bluuebunny/crossref_metadata_2025_split huggingface dataset:
Additive Manufacturing of Cu-Al-Ni Shape Memory Alloys through Laser Powder Bed Fusion and Laser Metal Deposition: Challenges and Perspectives
Authors: Juan Jose M. San , Pérez-Cerrato Mikel , Del-Rio Lucia , Urionabarrenetxea Ernesto , Leunda Josu , Gómez-Cortés Jose F. , Aristizabal Miren , Quintana Iban , Carreño Fernando , Burgos Nerea , Nó Maria L. 
Published: May 2024

Abstract
Shape memory alloys (SMA) are functional materials that are being applied in practically all industries, from aerospace, automotive, robotics and biomedical sectors, and at present the scientific and technologic communities of SMA are looking to get the advantages offered by the new processing technologies of additive manufacturing (AM). However, the use of AM to produce functional materials, like SMA, constitutes a real challenge because of the particularly well controlled microstructure required to exhibit the functional property of shape memory. Most of the efforts are being focused on AM of Ti-Ni alloys, but there is a growing interest in Cu-based SMA due to their good functional properties of shape memory and superelasticity, even at high temperature. In the present work, the design of the complete AM processing route, from powder atomization and using two different methods of AM, is developed and the finally obtained thermomechanical properties are compared to those obtained by classical powder metallurgy route, using exactly the same Cu-Al-Ni SMA powders.
Sinter-Based Additive Manufacturing of Ni-Ti Shape Memory Alloy
Authors: Cohen Yeshurun , Addess Alon , Burkhardt Carlo , Vogel Lucas , Baum Andreas , Mitteramskogler Gerald , Glass Boaz , Rabkin Eugen , Shilo Doron , Faran Eilon 
Published: May 2024

Abstract
Additive manufacturing (AM) of Shape Memory Alloys (SMA) is an emerging technology that can open the route for numerous new applications in the fields of actuation, sensing, energy harvesting, and heat management. Currently, most AM processes of SMA rely on melting-based methods that locally melt the metallic feedstock of Ni-Ti. However, the repeated melting impairs the resulting microstructure, thus limiting the ability to undergo a reversible thermo-elastic martensitic transformation. Recent advances in sinter-based AM have the potential to facilitate the control over the final microstructure and properties of the printed SMA. Here, we present the production and characterization of Ni-Ti SMA produced via two sinter-based AM methods: 1. Lithography-based Metal Manufacturing (LMM), and 2. Moldjet, a unique modification of conventional metal injection molding.
Effect of Severe Torsion Deformation on Structure and Properties of NiTi Shape Memory Alloys
Authors: Komarov Victor 
Published: May 2024

Abstract
NiTi shape memory alloys (SMA) are attractive functional materials that are widely used in different fields of engineering and medicine for production of various shape-memory devices. The severe plastic deformation (SPD) is one of the most effective methods for the formation of an ultrafine-grained structure (UFG) in NiTi SMA, which is characterized by the best combination of functional properties. The development of SPD methods continues in the direction of the investigation of new approaches allowing to produce bulk samples with a nanocrystalline structure. Severe torsion deformation (STD) is a promising SPD method that allows for high plastic strain accumulation without significant dimensional changes. It was established that application of STD provides simultaneous improvement of strength and ductility of studied alloys. However, STD has never been applied to NiTi SMA. Therefore, in this study, STD was applied to NiTi SMA at various deformation temperatures from 350 to 600°C in order to maximize the number of turns and accumulate significant strain. Deformation in this temperature range leads to the formation of a dynamically polygonised dislocation substructure, that must provide conduction of the highest number of turns and facilitate the formation of an UFG structure. The goal of this work is to evaluate the possibility of applying the torsional deformation to bulk NiTi samples at low temperatures (in the range of dynamic polygonization) to accumulate high strains and refine the structure.
Influence of Heating, Cooling Rates, and Testing Media on Results of ASTM E3097 Testing Performed on NiTi Wire
Authors: Davis Jack , Wilson Todd 
Published: May 2024

