Study of Enhancement of Fatigue Strength for Welded Structure due to Flame Line Heating

概要

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Fatigue cracks often initiate at the fillet weld toe of structual discontinuity parts in welded struc-tures. Large tensile residual stress usually acts in these parts in as-weld condition. As the tensile residual stress forces fatigue strength to decrease, we intended that tensile residual stress turns to compressive residual stress for the purpose of enphancement of fatigue strength.Simplified method obtaining flame line heating condition for maximum reduce of residual stress is investigated from the previous study of flame line heating and welded residual stress.As a result, it is confirmed that residual stress with the order of yield stress (σ_??_) in the as-weld condition at boxing weld toe changes to compressive residual stress with the order of -0.5σ_??_ by flame line heating for HT-50 steel.Then fatigue tests of boxing welded joint using HT-50 steel were carried out both for as-welded joint and flame heated joint. Drastic improvement of fatigue strength is observed after flame line heating.
社団法人日本船舶海洋工学会の論文