Elastic Stability of Circular Tubes of Circumferentially Variable Thickness Under External Pressure

The effect of circumferential variation in wall thickness on the elastic stability of long, thin-walled, circular tubes under external pressure is investigated both theoretically and experimentally. The theoretical critical pressure for instability is deduced from an extension of Levy’s classical stability analysis. Experimental values of critical pressure are reported for tubes with flats milled on the outside surface. Both numerical and experimental results indicate a transition from symmetric to asymmetric deformation at instability as the minimum wall thickness decreases.