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Formability Study of Tailored Blanks with Different Thickness Ratios Welded by Friction Stir Welding

Kolahgar, Sina | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41823 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kokabi, Amir Hossin; Akbarzadeh, Abbas
  7. Abstract:
  8. These days the usage of welded tailor blanks with sufficient stability and flexibility is accelerating rapidly in order to production of slighter parts and reduction of fuel consumption in transportation means. Therefore, the conjuncture of blanks by welding methods is highly considerable before forming and ultimate production. Friction Stir Welding is greatly appealing to industry as one of the newest methods of solid state welding in production of TWB blanks. In this research, the feasibility study of Friction Stir Welding of thin Al 1100 – H18 alloy blanks with 1.5, 2 and 2.5mm thickness has been evaluated first. After creation of sound welds with same thicknesses, Friction Stir Welding of blanks with different thickness ratios to each other has been investigated. The surveys showed that the production of Tailored Welded Blanks with different thickness ratios from thin blanks by FSW method is possible by operating appropriate compensation angle. According to this, the effect of Friction Stir Welding parameters on Tailored Welded Blanks properties with thickness ratios of 1, 1.3 and 1.7 has been studied. Afterwards, micro structural evaluations, mechanical tests and forming limit test have been done in order to optimize welding parameters and produce TWBs with optimum formability. Macro graphical studies have shown an increased volume of stirred area in each thickness ratio by increasing the rotational speed of the tool. Furthermore, these results showed that by increasing the thickness ratio in TWBs, thermal efficiency of the FSW joint will be decreased up to 60% of thermal efficiency of the FSW joints with same thicknesses. the mechanical properties studies of TWBs show that in constant transitive movement speed, by growth of rotational speed, the flexibility will grow up to 1.85 times comparing with base metal, and by correct input temperature selection in welding procedure it will be possible to achieve 87 percent of cold worked base metal’s stability ratio. The results of micro hardening test indicated the more rotational speed of the tool, the more widened W-form hardness profile and it will lead in further hardness drop-off in retreating side of HAZ. The formability studies of welded blanks with same thicknesses indicate the improvement of formability ratio (FR) up to 2.81 times in comparison with the base metal. The TWBs formability limit curves illustrate a reduction of blank’s formability by increasing the blank’s thickness ratios in constant welding conditions
  9. Keywords:
  10. Friction Stir Welding ; Tailor Welded Blanks (TWB) ; Different Thicknesses ; Forming Limit Diagram (FLD) ; Aluminum Blank

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