Abstract
The ASTM E3097 standard for constant-force thermal cycling provides a useful framework for measuring properties of shape memory alloys relevant to actuation applications, namely transformation strains and transformation temperatures. The standard allows for operator discretion when selecting a heating and cooling rate for the thermal cycling, provided that the specimen temperature is maintained uniformly within ±3°C across the specimen throughout the course of the thermal cycling. With larger test specimens such as dog-bones, for example, this can be ensured via thermocouples affixed to the specimen. Substantial work has been done to quantify the ruggedness of the standard for such specimens. However, it can be difficult to verify specimen temperature in-situ during testing of wire specimens due to their small diameter. Contact methods, such as thermocouples, can be difficult to affix to the specimen due to its small size. It is also difficult to get accurate measurements using contact methods, due to the often- substantial size and mass disparity between the temperature sensor and the wire specimen and the tendency of the temperature sensor to act as a heat sink for the test specimen. Non-contact methods such as infrared (IR) thermography are possible, but not always practical. A high image resolution is crucial for IR measurement of small diameters, and calibration adjustments may be required from one test to the next, depending on surface characteristics and resulting emissive properties, to ensure accurate measurements. For these reasons, one common practice is to thermally cycle the wire specimens by means of a temperature-controlled environment, rather than heating the specimens directly, and change the temperature of the environment at a rate such that the wire specimen remains equilibrated in temperature. It is, therefore, especially important when testing wire according to the E3097 standard for the test operator to understand the potential influence of heating and cooling rates on test results. This work presents results from ASTM E3097 tests performed on various wire diameters using different thermal ramp rates, as well as different testing media.
Effects of Permanent Loads on Mechanical Performance of Nitinol Tubes
Authors: Guzmán José M. Matamoros , Sesin Jorge M. Cubero , Meza Fernando A. Dittel , Quirós Oscar Chaverri , Plaskonka-Weisenburger Katarzyna , Keck Andreas 
Published: May 2024

Abstract
Nitinol is frequently used as raw material for cardiovascular endoprosthesis, due to their high biocompatibility and properties such as psedoelasticity. Typically, the highest stress/strain that Nitinol based devices undergo occurs during crimping. These mechanical stresses can affect the functional fatigue behaviors. Nitinol devices are crimped to small diameters to deliver to the anatomical location of interest. Thereby, the microstructural and mechanical changes in Nitinol tubes generated by mechanical load conditions are studied, to monitor the pseudoelastic properties as a function of load time. Consequently, a permanent load test is carried out by means of a fixture with parallel clamps, in order to generate deformation of the cross-sectional area of the tube. The procedure consists of deforming 5 mm long samples with 7 mm outer diameter tubes and a wall thickness of 0.5 mm in straight annealed condition at room temperature. For this test, o-shaped samples of single ingot were analyzed. The test was carried out with strains of 2 %, 4 %, 6 % and 8 % to simulate different device crimp strains. Parts were evaluated after time intervals up to six months under load. Afterwards the geometrical changes of the samples were measured. Additionally, the samples were characterized by DSC and XRD measurements.
Observations of Damage and Crack Formation in Nitinol at Inclusions Smaller Than the Critical Flaw Size
Authors: Rendon Nathan , LePage William 
Published: May 2024

Abstract
Inclusions and surface defects are the primary drivers of fatigue fractures for Nitinol. Surface defects can take the form of die marks, surface roughness, or scratches, and when present, these will typically be the sites for fatigue fractures. When such surface defects are not present, however, surface-exposed inclusions become the primary sites of fatigue fractures. Surface-exposed inclusions are either fully embedded (no surrounding voids) or particle-void assemblies (PVAs). PVAs are up to 600 times more likely to be the sites of crack nucleation compared to fully embedded particles, so they are of primary interest. PVAs typically take the form of a single, small, and unbroken inclusion with one or two associated voids (coined a "teardrop"), or a longer, drawn-out, and broken-up inclusion with many voids (coined a "stringer").
Shape Memory Alloy Rotary Actuators for Aerospace: Part 2 Applications and Maturation
Authors: Calkins Frederick , Nicholson Douglas E. , Mabe James H. 
Published: May 2024

