On the Use of the First Order Shear Deformation Models of Beams, Plates and Shells in Creep Lifetime Estimations

Abstract

Numerical creep-damage life-time predictions of thinwalled structures are discussed with respect to the cross section assumptions used in engineering models of beams, plates and shells. The first part of the paper is devoted to the comparative numerical study of a pipe bend based on shell and solid type finite elements available in the ANSYS code. The second part demonstrates the possibilities and limitations of the first order shear deformation beam theory in connection with creep damage analysis. The results show that the beam and shell models provide a satisfactory accuracy of time dependent deformation and stress solutions for the von Mises stress controlled creep response. The dependence of the creep strain rate on the kind of the stress state induced by the damage evolution requires to refine through-the-thickness approximations of displacement and stress fields used in the first order shear deformation engineering models. The errors of the creep solution with the shell or beam model result in the underestimation of displacements and the wrong edge zone stress redistributions.