Browsing by Author "Stukowski, Alexander"

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    Atomistic investigation on the structure-property relationship during thermal spray nanoparticle impact
    (Elsevier, 2013-12-31) Goel, Saurav; Faisal, Nadimul Haque; Ratia, Vilma; Agrawal, Anupam; Stukowski, Alexander
    During thermal spraying, hot particles impact on a colder substrate. This interaction of crystalline copper nanoparticles and copper substrate is modeled, using MD simulation. The quantitative results of the impacts at different velocities and temperatures are evaluated using a newly defined flattening aspect ratio. This ratio between the maximum diameter after the impact and the height of the splat increases with increasing Reynolds numbers until a critical value is reached. At higher Reynolds numbers the flattening aspect ratio decreases again, as the kinetic energy of the particle leads to increasing substrate temperature and, therefore, decreases the substrate resistance. Thus, the particle penetrates into the substrate and deforms less.
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    Comment on "Incipient plasticity of diamond during nanoindentation" by C. Xu, C. Liu and H. Wang, RSC Advances, 2017, 7, 36093
    (Royal Society of Chemistry, 2018-01-31) Goel, Saurav; Stukowski, Alexander
    A recent molecular dynamics simulation study on nanoindentation of diamond carried out by Xu et al. 1 has reported observation of the presence of a controversial hexagonal lonsdaleite phase of carbon in the indentation area. In this comment, we question the reported observation and attribute this anomaly to shortcomings of the long range bond order potential (LCBOP) employed in the nanoindentation study.
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    Designing nanoindentation simulation studies by appropriate indenter choices: Case study on single crystal tungsten
    (Elsevier, 2018-06-22) Goel, Saurav; Cross, Graham; Stukowski, Alexander; Gamsjäger, Ernst; Beake, Ben D.; Agrawal, Anupam
    Atomic simulations are widely used to study the mechanics of small contacts for many contact loading processes such as nanometric cutting, nanoindentation, polishing, grinding and nanoimpact. A common assumption in most such studies is the idealisation of the impacting material (indenter or tool) as a perfectly rigid body. In this study, we explore this idealisation and show that active chemical interactions between two contacting asperities lead to significant deviations of atomic scale contact mechanics from predictions by classical continuum mechanics. We performed a testbed study by simulating velocity-controlled, fixed displacement nanoindentation on single crystal tungsten using five types of indenter (i) a rigid diamond indenter (DI) with full interactions, (ii) a rigid indenter comprising of the atoms of the same material as that of the substrate i.e. tungsten atoms (TI), (iii) a rigid diamond indenter with pairwise attraction turned off, (iv) a deformable diamond indenter and (v) an imaginary, ideally smooth, spherical, rigid and purely repulsive indenter (RI). Corroborating the published experimental data, the simulation results provide a useful guideline for selecting the right kind of indenter for atomic scale simulations.
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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.