The effect of residual stress on polymer pipe lifetime

This paper presents a quick methodology to assess the lifetime of an internally and externally pressurized polymer pipe using linear elastic fracture mechanics. The non-homogenous distribution of residual stress induced by production technology is incorporated into the numerical model of the cracked pipe. The stress intensity factor of the axially oriented crack growing from the inner surface through the pipe wall is estimated and combined with experimentally determined creep crack growth kinetics used for lifetime assessment. Major parameters affecting the pipe’s lifetime are identified and discussed. A simplified equation for estimation of the stress intensity factor value, removing the need for complicated finite element simulation, is then proposed. The combination of the creep crack growth tests and the approach presented can be a very powerful tool for reliable lifetime estimation of plastic pipes.