THE INITIATION AND PROPAGATION OF A LOCALIZED INSTABILITY IN AN INFLATED ELASTIC TUBE

A thin elastic tube, when inflated, first expands to a cylindrical shape. After some deformation, this is interrupted by the development of a bulge somewhere along the length of the tube. For some rubber materials, the bulge initially grows with decreasing pressure, whereas the rest of the tube unloads. After growing to a certain diameter, the bulge starts spreading axially. This can occur at a well defined value of pressure which is much lower than the pressure required to initiate the bulge. The mechanisms through which the bulge is initiated, its initial growth and its eventual propagation along the length of the tube are studied experimentally and analytically. The results vividly illustrate localization and propagation types of instabilities which govern the mechanical behavior of a variety of solids and structures.