Sharif Digital Repository

In this study, microstructural changes and mechanical properties during friction stir welding of AA7075-T6 have been investigated. Friction stir welding at relatively high rotational speeds ranging from 1000 to 1400 rpm and longitudinal speeds in the range of 40 to 80 mm/min have been performed and then microstructures and mechanical properties of the weldments have been studied. The results show that the rotational and longitudinal speeds have a significant effect on the microstructures as well as the mechanical behavior of the welded material while a fine grain structure is produced at higher ratio of rotational speed to longitudinal speed. On the other hand, for a given longitudinal... 

Welded sheets with different thicknesses are one of the interesting types of tailor-welded blanks (TWBs) that are widely used in metal-forming industries. In the present work, the formability behavior of different 1100-aluminum TWBs was studied. In this regard, the TWBs were made with different thickness ratios by using friction stir welding (FSW) at different welding rotational speeds (ω). The thickness ratios of 1.0, 1.3, and 1.7 were investigated where the thinner sheets had 1.5 mm thick for all conditions; i.e., the volume of welded material increased when the thickness ratio increased. Macrostructural observations, mechanical investigations, and sheet-forming limit tests were... 

The effect of the layer in contact with tool (Al or Cu) and the depth of plunge on friction stir butt welding of Al-Cu bilayer laminated composites produced by cold roll welding were studied. The measurement of weld cross sections and variations of the axial load and torque during welding process showed that material flow is influenced by the material which is in contact with the shoulder. Being Al layer in contact with the shoulder led to higher force and torque during welding, and a defect-free weld could be obtained in this manner. By welding from Cu side, a higher plunge depth was needed to develop enough force and torque and thereby a defect-free weld. The amount of material swept by... 

In this article, a strain energy density function of the Saint Venant-Kirchhoff type is expressed in terms of a Lagrangian deformation measure. Applying the governing postulates to the form of the strain energy density, the mathematical expression of this measure is determined. It is observed that this measure, which is consistent with the strain energy postulates, is a strain type with the characteristic function more rational than that of the Seth-Hill strain measures for hyperelastic materials modelling. In addition, the material parameters are calculated using a novel procedure that is based on the correlation between the values of the strain energy density (rather than the stresses)...