernel average misorientation (KAM) values can effectively reflect superior impact toughness. In contrast, fewer high-angle grain boundaries (HAGBs) are preferable. Due to the adiabatic effect, the phase transformation of the samples from austenite to martensite doesn't appear under the impact loading. Additionally, this paper discusses the impact of texture orientation, defects, and the relationship between loading direction and deposited layers on the impact toughness of the samples. These findings on impact properties would provide valuable guidance for engineering applications of NiTi SMAs.

A Review on Comparison between NiTi-Based and Cu-Based Shape Memory Alloys

One of the best types of smart materials is Shape Memory Alloys (SMAs), which have more applications in modern technology such as aerospace, automotive, biomedical, civil engineering, robotics, and so on. Among all parts of them NiTi-based, and Cu–based are more focused on because they have some interesting properties that have made them more widely used in modern technology. In this work, the classifications and applications of SMAs according to the different application fields like biomedical, automotive, and aerospace have been reviewed. Besides the characteristic of (NiTi-based, Cu – based) and the comparison between them in many areas such as: In terms of cost, creation, corrosion resistivity, density, and electrical and thermal conductivity were represented. Each of NiTi and Cu-based SMAs has many useful applications and strengths, but they have some limitations.

The Applications of Shape Memory Alloy

With the rapid development of the aerospace industry, more stringent new requirements have been put forward for new materials. A large number of intelligent materials have emerged. The most noteworthy among them are shape memory alloys (SMAs). Therefore, the number of SMAs used for aerospace research has increased significantly. It is very necessary to analyze these works. This article focuses a specific kind of active materials called SMAs, especially for the applications of this material in the aerospace field. SMAs are able to ‘memorise’ or restore their previous form when facing thermal, thermomechanical or magnetic changes. Because of its superior performance and diverse uses, it is widely used in various engineering fields. A brief introduction of SMAs is provided in this work. Their outstanding properties and extraordinary working principle can also be seen in this article. Before and nowadays aerospace applications are introduced. The applications of SMAs in wing morphing, lifting body, and variable geometry chevron, were also introduced. This work will promote the application of SMAs in the aerospace field.

Flexural improvement of reinforced concrete beams strengthened with self-prestressing shape memory alloys

The study reported here aims to investigate the application of shape memory alloys (SMAs) in the form of strips for strengthening cracked reinforced concrete (RC) beams. The study proposes an innovative technique for prestressing RC beams by utilizing the shape recovery property of the alloy. Nine full-scale RC beams with a length of 3.75 m and a cross-section of 200 mm × 300 mm were categorized into three groups based on the steel reinforcement ratio, and tested under static loading. Three RC beams were used as control specimens and the other six were retrofitted with either one layer or two layers of SMA strips. The beams to be strengthened were exposed to an initial applied load before the installation of the SMA strip to simulate the deterioration scenario. SMA strips were retrofitted on the soffits of the deteriorated beams and activated by applying temperature from an external heat source while the temperature-deflection-strain measurements were monitored. Specimens were tested again up to failure to evaluate the strength improvement of the retrofitted specimens. Beams retrofitted with one layer of SMA experienced a deflection recovery up to 2.3 mm upon activation and an additional service load of up to 62%, whereas beams retrofitted with two layers experienced a deflection recovery up to 2.8 mm and an additional service load of up to 95%. In general, the deflection recovery was proportional to the ratio of the total reinforcement ratio after strengthening to the initial reinforcement ratio before strengthening. Therefore, tested specimens with two SMA layers experienced less improvement than specimens with one SMA layer. Finally, the experimental results were evaluated with two analytical methods: ACI method and the non-linear sectional analysis proposed by Oukaili.

