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Body Systems
Published in Dorin O. Neacşu, Automotive Power Systems, 2020
A solution that has recently proved to have merit consists of shape memory alloys, also called smart materials. The shape memory alloy is an alloy that can be deformed when cold but easily returns to its predefined shape when heated. The shape memory alloy components are also actuated electrically when an electric current produces Joule heating. This usually produces a fast actuation and a slower de-actuation time. The two most important shape memory alloys are copper–aluminum–nickel and nickel–titanium. Components made of these materials are lightweight and hence a good replacement for the heavier motor drive actuators.
Additive Manufacturing of Metals Using Powder Bed-Based Technologies
Published in Amit Bandyopadhyay, Susmita Bose, Additive Manufacturing, 2019
M. J. Mirzaali, F. S. L. Bobbert, Y. Li, A. A. Zadpoor
Shape memory alloys are materials that are capable of recovering their initial shape once triggered by an external stimulus (e.g., high temperatures). This unique property together with good biocompatibility, corrosion resistance, and high ductility [194] make them promising candidates for fabrication of medical devices such as surgical tools, stents, orthodontic wires, and staples for bone fractures [122]. Nickel-titanium (NiTi) alloys (e.g., Nitinol with 50% Ni and 50% Ti) are the most commonly used types of shape memory alloys. The martensite/austenite phase transformation is responsible for the shape memory property of shape memory alloys. While the martensite phase is stable under low-temperature conditions, the austenitic is stable at high temperatures [195]. Solid and porous NiTi materials have been produced by laser-based AM techniques [196,197]. Functionalized AM porous nitinols have shown high levels of tissue regeneration performance. Therefore, these materials can be used as a basis for development of deployable orthopedic implants [198].
Interconnections and Connectors
Published in Michael Pecht, Handbook of Electronic Package Design, 2018
A combination of ZIF and large normal force is achieved using shape memory alloys. Shape memory alloys have the ability to change from a deformed shape to the original shape when triggered thermally. The deformation and recovery cycles can be repeated thousands of times without degradation if proper conditions are maintained. Shape memory contact components resemble standard contacts in appearance and are manufactured by similar processes. Shape memory alloys provide a zero insertion force along with high normal forces and outstanding performance in temperature cycling, shock, and vibration.
Modeling stress–strain response of shape memory alloys during reorientation of self-accommodated martensites with different morphologies
Published in Mechanics of Advanced Materials and Structures, 2022
Mahendaran Uchimali, Srikanth Vedantam
Shape memory alloys (SMAs) undergo diffusionless reversible phase transformations which results in two technologically important behaviors: pseudoelasticity and shape memory effect (SME) [1]. At temperatures above the transformation temperature, the SMAs exhibit pseudoelastic behavior under mechanical load. On the other hand, SME arises due to a combination of thermal and mechanical loads. When the SMA is cooled below a critical temperature known as the transformation temperature, it undergoes a transformation from an austenite phase to a twinned martensite (consisting of alternating bands of martensite variants). Due to an equal volume fraction of the variants of martensite, this process does not result in a visible shape change in the material [2]. This is termed self-accommodation of the martensite variants.
Computational seismic evaluation of a curved prestressed concrete I-girder bridge equipped with shape memory alloy
Published in European Journal of Environmental and Civil Engineering, 2020
Junwon Seo, Luke P. Rogers, Jong Wan Hu
DesRoches and Delemont (2002), Hu (2013), and Hu, Choi, and Kim (2013) in particular, studied the possible benefits of Shape Memory Alloy (SMA) restraint components, offering many advantages over common steel materials. It should be noted that the cost of SMA material is $1000 and below $150 in USD per kg as of 2008 (Alam, Nehdi, & Youssef 2008); the fully implementation of SMA in bridge replacement or construction might not be an economically reasonable choice. SMA application for only prestressing strands in a bridge was investigated by El-Tawil and Ortega-Rosales (2004) and found that adequate prestress and anchorage forces are attainable, therefore SMA tendons are likely feasible. Further research by Alam et al. (2008) composed of a comprehensive state of the art review. It was found that SMA equipped bridges do have potential to reduce damage and lower maintenance expense. Despite this review, no curved PSC bridges were investigated. A key benefit to shape memory alloys is their ability to withstand large displacements and stresses without permanent deformation. Typical SMAs for use in bridges would be composed of a Nickel-Titanium alloy. This alloy provides superior super elasticity and high transformation of stresses (DesRoches & Delemont, 2002). The results provided evidence that SMA restraints can be beneficial at reducing bridge displacement while remaining elastic.
Design and Testing of Ratcheting, Tension-Only Devices for Seismic Energy Dissipation Systems
Published in Journal of Earthquake Engineering, 2020
Jarrod Cook, Geoffrey W. Rodgers, Gregory A. MacRae
To avoid compression and buckling-related issues, several tension-only solutions have been developed. Among these solutions is a damper-cable bracing mechanism [Phocas and Pocanschi, 2003], which uses pulleys and small cable members in tension. The seesaw vibration control system [Kang and Tagawa, 2013] comprises three main parts: a brace, seesaw member and viscoelastic dampers. This system presents a reasonably high level of complexity in design. Eatherton et al. [2014] have proposed adding self-centering capability to BRB systems. This approach has some limitations due to high costs, particularly when using shape memory alloys, and low stroke capacities. Lei et al. [2014] have used wedge spring devices to offset anchor bolt elongation in column connections. This is a promising design system, but the application is limited to small displacements and may not be suitable for use with energy dissipation in bracing systems. A non-buckling segmented brace system with sliding joints has been proposed by Hao [2015]. The use of multiple joints in this design provides significant inelastic capacity, but increases the number of parts and system assembly complexity. A further project addressing these issues is a compression-free device (CFD) for energy dissipative braces using an arrangement of cams and rollers with a slim steel coupon [Thammarak et al., 2015]. Despite several promising designs present in the research, there has been little adoption of tension-only systems in the structural design industry, and the need for an effective, yet simple and low-cost non-buckling, seismic energy dissipation solution remains.