Effects of Shot Peening Using a Circulating Blast Process on Bridge Welded Joints

Shot peening is a well-established industrial practice which can enable beneficial compressive stresses to be created in the surfaces of metal parts.
Alternative mechanical peening has been shown to improve bridge life and performance by utilizing similarly created compressive stresses particularly in “weld
toe” areas of bridge steel. A previous study by Purdue University’s School of Materials Engineering gave a preliminary indication that shot peening could be
used to create similar stress states in the weld toe area of bridge steel. Circulating Blast Processing is envisioned to produce beneficial compressive stresses in
the weld toe areas of bridge steel using a process inherently more amenable for “on-site” treatment of existing bridges than “conventional” shot peening.
The overriding objective of this project is to compare welded joints in bridge steel which have been shot peened with a circulating blast process to similarly
prepared joints that have not received the blast process peening treatment. Welded carbon steel specimens will be created in conjunction with the testing
required to appropriately assess the sample. Four peening conditions are being considered. The key tests to be performed on the various samples are stress
measurement and fatigue.


• Shot and needle peening increase compressive residual stresses in the
weld area.
• Increased compressive residual stress increases fatigue life.
• Needle peening has greater compressive residual stress at the peen line
but not as long of a fatigue life as shot peening due to less compressive
residual stresses away from the peen line
• Improved fatigue life allows longer lasting bridges which saves money