Fatigue behavior of innovative alloys at elevated temperature

F. Berto, P. Gallo, S.M.J. Razavi, M.R. Ayatollahi
2017 Procedia Structural Integrity  
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation
more » ... mmercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data. Abstract 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. Abstract 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.
doi:10.1016/j.prostr.2017.04.029 fatcat:343qjzmf75gv5efew6jiqpw3s4