الفهرس 
chapter 1Only 14 pages are availabe for public view
 |  | from | 113 |  |  |
| | | from | 113 | | |
Abstract
Recently, modem industries particular aerospace, automotive and
shipbuilding have addressed a large attention to a new welding
technology based on a solid state welding process, called friction stir
welding (FSW). This advanced welding technology proved magic
solution in welding unweldable and dissimilar materials.
The present investigation aims to study the aluminum weldment quality
using the friction stir welding technique with a double shoulder tool
instead of the common single shoulder one. Attempts have been made to
understand effects of process parameters include tool geometry, rotation
speed, and welding speed on aluminum weldment.
In this direction, a single shoulder tools with five different pin profiles
(straight cylindrical, right threaded cylindrical, left threaded cylindrical,
tapered cylindrical, and right threaded tapered cylindrical) and a double
shoulder tools with three different pin diameters investigated. The
operation parameters included three rotation speeds and three welding
speeds were also investigated for double shoulder tool and compared
with single shoulder one.
Also an attempt has been done to correlate welding tool geometry and the
operation parameters in the friction stir welded joint with temperature
distribution across welded joints.
Evaluations of friction stir welded joints were carried out by tensile,
impact, and Vickers micro-hardness tests. The tensile behavior expressed
as strength and elongation% were investigated and impact energy at
room temperature and at range of temperature from ( -70°C to l50°C)
were examined. Vickers micro-hardness tests were performed and
assessed at single shoulder tool with different tool pin profiles. All results
were compared and evaluated with the aluminum base metal
It is found that the shape of the tool pin profile is affecting on the amount
of heat which generated during friction stir welding and on the
mechanical properties of the weldments.
The welded joint strength reached about 90, 80 and 76% of base metal at
controlling rotation speed, welding speed, tool pin diameter respectively.
In addition, elevated temperature impact energy increased with
decreasing temperature. Sharp DROP in impact energy recorded at
temperature below sub-zero, this was true for all process parameters.
On the other hand, Friction stir welding introduced softening in the stir
zone and thermo-mechanical affected zone.