Fatigue strength for pipes with allowable flaws and design fatigue curve

To evaluate the structural integrity for nuclear power piping systems, low cycle fatigue tests were performed on 4 in. diameter carbon steel pipes with flaws. The flaws are local wall thinning, taking into account the minimum wall thickness required for design pressure and circumferentially part-through cracks based on the acceptance standards in the ASME Code Section XI. The applied load was four-point bending with or without an internal pressure under displacement-controlled conditions at ambient temperature. The results show that the flaws above do not influence the integrity of the piping system and pipes do not break within the seismic regime of stress and cycles.