Fatigue of Thick Steel Plates Bent to a Low R/t Ratio

Abstract

The use of cold-bent plates, instead of welded corner joints, in the fabrication of pressure vessels can reduce production costs. The cold-bending operation is relatively easy, inexpensive, and requires minimum quality control. The attractiveness of using cold-bent plates as a potential substitute for plates with welded corner joints motivated the fatigue study described here. Fatigue test resutls are reported for nineteen 25-mm thick HY80 and HY100 steel plates, cold-bent to a nominal bend angle of 90 deg and an R /t (inner bend radius/thickness) of 1.5, and ten 25-mm thick HY80 welded corner joints. Testing was performed under zero-to-tension loading (stress ratio R = 0) at room temperature and at a frequency of 4 Hz on specimens that retained the actual cold-bending-induced residual stresses. These test results indicate that the cold-bent plates may be a good alternative to welded corner joints for cyclic loading histories.