Effect of FSW Parameters on The Microstructure and Mechanical Properties of T-joints between Dissimilar Al-Alloys

The main purpose of this research is to develop T-joints between the aluminum AA 2024-T4 and AA 7075-T6 using friction stir welding.  The effect of tool geometries, tool traveling speed, and rotational rate in the welded T-joints were investigated and discussed. Three different tools were used with different shoulder to pin ratios 3.28, 3.36, and 4.31. After optimization, the best tool dimension has used with the different rotational and welding speeds. Three tool traverse speeds of 50, 75, and 100 mm/min were used. Two rotation rates of 800 rpm and 1000 rpm were applied. After FSW, at a number of the above FSW parameters' combinations, macrostructure and microstructure analyses were done using optical microscopy. In order to have an insight into the mechanical properties, hardness measurements and tensile testing were carried out. Using small shoulder to pin ratio produced visually unacceptable T-joint. Opposite happened by using the tool with 4.31 of shoulder to pin ratio. Furthermore, the results showed sound T-welds with no obvious defects at high rotational rate of 1000 rpm with the two used traveling speeds. Asymmetric temperature distribution was observed between the two sides, advance side (AS) and retreating side (RS

A Hybrid Analytical-Numerical Model of Heat Generation and Distribution in Friction Stir Welded AA2024 Butt Joints

Being a solid-state process, friction stir welding (FSW) is considered a candidate technique for welding critically-microstructure-sensitive materials such as heat-treatable aluminum alloys. A hybrid computational model that employs both analytical and numerical approaches was used to estimate the amount of heat generated in the FSW of AA2024-T4 butt-welded sheets and how it is distributed as a function of time using a 3D transient heat transfer finite element analysis (FEA). Experimental procedures were used to validate the heat distribution in the welded butt joints using candidate rotational and travel speeds from the numerical model. The model outcomes show that rotational speed less than 600 rpm gives insufficient heat input when the optimum travel speed is 25 mm/min while higher rpm would cause overheating and flash formation. Structural and mechanical joint characterizations were performed to ensure the validity of the optimized process parameters. The model recommended parameters give the defect-free butt joints with the best efficiency in terms of ultimate strength. The Vickers hardness profile (W-shaped) for the welds’ cross-sections shows that 600 rpm gives the highest values in all different weld zones compared to that welded at 400 and 800 rpm

Formulation and evaluation of orally disintegrating clopidogrel tablets

ABSTRACT Recent advances in drug delivery systems have aimed to achieve better patient compliance. One of these advances is the formulation of orally disintegrating tablets (ODTs) that dissolve instantaneously, releasing drugs within a few seconds without the need of water. The main objective of this paper was to prepare and develop ODTs of clopidogrel. The ODTs were prepared by direct compression. The effect of three superdisintegrants, namely crospovidone, croscarmellose sodium, and sodium starch glycolate, using three different disintegration times on the dissolution rate was investigated. The prepared tablets were evaluated for hardness, friability, disintegration time and in vitro drug release. Furthermore, the interaction of clopidogrel with the formulation excipients was studied using differential scanning calorimetry (DSC). DSC studies revealed that there were no interactions between the drug and the excipients used. All tablets had hardness values in the range 4.0-5.2 kp and friability lower than 1%. The weight and drug content uniformity of all formulations was within official limits according to BP. In vitro drug release studies of the ODTs showed that more than 90% of the drug was released within ten minutes. A palatability test in human volunteers showed acceptable taste and mouth feel. Thus, the obtained results conclusively demonstrated successful rapid disintegration of the formulated tablets and acceptable palatability