Experimental and numerical investigations of shape memory alloy helical springs (original) (raw)
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Shape memory alloy helical springs: modeling, simulation and experimental analysis
2009
Shape memory alloys (SMAs) are metallic materials that have the capability to recover its original shape eliminating residual deformations when subjected to adequate thermal process. This behavior is related to phase transformation induced by stress or temperature and several alloys present this behavior. During the phase transformation process of a SMA component, large loads and/or displacements can be generated in a relatively short period of time making this component an interesting mechanical actuator. Because of such remarkable properties, SMAs have found a number of applications in different areas. The present contribution deals with the modeling, simulation and experimental analysis of SMA helical springs. Basically, it is assumed a one-dimensional constitutive model to describe its thermomechanical shear behavior and, afterwards, helical springs are modeled by considering classical approach. A numerical method based on the operator split technique is developed. SMA helical spring thermomechanical behavior is investigated through experimental tests performed at different loads. Numerical results show that the model is in close agreement with those obtained by experimental tests.
Shape Memory Alloy Helical Springs Performance: Modeling and Experimental Analysis
Materials Science Forum, 2013
Shape memory alloys (SMAs) are metallic materials that have the capability to recover its original shape eliminating residual strains when subjected to adequate thermal process. This behavior is related to phase transformation induced either by stress or by. During the phase transformation process of an SMA component, large loads and/or displacements can be generated in a relatively short period of time making this component an interesting mechanical actuator. Because of such remarkable properties, SMAs have found a number of applications in different areas. The present contribution deals with the modeling, simulation and experimental analysis of SMA helical springs. Basically, it is assumed a one-dimensional constitutive model to describe its thermomechanical shear behavior and, afterwards, helical springs are modeled by considering classical approach. SMA helical spring thermomechanical behavior is investigated through experimental tests performed at different loads. Numerical results show that the model is in close agreement with experimental data. Since the thermal process has an essential importance in the performance of an SMA actuator, different cooling medium conditions are investigated, evaluating the actuators performance.
Nonlinear geometric influence on the mechanical behavior of shape memory alloy helical springs
Smart Materials and Structures, 2015
This paper presents an investigation into shape memory alloy (SMA) springs considering the effects of geometry changes under small as well as large deformations. Helical springs were fabricated by shape setting of NiTi wires through heat treatment. The products exhibited pseudoelasticity at the ambient temperature, and their force-displacement responses were examined by performing simple tension tests. A model was further proposed to study tension and compression of SMA springs, and it was shown that the consequences of geometrical changes in tension and compression of springs are different. The numerical results of large and small deformation models were verified by experimental tensile results. In order to design a spring with maximum dissipative performance, a designer has three geometric parameters to set: wire diameter, spring diameter, and the number of active coils. The influences of these parameters on dissipated energy were studied in both displacement-and force-control loadings, and a framework for designing SMA springs with the purpose of achieving maximum applicable dissipation was at last developed.
Thermomechanical Analysis on Ti-Ni Shape Memory Helical Springs Under Cyclic Tensile Loads
Materials Research, 2015
Shape memory alloys (SMAs) present some characteristics, which make it unique material to be use in applications that require strength and shape recovery. This alloys was been used to manufacture smart actuators for mechanical industry devices and several other applications in areas as medicine, robotics, aerospace, petroleum and gas industries. However it is important to know the actuators response to external stimulus (heat source, electrical current and/or external stress) in these technological applications. This work investigated the thermomechanical behaviors of helical actuators produced from Ti-Ni alloy commercial wires. Initially, the wire was subjected to some heat treatment and characterized by differential scanning calorimeter (DSC), scanning electron microscopy (SEM), optical microscopy (OM) and Energy dispersive spectroscopy. Then two heat treatments were selected to obtain the helical actuators. The actuators were tested in an apparatus developed to apply an external traction stress in helical actuators during thermal cycles. Two wires were tested in a dynamic mechanical analyzer (DMA). The results were analyzed in comparison with thermoplastic properties obtained in thermomechanical tests. The analysis took into consideration the wiring forming process, the precipitates formation, the stress fields generated by dislocations and reorientation of martensite variants during the actuators training process.
