MODEL FOR CALCULATION OF DEFORMATION AND RESIDUAL-STRESS IN OXIDE LAYERS UNDER VARIABLE THERMAL CONDITIONS

A one-dimensional model based on finite elements calculation is propos ed in order to explain the mechanical behaviour of metal-oxide systems . In spite of a general approach this model has been specially applied to the NiO/Ni system. This model takes into account the thickening of the oxide layer, the epitaxial misfit between the oxide scale and the metallic substrate, the volume variations, the visco-plastic deformat ions of the materials and the effect of temperature on the mechanical coefficients of the system. This model leads to calculate the variatio n of the residual stresses in the oxide scale and to relate them to th ermal cycling conditions or variations of cooling rates. The calculate d values are compared to experimental data obtained by X-RD; this comp arison demonstrates a good agreement.