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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 2933 Any correspondence concerning this service should be sent to the repository administrator: staff-oatao@listes-diff.inp-toulouse.fr AbstractA method is proposed for the evaluation of surface fatigue damage of hot forming tools that undergo severe thermo mechanical loading. Crack propagation under fatigue loading in a X38CrMoV5-47HRC is investigated using specimens of 2.5*8 mm*mm section. The effect of thickness on crack propagation is investigated. The crack propagation experiments are performed at different R values on single-edge cracked tension s curves are established. Short crack propagation in thin specimens is also investigated. Numerical simulation and analysis of the specimens is performed by ABAQUS® Standard software. Evolution of the J integral with respect to the crack length is investigated. Crack closure along the whole crack length is observed by a microscope. Effect of slip bands on crack propagation mechanism is investigated.

Silver-copper alloys are condensed in a liquid-solid domain of the phase diagram on a tilted molybdenum substrate regulated in temperature. After a droplets regime, a film which contains a monolayer of nodular solid crystals forms. The size distribution and density of the particles in the film are measured after different condensation times. Results show that in our experimental conditions a ripening process occurs which is evidenced by a decrease of the number of particles with time, and a broad particle size distribution. However, the decrease rate is smaller than expected without a condensation flux. A model is then developed to interpret and generalize these results. This model results from the modification of the Lifshitz-Slyosov model [1] to take into account the supply from the vapour phase. It is shown that the higher the flux of material to solidify from the vapour phase is, the more the growth from the vapour phase overcomes the ripening process. Once the particle density reaches a characteristic value which is simply proportional to the incoming flux, no more particles are dissolved. The system then tends towards a monomodal distribution with a radius which grows in t 1/3 .