On the shakedown analysis of nozzles using elasto-plastic FEA

The performed shakedown calculations of a dished end with a nozzle in the knuckle region with varying internal pressure load, and two cylinder-cylinder intersections with constant moment load and varying internal pressure load are example cases for the application of the check against progressive plastic deformation as stated in the new European UFPV standard, Annex 5.B: "Direct route for design by analysis" (DBA). To calculate the shakedown limits, Melan's (lower bound) shakedown theorem is used. In this context, the usage of the deviatoric maps of stress states to obtain proper self-equilibrating stress fields is shown. Furthermore, some problems and corresponding possible solutions for performing the shakedown check using a finite element model with shell elements are stated and shown in the examples. (C) 1999 Elsevier Science Ltd. All rights reserved.