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.

Rolling Texture of α"-Phase in Ti-22mol%Nb-3mol%Al Biomedical Shape Memory Alloy

2007 ◽  
pp. 1517-1520
Author(s):  
Tomonari Inamura ◽  
Ryutaro Shimizu ◽  
Jae II Kim ◽  
Hee Young Kim ◽  
Kenji Wakashima ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Rolling Texture ◽  
Α Phase

Non-Contact Technique for Characterizing Full-Field Surface Deformation of Shape Memory Polymers

2010 ◽  
Author(s):  
A. J. W. McClung ◽  
G. P. Tandon ◽  
K. E. Goecke ◽  
J. W. Baur
Keyword(s):  
Elastic Modulus ◽  
Shape Memory ◽  
Strain Measurement ◽  
Shape Memory Polymers ◽  
Material Behavior ◽  
Image Correlation ◽  
Optical Measurements ◽  
Transverse Strain ◽  
Strain Gages ◽  
Full Field

Thermally-actuated shape memory polymers (SMPs) typically display two phases separated by the glass transition temperature (Tg). At temperatures well below the Tg, the polymer exhibits a relatively high elastic modulus. Well above the Tg the elastic modulus drops by several orders of magnitude. In this high temperature region, SMP materials can achieve strain levels well above 100 %. The complex behavior of SMPs (stiffnesses dropping to the order of 1 GPa and extremely high strain levels) precludes the use of traditional strain gages and low-contact force extensometers. The present study presents a detailed expansion of state-of-the-art thermomechanical testing techniques used to characterize the material behavior of SMPs. An MTS environmental chamber with an observation window allows for non-contact optical measurements during testing. A laser extensometer is used for measurement and active control of axial strain. The upper limit on the strain rate capability of the laser extensometer is established. In addition, the photographic strain measurement method known as digital image correlation (DIC) is incorporated, allowing for full field measurement of axial and transverse strains of SMPs over a range of temperatures and strain rates. The strain measurements of the DIC and laser extensometer are compared to each other as well as to clip-on extensometers and strain gages. The comparisons provide insight into the limitations of the traditional strain measurement systems. A series of tensile tests are performed on a commercial SMP from 25 °C up to temperatures of 130 °C and strain levels above 100 %. The laser extensometer provides a robust method for controlling the strain in the gage section of the samples. In addition, results show that the full field measurements of both the axial and the transverse strain are essential for characterizing the constitutive response of SMPs at room and elevated temperatures.

Full-Field Deformation and Thermal Characterization of GNP/Epoxy and GNP/SMA Fiber/Epoxy Composites

2019 ◽  
Author(s):  
Ugur Kilic ◽  
Muhammad M. Sherif ◽  
Sherif M. Daghash ◽  
Osman E. Ozbulut
Keyword(s):  
Shape Memory ◽  
Epoxy Matrix ◽  
Large Scale ◽  
Low Cost ◽  
Image Correlation ◽  
Epoxy Composites ◽  
Uniaxial Tensile ◽  
Graphene Sheets ◽  
Atomic Lattice ◽  
Full Field

Abstract Shape memory alloys (SMAs) are a class of metallic alloys that possess remarkable characteristics such as superelasticity and shape memory effect. Superelastic SMAs have been considered as fiber in polymer composites due to their ability to recover their deformation upon removal of load, good energy dissipation capacity and impact resistance. Graphene nanoplatelets (GNPs) consists of small stacks of graphene sheets that are two-dimensional. Both sides of atomic lattice of GNPs contact matrix of a composite system and can generate more sites for potential chemical and physical bonding with the host material. Most importantly, graphene sheets and their derivatives can be produced at large-scale for industrial demand at low-cost. This study explores the fabrication of multi-scale reinforced epoxy matrix composites in which GNPs and SMA strands are employed as nano- and micro-scale reinforcements, respectively. First, GNPs are dispersed into a ductile and brittle epoxy matrix to produce GNP/epoxy nanocomposites. To study the effect of GNP content on the behavior of the developed nanocomposite, GNPs are added to the epoxy-hardener mixture at different weight percentages (neat, 0.1%, 0.25%, 0.5%, 1%, and 2%). Uniaxial tensile tests of the developed nanocomposites are conducted under monotonic load up to failure. The optimum GNP content for GNP-reinforced epoxy matrix is determined and used in the fabrication of SMA fiber/epoxy composite. The developed multiscale reinforced epoxy composites are tested under tensile loading and their full-field strain and temperature behavior are monitored and evaluated using a digital image correlation system and an infrared thermal camera.

