Fem analysis of pressure vessel with an investigation of crack growth on cylindrical surface

During the exploitation, pressure vessels are subjected to different load types (static, dynamic, thermal, etc.), and their failures usually occur in areas of geometrical discontinuity. The most common geometrical discontinuities are nozzles positioned on the cylindrical shell of the pressure vessel. The previous researches in the field [6, 15, 16] focused on this problem: stress and strain fields on pressure vessels with one nozzle were analysed, using analytical and numerical calculations, as well as experimental methods. Nozzles are usually positioned on cylindrical shells at angle bigger or less than 90o relative to longitudinal axis of the vessel [14, 19]. Each nozzle has its constructive characteristics, as well as specific effect on cylindrical shell strength. The aim of the research was to analyse the influence of the dimensions and positions of the two nozzles on the strain distribution on the vessel cylindrical shell subjected to internal pressure, and then to use obtained distributions for initial crack position prediction and consequent damage analysis. In general, damage to pressure vessels can be thought of as occurring in two stages: crack initiation and crack propagation. However, in conducting damage analyses on pressure vessel, it is often conservative to ignore the crack initiation process, assume that the component already contains a pre-existing crack or defect, and use the analysis technique to estimate the in-service extension of the defect [3, 12]. Hypothesizing the existence of an initial crack or defect seems especially appropriate for the case of large welded structures since the welds may contain defects (lack of fusion, voids, inclusions, etc.). Martina BAlAc Aleksandar GrBovic Aleksandar Petrovic vladimir PoPovic