A high-cycle fatigue apparatus at 20 kHz for low-cycle fatigue/high-cycle fatigue interaction testing

High-cycle fatigue (HCF) failures in aircraft engines are attributed to mat erial damage states, created during processing or by in-service loading and environmental conditions, and then propagated to failure by HCF loading. T he loading configuration experienced by aircraft engine turbine blades cons ists of an a-dal load caused by the centrifugal acceleration during rotatio n combined with the tensile and compressive loads caused by the natural vib rations of the blades themselves. To simulate these loading conditions a ne w testing apparatus was developed that is capable of providing interactive low-cycle fatigue/high-cycle fatigue (LCF/HCF) loading, in ratios (of magni tude and frequency) that give a realistic simulation of the actual flight l oads experienced by engine components. This testing apparatus is based on a HCF cell operating at 20 Hz. The cell can also be integrated to a servo-hy draulic load frame, which provides a second fatigue cycle. The objective of this study was to demonstrate the capabilities of the new HCF apparatus vi a thermographic measurements and by performing LCF/HCF interaction tests.