Fracture
Plastic Pipes Conference Association # 1995 Edinburgh
Grigory, Kim, Kanninen, O'Donoghue, Mamo
The perceived need to ensure that polyethylene gas distribution pipes are safe from the possibility of long running catastrophic cracks has prompted a significant level of research recently. This paper brings to a completion an ongoing effort by the authors and their colleagues over the last few years. The basic premise to precluding rapid crack propagation is that the material fracture toughness must always be greater than the maxi-mum available driving force. A unique approach to determine the fracture toughness of the pipeline material has been developed using an instrumented version ofthe small scale steady state test. The dynamic fracture toughness is then evaluated from finite element analyses of these tests. As routine evaluation of the m-um crack driving force is a non-trivial task for a utility engineer, a relatively simple empirical form has been established in terms of the line pressure, diameter and SDR. Thus, the driving force can be calculated for a given set of pipeline design conditions and this can be compared with the fracture toughnesses for available pipeline materials. Illustrative examples are presented to demonstrate how this methodology can be used beneficially by the gas industry.
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