Type I Fatigue-Creep Fracture Map for ECD——The program of fatigue-creep interaction Ⅱ

A series of fatigue-creep fracture life curves for a big ESR-Cast-toShape gas turbine disc(ECD) were obtained from tests called fatigue-creepnteraction test which was performed at constant temperature and fixed max stress with various value of min stress The shape of interaction curve was different from that of the normal S-N curve and creep curve.It could be envisaged as a combination of pure fatigue and pure creep curves.On the ground of the different stress being dependent of fracture lives,the whole interaction curve could be classified into three parts:fatigue(F),creep(C), and mixed(FC) regions.
The larger the max strss the stronger the interaction,the shorter the life.According to the fracture mechanisms and experimental observation of the appearance of fracture surfaces,five distinct fracture mechanism regions (i.e.FF,FCF,CFF,CFC,CC,regions) were occured.
On the basic of macro-micro analysis of fracture a new fatigue-creep interaction map called first type of interaction map was constructed.It provided the basic information of fracture lives and fracture mechanisms.
Discussing several features of interaction,a unified competi tive and cumulative model was suggested to show the nature of fatigue-creep interaction.