Bending of Superelastic Shape Memory Alloy Tubes

2011 ◽  
Author(s):  
Benjamin Reedlunn ◽  
Christopher Churchill ◽  
Emily Nelson ◽  
Samantha Daly ◽  
John Shaw
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Mechanical Response ◽  
Surface Displacement ◽  
Beam Theory ◽  
Image Correlation ◽  
Reasonable Assumption ◽  
Significant Shift ◽  
Localized Deformation ◽  
Tension And Compression

Many shape memory alloy (SMA) applications exploit superelasticity in a bending mode, yet the large displacements and rotations associated with bending of slender structures make controlled experiments difficult. A custom pure bending fixture was built to perform experiments on superelastic NiTi tubes. To understand the bending results, the tubes were also characterized in uniaxial tension and compression, where a custom fixture was utilized to avoid buckling. In addition to measuring the global mechanical response, stereo digital image correlation (DIC) was used in all the experiments to capture the local surface displacement and strain fields. Consistent with the tension/compression data, our bending experiments showed a significant shift of the neutral axis towards the compression side. Also, the tube had strain localization on the tension side, but no such localization on the compression side. Detailed analysis of the strain distribution across the tube diameter revealed that the usual assumption of beam theory, that plane sections remain plane, did not hold along the tension side. Averaged over a few diameters of gage length, plane sections remain plane is a reasonable assumption and can be used to predict the global moment–curvature response. However, this assumption should be used with caution since it can under/over predict local strains by as much as 2× due to the localized deformation morphology.

Shape Memory Alloy Cables for Civil Infrastructure Systems

2014 ◽  
Author(s):  
Sherif Daghash ◽  
Osman E. Ozbulut ◽  
Muhammad M. Sherif
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Mechanical Response ◽  
Civil Engineering ◽  
Large Diameter ◽  
Small Diameter ◽  
Image Correlation ◽  
Temperature Fields ◽  
Uniaxial Tensile ◽  
Civil Infrastructure

Shape memory alloys (SMAs) have attracted a great deal of attention as a smart material that can be used in various civil engineering applications due to their favorable mechanical properties such as ability to undergo large deformations, high corrosion and fatigue resistance, good energy dissipating capacity, and excellent re-centering ability. In contrast to the use of SMAs in the biomedical, mechanical and aerospace applications, which requires mostly small diameter of material, the larger size bars are usually needed in a civil engineering application. It is well known that properties of large-section SMA bars are generally poorer than those of wires due to difficulties in material processing. Furthermore, large diameter SMA bars are more expensive than thin SMA wires. Shape memory alloy cables have been recently developed as an alternative and new structural element. They leverage the superior mechanical characteristics of small diameter SMAs into large-size structural tension elements and possess several advantages over SMA bars. This study explores the performance of NiTi SMA cables and their potential use in civil engineering. The SMA cable, which has a diameter of 8 mm, is composed of 7 strands and each strand has 7 wires with a diameter of 0.885 mm. The uniaxial tensile tests are conducted at various loading rates and strain amplitudes to characterize the superelastic properties of the SMA cable and study the rate-dependent mechanical response of the SMA cable under dynamic loads. An optical digital image correlation measurement system and an infrared thermal imaging camera are employed to obtain the full-field strain and temperature fields. Potential applications of SMA cables in civil infrastructure applications are discussed and illustrated.

A model for shape memory alloy beams accounting for tensile compressive asymmetry

2019 ◽  
Vol 30 (18-19) ◽  
pp. 2697-2715 ◽  
Author(s):  
Nguyen Van Viet ◽  
Wael Zaki ◽  
Ziad Moumni
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Solid Phase ◽  
Constitutive Relations ◽  
Beam Theory ◽  
Element Analysis ◽  
Proposed Model ◽  
The Finite Element Analysis ◽  
Tension And Compression ◽  
Asymmetric Shape

A new analytical model is derived for cantilever beams made from superelastic shape memory alloy and subjected to tip load. The deformation of the beam is described based on Timoshenko beam theory using constitutive relations that account for asymmetric shape memory alloy response in tension and compression. Analytical moment and shear force equations are developed and the position of the neutral axis and the different solid phase regions in the beam are tracked throughout a full loading–unloading cycle. Validation of the proposed model is carried out against data from the literature and from the finite element analysis considering tensile–compressive asymmetry in shape memory alloy behavior.

An Experimental Setup for Measuring Unstable Thermo-Mechanical Behavior of a Shape Memory Alloy Wire

2000 ◽  
Author(s):  
Mark A. ladicola ◽  
John A. Shaw
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Mechanical Response ◽  
Infrared Imaging ◽  
Temperature Fields ◽  
Critical Parameters ◽  
Ambient Conditions ◽  
Stress Concentrations ◽  
Localized Deformation ◽  
Full Field

Abstract An experimental arrangement is demonstrated that overcomes some difficulties in thermo-mechanical testing of thin Shape Memory Alloy (SMA) wires under uniaxial tension. It is now well known that stress-induced transformations in some SMAs under uniaxial loading can lead to mechanical instabilities and propagating phase transformation fronts. Critical parameters, such as nucleation barriers are difficult to measure by conventional testing techniques and are often masked by unavoidable stress concentrations at grips. In addition, simultaneous full field measurements of localized deformation and temperature fields are difficult to obtain for different ambient conditions. The current scheme uses a temperature-controlled conduction block and a non-uniform temperature field induced by thermoelectric modules to uncover the underlying thermo-mechanical response of the wire. The approach also allows access for optical and infrared imaging of the specimen deformation and temperature fields.

