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Functional Nanoceramics A Brief Review on Structure Property Evolutions of Advanced Functional Ceramics Processed Using Microwave and Conventional Techniques
Published in Sivashankar Krishnamoorthy, Krzysztof Iniewski, Nanomaterials, 2017
Santiranjan Shannigrahi, Mohit Sharma
There are a number of different types of smart fluids, but in each case, the viscosity of the material changes in response to the specific stimulus. One of the most well-known smart fluids is the toy Silly Putty, which is a type of non-Newtonian fluid. The viscosity of Silly Putty is dependent on the rate at which it is deformed; the faster it is deformed, the more viscous it becomes. Silly Putty is actually a type of silicone compound called polyborosiloxane, which consists of long-chain molecules with bulky side groups. When the material is deformed slowly, the structure can flow, but when deformed rapidly, the structure locks together, and the material can become very brittle! Other types of smart fluids rely on a suspension of very fine, micron-sized particles in a carrier liquid such as glycerol or mineral oil. In an electro-rheological fluid, the viscosity increases in the presence of an electrical field. In a magneto-rheological fluid, the viscosity changes in the presence of a magnetic field. In both cases, the smart fluid changes from a liquid to a solid with the application of the relevant field. The small particles in the fluid align and are attracted to each other, resulting in a dramatic change in viscosity. The effect takes milliseconds to occur and is completely reversible by the removal of the field.
Multifunctional Actuators Utilizing Magnetorheological Fluids for Assistive Knee Braces
Published in Yunhui Liu, Dong Sun, Biologically Inspired, 2017
For active actuators, especially for electric DC motors, brake function requires a large amount of power to maintain any posture and might cause safety problems. Some researchers have adopted smart fluids in actuation mechanisms; for instance, a rehabilitative knee orthosis equipped with electrorheological (ER) fluids-based actuators (Nikitczuk, Weinberg, and Mavroidis 2005). An orthopedic active knee brace using a magnetorheological (MR) fluids-based shear damper was developed to make the knee brace have controllable resistance (Ahmadkhanlou, Zite, and Washington 2007). All of the knee braces developed using smart fluids provide controllable torque by passive and semi-active means while consuming little power. Furthermore, according to clinical gait analysis (CGA), the knee joint dissipates power during walking (Zoss and Kazerooni 2006). Hence, the knee joint dynamics could be closely matched by a controlled energy-dissipative device; for example, smart fluids-based actuators. However, in some situations, such as going upstairs or stepping over obstacles, such knee braces do not help in active ways.
Vibration Control of Train Suspension Systems Via Mr Fluid Dampers
Published in Norman M. Wereley, Inderjit Chopra, Darryll J. Pines, Twelfth International Conference on Adaptive Structures and Technologies, 2017
The development of high-speed railway vehicles has been a great interest of many countries because high-speed trains have been proven as an efficient and economical transportation means while minimizing air pollution. However, the high speed of the train would cause significant car body vibrations, which induce the following problems: the ride stability, the ride quality, and the cost of track maintenance. Thus the vibration control of the car body is needed to improve the ride comfort and safety of a train. Various kinds of railway vehicle suspensions linking the bogies and the car bodies have been designed to cushion riders from vibrations. In recent years, semi-active suspension systems that utilize controllable devices based on smart fluids have drawn the attention of many researchers. The essential characteristics of the smart fluids are their abilities to reversibly change from a free-flowing fluid to a semi-solid with controllable yield strength in milliseconds when exposed to an electric or magnetic field [1]. Two fluids that are viable contenders for the development of controllable dampers are electrorheological (ER) and magnetorheological (MR) fluids [2].
Convective heat transport in yield stress nanofluids in a differentially heated square enclosure
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Naushad Hasin Khan, Md Ashique Hassan
Smart fluids, such as electrorheological and magnetorheological fluids, are utilized in many practical applications for example brakes, clutches, dampers, etc. Further, smart fluids (Elsaady, Oyadiji, and Nasser 2020; Gertzos, Nikolakopoulos, and Papadopoulos 2008) as well as drilling fluids (Wang, Guo, and Chen 2020) can be considered as yield stress fluid and modeled with Bingham rheological relation. Rapid cooling is desired from these yield stress fluids. Mixing of nanoparticles in these fluids could be an approach to enhance the cooling efficiency. Nanoparticle blended yield stress fluid is termed as yield stress nanofluid. To our knowledge, investigation of heat and fluid flow characteristics in yield stress nanofluid by considering Rayleigh Benard convection lacks in literature. Therefore, this work is motivated to fill this research gap. Study of natural convection in yield stress nanofluid filled differentially heated rectangular enclosure has been carried out. The rheology of the test fluid is modeled by Regularized Bingham relation. The sample fluids are seeded with multi-walled carbon nanotube (MWCNT). Effects of Rayleigh number, yield stress, nanoparticle volume fractions and Prandtl number on the natural convection of yield stress nanofluid have been investigated using finite volume-based algorithm.
Magnetorheological finishing of UHMWPE acetabular cup surface and its performance analysis
Published in Materials and Manufacturing Processes, 2020
Kunal Arora, Anant Kumar Singh
Therefore, in the present work, to overcome these challenges, an attempt is made to improve the finishing of the acetabular cup liner surface with the help of the magnetorheological finishing (MRF) process. The MRF process provides a fine grade of surface finish with a minimal scar.[20] The MRF process uses magnetorheological polishing (MRP) fluid. The MRP fluid includes the electrolytic iron particles (EIPs), polishing grade abrasives, and the carrier fluid.[21] Magnetorheological (MR) fluid is also known as smart fluid because on applying the magnetic field it changes its property from Newtonian fluid to non-Newtonian fluid, i.e., it becomes viscoelastic and external forces are controlled accordingly.[22] In the MRF process, the magnetic field act as the driving force. Once the magnetic field is applied, the magnetic EIPs move toward a higher concentration of magnetic flux (B), i.e., toward the tip of tool and abrasives, which are non-magnetic, move toward lower concentration of B, i.e., toward the work part surface. This is because of the magnetic field gradient amid the tool core tip and the work part surface which makes sure that the active abrasives of MRP fluid remains rich at the workpiece surface for effective finishing.[23] Also, the MR fluid-based finishing process does not leave pits or scratches on the surface. This is because in this process the material removal is determined by shear stresses as acted on the work part surface by active abrasive particles (AAPs) of the MRP fluid.[20] In this process, the normal force acting on the AAPs is very low and this leads to a clean and damage-free surface. In the present work, the hemispherical shape tip-based tool is utilized for improving the acetabular cup surface using the MR finishing process. Further, the optimum parameters of MR finishing process are predicted for the effective finishing of the UHMWPE acetabular cup surface and to check the effectiveness of the present process, surface morphology, circularity, and microhardness test are performed on the UHMWPE acetabular cup.