Mechanical Engineering

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Shiv Nadar University

Bioimplants are susceptible to simultaneous wear and corrosion degradation in the aggressive physiological environment. High entropy alloys with equimolar proportion of constituent elements represent a unique alloy design strategy for developing bioimplants due to their attractive mechanical properties, superior wear, and corrosion resistance. In this study, the tribo-corrosion behavior of an equiatomic MoNbTaTiZr high entropy alloy consisting of all biocompatible elements was evaluated and compared with 304 stainless steel as a benchmark. The high entropy alloy showed a low wear rate and a friction coefficient as well as quick and stable passivation in simulated body fluid. An increase from room temperature to body temperature showed excellent temperature assisted passivity and nobler surface layer of the high entropy alloy, resulting in four times better wear resistance compared to stainless steel. Stem cells and osteoblast cells displayed proliferation and migratory behavior, indicating in vitro biocompatibility. Several filopodia extensions on the cell periphery indicated early osteogenic commitment, and cell adhesion on the high entropy alloy. These results pave the way for utilizing the unique combination of tribo-corrosion resistance, excellent mechanical properties, and biocompatibility of MoNbTaTiZr high entropy alloy to develop bioimplants with improved service life and lower risk of implant induced cytotoxicity in the host body. ©

World University root node

(SoE) School of Engineering

ACS Applied Bio Materials

Biocompatible High Entropy Alloys with Excellent Degradation Resistance in a Simulated Physiological Environment

Urban Air Mobility (UAM) is a long-desired service which will revolutionize the present transportation facilities, by introducing air mobility for on-demand aviation. Due to the continuous increase in population, road traffic is increasing at alarming rates and the problem of congestion is also increasing in metro cities. These new services will provide improved ways for individuals to go around urban communities and urban territories while decreasing blockage. eVTOLs are aircraft that are capable of Vertical Take-off and Landing (VTOL) with no requirement of run-up space and are tremendously getting popular when it comes to UAM due to the important factor of clean propulsion with zero-emission. The industry is rapidly proposing and adopting new vehicle concepts to meet consumer demands and hence conceptually designing these vehicles with basic guidelines will set a preliminary foundation for more innovative technologies to come. This research work sets a baseline procedure and an initial iteration example for the industries and upcoming companies in this sector hence focuses on the Conceptual designing of eVTOLs. The novelty of the presented work lies in enhanced eVTOL configuration using coaxial ducted tilt rotors with wings. © 2020 IEEE.

Proceedings of the 4th International Conference on Electronics, Communication and Aerospace Technology, ICECA 2020

Baseline procedure for conceptual designing of an eVTOL for Urban Air Mobility

The present work deals with the nonlinear stability characteristics of geometrically imperfect shear deformable functionally graded plates (FGP) subjected to thermo-mechanical loads. The equilibrium, stability, and compatibility equations are derived using trigonometric shear-strain function based refined shear deformation plate theory. The displacement field used in the present study has been employed for FGP for the first time. The in-plane and transverse displacements consist of bending and shear components, whereas the displacement field contains only four unknowns. Geometric nonlinearity has been incorporated in the formulation in a von-Karman sense. A generalized porosity model has also been developed to accommodate both even and uneven porosity distribution reported in the literature. Various models of geometric imperfection have been modeled using imperfection function. An exact expression for the critical buckling load and critical buckling thermal load of geometrically imperfect porous FGPs for various loading conditions have been developed. After ensuring the excellent accuracy of the developed expression, the influence of geometric imperfection, porosity inclusion, and geometric configuration on the nonlinear stability of FGPs has been discussed extensively. The results presented in this paper will be used as a benchmark for future research. © IMechE 2020.

Fulltext

Journal of Strain Analysis for Engineering Design

Microstructure/geometric imperfection sensitivity on the thermo-mechanical nonlinear stability behavior of functionally graded plates using four variable refined structural kinematics

AIAA Journal

Geometric nonlinear analysis of composite stiffened panels using variational asymptotic method

A novel and strategic green energy production method that utilizes relative wind generated from moving vehicles is presented. A speeding train generates an enormous wake of wind around it, which stocks a substantial amount of kinetic energy. In this study, this freely accessible wind power is harvested by installing a modified savonius wind turbine within the slipstream region of the train. A computer-oriented fluid-solid integrate simulation of wind turbine propelled by train-induced wind is performed by executing all physically realistic boundary conditions. The numerical study is based on open-source CFD toolbox OPENFOAM, and the results were validated against benchmark experimental study. Parametric sensitivity analysis such as optimal turbine performance within the slipstream regime, torque prediction from express trains, two opposite crossing trains, tunnel condition, and turbine wind turbine clusters arrangement has been reported. This study enhances the understanding of the power generation by the turbine from the train slipstream which is not reported in any open literature as far as the authors’ present knowledge goes. Copyright © 2020 by ASME

Mathematics

(SoNS) School of Natural Sciences

Journal of Energy Resources Technology, Transactions of the ASME

A Numerical study toward harvesting power from train slipstream using savonius rotor

Opportunistic maintenance approaches deal with performing group preventive maintenance (PM) on the other units in a series system due to the intervention of any scheduled PM of a component. Simultaneous maintenance actions show better economic performance due to the direct reduction of downtime costs and production losses. However, it is uneconomical to perform maintenance on all units simultaneously. To address this issue, various simulation and optimization approaches including Markov chains, genetic algorithm etc. have been applied in order to achieve optimum solutions in group maintenance models. However, most of these strategies suffer from intractability as the problem size increases. In the present paper, we develop an efficient opportunistic grouping methodology for the multi-unit series system while considering imperfect preventive maintenance. The aim is to obtain an optimum PM interval and grouping of units to minimize the expected total system maintenance cost per unit time during the mission. A recently developed meta-heuristic named ‘Jaya algorithm’ is applied to optimize the objective function. The effectiveness of the proposed approach is examined with three maintenance models: single unit model, mono-group model and the proposed opportunistic group model. Results reveal that the proposed group maintenance model results in 19\% cost savings as compared to the mono-group model and 71\% compared to the single component maintenance model. © 2019, Operational Research Society of India.

