الفهرس 
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Abstract
Friction stir spot welding (FSSW), as a solid state joining process, has shown a great potential to be a replacement of single-point joining processes. The application of FSSW in polymers is still in need of more research work. In the present thesis experimental studies have been conducted to explore the feasibility of welding polymers by FSSW. The investigation is applied on the most popular polymers, namely: polyethylene (PE), polyamide (PA), polypropylene (PP) and Polyvinylchloride (PVC), under different operating conditions. Plunging depth and dwell time at two different tool rotational speeds have been considered as varying parameters. The welding force during test procedure and the temperature in the welding material zone during dwell time have been recorded to investigate the effect of the duration of dwell time on the heat generation during welding. The effect of the welding parameters on the strength of welded joints has been determined by lap shear test. Oral and morphological tests were also done to study the fracture behavior of the joint polymers.
Within the range of the present experimental work, the results confirm that FSSW can be applied to PE, PA and PP but is not applicable to PVC. The tool rotational speed, tool plunge depth, plunge rate and dwell time are important in the joint formation and its strength.