天井クレーン模擬プログラム荷重下のガセット溶接継手の疲労強度

抄録

A survey of degradation in overhead traveling cranes was performed and fatigue cracks were often detected in highly stressed regions in cranes that have been used for fifteen years or more. Service stresses of an overhead traveling crane with lifting capacity of 50 kN were monitored and analyzed by the rain-flow method. A fatigue test of gusset welded joints made of SM490A steel was carried out under both constant loading and program loading determined based on the service stress monitoring. The fatigue life of the gusset welded joints is dominated by crack initiation rather than propagation. The crack growth rate of the welded joints under program loading is correlated with an effective stress intensity factor range, ΔK_rem, estimated based on linear accumulation of the stress intensity factor range which takes into account residual stress at each step in a block. The prediction of fatigue propagation life using ΔK_rem agrees with the experimental result in the range of error within 15%, when the crack length is less than 20 mm.