13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Comparing Crack Growth Testing and Simulation Results Under Thermo-Mechanical Fatigue Conditions Chris Timbrell1, Ramesh Chandwani1,*, Steve Jacques2, Lee Waterhouse2, Andrew Wisbey2, Steve Williams3 1 Zentech International Limited, 590b Finchley Road, London, NW11 7RX, UK 2 Amec Technical Services (was Serco), Walton House, Birchwood Park, Risley, Warrington, Cheshire. WA3 6GA, UK 3 Rolls-Royce plc, PO Box 31, Derby. DE24 8BJ. UK * Corresponding author: ramesh@zentech.co.uk Abstract 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. Keywords thermo-mechanical fatigue, crack growth rates, finite element analysis, crack growth simulation 1. Introduction The ultimate objective of simulating thermo-mechanical testing by analysis is to develop a method which can be applied to crack growth prediction during complex loading cycles. One particular application is for aerospace engine flight cycles. Such flight cycles consist of out-of-phase stress and temperature time histories having duration of order of several hours. An example is shown in Figure 1. 0 200 400 600 800 1000 1200 ‐100 0 100 200 300 400 500 600 0 5000 10000 15000 20000 25000 30000 Stress (MPa) Temperature (degrees C) Time (s) Temperature Stress Figure 1. Typical stress and temperature time histories For a crack located within a component experiencing such flight cycles, each point along the crack front will experience a slightly different stress and temperature time history. The salient features are: • Peak temperature and stress occur at the end of the climb phase with the temperature
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