Combined fatigue experiments on full scale turbine components

The purpose of this paper is to perform experiments on a full scale turbine blade attached to a part of actual turbine disc at elevated temperature, which can accurately predict the life of a fir-tree contact under high cycle fatigue (HCF)/low cycle fatigue (LCF) combined loading. Moreover, the effect of shot-peening on the fatigue lives of the turbine attachments is investigated experimentally by comparing those of unpeened ones. An experimental system for a full scale turbine blade attached to a part of actual turbine disc at elevated temperature is established in this paper, with a new HCF/LCF combined loading scheme and a design of blade clamp. The new combined fatigue loading method achieves a noninterfering treatment of the high cycle and low cycle loading by placing low cycle loading exerting point to the back of the mortise. Then fatigue tests were performed on six used turbine components to investigate the effect of shot-peening on fatigue life compared with the unpeened ones. This test system ingeniously achieves HCF/LCF combined loading of the full scale turbine component, and a special design of the blade clamp successfully simulates the stress field of the turbine blade. Experimental life data show that the shot-peening process greatly improves the used turbine fir-tree attachment's life. The present study provides an experimental method to simulate HCF/LCF combined loading of a full scale fir-tree turbine attachment at elevated temperature at laboratory. Compared with the unpeened turbine components, the fatigue lives of the shot-peened ones are increased greatly. Mean life of the shot-peened turbine attachment is 5.23 times longer than that of the unpeened.