Volume 1 Issue 1

Authors: A. Abdiche Abdiche; R. Riane; M. Guemou; R. Khenata; R. Baghdad; Y. Al-Douri

Abstract: First principles total energy calculations were carried out to investigate structural, electronic and optical properties of zinc-blend (ZB) MgO solid solution. Firstly, we have calculated lattice parameters a0(A°), bulk modulus B in GPa and pressure derivative B’(GPa). The direct and indirect band-gap energies were calculated for this material. Total and partial densities of states are depicted in Fig. 2. Secondly, we have examined the pressure effects on the electronic properties. We have varied the pressure from hydrostatic pressure to 350 GPa. Linear coefficients α and β of band gaps are calculated. Finally, the optical properties were investigated under hydrostatic pressure and under a pressure of 300 GPa, where the refractive index n, the optical conductivity in (1/Ω.cm), the real part ε1 and imaginary part ε2 of the dielectric function are presented. Results obtained are discussed and compared with other available theoretical and experimental results.

Keywords: : Wide gap semiconductors, FP-LAPW, MgO, Pressure effect.


Authors: Morshed Khandaker; S. Tarantini Tarantini

Abstract: The interfacial mechanics at the bone-implant interface is a critical issue for implant fixation and the filling of bone defects created by tumors and/or their excision. Our previous study found that micron and nano sizes MgO particles improved the fracture toughness of bone-cement interfaces under tension loading. The strength of bonding of different types of bone with different types of implants may not be the same. The aims of this research were to determine the influences of material mismatch due to bone orientation and a magnesium oxide (MgO) filler material for PMMA bone cement on the mechanical strength between bone and bone cement specimens. This research studied the longitudinal and transverse directions bovine cortical bone as different bone materials and poly Methyl MethAcrylate (PMMA) bone cement with and without MgO additives as different implant materials. The scope of work for this study was: (1) to determine the bending strength and modulus of different bone and bone cement specimens, (2) to determine whether inclusion of MgO particles on PMMA has any influence on these mechanical properties of PMMA, and (3) to determine whether bone orientation and inclusion of MgO particles with PMMA has any influence on the interface strength between bone and PMMA. This study showed that bone orientation has statistically significant effect on the bonding strength between bone and bone cement specimens (P value<0.05). This study also found that while MgO additive decreased the bending strength and modulus of PMMA bone cement, but the inclusion of MgO additives with PMMA bone cement has no statistically significant effect on the bonding strength between bone and bone cement specimens (P value>0.05)

Keywords: Cortical bone, PMMA, MgO, Additives, Mechanical Properties


Authors: M. R. Allazadeh; M. K. Itani; S. N. Wosu

Abstract: The stresses developed in the material by impact load are analyzed experimentally, numerically, and analytically for specimens out of steel, aluminum, wood and woven graphite epoxy composites to investigate the material response to high strain rate stresses for aforementioned materials. The applied strain rates in experiments were set to be within 950 and 3500 s-1. The thin circular shape specimens were examined with high strain rate laboratory tests using the perforation split Hopkinson pressure bar (P-SHPB) with dimensional ratio accepted for One-dimensional stress analysis hypothesis. The article describes analytical solutions for one dimensional in detail to be implemented for numerical analyzing via trapezoid computation. The graphs of the four listed materials with two different thicknesses are compared for the specimen’s energy absorbed, specimen’s strain rate, stress strain rate relationship of the specimen, maximum energy absorbed, and maximum strain in specimen. It turned out that the dependency of deformation on energy absorption follows a power law for the woven composite and is approximated with linear relationships for aluminum and steel. Studying the effect of thickness in energy absorbed shows that doubling the thickness of the specimen reduces the strain of the specimen by 50 percentages for woven graphite epoxy and wood specimens, but the reduction is 25 percentages in the steel and aluminum specimens.

Keywords: Compression Test; High Strain Rate; P-SHPB; Fiber Structure; Damage Mode