SEDL / STP / STP1439-EB / STP11308S

High Cycle Variable Amplitude Fatigue of a Nodular Cast Iron

Marquis, GB
Professor, Lappeenranta University of Technology, Lappeenranta,

Rabb, BR
Section Manager, Wärtsilä Technology, Vaasa,

Karjalainen-Roikonen, P
Senior Research Scientist, VTT Industrial Systems, VTT (Espoo),

Pages: 17    Published: Jan 2005

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Abstract

This paper provides a brief summary of life prediction methods for variable amplitude fatigue. Special attention is given to cracks propagating from nominally defect free components in the high cycle regime where a significant portion of the fatigue damage can be attributed to cycles with amplitude less than the fatigue limit observed under constant amplitude loading. Constant and variable amplitude fatigue data for a nodular cast iron are presented. An effective stress method for variable amplitude loaded similar to the Topper model is developed. Most model parameters are derived from constant amplitude S-N curves and the Haigh diagram, but two sets of long life variable amplitude tests are needed to derive the variable amplitude interaction parameters.