Method for Fatigue Life Prediction of Notched Specimen Considering Size Effect.

A method for predicting the fatigue life of notched specimen considering the size effect is proposed. In this method, firstly the notched specimen is made equivalent to a reference smooth specimen. The ratio of the stresses on them is dependent on the fatigue notch factor. The size of the reference smooth specimen is determined according to the principle of having the same area of possible crack initiation surface as the notched specimen. Then based on the weakest link theory, the reference smooth specimen is made equivalent to a smooth specimen which has the same size as the smooth specimen whose experimental data is already available (here after to be called the standard smooth specimen). The ratio of stresses on them is dependent on Weibull exponent and the ratio of their sizes. Based on the above equivalences, the relation between the notched specimen and the standard smooth specimen is established, and the parameter of equivalent stress is introduced. Employing this parameter to refer to the test data of standard smooth specimen would lead to the fatigue life of notched specimen. This model reflects the influence of fatigue damage field area on the fatigue life of notched specimen, and can eliminate the phenomenon that referring to the test data of smooth specimens of different sizes using the same value of fatigue damage parameter would result in different values of fatigue life. An example of centre hole notched LY12CZ specimens is accomplished. The predicted result is in good agreement with the test result, which shows that the method is effective and practical. [ABSTRACT FROM AUTHOR]