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Simulation numérique du choc laser pour la mise en compression en présence de l'état initial dû au soudage

Abstract : Surface treatments as laser shock peening offer the possibility to reduce tensile stresses or to generate compressive stresses in order to prevent crack initiation or reduce crack growth rate in particular in the areas where tension weld residual stresses are present. Laser shock peening may be applied on different metallic components to prevent stress corrosion cracking of Inconel 600 and high cycle thermal fatigue of austenitic stainless steels. The main aim of the PhD thesis is to develop the numerical simulation of laser peening. In the first section, axisymetrical and 3D numerical models for one or several pulses have been developped in Code_Aster and Europlexus softwares. These models were validated by experimental tests carried out in PIMM-ENSAM laboratory. Parameters identification of Johnson-Cook constitutive law was carried out for Inconel 600 at high strain rates. Moreover a new test was proposed which allowed proving the isotropic behavior of Inconel 600 at high strain rates. A modification of the Johnson-Cook constitutive law was also proposed, to take into account in a new way the sensitivity of the law to high strain rates. The second section of the thesis concerns a study on the effect of an initial state of welding on residual stresses after application of laser peening. We could conclude that this initial state has no strong influence on final residual stresses. Finally, a qualitative study on the effect of strain hardening induced by laser peening on fatigue life of stainless steels was undertaken, which shows the advantage of laser peening on shot peening due to smaller strain hardening created by laser peening.
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Submitted on : Thursday, January 29, 2015 - 6:31:30 PM
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Emricka Julan. Simulation numérique du choc laser pour la mise en compression en présence de l'état initial dû au soudage. Mécanique des structures [physics.class-ph]. Ecole Polytechnique Paris, 2014. Français. ⟨tel-01111205⟩

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