Original article Finite element analysis of an elbow tube in concrete anchor used in water supply networks Sorin Vlase 1 , Daniel Scarla ˘tescu 1 , Marin Marin 2 and Andreas O ¨ chsner 3 Abstract This paper aims to analyze the stress and strain states appearing in the elbow of a tube, such as those commonly used in a city’s water supply network. The stress field is characterized by the fact that there is a significant stress increase when compared to a straight tube. As a result, the strength of such an elbow must be investigated and guaranteed for such a network to be well designed. A practical solution used is to anchor the elbow in a massive concrete block. The paper compares the stress field that occurs in the elbow when it is free, buried in the ground, and when it is anchored in a massive concrete block. Furthermore, we investigate how a crack appears and propagates in the elbow. This happens especially for the elbow buried in the ground where the stress and strain are higher than when the elbow is anchored in concrete. The results obtained can be used in the current practice in the case of water supply networks made by high- density polyethylene pipes. Keywords Finite element method, elbow tube, concrete anchor block, water supply networks Date received: 27 February 2019; accepted: 2 August 2019 Introduction The use of tubes is widespread in the transport of liquids, especially for the transport of oil, gas, and water for human communities. Concerning the water supply in the second half of the 20th century, technological development has allowed the emergence and production of plastic materials that have become the predominant materials for tubes used in water supply systems. These modern tubes can be used in water supply networks, resulting in structures that meet all the requirements imposed on such supply networks. The most suitable plastic currently used to produce the tubes needed to transport water in modern water supply networks has been shown to be high-density polyethylene (HDPE). 1–3 Tubes and fittings obtained are characterized by a long service life and reduced maintenance costs. These tubes have many advantages when compared to the conventional ones made of steel. HDPE tubes are already in their third generation. 2,4 These tubes have proven to have very good behav- ior in terms of strength and complex loading bearing ability as they are continuously subjected to variable loads in a water supply network that has to work uninterruptedly. A problem that occurs is the severe damage in the form of ductile or breakable mode, partly due to the placement of these tubes. For the ductile breaking mode, the appearance is in the form of a parrot beak 2,6–10 and this is the main focus of this paper (see Figure 1). The finite element method (FEM), in this case, allows for an accurate and low cost evaluation of prob- lems related to this type of breaking. 3,11–15 In the pre- sent research, it is necessary to use solid elements to adequately generate a computational model. It is thus possible to quickly obtain information on the stress and strain states in the structure. The breaking of buried tubes made of HDPE may occur due to several conditions that can be grouped as follows: . Internal conditions (high pressure, variable pres- sure, temperature of the fluid); 1 Department of Mechanical Engineering, Transylvania University of Brasov, Romania 2 Department of Mathematics and Computer Science, Transylvania University of Brasov, Brasov, Romania 3 Faculty of Mechanical Engineering, Esslingen University of Applied Sciences, Esslingen, Germany Corresponding author: Andreas O ¨ chsner, Faculty of Mechanical Engineering, Esslingen University of Applied Sciences, Esslingen, Germany. Email: andreas.oechsner@gmail.com Proc IMechE Part L: J Materials: Design and Applications 0(0) 1–9 ! IMechE 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1464420719871690 journals.sagepub.com/home/pil