Predicting the tensile strength, impact toughness, and hardness of friction stir-welded AA6061-T6 using response surface methodology

In this research, an attempt has been made to develop mathematical models for predicting mechanical properties including ultimate tensile strength, impact toughness, and hardness of the friction stir-welded AA6061-T6 joints at 95 % confidence level. Response surface methodology with central composite design having four parameters and five levels has been used. The four parameters considered were tool pin profile, rotational speed, welding speed, and tool tilt angle. Three confirmation tests were performed to validate the empirical relations. In addition, the influence of the process parameters on ultimate tensile strength, impact toughness, and hardness were investigated. The results indicated that tool pin profile is the most significant parameter in terms of mechanical properties; tool with simple cylindrical pin profile produced weld with high ultimate tensile strength, impact toughness, and hardness. In addition to tool pin profile, rotational speed was more significant compared to welding speed for ultimate tensile strength and impact toughness, whereas welding speed showed dominancy over rotational speed in case of hardness. Optimum conditions of process parameters have been found at which tensile strength of 92 %, impact toughness of 87 %, and hardness of 95 % was achieved in comparison to the base metal. This research will contribute to expand the scientific foundation of friction stir welding of aluminum alloys with emphasis on AA6061-T6. The results will aid the practitioners to develop a clear understanding of the influence of process parameters on mechanical properties and will allow the selection of best combinations of parameters to achieve desired mechanical properties

Homotopy Perturbation Method For Fractional Shallow Water Equations

In this paper, the homotopy perturbation method is adopted to find explicit and numerical solutions for systems of non-linear fractional shallow water equations. The fractional derivatives are described in the Caputo sense. We apply both the homotopy perturbation method and the homotopy analysis method, to solve  certain shallow water equations with time-fractional derivatives, and explicitly construct convergent power series solutions. The  results obtained reveal that these  methods are  both very effective and simple for finding approximate solutions. Some numerical examples and plots are presented to illustrate the efficiency and reliability of these methods

Defects and doping in oxides: case of doped TiO2 films

Oxide-based films and nanostructures have emerged as important and promising materials for a wide range of applications such as photovoltaics, photocatalysis, optoelectronics, gas sensing and electronics. To develop an appropriate understanding of the properties of these oxides, it is necessary to address the material preparation methods as well as structural and defect issues. The present work deals with oxide films synthesis processes using radio-frequency sputtering technique, the film stoichiometry control and structural defect identifying, to produce transparent and conductive films. Nb-doped titanium oxide (TiO2:Nb) thin films are considered. A comparative study of the electrical and optical properties of the Nb:TiO2 thin films in relation with the film chemical properties, structural defects and crystalline phase, the target material and the sputtering gas was made. The lowest resistivity was achieved in the range 2×10-3 -7.42×10-4 Ω.cm, which makes the used deposition method a suitable technique for the development of transparent electrodes, transferable also to large areas