The aim of the project is to provide a basis for extended use of the life potential of existing and future advanced aero-engine fracture critical parts (e.g. disks).
A parametric model has been developed to perform cycle by cycle crack propagation predictions for aero engine disks. The unknowns in the model were determined by extensive specimen testing.
Several algorithms have been developed which account for part or all of the observed phenomena:
the Walker model for the R-dependence of crack propagation;
the Elber model for crack closure;
the Chaboche model for the elastoplastic behaviour and crack initiation;
the Paris and Forman Laws for crack propagation;
newly developed models to account for retardation due to cycle interaction.
The algorithms were validated using the complex cycle and disc spinning tests.
The implementation of these algorithms into life monitoring systems will lead to better life predictions and so result in an increase of safety and a more economical use of resources. Furthermore, the successful application of the potential drop (PD) technique to a disc spinning test will allow for a more accurate crack propagation tracking in real engine component tests.
The implementation of the algorithms into real time engine monitoring systems will reduce the uncertainty of component life prediction by a factor of 2, resulting in improved component reliability, and will support the introduction of damage tolerant lifing concepts.
This aim shall be achieved by means of algorithms for life prediction and usage monitoring. Those algorithms shall be based on models for crack initiation and crack propagation. They will be able to predict the behaviour of cracks under variable amplitude loading and transient temperatures such as aero-engine disks experience due to real operating conditions.
The algorithms shall make use of parametric models which allow for a cycle by cycle crack initiation and propagation prediction in order to support the extent of usage by in-flight real time engine usage monitoring. The parameters will be determined by experiments on Corner Crack Specimen (plain), Notched Specimen (plain), Notched Specimen (round with circumferential notch) and biaxial loading specimen (cruciform shaped). The predictions of the algorithms will be verified by components tests (disk spinning tests).
10127 Torino (Turin)
DE2 8BJ Derby
SA2 8PP Swansea