ELASTIC-PLASTIC ANALYSIS OF INTERNALLY PRESSURIZED TORISPHERICAL SHELLS

The constitutive equation for an. elastic-plastic material model was d erived using the von Mises yield criterion and assuming isotropic stra in hardening. A layered finite element permitting geometrically lineal and geometrically nonlinear elastic-plastic analysis of thin shell st ructures is presented. The effect of linear strain hardening on the si ze of plastic regions and the distribution of internal forces in an in ternally pressurized torispherical shell was analyzed. At sufficiently high pressures a significant difference in the distribution of intern al forces was observed between elastic, perfectly plastic and strain h ardening material. The effect of the size of plastic regions on the di fference in the magnitude of internal forces obtained by geometrically linear and geometrically nonlinear computations of the torispherical shell was studied. An increase in the size of the plastic region was f ound to produce greater differences in the computation of meridional b ending moments than in the computation of hoop stress resultants.