Date of Award

Summer 2006

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

Stango, Robert

Second Advisor

Domblesky, Joseph

Third Advisor

Fournelle, Raymond


In this thesis, a rotary bristle tool comprised of filaments with spherical tips was designed for performing peening processes. The concept of this tool was based on simulating a single impact of the shot peening process with a single impact from a bristle tip. For a direct comparison between the bristle peening tool and conventional shot peening, a pre-impact energy analysis was used to determine an equivalent shot peening process. The design criteria for this comparison were based upon rigid body mechanics. Moreover, the dynamic response of the bristle was studied theoretically by using FEM and experimentally by using the newest technology in high-speed digital photography. Impact craters were experimentally produced by the bristle peening process and were directly compared to the crater geometry produced by conventional shot peening. Both an optical microscope and a scanning electron microscope (SEM) were used to examine an array of craters. From the information attained, modifications in bristle geometry were made that yielded impact craters similar to conventional shot peening. With the final bristle design and equivalent shot peening process determined, initial testing was performed by peening aluminum 6061-T6 Almen strips. For the two different processes, the curvature of the peened Almen strips was measured using an Almen gage, and the morphology of the peened surfaces was examined using an optical microscope. Finally, a rotating bending fatigue test was performed on as-machined, bristle peened and shot peened aluminum 6061-T6 specimens using an R. R. Moore fatigue tester. The results showed a fatigue life increase of up to 150% for the bristle peened specimens when compared to the as-machined ones. Also, a fatigue life increase of up to 330% was obtained from the shot peened specimens over the bristle peened specimens. From this data, it was concluded that the bristle tool can be used as a viable peening processes, and that further research is warranted for improving the performance of bristle peening processes.



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