Wave Propagation in a Shape Memory Alloy Bar Under an Impulsive Loading

2016 ◽  
Vol 83 (10) ◽  
Author(s):  
Pingping Zhu ◽  
Hui-Hui Dai
Keyword(s):  
Wave Propagation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Wave Structure ◽  
Impulsive Loading ◽  
Wave Patterns ◽  
Elastic Shock ◽  
Loading And Unloading ◽  
Impact Phase ◽  
The Impact

We analyze wave propagation in a semi-infinite shape memory alloy (SMA) bar under a rectangular impulsive loading. Different trilinear up–down–up nominal stress–strain curves for loading and unloading processes are adopted to complete the dynamical system. The chord criterion (equivalent to maximally dissipative kinetics) is employed to single out the unique solution for the impact problem. The interactions among discontinuities (loading/unloading elastic shock waves and phase boundaries) can yield some complicated wave structure. In particular, it is found that the encounter of the unloading elastic shock wave and the loading phase boundary can yield three different wave patterns depending on the level of impact stress, which are different from those for a hardening response studied in the literature. Solutions in the whole temporal and spatial domain are obtained, which reveal interesting wave structures induced by two different levels of impact. Phase transformation regions and tension/compression regions are also determined. The results also suggest that the SMAs can be used for impact-protection purpose effectively.

Wave propagation in shape memory alloy rods under impulsive loads

2005 ◽  
Vol 461 (2064) ◽  
pp. 3871-3892 ◽  
Author(s):  
Yi-Chao Chen ◽  
Dimitris C Lagoudas
Keyword(s):  
Wave Propagation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Wave Front ◽  
Impact Load ◽  
Reverse Transformation ◽  
Loading Function ◽  
Unloading Wave ◽  
The Impact ◽  
Elastic Unloading

A dynamic analysis is given of the wave propagation in a polycrystalline shape memory alloy semi-infinite rod subject to an impulsive load described by a rectangular loading function. This is a continuation of the previous study for which the impact load is described by a step loading function, and for which the rod undergoes martensitic phase transformation only. In the presence of unloading, the rod also undergoes reverse transformation from martensite to austenite. A maximum internal dissipation criterion is proposed to select a unique dynamic solution, in which an elastic unloading wave front precedes the reverse transformation wave front. This elastic unloading wave will meet with the forward transformation wave at a later time, leading to a sequence of wave encounters and progressively more complicated profiles of the state variables. The asymptotic behaviour of the solution and the energy dissipation are discussed.

Design and Optimization of a Shape Memory Alloy-Based Self-Folding Sheet

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Edwin Peraza-Hernandez ◽  
Darren Hartl ◽  
Edgar Galvan ◽  
Richard Malak
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Three Dimensional ◽  
Building Blocks ◽  
Passive Layer ◽  
Von Mises Stress ◽  
Maximum Temperature ◽  
Radius Of Curvature ◽  
Folding Angle ◽  
The Impact

Origami engineering—the practice of creating useful three-dimensional structures through folding and fold-like operations on two-dimensional building-blocks—has the potential to impact several areas of design and manufacturing. In this article, we study a new concept for a self-folding system. It consists of an active, self-morphing laminate that includes two meshes of thermally-actuated shape memory alloy (SMA) wire separated by a compliant passive layer. The goal of this article is to analyze the folding behavior and examine key engineering tradeoffs associated with the proposed system. We consider the impact of several design variables including mesh wire thickness, mesh wire spacing, thickness of the insulating elastomer layer, and heating power. Response parameters of interest include effective folding angle, maximum von Mises stress in the SMA, maximum temperature in the SMA, maximum temperature in the elastomer, and radius of curvature at the fold line. We identify an optimized physical realization for maximizing folding capability under mechanical and thermal failure constraints. Furthermore, we conclude that the proposed self-folding system is capable of achieving folds of significant magnitude (as measured by the effective folding angle) as required to create useful 3D structures.

