•Investigation on potential impacts in power sector due to COVID-19 pandemic.•An analysis on Indian power system scenario during pandemic is presented.•Measures to combat unforeseen reduction and ...shifting of electricity demand.•Recommendations are provided for risk management in power and energy sector.
The demand of electricity has been reduced significantly due to the recent COVID-19 pandemic. Governments around the world were compelled to reduce the business activity in response to minimize the threat of coronavirus. This on-going situation due to COVID-19 has changed the lifestyle globally as people are mostly staying home and working from home if possible. Hence, there is a significant increase in residential load demand while there is a substantial decrease in commercial and industrial loads. This devastating situation creates new challenges in the technical and financial activities of the power sector and hence most of the utilities around the world initiated a disaster management plan to tackle this ongoing challenges/threats. Therefore, this study aims to investigate the global scenarios of power systems during COVID-19 along with the socio-economic and technical issues faced by the utilities. Then, this study further scrutinized the Indian power system as a case study and explored scenarios, issues and challenges currently being faced to manage the consumer load demand, including the actions taken by the utilities/power sector for the smooth operation of the power system. Finally, a set of recommendations are presented to support the government/policymakers/utilities around the world not only to overcome the current crisis but also to overcome future unforeseeable pandemic alike scenario.
The effect of mechanical processing and thereby induced residual stress on the shock response of the crystalline-amorphous nanolaminate is unexplored till date. Here, we have implemented molecular ...dynamics (MD) simulation to study the structural evolution of the cold-rolled crystalline Cu-metallic glass Cu63Zr37 nanolaminates during shock loading. Atomic stress analysis has revealed that specimen rolled from the metallic glass (MG) side accumulates compressive residual stress, whereas the specimen rolled from the crystalline side amasses tensile residual stress. The influence of the residual stress can be directly seen during the shock propagation through the pressure profiles, which shows reduced pressure for the specimen with tensile residual stress compared to the un-rolled specimen. Also, presence of stress fields due to partial dislocations reduces the intensity of the compressive stress in the nanolaminates. It is found that generation of rarefaction wave at higher piston velocity causes formation of tensile residual stress at crystalline/amorphous interface.
•Nature of residual stress in specimen depends on the region that is rolled first.•MG side rolled specimen shows a comparatively higher pressure in the specimen.•Tensile residual stress reduces the pressure for high and low intensity shockwaves.•Stress field due to dislocations reduce shock intensity and generate lower stress.
In this present study, effect of Nb content on glass forming ability and plasticity of Ni-Nb metallic glass has been investigated using molecular dynamics simulation with embedded atom method (EAM). ...Ni-Nb metallic glass specimens having different atomic percentages of Nb content (i.e. ~15, 20, 25, 30, 38, 40.5, 45 and 50at.%) are prepared by fast cooling process (cooling rate~1012Ks−1) from their liquid phase. It is observed that increase in Nb content up till 38at.% causes improvement of glass forming ability of Ni-Nb binary system. On further increment of Nb content, glass forming ability is found to be slightly reduced or remain almost same. Voronoi cluster analysis has been performed to evaluate the variation in short range ordering with increasing Nb content in Ni-Nb glass. Simulated tensile tests are also performed, and it reveals that higher Nb content actually helps in augmentation of the plastic behavior of the Ni-Nb metallic glass.
•Increasing Nb content increases the glass forming ability of Ni-Nb metallic glass.•Population of icosahedral-like clusters increases with increase in Nb content.•Plasticity of the Ni-Nb metallic glass is enhanced by increasing Nb content.
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•AIF thickness of 1 nm and 2 nm retards crack growth under tensile load.•AIF impedes possibility of multiple crack formation.•For cyclic loads, crack propagation is also retarded by ...presence of AIF.
In the present study, molecular dynamics simulation was used to investigate the influence of amorphous intergranular films (AIF) and its thickness on possible crack retardation in nanocrystalline Cu under tensile and cyclic loading conditions. Structural analyses were carried out based on different methods such as centro-symmetry parameter, common neighbor analysis, and atomic strain. Results showed that specimens with AIF thickness as small as 0.5 nm can restrict the propagation of both perpendicular and parallel cracks during uniaxial tensile deformation. By increasing the AIF thickness, the crack propagation was found to be further retarded due to crack tip blunting. Atomic strain analysis also revealed that thicker AIF localized the strain distribution more strongly thus inhibiting the nucleation of multiple intergranular cracks and subsequent rapid fracture. In case of cyclic loading, the strain was accumulated through the formation of twins/stacking faults when the AIF thickness was 0.5 and 1 nm, which can interact with the AIF and eventually cause the nucleation of voids/cracks. However, increasing the AIF thickness to 2 nm can restrict such mechanism as the strain was mostly accommodated by the amorphous phase.
