Issue 49

B. G. N. Muthanna et alii, Frattura ed Integrità Strutturale, 49 (2019) 463-477; DOI: 10.3221/IGF-ESIS.49.44 475 C ONCLUSION he presence of elbow in piping system leads to activate a locally stresses. For the studied pipe (internal radius R i = 298.45 mm, wall thickness t = 12.7 mm) and for internal pressure P = 7 MPa, stress amplification factor k t was found to be 1.2. The maximum stress was located at a curvature angle α=72°. This localized an eventual defect which is considered as a semi-0elliptical surface defect. This defect is submitted to mixed mode of loading due to longitudinal and circumferential pipe stress distribution and elbow and pipe curvature. The mixed mode consists of superposition of mode I, II and III. Therefore, an equivalent stress intensity factor was computed and a mixed mode failure criterion was used to determine critical semi elliptical crack orientation. The assessment of defects in elbow can be made with a modified Failure Assessment Diagram where the non-dimensional crack driving force refers to the equivalent stress intensity factor and the value of fracture toughness which take into account high constrain in elbow. Severe stress conditions of a defect in elbow locate its assessment point in the brittle part of the FAD. R EFERENCES [1] Meriem-Benziane, M., Abdul-Wahab, S.A., Benaicha, M. and Belhadri, M., 2012. Investigating the rheological properties of light crude oil and the characteristics of its emulsions in order to improve pipeline flow. Fuel, 95, pp.97-107. DOI: 10.1016/j.fuel.2011.10.007. [2] Meriem-Benziane, M. and Zahloul, H., 2013. Rheological Behaviors of Crude Oil in the Presence of Water. Int J Mech Aerospace Mech Eng, 7, pp.223-227, DOI: 10.5281/zenodo.1329577. [3] Testa, G., Bonora, N., Gentile, D., Ruggiero, A., Iannitti, G., Carlucci, A., Madi, Y., (2017), Strain capacity assessment of API X65 steel using damage mechanics, Frattura ed Integrità Strutturale, 42 (2017) 315-327. DOI: 10.3221/IGF-ESIS.42.33. [4] Larrosa, N.O., Ainsworth, R.A., (2016), Ductile fracture modelling and J-Q fracture mechanics: a constraint based fracture assessment approach, Frattura ed Integrità Strutturale, 10(38), pp. 266-272, DOI: 10.3221/IGF-ESIS.38.36. [5] Ouardi, A., Majid, F., Mouhib, N., Elghorba, M., (2018), Residual life prediction of defected Polypropylene Random copolymer pipes (PPR), Frattura ed Integrità Strutturale, 43, pp. 97-105, DOI: 10.3221/IGF-ESIS.43.07. [6] Vazouras, P., Karamanos, SA., (2017), Structural behavior of buried pipe bends and their effect on pipeline response in fault crossing areas, Bull Earthq Eng, DOI: 10.1007/s10518-017-0148-0. [7] Karamanos, SA., (2016), Mechanical behavior of steel pipe bends: an overview, J Press Vessel Technol 138, 41203, DOI: 10.1115/1.4031940. [8] Soudani, M., Bouledroua, O., Hadj Meliani, M., El-miloudi, K., Muthanna, B.G.N., Khelil, A., Elhoud, A., Matvienko, Y.G. and Pluvinage, G., (2018). Corrosion inspection and recommendation on the internal wall degradation caused rupture of 6” gas line pipe. Journal of Bio-and Tribo-Corrosion, 4(2), p.28, DOI: 10.1007/s40735-018-0145-0. [9] Hadj Meliani, M., Bouledroua, O., Azari, Z., Sorour, A., Merah, N. and Pluvinage, G., (2017). The inspections, standards and repairing methods for pipeline with composite: a review and case study. In International Conference on New Trends in Fatigue and Fracture (pp. 147-156). Springer, Cham, DOI: 10.1007/978-3-319-70365-7_17. [10] Meriem Meriem-Benziane, M., Bou-Saïd, B. and Boudouani, N., (2017). The effect of crude oil in the pipeline corrosion by the naphthenic acid and the sulfur: A numerical approach. Journal of Petroleum Science and Engineering, 158, pp.672-679. DOI: 10.1016/j.petrol.2017.08.073. [11] Soudani, M., Hadj Meliani, M., El-Miloudi, K., Bouledroua, O., Fares, C., Benghalia, M.A., Azari, Z., Capelle, J., Sorour, A.A. and Pluvinage, G., (2018). Efficiency of green inhibitors against hydrogen embrittlement on mechanical properties of pipe steel API 5L X52 in hydrochloric acid medium. Journal of Bio-and Tribo-Corrosion, 4(3), p.36. DOI: 10.1007/s40735-018-0153-0. [12] Liu, J.G., Bakedashi, W., Li, Z., Xu, Y.Z., Ji, W.R., Zhang, C., Cui, G., Zhang, R.Y., (2017), Effect of flow velocity on erosion–corrosion of 90- degree horizontal elbow, Wear DOI: 10.1016/j.wear.2016.11.015 . [13] Zeng, L., Shuang, S., Guo, X.P., Zhang, G.A., (2016), Erosion-corrosion of stainless steel at different locations of a 90◦ elbow, Corros. Sci. 111, pp. 72, DOI: 10.1016/j.corsci.2016.05.004. [14] Borruto, A., Narducci, G., Pietrosanti, P., (2012), Analysis of the causes of failure in 5Cr-1Mo pipes mounted in a preheating furnace, Frattura ed Integrità Strutturale, 20, pp. 22-31, DOI: 10.3221/IGF-ESIS.20.03. [15] Amara, M., Muthanna, B.G.N., Abbes, M.T. and Hadj Meliani, M., 2018. Effect of sand particles on the Erosion- corrosion for a different locations of carbon steel pipe elbow. Procedia Structural Integrity, 13, pp. 2137-2142, T