[ANGLÈS] Stainless steel is a relatively recent material that combines excellent corrosion resistance and mechanical properties suitable for structural applications. But its nonlinear stress-strain behaviour, different from the typical carbon steel, explains, among other reasons, that it has had very little presence in the field of construction as a structural element. In the literature, there are different analytical expressions that reproduce this behaviour, all of them based on the original expression of Ramberg- Osgood. In this paper, the differences between these models are analyzed in order to determine the most appropriate expression, and suggest values for the parameters that fit properly the behaviour of the material, especially for different grades of ferritic stainless steel. Therefore, an interactive program is developed, reusable for any series of experimental data, and criteria for the determination of the initial elastic modulus (E0) are proposed. It is also demonstrated that the analytical expressions proposed by Rasmussen for determining, on the one hand, the parameters of non-linearity (n, m) and the ultimate strain (εu), included in the European code Eurocode 3, and on the other hand the ultimate tensile strength (σu) obtained from the Ramberg-Osgood parameters (E0, σ0.2 and n), do not provide good estimations in the case of ferritic alloys. Therefore, new analytical expressions to determine these parameters are developed in this paper. Compared with a reasonable range of experimental data, the expressions provide a good accuracy, which then participates in improving the modelling of the stress-strain behaviour for ferritic stainless steel.

[CASTELLÀ] Se analizan las diferencias entre los modelos propuestos en la literatura para modelizar el comportamiento tenso-deformacional no lineal del acero inoxidable, y se proponen valores optimizados de los parámetros que ajusten convenientemente dicho comportamiento. Se modifican las fórmulas propuestas por Rasmussen para aplicarlas al caso del acero inoxidable ferrítico.