Abstract
Fracture mechanics calculations are required to validate the safety level defined in design codes to prevent a fatigue failure. The periodic inspection-assessment cycle can lead to the implementation of a fatigue crack repair by crack removal. To improve the fatigue performance of the crack repair, residual compressive stresses induced by peening can be considered. This paper is in relation to the peening effect estimation on stress intensity factors in fatigue crack repaired weldments, since the stress intensity factor is a key parameter in fracture mechanics calculations. A set of T-butt specimens were experimentally fatigue tested and crack propagation data was gathered for the calculation of stress intensity factors. The experiments were designed to estimate the residual compressive stress depth layer and its effect on crack propagation inhibition. Experimental estimation of the peening effect on stress intensity factors in fatigue crack repaired weldments was validated by comparison against an analytical weight function solution. Experimental stress intensity factors determined from a set of fatigue tested T-butt specimens allowed estimating preliminarily that peening has a limited effect on fatigue crack propagation inhibition for edge repaired T-butt weldments subjected to bending loading.
Highlights
Inspection of components subjected to fatigue loading can reveal fatigue cracks presence; depending on the particular component, the option of component replacement or repair in situ is an issue
This paper is in relation to the peening effect estimation on stress intensity factors in fatigue crack repaired weldments, since the stress intensity factor is a key parameter in fracture mechanics calculations
The absence of weldment geometry leads to an approximate SCF reduction of 18% at the notch compared to the T-butt case; flat plate Y factors are lower in early stages of crack growth
Summary
Inspection of components subjected to fatigue loading can reveal fatigue cracks presence; depending on the particular component, the option of component replacement or repair in situ is an issue. Repair in situ is the most feasible option, since offshore structures have to operate continuously. Research on improvements to fatigue crack repair for offshore structures incorporated metal filling of the ground notch by dry or wet welding to improve the fatigue performance of the repaired weldment surface [4]. This paper describes the addition of compressive residual stresses by shot peening to the ground notch surface to improve the fatigue performance of the repaired weldment. It is expected that compressive stresses improve the fatigue crack performance, since cracks grow due to the opening effect induced by tensile stresses. This research is focused on the estimation of the peening effect on stress intensity factors, since K is a key input in fracture mechanics calculations for fatigue life predictions
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