Résumé: Un chauffage par induction a été employé pour élever rapidement la température d'une éprouvette en acier et d'une éprouvette en fer pur, avant de les tester au vitesses de déformation > 10 3 s " 1 . Les résultats montrent en général que la ductibilité diminue pour des températures au-delà des limites testées (20 -400 °C). Basé sur des informations expérimentales et sur les résultats de simulations numérique de l'essai, un modèle empirique a été dérivé pour du fer pur et donne la tension de fracture en fonction des contraintes et de la température. Récemment, la technique de chauffage par induction a été étendue aux matériaux non-ferreux. Des tests à fortes tension sur du cuivre à 99,99% pur n'ont pas révélé les effets de la température sur la ductibilité du matériaux audessus des températures employées (20 -300 °C).Abstract: Induction heating has been employed to rapidly raise the temperature of ferrous specimens prior to testing at strain-rates > 10 3 s" 1 . The results show a general tendency for the ductility of a specially-processed pure iron to decrease with temperature over the range tested (20-400 C). Based on the experimental data and the results of numerical simulations of the experiment, an empirical fracture model has been derived for the iron which gives fracture strain as a function of state-of-stress and temperature. Recently, the induction heating technique has been extended to nonferrous materials. High strain-rate tests on 99.9% pure copper revealed no significant effect of temperature on ductility over the range of start temperatures employed (20-300 C).

High strain-rate tensile tests have been carried out on pre-notched specimens of OFHC copper and Remko iron at both elevated and cryogenic temperatures. When properly expressed as a function of stress triaxiality at the centre of the notch (as predicted by numerical simulations of the experiment), the ductility of copper was found ta be independent of temperature over a range from -190°C to 300°C. The specially-processed Remko iron was found to undergo a ductile-to-brittle transition at a temperature dependent on the stress triaxiality and the particular batch of the material. Otherwise the fully ductile strains-to-failure (when expressed as a function of stress triaxiality) for iron were found to decrease with increasing temperature up to 400°C; this being the maximum temperature tested. NOMENCLATURE do =initial minimum diameter df = post-fracture minimum diameter T, = melting temperature To = test start temperature T, = reference temperature (20°C) Ef = effective plastic strain at failure = 2 In(d,/d,) u, = Von Mises effective stress urn = mean stress T** =homologous temperature = (T, -T,)/(Tm -T,)

In this study, we investigated the synthesis of pack cemented coating on two metallic materials (304 & 316L) in order to form silicon compounds on their surface at lower temperatures (800,900 &950˚C) to avoid sintering of the pack and adhesion of material to the samples surface.In our investigation silicon was used as a master alloy and alumina (Al2O3) as a filler material. Also ammonium chloride was used as an activator with different weight percentage (5,7 &10%) ,in order to increase the efficiency of the coating layer formation process. Silicon zing of two alloys which are 304 & 316L by pack cementation process according to light optical microscope examination (LOM), the coating layer formation is a temperature and activator weight percentage dependent process, which means that it is a diffusion controlled reaction. Thus the thickness of sample silicon zed with pack content 10% activator at 950˚C is higher than the sample silicon zed with pack content 7% and 5% activator and these samples have higher thickness than samples coated at 900˚C and 800˚C at same conditions. The average coating thickness obtained by silicon zing process at 4hr by using different activator weight percentage for two selective alloys are:1-8.520 -129.390 am for 304 st.st alloy. 2-75.929 -192.592 μm for 316L st.st alloy.

This research include the study of the fatigue property for the polymer and the composite materials, we using the epoxy resin as matrix for the reinforced materials that consist of artificial fibers (Kevlar, glass and PVC fibers) also aluminum powder for reinforcing.The slates made of composite materials and hybrid composite materials for both volume fractions30% and 40% from the reinforced materials, where we made twenty one slates from the composite materials, all these slates cutting to samples with measurement (10x 70mm) in order to execute the fatigue test accordingly for the fatigue machine characteristics, these samples divided to several groups for both volume fractions 30% and 40%, these groups immersing in H2SO4 acid for fifty day to study the effect of this solution in the fatigue characteristic.The test executed by two steps: -the first step include executing the fatigue testing for the dry samples and comparison these results with each other, the second step include the fatigue test for the samples after immersion in the solution (H2SO4 acid) for fifty day,. The results of fatigue test from the second step comparing with the results from the first group for both volume fractions 30% and 40%. The results and laboratory examinations for these samples show a decreasing in the number of fatigue cycles until the fail when the applied load or applied stress increase.

In the present investigation, the static electrochemical corrosion behavior of nano (Al 2 O 3 ) P and nano (SiC) P based aluminum in Fao water was compared. The nanocomposites were fabrication using liquid metallurgy technique. The effect of nanoparticulates weight percentage (5%, 15% and 25%) on the corrosion was studied. The results showed that the Al reinforced with nano (Al 2 O 3 ) composites exhibited lower corrosion rates that the Al reinforced with nano (SiC) P composites. The corrosion rate was found to be increased by increasing of the weight percentage of the nanoparticles more than 5% nano (Al 2 O 3 ) P composites exhibited the highest corrosion resistance among all the investigated nanocomposites.