Advances in Shape Memory Alloy-Based Reinforcement in Steel Structures: A Review

The utilization of shape memory alloys (SMAs) to reinforce steel structures has been proven to be an efficient and reliable method, the structural strengthening needs can be met without the need for tensioning equipment by activating the SMAs to generate restoring stresses. This paper firstly introduces the properties of SMA, and then presents the latest research progress, opportunities and challenges of SMA in the field of steel structural reinforcement, both in terms of basic components and applications. In terms of components, the construction forms and working mechanisms of Fe-SMA strips, SMA/CFRP composite patches and SMA dampers are introduced. On this basis, the application of SMA in steel structures reinforcement is introduced, and its effect is analyzed from three aspects: crack restoration, seismic retrofitting and structural strengthening. Finally, the results of the current research are summarized and the shortcomings are analyzed, hoping to provide a reference for the research of SMA in the field of steel structures reinforcement.

A Physics-Based Hybrid Dynamical Model of Hysteresis in Polycrystalline Shape Memory Alloy Wire Transducers

Shape memory alloys (SMAs) are a class of smart materials that exhibit a macroscopic contraction of up to 5% when heated via an electric current. This effect can be exploited for the development of novel unconventional actuators. Despite having many features such as compactness, lightweight, and high energy density, commercial SMA wires are characterized by a highly nonlinear behavior, which manifests itself as a load-, temperature-, and rate-dependent hysteresis exhibiting a complex shape and minor loops. Accurate modeling and compensation of such hysteresis are fundamental for the development of high-performance SMA applications. In this work, we propose a new dynamical model to describe the complex hysteresis of polycrystalline SMA wires. The approach is based on a reformulation of the Müller–Achenbach–Seelecke model for uniaxial SMA wires within a hybrid dynamical framework. In this way, we can significantly reduce the numerical complexity and computation time without losing accuracy and physical interpretability. After describing the model, an extensive experimental validation campaign is carried out on a 75- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m diameter SMA wire specimen. The new hybrid model will pave the development of hybrid controllers and observers for SMA actuators.

Experimental, mathematical model, and simulation of a dual-system self-centering energy dissipative brace equipped with SMA and variable friction device

The application of shape memory alloy (SMA) in seismic-resistant devices has received extensive attention due to its unique superelastic and shape memory effect. The poor energy dissipative capacity, insufficient reliability, and small bearing capacity are the main challenges that hinder the application of the developed SMA braces and dampers. The new system of self-centering energy dissipative (SCED) brace was proposed, fabricated, and tested, and the numerical model was defined and verified. The dates manifest that the load-displacement curve of the new dual-system SCED brace displays a typical flag shape. The new dual-system SCED brace exhibits the desirable energy dissipative ability and self-centering capacity and the theoretical and FE model established in this research can preferably express the hysteretic performance. The FE parametric analysis shows that the SMA screw preload has a small effect on the hysteretic curve of the new system brace, but it plays a decisive role in the shape of the hysteretic curve under small deformation. Furthermore, the bearing capacity and stiffness of the dual-system SCED brace can be adjusted by designing key parameters. The research shows that the new dual-system SCED device compensates for the shortcomings of the existing SMA braces and dampers, and it is a very promising and recommended self-centering energy dissipative device to use the wedge block system as the main energy dissipative system and SMA system as the main self-centering system.

Toughening of Ni-Mn-Based Polycrystalline Ferromagnetic Shape Memory Alloys.

Solid-state refrigeration technology is expected to replace conventional gas compression refrigeration technology because it is environmentally friendly and highly efficient. Among various solid-state magnetocaloric materials, Ni-Mn-based ferromagnetic shape memory alloys (SMAs) have attracted widespread attention due to their multifunctional properties, such as their magnetocaloric effect, elastocaloric effect, barocaloric effect, magnetoresistance, magnetic field-induced strain, etc. Recently, a series of in-depth studies on the thermal effects of Ni-Mn-based magnetic SMAs have been carried out, and numerous research results have been obtained. It has been found that poor toughness and cyclic stability greatly limit the practical application of magnetic SMAs in solid-state refrigeration. In this review, the influences of element doping, microstructure design, and the size effect on the strength and toughness of Ni-Mn-based ferromagnetic SMAs and their underlying mechanisms are systematically summarized. The pros and cons of different methods in enhancing the toughness of Ni-Mn-based SMAs are compared, and the unresolved issues are analyzed. The main research directions of Ni-Mn-based ferromagnetic SMAs are proposed and discussed, which are of scientific and technological significance and could promote the application of Ni-Mn-based ferromagnetic SMAs in various fields.

