Fatigue crack growth retardation and acceleration in coupon specimens and tubular joint element specimens

This experimental study considers load sequence effects in fatigue crack growth in coupon specimens and in element specimens. The coupon specimens were standard edge crack configurations cyclically loaded under four point bending on base metal and welds, whereas the element specimens were full-scale axially loaded tubular joints. Whereas load...

A new analytical approach for describing fatigue load sequence effects

Load sequence effects in fatigue crack growth, such as retardation and acceleration due to a large overload (OL) and underload (UL), can dramatically change the (remaining) fatigue life. These effects can be determined using analytical and numerical tools, often trading accuracy for a steep increase in required calculation time. This paper...

A new model for fatigue load sequence effects in offshore wind turibne substructures and its implications for design life

Measurements at Offshore Wind Turbine (OWT) substructures show that typical loading patterns include overloads, underloads, and shifts in mean stress cycles, due to the everchanging wind direction. These events follow each other in time and are further expressed as load sequences. Load sequences may affect the fatigue life. A novel model...

Approach to include load sequence effects in the design of an offshore wind turbine substructure

Fatigue is one of the main design drivers for offshore wind substructures. Using Fracture Mechanics methods, load sequence effects such as crack growth retardation due to large load peaks can be included in the fatigue damage estimation. Due to the sequence dependency, a method is required that represents the sequences of loads in the design or...

Including load sequence effects in the fatigue damage estimation of an offshore wind turbine substructure

Retardation is a load sequence effect, which causes a reduced fatigue crack growth rate after an overload is encountered. Retardation can be cancelled when the overload is followed by an underload. The net effect is beneficial to the fatigue lifetime of Offshore Wind Turbines (OWTs). To be able to take this into account, computationally...