TIME DEPENDENT CRACK GROWTH IN POLYETHYLENE: CHARACTERIZING THE K VS. da/dt DEPENDENCE AND THE EFFECTS OF IGEPAL

摘要

Testing of newly developed pipe is both time consuming and costly. Hydrostatic creep-rupture tests that measure hoop stress vs. time to failure can be used to rank systems and predict service lifetimes. This paper presents a fracture mechanics approach to ranking polymers and predicting lifetimes for long-term, slow crack-growth rate failures. Constant load three point bend tests have been performed on notched specimens to produce displacement vs. time data and calculate stress intensity (K_1) vs. crack growth rate (da/dt) relationships. Very good repeatability has been demonstrated and da/dt has been found to be a unique function of K_1 independent of the combination of load and crack length used to obtain it.