Scatter of fatigue data owing to material microscopic effects
A common phenomenon of fatigue test data reported in the open literature such as S-N curves exhibits the scatter of points for a group of same specimens under same condition.The reason is well known that the microstructure is different from specimen to specimen even in the same group.Specifically,fatigue failure is a typical multiscaling problem so that a fatigue failure model should have the ability to take the microscopic effect and scale transition from micro to macro into account.In the recent work by Sih and Tang,a dual scale crack model based on the restraining stress zone has been proposed and the analytical solution has been obtained by coupling the microscopic and macroscopic scales.Obtained is the dual scale stress intensity factor as well as the dual scale strain energy density factor.By taking as a controlling parameter for the fatigue crack growth from micro to macro,a dual scale fatigue crack growth model is developed in this work which can be able to reflect the material microscopic effect and scale transition in a fatigue process.The objective is in order to re-produce the scattered experimental fatigue data by considering the materiai microscopic effects by using the proposed dual scale model.The fatigue test data of aluminum alloy LY12 plate specimens in the open literature is taken as an example.Two S-N experimental curves for cyclic stress ratio R=0.02 and R=0.6 are selected.The scattered test data points and two S-N curves for both R=0.02 and R=0.6 are exactly re-produced by using the proposed dual scale model.The fact is that the microscopic effect has a pronounced influence on the fatigue life of specimens.The result shows that the accurate prediction of fatigue life is unrealistic if there is no detailed information of material microstructure.
fatigue crack growth micro/macro dual scale crack model mesoscopic fracture mechanics restraining stress zone damage evolution
X.S.Tang
School of Civil Engineering and Architecture,Changsha University of Science and Technology,Changsha,410114,China
国际会议
International Conference on Airworthiness & Fatigue -7th ICSAELS Series Conference(大飞机安全性能与疲劳国际会议)
北京
英文
59-63
2013-03-24（万方平台首次上网日期，不代表论文的发表时间）