Numerical modelling and experimental validation of elastic - plastic behaviour of pressure vessel with nozzles

Abstract

To evaluate the safety of welded structures, such as pressure vessels, it is necessary to know the material properties of which vessels are made and their behavior under different working conditions. Due to various requirements, nozzles are often welded on vessel’s shell. Stress and strain analysis of the influence of two nozzles closely welded on the pressure vessel cylindrical shell, subjected to internal pressure, is presented in this paper. For analysing full field of surface strain, 3D Digital Image Correlation (DIC) method was applied. DICM with camera system in combination with Aramis software is a non-contact and material independent measuring system providing high resolution, and highly accurate information about a component's 3D shape, strain and deformation. After determination of critical areas (strain concentration areas) by experimental method, the numerical analysis of the equivalent 3D model was performed. 3D model vessel which includes material nonlinear properties of vessel was obtained by finite element analysis. Maximal stress and strain values were determined and results were comparable with experimental results. The aim of this study is to show behaviour of cylindrical pressure vessel with two nozzles subjected to internal pressure, using both 3D DIC method and numerical method. Maximum values of stress and strains, as well as their positions are shown in the paper. Differences between these two methods in the area of the highest strain values were from 2.99% to 17.8%.