Mechanical Engineering

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In this paper, molecular dynamic (MD) simulation was employed to simulate the AFM tip-based nanoscratching process on multilayer graphene to investigate graphene deformation and coefficient of friction (COF). MD Simulation results showed cross-linking structures were created at the interface of two-layer graphene during nanoindentation and nanoscratching. The loading force had a characteristic of a periodic wave crest-trough transition. The COF of the diamond tip fluctuated at around 0.15 during nanoscratching process. © 2021 Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021. All rights reserved.

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Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021

Molecular dynamics simulation of AFM tip-based nanoscratching of multi-layer graphene

A comprehensive study to understand important parameters that affects the Cavity Linear Receiver (CLR) performance has been done. In this paper, the combined optical and thermal analysis has been successfully utilized, to investigate the thermal-hydraulic behavior of CLR of cross-linear CSP (CL-CSP) system, which is developed at the Tokyo Institute of Technology proposed a new CSP technology, which is called Cross Linear Concentrating Solar Power (CL-CSP). The first demonstration plant of cross-linear concept has been installed at Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal (23.2599° N, 77.4126° E), the combined analysis was done using a numerical model, which has been validated with literature and experimental test. The numerical model simulates the thermal-hydraulic behavior of CLR with the variation of working condition, surface property, and geometry. The optical efficiency and thermal efficiency are the main performance parameters for the simulation. From the numerical study, distribution of both solar flux and temperature on the receiver tubes shows high non-uniformity in axial and radial direction. Furthermore, the parameters effect on the CLR performance is investigated under general working condition of receiver of 673 K temperature, 0.0925 kg/s mass flow rate, and during solar noon of summer solstice. © 2020 Elsevier Ltd

Energy

Numerical analysis of cavity receiver with parallel tubes for cross-linear concentrated solar system

GaAs is a hard, brittle material and its cutting at room-temperature is rather difficult, so the work explored whether hot conditions improve its cutting performance or not. Atomic force microscope (AFM) tip-based hot machining of the (0 1 0) oriented single crystal GaAs was simulated using molecular dynamics (MD). Three representative temperatures 600 K, 900 K and 1200 K (below the melting temperature of ~1511 K) were used to cut GaAs to benchmark against the cutting performance at 300 K using indicators such as the cutting forces, kinetic coefficient of friction, cutting temperature, shear plane angle, sub-surface damage depth, shear strain in the cutting zone, and stress on the diamond tip. Hotter conditions resulted in the reduction of cutting forces by 25% however, the kinetic coefficient of friction went up by about 8%. While material removal rate was found to increase with the increase of the substrate temperature, it was accompanied by an increase of the sub-surface damage in the substrate. Simulations at 300 K showed four major types of dislocations with Burgers vector 1/2<110>, 1/6<112>, <0–11> and 1/2<1–12> underneath the cutting zone and these were found to cause ductile response in zinc-blende GaAs. Lastly, a phenomenon of chip densification was found to occur during hot cutting which referred to the fact that the amorphous cutting chips obtained from cutting at low temperature will have lower density than the chips obtained from cutting at higher temperatures. © 2021

Fulltext

Materials Science in Semiconductor Processing

Molecular dynamics simulation of AFM tip-based hot scratching of nanocrystalline GaAs

Insights into the biological channels and synthetic pore-forming assemblies have elucidated many fundamental aspects of selective water and solute transport over the last few decades. This has led to the development of novel technologies with unique selectivity and permeability. In terms of membrane separation technology, this development has proceeded by adapting either of two approaches: (i) one where biological channel proteins are reconstituted in suitable materials mimicking the biological bilayer membrane and (ii) one where selective transport is mimicked in synthetic structures. The development of water filtration membranes in the former approach takes advantage of aquaporin proteins as representative building blocks and that of carbon nanotubes and molecular pore-forming assemblies in the latter approach. The first approach is often referred to as the field dominated by biomimetic membranes and the latter referred to as artificial water channels. In this study, a bibliometric analysis was conducted to investigate trends in these two areas based on growing publication trends, peer-reviewed journal selection, countries, institutions, authors, and collaborative networks. A total of 3199 records available from Scopus between 1962 and 2021 were extracted and analyzed. The results showed strong international collaborations and highlighted leading researchers and hubs of excellence in these two areas. This is very timely considering that the UN climate change conference (COP26) in Glasgow, UK later this year will bring focus to the global need for water treatment technologies. This work can serve as a quick reference for early-career researchers and industries working in the area of membrane development for water purification/filtration. © 2021, The Author(s).

