BITS Faculty Publications

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Author: search.filters.author.Sharma, AnujSubject: search.filters.subject.Molecular dynamics (MD)

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    Atomic scale insights into material removal mechanisms in nanoscale machining of copper beryllium
    (Sage, 2023-12) Kumar, Amit; Sharma, Anuj
    The heterogeneous nature of the copper beryllium (CuBe) workpiece because of the presence of hard particles tends to affect material removal. When machining a CuBe material, it is anticipated that the mechanism of cutting and surface formation may differ from those seen when cutting a homogenous Cu material. Although these mechanisms are popular for the diamond turning of homogeneous materials, they have not been thoroughly studied in relation to CuBe alloys, which contain hard beryllium precipitates. Therefore, the effect of hard particles in the workpiece specimen on the nano-regime diamond turning of CuBe alloy needs to be understood. To explain the influence of Beryllium (Be) particles on the cutting tool and the workpiece surface, a molecular dynamics (MD) simulation was performed. It is revealed that the material removal mechanism in the case of CuBe is phase-dependent. Ductile machining is dominant in the Cu phase, and brittle fracture is dominant in the Be rich phase. It is also observed that the a/r ratio equal to 1 is suitable for cutting in the Cu phase and for ductile regime machining conditions in the Be phase. The a/r ratio higher than 1 causes higher cutting forces, and thus shear plane cutting takes place, which leads to a higher amount of material removal.
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    A review on applications of molecular dynamics in additive manufacturing
    (Sage, 2024-02) Sharma, Anuj; Kumar, Amit
    Additive manufacturing (AM) is an emerging technology that has significant geometric and material capabilities, because of which it is being used in different fields such as aerospace, healthcare, automotive, architecture, and construction. This process takes the digital data for the three-dimensional model to be made and adds materials accordingly in a layer-by-layer manner. Therefore, the understanding of materials at the atomic level may help in getting optimized output in the AM process, and it can have a significant impact on the final products. Molecular dynamics (MD) studies the dynamic behavior of molecules and materials at the atomic and molecular scales. The main objective of this review article is to briefly discuss how MD simulations may be utilized to examine AM processes. This review also covers the potential benefits of using MD to characterize AM processes, the current literature on using MD to simulate AM processes, the primary obstacles and limitations of MD simulations, and the methodologies utilized in AM simulations using MD. Finally, this article concludes with an in-depth discussion and outlines future research potentials.
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    Molecular dynamics modelling of micro/nano manufacturing processes
    (Sage, 2024) Sharma, Anuj; Roy, Tribeni
    Manufacturing processes such as machining, casting, welding, forming including additive manufacturing are essential processes to fabricate various types of components. These manufacturing processes have been developed and are improving with time by optimising process parameters and revealing better insights about the processes. Earlier, research has used various tools like finite element analysis, mathematical modelling, etc., to improve the process understanding and their optimisation. This has brought the significance of computational modelling to support the analysis and optimization of manufacturing processes. In general, any manufacturing process works on two different domains of size scale such as micro scale and macro scale mechanism. Micro scale mechanism is associated with micro/nano manufacturing processes which differs from the macro scale, and conventional tools of modelling do not support it. During the last few decades, there has been an increasing interest in the simulations of micro/nano manufacturing processes. Modelling at nano scale brings out deep insights into the mechanisms and different phenomena. Out of the various modelling approaches, Molecular Dynamics (MD) modelling approach is the most preferred technique to simulate nanoscale manufacturing and investigate the science behind the processes. In general, MD simulation was extensively being used in the field of biology and chemistry towards discovery of novel drugs, chemical, materials, etc. In the last few decades, MD simulation has also been implemented by researchers in the field of manufacturing especially for polishing and thin film technology. Recently there has been a demand to use this tool to discover all possible phenomena at the atomic scale for all types of manufacturing processes. In this special issue of the Journal of Micromanufacturing, recent findings in micro/nano manufacturing through molecular dynamics modelling are aimed. In MD simulation, materials are modelled from atoms by assuming the atoms obey Newton’s second law of motion and will interact using interatomic potential. This concept of modelling brings insight into the manufacturing processes at atomic scale. However, modelling materials at the atomic scale requires reducing the temporal resolution of the order of a few picoseconds. Thus, the computational effort and time become enormous when any process is being modelled at a nanometric scale. Moreover, this approach becomes impossible to model when the space frame is in order of a few microns or more. To overcome this issue, researchers have identified alternate approaches like coarse grain modelling, multi-scale modelling, atom to continuum modelling, etc. All these techniques utilise the MD modelling at the zone of interaction and due to this, the special issue has focussed on MD simulation related novel outcomes for various types of manufacturing processes such as nanofinishing, nanomachining, additive manufacturing, nano-indentation, material’s mechanical characterisation, etc. In addition, this Special Issue will also promote and disseminate the latest works focused on MD modelling and simulation of various micro/nano-manufacturing processes and encourage researchers to adopt this technique to cater the present and future demand of technology. A brief report about the articles accepted under this issue are summarised as follows.
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    Effect of porosity on shock propagation behaviour of single crystal aluminium: A molecular dynamics investigation
    (Elsevier, 2023-02) Sharma, Anuj
    Materials' response to shock waves is largely affected not only by their inherent atomic structure but also by their physical structure. Current study involves analysis of shock propagation behaviour of single crystal aluminium (Al) specimens with different levels of porosities at nanoscale under a compressive shock loading using three dimensional molecular dynamics (MD) simulations. Solid, two dimensional array of pores, and three dimensional array of pores in the single crystal Al specimen were considered for detailed analysis of the shock response. It is observed that the porosity causes time delay in the travel of shock wave from front end of the surface to the rear end. The computational results indicate that the porosity results into increase in time of shock wave travel and it is found that the maximum porosity (47% in this simulation) causes 4 times the time of travel taken in solid Al specimen. The shock wave causes various sequential phenomenon in the Al specimen from compression to rarefaction which further leads to spalling of the material. The study also reveals that the pore walls act as a reflecting wall to the shock wave which causes secondary rarefactions and spalling phenomenon. Analyses show that the deformation in the material during shock loading is largely dominated by Shockley partial dislocations.