Development and Characterization of Friction Bit Joining: A New Solid State Spot Joining Technology Applied to Dissimilar Al/Steel Joints Development and Characterization of Friction Bit Joining: A New Solid State Spot Joining Technology Applied to Dissimilar Al/Steel Joints
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.
School:Brigham Young University
School Location:USA - Utah
Source Type:Master's Thesis
Keywords:friction bit joining spot welding stir self piercing rivet riveting selfpiercing resistance solid state solidstate aluminum to steel al joints dissimilar metal and fbj spr rsw fsw sfsw fssw
Date of Publication:06/10/2008