A method of fatigue life prediction for service extension of aircraft structures

How important is the accuracy of the applied load spectra with respect to the fatigue life? With a focus on the control points of an F-16 fighter jet, a correlation between applied loading and the resulting service life is investigated in order to develop a systematic method for service life prediction and extension. By using ANSYS to run finite element analyses of solid models created using Solid Edge and Pro/Engineer under assumed loading conditions, the stress field information was generated. This information is then imported into MSC. Fatigue or AFGROW to perform a crack growth analysis in order to predict the service life. In order to check for accuracy, the results are compared to the data of an existing service life extension program study. The effect of small variations in load spectra is then also investigated, and the results are compared. It has been found that even very small differences in loading or load spectra can cause a significant difference in fatigue life prediction.