scholarly journals Ni-Ti Shape Memory Alloy Coatings for Structural Applications: Optimization of HVOF Spraying Parameters

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Carmen De Crescenzo ◽  
Despina Karatza ◽  
Dino Musmarra ◽  
Simeone Chianese ◽  
Theocharis Baxevanis ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Large Scale ◽  
Thermal Spray Technology ◽  
Spray Parameters ◽  
Hvof Spraying ◽  
Structural Applications ◽  
External Stimuli ◽  
Steel Substrates ◽  
The Impact

This work aims at contributing to the development of a revolutionary technology based on shape memory alloy (SMA) coatings deposited on-site to large-scale metallic structural elements, which operate in extreme environmental conditions, such as steel bridges and buildings. The proposed technology will contribute to improve the integrity of metallic civil structures, to alter and control their mechanical properties by external stimuli, to contribute to the stiffness and rigidity of an elastic metallic structure, to safely withstand the expected loading conditions, and to provide corrosion protection. To prove the feasibility of the concept, investigations were carried out by depositing commercial NiTinol Ni50.8Ti (at.%) powder, onto stainless steel substrates by using high-velocity oxygen-fuel thermal spray technology. While the NiTinol has been known since decades, this intermetallic alloy, as well as no other alloy, was ever used as the SMA-coating material. Due to the influence of dynamics of spraying and the impact energy of the powder particles on the properties of thermally sprayed coatings, the effects of the main spray parameters, namely, spray distance, fuel-to-oxygen feed rate ratio, and coating thickness, on the quality and properties of the coating, in terms of hardness, adhesion, roughness, and microstructure, were investigated.

Effect of superelastic shape memory alloy wires on the impact behavior of carbon fiber reinforced in situ polymerized poly(butylene terephthalate) composites

2011 ◽  
Vol 65 (5) ◽  
pp. 863-865 ◽  
Author(s):  
J. Aurrekoetxea ◽  
J. Zurbitu ◽  
I. Ortiz de Mendibil ◽  
A. Agirregomezkorta ◽  
M. Sánchez-Soto ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Impact Behavior ◽  
Fiber Reinforced ◽  
Butylene Terephthalate ◽  
Carbon Fiber Reinforced ◽  
The Impact

scholarly journals OPTIMIZATION OF NICKEL CONTENT ON SOME PROPERTIES OF (NITI) SHAPE MEMORY ALLOY

2020 ◽  
Vol 1 (01) ◽  
pp. 40-47
Author(s):  
Aissa Bouaissi ◽  
Nabaa S Radhi ◽  
Karrar F. Morad ◽  
Mohammad H. Hafiz ◽  
Alaa Abdulhasan Atiyah
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Smart Materials ◽  
Shape Recovery ◽  
Fatigue Behavior ◽  
Nickel Content ◽  
Functionally Graded ◽  
Niti Shape Memory Alloy ◽  
Shape Effect ◽  
The Impact

Shape Memory Alloys (SMAs) are one of the most hopeful smart materials, especially, Nickel–Titanium (NiTi or Nitinol). These alloys are great and desirable due to their excellent reliability and behavior among all the commercially available alloys. In addition, strain recovery, (Ni–Ti) is granulated for a wide variety of medical uses because of its favorite properties such as fatigue behavior, corrosion resistance and biocompatibility. This paper explores the creation and the characterization of functionally graded (NiTi) materials. This work demonstrations the impact of Nickel contains changes on the characteristics of NiTi shape memory alloy, in order to obtain the suitable addition of Nickel contain, which gives the optimal balance between hardness, start and finish martensitic point, shape recovery and shape effect of alloys properties. These materials are prepared to obtain suddenly or gradually microstructure or composition differences inside the structure of one piece of material, the specimens made by powder metallurgy process and the influence of every layer of composite by; micro-hardness, transformation temperature DSC and shape effect. The hardness value and shape recovery decrease with increase nickel content. superior shape memory effect (SME) and shape recovery (SR) properties (i.e., 8.747, 10.270 for SMA-FGM1 SMA-FGM2 respectively, and SR is 1.735, 2.977 for SMA-FGM1 SMA-FGM2) respectively.  