Abstract
Shape memory alloys (SMA) provide a compact, robust, light-weight and scalable rotary actuation technology suitable for many aerospace applications that require precise control and high torque over a discrete output range. With their compact form factor and high energy density, SMA rotary actuators can often be directly integrated into or near a hinge line reducing the need for complex kinematics (e.g., linkages and gears) that are typically required to transfer the work from a rotary actuator’s output to an effector such as a flap or aileron. Boeing has executed high technology readiness level (TRL) demonstrations and production use of scalable SMA rotary actuation technology across several size scales and aeronautical platforms. Applications range from wind tunnel models to full-scale laboratory demonstrators and flight tests. Successful demonstrations include reconfigurable vortex generators, actuated wind tunnel models, adaptive trailing edges, power door opening systems, spanwise adaptive wings, variable area nozzles and variable geometry structures.
Phase Transformation Temperatures and Pseudoelasticity Behavior of NiTi-X Ternary Shape Memory Alloys: A Molecular Dynamics Simulation Study
Authors: Bahramyan Mehran , Little Suzanne , Brabazon Dermot 
Published: May 2024

Abstract
NiTi alloy stands out as a promising material, particularly in biomedical, aerospace, and heat pump applications, owing to its biocompatibility and distinctive properties, including exceptional shape memory (SME) and pseudoelasticity. These properties arise from the alloy's capacity to undergo phase transformations during heating/cooling and loading/unloading cycles. The specific phase transformation temperatures and pseudoelastic behavior are heavily influenced by the composition of the alloy. The introduction of transition elements such as V, Cr, Mn, Fe, and Co in place of Ni and Ti can lower the martensite start (Ms) temperature, while substitution with Hf, Zr, Ag, and Au for Ni and Sc, Y, Hf, and Zr for Ti can elevate the Ms temperature. Consequently, it is imperative to comprehensively comprehend the effects of third alloying elements on the properties of these alloys from an atomic perspective. Molecular dynamics (MD) simulations, operating at the atomic level, offer a valuable means to explore the impact of various compositions, including the addition of a third element, on the alloy properties, thereby enhancing their performance. However, a significant challenge in MD simulations lies in selecting reliable interatomic potentials between the elements. Developing new potentials poses challenges, prompting the evaluation of existing potentials for ternary systems in this study, which will be compared with experimental results. While several interatomic potentials have been proposed for binary NiTi SMAs, limitations arise when extending to tertiary alloys. Existing studies have reported ternary interatomic potentials for NiTiV, NiTiNb, and NiTiHf, but these are insufficient for capturing the phase transformation of these tertiary systems. To address this, a hybrid model will be employed, combining different types of interatomic potentials such as modified embedded atom method (MEAM), embedded atom method (EAM), Lennard-Jones (LJ), and Morse potentials. This approach aims to capture the phase transformation of ternary alloys doped with elements like Cu, Hf, Pd, Pt, Sc, Ta, Mn, Zr, Y, and Au, which can increase transformation temperatures such as the martensite start temperature (Ms), martensite finish temperature (Mf), austenite start temperature (As) and Austenite finish temperature (Af), during cooling and heating processes. These alloys, known as high-temperature shape memory alloys (HT-SMAs), hold significant potential for diverse applications, including actuators, owing to their unique properties and enhanced transformation behaviours.
Modeling the Dynamic Deformation of Shape Memory Alloy Hybrid Composites under External Influences
Authors: Kaiser Max , Kunzler Manuel , Gurka Martin 
Published: May 2024

Abstract
Morphing shape memory alloy hybrid composites (SMAHC) offer a great potential for various engineering applications due to their lightweight properties and their ability to undergo significant deformations. They fundamentally consist of two primary components: a stiff substrate and a shape memory alloy (SMA) layer, enabling external two-way shape memory capability. During actuation the metallic SMA undergoes a contraction of several percent when subjected to electric current. As the SMA contracts, the substrate retains its original length, causing a bending movement in the composite. A third component to be mentioned is the interlayer, positioned between the rigid substrate and the SMA layer, opens up a greater design flexibility. By adjusting the distance between these two components fine-tuning of the relationship between deflection and bending moment in response to an external load can be achieved. (compare Fig. 1).
Nitinol Film: From Research to Clinical Trial
Authors: Miranda Rodrigo Lima de , Bechtold Christoph , Chluba Christoph 
Published: May 2024

