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Experimental studies on ultrasonically assisted friction stir spot welding of AA6061

Rostamiyan Y., Seidanloo A., Sohrabpoor H., Teimouri R.

Archives of Civil and Mechanical Engineering

2015

Vol. 15, no. 2

335--346

The present study introduces a new combination of two separate welding processes, i.e. friction stir spot welding (FSSW) and ultrasonic welding (USW). Here, in order to improve the weld quality, the friction stir spot welding is assisted by ultrasonic vibration of tool. To systematically analyze effect of process factors such as US vibration, tool rotary speed, tool plunge depth and dwell time on lap shear force and hardness, a L18 orthogonal array from Taguchi design of experiments is developed. Effects of process factors on responses were studied along with their percentage of contribution which was determined through analysis of variances. Results indicated that US vibration is a significant factor having positive influence on lap shear force and hardness. Next to the vibration, tool rotary speed, dwell time and plunge depth are also the important factors which affects mechanical properties significantly. Optimization of process factors by grey relational analysis showed that applying US vibration and selections of 1200 RPM tool rotary speed, 6 mm plunge depth and 6 s dwell time causes the highest value of grey relational grade and guarantee maximum lap shear force as well as maximum hardness.

Application of generalized differential quadrature method to nonlinear bending analysis of a single SWCNT over a bundle of nanotubes

Fereidoon A., Babaee A. M., Rostamiyan Y.

Archives of Mechanics

2012

Vol. 64, nr 4

347-366

The deformation of an individual single walled carbon nanotube (SWCNT) over a bundle of nanotubes has been studied using the generalized differential quadrature (GDQ) method. The effects of length, diameter, and minimum value of Lennard–Jones experimental potential have been considered in the governing equation which is derived based on the GDQ and the issues related to the implementation of the boundary and compatibility conditions were addressed. The explanation of reliability and flexibility of the GDQ is done by solving several selected examples which are evaluated by comparing them with existing exact or approximate solutions which were previously generated by finite element approach.