Comparison of the Experimental Behavior of a Shape Memory Alloy in Compression and Tension

Aerospace ◽  
2003 ◽  
Author(s):  
Tobias Hesse ◽  
Mehrdaad Ghorashi ◽  
Daniel J. Inman
Keyword(s):  
Shape Memory Alloy ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Material Properties ◽  
Tensile Loading ◽  
Theoretical Models ◽  
Compression Tests ◽  
Stress Strain ◽  
Tensile Forces ◽  
Tension And Compression

The concept of Shape Memory Alloy (SMA) has been a subject of extensive research in the recent few years. In many SMA applications, wire elements have been used in order to control structural specifications like shape and stiffness. Since a wire can only be subjected to tensile forces, the available theoretical models for DMA discuss only the tensile loading. The present paper is an endeavor to overcome this shortcoming. It gives experimental resluts for tension and compression tests on specimens (having different geometries) made of an identical shape memory alloy. The corresponding results are compared with each other. Using stress-strain diagrams, several important material properties are obtained. These parameters can then be implemented in SMA models in order to analyze and predict the mechanical behavior of SMA elements subjected to compression.

Design, analysis, and manufacture of a tension–compression self-centering damper based on energy dissipation of pre-stretched superelastic shape memory alloy wires

2017 ◽  
Vol 28 (15) ◽  
pp. 2129-2139 ◽  
Author(s):  
Amin Alipour ◽  
Mahmoud Kadkhodaei ◽  
Mohsen Safaei
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Damping Ratio ◽  
Dissipated Energy ◽  
Damping Capacity ◽  
Compression Tests ◽  
Mechanical Unloading ◽  
Tension And Compression ◽  
The Individual

Superelastic shape memory alloys dissipate significant amount of energy since they recover large transformation strains upon mechanical unloading. Due to their dissipation properties, shape memory alloys can be effectively employed as dampers. Design, simulation, and fabrication of a newly developed superelastic shape memory alloy damper are discussed in this article. To enhance the stroke and dissipation capacity of the proposed damper, a system is implemented which operates more efficiently than a single shape memory alloy wire. Although shape memory alloy wires can only undergo tension, the new system enables the damper to be loaded in both tension and compression. Two damping groups are employed in this mechanism: one of which is activated during tension and the other is activated during compression of the damper. Each damping group consists of two shape memory alloy wires acting in the opposite directions to increase the damping capacity of the system. The mechanical responses of the individual components as well as the assembled damper are simulated. The predicted performance of the damper is then validated through tension/compression tests on the fabricated sample. Numerical and experimental force–displacement curves are also shown to be in a good agreement. The effect of different parameters on damping ratio and dissipated energy of the presented damper is investigated.

Rate-Dependent Damping Capacity of NiTi Shape Memory Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 37-42 ◽  
Author(s):  
Yong Jun He ◽  
Qing Ping Sun
Keyword(s):  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Strain Curve ◽  
Tensile Loading ◽  
Niti Shape Memory Alloy ◽  
Damping Capacity ◽  
Environmental Condition ◽  
Mechanical Coupling ◽  
Rate Dependent

High damping capacity is one of the prominent properties of NiTi shape memory alloy (SMA), having applications in many engineering devices to reduce unwanted vibrations. Recent experiments demonstrated that, the hysteresis loop of the stress-strain curve of a NiTi strip/wire under a tensile loading-unloading cycle changed non-monotonically with the loading rate, i.e., a maximum damping capacity was obtained at an intermediate strain rate (ε.critical). This rate dependence is due to the coupling between the temperature dependence of material’s transformation stresses, latent-heat release/absorption in the forward/reverse phase transition and the associated heat exchange between the specimen and the environment. In this paper, a simple analytical model was developed to quantify these thermo-mechanical coupling effects on the damping capacity of the NiTi strips/wires under the tensile loading-unloading cycle. We found that, besides the material thermal/mechanical properties and specimen geometry, environmental condition also affects the damping capacity; and the critical strain rate ε.criticalfor achieving a maximum damping capacity can be changed by varying the environmental condition. The theoretical predictions agree quantitatively with the experiments.

