scholarly journals Preparation of bilayer shape memory intelligent hydrogel actuators and their structural characteristics

2020 ◽  
Vol 23 (1) ◽  
pp. 470-480
Author(s):  
Shengzhu Zhou ◽  
Qiang Zhou ◽  
Meng Wang ◽  
Zhihui Zhang ◽  
Luquan Ren
Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4824
Author(s):  
Alireza Tabrizikahou ◽  
Mieczysław Kuczma ◽  
Piotr Nowotarski ◽  
Małgorzata Kwiatek ◽  
Ahad Javanmardi

Every year, structural flaws or breakdowns cause thousands of people to be harmed and cost billions of dollars owing to the limitations of design methods and materials to withstand extreme earthquakes. Since earthquakes have a significant effect on sustainability factors, there is a contradiction between these constraints and the growing need for more sustainable structures. There has been a significant attempt to circumvent these constraints by developing various techniques and materials. One of these viable possibilities is the application of smart structures and materials such as shape memory and piezoelectric materials. Many scholars have examined the use of these materials and their structural characteristics up to this point, but the relationship between sustainability considerations and the deployment of smart materials has received little attention. Therefore, through a review of previous experimental, numerical, and conceptual studies, this paper attempts to draw a more significant relationship between smart materials and structural sustainability. First, the significant impact of seismic events on structural sustainability and its major aspects are described. It is then followed by an overview of the fundamentals of smart material’s behaviour and properties. Finally, after a comprehensive review of the most recent applications of smart materials in structures, the influence of their deployment on sustainability issues is discussed. The findings of this study are intended to assist researchers in properly addressing sustainability considerations in any research and implementation of smart materials by establishing a more explicit relationship between these two concepts.


2013 ◽  
Vol 738-739 ◽  
pp. 338-343 ◽  
Author(s):  
Francisco Manuel Braz Fernandes ◽  
Karimbi Koosappa Mahesh ◽  
Corneliu Marius Crăciunescu ◽  
João Pedro Oliveira ◽  
Norbert Schell ◽  
...  

The demand of emerging joining techniques for shape memory alloys (SMA) has become of great importance, as their functional properties, namely shape memory effect (SME) and superelasticity (SE) present unique solutions for state-of-the-art applications. Literature shows that significant efforts have been conducted on laser welding of these alloys, although very limited results concerning mechanical properties are repeatedly achieved. A better understanding of the mechanical behaviour of these welded joints may be got through a detailed analysis of the structural characteristics of the material from the base metal to the weld bead. Such studies have been carried out on a series of Ni-rich Ni-Ti SMA laser welded plates using synchrotron radiation.


2018 ◽  
Vol 203 ◽  
pp. 06005
Author(s):  
Azmi Mohammad Hassan ◽  
Raizal Saifulnaz Muhammad Rashid ◽  
Nazirah Ahmad ◽  
Shahria Alam ◽  
Farzad Hejazi ◽  
...  

Smart structures are defined as structures that able to adapt and maintain structural characteristics in dealing with changes of external disturbance, environment and unexpected severe loadings. This ability will lead to improve structural safety, serviceability and structural life extension. Shape memory alloys is one of the smart materials which has potential to be integrated in structural system to provide functions such as sensing, actuation, self-adapting and healing of the structures. The unique characteristic of shape memory alloys material is the ability to ‘remember’ its original shape after deformation. Nickel Titanium superelastic shape memory alloy wire is popular and widely used in many engineering fields and owned fully recovery of maximum strain of 6%-13.5% which is among the best shape recovery limit in alloy materials. The austenite finish temperature plays important role in stress-strain behaviour of superelastic shape memory alloys where higher stress required to complete martensite transformation with the increase of austenite finish temperature. The similar behaviour also is observed in the case of higher strain rate. The behaviour of superelastic shape memory alloys need to be studied before implementing in the structural system, so the targeted improvement for the structural system can be achieved.


Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1629
Author(s):  
Gheorghe Gurau ◽  
Carmela Gurau ◽  
Francisco Manuel Braz Fernandes ◽  
Petrica Alexandru ◽  
Vedamanickam Sampath ◽  
...  

It is generally accepted that severe plastic deformation (SPD) has the ability to produce ultrafinegrained (UFG) and nanocrystalline materials in bulk. Recent developments in high pressure torsion (HPT) processes have led to the production of bimetallic composites using copper, aluminum or magnesium alloys. This article outlines a new approach to fabricate multilayered Ni-Ti nanocomposites by a patented SPD technique, namely, high speed high pressure torsion (HSHPT). The multilayered composite discs consist of Ni-Ti alloys of different composition: a shape memory alloy (SMA) Ti-rich, whose Mf > RT, and an SMA Ni-rich, whose Af < RT. The composites were designed to have 2 to 32 layers of both alloys. The layers were arranged in different sequences to improve the shape recovery on both heating and cooling of nickel-titanium alloys. The manufacturing process of Ni-Ti multilayers is explained in this work. The evolution of the microstructure was traced using optical, scanning electron and transmission electron microscopes. The effectiveness of the bonding of the multilayered composites was investigated. The shape memory characteristics and the martensitic transition of the nickel-titanium nanocomposites were studied by differential scanning calorimetry (DSC). This method opens up new possibilities for designing various layered metal-matrix composites achieving the best combination of shape memory, deformability and tensile strength.


2019 ◽  
Vol 5 (7) ◽  
pp. 1465-1476 ◽  
Author(s):  
Jelan Hameed ◽  
Ali Laftah Abbas

Shape Memory Alloys (SMA) is type of smart materials that have ability to undergo large deformation and return back to their undeformed shape through heating (shape memory effect) or removal of load (superelastic effect). This unique ability is useful to enhance behavior of structure and seismic resistance. In this paper, superelasticity (SE) effect of NiTi alloys is used to improve the structural characteristics of steel building. The finite element analysis of steel building is done using ABAQUS v.2017. In order to compare the structural behavior of the steel building equipped with Shape Memory Alloy bars at beam-column connection, three steel building was modeled with a different combination of high strength steel bars and SMA bars. The steel building was checked for time history analysis by using Vrancea 1977 earthquake data. In order to estimate the recentring ability, residual of roof displacement and energy dissipation. The steel building equipped with SMA bars shows 82.7%, 152.72%   recovery in residual roof displacement for  steel building equipped with 50% SMA bars and 50% HS steel bars and steel building equipped with 100% SMA bars respectively, and moderate energy dissipation. In general, the frame equipped with 50% superelastic SMA bars and 50% HS steel bars provided better seismic performance.


Author(s):  
R. Gronsky

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.


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