scholarly journals Investigation of the Propagation of Stress Wave in Nickel-Titanium Shape Memory Alloys

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1215
Author(s):  
Yehui Cui ◽  
Xiangguo Zeng ◽  
Huayan Chen ◽  
Jun Chen ◽  
Fang Wang
Keyword(s):  
Phase Transition ◽  
Wave Propagation ◽  
Phase Transformation ◽  
Elastic Wave ◽  
Shape Memory ◽  
Wave Velocity ◽  
Stress Wave ◽  
Nickel Titanium ◽  
Plastic Wave ◽  
Transition Wave

Based on irreversible thermodynamic theory, a new constitutive model incorporating two internal variables was proposed to investigate the phase transformation and plasticity behavior in nickel-titanium (NiTi) shape memory alloys (SMAs), by taking into account four deformation stages, namely austenite elastic phase, phase transition, martensitic elastic phase, and plastic phase. The model using the material point method (MPM) was implemented by the FORTRAN code to investigate the stress wave and its propagation in a NiTi rod. The results showed that its wave propagation exhibited martensitic and austenitic elastic wave, phase transition wave, and plastic wave. However, a double-wave structure including the martensitic and austenitic elastic wave and plastic wave occurred when the martensitic elastic wave reached the phase transformation wave. Thus, the reflection wave at a fixed boundary exhibited a different behavior compared with the elastic one, which was attributed to the phase transition during the process of reflection. It was found that the stress increment was proportional to the velocity of phase transition wave after the stress wave reflection. In addition, the influences of loading direction and strain rate on the wave propagation were examined as well. It was found that the phase transition wave velocity increased as the strain rate increased. The elastic wave velocity of martensite under compressive conditions was larger than that under tensile loading. In contrast, the plastic wave velocity under compression was less than that subjected to the tensile load.

On the Optimal Damping of a Vibrating Shape Memory Alloy Rod

2002 ◽  
Vol 124 (2) ◽  
pp. 97-102 ◽  
Author(s):  
Eduard R. Oberaigner ◽  
Franz D. Fischer ◽  
Kikuaki Tanaka
Keyword(s):  
Phase Transformation ◽  
Shape Memory ◽  
Stress Wave ◽  
Constitutive Law ◽  
Major Area ◽  
Static Approximation ◽  
Smart Systems ◽  
Optimal Damping ◽  
Basic Equations ◽  
The One

Vibration damping through phase transformation is one major area of application of shape memory alloys in smart systems and structures. The authors of this study have shown in earlier publications, how damping of vibrating rods can be accomplished. This paper is an extension and generalization. On the one side it uses the proper description of the stress-wave phenomenon instead of a quasi-static approximation, on the other side it describes, how the damping could be optimized. The basic equations of the underlying mathematical model are the stress-wave equation, the heat conduction equation, a kinetic and a constitutive law as well as a condition to ensure maximal damping. The major results are the heating history, which governs the phase transformation, and the domain splitting along the rod into elastic and inelastic regions.

scholarly journals Phase transformation volume amplitude as a low-cycle fatigue indicator in nickel–titanium shape memory alloys

2020 ◽  
Vol 178 ◽  
pp. 442-446 ◽  
Author(s):  
Harshad M. Paranjape ◽  
Bill Ng ◽  
Ich Ong ◽  
Lot Vien ◽  
Christopher Huntley
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Low Cycle Fatigue ◽  
Nickel Titanium ◽  
Cycle Fatigue

Control of Wave Propagation in Periodic Composite Rods Using Shape Memory Inserts

1999 ◽  
Author(s):  
M. Ruzzene ◽  
A. Baz
Keyword(s):  
Wave Propagation ◽  
Phase Transformation ◽  
Elastic Modulus ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Longitudinal Wave ◽  
Design Parameters ◽  
Impedance Mismatch ◽  
Periodic Composite ◽  
Longitudinal Wave Propagation

Abstract Longitudinal wave propagation is controlled using shape memory inserts placed periodically along rods. The inserts act as sources of impedance mismatch with tunable characteristics. Such characteristics are attributed to the unique behavior of the shape memory alloy whereby the elastic modulus of the inserts can be varied up to three times as the alloy undergoes a phase transformation from martensite to austenite. With such controllable capability, the inserts can introduce the proper impedance mismatch necessary to impede the wave propagation along the rods. An analytical model is presented to study the attenuation capabilities of the composite rods and to determine the influence of the various design parameters of the inserts that can control the width of the pass and stop-bands. The numerical results demonstrate the potential of shape memory alloys in controlling the dynamics of wave propagation in rods. Furthermore, the obtained results provide a guideline for designing inserts that are capable of filtering out selected excitation frequencies through proper adjustment of the geometry of the inserts as well as their activation strategies.

scholarly journals Characterization Techniques of a Shape Memory Nickel Titanium Alloy

Proceedings ◽  
2020 ◽  
Vol 38 (1) ◽  
pp. 15
Author(s):  
Andrade ◽  
Soares ◽  
Nobrega ◽  
Hilário ◽  
Santos
Keyword(s):  
Differential Scanning Calorimetry ◽  
Titanium Alloy ◽  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Tensile Tests ◽  
Metallic Alloys ◽  
Nickel Titanium ◽  
Metallographic Analysis ◽  
Scanning Calorimetry

This paper presents a characterization processes study of metallic alloys, more specifically the shape memory alloys (SMA) composed by Nickel and Titanium (NiTinol). Two different wire suppliers were studied, starting with metallographic analysis until observe the contours of the grain wires. Differential scanning calorimetry (DSC) test was also performed to obtain phase transformation temperatures of the NiTinol alloys. Finally, after several tensile tests, some results were obtained for stresses, strains, elasticity modules and maximum rupture deformation.

