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.

Master thesis (2017)

Authors

N.C.H. Troost Mechanical Engineering

Contributors

M.L. Kaminski (supervisor 1)
Lambertus J. Sluys (supervisor 2)
J.H. den Besten (supervisor 2)
P.S. van Lieshout (supervisor 2)
G. Bufalari (supervisor 2)
R.B. Hageman (supervisor 1)
Faculty
Mechanical Engineering
Copyright: © 2017 Niels Troost
More Info
expand_more

Published Date

14-12-2017

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Mechanical Engineering

Abstract

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.