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Influence of different load histories on the cyclic material behavior of nodular cast iron for thick-walled application

: Bleicher, Christoph; Wagener, Rainer; Kaufmann, Heinz; Melz, Tobias

International Society of Offshore and Polar Engineers:
Twenty-seventh International Ocean and Polar Engineering Conference 2017. Proceedings : San Francisco, California, June 25-30, 2017, CD-ROM
Cupertino, Calif.: ISOPE, 2017
ISBN: 978-1-880653-97-5
International Ocean and Polar Engineering Conference <27, 2017, San Francisco/Calif.>
Conference Paper
Fraunhofer LBF ()
nodular cast iron; cyclic material behavior; fatigue; thick-walled; wind energy; overload

The present article discusses the cyclic material behavior, in the form of stress-life, strain-life and cyclic stress-strain curves, of five different nodular cast iron materials derived from specimens taken from heavy-walled cast blocks and a main frame of a nacelle of a wind energy turbine. Results are shown for both static and cyclic strain-controlled tests performed at room temperature under constant and variable amplitude loading at Rε = -1 and (equation), respectively. The load-time history used for the tests under variable amplitude loading is taken from a wind turbine hub. To check the influence of overloads on the fatigue strength of the materials, a negative overload with a load ratio of (equation) was introduced provoking positive mean stresses in the specimen and thus a shorter lifetime. These overloads were introduced at the beginning and after one transit of the load-time history to show their influence when occurring right on the first day of machinery usage to neglect any influence of a cyclic hardening and after a certain cyclic usage, when probably a hardening has taken place.