Slow crack growth behaviour and failure mechanisms of PE 100 pipe grade materials exposed to liquid hydrocarbon environment
Sprache des Vortragstitels:
Advances in Polymer Science and Technology 3
Sprache des Tagungstitel:
Introduction and Experimental
Due to the growing utilization of PE pipes in the oil and gas industry, it essential to evaluate liquid hydrocarbon environment related changes, particularly on slow crack growth (SCG) behavior. Thus, fatigue crack growth (FCG) tests, using cracked round bar (CRB) specimen under cyclic loading, have been carried out with three commercially available PE100 pipe grades. Specimen have been tested fully immersed in media and tempered at 35 °C and 60 °C, respectively, in either deionized water (?water application?) or a mixture of 90w-% i-octane/ 10w-% toluene (?oilfield application?). Prior to testing, ?oilfield application? samples have been preconditioned in media at the designated testing temperature until mass constancy.
Results and Conclusions:
FCG tests revealed different failure mechanisms for water and oilfield environments. As expected for water and similar to investigations in air, the typical failure mechanism was crack tip crazing visible as remnant of fibrils and micro-voids. In sharp contrast to liquid hydrocarbon environment, no micro-voids and fibrilar structures could be observed on the fracture surfaces, suggesting that the dominant crack tip failure mechanism is cyclic shear yielding. Interestingly, at very low initial stress intensity factors (SIF), the resistance to SCG of liquid hydrocarbon saturated samples remained even better than for tests in water.
 Haager M, Institute of materials science and testing of plastics, University of Leoben, 2006