Fracture Mechanics of Multiple Crack Initiations. An Application for Fracture Mechanics Analysis of Gas Turbine Engine Disks

摘要

The purpose of this task was to investigate the current life prediction methodology for multiple crack growth in gas turbine engine components. To this end, experimental and analytical efforts were carried out. Current prediction methods for very small cracks (as small as 0.005 x 0.010 inches) were modified to address the larger interacting cracks produced by the controlled preflaw methods used in this program. The authors conclude that: (1) The modified crack growth life prediction technique currently in use resulted in acceptable but conservative predictions in all cases. Variability in the predictions was also acceptable and was similar to variability in predicted versus actual results for singular crack cases. (2) The multiple-degree-of-freedom approach also produced acceptable life predictions and, in fact, demonstrated reduced variability in predicted versus actual results. It was, however, more complicated to use and did not result in a consistent conservative bias in the life predictions. (3) Based on this study, the modified crack growth life prediction technique currently in use is considered adequate for Retirement-for-Cause applications. The multiple-degree-of-freedom approach offers potential improvements for future use.