0.8 mm Ni–Ti shape memory alloy wires: Post-training behavior and application in a cold-formed steel structure

This study explores the post-training performance, mechanical training strategy, and potential seismic application of shape memory alloy (SMA) wires. A part of SMA wire specimens were trained by different training protocols, and subsequently all the untrained and trained SMA wire specimens were tested at room temperature under various cyclic loading protocols. It is observed that the incremental cyclic training could lead to a higher post-yield stiffness during the post-training stage at a certain expense of residual strain and forward transformation stress, and the post-training hysteretic behavior will be stable and predictable within the historical training strain amplitude. The influence of training on mechanical performance of SMA wires under near-fault loading was revealed and evaluated. Following the test program, a cold-formed steel (CFS) joint model employing SMA wires is proposed and analyzed to demonstrate the feasibility and efficiency of trained SMA wires for optimizing seismic performance. The finite element (FE) analysis results indicates that the self-centering CFS joint can effectively optimize the original pinched hysteretic response, including mitigating residual displacement, and improving the peak strength, initial stiffness and energy-dissipate capacity.

Efficient phase-field simulation for linear superelastic NiTi alloys under temperature gradients

Engineering the martensitic transformation (MT) with exceptional and controllable properties is essential for the innovative application of shape memory alloys (SMAs) in advanced technologies. Herein, we combine high-throughput (HTP) phase-field simulations and machine learning approaches to propose the concept of “temperature-controlled mechanics” and demonstrate that it is possible to design NiTi alloys with outstanding mechanical properties that integrate ultra-low modulus, linear superelasticity, and no hysteresis in environments with temperature gradients. These nontrivial mechanical properties originate from continuous variations in the critical stress for the MT, which contributes to a gradual and continuous MT rather than a sharp first-order transition as occurs in common SMAs. An active learning workflow based on uncertainty sampling is employed to guide phase-field simulations to efficiently clarify and optimize the temperature in the environment for different NiTi alloys with the desired properties. Furthermore, the SISSO (Sure Independence Screening and Sparsifying Operator) algorithm is applied to the datasets from the HTP simulations to establish an explicit expression for the Young's modulus, which is verified by additional phase-field simulations and is instructive for the inverse design of the temperature field. The present study not only provides fundamental insights into the effects of temperature gradients on MTs and overall mechanical properties, but also offers a promising computational approach for developing advanced materials with extraordinary properties.

Superelastic Nickel-Titanium (NiTi)-Based Smart Alloys for Enhancing the Performance of Concrete Structures.

Recent advances in materials science have led to the development of smart materials that can continuously adapt to different loading conditions and changing environment to meet the growing demand for smart structural systems. The unique characteristics of superelastic NiTi shape memory alloys (SMAs) have attracted the attention of structural engineers worldwide. SMAs are metallic materials that can retrieve their original shape upon exposure to various temperatures or loading/unloading conditions with minimal residual deformation. SMAs have found increasing applications in the building industry because of their high strength, high actuation and damping capacities, good durability, and superior fatigue resistance. Despite the research conducted on the structural applications of SMAs during the previous decades, the existing literature lacks reviews on their recent uses in building industry such as prestressing concrete beams, seismic strengthening of footing-column connections, and fiber-reinforced concrete. Furthermore, scarce research exists on their performance under corrosive environments, elevated temperatures, and intensive fires. Moreover, the high manufacturing cost of SMA and the lack of knowledge transfer from research to practice are the main obstacles behind their limited use in concrete structures. This paper sheds light on the latest progress made in the applications of SMA in reinforced concrete structures during the last two decades. In addition, the paper concludes with the recommendations and future opportunities associated with expanding the use of SMA in civil infrastructures.

Editorial: Application of Shape Memory Alloys

In the ambit of smart materials, shape memory alloys (SMA) have emerged as a remarkable class of materials capable of undergoing significant shape changes when stimulated by external factors such as mechanical, magnetic, thermal, or electrical forces [...]