In the present investigation the mechanical behaviour of AA7075T651 and AA6061T6 aluminium alloys plates joined by friction stir welding (FSW) were evaluated. The effects of weld process parameter like tool rotation speed 650-1000 rpm and weld speed 30-40mm/min with square trapezoidal pin profile on mechanical properties were investigated. The welded joints were tested by means of by X-ray radiography, tensile, hardness and optical microscopy testing. The radiography revealed the presence of internal in FS welds and observed that increasing transverse speed increases the occurrence of weld defects. The hardness was found to be mixed effect with respect to tool rotations and transverse speed for similar FSW joints. But in dissimilar FSW joints, hardness decreases with increasing tool speed and weld speed and it was strongly affected by precipitate distribution. Difference in grain size and distribution was observed for different ranges of rotation and weld speed. پرونده مقاله

Abstract: A continuously variable transmission (CVT) is a transmission which may change step less by way of an infinite variety of effective gear ratios between maximum and minimum values. This contrasts with different mechanical transmissions that solely permit just a few different distinct gear ratios to be selected. Continuously variable transmissions (CVTs) are mechanical devices that allow a continuous variation of the output velocity by adjusting its geometrical configuration. This offers several advantages over traditional transmissions such as better fuel efficiency, quieter operation, and a lower mass. Current efforts to reduce the vehicles, fuel consumption in order to protect the environment and save fuel have seen a recent resurgence in CVT research, especially in the automotive industry. The torque of the continuously variable transmission system with friction drive mechanism is transmitted by contacting roller with input and output disks. For the higher transmitted torque, it is necessary to apply large load in order to get higher friction force, which in turn generates severe high stress on the contact surfaces of roller and disks. The toroidal type CVT system has simple component arrays that have three contact points between roller and each input or output disk to get the torque transmitted This work documents a successfully developed experimental model of a toroidal continuously variable transmission (CVT) by adjusting its geometrical configuration of CVT design and compared the experimental results of speed, torque and power delivered at the output disc with those obtained by a theoretical. پرونده مقاله

Abstract: Friction stir welding, a solid state innovative joining technique, is widely being used for joining aluminium alloys for aerospace, marine automotive and many other applications of commercial importance. FSW trials were carried out using a vertical machining centre (VMC) on AA6061 alloy. The main objective of the present work was to evaluate the weld processing parameter of friction stir weld (FSW) process for AA6061-T6 alloy and to determine the properties of the obtained joints with respect of welding speed. Experiments have been conducted by varying the welding speed of 55-70 mm/min and the rotating speed was fixed at 1700rpm. Tensile properties, microstructure, microhardness, fractography, and corrosion resistance of FSW joints were investigated in this study. The result showed that  there was a variation of grain size  in each weld zone which depends upon the material and process parameters of FSW in the joint itself. The coarsest grain size was observed in heat affected zone (HAZ), followed by the thermomechanically affected zone(TMAZ) and the nugget zone(NZ). The maximum tensile strength of 184MPa and highest joint efficiency of 49.32% was obtained on the joint fabricated at 55mm/min of welding speed. پرونده مقاله