High Temperature Fatigue Tests of Cu-be and 40CrMoV13.9 Alloys

The present paper summarizes the results from uniaxial-tension stress-controlled fatigue tests performed at different temperatures up to 650 °C on Cu-Be and 40CrMoV13.9 specimens. Two geometries are considered: hourglass shaped (both materials), plates weakened by a central hole (Cu-Be alloy). The motivation of the present work is that, at the best of authors’ knowledge, only a limited number of works on these alloys under high-temperature fatigue are available in the literature and no results deal with notched components.In the present contribution, after a brief review of the recent papers, material properties and experimental procedure are described. The new data from un-notched and notched specimens are summarized in the corresponding fatigue curves.The Cu-Be specimens fatigue data are re-analysed in terms of the mean value of the Strain Energy Density (SED). The approach, successfully used by the same authors to summarise fatigue data from notched specimens made of different materials tested at room temperature, is extended here for the first time to high-temperature fatigue. In the plates with central holes the SED is evaluated over a finite size control volume surrounding the highly stressed zone at the hole edge. A value of the radius equal to 0.6 mm seems to be appropriate to summarize all fatigue data in a quite narrow scatter-band. Thanks to the SED approach it is possible to summarise in a single scatter-band all the fatigue data, independent of the specimen geometry.