scholarly journals The low-velocity impact and compression after impact (CAI) behavior of foam core sandwich panels with shape memory alloy hybrid face-sheets

2019 ◽  
Vol 26 (1) ◽  
pp. 517-530 ◽  
Author(s):  
Ye Wu ◽  
Yun Wan
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sandwich Panels ◽  
Image Correlation ◽  
Low Velocity Impact ◽  
Foam Core ◽  
Low Velocity ◽  
Velocity Impact ◽  
Compression After Impact ◽  
The Impact

AbstractDue to the properties of shape memory effect and super-elasticity, shape memory alloy (SMA) is added into glass fiber reinforced polymer (GFRP) face-sheets of foam core sandwich panels to improve the impact resistence performance by many researchers. This paper tries to discuss the failure mechanism of sandwich panels with GF/ epoxy face-sheets embedded with SMA wires and conventional 304 SS wire nets under low-velocity impact and compression after impact (CAI) tests. The histories of contact force, absorbed energy and deflection during the impact process are obtained by experiment. Besides, the failure modes of sandwich panels with different ply modes are compared by visual inspection and scanning electron microscopy (SEM). CAI tests are conducted with the help of digital image correlation (DIC) technology. Based on the results, the sandwich panels embedded with SMA wires can absorb more impact energy, and show relatively excellent CAI performance. This is because the SMA wires can absorb and transmit the energy to the outer region of GFRP face-sheet due to the super-elasticity-behavior. The failure process and mechanism of the CAI test is also discussed.

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.

Proof-of-Concept of the Shape Memory Alloy ReseTtable Dual Chamber Lift Device for Pedestrian Protection With Tailorable Performance

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
James Otten ◽  
Jonathan Luntz ◽  
Diann Brei ◽  
Kenneth A. Strom ◽  
Alan L. Browne ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Internal Space ◽  
Operating Parameters ◽  
Proof Of Concept ◽  
Dual Chamber ◽  
Extrinsic Factors ◽  
On Line ◽  
The Impact ◽  
Crush Zone

As automobile use expands in population-dense cities across the world, there is a growing need for new approaches to mitigate the consequences to pedestrians of pedestrian/automotive collisions. This is especially challenging for passive approaches since there is an increasing internal space demand that reduces the crush zone between the relatively compliant hood and rigid underhood components. One unique approach is an active hood lift which raises the hood upon detection of a collision with a pedestrian to increase the crush zone. This approach is technically challenging due to the fast and accurate timing which is sensitive to extrinsic factors (including pedestrian height and weight and the need for reusable/automatically resettable functionality. This paper presents a novel hood lift concept: the shape memory alloy ReseTtable (SMArt) dual chamber lift device which is reusable, automatically resettable, and has tunable performance both off-line, and on-line to adjust to extrinsic factors. This device is situated under the rear corners of the hood and stores energy in the form of compressed air in opposing sides of a dual chamber pneumatic cylinder and a high-speed shape memory alloy exhaust valve (SEV) vents the upper chamber within milliseconds to allow the lower chamber to deploy the hood. A general multistage sequential design process is outlined that enables lift timing performance to be tailored by parametric design off-line and by varying operating parameters on-line. A proof-of-concept prototype was built and experimentally characterized for a midsize sedan case study confirming the timing, load capability and stroke of the device on the benchtop and the complete operational cycle in a full-scale automobile hood bay. The impact of additional mass on the lift timing was measured and two on-line adjustable operating parameters (pressure and valve timing) were investigated for their ability to compensate for the mass and other extrinsic effects. While this was a limited study of this new active technological approach to pedestrian safety, it does indicate promise to meet the strict demands of an active lift and a tailorable, resettable/reusable device.

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