Shape memory alloy based smart landing gear for an airship

The design and development of a shape memory alloy based smart landing gear for aerospace vehicles is based on a13; novel design approach. The smart landing gear comprises a landing beam, an arch, and a superelastic nickeltitanium shape memory alloy element. This design is of a generic nature and is applicable to a certain class of light13; aerospace vehicles. In this paper a specixFB01;c case of the shape memory alloy based smart landing gear design and13; development applicable to a radio controlled semirigid airship (radio controlled blimp) of 320 m3 volume is13; presented.Ajudicious combination of carbon xFB01;ber reinforced plastic for the landing beam, cane (naturally occurring13; plant product) wrapped with carbon xFB01;ber reinforced plastic for the arch, and superelastic shape memory alloy is13; used in the development. An appropriate sizing of the arch and landing beam is arrived at to meet the dual requirement of low weight and high-energy dissipation while ndergoing x201C;large elasticx201D; (large nonlinear recoverable13; elastic strain) deformations to ensure soft landings when the airship impacts the ground. The soft landing is required13; to ensure that shock and vibration are minimized (to protect the sensitive payload). The inherently large energydissipating character of the superelastic shape memory alloy element in the tensile mode of deformation and the superior elastic bounce back features of the landing gear provide the ideal solution.Anonlinear analysis based on the classical and xFB01;nite element method approach is followed to analyze the structure. Necessary experiments and tests have been conducted to check the veracity of the design. Good correlation has been found between the analyses and testing. This exercise is intended to provide an alternate method of developing an efxFB01;cient landing gear with satisfactory geometry for a x201C;certain class of light aerospace vehiclesx201D; such as airships, rotorcraft, and other light unmanned air vehicles

Effect of Geometry And Material on the Response of A Shape Memory Alloy (sma) Earthquake Damper

Shape memory alloys (SMAs), such as Nitinol (i.e., NiTi), are of numerous importance in engineering applications due to their exceptional superelasticity and shape memory properties. Applications of a Shape Memory Alloy (SMA) in alleviating the seismic vibration response of civil infrastructure is attaining momentum. “Shape Memory” indicates that the material recollects its original formed shape. SMA has two simple properties, Super-Elasticity and Shape Memory Effect (SME). The “Super-Elastic” behavior revealed by SMA materials, allows a full recovery of strains up to 8% from big cyclic deformations, whereas developing a hysteretic loop. SME permits the material to recover the primary shape which is considered as re-centering mechanism. The mechanism of shape recovery comprises two crystallographic phases, Martensite and Austenite, and the transformations amongst them. The Austenite phase offers more stiffness than the Martensite phase. Phase transformation happens among Martensite and Austenite subject upon temperature and stress. These exceptional properties result in high damping and repeatable re-centering abilities which is an advantage in several civil infrastructure applications, exclusively in seismic vibration control devices. In recent years, additive manufacturing (AM) processes have been used to produce complex NiTi components, which provide the ability to tailor microstructure and thus the critical properties of the alloys. SMAs have also been explored progressively by the earthquake engineering community, because of their extraordinary self-centering (SC) and energy-dissipating competences. This work analytically presents numerical investigations iv executed to comprehend the numerical behavior of an SMA damper. Part of the numerical model is assessed against an experimental result by Zhai et al. (2020) and exhibited reasonable accuracy. The SMA damper with SC function under monotonic, fatigue cyclic and quasi-static cyclic loading is presented. The numerical results demonstrate that outstanding and stable flag-shaped hysteresis loops are exhibited in multiple loading cycles, indicating good energy dissipation, large deformation and ductility abilities. The stress-strain states with dissimilar phase transformation are also discussed in this work

Seismic assessment of a benchmark highway bridge equipped with optimized shape memory alloy wire-based isolators

In this paper, an evolutionary multi-objective optimization algorithm named NSGA-II was used to determine the optimum radius for shape memory alloy (SMA) wires employed in conjunction with the lead rubber bearing (LRB), referred to as an SMA-LRB isolator. This algorithm simultaneously minimizes the mid-span displacement and the base shear force. Then, the optimized SMA-LRBs were implemented in a benchmark bridge to reduce excessive displacements. The results obtained from the nonlinear dynamic analysis show that the implemented approach could effectively optimize the SMA-LRBs. These improved smart isolators can noticeably reduce the maximum displacements and residual deformations of the structure; meanwhile, the base shear and deck acceleration remain less than those of the non-isolated benchmark bridge. This isolator can reduce the maximum mid-span displacement of the bridge by up to 61%, and the mid-span residual deformations by up to 100%, compared to an uncontrolled isolated bridge under different ground motions. This optimized passive system was compared with nonlinear dampers, passive SMA dampers, and a negative stiffness device. The results indicate that the optimized SMA-LRB isolators are generally more successful in reducing and recovering displacements than the other controllers

