A small-scale creep test for calibrating an efficient lifetime model for high pressure turbine blades

Abstract

Jet engines of airplanes are designed such that in some components damage occurs and grows in service without being critical up to a certain level of damage. Since maintenance, repair and component exchange are very cost-intensive, it is necessary to predict the component lifetime very well in an acceptable amount of time. To efficiently calculate the lifetime consumption with sufficient accuracy under operational conditions, we developed in a former investigation a hybrid approach where the lifetime consumption is calculated from interpolated stress and temperature distributions based on a DoE study with precise aerodynamic and structural mechanics simulations. Since the parameters of the former implemented lifetime models were only estimated from literature values of macroscopic medium- and long-time experiments, it was necessary to develop a special test setup, which allows the determination of the short time creep behavior, which is more relevant for the actual loading situation of real turbine blades. To consider also microstructural influences resulting from the manufacturing of thin-walled single crystal turbine blades, we developed a procedure to prepare small scale creep test samples out of real turbine blades and test them in short- and medium-time creep experiments. Based on the experimental results and the former used literature values, we were able to calibrate a modified creep model which describes the creep fracture behavior from short to long time loading and can now be used for the efficient prediction of the lifetime consumption of turbine blades under real loading conditions.