Anomalous stress-strain behavior of NiTi shape memory alloy close to the border of superelastic window

2021 ◽  
Vol 204 ◽  
pp. 114135
Author(s):  
Xiebin Wang ◽  
Xiayang Yao ◽  
Dominique Schryvers ◽  
Bert Verlinden ◽  
Guilong Wang ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Niti Shape Memory Alloy ◽  
Stress Strain ◽  
Strain Behavior

Analysis and Design of a Shape Memory Alloy Actuated Arm to Replicate Human Biomechanics

2016 ◽  
Author(s):  
Cody Wright ◽  
Onur Bilgen
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Biceps Brachii ◽  
Characteristic Curve ◽  
Stress Strain ◽  
Analysis And Design ◽  
Human Arm ◽  
Linear Spring ◽  
Mechanism Kinematic

Shape memory alloy actuators paired in an antagonistic arrangement can be used to produce mechanisms that replicate human biomechanics. To investigate this proposal, the biomechanical articulation of the elbow by means of the biceps brachii muscle are compared with that of a shape memory alloy actuated arm. Initially, the movement of the human arm is modeled as a single degree of freedom rocker-slider mechanism. Using this model, a purely kinematical analysis is performed on the rigid body rocker-slider. Force analysis follows by modeling the muscle as a simple linear spring. Torque, rocking angle, and energy are calculated for a range of rocker-slider geometries. Actuator characterization of the SMA wire is conducted by experimentally determining the stress-strain curves for the martensite detwinned and full austenite states. Using the experimentally obtained stress-strain curves, nonlinear and linear theoretical actuator characteristic curves are produced for the isolated SMA wire. Using the theoretical actuator characteristic curve on the rocker-slider mechanism, kinematic and force analyses are performed for both the nonlinear and linear actuated mechanisms. To compare to biomechanics, a literature survey is performed on human musculotendon and skeletal lengths and introduced to the kinematic analysis. Examination of biological and mechanical results are then discussed.

Complex transformation field created by geometrical gradient design of NiTi shape memory alloy

2017 ◽  
Vol 10 (01) ◽  
pp. 1740011 ◽  
Author(s):  
Reza Bakhtiari ◽  
Bashir S. Shariat ◽  
Fakhrodin Motazedian ◽  
Zhigang Wu ◽  
Junsong Zhang ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Stress Gradient ◽  
Tensile Loading ◽  
Niti Shape Memory Alloy ◽  
Mechanical Behaviors ◽  
Modeling Framework ◽  
Complex Transformation ◽  
Pseudoelastic Behavior

Owing to geometrical non-uniformity, geometrically graded shape memory alloy (SMA) structures by design have the ability to exhibit different and novel thermal and mechanical behaviors compared to geometrically uniform conventional SMAs. This paper reports a study of the pseudoelastic behavior of geometrically graded NiTi plates. This geometrical gradient creates partial stress gradient over stress-induced martensitic transformation, providing enlarged stress controlling interval for shape memory actuation. Finite element modeling framework has been established to predict the deformation behavior of such structures in tensile loading cycles, which was validated by experiments. The modeling results show that the transformation mostly propagates along the gradient direction as the loading level increases.

Nickel–titanium shape memory alloy mechanical components produced by investment casting

2018 ◽  
Vol 29 (19) ◽  
pp. 3748-3757 ◽  
Author(s):  
Jackson de Brito Simões ◽  
Carlos José de Araújo
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Investment Casting ◽  
Mechanical Characterization ◽  
Nickel Titanium ◽  
Compression Tests ◽  
Thermoelastic Martensitic Transformation ◽  
Scanning Calorimetry ◽  
Helical Springs ◽  
Mechanical Components

This work aimed to produce mechanical components of nickel–titanium shape memory alloys using investment casting processes. Then, in order to validate processing, different designs of nickel–titanium shape memory alloy components as staple implants, Belleville springs, meshes, helical springs, screws and hexagonal honeycombs were produced and submitted to thermal and mechanical characterization. Thermoelastic martensitic transformation of the nickel–titanium shape memory alloy parts was determined by differential scanning calorimetry and electrical resistance with temperature, while the superelastic behaviour was verified by cyclic tensile and compression tests. It has been demonstrated that the employed investment casting processes are suitable to manufacture nickel–titanium shape memory alloy mechanical components with simple and complicated designs as well as functional properties related to phase transformation and superelasticity.

Superelastic response in 〈1 2 2〉-oriented single crystals of FeMnAlNi shape memory alloy in tension and compression

2018 ◽  
Vol 233 ◽  
pp. 195-198 ◽  
Author(s):  
V.V. Poklonov ◽  
Y.I. Chumlyakov ◽  
I.V. Kireeva ◽  
V.A. Kirillov
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Single Crystals ◽  
Tension And Compression
Sign in / Sign up

Export Citation Format

Share Document