Research project

The temperatures and stresses in different sections of turbine blades in aero engines vary strongly. Normally these temperature and stress distributions are calculated numerically to give valuable information for the design of turbine blades and aero engines. Unfortunately, it is difficult to check experimentally, whether the models used for these simulations correspond reliably to the actual stress and temperature distributions in the turbine blade. In this project, the actual stresses and temperatures which occurred in different sections of a turbine blade during service are deduced by comparing the local lattice misfits in the different areas with the lattice misfits encountered in specimens which have been creep-deformed under well defined deformation conditions. In order to measure the lattice parameters and misfits with the necessary high lateral resolution the method of convergent beam electron diffraction (CBED) in the transmission electron microscope is employed. While CBED is the only method that allows to measure local lattice parameters with high lateral resolution, the evaluation procedures to deduce the lattice parameters from the CBED patterns are complicated and time-consuming. To establish CBED measurements as a useful tool for routine investigations, as is necessary in the present project, it is necessary to develop faster evaluation procedures for CBED patterns without loosing accuracy. This goal is addressed by introducing new computer-supported techniques for the evaluation of lattice parameters which have already been applied successfully to aluminium and silicon before and that are now used with good success for the first time in studies on nickel-base superalloys.