Experimental and Numerical Determination of Critical Buckling Pressure of thin Cylindrical Shells Subjected To External Pressure

Abstract

Thin shell structures have very high load bearing capacity, hence find wide applications in the field of mechanical engineering, structural engineering, sea shore structures, aerospace industries and nuclear engineering structures. The major failure of thin shell structures is buckling. Oil carrying pipelines, hull structures, oil tankers are few examples in which thin cylindrical shell structures fails by buckling under external pressure loading. In order to avoid the buckling failure, prediction of critical buckling pressure is important in thin shell structures under external pressure. But this critical buckling pressure depends on boundary conditions, imperfections, thickness variation of shells etc. To estimate the effects of these parameters on Critical Buckling Pressure (CBP) require a reliable experimental test rig. Hence in our proposed work, efforts are taken to develop a simple cost-effective reliable test rig to determine the effects of these parameter variations on the critical buckling pressure. For developing the test rig two important components to be designed properly namely, external cover cylinder and online pressure measurement system. The external cover cylinder with lid which contains test cylindrical shell inside should be designed in such a way that it should be leak proof and rigid so as to withstand the internal working pressure with negligible deformations. Hence, a ring and stinger stiffened cylindrical shell is taken as external cylindrical shell. The pressure variation in the test rig should be recorded online so as to predict the critical buckling pressure accurately. Hence, PC interfaced microcontroller-based pressure measurement system is developed in our proposed work. The test cylinder considered for this work is made of mild steel of size diameter 456 mm, length 456 mm and thickness 1 mm. The classical (simply supported) boundary conditions are assumed and simulated on both sides of the test cylinders. The experimental critical buckling pressures are compared with the FE results and both the results have good agreement.