Influence of Different Load Histories on the Cyclic Material Behavior of Nodular Cast Iron for Thick-walled Application

Bleicher, Christoph (Fraunhofer Institute for Structural Durability and System Reliability LBF)


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.