A method for mechanical property assessment across butt fusion welded polyethylene pipes
- 15 Downloads
The use of high-density polyethylene pipes in gas and water distribution networks is steadily growing worldwide. If the resistance of plain pipes is at present time well established using appropriately designed standards, welding issues continue to be globally approached equally in terms of structure and mechanical properties. Consequently, further practical investigations should be aimed at studying mechanical properties in the weld region which includes the melt zone and its heat-affected zones. This work presents a method based on removing layers in order to assess localized variances in mechanical properties throughout the weld seam in both radial and circumferential directions. An experimental plan based on specific machining operations allowed testing 39 standard specimens representing the weld volume matter in three concentric layers for given pipe dimensions and their counterpart standard unwelded ones. The typical stress–strain behavior of semi-crystalline materials is preserved in welded and unwelded specimens but with different characteristic limits. At the weld inner layers, properties such as elastic modulus, yield, and failure stresses displayed lower values, whereas in welded outer layers, the tendency is inversed. The cold drawing extend remained approximately steady for unwelded and welded cases across the pipe wall. This property is less affected by the presence of the weld as it described a constant material flow which is mostly a function of available material quantity for yielding. The approach developed in this study gives consistent indications on welding quality around the pipe weld and across the thickness. Accordingly, outermost and innermost welded layers may exhibit lower or even bad-quality welds as imperfections can concentrate stresses at the joint interface because of cold weld problems. Such method enabled detecting 23% of failures at the weld seam from outer and inner layers while the middle layer did not reveal any failure at the weld. The causes of this behavior are approached using crystallinity evolution in welded and unwelded pipes.
KeywordsHDPE pipe Butt fusion welding Mechanical properties Radial direction Circumferential direction Structural variances
Unable to display preview. Download preview PDF.
The authors would like to express their gratitude to those who provided assistance to this research work: SARL Z.A.—Annaba (Water Construction Network Co.), Mechanical Eng. Dept. (Hall Technologique) of Guelma University (8 May 1945 U.), R&D Dept., POLYMED Co., Skikda, Unité de Recherche Matériaux, Procédés et Environnement (URMPE) of Boumerdes University (UMBB). Fruitful discussions with members of LR3MI of UBM Annaba are also greatly appreciated. Part of this work was supported by Algerian Ministry of Higher Education & Scientific Research, CNEPRU Research Project “Study of thermo-mechanical behavior of butt welded joints in HDPE pipes,” Project Code A11N01UN23012014122 (2014).
- 2.Yu K, Morozov EV, Ashraf MA, Shankar K (2017) A review of the design and analysis of reinforced thermoplastic pipes for offshore applications. J Reinf Plast Compos. https://doi.org/10.1177/0731684417713666
- 3.Deblieck RAC, van Beek DJM, McCarthy M, Mindermann P, Remerie K, Langer B, Grellmann W (2017) A simple intrinsic measure for rapid crack propagation in bimodal polyethylene pipe grades validated by elastic–plastic fracture mechanics analysis of data from instrumented Charpy impact test. Polym Eng Sci 57:13–21. https://doi.org/10.1002/pen.24380 CrossRefGoogle Scholar
- 6.van der Stok EJW, Scholten FL (2016) Determining the residual quality of PE pipes using the strain hardening test. Proc. of the 18th plastic pipes Conf. PPXVIII, September 12–14, 2016, Berlin, 10p. https://doi.org/10.1134/S0021894417020183
- 17.Pokharel P, Kim Y, Choi S (2016) Microstructure and mechanical properties of the butt joint in high density polyethylene pipe. Int J Polym Sci, Art. ID 6483295. https://doi.org/10.1155/2016/6483295. 13p
- 18.Jagtap TU, Mandave HA (2015) Machining of plastics: a review. Int J Eng Res Gen Sci 3((2) (Part 2)):577–581Google Scholar
- 20.Rehab-Bekkouche S, Ghabeche W, Kaddeche M, Kiass N, Chaoui K (2009) Mechanical behaviour of machined polyethylene filaments subjected to aggressive chemical environments. Mechanika (MECHANICS) 77(3):40–46Google Scholar
- 23.Ghabeche W, Alimi L, Chaoui K (2015) Degradation of plastic pipe surfaces in contact with an aggressive acidic environment. 30. Int. Conf. Technol. & Mater. for Renew. Energy, Envir. & Sustainability. Energy Procedia 74:351–364. https://doi.org/10.1016/j.egypro.2015.07.625
- 27.Hehn O (2006) Analyse expérimentale et simulation thermomécanique du soudage bout à bout de tubes de polyéthylène. PhD Thesis, Ecole des Mines de Paris, 20pGoogle Scholar
- 30.BS ISO 4427–2 2007 British standard, Plastic piping system—polyethylene (PE) pipes and fittings for water supply—part 2: pipes; www.spic.ir
- 31.ASTM Standard D 638–02a 2002 Standard test method for tensile properties of plastics (metric), Annual Book of ASTM StandardsGoogle Scholar
- 32.http://www.groupe-chiali.com/images/documentations/manuels_de_pose/man_bout_à_bout. Accessed Sept. 10 2017
- 33.ISO 12176–3 (2003) Plastics pipes and fittings—equipment for fusion jointing polyethylene systems—part 1: Butt fusionGoogle Scholar
- 37.Niou S, Azzouz S, Chaoui K, Azari Z (2016) Développement d’une méthode pour caractériser la résistance mécanique circonférentielle d’un joint de tube plastique soudé bout-à-bout, 10èmes Journées de Mécanique (JM’10, EMP), Ecole Militaire Polytechnique, 12-13 April, Algiers, 1–5Google Scholar
- 41.El-Bagory TMAA, Younan MYA, Sallam HEM (2013) Mechanical behavior of welded and un-welded polyethylene pipe materials, K-PVP Conference, Proc. of the ASME, Pressure Vessel & Piping Division, Paper # 2013–97743, Paris, (14–18/07/13)Google Scholar
- 45.Qi F, Huo L, Zhang Y, Jing H (2004) Study on fracture properties of high-density polyethylene (HDPE) pipe. Key Eng Mater 261-263:153–158. https://doi.org/10.4028/www.scientific.net/KEM.261-263.153 CrossRefGoogle Scholar