PSI - Issue 43

Lukáš Trávníček et al. / Procedia Structural Integrity 43 (2023) 148 – 153 Author name / Structural Integrity Procedia 00 (2022) 000 – 000

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is substituted by the ductile fracture very early in the crack growth process, or the slow crack growth does not occur at all. The higher constraint in the CRB specimens, which is caused by their shape of a full cylinder, allows for an early initiation of the SCG process and provides a sufficient space for the crack propagation, which results in the ability of these specimens to catch finer differences between the materials. The comparison of the pipe specimens with the CRB tests confirms this conclusion.

Fig. 6. Comparison of resistance against SCG for CRB and pipe specimens.

The original motivation for experimenting with the extruded pipe specimens was to save time. However, it turned out that the time saved by the very fast specimen preparation is consumed by the much longer testing times of the pipe specimens. Some modifications of the specimens are possible to try reducing the testing times and obtain more accurate results – increasing the pipe wall thickness t of the specimens and precisely determining the optimal testing load, especially for the more SCG-resistant PE grades. These modifications are planned for the upcoming work in this field. Acknowledgements This research was supported by the project TN01000071 of National Competence Centre of Mechatronics and Smart Technologies for Mechanical Engineering cofounded by the Technology Agency of the Czech Republic. References Arbeiter, F., Schrittesser, B., Frank, A., Berer, M., Pinter, G., 2015. Cyclic tests on cracked round bars as a quick tool to assess the long-term behaviour of thermoplastics and elastomers. Polymer Testing 45, 83 – 92. Beech, S., Clutton, E., 2013. Interpretation of results of full notch creep test and comparison with notched pipe test. Plastics, Rubber and Composites 34(7), 294-300. Fleissner, M., 1998. Experience with a full notch creep test in determining the stress crack performance of polyethylene. Polymer Engineering and Science (2), 330-341. Frank, A., Arbeiter, A., Berger, I., Hutař, P., Náhlík, L., Pinter, G., 2019. Fracture Mechanics Lifetime Prediction of Polye thylene Pipes. Journal of Pipeline Systems Engineering and Practice 10(1). Frank, A., Pinter, G., 2014. Evaluation of the applicability of the cracked round bar test as standardized PE-pipe ranking tool. Polymer Testing 33, 161-171. ISO. 2015. Polyethylene (PE) materials for piping systems – Determination of resistance to slow crack growth under cyclic loading – Cracked Round Bar test method. ISO 18489. ISO. 2012. Plastics piping and ducting systems: Determination of the long-term hydrostatic strength of thermoplastics materials in pipe form by extrapolation. ISO 9080. Lu, X., Brown, N., 1992. A test for slow crack growth failure in polyethylene under a constant load. Polymer Testing 11(4), 309-319. Nayyar, M., King, S., 2000. Piping handbook. 7th edition. New York: McGrawHill. ISBN 0-07-047106-1. Pinter, G., Haager, M., Balika, W., Lang, R. W., 2013. Fatigue crack growth in PE-HD pipe grades. Plastics, Rubber and Composites 34(1), 25-33. Pinter, G., Haager, M., Balika, W., Lang, R. W., 2007. Cyclic crack growth tests with CRB specimens for the evaluation of the long-term performance of PE pipe grades. Polymer Testing 26(2), 180 – 188.