Assessment of Ramberg-Osgood model parameters for an additively built wall through stress-strain curve generation

Predicting the tensile response of directed energy deposition (DED) fabricated additively built wall (ABW) is challenging due to thermal cycling-induced heterogeneity and directional solidification. This study presents a systematic application of Ramberg-Osgood (RO) fitting combined with microstructural interpretation to describe the effective macroscopic true stress–true strain response of a DED-fabricated structure. Tensile testing, based on crosshead displacement measurement, showed that ABW exhibited a higher uniaxial tensile strength (UTS) of 559 MPa and a yield strength (YS) of 309 MPa compared to wrought steel (525 MPa and 219 MPa), along with comparable elongation (28% vs.32%). Strain hardening exponent-n is significantly higher for ABW (8.32) than for wrought steel (5.79), due to refined microstructure. The RO model reasonably captured the nonlinear elastic–plastic response within the uniform deformation regime, with high coefficients of determination (R2 = 0.91–0.96). Microstructural and fractographic analysis confirmed sound metallurgical bonding and predominantly ductile failure characteristics. The study demonstrates the applicability of RO-based modelling for engineering-level mechanical description of DED fabricated structures.