Deformation and Failure of Pre-Notched Thin Metal Plates Subjected to Confined Blast Loading

2015 ◽  
Vol 782 ◽  
pp. 49-58
Author(s):  
Han Liu ◽  
Peng Wan Chen ◽  
Bao Qiao Guo ◽  
Shao Long Zhang ◽  
Hai Bo Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Deformation ◽  
Blast Loading ◽  
Thin Metal ◽  
Image Correlation ◽  
Deformation And Failure ◽  
Full Field ◽  
3D Digital Image Correlation ◽  
Metal Plates ◽  
Dic Technique

In this paper, the dynamic deformation and rupture of pre-notched thin metal plates subjected to confined blast loading were investigated. The thin copper plates with cross-shape pre-notch were clamped on the end of a confined cylinder vessel by a cover flange. An explosive charge with a mass of 4g was detonated in the vessel center to generate blast load acting on the metal plates. The images of metal plates were recorded by two high-speed cameras. The displacement and strain fields during the deformation and rupture process were measured by using 3D digital image correlation (3D DIC). The effects of pre-notches on the dynamic deformation and rupture of thin metal plates were analyzed. The microstructure of fracture surface was examined The 3D DIC technique is proven to be an effective method to conduct dynamic full-field deformation measurement.

Design of a shape-memory alloy actuated macro-scale morphing aircraft mechanism

2005 ◽  
Author(s):  
Justin Manzo ◽  
Ephrahim Garcia ◽  
Adam Wickenheiser ◽  
Garnett C. Horner
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Morphing Aircraft ◽  
Macro Scale

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.

Full Field Measurements of the Dynamic Response of AA6061-T6 Aluminum Alloy Under High Strain Rate Compression and Torsion Loads

2012 ◽  
Author(s):  
Gbadebo Owolabi ◽  
Daniel Odoh ◽  
Akindele Odeshi ◽  
Horace Whitworth
Keyword(s):  
Aluminum Alloy ◽  
High Speed ◽  
High Strain ◽  
Shear Bands ◽  
Field Measurements ◽  
Image Correlation ◽  
Deformation Analysis ◽  
Deformation And Failure ◽  
Full Field ◽  
Structural Applications

Aluminum alloys exhibit an attractive combination of mechanical and physical properties such as high stiffness and low density, which favors their utilization in many structural applications. Thus, increasing the structural applications of aluminum alloy is the driving force for the need to adequately understand its deformation and failure mechanisms under various types of dynamic loading conditions. In this study, full field plastic deformation of AA6061-T6 aluminum alloy at high strain-rates under compressive and torsion loads are measured using split Hopkinson compression and torsion bars and a high speed digital image correlation system. The stress-strain curves obtained using the high speed digital cameras are compared with results obtained from the elastic waves in the compression and torsion bars. A post deformation analysis of the specimen also shows strain localization along narrow adiabatic shear bands in the AA6061-T6 alloy.

Rolling Texture of α"-Phase in Ti-22mol%Nb-3mol%Al Biomedical Shape Memory Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 1517-1520 ◽  
Author(s):  
Tomonari Inamura ◽  
Ryutaro Shimizu ◽  
Jae II Kim ◽  
Hee Young Kim ◽  
Kenji Wakashima ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Parent Phase ◽  
Reduction Rate ◽  
Rolling Texture ◽  
Martensite Phase ◽  
Orthorhombic Martensite ◽  
Preferential Formation ◽  
Macroscopic Deformation ◽  
Cold Rolled

Rolling texture of α"(C-orthorhombic) martensite phase in Ti-22mol%Nb-3mol%Al β-titanium based shape memory alloy was examined using X-ray pole figure measurement. The alloy was dual phase of α'' and β(bcc) at room temperature (RT) and was cold-rolled with reduction rates of 40%~99% at RT. Stress-induced martensitic transformation occurred during the rolling and then the material was fully transformed into martensite phase. Subscript α" and β indicate martensite and parent phase hereafter. The major texture was close to {411}α"<173>α" when the reduction rate was lower than 60%. This texture is a result of a preferential formation of specific variants which have a higher interaction with the macroscopic deformation. As the reduction rate was increased, ND moved toward {101}α" whereas RD was around <010>α" regardless of the reduction rate. {101}α"<010>α" texture was confirmed when the reduction rate was 99%.

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.

Novel Methods for Assessment of Three-Dimensional Constitutive Properties for Composites

2010 ◽  
Vol 452-453 ◽  
pp. 401-404 ◽  
Author(s):  
Paige Carpentier ◽  
Andrew Makeev
Keyword(s):  
Polymer Matrix Composites ◽  
Three Dimensional ◽  
Image Correlation ◽  
Stress Strain ◽  
Complex Deformation ◽  
Deformation And Failure ◽  
Full Field ◽  
Short Beam ◽  
Beam Shear ◽  
Constitutive Properties

Accurate three-dimensional stress-strain constitutive properties are essential for understanding of complex deformation and failure mechanisms for glass-fiber and carbon-fiber reinforced polymer-matrix composites. A large number of different methods and specimen types, which are currently required to generate three-dimensional allowables for structural design, slow down material characterization. Also, some of the material constitutive properties are never measured due to prohibitive cost of the specimens needed. This work shows that simple short-beam shear specimens are well-suited for measurement of 3D constitutive properties for composite systems. In particular, a methodology to measure tensile and compressive material properties, generate shear stress-strain curves and measure the shear strength in a simple short beam shear test will be presented. The methodology is based on the Digital Image Correlation (DIC) full-field deformation measurement. Short-beam and curved-beam tests are accomplished to generate 3D stress-strain response for glass/epoxy and carbon/epoxy tape composite material systems. Accuracy of constitutive properties is also verified using standard methods and data available in the public domain.

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