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In many cases, it is advantageous to discretize a domain using several finite element meshes instead of a single mesh. For example, in fluid-structure interaction problems, an Eulerian mesh is advantageous for the fluid domain while a Lagrangian mesh is most suited for the structure. However, the interface conditions between different types of meshes often lead to significant errors. A method of treating different meshes by smoothly varying the description from Lagrangian to Eulerian in an interface or blending domain is presented. A Lagrangian mesh is used for the structure while two different types of mesh are used for the fluid. Arbitrary Lagrangian-Eulerian (ALE) meshes are used in the regions of the fluid-structure interfaces while Eulerian meshes are used for the remainder of the fluid domain. A blending function is used to couple the ALE and Eulerian meshes to ensure a smooth transition from one mesh to another. The method is tested on two fluid-structure problems — flow past a hinged plate, and fluid expansion in a closed container. Results are in good agreement with standard finite element and analytical solutions.

Molecular dynamics simulations are performed on multiwalled carbon nanotubes (MWCNTs) under axial compression to investigate the effects of the number of walls and their van der Waals (vdW) interaction on the buckling behaviors and mechanical properties (Young's modulus and Poisson's ratio). The Brenner second-generation reactive empirical bond order and Lennard-Jones 12-6 potential have been adopted to describe the short-range bonding and long-range vdW atomic interaction within the carbon nanotubes, respectively. In the presence of vdW interaction, the buckling strain and Young's modulus of MWCNTs increase as the number of tubes is increased while keeping the outermost tube diameter constant, whereas Poisson's ratio was observed to decrease. On the other hand, when the MWCNTs are formed by progressively adding outer tubes while keeping the innermost tube diameter constant, Young's modulus and buckling strain were observed to decrease, whereas Poisson's ratio increases. The buckling load increases with increasing the number of walls due to the larger cross-sectional areas. Individual tubes of MWCNTs with a relatively large difference between the diameters of the inner and outer tubes buckle one at a time as opposed to simultaneously for MWCNTs with a relatively small difference in diameters.

The elastic constants of polycrystalline Cu6Sn5—an intermetallic in lead-free alternatives of several material systems—are presented. The results are obtained by applying: (i) Reported crystallographic structure of monoclinic single crystal Cu6Sn5, (ii) structure optimization and determination of single crystal elastic constants from first principle calculations, and (iii) limit analysis of polycrystal stiffness based on single crystal properties. The agreement between the calculated Young’s modulus (120 GPa) and those from nanoindentation experiments (112–125 GPa), and the tight bounds on the predicted polycrystal values give a measure of confidence in other calculated properties for which experimental data are unavailable.