Assessment of Field Surface Treatments for Prolonging the Life of Steel Welded Joints Subjected to Fatigue Loading

Abstract

In heavy truck applications welds are commonly used to join structural steel components that are subjected to cyclical loads. In cases where a weld fatigue issue is discovered in the field the customer desires to have low-cost methods to increase service life. This research was initiated to recommend a process for treating welded joints on heavy trucks that can be accomplished in the field with limited manufacturing resources. Surface peening is a cold working process that introduces beneficial residual compressive stresses in the surface of a work piece. Two different surface peening processes were evaluated for their ability to increase fatigue life in fillet welds. These processes were hammer peening and rotary flap peening. T-shaped fillet weld test samples were fabricated and subjected to cyclic loading in three configurations; as-welded, welded and hammer peened, and welded and flap peened. Metallographic inspection was used to further evaluate the test samples following fatigue testing. Fatigue life estimation methods were considered based on both experimentally measured strain data and stress/strain results obtained through the use of finite element methods. Stress-life analyses based on weld classifications established by British Standard BS7608 were conducted. Strain-life analyses based on the use of A36 steel fatigue properties with the application of a fatigue notch factor were also conducted.