by Kyros P. Andreadakis
Diploma Thesis, July 2004
The present work examines the response of tubular members (D/t£50) subjected to lateral (transverse) quasi-static loading, imposed by wedge-shaped indenters, in the presence of internal pressure. In the first part of the work, tubes are modelled with shell finite elements, accounting for geometric and material nonlinearities, and the numerical results are in good agreement with pipe indentation test data from internally pressurized pipes. Using the finite element tools, a parametric study is conducted and load-deflection curves are obtained for different levels of pressure, for various wedge shapes and for different types of boundary conditions. It is found that the presence of internal pressure increases significantly the indentation force. The effects of yield anisotropy on the indentation resistance are examined, and deformed shapes of tubes for different pressure levels are depicted and discussed. A simplified three-dimensional analytical model is also developed, which yields closed-form expressions for the indentation force and the corresponding indentation length. The model was introduced elsewhere for non-pressurized tubes and, herein, it is enhanced to include the effects of pressure, accounting for different types of tube end conditions. The analytical solution is in fairly good agreement with the finite element results, and illustrates tube indentation response in a clear and elegant manner.