Mean Stress Correction Procedure in Fatigue Evaluation for High Pressure Vessels
One important issue in the fatigue evaluation that must be addressed is the mean stress correction procedure. ASME Div.3 is provided with the mean stress correction procedure. The predicted equivalent alternating stress intensities Seq are compared with the experimental results for push-pull fatigue tests with mean stress for JIS SCM440 and JIS SUS630 H1075. Seq per ASME Div.3 are not coincident with the experimental results. In case of high ratio of tensile mean stress to tensile strength, the difference becomes large and it is un-conservative. On the other hand Seq per KHK Standard are coincident with experimental results. The fatigue test results for pressurized cylinder tube by Davidson and Findley are also compared with predicted values per ASME Div.3 and KHK Standard. The results of comparison are same as that for above mentioned push-pull fatigue tests. Based on the experimental verification, the authors recommend that the mean stress correction procedure per KHK Standard be implemented in ASME Div.3.