Friction Bit Joining (FBJ) is a new technology used primarily in joining dissimilar metals. Its primary use has been focused in the automotive industry to provide an alternative joining process to welding. As automotive manufacturing has continually pushed toward using dissimilar materials, new joining processes have been needed to replace traditional welding practices that do not perform well when materials are not weld compatible. FBJ meets these needs perfectly as it provides strength as well as the ability to join materials of almost any kind.The purpose of this research was to explore different applications of the FBJ process. Traditionally FBJ has used a steel bit to drill through a thin piece of aluminum and weld to a piece of steel behind the aluminum. This research explored a different application of FBJ by using a steel bit to drill through multiple pieces of aluminum and weld to a small steel bit on the backside of the aluminum. The primary goal of this research was to answer two questions. (1) How does drilling impact peak weld strength and (2) Does an optimal shank diameter exist in terms of peak weld strength? As in other research, no universal parameters were found for optimization of lap shear, cross tension and t-peel tests. Drilling was found to be an important factor in peak weld strength. Number of flutes on the consumable steel bit was varied to see the impact of better and worse chip clearance ability. Increasing number of flutes was found to positively impact peak weld strength to a point. Optimal number of flutes was found to be different for each type of testing. It was found that there was an optimal bit head to bit shank diameter ratio that optimized peak weld strength. Again the optimal diameter was different for each test. Bits of different diameters were created and then tested to measure the impact of varying shank diameters on peak weld strength. It was found that there was a strength tradeoff between two localized joint areas in diameter testing. Decreasing the shank diameter increased the amount of overlap formed by the bit head over the top coupon. This shifted strength to the bit head region. While this strengthened the bit head region of the joint, strength was sacrificed in the bit-nut intersection. This tradeoff was consistently found in all test types.
College and Department
Ira A. Fulton College of Engineering and Technology; Technology
BYU ScholarsArchive Citation
Okazaki, Matthew R., "Friction Bit Joining of Similar Alloy Sheets of High-Strength Aluminum Alloy 7085" (2018). Theses and Dissertations. 6866.
FBJ, aluminum, automotive manufacturing, Matthew R. Okazaki