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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Poly(styrene-co-N-alkylmaleimide)s can be prepared either by free-radical polymerization of the respective monomers or by chemical modification of poly(styrene-co-maleic anhydride) (SMA) with primary amines. The radical route which has been described extensively in the literature is used when alternating poly(styrene-co-N-alkylmaleimide)s are required.3,4 Non-equimolar polymers can be prepared from the reaction of the maleic anhydride group in the SMA polymer backbone with primary amines. This reaction is usually accomplished in organic solvents at temperatures ∼, 125 °C, and pressures between 4.105–106 Pa after 8 to 48 hrs.5,6 Generally, the use of a solvent facilitates the control and the reactivity between the reactants. Another approach is to conduct the reaction in the melt as is described in this article. In this case the main reaction medium is the molten polymer and the reaction and process parameters are very different, especially temperature and viscosity.
Damping and frequency of a sag cable attached with a pre-tensioned Shape Memory Alloy wire
Published in Jaap Bakker, Dan M. Frangopol, Klaas van Breugel, Life-Cycle of Engineering Systems, 2017
H. J. Zhou, Y. H. Wu, G. Z. Yao, L. B. Zhou, F. Xing, L. M. Sun
SMA is a type of smart material with high damping and re-centering capability. Earlier studies have shown that SMA also has high fatigue resistance and high corrosion durability. Therefore, Efforts have been undertaken to develop various types of dampers, actuators and other devices to mitigate engineering structures vibration in the past few decades (Song et al. 2006, Desroches & Smith 2003, Zhang & Zhu 2007, Huang et al. 2014). A few literatures are also already available to apply SMA dampers for cable vibration mitigation. Zuo & Li (2011) developed a SMA damper and verified the mitigation effects by both numerical simulation and experimental results. Li et al. (2004) conducted theoretical and numerical studies to explore the damping effects of cable with attached SMA damper. Liu et al. (2007) further conducted model cable experiment to verify the mitigation effects of SMA spring dampers to the cable. Casciati et al. (2008) discussed the feasibility of cable vibration mitigation by added SMA wire [14]. Mekki & Auricchio (2011) further investigated effects of SMA damper parameters on energy dissipation capability by numerical simulation; and a comparison between SMA damper and TMD damper to control the stay cable was made. Faravelli et al. (2011) proposed a hybrid control policy which combines wrapped shape memory alloy wires and an open-loop actuation in mitigating the linear and non-linear multimodal cable vibration; both numerical and experimental results showed that the open loop controller guaranteed a significant reduction of the nonlinear response of both the first and the second in-plane modes.
Materials for 3D Printing in Medicine
Published in Harish Kumar Banga, Rajesh Kumar, Parveen Kalra, Rajendra M. Belokar, Additive Manufacturing with Medical Applications, 2023
Kamal Kishore, Roopak Varshney, Param Singh, Manoj Kumar Sinha
Shape-memory alloys are smart materials which may be defined as materials having the ability to change their strength, execute and control movement, generate signals due to changes in geometry or property when exposed to external stimuli such as heat, magnetic field, etc. There are two stable phases for shape-memory alloys; one is at a high temperature called austenite and the other at a low temperature called martensite (Mantovani, 2000). Firstly in 1938, copper-zinc alloy and copper-tin alloy were developed as shape-memory alloys by Greninger and Mooradian. Initially, the pace of research and development related to SMA was slow and therefore it took nearly 30 years to patent the first SMA (Mehl et al., 1938). Further, in 1965, Buehler and his co-worker developed a nitinol (nickel-titanium) based smart alloy in a naval ordnance laboratory and named it (Heilig, 1994). Consequently, some other smart metal alloys were also developed in due time, such as copper-aluminium-nickel, copper-zinc-aluminium and iron-manganese-silicon. Still, NiTi alloy is widely used due to its biocompatibility and high strength. The nickel-titanium alloys can be produced by vacuum melting techniques such as electron-beam melting and vacuum induction melting (Mahan, 2019). However, its processing is very difficult as it is externally compositional sensitive and also the machinability of such SMA is relatively poor. Hence, AM technologies such as SLM are being considered as potential solutions to fabricate parts from NiTi alloys. NiTi is used to make bone clamps, stents, catch baskets for kidney stones, metal guide wires, orthodontics, etc. (Strittmatter et al., 2019).
