Fracture Mechanics Analysis of Fatigue Crack Repaired Joints

Abstract

Fatigue life predictions based on fracture mechanics calculations are required to satisfy an increasing level of safety demanded by industry. These predictions are mainly used to schedule NDT inspections and with inspection data make structural integrity assessments. The periodic inspection-assessment process can lead to the implementation of a fatigue crack repair by crack removal. Fracture mechanics analysis is used again to determine whether or not a repair will be effective. For the case of tubular joints, in offshore structures, once repairs have been shown to be ineffective it is usually required to install a clamp to maintain the continuity of joint members if the structure is still required for production. In this paper a fracture mechanics analysis of crack repaired joints based on Y factors is presented. The analysis is used to predict fatigue life after crack removal and is validated against T-butts experimental data. The analysis is also extrapolated for the prediction of fatigue life of crack repaired tubular joints.

Fatigue performance of tubular X-joints with PJP+ welds: II — Numerical investigation

“…Estimations of the fatigue crack propagation life, based on the Paris law, provide a convenient approach in assessing the fatigue life of the cyclically loaded, large-scale structural and mechanical components [4][5][6][7][8][9][10]. Olowokere and Nwosu [11] demonstrated that the crack propagation life estimated using the Paris law with numerically computed stress-intensity factors (SIFs) using spring elements agreed well with the experimental results obtained from cracked tubular T-joints subjected to axial loads and brace in-plane bending.…”