scholarly journals Effect of strain rate on strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy

2021 ◽  
Vol 250 ◽  
pp. 05012
Author(s):  
Sebastian Henschel ◽  
Lutz Krüger
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Image Correlation ◽  
Coarse Grained ◽  
Strain Rates ◽  
Localized Deformation ◽  
Strength And Deformation

The strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy at different strain rates was studied. Furthermore, the effect of grain size was investigated. To this end, a batch with bamboo-like grain arrangement and a batch with smaller, nevertheless coarse, grains were analyzed. Tensile tests at quasi-static, intermediate, and dynamic loading rates were performed. Digital image correlation and microstructural analysis revealed the localized deformation and phase transformation in favorable oriented grains. At higher strain rates, a increased number of orientations was activated for the phase transformation. A higher strain rate resulted in an increased strength for the coarse-grained material while the bamboo-like material did not show this effect. The analysis of fracture surfaces revealed ductile fracture and cleavage fracture for all strain rates.

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

scholarly journals Deformation Behavior of a Shape Memory Alloy: Nitinol

2008 ◽  
Author(s):  
Samantha Daly ◽  
Kaushik Bhattacharya ◽  
Guruswami Ravichandran
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Rolling Texture ◽  
Image Correlation ◽  
Space Applications ◽  
Deformation And Failure ◽  
Full Field ◽  
New Information ◽  
Macro Scale ◽  
First Time

Nickel-Titanium, commonly referred to as Nitinol, is a shape-memory alloy with numerous applications due to its superelastic nature and its ability to revert to a previously defined shape when deformed and then heated past a set transformation temperature. While the crystallography and the overall phenomenology are reasonably well understood, much remains unknown about the deformation and failure mechanisms of these materials. These latter issues are becoming critically important as Nitinol is being increasingly used in medical devices and space applications. The talk will describe the investigation of the deformation and failure of Nitinol using an in-situ optical technique called Digital Image Correlation (DIC). With this technique, full-field quantitative maps of strain localization are obtained for the first time in thin sheets of Nitinol under tension. These experiments provide new information connecting previous observations on the micro- and macro-scale. They show that martensitic transformation initiates before the formation of localized bands, and that the strain inside the bands does not saturate when the bands nucleate. The effect of rolling texture, the validity of the widely used resolved stress transformation criterion, and the role of geometric defects are examined.

Dynamic analysis of a shape memory alloy beam with pseudoelastic behavior

2018 ◽  
Vol 29 (9) ◽  
pp. 1835-1849 ◽  
Author(s):  
Reza Razavilar ◽  
Alireza Fathi ◽  
Morteza Dardel ◽  
Jamal Arghavani Hadi
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Frequency Response ◽  
Kinetic Equations ◽  
Elastic Beam ◽  
Beam Theory ◽  
Response Analysis ◽  
Interesting Phenomenon ◽  
Time Saving ◽  
Solution Approach

This article aims at developing a semi-analytic approach for studying the free and forced vibrations of a pseudoelastically behaving shape memory alloy beam. Based on the Euler–Bernoulli beam theory, equations of motion were derived through Hamilton principle, and the obtained partial differential equations were decomposed by applying the Galerkin approach and were solved using Newmark integration method. A three-dimensional phenomenological model of shape memory alloy, which is capable of identifying the main properties of the shape memory alloy, was employed to model the behavior of the shape memory alloy beam. A closed-form numerical algorithm was introduced to simulate the governing kinetic equations of the shape memory alloy beam coupled with transformation strain. The presented novel solution approach is simple, flexible, and time-saving. Stability analysis was performed using phase state trajectories to show dynamic characteristics of the shape memory alloy beam. Due to hysteric behavior of the shape memory alloy, energy dissipation was clearly observed in early stages of the free vibration and within the transient regions of the forced vibration. The numerical results showed that, due to the hysteric induced damping effect, the vibration amplitude is smaller in comparison to an equivalent elastic beam, and consequently, the shape memory alloy beam exhibits more stable behavior at the resonant frequencies. This property can potentially find applications in energy damping applications and vibration control. Moreover, an interesting phenomenon called jumping was observed in the results of frequency response analysis. At jumping frequency, the amplitude of the frequency response has two distinct levels. This jumping frequency is as a result of the hysteresis behavior of the shape memory alloy, and it is a function of the exciting amplitude.

scholarly journals Modeling the behavior of bilayer shape memory alloy/functionally graded material beams considering asymmetric shape memory alloy response

2019 ◽  
Vol 31 (1) ◽  
pp. 84-99 ◽  
Author(s):  
Nguyen Van Viet ◽  
Wael Zaki ◽  
Rehan Umer ◽  
Quan Wang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Functionally Graded Material ◽  
Three Dimensional ◽  
Laminated Composite ◽  
Alloy Layer ◽  
Functionally Graded ◽  
Tension And Compression ◽  
Graded Material ◽  
Asymmetric Shape

A new model is proposed to describe the response of laminated composite beams consisting of one shape memory alloy layer and one functionally graded material layer. The model accounts for asymmetry in tension and compression of the shape memory alloy behavior and successfully describes the dependence of the position of the neutral surface on phase transformation within the shape memory alloy and on the load direction. Moreover, the model is capable of describing the response of the composite beam to both loading and unloading cases. In particular, the derivation of the equations governing the behavior of the beam during unloading is presented for the first time. The effect of the functionally graded material gradient index and of temperature on the neutral axis deviation and on the overall behavior of the beam is also discussed. The results obtained using the model are shown to fit three-dimensional finite element simulations of the same beam.

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