Abstract
Fatigue strength is known to decrease with increasing dimension of the component. This is due to a technological size effect, related to the production process, and to a geometrical size effect, due to a higher probability of finding a large defect. To investigate the latter, an heavy-walled component made of Ductile Cast Iron (DCI) has been trepanned and a fatigue test plan has been carried out using 4 different specimen geometries. An attempt has been made to relate the resulting fatigue strength using a weakest-link approach based on the effective volumes and surfaces. This approach seems to work well only in cases of different specimen's lengths. Some of the fracture surfaces were analyzed by means of SEM and the initiating defects were identified and measured. An approach in which the defects population can be randomly distributed in the specimen has been tried. Virtual fatigue tests have been carried out by considering pure propagation of the worst defect. The resulting fatigue curves showed that this approach is promising but needs further description of the initiation phase.
Highlights
It is a well known phenomenon that the fatigue strength of material decreases with increasing the size of the component
This is due to a technological size effect, related to the production process, and to a geometrical size effect, due to a higher probability of finding a large defect
An heavy-walled component made of Ductile Cast Iron (DCI) has been trepanned and a fatigue test plan has been carried out using 4 different specimen geometries
Summary
It is a well known phenomenon that the fatigue strength of material decreases with increasing the size of the component. Fatigue initiates from discontinuities, that may be considered as micro-cracks [1]. Fatigue specimens of 4 different geometries were machined from a component made of Ductile Cast Iron GJS-400 in order to test different volumes and surfaces
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