Browsing by Author "Upadhyaya, Hari M."

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    Atomic scale friction studies on single crystal gallium arsenide using atomic force microscope and molecular dynamics simulation
    (Springer, 2021-07-10) Fan, Pengfei; Goel, Saurav; Luo, Xichun; Upadhyaya, Hari M.
    This paper provides a fresh perspective and new insights on the nanoscale friction investigated using molecular dynamics simulation and atomic force microscope (AFM) nanoscratch experiments. The work considered Gallium Arsenide, an important III-V direct bandgap semiconductor material residing in the zinc-blende structure as a reference sample material due to its growing usage in 5G communication devices. In the simulations, the scratch depth was tested as a variable in the fine range of 0.5 nm to 3 nm to understand the behaviour of material removal as well as to gain insights into the nanoscale friction. Scratch force, normal force and average cutting forces were extracted from the simulation to obtain two scalar quantities namely, the scratch cutting energy (defined as the work done in removing a unit volume of material) and kinetic coefficient of friction (defined as the force ratio). A strong size effect was observed for scratch depths below 2 nanometres from the MD simulations and about 15 nm from the AFM experiments. A strong quantitative corroboration was obtained between the MD simulations and the AFM experiments in the specific scratch energy and more qualitative corroboration with the pile up and the kinetic coefficient of friction. This conclusion suggested that the specific scratch energy is insensitive to the tool geometry and the speed of scratch used in this investigation but the pile up and kinetic coefficient of friction are dependent on the geometry of the tool tip
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    Horizons of modern molecular dynamics simulation in digitalized solid freeform fabrication with advanced materials
    (Elsevier, 2020-09-22) Goel, Saurav; Knaggs, Michael; Goel, Gaurav; Zhou, Xiaowang W.; Upadhyaya, Hari M.; Thakur, Vijay Kumar; Kumar, Vinod; Bizarri, Gregory; Tiwari, Ashutosh; Murphy, Adrian; Stukowski, Alexander; Matthews, Allan
    Our ability to shape and finish a component by combined methods of fabrication including (but not limited to) subtractive, additive, and/or no theoretical mass-loss/addition during the fabrication is now popularly known as solid freeform fabrication (SFF). Fabrication of a telescope mirror is a typical example where grinding and polishing processes are first applied to shape the mirror, and thereafter, an optical coating is usually applied to enhance its optical performance. The area of nanomanufacturing cannot grow without a deep knowledge of the fundamentals of materials and consequently, the use of computer simulations is now becoming ubiquitous. This article is intended to highlight the most recent advances in the computation benefit specific to the area of precision SFF as these systems are traversing through the journey of digitalization and Industry-4.0. Specifically, this article demonstrates that the application of the latest materials modelling approaches, based on techniques such as molecular dynamics, are enabling breakthroughs in applied precision manufacturing techniques.
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    Resilient and agile engineering solutions to address societal challenges such as coronavirus pandemic
    (Elsevier, 2020-05-28) Goel, Saurav; Hawi, Sara; Goel, Gaurav; Thakur, Vijay Kumar; Agrawal, Anupam; Hoskins, Clare; Pearce, Oliver; Hussain, Tanvir; Upadhyaya, Hari M.; Cross, Graham; Barber, Asa H.
    The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, India, and most of Europe continue to be in a state of lockdown. The worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. Lockdowns became necessary as a preventive measure to avoid the spread of the contagious and infectious “Coronavirus Disease 2019” (COVID-19). This newly identified disease is caused by a new strain of the virus being referred to as Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS CoV-2; formerly called 2019-nCoV). We review the current medical and manufacturing response to COVID-19, including advances in instrumentation, sensing, use of lasers, fumigation chambers and development of novel tools such as lab-on-the-chip using combinatorial additive and subtractive manufacturing techniques and use of molecular modelling and molecular docking in drug and vaccine discovery. We also offer perspectives on future considerations on climate change, outsourced versus indigenous manufacturing, automation, and antimicrobial resistance. Overall, this paper attempts to identify key areas where manufacturing can be employed to address societal challenges such as COVID-19.