Mechanical Engineering

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In the present article, an exact solution has been given to investigate the influence of porosity inclusion, boundary conditions, and volume fraction index on the vibration response of functionally graded material (FGM) plates using the dynamic stiffness method (DSM). The material properties of FGM are continuously changing along the thickness direction of plates according to the power law with even porosity inclusion. Classical plate theory (CPT) along with the concept of a physical neutral surface is employed to develop the governing differential equation of motion by using Hamilton's principle. The levy type (closed form) solution is used to develop the dynamic stiffness matrix. The Wittrick-Williams algorithm has been employed to compute the exact natural frequency of the FGM plates with porosity inclusion. The efficacy and authenticity of the present formulation have been ascertained by comparing the present results with those of the literature. A comprehensive parametric study has been performed to compute the influence of various geometric and boundary configurations on the vibration response of the FGM plates. © 2022, The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.

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(SoE) School of Engineering

International Journal on Interactive Design and Manufacturing

Effect of porosity inclusions on the natural frequencies of the FGM plates using dynamic stiffness method

Synthetic superhydrophobic surfaces have drawn significant interest owing to their water-resistant and self-cleaning applications. However, most of the fabrication practices involve complex processes that are unsustainable to withstand large-scale fabrication to transform into standard industrial practice. The desired durability of these surfaces is another crucial challenge that makes the translation of these products difficult. In this paper, we reported the fabrication of superhydrophobic aluminum alloy with a simpler, low-cost, and eco-friendly technique using the hydrothermal treatment. Subsequently, the surface energy of the processed substrate was modulated using a chemical vapor deposition technique. The developed surface shows an extreme water repellency with a contact angle above 160° and a very low contact angle hysteresis and rolling angle (<5°). Surface morphological characterizations showed the formation of nanoscale hierarchical structures which resulted in a stable Cassie state due to the effective entrapment of air and exhibiting self-cleaning ability. The developed surface showed extreme wetting resilience during exposure to a droplet impingement with an impinging velocity of >2 m/s. Further, these superhydrophobic surfaces were exposed to atmospheric weather conditions to check their robustness. During a rain simulator testing, a developed surface showed low contact angle hysteresis (<10°) after enduring multiple cycles. The processed surface also showed significant de-wetting behavior during condensation experiments and chemical resistance under prolonged exposure. Weathering tests performed under outdoor conditions showed an insignificant influence on the de-wettability of the processed sample. The present study highlights the fabrication of superhydrophobic durable metallic surfaces through a facile and green fabrication route for multifunctional applications. © IMechE 2021.

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology

Eco-friendly and facile fabrication of superhydrophobic aluminum alloy

In the current study, we report an excellent high temperature oxidation resistance of AlCoCrFeNi high entropy alloy (HEA) following surface modification. The surface properties of HEA were tailored through a severe surface deformation technique. The as cast HEA exhibited coarse grain B2/BCC microstructure. In contrast, processed specimen showed significant grain refinement along with B2/BCC to FCC phase-transition. The processed specimen demonstrated 11-67% reduction in the oxidation kinetics. Cr2O3 and Al2O3 were the predominant oxides formed in all the oxidized specimens. In addition, Cr, Fe and Co rich spinels were also found in the as cast oxidized specimens. The superior oxidation resistance of the processed specimen is attributed to the microstructural refinement resulting in the formation of protective dense chromia layer. © 2022 Walter de Gruyter GmbH, Berlin/Boston 2022.

Corrosion Reviews

Improving the high temperature oxidation resistance of high entropy alloy by surface modification

The turbulent melting characteristics of hybrid nano-enhanced phase change material (HNEPCM) in a three-dimensional rectangular enclosure has been numerically investigated. The lower and upper walls are partially heated and cooled using constant surface temperature boundary condition and the other surfaces are specified with adiabatic boundary condition. The rectangular enclosure is filled with molten salt phase change material (PCM) of potassium nitrate (KNO3) with melting temperature of 334 °C. The transient melting rates of PCM are investigated by dispersing hybrid mono-dispersed spherical nanoparticles of Aluminum oxide (Al2O3) combined with Silicon dioxide (SiO2), Titanium dioxide (TiO2) and Multi-walled carbon nanotubes (MWCNT). The Rayleigh number (Ra) and particle volume fraction (ϕ) are varied in the range of 106≤Ra≤1010 and 2%≤ϕ≤5%. The turbulent phase change process of PCM is modeled using enthalpy–porosity approach with Lam–Bremhorst k−ϵ turbulence model. The three-dimensional governing equations are discretized using Finite difference technique and computations are carried out using Fortran 90 in-house code. The stronger thermal buoyancy force accelerates the melting rate and the melting pattern indicates the accumulation of large quantity of molten metal in the upper regions of the rectangular enclosure. The average melting velocity and turbulent kinetic energy of pure KNO3 PCM is increased by 51.17% and 77.84% by the addition of Al2O3−MWCNT hybrid nanoparticles. The impact of hybrid nanoparticles on the melting rate and thermal performance of PCM is significant in higher Rayleigh number flows than transitional flows. The present results are validated and are in close agreement with the benchmark experimental results. © 2022 Elsevier Ltd

