A new two-stage constitutive model for characterizing stainless steel stress-strain curves

Stainless steel alloys come in a wide range, all exhibiting notable nonlinearity and strain hardening in their stress-strain characteristics. This behaviour can be analysed and represented by different material models, among which the two-stage Ramberg-Osgood model adopted in prEN1993-1-14, an extension of the classical RambergOsgood model, is the most popular. While this model fits well with the overall stress-strain curve, it has been noted in previous studies and confirmed in this research that the model is not ideal for certain small strain ranges, and it is also not suitable for materials under compression. This paper proposes a new constitutive model and provides predictive expressions for key parameters in the model, covering both the full strain range and the 10 % plastic strain range. These predictive expressions are based on an analysis of a database containing over 200 stress-strain curves, including data from literature and tests on stainless steels. The database includes various grades, plate thicknesses, and product types. The applicability of the constitutive model was assessed using the stress-strain curves in the database and compared with the two-stage Ramberg-Osgood model adopted in prEN1993-1-14. The results show that, compared to the two-stage Ramberg-Osgood model in prEN1993-1-14, the proposed model provides more accurate and relatively conservative predictions across the entire range of the stress-strain curve.