EVOLUTION OF THE CARBON NANOTUBE BUNDLE STRUCTURE UNDER BIAXIAL AND SHEAR STRAINS

Close packed carbon nanotube bundles are materials with highly deformable elements, for which unusual deformation mechanisms are expected. Structural evolution of the zigzag carbon nanotube bundle subjected to biaxial lateral compression with the subsequent shear straining is studied under plane strain conditions using the chain model with a reduced number of degrees of freedom. Biaxial compression results in bending of carbon nanotubes walls and formation of the characteristic pattern, when nanotube cross-sections are inclined in the opposite directions alternatively in the parallel close-packed rows. Subsequent shearing up to a certain shear strain leads to an appearance of shear bands and vortex-like displacements. Stress components and potential energy as the functions of shear strain for different values of the biaxial volumetric strain are analyzed in detail. A new mechanism of carbon nanotube bundle shear deformation through cooperative, vortex-like displacements of nanotube cross sections is reported

Bonding of Dissimilar Metals in the Interlayer Region in Al-Based Composites: Molecular Dynamics

The aluminum–matrix composites possess are very important for future applications because they have unique mechanical properties. Here, molecular dynamics is used to analyze the bonding of dissimilar metals on the interface of Al/Mg, Al/Ti, and Al/Cu interfaces during deformation treatment–compression combined with shear at room temperature. The terminal-mechanical treatment used in this simulation is a variant of the experimental technique applied to fabricate Al/Metal composites. It is found that there is a critical value of compressive and shear strain required to obtain the strong mixed Al/Metal interface. The diffusion depth of atoms of both components is dependent on the applied strain: (i) linear relationship for Al/Mg; (ii) logarithmic relationship for Al/Ti and Al/Cu. The mechanical behavior under tension and fracture analysis of the obtained interfaces are discussed in terms of atomic-level structural features which allow an understanding of the interconnection between the mechanical behavior and structure mixture near the interface. One of the important criteria for atomic mixing is the symmetry of the interface. After atomic mixing, Al/Ti composite has the highest ultimate tensile strength, Al/Cu—the average, and Al/Mg—the lowest between the considered interfaces, while the fracture strain of Al/Mg and Al/Ti composites are very close and higher than for Al/Cu. The obtained results are significant for the development of fabrication of Al/Metal interface by high-pressure torsion in practice

Bonding of Dissimilar Metals in the Interlayer Region in Al-Based Composites: Molecular Dynamics

The aluminum–matrix composites possess are very important for future applications because they have unique mechanical properties. Here, molecular dynamics is used to analyze the bonding of dissimilar metals on the interface of Al/Mg, Al/Ti, and Al/Cu interfaces during deformation treatment–compression combined with shear at room temperature. The terminal-mechanical treatment used in this simulation is a variant of the experimental technique applied to fabricate Al/Metal composites. It is found that there is a critical value of compressive and shear strain required to obtain the strong mixed Al/Metal interface. The diffusion depth of atoms of both components is dependent on the applied strain: (i) linear relationship for Al/Mg; (ii) logarithmic relationship for Al/Ti and Al/Cu. The mechanical behavior under tension and fracture analysis of the obtained interfaces are discussed in terms of atomic-level structural features which allow an understanding of the interconnection between the mechanical behavior and structure mixture near the interface. One of the important criteria for atomic mixing is the symmetry of the interface. After atomic mixing, Al/Ti composite has the highest ultimate tensile strength, Al/Cu—the average, and Al/Mg—the lowest between the considered interfaces, while the fracture strain of Al/Mg and Al/Ti composites are very close and higher than for Al/Cu. The obtained results are significant for the development of fabrication of Al/Metal interface by high-pressure torsion in practice

Superplastic Roll Forming of Axial Symmetric Articles from Superalloys

Abstract. A new method of microstructure design in axisymmetric gas turbine engine components made of superalloys is proposed. The method is based on obtaining three types of microstructures by means of superplastic roll forming: coarse-grained one with coherent nano-sized precipitates of the γ′-phase, the second with ultrafine grains of both phases and the third combining coarse deformed matrix grains surrounded by thin layers of fine matrix grains and coarsened precipitates of γ′-phase

Superplastic Roll Forming of Axial Symmetric Articles from Superalloys

Abstract. A new method of microstructure design in axisymmetric gas turbine engine components made of superalloys is proposed. The method is based on obtaining three types of microstructures by means of superplastic roll forming: coarse-grained one with coherent nano-sized precipitates of the γ′-phase, the second with ultrafine grains of both phases and the third combining coarse deformed matrix grains surrounded by thin layers of fine matrix grains and coarsened precipitates of γ′-phase

Crumpled Graphene-Storage Media for Hydrogen and Metal Nanoclusters

Understanding the structural behavior of graphene flake, which is the structural unit of bulk crumpled graphene, is of high importance, especially when it is in contact with the other types of atoms. In the present work, crumpled graphene is considered as storage media for two types of nanoclusters—nickel and hydrogen. Crumpled graphene consists of crumpled graphene flakes bonded by weak van der Waals forces and can be considered an excellent container for different atoms. Molecular dynamics simulation is used to study the behavior of the graphene flake filled with the nickel nanocluster or hydrogen molecules. The simulation results reveal that graphene flake can be considered a perfect container for metal nanocluster since graphene can easily cover it. Hydrogen molecules can be stored on graphene flake at 77 K, however, the amount of hydrogen is low. Thus, additional treatment is required to increase the amount of stored hydrogen. Remarkably, the size dependence of the structural behavior of the graphene flake filled with both nickel and hydrogen atoms is found. The size of the filling cluster should be chosen in comparison with the specific surface area of graphene flake