Fatigue Studies of Stainless Steel Pipes Subject to High Cycle Domain Sinusoidal Thermal Loads

The assessment of fatigue crack growth due to turbulent mixing of hot and cold coolants presents significant challenges, in particular to determine the thermal loading spectrum. A simplified approach in which the entire spectrum is replaced by a sine-wave variation of the temperature at the inner pipe surface has been applied in this study. Particular attention is given to the evaluation of the maximum allowable surface temperature variation before the growth of a given defect occurs in relation to different frequencies of loading. A critical frequency defined as that which gives the shortest crack initiation and growth life will be investigated for different semi-elliptical crack shapes. The application of the method is described for the pipe geometry and loadings conditions reported for the Civaux 1 case.