AutoPIPE has a very robust fatigue analysis based on Nuclear Class 1 piping. The interface and reporting is very intuitive and well developed.
Evaluating the cumulative effect of the stress cycles experienced by the piping system is done first by deciphers the stress cycles. The number of times each stress cycle of type 1, 2, 3, etc. is repeated during the life of the system shall be designated as n1, n2, n3, etc. This is an input by the user in AutoPIPE. Cycles shall be superimposed such that the maximum possible peak stress ranges are developed.
For each type of stress cycle, AutoPIPE determines the alternating stress intensity (Salt) from Equation 14 in ASME Section III. For each value of Salt, the applicable design fatigue curve is used to determine the maximum number of cycles permitted if this were the only cycle occurring. (These fatigue curves are found in the appendices to the code).
These values shall be called N1, N2, N3, etc. User defined fatigue curves can also be used. If N1 is greater than the maximum number of cycles defined in the applicable design fatigue curve the value of n/N may be taken as zero.
For each type of stress cycle, the usage factor is calcuted.
AutoPIPE then uses its intelligent analysis sets to setup the proper calculations for the fatigue analysis.
Unlike other analysis codes, the Code Combinations for ASME NB are not created automatically. They are managed by the Stress Summary which also defines the fatigue analysis. The Stress Summary combines the various load cases together that describes each specific plant operating event in line with the code requirements and assigns number of cycles that each event (or load pair) occurs during the plant lifetime. The program automatically calculates the maximum equation stress results and determines the incremental usage factor based on the maximum occurrence of each load pair. The definitions in the stress summary form the basis of the full verification and fatigue analysis.
Finally, the fatigue report includes all the required information in an intuitive format including the iterations, load sets pairs, and results including the cumulative usage factor.
Training is available if needed to show you all that is needed to setup up a fatigue analysis. Check out this feature and let us know what you think.
Please submit a service request with your archived model (APC file) attached so we can investigate your question fully.
Take a look at Bentley's Learn Server for the AutoPIPE Nuclear training:
Thank you for this excellent summary.
I had one question, when I look at the NB-3600 CUF calculated by AutoPIPE, it has a value of 0.000. In the Fatigue summary, it shows the allowed cycles as "INFINITY". Why is it using infinity for allowed number of cycles? It should take it from the ASME Section III Fig I.9 curve for carbon steel. Note that my alternating stress intensity Salt is above the endurance limit.
I am interested to see more details in tutorial and would like to learn the steps how to run Fatigue evaluation as described above, and wondering if there is video available, if yes, where can I find it?