| The dynamic ductile fracture toughness of X70 and X80 pipeline materials was studied. Instrumentation of Charpy and Drop Weight Tear testers was conducted to examine the possibility of measuring propagation directly from a load-displacement trace. Tests conducted in this study showed that instrumentation that uses strain gauges for data acquisition result in energy measurement errors and therefore and alternative energy measurement technique which uses an optical encoder an linear tape was developed. This alternative technique shows promise. From the drop weight tear test load-displacement trace a region of steady state crack propagation can be measured for both the X70 and X80 materials, but side grooves must be added to Charpy specimens to induce steady state crack propagation. With the X80 material it was shown that a side groove depth of 1.0 mm does induce steady state crack propagation, but the X70 specimens require a groove depth greater than 1.5 mm, which was the maximum groove depth that could be used. Thus for the conditions tested, steady state crack propagation can be compared only between X80 Charpy and drop weight tear test specimens. |
