Pressure Pipe Damage: Numerical Estimation of Point Load Effect

Abstract:

The most relevant loading conditions for real polymer pipe systems are not only internal pressure, but also loading caused by sand embedding including bending or different kinds of point loads. It has been shown that service lifetime of buried pipes can be reduced especially due to stress concentration caused by external point loads. If the pipe is loaded locally the stress is concentrated here and a crack can initiate at this position or the existing crack can be affected by corresponding stress redistribution. In the paper the effect of the hard indenter, Poissons ratio, hoop stress level and pipe wall thickness on the crack shape was estimated using numerical simulations of the creep crack propagation based on finite element method. Relation between crack length and crack width was found and expressed by simple relationship. A deeper understanding of the point load effect in order to prevent unexpected failure of the pipelines is of paramount importance for pipeline design.

• Periodical: Key Engineering Materials (Volumes 525-526)
• Pages: 177-180
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.525-526.177
• Online since: November 2012
• Authors: Michal Zouhar, Pavel Hutař, Martin Ševčík, Luboš Náhlík
• Keywords: Crack Shape Prediction, Point Load, Polymer Pressure Pipes, Stress Intensity Factor (SIF)

References

[1] Janson L.E., Plastic Pipes for Water Supply and Sewage Disposal, Borealis, Stockholm; (1999).

[2] Pinter, G., Haager, M., Lang, W.G., Influence of nonylphenol–polyglycol–ether environments on the results of the full notch creep test, Polymer Testing, Vol. 26, Issue 6, pp.700-710, (2007).

DOI: 10.1016/j.polymertesting.2007.01.010

[3] Farshad, M., Determination of the long-term hydrostatic strength of multilayer pipes, Polymer Testing, Vol. 24, Issue 8, pp.1041-1048, (2005).

DOI: 10.1016/j.polymertesting.2005.07.001

[4] X. Lu, N. Brown, A test for slow crack growth failure in polyethylene under a constant load, Polymer Testing, Vol. 11, Issue 4, pp.309-319, (1992).

DOI: 10.1016/0142-9418(92)90025-7

[5] Hutař, P., Ševčík, M., Náhlík, L., Pinter, G., Frank, A., Mitev, I., A numerical methodology for lifetime estimation of HDPE pressure pipes, Engineering Fracture Mechanics, Vol. 78, Issue 17, pp.3049-3058, (2011).

DOI: 10.1016/j.engfracmech.2011.09.001

[6] Watkins R.K., Anderson L. R., Structural Mechanics of Buried Pipes, CRC Press, Boca Raton, (2000).

[7] Hessel, J., Minimum service-life of buried polyethylene pipes without sand-embedding. 3R international 40, Special Plastic Pipes, pp.4-12, (2001).

[8] Schouwenaars R., et. al, Slow crack growth and failure induced by manufacturing defects in HDPE-tubes, Engineering Failure Analysis, vol. 14, pp.1124-1134, (2007).

DOI: 10.1016/j.engfailanal.2006.11.066

[9] Anderson, T. L. Fracture mechanics: fundamentals and applications. 2nd ed. London: CRC Press, (2000).

[10] Branco, R., Antunes, F.,V., Finite element modeling and analysis of crack shape evolution in mode-I fatigue Middle Cracked Tension specimens, Engineering Fracture Mechanics, 75, pp.3020-3037, (2008).

DOI: 10.1016/j.engfracmech.2007.12.012

[11] Blümich, A., et al.: Mobile NMR for Analysis of Polyethylene Pipes. Acta Physica Polonica A. Vol. 108, pp.13-23. (2005).

DOI: 10.12693/aphyspola.108.13