Journal of Energy Storage

Turbulent melting characteristics of hybrid nano-enhanced molten salt phase change material in rectangular enclosure

Environmental Science and Pollution Research

Performance enhancement of the photovoltaic system with different cooling methods

The condition for the formation of droplet groups in liquid sprays is poorly understood. This study looks at a simplified model system consisting of two iso-propanol droplets of equal diameter, Dd0, in tandem, separated initially by a center-to-center distance, a20, and moving in the direction of gravity with an initial velocity, Vd0 &gt; Vt, where Vt is the terminal velocity of an isolated droplet from Stokes flow analysis. A theoretical analysis based on Stokes flow around this double-droplet system is presented, including an inertial correction factor in terms of drag coefficient to account for large Reynolds numbers (≫1). From this analysis, it is observed that the drag force experienced by the leading droplet is higher than that experienced by the trailing droplet. The temporal evolutions of the velocity, Vd (t), of the droplets, as well as their separation distance, a2 (t), are presented, and the time to at which the droplets come in contact with each other and their approach velocity at this time, ∆Vd0, are calculated. The effects of the droplet diameter, Dd0, the initial droplet velocity, Vd0, and the initial separation, a20 on to and ∆Vd0 are reported. The agreement between the theoretical predictions and experimental data in the literature is good. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Fulltext

Fluids

An Analytical Study on the Mechanism of Grouping of Droplets

Environmental Progress and Sustainable Energy

Performance analysis based on energy and exergy output of double slope passive and active solar still

In the present paper, thermo-mechanical stability analysis of geometrically imperfect porous functionally graded plates (FGP) with geometric nonlinearity is presented. The equilibrium, stability, and compatibility equations are derived using Logarithmic structural kinematics in conjunction with the von-Karman type of geometric nonlinearity. A logarithmic-based shear-strain function has been used for the first time for the buckling response of functionally graded material (FGM) plates. Generic imperfection function has been implemented to incorporate the various imperfection modes like sin-type or global type in the formulation. The effective materials properties of the plates with porosity inclusion have been computed using modified power law. The plate is subjected to uniaxial and biaxial compression as well as combined compression and tension along with thermal loading. An exact expression for the critical buckling load and critical buckling thermal load of geometrically imperfect porous FGM plate for each loading case has been developed. After confirming the excellent accuracy of the current exact solutions, the effect of geometric imperfection, porosity inclusion, and geometric configurations on the nonlinear stability of the FGM plate have been discussed extensively. The results presented in this paper will be used as a benchmark for future research. © 2022 Wiley-VCH GmbH.

ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik

Thermo-mechanical nonlinear stability analysis of geometrically imperfect functionally graded plates with microstructural defects using logarithmic structure kinematics: An unified expression

Linear vibratory feeder is one of the most extensively used part feeding systems in a production line. The part motion on the feeder can be sliding or hopping or a combination of these two. Based on the dynamics of part motion this paper identifies three distinct regimes. A mathematical model was developed that can predict the trend in conveying velocity in these regimes. This model can provide the parts position as a function of time and has considered relative displacement between the part and the conveying surface. The simulation was validated by performing experiments for a range of vibration frequencies and amplitudes. © IMechE 2022.

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

Part dynamics in the intermediate regime of a linear vibratory feeder

Inspired by many biological systems such as lotus leaves, insect wings and rose petals, great attention has been devoted to the study and fabrication of artificial superhydrophobic surfaces with multiple functionalities. In the present study, a simple and ecological synthesis route has been employed for large scale fabrication of self-assembled, sustainable nanostructures on unprocessed and micro imprinted aluminum surfaces named ‘Nano’ and ‘Hierarchy’. The processed samples show extreme wettability ranging from superhydrophilicity to superhydrophobicity depending on post-processing conditions. The densely packed ellipsoidal nanostructures exhibited superhydrophobicity with excellent water, bacterial and dust repellency when modified by low surface energy material 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTES), characterized by a static contact angle of 163 ± 1° and contact angle hysteresis (CAH) ~3°. These coated surfaces show significant corrosion resistance with current density of 6 nA/cm2 which is 40 times lower than unprocessed counterpart and retain chemical stability after prolonged immersion in corrosive media. These surfaces show excellent self-cleaning ability with significantly low water consumption (&lt; 0.1 µl/mm2-mg) and prevent biofouling which ensures its applicability in biological environment and marine components. The nanostructured superhydrophilic aluminum shows maximum antibacterial activity due to disruption of cell membrane. This work can offer a simple strategy to large scale fabrication of multifunctional biomimetic metallic surfaces. © 2021