A study of fracture mechanisms when exposed to hydrostatic loads

Abstract

Bridgman experiment is an experiment that was conducted by Bridgman in 1912. This simple experiment consists of a rod going all the way through a pressure vessel. When pressurizing the vessel, the rod is loaded on the curved surface and when pressure get high enough, the rod fractures. There are still disagreement on the reason for fracture. Two explanations tend to stand against each other. One side explaining the fracture with use of the effective tension theory and the other side with use of Von Mises criterion and Poisson ratio. With examples from calculation of buoyancy, the two sides are explained and understood. Both sides with experiments differentiating them and their arguments. Then the theory on effective tension is elaborated by super positioning and explained. During the thesis, experiments were conducted. Bridgman experiment, bending experiment and tension experiment. All rods were cut down in size and photographed in SEM (Scanning Electron Microscope) to have a closer look at the fracture surfaces. It was shown that the fracture surface from Bridgman experiment is a fracture surface of tension. Results were discussed with several experts and feedback from both sides were discussed. Further investigations in three different softwares, AutoCAD Inventor, OpenFOAM and Ansys. Neither of the softwares show axial tension in the rods during pressure loading. Experts on the softwares were contacted and defended their software.