Rolling processes are extensively used to induce network of shear bands (SBs) in the bulk metallic glasses, which in turn enhances the overall plasticity of the specimen. However, the atomic-level ...understanding of shear band formation/propagation mechanism during mechanical processing is still limited. In this perspective, we have developed a molecular dynamics (MD) simulation model to recreate the rolling deformation process and investigate the SB formation in Cu-Zr metallic glass (MG) specimen. Results have shown that dense and concentrated primary SBs along with secondary branching are formed during cryo-rolling, whereas a scattered and thicker SBs are formed during hot rolling process. Meanwhile, Voronoi cluster analysis revealed that the high five-fold symmetry clusters tend to decrease, while the crystalline-like cluster increases during the hot rolling process. These findings from the study are in good agreement with previous experimental studies substantiated in literature, which shows that the model correctly predicts the shear-banding phenomenon.
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•Residual stress is found at grain boundary and triple junction at cryo-rolling.•Grain interior shows dispersed stress due to thermal vibration at high temperature.•Nano-rolling ...generates new grain orientation, finer grain, and sub-grain boundaries.•(200) and (111) peaks are the preferred orientation during the rolling process.
Although the rolling process is significant on developing the preferred crystallographic orientation in the metallic sheets, its implementation at the nanoscale is uncertain. However, it is believed that the nano-rolling process can be realized with progressive scientific and technological advancement in material processing. Presently, we have modeled the rolling process of nanocrystalline Ni specimen using molecular dynamics simulations and investigated the underlying deformation mechanism along with the orientation evolution. Moreover, we have also analyzed the effect of temperature on the residual stress generation and the grain rotations. This atomistic model takes both shear and compressive forces into consideration, which makes it efficient in representing the actual deformation process. It is found that the compressive stress accumulation majorly occurs at grain boundary whereas tensile stresses are accumulated at triple junctions. At elevated temperatures, the stresses during the deformation are diminished and gets dispersed due to the thermal vibrations caused by the high temperature deformation. Through this study, we have evidently shown the orientation change, grain refinement, and formation of sub-grain boundaries during the rolling process. In addition, we have also characterized the specimens with virtual diffraction analysis, which has shown the preferred orientations to be (002) and (111) after rolling through the first and second set of rollers respectively.
Grain boundary (GB) migration and grain growth in nanocrystalline metals are major obstructions to exploit these materials to their fullest potential, thus limiting their utility as advanced ...structural materials. Here, we investigate the effect of Zr segregation to a Ni GB on migration and subsequent strengthening during shear deformation and high-temperature bending creep. Specifically, using molecular dynamics simulation, we simulate deformation of a Ni bicrystal specimen having a symmetric ∑5 grain boundary with and without segregated Zr. It is found that GB segregation up to 0.4 at.% pins the CSL boundary resulting in increased shear strength. Similar behavior is also observed in the case of bending creep deformation where the creep resistance increases only up to 0.4 at.%. This study indicates that larger amounts of GB segregation cause destabilization of the local atomic structure and consequently affect the GB stiffness. Moreover, we investigate the effect of Zr segregation on the interaction between the GB and a dislocation. We find that the preexisting dislocation is absorbed in the GB region for both clean and segregated specimens; however, the absorption path of the dislocation is different due to the change in GB stiffness caused by the Zr segregation.
Basal texture weakening and twinning are two important mechanisms causing enhancement in the formability of nanocrystalline magnesium. However, the atomistic perspective of these mechanisms along ...with structural evolution during the rolling process is unexplored. Here, we have implemented molecular dynamics simulations and modeled the cold-rolling process to study the dynamic twin nucleation through atomic shuffling and texture weakening mechanisms under the influence of compressive loads. Results show that twinning propagates along the grains under shear stress through twin boundary disconnection steps, whereas successive thickness reduction through multiple passes causes an overall texture weakening due to the RD splitting of basal orientation. Along with this, grain refinement is also found to contribute towards texture weakening. The findings of this work comply well with the experimental results and we hope that it can aid in demystifying the enigma related to structural evolution in nanostructured HCP metals during the rolling process.
Molecular dynamics simulation based study of amorphous to crystalline transformation under compressive loading at different temperatures (10 K, 100 K and 300 K) has been performed using embedded atom ...method potential for nano-size Ni specimen. Intermediate BCC and HCP phases are found to be formed during the transformation from amorphous to FCC structure. The extent of transformation to FCC structure in the final specimen is found to be comparatively more during deformation process at 100 K temperature when compared to 10 K and 300 K temperatures for applied compressive load.
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•BCC and HCP are intermediate phases during amorphous to FCC transformation.•RDF plot shows splitting of first peak during the BCC martensitic transformation.•Deformation at 100 K forms higher fraction of FCC phase when compared with 10 K and 300 K.
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