Does your WRC297 report indicate that the proimary stress failure is in the nozzle or in the shell to which it is attached? Typically, a CAESAR II report would not list shell stress.
If it is the nozzle, are you sure the cause is hoop stress? Perhaps it is the calculated thrust load due to pressure. Such a thrust load, too, would not typically be included in the CAESAR II analysis.
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Dave Diehl