Buckle Propagation in Steel Pipes of Ultra-high Strength: Experiments, Theories and Numerical Simulations

In this paper, experimental, theoretical and numerical approaches were employed to scrutinize the buckle propagation events occurring in pipes subjected to external pressure. Two groups of samples with different radius-to-thickness ratios were fabricated using steel pipes of ultra-high strength and were subjected to compression of external pressure in a sealed pressure vessel specially designed and customized for the experiment. Experimental results were recorded through a data acquisition system. For facilitating the theoretical calculations, uniaxial tensile tests were performed on tensile pieces cut from the same pipes to obtain the material properties. It was found from the experimental results that once a buckle is initiated in a pipe, the external pressure dropped to a specific value called buckle propagation pressure and kept at this level until the whole pipe is flattened into a dog-bone shape. Based on the measured material properties and geometric parameters, theoretical solutions were computed using established ring models and shell model, and finite element predictions were also obtained from ABAQUS software. The efficiency and accuracy of the shell model and finite element model were expounded by comparing various theoretical solutions and numerical predictions with the experimental results. With the authenticated shell model and finite element model, a deep insight into the phenomenon of buckle propagation of pressurized long pipes was provided by performing a series of parametric study.