Department of Mechanical engineering

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Author: search.filters.author.Mishra, Radha RamanSubject: search.filters.subject.Molecular dynamics simulations

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    Unravelling the atomistic-scale insights into tensile response of equiatomic cupronickel alloy with pre-existing faceted grain boundary interface
    (Elsevier, 2024-02) Mishra, Radha Raman
    The aim of this research work is to investigate the effect of strain rates and temperatures on the mechanical properties of an equiatomic copper-nickel (Cu–Ni) alloy with a pre-existing faceted Σ3 [111] 60° {11 8 5} grain boundary. Molecular dynamics simulations conducted in this scrutiny focuses on understanding the tensile behaviour of bicrystalline equiatomic Cu–Ni alloys (denoted by Cu50Ni50) under various thermodynamic conditions. The uniaxial tensile deformation simulation was carried out at various strain rates (108, 109 and 1010 1/s) in conjunction with different conditions of cryogenic temperature (100 K), room temperature (300 K) and high temperature (500 K). The authors found that the yield stress and Young's modulus of the bicrystalline Cu50Ni50 alloy were highest at the cryogenic temperature, and decreased as the temperature increased. To add on, the yield stress of the bicrystalline Cu50Ni50 alloy increased with an increase in the strain rate value. From the microstructural and dislocation analysis point of view, it was observed that the formation of dislocations was lowest at the cryogenic temperature. Interestingly, at the yield point, the coherent twin boundary tip act as the nucleation site for the dislocations for cryogenic temperature condition. These findings shed light on the relationship between the temperatures, strain rates, and the mechanical properties of Cu–Ni alloys, which will aid in reporting the optimized conditions for their desired engineering applications. It is also proposed that tailoring of the tensile properties is achievable by exposing Cu–Ni alloys to various environmental conditions (cryogenic, ambient, and elevated temperatures with different applied strain rates).
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    Exploring microwave heating characteristics of polycrystalline 3c-sic using molecular dynamics study
    (MDPI, 2024-09) Mishra, Radha Raman
    Polycrystalline silicon carbide (SiC) has been significantly used as a susceptor material during microwave-based material processing owing to its excellent microwave absorption properties. However, the interaction of microwaves with polycrystalline SiC at an atomic level has not been explored experimentally or theoretically. This work investigates the microwave heating characteristics of polycrystalline cubic 3C-SiC through molecular dynamics (MD) simulation using the Vashishta interatomic potential. The effect of change in electric field strength and frequency on the structural evolution and thermo-physical properties of polycrystalline 3C-SiC has been studied. The study revealed that the presence of grain boundaries in polycrystalline 3C-SiC structures plays a critical role in enhancing microwave absorption efficiency. Microwave exposure to polycrystalline 3C-SiC beyond 2830 K significantly increases total energy; consequently, a solid-to-liquid transition occurs in the 3C-SiC structure, initiated from the grain boundaries. Further, an increase in microwave exposure time results in a reduction in grain size due to rapid microwave absorption at grain boundaries. The phase transition temperature of polycrystalline 3C-SiC was observed to be 14% lower than that of the single-crystal 3C-SiC.