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Abstract
The microstructure sensitive multistage fatigue model captured the fatigue life of a powder metal FC-0205 steel alloy. Uniaxial strain controlled fatigue data and microstructure information from sets of high and low porosity specimens calibrated the model. Strain–life behaviour depicted that above the plastic strain limit of 0·002 mm mm−1 in the low cycle fatigue regime, where ubiquitous plasticity occurred, the different porosity levels gave distinct, visibly different results. However, specimens tested below the plastic limit in the high cycle fatigue regime, where failure was dominated by local cyclic microplasticity, showed unclear fatigue lives at different porosity levels. Fractography using scanning electron microscopy showed no clear presence of striations; however, asserted striations in powder metal specimens were similar to geometrical features observed on fracture surfaces of monotonically loaded specimens. The experimental and microstructure data calibrated a fatigue model that allowed for satisfactory prediction of the varying porosity specimen strain–life curves.
Acknowledgements
This research was funded by US Automotive Materials Partnership (AMD410) contract no. FC-26-02OR22910 with guidance from H. I. Sanderow (Center for Powder Metallurgy Technology), R. A. Chernenkoff (Metaldyne), P. Rosa (DaimlerChrysler), S. G. Wakade (GM Powertrain) and G. Weber (Ford Motor Company). We would also like to acknowledge the Center for Advanced Vehicular Systems at Mississippi State University for supporting this work. Discussions and guidance about this research from Dr R. German (SDSU) to Dr Allison are gratefully acknowledged. Permission to publish was granted by Director, Geotechnical and Structures Laboratory.