A relative crack opening time correlation for corrosion fatigue crack growth in offshore structures

Abstract

A considerable amount of research has been carried out on the prediction of mean stress effects on fatigue crack growth in structures. Newer types of structure are now being developed for use in highly dynamic, harsh marine environments, particularly for renewable energy applications. Therefore, the extent to which mean stresses can enhance corrosion‐assisted fatigue damage in these structures needs to be better understood. A new theoretical model that accounts for mean stress effects on corrosion fatigue crack growth is proposed. The model is developed based on the relative crack opening period per fatigue cycle and by considering only the damaging portion of the stress cycle. The baseline data for the modelling exercise are the data obtained at a stress ratio of 0.1 in air and seawater tests conducted on compact tension specimens. The model is validated by comparison with experimental data and with other fatigue crack propagation models. The proposed model correlates fairly well with experimental data and the other models examined.

Corrosion fatigue crack growth mechanisms in offshore monopile steel weldments

“…This can be argued considering the investigations that have shown different crack growth behaviour in similar materials with respect to increasing mean stresses . Thorpe et al . found that at free‐corrosion potential, crack growth rates in BS 4360 50D steels were significantly enhanced as the mean stress was increased from 0.5 to 0.7.…”

“…. Mean stress effects on crack growth rates have been described as the ratio of the minimum to the maximum stresses used for testing . However, it was mentioned by Burnside et al .…”

Report of Committee III.2: Fatigue and fracture

“…Both the strength and mechanism parameters, intersect logC and slope m, are affected. Model estimates and sinusoidal constant amplitude experimental data correlate fairly well (Adepipe et al, 2016).…”

Fatigue damage criteria classification, modelling developments and trends for welded joints in marine structures

“…With respect to the material, loading & response and environment dimensions, mechanical-and electro-chemical properties of the base material, heat affected zone and weld material, frequency, mean and residual stress, humidity and temperature (e.g. Guedes Soares et al 2009;Adepipe et al 2015Adepipe et al , 2016 affect and interact with the corrosion damage process as well. The geometry dimension related typical uniform corrosion induced plate thickness reduction implicitly increases the far field stress level.…”