Vers une contribution de la sûreté de fonctionnement des équipements pétroliers en Algérie.

Abstract

The work presented concerns the experimental and numerical modeling of the pipeline assembly process by SMAW electric arc welding. The study was conducted on an API5L X70 steel type material. The purpose of the experimental modeling was obtaining statistical models of the objective functions evolution as influencing factors function. The large number of factors which intervene during the welding process with the electric arc SMAW as well as the complexity of the physical phenomena occurring during the interaction during this process, led us to appeal to the experimental designs. This method allowed reducing the number of tests while having a good resolution of the obtained results. By using the design of experiments method on the one hand to estimate the effects of the operating parameters (welding speed, voltage, intensity and the electrode diameter) and their interactions on several functions characterizing the morphology of the weld bead (the height of the deposit of material H, width of the bead facing towards L1 and the width in the middle of the bead (lateral penetration) L2), and on the 112 other hand to provide a mathematical model which links the operating parameters of welding to the objective studied functions. The numerical modeling part aims is to complete the information acquired through experimental modeling with information on the evolution of physical phenomena during the SMAW welding interaction. The aim is to simulate heat transfer phenomena using the equivalent heat source approach, and to develop a direct model using the finite element software COMSOL Multiphysics. The so-called “equivalent source” approach, which consists of solving a nonlinear conduction problem in the parts to be assembled. In this case, an analytical form of the source representing the distribution of the heat input by the SMAW welding process could be given. The numerical model proposed was validated by a comparison between several dimensional quantities which characterize the shape of the experimental melted zone with the shape of the calculated melted zone. In order to validate the numerical model developed, the method of numerical designs is used to estimate the effects of the numerical model parameters through the heat sources parameters (radius of the upper surface source, radius of the lower surface source, radius face location of the volume source and the conductivity) and their interactions on several functions characterizing the morphology of the digital weld pool (width of the molten zone on the lower side Linf, width in the middle of the bead Lm, width of the molten zone on the upper side Lsup and the height of deposit H). This optimization gave a good correlation of the molten pool shape of the developed model and the experimental one (macrography)