CRACK GROWTH RATE IN STRAIN-CONTROLLED LOW CYCLE FATIGUE

Strain-controlled low cycle fatigue tests were performed for various test-piece geometries, frequencies, CTOD ratios and strain ranges in order to find out the behaviors of fatigue crack growth on pressure vessel steel. The influences of cyclic material properties and deformation rates on da/dN were discussed. The possibility of taking the parameter Δ CTOD ( Δδ t ) as the basis for describing strain-controlled low cycle fatigue behaviors was examined. A specially designed High Strain Tension specimen (HST) was used to simulate high-strain fields in pressure vessels and Compact Tension specimens (CT) were also tested. The relationship between da/dN and Δ CTOD was obtained from the results of two types of specimen.