STUDY OF EFFECTS OF INELASTICITY ON BUCKLING OF CYLINDRICAL SHELL UNDER AXIAL LOAD

Abstract

This master thesis presents research into inelastic buckling of cylindrical shells under axial loads. This type of structure is found in aerospace application like planes, launch vehicles, rockets etc. However modeling of these is not discussed here. Here the study is to see effects of plasticity on buckling loads. The idea behind this research is that in experiments we can’t separate plasticity of a material but in FEA Software we can. A FE Module is developed such that it’s buckling load according to classical theory is higher than yield point. It is first analyzed with linear elastic material model and then linear elastic-nonlinear plastic, and results are compared to study effects of plasticity. Material module is developed by using nonlinear kinematic hardening equations for 2024 T3 alloy of aluminum at room temperature(250 C ). Data points for plotting graph are found by Matlab. To find inelastic critical buckling loads an iterative method related to reduced modulus theory is tried for three different shell thickness, though it was a failure. The results of analysis shows that there is an expected reduction of buckling load when plasticity is considered which in some cases could be about nine times of further reduction when imperfections are considered, so there is a need for a better theoretical model which would consider plasticity. The idea is maybe by studying inelastic load values we could get some insight on how to deal with theoretical equations or what kind of results should come.