PREDICTION OF REMAINING LIFE OF HIGH-TEMPERATURE COMPONENTS USING NONLINEAR FRACTURE-MECHANICS

Procedures developed by Ainsworth and Smith and Webster to assess the remaining life of high temperature engineering components containing cracks are presented and applied to a practical example of a 2(1)CrMoV steel pressure vessel operating at 565-degrees-C. The general principles of the procedures are similar. Net section creep rupture is described in terms of the reference stress method and creep crack initiation and growth is predicted using the non-linear (creep) fracture mechanics parameter C*. However, the details of each procedure are shown to differ. The main differences lie in the predicted times for net section creep rupture and creep crack initiation. Ainsworth's method predicts shorter creep rupture times than Smith and Webster's procedure. The initiation time using the Smith and Webster procedure is predicted to occur shortly after loading while Ainsworth's estimate is about 40% of the life of the vessel. Both procedures predict similar times for failure by creep crack initiation and crack growth.