Improvement of Fatigue Life Prediction Accuracy for Various Realistic Loading Spectra by Use of Correction Factors

摘要

Some examples of using the correction factor method for improving the direct Nominal-Stress Approach (LSA) predictions are considered in the report. The N sub exp/N sub calc ratio for a relevant loading spectrum was used for more correct prediction of the considered fatigue life for a not too different loading frequency distribution. It was shown that the application area of the relative method is similar both for the Nominal-Stress and Local-Strain approaches. In the second case a correction is especially needed for obtaining more reliable estimates. For both approaches, it is possible to obtain much improved predictions when the two compared loading cases differ only in the reference stress level, or when the reference stress level and some other important loading spectrum parameters are identical but the loading frequency distribution differs somewhat. For the cases of the same loading spectrum but different materials or different stress concentrations, prediction of the material effect or of the stress concentration effect is also possible, especially from the qualitative viewpoint.