Abstract

Friction bit joining (FBJ) is a new solid-state spot joining technology developed in cooperation between Brigham Young University of Provo Utah, and MegaStir Technologies of West Bountiful Utah. Although capable of joining several different material combinations, this research focuses on the application of FBJ to joining 5754 aluminum to DP 980 steel, two alloys commonly used in automotive applications. The thicknesses of the materials used were 0.070 inches (1.78 mm) and 0.065 inches (1.65 mm), respectively. The FBJ process employs a consumable 4140 steel bit and is carried out on a purpose built research machine. In the first stage of the weld cycle the bit is used to drill through the aluminum top sheet to be joined. After this, spindle speed is increased so that the bit tip effectively forms a friction weld to the steel bottom sheet. Momentary stoppage of the spindle facilitates weld cooling before the spindle is restarted, shearing the bit tip from the bit shank, and retracted. Incorporated into the bit tip geometry is a flange that securely holds the aluminum in place after joint formation is complete. This research consists of several developmental steps since the technology only recently began to be formally studied. Initial joint strengths observed in lapshear tensile testing averaged only 978.5 pounds (4.35 kN), with a relatively high standard deviation for the data set. Final lapshear tensile test results were improved to an average of 1421.8 pounds (6.32 kN), with a significantly lower, and acceptable, standard deviation for the data set. Similar improvements were realized during the development work in cross tension tensile test results, as average strengths increased from 255.8 pounds (1.14 kN) to 566.3 pounds (2.52 kN). Improvements were also observed in the standard deviation values of cross tension data sets from initial evaluation to the final data set presented in this work.

Degree

MS

College and Department

Ira A. Fulton College of Engineering and Technology; Technology

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2008-06-18

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd2425

Keywords

friction bit joining, spot joining, spot welding, friction welding, friction stir welding, friction stir spot welding, spot friction welding, self piercing rivet, self piercing riveting, selfpiercing, resistance spot welding, solid state joining, solid state welding, solid state spot joining, solid state spot welding, solidstate, aluminum to steel joining, al/steel joints, dissimilar metal welding, dissimilar metal joining, welding aluminum to steel, welding aluminum and steel, fbj, spr, rsw, fsw, sfsw, fssw

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