Abstract
Nitinol, a remarkable alloy of nickel and titanium renowned for its unique shape memory and superelastic properties, has been instrumental in various industries for decades. Traditional fabrication methods, such as melting, metal transformation, and subtractive structuring, have been the norm in Nitinol production. The potential of alternative, additive deposition techniques, despite their precision and scalability, remains largely untapped in the manufacturing of Nitinol components, particularly those intended for clinical applications.
New Cu-Based Shape Memory Alloy Family Transforming at Ultra-Low Temperatures for Cryogenic Applications
Authors: Juan José M. San , Lorenzo Patricia , Nó Maria L. 
Published: May 2024

Abstract
Nowadays, there is a great interest in developing new families of shape memory alloys (SMA) exhibiting thermomechanical properties beyond the classical ones obtained with the well-known NiTi SMA and the derived ternary alloys. Indeed, a great effort is being focused in developing high-temperature SMA, like the ones based on NiTiHf/Zr or on Cu-Al-Ni, and also on the development of SMA that could be successfully implemented at micro and nanoscale for smart micro electro-mechanical systems (MEMS) applications. However, new hydrogen-based energy sources, high-power nuclear fusion and the emerging quantum computing technologies, as well as the classical superconducting ones, require low-temperature working environments. All of them need the use of sensors and actuators at cryogenic temperatures, but, at present, there are not shape memory alloys (SMA) offering the possibility of operating as sensors and actuators, valves for instance, at so low temperatures, below liquid nitrogen.
Alloy Design for Additive Manufacturing of Shape Memory Alloys
Authors: Pourshams Mohammad , Dabbaghi Hediyeh , Poorganji Behrang , Elahinia Mohammad 
Published: May 2024

Abstract
There is a growing need to design tailored alloys for Additive Manufacturing (AM) in order to achieve the desired properties and quality in the resulting parts. The need is even stronger for functional materials such as Nickel- Titanium (NiTi) shape memory alloys (SMAs) with microstructure-driven properties such as superelasticity and the shape memory effect. These alloys have been used in innovative applications in aerospace, biomedical, and robotics. Despite their potential, the realization of NiTi SMAs through AM faces significant challenges, including phase stability, compositional heterogeneity, and solidification defects, which impede the achievement of desired microstructural and mechanical characteristics.
Shape Memory Alloy Design for a Lightweight and Low Stow Volume Expandable Solar Concentrator
Authors: Worrell Dominique , Gantz Faith , Bolisay Linden , Palisoc Art , Young Marcus L. 
Published: May 2024

Abstract
Solar concentrators increase the amount of usable energy available in solar collection systems by focusing energy through an aperture to which energy is magnified within the area of its trajectory. Design challenges of a solar concentrators for space applications are to make them more lightweight, compact, and exhibit a smooth and consistent reflective surface curvature for optimal performance. Shape memory alloys (SMAs) offer an effective and compact solution to engineering needs, such as solar reflectors, to reduce weight and improve overall energy collection and concentration performance. The one-way shape memory effect can be used for this application, where the SMA is heat treated in a strained designed curvature by forcing the austenite microstructure to “remember” the original shape even after deformation. SMAs are capable of actuating from the stow configuration and into the designed shape after the solar energy exposure induces a phase transformation. In this study, NiTi and NiTiCu SMAs were thermomechanically processed into plates and cut into three sizes of triangular chips for use as reflector components. Standard binary NiTi SMAs was modified with the substitution of Cu for Ni to achieve a narrower hysteresis and better thermomechanical cycling stability. The SMAs were produced from commercially available NiTi SM495 plates by ATI Specialty Alloys and Components (Albany, OR) and custom-melted NiTiCu buttons. Each processing step was comprehensively characterized to monitor microstructural and thermomechanical property changes using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Vickers hardness (HV). The NiTi and NiTiCu triangular chips were shape-set utilizing a custom-made apparatus to attain the intended curved surface with specific dimensions for a reflector component within a solar concentrator.
Processing and Thermomechanical Stability of Low Hysteresis Shape Memory Alloys
Authors: Montagnoli Andre , Young Marcus L. , Somsen Christoph , Frenzel Jan A. , Calkins F. Tad , Nicholson Douglas E. 
Published: May 2024

