this study aims to numerically investigate on the crashworthiness of thin-walled square tubes by consideration of 3-d oblique loading. in this type of loading, direction of loading is defined by using two spatial angles relative to the position of the tube. to this aim, finite element (fe) analysis is employed to simulate the loading for 8 different numerical models with different loading orien...

-The characteristics of a number of metal components proposed as impact energy absorbers are reviewed, attention being focussed on to modes of deformation which stem from the axial compression of metal tubes. Progressive buckling, inversion and splitting are discussed and areas for future work identified. The buckling of thin-walled square section tubes filled with polyurethane foam is also des...

Amodel for torsional vibration of slender thin-walled tubes with constrained-layer dampers is developed. Assuming that the deformation obeys the Saint-Venant hypotheses, we develop a model suitable for prediction of the complex stiffness per unit length in closed, thin-walled tubes whose walls consist of laminated elastic and viscoelastic layers, and formulate a boundary-value problem for the w...

Single-walled carbon nanotubes (SWCNTs) offer a range of potential applications based on their unique one-dimensional structures. Theoretical calculations shows that their electronic structures depend strongly on their chiral vector indices (n,m) which determine the diameter and chiral angle. The graphite wrapping condition n-m=3p+q generates metallic tubes for q=0, while semiconducting tubes a...

We show that the photoluminescence intensity of single-walled carbon nanotubes is much stronger in tubes with large chiral angles--armchair tubes--because exciton resonances make the luminescence of zigzag tubes intrinsically weak. This exciton-exciton resonance depends on the electronic structure of the tubes and is found more often in nanotubes of the +1 family. Armchair tubes do not necessar...

The vibrational properties of single-walled carbon nanotubes reflect the electron and phonon confinement as well as the cylindrical geometry of the tubes. Raman scattering is one of the prime techniques for studying the fundamental properties of carbon tubes and nanotube characterization. The most important phonon for sample characterization is the radial-breathing mode, an in-phase radial move...

Material properties and geometry are two important design parameters which their effects should be considered in a crashworthiness analysis. In this paper, the axial impact of metallic and hybrid energy absorbing thin-walled tubes with poly-gonal cross-section is simulated using LS-DYNA software. The combined effects of changing the geometry and material properties on the mass specific energ...

The structure of single walled armchair and zig-zag carbon nanotubes having 70 atoms and two carbons replaced by boron or nitrogen is obtained at minium energy using HF/6-31G* molecular orbital theory. The calculations show that the ground state of the zig-zag tubes is a triplet state while for the armchair tubes it is a singlet. In the zig-zag tubes the density of states at the Fermi level is ...