Elastic ratcheting analysis

Elastic Stress Analysis - Simplified Elastic-Plastic Method. This method may be used in the case where the method indicated above shows the Pr + Pb + Q stress limits are not satisfied, but indicates that the Pl + Pb + Q range and excluding thermal effects must be less than Sps- Additionally, the effective alternating equivalent stress amplitude must include the fatigue penalty factor, ICej, which is based off of the simplified elastic-plastic criteria from the pre-2007 Section VIII, Division 2. Finally, a thermal stress ratcheting assessment must be made. 

Elastic Stress Analysis - Thermal Stress Ratcheting Assessment. This section will evaluate the allowable limit on the secondary stress range from cyclic thermal loading. 

Plastic instability—Incremental collapse incremental collapse is cyclic strain accumulation or cumulative cyclic deformation. Cumulative damage leads to instability of vessel by plastic deformation. The primary plus secondary limits are intended to preclude any ratcheting and validate the use of elastic analysis. 

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