RESEARCH ON HCF TESTS AND DAMAGE MODEL OF TC11 ALLOY WELDED JOINTS

摘要

In the paper, the loading controlled fatigue tests of TC11 alloy welded joints had been done, micro characteristic of fatigue fracture surface had been studied by SEM (scan electron microscope) as well. Test results revealed that two types of fatigue source on fracture surface of the welded joints were found, say, surface fatigue source and internal fatigue source. Then S-N curve about two types were obtained respectively. The fatigue life of the welded joints which have surface fatigue source are 35-65% as long as of that have internal fatigue source. Moreover, the fractal dimension of fatigue source rejoin on fracture surface had been calculated, which based on the grayscale distribution of the fracture surface's SEM imagines. The relationship between fractal dimension and fatigue life were surveyed. Finally, a fractal damage model which concern with macro and micro damage was established based on the combination of damage mechanics theory and geometry fractal theory.