Thermodynamics and Multi-physical Model for Application to the Effect of Severe Environment on Metallic Alloys

In this paper, we have formulated a fully coupled thermo-elasto-visco-plastic-damage theory, which includes both kinematic and isotropic hardening, and takes also into account the diffusion of several species in metals. This theory is based on the thermodynamics of irreversible processes under small strain hypothesis. Each specie is supposed to diffuse in both lattice and trapping sites. In order to take correctly into account of different coupling effects, the diffusion fluxes vectors depend not only on the gradient of chemical potential, but also on the gradient of temperature (thermodiffusion) and on the gradient of pressure (barodiffusion). The heat flux also depends not only on the gradient of temperature, but also on the chemical potential gradient of each specie, according to the thermodynamics of irreversible processes. This model is implemented into Abaqus/Standard using the Uel user subroutine. An application is made for the diffusion of hydrogen in TA6V after welding

Stress distribution correlated with damage in duplex stainless steel studied by synchrotron diffraction during plastic necking

The goal of this work was the determination of lattice strains distribution in two phases of duplex steel during plastic necking. Subsequently, the stress heterogeneity in the neck was studied in order to determine the reason for the damage initiation and to verify the hypothesis that the damage begins in the ferritic phase. To do this, X-ray synchrotron radiation was used to scan the ‘in situ’ variation of the interplanar spacings along the necking zone for samples subjected to tensile loading. A self-consistent model and FEM simulation were applied for the experimental data interpretation. It was found that for advanced necking the phase lattice strains, especially those measured at some distance from the neck centre, show a large inversion of the loads localised in both phases compared to the undamaged state (the lattice strains in the ferrite become smaller than in the austenite). This effect indicates stress relaxation in the ferrite which is connected with the damage phenomenon. Correlation of the experimental results with the modelling shows that the value of von Mises stress is responsible for the initiation of the ferritic phase softening

Higher spin quaternion waves in the Klein-Gordon theory

Electromagnetic interactions are discussed in the context of the Klein-Gordon fermion equation. The Mott scattering amplitude is derived in leading order perturbation theory and the result of the Dirac theory is reproduced except for an overall factor of sixteen. The discrepancy is not resolved as the study points into another direction. The vertex structures involved in the scattering calculations indicate the relevance of a modified Klein-Gordon equation, which takes into account the number of polarization states of the considered quantum field. In this equation the d'Alembertian is acting on quaternion-like plane waves, which can be generalized to representations of arbitrary spin. The method provides the same relation between mass and spin that has been found previously by Majorana, Gelfand, and Yaglom in infinite spin theories

Influence of surface mechanical attrition treatment (SMAT) on oxidation behavior of 316L stainless steel at 650°C

Abstract In this paper, the effects of Surface Mechanical Attrition Treatment on the high-temperature oxidation of AISI 316L austenitic stainless steel are investigated. Samples treated with different conditions were oxidized at 650 o C in order to study the effect of this type of nanocrystallisation on the oxidation resistance of the alloy concerned. X-ray diffraction and in-situ Raman spectroscopy were used to identify the oxides formed at the surface. The results indicate the presence of hematite and chromium oxides. Experimental results obtained by Raman spectroscopy were also used to study the stress evolution in Cr2O3 films during isothermal conditions

Large deformation and mechanical effects of damage in aged duplex stainless steel

International audienceThe lattice strains in large tensile deformations, up to the fracture of the sample were measured using neutron TOF method. For the first time, the range of large deformation was studied measuring lattice strain in the deformation neck and using special correction for macrostress value. It was found that during large plastic deformation the lattice stresses arise almost linearly with the macrostress value. The relaxation of elastic strains in some groups of ferritic grains (corresponding to reflections 211 and 200) can be connected with initiation of damage process in the ferritic phase

Influence of surface mechanical attrition treatment on the oxidation behavior of 316L stainless steel at 750°C

International audienceIn this paper, the effects of Surface Mechanical Attrition Treatment on the high- temperature oxidation of AISI 316L austenitic stainless steel are investigated. Samples treated with different conditions were oxidized at 750°C in order to study the effect of this type of nanocrystallisation on the oxidation resistance of the alloy concerned. X-ray diffraction and in- situ Raman spectroscopy were used to identify the oxides formed at the surface. The results indicate the presence of hematite, magnetite and chromium oxides. Experimental results obtained by Raman spectroscopy were also used to study the stress evolution in Cr 2 O 3 films during isothermal conditions