Comparing Crack Growth Testing and Simulation Results Under Thermo-Mechanical Fatigue Conditions

Chris Timbrell, Ramesh Chandwani, Zentech International Ltd., Steve Jacques, Lee Waterhouse, Andrew Wisbey, Amec Technical Services (was Serco), Steve Williams, Rolls-Royce plc

13th International Conference on Fracture, Beijing, China, 16-21 June 2013

As the need for improved prediction of component life and development of new materials for use at high temperatures becomes more demanding, there is increasing requirement for a detailed understanding of thermo-mechanical fatigue (TMF) behaviour including the combined effects of fatigue and dwell on the overall crack growth rates under such conditions. To generate experimental TMF crack growth test data, a conventional servo-electric load frame, used in combination with a radiant lamp furnace, has been employed. The method for the measurement of crack growth under the TMF load cycle is also described. The performance of the experimental method is demonstrated with trials on an advanced nickel-based superalloy, RR1000. To reduce future testing requirements, simulation via the finite element method provides a means for crack growth prediction. This clearly requires validation with real test data at the outset. A method is described whereby separate fatigue and time dependent growth data can be combined and applied to TMF load cycles ranging from simple test cycles to full flight cycles. Results of this method used in conjunction with finite element based crack growth simulation are compared with experimental data, using the test method described above, from several TMF load cycles for RR1000 specimens.