Papers by Author: Mohammed Hadj Meliani

Abstract: A failure criterion is proposed for ductile fracture in U-notched components under mixed mode static loading. The Compact Tension Shear (CTS) is the preferred test specimen used to determine stress intensity factor in the mode I, mode II and the mixed-mode fracture. In this work, the mode I and mode II stress intensity factors were computed for different notch ratio lengths 0.1<a/W<0.7, of the inner radius of notch 0.25mm<ρ<4mm and load orientation angles 0°<α< 90° using finite element analysis. However, a review of numerical analysis results reveals that the conventional fracture criteria with only stress intensity factors (NSIFs) Kρ first term of Williams’s solution provide different description of stress field around notch zone comparing with results introduce the second and third parameter T-stress and A₃.

Abstract: In the present work, an experimental study of the influence of tribological parameters upon the mechanical wear behavior of unalloyed and high-alloy steels is proposed, in order to monitor the residual stress evolution as a function of the friction coefficient. For both types of steel, the tests are carried out on specimens polished mechanically or chemically. The dry friction tests were performed on a ball-on-plate testing machine in order to determine the cyclical friction coefficient and the residual stresses developed during the slip of the tempered steel wiper on the specimen. Using the data analysis technique, the correspondence factorial analysis method describes more quickly a large data source by exploiting sophisticated descriptive statistics. The data will are then subjected to a factorial treatment using the metric of Chi-squared (2c) to preserve the probabilistic nature of the problem. This method is considered to be very useful and very precise for determining the residual stress under the cyclical loading caused by dry mechanical friction.

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.