scholarly journals Mathematical modelling of elastoplasticity at high stress

2012 ◽  
Vol 468 (2148) ◽  
pp. 3842-3863 ◽  
Author(s):  
P. D. Howell ◽  
H. Ockendon ◽  
J.R. Ockendon
Keyword(s):  
Mathematical Model ◽  
Wave Propagation ◽  
Elastic Wave ◽  
Wave Speed ◽  
High Stress ◽  
Plastic Wave ◽  
Simple Mathematical Model ◽  
One Dimensional ◽  
Plastic Compression ◽  
Elastoplastic Wave

This study describes a simple mathematical model for one-dimensional elastoplastic wave propagation in a metal in the regime where the applied stress greatly exceeds the yield stress. Attention is focused on the increasing ductility that occurs in the over-driven limit when the plastic wave speed approaches the elastic wave speed. Our model predicts that a plastic compression wave is unable to travel faster than the elastic wave speed, and instead splits into a compressive elastoplastic shock followed by a plastic expansion wave.

Experimental Investigation and Numerical Simulation of the Mechanical and Thermal Behavior of a Superelastic Shape Memory Alloy Beam During Bending

2014 ◽  
Author(s):  
Johannes Ullrich ◽  
Marvin Schmidt ◽  
Andreas Schütze ◽  
André Wieczorek ◽  
Jan Frenzel ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Phase Transformation ◽  
Thermal Behavior ◽  
Shape Memory ◽  
High Speed ◽  
Nickel Titanium ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation ◽  
Research Association ◽  
Restoring Force

Superelastic Shape Memory Alloys (SMA) are typically used in applications where the martensitic phase transformation is exploited for its reversible, large deformation such as medical applications (e.g. stents). In this work, we focus on the mechanical and thermal behavior of a Nickel-Titanium SMA strip in bending mode. One possible application of this mode is to provide a restoring force when used in joints of SMA wire actuator systems making the need for an antagonistic SMA actuator redundant. In these applications mentioned above, typically only the mechanical properties are of interest while the temperature is considered constant, even though the martensitic phase transformation in SMA is a thermo-mechanically coupled process. As a part of the DFG (German Research Association) Priority Programme SPP1599 “Ferroic Cooling” which aims at advancing the development of solid state cooling devices, we have an equally large interest for the thermal evolution of Nickel-Titanium SMA during deformation and its induced phase transformation. In this paper we investigate the thermal and the mechanical response of a SMA beam during bending experiments in which the deformation is induced by holding one end of a SMA strip fixed while the other end is subject to a prescribed deflection. Sensors and high speed thermal cameras are used to capture reaction forces, deformations and temperature changes. We compare these experimental results with numerical simulation results obtained from Finite Element simulations where a thermo-mechanically coupled SMA model is implemented into a finite deformation framework.

Maximum Attainable Deflections of Shape Memory Alloy-Layered Microcantilever

2008 ◽  
Vol 5 (2) ◽  
pp. 52-61
Author(s):  
P. Majumder ◽  
A. Bhattacharyya
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Case Analysis ◽  
Nickel Titanium ◽  
Surveillance Systems ◽  
Computational Results ◽  
Heating And Cooling ◽  
Out Of Plane ◽  
Cantilever Surface

Finite element modeling of a shape memory alloy (SMA)-layered microcantilever is reported herein. It is assumed that the SMA layer is “two-way–trained,” such that alternate heating and cooling of the SMA layer will cause a phase transformation in the SMA layer and deform the cantilever out-of-plane and back. For a nickel–titanium (NiTi) layer on a glass substrate, computational results indicate that a uniform 4% two-way strain along the length of a SMA layer spanning the full length of a 100-μm cantilever translates to a tip deflection of 29.5 μm, and a sweep of approximately 30° from the flat “rest” state. As well, 40% of the cantilever surface (measured from its free end) is flat and can be used as a flat reflective surface for micromirror applications. A “worse-case” analysis is presented where only 50% of the SMA length is able to undergo phase transformation, resulting in deflections of about 10 μm with a 12° sweep. Finally, it is shown that deflections are about two orders of magnitude higher than what would be possible if the SMA layer did not undergo phase transformations (but underwent pure thermal expansion only). One possible area of application could be in the area of continuously rotating micromirrors, suitable for surveillance systems.

Primary Design of a Shape Memory Alloy Expandable Insert to Enhance Pedicle Screw Performance

2009 ◽  
Author(s):  
Maiid Tabesh ◽  
Mohammad Elahinia
Keyword(s):  
Corrosion Resistance ◽  
Phase Transformation ◽  
Shape Memory ◽  
Nickel Titanium ◽  
Damping Capacity ◽  
Specific Level ◽  
The Past ◽  
Niti Sma ◽  
Mechanical Deformations ◽  
Biomedical Fields

Shape Memory Alloys, such as Nickel Titanium, undergo a phase transformation in their crystalline structure when transformed from Austenite into Martensite. This inherent phase transformation is the basis for the unique properties of shape memory and superelasticity. Shape memory is attributed to the recovery of large mechanically induced deformations upon raising the temperature upto a specific level (Af). The superelasticity is the ability of the material, at a temperature above Austenite start Af, to recover mechanical deformations upon unloading. Thanks to superelasticity, shape memory effect, high damping capacity, corrosion resistance and biocompatibility, NiTi SMA alloys gain researchers attention for implementation in biomedical fields for the past 40 years [1].

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