Finite element modeling and simulation of a robotic finger actuated by Ni-Ti shape memory alloy wires

In this paper, a dynamic model for an artificial finger driven by Shape Memory Alloy (SMA) wires is presented. Due to their high energy density, these alloys permit the realization of highly compact actuation solutions with potential applications in many areas of robotics, ranging from industrial to biomedical ones. Despite many advantages, SMAs exhibit a highly nonlinear and hysteretic behavior which complicates system design, modeling, and control. In case SMA wires are used to activate complex robotic systems, the further kinematic nonlinearities and contact problems make the modeling significantly more challenging. In this paper, we present a finite element model for a finger prototype actuated by a bundle of SMA wires. The commercially available software COMSOL is used to couple the finger structure with the SMA material, described via the Muller-Achenbach-Seelecke model. By means of several experiments, it is demonstrated how the model reproduces the finger response for different control inputs and actuator geometries

Application and modelling of shape-memory alloys for structural vibration control : state-of-the-art review

One of the most essential components of structural design for civil engineers is to build a system that is resistant to environmental conditions such as harsh chemical environments, and catastrophic disasters like earthquakes and hurricanes. Under these circumstances and disturbances, conventional building materials such as steel and concrete may demonstrate inadequate performance in the form of corrosion, deterioration, oxidizing, etc. Shape Memory Alloys (SMAs) are novel metals with distinct features and desirable potential to overcome the inadequacies of existing construction materials and enable the structure to tolerate disturbances more efficiently. Shape Memory Effect (SME) and Pseudoelasticity (PE) have been the most attractive characteristics that scientists have focused on among the various features that SMAs exhibit. The SME enables the material to retain its original shape after severe deformation, whereas the PE behaviour of SMAs provides a wide range of deformation while mitigating a substantial amount of susceptible stresses. These behaviours are the consequence of the phase transformation between austenite and martensite. Many investigations on the modelling and application of SMAs in structural systems to endure applied dynamic loadings in the form of active, passive, and hybrid vibration control systems have been undertaken. The focus of this paper is to present an overview of the SMA-based applications and most frequently employed constitutive modelling, as well as their limits in structural vibration control and seismic isolation devices

Explicit finite element implementation of a shape memory alloy constitutive model and associated analyses

Shape memory alloys (SMA) represent an important class of smart metallic materials employed in various innovative applications thanks to their unique thermomechanical behavior. Since the 1980s, several SMA constitutive models have been proposed and implemented into both commercial and academic finite element analysis software tools. Such models have demonstrated their reliability and robustness in the design and optimization of a wide variety of SMA-based components. However, most models are implemented using implicit integration schemes, thus limiting their applicability in highly nonlinear analyses. The objective of this work is to present a novel explicit integration scheme for the numerical implementation of the three-dimensional Souza-Auricchio model, a phenomenological model able to reproduce the primary SMA responses (i.e., pseudoelasticity and shape memory effect). The model constitutive equations are formulated by adopting the continuum thermodynamic theory with internal variables, following a plasticity-like approach. An elastic predictor-inelastic corrector scheme is here used to solve the time-discrete non-linear constitutive equations in the explicit framework. The proposed algorithm is investigated through several benchmark boundary-value problems of increasing complexity, considering both pseudoelastic and shape memory response in quasi-static conditions; a comparison with an implicit integration scheme is also performed. Such numerical tests demonstrate the ability of the algorithm to reproduce key material behaviors with effectiveness and robustness. Particularly, the analysis of SMA cables demonstrates the effectiveness of the explicit algorithm to solve complex problems involving widespread nonlinear contact, which prevent the convergence of the implicit scheme. Details such as mass-scaling options are also discussed

Numerical analysis of complex systems evolution with phase transformations at different spatial scales

This paper shows the existence of a critical dimension for finite length nanowires exhibiting shape memory effects. We give a brief survey of phase transformations, their classifications, and provide the basis of mathematical models for the phenomena involving such transformations, focusing on shape memory effects at the nanoscale. Main results are given for the dynamic of square-to-rectangular transformations modelled on the basis of the modified Ginzburg-Landau theory. The results were obtained by solving a fully coupled system of partial differential equations, accounting for the thermal field, a feature typically neglected in recent publications on the subject when microstructures of nanowires were modelled with phase-field approximations. Representative examples are shown for nanowires of length 2000nm and widths ranging from 200nm to 50nm. The observed microstructure patterns are different from the bulk situation due to the fact that interfacial energy becomes comparable at the nanoscale with the bulk energy