Offshore fatigue crack repair by grinding and wet welding

A fatigue crack repair option based on crack removal by grinding and subsequent filling of the resultant groove by wet welding is presented. Author's experimental and fracture mechanics analysis experience on fatigue crack removal by grinding has demonstrated that a fatigue life extension factor of 2 to 3 is feasible for crack removal done before crack penetration has reached 30% of the plate thickness. However, it has also been demonstrated when groove is left empty, that fatigue life extension after crack removal is mainly due to the stage of fatigue initiation because crack propagation after removal has a higher rate than in as-welded condition. To overcome this situation, this work proposes for an underwater application like in the offshore industry, that filling the grinded groove by means of wet welding would produce a crack repair with a longer fatigue life than the empty groove case.