Department of Mechanical Engineering

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The capability of Dielectric Elastomers (DEs) undergoing large deformation is limited by electromechanical instability arising because of the positive feedback between the applied electric field and the reduction in thickness of the elastomer. This paper theoretically analyzes the stability of a dielectric elastomer fiber composite made up of two soft incompressible DE phases in the quasi-static and dynamic modes of actuation. An energy method, which relies on the energy balance at the position of maximum overshoot in an oscillation cycle, is used for extracting the critical electric field and stretch in the dynamic mode. The material behaviors of the fiber and matrix phases are characterized by neo-Hookean energy density function of the elastomer. The results demonstrate that DE composite with higher fiber volume fraction exhibits higher electric field at the onset of instability in both static and DC dynamic modes of actuation. The results of the present investigation can find potential applications in the development and design of the soft electroactive actuators subjected to dynamic loading. © 2021 Elsevier Ltd. All rights reserved.

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Materials Today: Proceedings

Static and dynamic stability of dielectric elastomer fiber composites

In this work, vertically grown rod type ZnO nanostructures have been synthesized on metallic nickel tube films fabricated through the cost-effective process of electroforming. The use of tubular metal substrates for the growth of ZnO nanorods has been found to be advantageous for the photocatalytic degradation of EtBr dye because of their high surface area-to-volume ratio. The nickel tubes with ZnO nanorods were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The developed system was utilized for the photocatalytic degradation of EtBr dye and its efficacy was revealed through the comprehensive mineralization of the dye within 150 min. The mechanism of the degradation process has been revealed through total organic carbon (TOC), chemical oxygen demand (COD) and high-performance liquid chromatography (HPLC) studies. A substantially lower amount of the photocatalyst has been used because of the homogeneously distributed growth of nanorods on the substrate. Density functional theory-based analysis has also been performed to study the photocatalytic degradation and adsorption properties of EtBr on ZnO nanorods. Using first principles DFT theory, geometry optimizations and vibrational analysis are performed which show a negative charge transfer from the substrate to the photocatalyst. For the first time this article reports the use of DFT analysis for investigating the adsorption of EtBr on ZnO nanorods, and the experimental growth of nanorods over electroformed Ni tubes.

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High aspect ZnO nanorod growth over electrodeposited tubes for photocatalytic degradation of EtBr dye

The present work involves the fabrication of microtubes through the process of pulse electroforming by employing an in-house-developed micro-electroforming equipment. Theoretical modeling and simulation have demonstrated the role of cathode rotation and pulse waveform in ensuring uniformity of deposition. Nickel microtubes having wall thickness in the range of 8-144 µm have been successfully produced by varying the input parameters, viz. duty cycle and time of deposition. The fabricated micro-tubes have also been tested for their structural and mechanical characterization with the help of FESEM, EDAX, XRD, hardness testing, and surface roughness measurements. The electroformed Ni microtubes exhibit well aligned growth in the <111> direction with minimum crystallite size of 14 nm. The result demonstrates relation among duty cycle, crystallite size and hardness of the tubes. Moreover, the formulation of a multi-objective function and optimization utilizing two evolutionary algorithms, i.e., genetic algorithms and particle swarm optimization, are accomplished. An optimized parameter of 8 hours deposition time and 38.7% duty cycle is recommended. The results show the electroformed Ni tubes to possess geometries in microscale and crystallite size in nanoscale resulting in high hardness and good rigidity. © 2021, ASM International.

Journal of Materials Engineering and Performance

Fabrication and Characterization of Nickel Microtubes through Electroforming: Deposition Optimization Using Evolutionary Algorithms

In this work, metallic deposition with the help of electrochemical energy is performed with the in-house fabricated experimental set-up. Controlled deposition of nickel and graphite was carried out while varying electrodeposition process parameters namely, bath temperature, deposition time, current density, etc. to achieve optimum condition. The effects of graphite particles on surface morphologies, compositions, coating thickness were investigated by optical microscopy, SEM, EDS, and XRD. Results of XRD and SEM images show that graphite particles have been dispersed uniformly throughout the substrate. Optical microscopy images show the uniform average thickness with excellent surface finish which can be achieved at optimized process parameters such as; 10-minute deposition time, 4.0 pH value of the solution, 8?10 A dm-2 current density, and 40? C bath temperature under specific stirring condition. Further, thermal conductivity and tensile strength of electrodeposited sample have been evaluated. Thermal conductivity of the developed coated substrate is found to be greater than that of the platinum, Al-Ni alloys and silicon nitrides and hence it can be envisioned as potential substrate as micro heaters used in MEMS based applications. ? 2021 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Materials, Processing \& Characterization.

