Simplified Fatigue Evaluation
Starting CAEPIPE Version 13.00, a new feature is added to perform Simplified Fatigue Evaluation. This evaluation can be turned ON or OFF through Loads > Simplified Fatigue.
When this evaluation is turned ON, CAEPIPE will compute the ‘equivalent reference displacement stress range cycles (N)’ expected during the service life of the piping system as per the Piping Code selected for analysis. When done, it will use this computed ‘equivalent reference displacement stress range cycles (N)’ to determine the Stress Range Reduction Factor (f or U) in computing the Expansion Allowable Stress as per the Piping Code selected. Refer to the Section titled “Simplified Fatigue” in CAEPIPE Code Compliance Manual for details on the equations used to compute ‘N’ for various Piping Codes.
When the Simplified Fatigue Evaluation is turned ON, then the ‘equivalent reference displacement stress range cycles (N)’ computed as per Simplified Fatigue Evaluation will internally overwrite the Number of Thermal Cycles (N) that was input through Options > Analysis > Temperature (= 7000 by default) for computing the Expansion Allowable Stress.
Steps to perform Simplified Fatigue evaluation are given below. Refer to the Section titled “Fatigue Cycles” in this manual for further details.
1. Turn ON the required Expansion load case(s) for Simplified Fatigue Evaluation through Loads > Load Cases.
2. Input the actual number of Thermal Cycles corresponding to each Expansion load case selected for this evaluation through Misc > Fatigue Cycles.
3. Once done, turn ON (tick) or OFF (un-tick) the Simplified Fatigue Evaluation through Loads > Simplified Fatigue.
Note:
Simplified Fatigue Evaluation option will be grayed out (disabled) from the Loads menu for any one of the following reasons.
1. Piping Code selected for analysis is equal to ASME NM.1/ASME NM.2/IGEM/ EN 13941/DNV-ST-F101/ISO 14692/BS 806(1986)/NONE.
2. No Expansion load case is turned ON for this Simplified Fatigue Evaluation.
3. None of the selected Expansion load cases includes a non-zero input for the actual number of thermal cycles.