On the design of a shape memory alloy spring actuator using thermal analysis
WSEAS TRANSACTIONS on SYSTEMS archive, 2008
Due to their unique properties and behavior, the Shape Memory Alloys (SMAs) play an increasingly important role in the intelligent systems performance. Recent applications in structural actuation and sensing demand increased material capabilities. This paper reviews the main advantages and the properties of SMAs and presents the design strategy for a typical shape memory actuator configuration of intelligent systems, using as active element Ni-Ti SMA spring working against a conventional steel spring. It also includes the thermal analysis experiments, in order to determine the transformation temperatures for the studied SMA spring. For design optimization a comprehensive graphical interface (based on the thermal analysis results), which runs under Visual Basic, has been developed for this application. It provides a user friendly environment allowing intelligent system parameters configuration as well as choosing the most adapted analysis methods and data displaying.
International Review of Applied Sciences and Engineering, 2022
Shape memory alloys are smart materials which have remarkable properties that promoted their use in a large variety of innovative applications. In this work, the shape memory effect and superelastic behavior of nickel-titanium helical spring was studied based on the finite element method. The three-dimensional constitutive model proposed by Auricchio has been used through the built-in library of ANSYS® Workbench 2020 R2 to simulate the superelastic effect and one-way shape memory effect which are exhibited by nickel-titanium alloy. Considering the first effect, the associated force-displacement curves were calculated as function of displacement amplitude. The influence of changing isothermal body temperature on the loading-unloading hysteretic response was studied. Convergence of the numerical model was assessed by comparison with experimental data taken from the literature. For the second effect, force-displacement curves that are associated to a complete one-way thermomechanical c...
Computational Materials Science, 2000
This paper analyzes and compares the predictions of two sharp phase-front based shape memory alloy (SMA) constitutive models – proposed by Abeyaratne and Knowles (R. Abeyaratne, J. Knowles, Journal of Mechanics and Physics of Solids 41 (1993) 541) and Bruno et al. (O. Bruno, P. Leo, F. Reitich, Phys. Rev. Lett. 74 (1995) 746–749) – in the context of an SMA linear actuator (an SMA rod or a wire) actuated electrically and subjected to spring-loaded boundary conditions at its ends. Both models are then used to analyze the performance – i.e., specific energy output and energy efficiency – of the SMA actuator. The computational modeling is done using a moving boundary finite element method (MBFEM)-based numerical approach proposed by Stoilov et al. (V. Stoilov, O. Iliev, A. Bhattacharyya, Computer Methods in Applied Mechanics and Engineering, accepted). It is seen that while both models produce somewhat differing predictions of the SMA response, the difference is not dramatic enough to prefer one model to another. Predictions of the SMA actuator performance indicate that there is an optimum spring stiffness at which the energy efficiency of the SMA actuator is at its maximum. This raises the possibility that when an SMA actuator is integrated into a structure, the passive components of the structure may play a key role in determining the optimum energy efficiency of the active structural component (the SMA actuator) during the activation of the structure.
Thermoelastic properties on Cu-Zn-Al shape memory springs
Materials Research, 2010
This paper present a thermomechanical study of actuators in form of helical springs made from shape memory alloy wires that can work as actuator and/or as sensor. These abilities are due to the martensitic transformation. This transformation is a diffusionless phase transition that occurs by a cooperative atomic rearrange mechanism. In this work, helical spring actuators were manufactured from Cu-Zn-Al shape memory alloy wires. The springs were submitted to constant tensile loads and thermal cycles. This procedure allows to determine thermoelastic properties of the shape memory springs. Thermomechanical properties were analyzed during 50 thermal cycles in the temperature range from 20 to 130 °C. Results of variations in critical transformation temperatures, thermoelastic strain and thermal hysteresis are discussed based on defects rearrangement and martensitic transformation theory.
Sensors, 2018
This paper proposes a new force-displacement model for superelastic shape memory alloy (SMA) springs under complex loading and unloading. For the SMA wires used to make superelastic springs, a new multilinear constitutive model based on a modification of the 1D Motahari model is developed. In the modified model, the stress-strain relation curves are changed to fit the experimental results. Furthermore, the established force-displacement relationship of the springs considers the impact of not only the torque but also the moment on the cross sections of the SMA wires. Afterwards, a series of tension tests are performed on four NiTi helical spring specimens under various loading conditions. From the numerical simulations and experimental results, it is shown that, compared with the force-displacement curves for the SMA springs simulated by the Motahari model, those simulated by the proposed model can better approximate the experimental results. The new model inherits the advantage of s...