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

This article discusses the cyclic material behavior-in the form of stress-life, strain-life, and cyclic stress-strain curves- of different nodular cast iron materials derived from specimens taken from cast blocks and a main frame 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 for alternating loading, respectively. The load-time histories used for the tests under variable amplitude loading are taken from a wind turbine hub and main frame. A negative overload was introduced to check the influence of overloads on the fatigue strength of the materials, provoking positive mean stresses in the specimen and thus a shorter lifetime.