MATERIALS TODAY-PROCEEDINGS

Investigation of surface characteristics and effect of electrodeposition parameters on nickel-based composite coating

School of Management & Entrepreneurship

Information Systems Journal

Locating resistance to healthcare information technology: A Bourdieusian analysis of doctors' symbolic capital conservation

The present study aims at investigating the effect of submerged arc welding fluxes for enhanced corrosion resistance of structural steel welds. By varying the basicity index of submerged arc welding fluxes the corrosion resistance and mechanical properties of weld metal such as tensile strength, impact strength, microhardness in submerged arc weldments were evaluated. The result shows that with the increase in bascity index tensile strength of weld specimen reduced while impact strength and microhardness value increased. Maximum microhardness (288 HV) was observed for flux 2 while base metal show minimum microhardness value (205 HV). Flux 5 gives maximum impact strength (94.17 J) as compared to the base metal (80 J). This is due to the reduced content of oxygen in weld metal which increases the weld metal impact toughness. Corrosion resistance of weld specimen increased as compared to the base metal. Ductile fracture mode and shear lip or tears were observed in the weld zone. Shear dimples and shear lips were more severe in base metal as well as weld metal impact specimens due to the rapid effect of external forces on the impact test. The banded microstructure of delta ferrite and austenite was observed in the base metal. Fine grains of ferrite and pearlite at the center and edges were present in the weld zone. © IMechE 2020.

Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering

Experimental investigation of structural integrity behavior of High strength low alloy steel – Study of mechanical, microstructural and corrosion behavior of Submerged arc welding weldments

Numerical simulations are always dominant over experimental investigations in the field of flow analysis as they are simple, economical and take less time. It is better to analyze hypersonic flow problems like re-entry of a space vehicle using computational simulation as it takes less time and predict highly accurate results. The present work mainly emphases on analyzing the flow behavior in the vicinity of Apollo re-entry vehicle at hypersonic speeds using computational fluid dynamics. A numerical analysis of at altered Mach number and two angles of attack (0° and 10°) was studied. Ansys Fluent was used as a CFD tool for modeling the problem. Meshing of domain along with the appropriate boundary conditions was used to analyze the effects of changing boundary conditions on aerodynamic properties. The flow domain around module geometry was made ten times the dimension of module geometry to capture the shock formation effectively. Appropriate boundary conditions along with suitable meshing were used to start the simulation. The effect of altering Mach number with angle of attack on aerodynamic properties, i.e., pressure, density, and temperature was examined using contours and comparison graphs. © 2021, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Flow Simulation of Atmospheric Re-entry Vehicle at Varying Mach Number and Angle of Attack

Thin film sensor (TFS) is one of the most promising candidates for instantaneous temperature measurements owing to their extremely small response time (~milliseconds) aided with fair accuracy. Since they are capable of making quick and precise temperature measurements, they can be also used as heat flux gauges to measure surface heat fluxes in dynamic environments like high speed aerospace applications, gas turbine blades etc. Usual TFS are made by depositing a thin metallic film over insulating substrate. In this work we developed an Ag-Carbon nanotube (CNT) nanocomposite film as the sensing element of a TFS and compare it with pure Ag TFS, both having Macor as substrate. Static calibration established a better temperature coefficient of resistance (TCR) value i.e. better sensitivity, for the nanocomposite TFS. X-ray diffraction (XRD) and Energy Dispersive X-ray (EDX) studies are done to probe behind the increase in sensitivity of the nanocomposite TFS compared to its conventional metallic counterpart. © 2020 Elsevier Ltd