Abstract
Various peening techniques have been used to improve the fatigue strength of steel structures. Among them, base metal impact hammer peening shows significant improvement in fatigue strength in ordinary steel, but the effect on high-strength steel has not been sufficiently studied. Accordingly, this study applied base material hammer impact peening to test specimens of 780 MPa grade high-strength steel (HT780) and 490 MPa grade ordinary steel (SM490), and the residual stress was measured and simulated. The experimental results clarified that a large compressive residual stress was introduced into the inner part of the plate thickness near the indentation in the high-strength steel, although the range of introduction of residual stress was equivalent in both the ordinary steel and high-strength steel.
Highlights
Steel structures support industries and infrastructures such as bridges, buildings, power plants, industrial plants, energy storage, and transportation, and are important social capital in Japan
We focused on hammer peening, which is a method for converting tensile residual stress at the weld toe to compressive residual stress, to improve the fatigue strength of the weld zone
The surface depression of high-strength steel (HT780) caused by base metal hammer impact peening (BMHIP) was about half that of ordinary steel (SM490), but the maximum value of the residual stress distribution in the surface layer was about −400 MPa for both the high-strength steel and ordinary steel, and the distribution was similar
Summary
Steel structures support industries and infrastructures such as bridges, buildings, power plants, industrial plants, energy storage, and transportation, and are important social capital in Japan. These steel structures must be able to be used safely in normal service conditions, and must not collapse in abnormal situations such as disasters, at which times fatigue becomes a problem. We used a technique for improving fatigue strength by base metal hammer impact peening (BMHIP). A previous study [5] clarified the relationship between the surface residual stress due to BMHIP, the number of impacts, and the effect of improving fatigue strength for ordinary steel (490 MPa grade steel)
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