Dr. FACI Youcef

High yield strength steels (HSLA) are microalloyed niobium, vanadium and titanium steels. They are known as dispersoidal steels with respect to elements forming stable insertion phases. The main structural constituents of these steels are: ferrite, perlite and secondary phases (carbides, nitrides). These steels are used in the as-rolled state or in the improved state for welded constructions and pipelines. Their intrinsic properties after thermomechanical rolling are obtained by hardening of precipitation and by refining. These compounds prevent any growth of grains during heating giving rise to fine grain structure. However, thermal and/or thermomechanical treatments applied to maximize the mechanical properties of these alloys can sensitize them to various modes of structural corrosion.For this reason, we will follow the evolution of the metallurgical and electrochemical behavior of L485Q grade steel (Quenched and tempered) in relation to the effect of precipitation after thermal improvement treatments. We will do a final comparative study with the same grade of L485M Thermomechanical rolled steel according to the ISO3183 standard.Thus, knowledge of the mixed influence of precipitation hardening and microstructural modifications resulting from heat treatments on the corrosion resistance is necessary to allow the desensitization of these alloys to this mode of damage, by introducing in particular a normative notion. imitates elasticity /corrosion resistance "among the many requirements.

A significant amount of scale is produced during casting of ingots and processing of hot-rolled products. In manufacturing steel, during the various rolling operations, the amount of scale produced is approximately 0.1% of the annual production of the rolling mills. The quality of the thin sheet during rolling is affected by the behavior of the iron oxide layers formed on their surfaces. For this reason, acids and oils are used for the descaling of slabs and billets by means of pressurized water. The calamine, contaminated by these various acids and used oils, is rejected and stored involuntarily on important areas and pollutes soil and groundwater. Micrographic observations as well as X-ray diffraction analysis have shown that calamine consists mainly of iron oxides. Hematite and magnetite become the main components for oxidation times greater than 1 hour. Characterization tests have shown that calamine is dense (ρ = 4.8 g/cm3), its particle size is variable depending on the degree of oxidation (from 0.5 to 10 mm). Simultaneous thermal analysis showed that an increase in mass of the calamine sample with a release of heat. Studies are underway for the physico-chemical characterization of the soils of the storage areas.

Fiber reinforced composite materials have been increasingly used as structural material in airplanes and in space applications because of their high specific stiffness and strength. This work presents the results of the damage kinetic of carbon fiber reinforced polymer using the acoustic emission under solicitations. The correlations between acoustic emission parameters and damage mechanism are identified, and then confirmed by microscopic observations. This review will emphasize the roles that AE can play as a tool for the composite materials, damage mechanisms, and characterization of damage evolution with increasing time or stress, the localization and origin of damage, quantification of crack size based on energy release from concrete structures in the field and reduction in the numbers of test specimens required in various studies.