Abstract
NiTi shape memory alloy (SMA) actuators have gained much attention in recent years because of their ability to combine high actuation forces to a significantly smaller component size. Binary SMAs containing Ni and Ti, however, suffer from relatively poor functional and structural fatigue, which requires training. Binary NiTi SMAs also possess a relatively wide hysteresis gap between the austenite final and martensite final temperatures (ΔTMfAf), which demands more energy to produce each actuation stroke. Zarnetta et al. have shown that small additions of substitutional elements to the NiTi-based SMA can significantly improve those conditions by increasing the coherency between the two transforming crystal structures. Two quaternary NiTiCuPd SMAs were selected based on combinatorial studies from X-ray diffraction data and their results were analyzed concerning their hysteresis width and thermal-mechanical stability.
Laser-Induced Nanostructures on Shape Memory Actuators for Strain Detection
Authors: Marx Jan , Schuleit Marvin , Haske Damian , Esen Cemal , Ostendorf Andreas 
Published: May 2024

Abstract
The activation behavior of nitinol actuators is typically examined in test rigs equipped with sensors for measuring mechanical and electrical parameters. However, these test rigs allow for measurements only under laboratory conditions; assessing the actuator behavior in real-world applications is not feasible. Therefore, a non-invasive, optical measurement method for relative strain detection of shape memory actuators is presented in this work. It is based on the diffraction of a laser beam by an optical grating applied to the surface of the actuator. While the grating period changes with the strain state of the actuator during activation, a camera captures the interference pattern to detect the diffraction angle of the maxima spots.
Atomic Layer Deposition as an Alternative Surface Finishing Technique: Characterisation of Oxide Layer Composition and Corrosion Behaviour
Authors: Höger Kim , Bruchlos Kirsten , Zende Stefan , Feth Nils-Agne 
Published: May 2024

Abstract
Nitinol is an important material for medical implants due to its super elastic behaviour and since its mechanical properties mimic biological materials. The surface of nitinol implants is commonly covered with a thin titanium dioxide (TiO2) layer which acts both as a passivating layer to increase the corrosion resistance and as a barrier layer to address the toxicological concerns of long-term nickel release into the biological tissue. Even though nitinol undergoes a natural passivation when exposed to air, various thermal, chemical, and electrochemical surface finishing techniques are applied during manufacturing to replace the native oxide layer by uniform TiO2 layers of controlled thickness. The properties of these oxide layers depend on the surface finishing technique and the process parameters.
Surface Functionalization of Nitinol Utilizing Ultrashort Laser Pulses
Authors: Bittigkoffer Lucas , Roth Henry , Baumann Martin , Feth Nils-Agne 
Published: May 2024

Abstract
Ultrashort pulse (USP) lasers are an established technology to manufacture nitinol medical devices. USP lasers offer a great variety of processing parameters which can be utilized for fine cutting, laser lathe and ablation of nitinol. Usually, several hundreds of kHz are used to penetrate the material with pulses of fixed energy and frequency. New USP laser sources are offering a so-called burst mode which can be used to precisely control the energy deposition into the material by adjusting the temporal pulse distribution. Depending on the applied process parameters, this leads to a cut through or ablation of some material besides a modification of the irradiated surface. Previous work showed that the bulk material is not affected by such laser light whereas the laser-matter interface is changed. The perpendicular irradiated surfaces are dominated by laser-induced periodic surface structures (LIPSS) which are oriented to the direction of polarization of the laser beam and by cone-like protrusions (CLPs). These modified surfaces allow, e.g., different roughness, wetting, corrosion, bioactivity, and ultimately tribological properties. The effect of such femtosecond laser-generated structures was shown for stainless steel and titanium. Complex medical devices might benefit from locally adjusted surface properties e.g. reduced frictional force between tissue and device or improved adhesion due to an increased surface area through microstructures.