Papers by Author: G. Pluvinage

Abstract: The objective of this study is examining the level of degradation caused by the welding process, the influence of defects by third parties and the speed of loading on the integrity of the pipeline. The use of Charpy instrumented pendulium coupled with the the volumetric method analysis allowed us to calculate the dynamic fracture toughness of the API 5L X52 pipeline steel in presence of a real defect characterized by its notch radius but also, to show the need for a second parameter to overcome the problem of fracture toughness transferability.

Abstract: The purpose of this work is to assess a gouge defect in a pipe submitted to internal pressure. To do that a method is used which is based upon a failure assessment diagram and, more precisely, upon a Modified Notch Failure Assessment Diagram (NMFAD) which has been proposed as a mesofracture approach. The safety factor has been determined under conservative conditions; i.e for a X52 pipe steel having a relatively low fracture toughness and a severe gouge defect with high aspect ratio and high constraint. In addition, a mesofracture approach to the fracture toughness transferability problem has been proposed. The crack (K-T) methodology has been modifed to create the ( –Teff) two-parameter fracture resistance criterion.

Abstract: The use of two parameters fracture mechanics criterion as a tool for structural design and analysis has increased significantly in recent years. First, we discuse the elastic solution for the stress distribution at crack tip for two dimensional geometries and particularly constraint as T-stress under various loading conditions. Secondly, using notch fracture mechanics and particularly the Volumetric Method approach, we study the stress distribution at the tip of a notch in pipes submitted to internal pressure. The Notch Stress Intensity Factor Kρ and the effective T-stress are combined into a two-parameter fracture criterion (KIρ-Tef). This approach is then used to quantify the constraint of notch-tip fields for various pipe geometry and loading conditions.

Abstract: Problems for load carrying elements reside mainly in buckling, embrittlement and corrosion. These problems can be mainly solved by introduction of composite materials of a sandwich type. These materials ally lightness, rigidity and resistance to the corrosion. For the design of a large number of applications, static and cyclic properties are necessary. In this paper, first static and fatigue tests on four points bending of four types sandwich panels have been performed. Load/displacement and S-N fatigue curves are presented and analysed. Fatigue failure and damage modes are observed with an electronic microscope and are discussed. Numerical simulation applied to the static tests is compared to the experimental results. The second is to address such fatigue behaviour by using a damage model and check it by experimentation. This fatigue damage model is based on stiffness degradation, which is used as a damage indicator. Four non-linear cumulative damage models derived from the chosen stiffness degradation equation are examined with assumption of linear Miner’s damage summation. Predicted results are compared with available experimental data.