الفهرس 
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Abstract
In the present investigation, the effect of friction stir spot welding (FSSW) parameters, typically, the tool rotation speed and dwell time on the microstructural and mechanical characteristics of friction stir spot welds of aluminum alloy AA1050-O was investigated. Also the effect of (FSSW) process parameters on the corrosion behavior of aluminum alloy AA1050 lap joints after immersion in 3.5 wt-% NaCl aqueous solution for 7 days was investigated.The present work is a study ofthe effect of FSSW parameter of (free length of specimen and the width of the Complete Metallurgical Bonded Region ”CMBR” width, on the dynamic behavior of AA1050 using three different methods to validate the presented data. These methods are mathematical modelling, Finite Element Analysis ”FEA”, and experimental work.
The results revealed that the width of the completely metallurgical-bonded region (CMBR) increases with increasing tool rotational speed and/or dwell time up to certain levels. Increasing the tool rotational speed and/or dwell time above these levels reduces the width of CMBR. Increasing the CMBR width increases the tensile-shear strength of the friction stir joint. The maximum tensile-shear force found in the present study was exhibited by the weld that has the maximum CMBR width. The peak temperature measured during FSSW increases with increasing tool rotational speed and/or dwell time. The maximum peak temperature observed was about 562 oC at a rotational speed1600 rpm and dwell time of 14 s.
The Tafel polarization curve revealed also that, the FSSW increase the corrosion resistance of (AA1050), the pitting corrosion start at lower potential in the stir zone but form passive film protect welding region from corrosion. The corrosion rate of base metal is higher than the welding specimen
The result revealed also the dynamic behavior of FSSW of aluminum alloy 1050 has greatly affected by length of free length of specimen, Combination Ratio (CR) and weak effect of complete metallurgical bonded region (CMBR).As the free length increases, the theoretical natural frequency decreases, but increase with increasing the CMBR and the variation of combination ratio (CR) has a great effect on the natural frequency, as (CR) increases the natural frequency decreases. The effect of CMBR on natural frequency when the free length (Lf) and combination ratio (CR) approximately straight line and CMBR has a weak effect on theoretical frequency of a cantilever beam.The error between theoretical and FEA is 8%, between theoretical and experimental is 6% , and between experimental and FEA model is 1.9%.