Confused sea-state induced fatigue

Confused sea-state induced fatigue: Joint swell and wind seas induced multiaxial stresses: the influence of confused sea-state induced multiaxial stress-states on fatigue damage of a USCG cutter.

Troost, Niels (TU Delft Mechanical, Maritime and Materials Engineering)

Kaminski, M.L. (mentor)
Sluys, Lambertus J. (graduation committee)
den Besten, J.H. (graduation committee)
van Lieshout, P.S. (graduation committee)
Bufalari, G. (graduation committee)
Hageman, R.B. (mentor)

Delft University of Technology

Valid

2017-12-14

Marine structures are mostly exposed to mild and moderate sea-states, where the structural response is elastic. Characteristics of environmental loading are highly stochastic in nature, resulting in stress-states that might be multiaxial. This thesis attempts to identify the source and effect of these multiaxial stress-states on fatigue damage in frigate type structures.
A stress invariant based method called the Projection-by-Projection approach was adopted to estimate damage in the presence of multiaxial stress-states. This method was tested for its applicability and modified, where necessary, to better cope with the encountered stress-states. The design rules by the International Institute of Welding (IIW) were also used to be able to distinguish physical phenomena from methodological properties.
The available data consisted of strain measurements from the United States Coast Guard (USCG) Cutters Bertholf and Stratton. The Bertholf was equipped with the WaMoS wave radar. Measured wave data was reinforced with simulated waves to make the research independent of encountered sea-states.
It was concluded that multiaxiality is most relevant at low damage estimates (i.e.: low wave). The governing influence factor is the incoming wave direction. It was also shown that multiaxial stress-states may significantly contribute to fatigue damage (up to a factor 2, depending on the structural detail and location in the vessel) at an estimated life time of 2 · 10^{6} cycles.

Fatigue
multiaxial
marine structures

http://resolver.tudelft.nl/uuid:c845b412-cab2-4c14-b2be-7bc8fd03cd6d

2017-12-31

Student theses

master thesis

© 2017 Niels Troost