Electro-mechanical characterization of shape memory alloy hybrid yarn based adaptive fiber-reinforced plastics
Published in The Journal of The Textile Institute, 2021
Moniruddoza Ashir, Eric Häntzsche, Chokri Cherif
Active functionalization of FRP can be achieved by means of an actuator. An actuator is a material or device, which converts an energy flow into mechanical and thermal energy. Shape memory alloys (SMA) are being used as actuator material by the composite community due to their higher volume specific work capacity of 10 J/cm3 compared to other actuator materials, such as bimetals, piezoelectric materials, or shape memory polymers (Pagel et al., 2013). SMA are metallic materials that can return to their original shape after plastic deformation during the thermal induced activation. The phase transition takes place at a certain transition temperature, which converts the microstructure from martensite to austentine (Otsuka & Wayman, 2002). The transition temperature depends on the percentage of alloy materials and ranges from −200 to 100 °C (Pagel et al., 2013).
Influence of the aggregate skeleton matrix and volumetric composition on the resistance of stone mastic asphalt to permanent deformation
Published in Road Materials and Pavement Design, 2021
Henrique Manuel Borges Miranda, Fátima Alexandra Batista, José Neves, Maria de Lurdes Antunes
The results allow to achieve the following main conclusions: SMA with coarse aggregate optimised with Proctor did not clearly distinguish itself from the dry-rodded and steel roller compaction, with respect to the SMA’s resistance to permanent deformation.For the studied cases, SMA tended to show a good resistance to permanent deformation with similar results independently: (i) of the aggregate skeleton matrix design method used, or (ii) of non-compliance with aggregate ranges recommended in the Bailey method.SMA optimised with Proctor and steel roller compaction tended to ensure a higher coarse aggregate content, higher binder content (around 1.0%), and VMA, as well as a thicker binder film coating comparatively to SMA designed by recipe method or optimised with dry-rodded compaction. Nevertheless, their resistance to permanent deformation was not significantly affected, despite the higher binder content.The use of a higher coarse aggregate content or nominal maximum aggregate size did not show a statistically significant correlation with the resistance to permanent deformation.Ratio between Marshall stability and flow, as well as, the ratio between binder film thickness and porosity revealed to have a statistically significant strong correlation with permanent deformation properties (RDAIR, WTSAIR and PRDAIR).
Parametric study of automotive shape memory alloy bumper beam subjected to low-velocity impacts
Published in International Journal of Crashworthiness, 2021
Ardalan Asadpoori, Ahmad Keshavarzi, Reza Abedinzadeh
Bumper systems are one of the most prominent vehicle structures which is considered in designing to reach a suitable impact behavior [5–8]. automobile bumper system is responsible for absorbing energy due to an impact according to the design facts [9,10]. The main expectations are to be deformable enough, absorb energy in order to reduce the pedestrian’s injuries, furthermore have necessary strength [10,11]. Although there are many studies on the mechanical behavior of shape memory alloy [12–15] the studies on behavior of automobile bumper beam made of these materials during the impact are few. Utilizing new groups of materials can reduce the car bumper weight and increase the strength [16,17]. There are a lot of automobile components which are made from shape memory alloy such as actuators (thermal or electrical) are discussed due to the demand for safety and comfortable requirements [18]. Such as motor actuator in side mirrors [19,20]. Many Researchers have found SMA more effectively in increasing the car safety by removing the lever of the clamping system and using a steering column. Moreover, the reduction of knee injuries has been reported [21]. Gheorghita et al. [22] investigated the behavior of wires which had made from NiTi under static (V < 50 mm/s) and dynamic conditions (V > 50 mm/s). according to the results, the NiTi wires are able to dissipate mechanical energy in static, quasi-static and dynamic condition, without damaging the structure of the samples. Automobile manufacturers have been investigating the mechanical properties of SMA for many years. General Motors has developed a prototype device that does precisely this using shape memory alloys (SMAs). A SMA is an alloy that can be made to have two different shapes depending on temperature, a so-called home state shape when it’s hot and a second state when it’s cool. one of the renowned company General Motors (GM) declared that their engineers have been working on SMA applications since the mid-1990s. So far, 60 U.S. patents have been issued to the automaker and more than 100 other patents are pending [23]. GM has an insight of utilizing SMA in producing an electric generator to make electricity by using exhaust heat, louver to control the airflow and grab handle of vehicle doors to open simply [24]. And using SMA in simplifying the bonnet lifting system to protect pedestrian without performance reduction [25]. According to the subjected essays, it illustrates that there are a few potential applications which can be implemented and economically possible. However, the critical circumstances such as longevity other have to be considered. Many researchers have challenged with the feasibility of making automobile batteries from NiTi alloys. Leary et al. [26] calculated and experimented the electrical resistivity of a linear NiTi actuator and assessed with a standard automotive battery. Hu et al. [27] have found that upholding the Sn anodes with NiTi alloy can perch on the large volume of Sn anodes because of reaction with lithium to decrease the internal stress and closing cracks in Sn anodes. This can lead the battery to have a stable cycleability (630 mA h g1 after 100 cycles at 0.7 C).