npj Clean Water

A bibliometric study on biomimetic and bioinspired membranes for water filtration

This paper proposes an analytical model for predicting grinding-induced sub-surface damage depth in a silicon wafer. The model integrates the dislocation kinetics for crack initiation and fracture mechanics for crack propagation for the first time. Unlike other conventional models, the proposed model considers the effects of strain rate on damage depth and the dynamically changing metastable phase change properties. The model is verified by grinding experiments and a comparison of theoretical and experimental results shows a good quantitative agreement. It is found that increasing grinding speed and decreasing depth of cut cause a higher strain rate so as to enhance material brittleness, which is favorable to achieving low sub-surface damage. These findings will pave a way towards optimizing the grinding parameters and greatly improving the production efficiency of hard and brittle materials. © 2021 CIRP

CIRP Journal of Manufacturing Science and Technology

An analytical model to predict the depth of sub-surface damage for grinding of brittle materials

Finding lightweight materials that are suitable for high-strength impact application is imperative. However, incorporating empirical methods for the same can be an exorbitant affair. This study aims to obviate these experimental methods and replace them with a numerical approach to the problem using the finite element method (FEM) in tandem with mean-field homogenization. CNT and BNNT nano-fillers were used in the polymer matrix for the sake of comparison of dynamical response. The preliminary step involves finding material properties of composite panels having different configurations and concentration of nanofillers both computationally and experimentally. Later, an explicit dynamic based finite element analysis was performed to simulate the low-velocity impact on each of the composite plate developed. Finally, temporal responses of the plate such as contact force, displacement, and velocity after the impact were illustrated and compared for both CNT and BNNT composite plates for different heterogeneities of fibre. © 2021 Elsevier Ltd

Materials Today Communications

Mean-field homogenization coupled low-velocity impact analysis of nano fibre reinforced composites

Voice disorders are common physiological challenges that arise largely due to vocal fatigue, i.e. fatigue of vocal folds and associated phonatory structures. Since the incurrence of fatigue in vocal folds directly depends on the qualitative and quantitative nature of the dynamical signature of vocal fold oscillations, the hitherto literature has resorted to estimating the time histories and stress histories of the vocal fold oscillations. Often, vocal fold dynamics are rid with different types of complexities. Therefore, the literature often resorts to the use of a mathematical model that closely resembles the human phonatory system. Modelling the mechanism of vocal folds as a two-mass model with 2DOF provides a reasonably accurate depiction of the same. In order to obtain the real-time histories of the vocal fold vibrations, a continuously changing parameter called phonation threshold pressure (PTP) is defined so as to describe the extent of accumulated fatigue. PTP can be determined numerically for a given set of physical and physiological parameters of the system. Since the vocal fold vibrations are of varying amplitude as time progresses, it is necessary to use a standard counting algorithm for fatigue analysis, like the Rainflow-Counting algorithm. Then, the incurred damage is computed with the help of a S-N curve and the Miner’s rule. With the time span of phonation as the control parameter and PTP as a continuously changing parameter, the responses of the system are systematically obtained. Later, comparisons on the fatigue damage are made. © 2021, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Fatigue Analysis of Vocal-Folds Using Discretized Aeroelastic Model

