(65r) Does Pipe Size Affect Slow Crack Growth Resistance?

The objective of this research was to investigate the effect of pipe geometry and stress intensity on slow crack growth (SCG) failure time of polyethylene (PE) pressure pipe. PE pressure pipe has an outstanding service record over the last 50 years. As PE is increasingly utilized to extrude larger diameter pipes, the stress intensity effect becomes critical. At the same design stress, the stress intensity increases with pipe size, especially for a scratched pipe. Although it is known that increased stress intensity will accelerate the SCG failure process, little work has been done to investigate the effect of pipe size on SCG resistance. In this research study, samples with different thicknesses and notch depths were tested under various stresses in order to create a model for failure time based on overall stress intensity. Preliminary data shows that stress intensity significantly decreases SCG failure time. More specifically the failure time decreases by up to 5.6 times for a hypothetical 36 inch pipe when compared to a 4 inch pipe. This model can be used to estimate the expected lifetime of various size pipes against SCG failure.