Elastic-plastic fracture mechanics assessment for steam generator tubes with through-wall cracks

The present work provides an elastic-plastic fracture mechanics (EPFM) assessment scheme for a steam generator tube with a through-wall crack under internal pressure. Noting that the geometry and material are rather uniform for steam generator tubes, and furthermore the only loading to be considered is internal pressure, an engineering EPFM analysis method is proposed to assess through-wall cracks in steam generator tubes. Important outcomes of the present work are closed-form approximations for J and crack opening displacement (COD). Sufficient confidence in the proposed J and COD estimates is gained from good agreements with the finite element results over a wide range of the crack length and pressure magnitude. Another important element of the EPFM assessment is to determine relevant J-resistance curve for steam generator tubes. To improve the accuracy of predicting tube failure, the present paper also proposes a new method to determine fracture toughness using an actual tubular specimen instead of using a standard specimen, from which J-resistance curves of steam generator tubes are obtained. Using the proposed J and toughness estimates, maximum pressures of steam generator tubes with through-wall crack are estimated based on EPFM analysis, which is compared with experimental results and predicted ones based on limit load approach.