In this research paper, vermicelli samples of 3 mm, 2 mm, and 1.25 mm diameters have been dried inside an even span greenhouse (1.2 × 0.8 m2 effective floor area) under forced convection mode in the climatic conditions of Rohtak, India (28°54′ N 76°34′E). The vermicelli samples were dried until safe moisture content was achieved. The present setup based on sustainable development due to thermal energy taken from sun, which has always an edge, compared to conventional drying in which high-grade energy (electric) is converted into low-grade energy (heat). The overall average values of thermal efficiency, energy efficiency, and exergy efficiency of greenhouse dryer for drying vermicelli were evaluated as 11.15\%, 34.83\% and 2.03\% respectively. Energy consumption and specific energy consumption of greenhouse dryer for drying vermicelli were found in the range of 0.279 to 0.539 kWh and 0.092 to 0.235 kJ/kg which was observed significantly lower than other drying methods. The drying kinetics of thin layer vermicelli has also been investigated. Lewis model was found to be most suitable to describe the thin layer drying behaviour of vermicelli drying under forced convection sustainable greenhouse drying mode. Practical applications. Traditionally, vermicelli is dried in open sun, but its colour and quality gets deteriorated due to exposure to ultraviolet rays, dust, animals, birds, rainfall etc. In industries, vermicelli is dried by electrical/hot air dryers, which consumes lot of energy and makes it costly. Therefore, a practical and advanced method of drying is essential to be developed. Greenhouse drying is an efficient, low cost and energy‐saving advanced technology, compared to the conventional hot air drying and open sun drying. This study proved to be feasible and efficient to work out an optimized drying condition for vermicelli drying under greenhouse, which could give a new path in vermicelli processing industry. The quality of dried vermicelli is good and can be stored for a long time. © 2021 Elsevier Ltd

Sustainable Energy Technologies and Assessments

Thermal performance and kinetic analysis of vermicelli drying inside a greenhouse for sustainable development

In the present article, the vibration response of geometrically imperfect functionally graded material (FGM) plates with geometric discontinuities and microstructural defects have been investigated. The structural kinematics used in the present study is based on logarithmic shear-strain function. A refined generalized porosity model has been developed to encompass even and uneven types of porosity models available in the literature. The geometric discontinuities have been assimilated in terms of a circular cutout of different sizes at the center of the plate. To incorporate the geometric imperfection, a generic function has been used. A C0 continuous iso-parametric finite element formulation has been used to attain the results whereas the accuracy of the present solution has been confirmed by comparing the results with the available literature. The analysis reveals that after a specific cutout radius, the FGM plates exhibit the nonlinear vibration characteristics. It has been observed that the influence of boundary conditions, cutout dimensions, geometric imperfections, and porosity inclusions on frequency parameters are significant. Most of the results presented in this paper are novel and may be treated as benchmark results for future reference. © 2021 Taylor & Francis Group, LLC.

Mechanics Based Design of Structures and Machines

Geometric/microstructural imperfection sensitivity in the vibration characteristics of geometrically non-uniform functionally graded plates with mixed boundary conditions

In the present work, we investigated the effectiveness of microwave processing and thermal spraying for developing tungsten carbide (WC)-based erosion-resistant claddings. The microwave cladding showed a columnar structure with a well-bonded interface compared to discrete splat morphology and discontinuous interface of the thermal spray coating. The cladding showed a lower hardness (800 HV) compared to thermal spray coating (1,300 HV) and a two times higher fracture toughness due to the absence of splat boundaries and pores. The microwave cladding also showed 14 times and 10 times higher cavitation erosion resistance than thermal spray coating and SS316L substrate steel, respectively. The improved cavitation erosion resistance of the microwave cladding is explained on the basis of the optimized combination of hardness and fracture toughness. The surface of eroded cladding showed plastically deformed micropits compared to the thermal spray coatings, which showed large craters. Results show that microwave claddings can help improve the durability of engineering systems. © 2021 Society of Tribologists and Lubrication Engineers.