OPSEARCH

An opportunistic group maintenance model for the multi-unit series system employing Jaya algorithm

Jaya algorithm has recently been proposed, which is simple and efficient meta-heuristic optimization technique and has received a great attention in the world of optimization. It has been successfully applied to some thermal, design and manufacturing associated optimization problems. This paper aims to analyze the performance of Jaya algorithm for permutation flow-shop scheduling problem which is a well-known NP-hard optimization problem. The objective is to minimize the makespan. First, to make Jaya algorithm adaptive to the problem, a random priority is allocated to each job in a permutation sequence. Second, a job priority vector is converted into job permutation vector by means of Largest Order Value (LOV) rule. An exhaustive comparative study along with statistical analysis is performed by comparing the results with public benchmarks and other competitive heuristics. The key feature of Jaya algorithm of simultaneous movement towards the best solution and going away from the worst solution enables it to avoid being trapped in the local optima. Furthermore, the uniqueness of Jaya algorithm compared with any other evolutionary based optimization technique is that it is totally independent of specific parameters. This substantially reduces the computation effort and numerical complexity. Computational results reveal that Jaya algorithm is efficient in most cases and has considerable potential for permutation flow-shop scheduling problems. © 2020 by the authors; licensee Growing Science, Canada.

International Journal of Industrial Engineering Computations

A discrete jaya algorithm for permutation flow-shop scheduling problem

In the present article, the vibrational behaviour of a functionally graded plate (FGP) resting on elastic foundations under a thermal environment with geometric discontinuities and microstructural defects (porosity) has been investigated. The structural kinematics is based on the trigonometric shear-strain function with only four unknowns. The transverse shear stress varies nonlinearly along the thickness. The FGP has geometric discontinuities in the form of a circular cut-out of different dimensions at the centre. The various geometric imperfections are modelled using a generic function, whereas the microstructural defects (porosity) have been included using modified power law. The temperature variation between the surfaces is nonlinear along the thickness direction. The FEM-based solutions are presented using C0 continuous iso-parametric element. Convergence and validation study have been carried out to demonstrate the efficacy and reliability of the presented results. The effect of porosity inclusion, circular cut-out, elastic foundation, thermal environment, geometric imperfection modes and the volume fraction index have been analysed under conventional and unconventional boundary constraints. It is observed that after a specific dimension of circular cut-out, vibrational behaviour of FGPs exhibits nonlinearity in nature. © 2020, The Brazilian Society of Mechanical Sciences and Engineering.

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Influence of geometric discontinuities and geometric/microstructural defects on the temperature-dependent vibration response of functionally graded plates on elastic foundation

Owing to its good biocompatibility and low cost, stainless steel is one of the most widely utilized biomaterial. However, longtime assessment of stainless steel has shown problems related to material degradation, especially localized corrosion and bio-film formation. In addition, the leaching of toxic nickel and chromium ions from stainless steel leads to additional health complications. Here, we utilized submerged friction stir processing, a severe surface deformation technique for significantly enhancing its durability, bio-activity as well as antibacterial resistance. The processing was done with a wide variation in strain rates to produce tunable surface microstructure. High strain-rate processing resulted in nearly single-phase fine-grained microstructure, while slow strain-rate processing developed a dual-phase fine-grained microstructure. The bio-corrosion rate of processed steel was reduced by more than 60 \% along with significant enhancement in the pitting resistance. The processed steel showed nearly no bacterial adhesion/biofilm formation, evaluated using S. aureus and E. coli bacterial strains. Further, the processed stainless steel surface demonstrated minimum leaching of the toxic elements, significantly enhancing its appeal for bio-implant applications. The observed behavior was explained based on the formation of a stable passive layer, rich in Cr2O3, as determined using x-ray photoelectron microscopy (XPS) and increased hydrophilicity. © 2020 Elsevier B.V.

Colloids and Surfaces B: Biointerfaces

Enhanced durability, bio-activity and corrosion resistance of stainless steel through severe surface deformation

Here, an excellent cavitation erosion-corrosion resistance of stainless steel using a novel severe surface deformation technique, reciprocating friction processing (RFP) was demonstrated. The RFP treated stainless steel showed nano-grained, nano-twinned microstructure along with high dislocation density. The RFP treated steel significantly surpassed the performance of advanced structural materials including high entropy alloy (Al0.1CoCrFeNi) and complex concentrated alloy (SiC reinforced Al0.1CoCrFeNi), demonstrating the lowest cavitation erosion and cavitation erosion-corrosion rates for this class of materials. The RFP treated steel demonstrated outstanding corrosion behavior in 3.5\% NaCl solution as well. The unusual performance of RFP treated steel is attributed to its excellent mechanical strength and strong passivating behavior. © 2020 Elsevier B.V.