The present work is devoted to experimental and numerical investigation of in situ tensile tests to recognize the mechanisms of ductile fracture under different stress states. The GTN model, which is a micromechanical based damage model, was used for numerical simulations. The void related parameters of GTN model for SAE 1010 plain carbon steel were identified by response surface method (RSM) through minimizing the difference between numerical and experimental results of tensile test on a standard specimen. The void related parameters of GTN model were determined 0.00107, 0.00716, 0.01 and 0.15 for f₀, f_N, f_c and f_f respectively. After calibrating the damage model for the studied material, the tensile tests were carried out on the in-situ specimens with different geometries. The fractographic analysis was performed to identify the ductile fracture under wide range of stress states and two failure mechanisms were observed. The calibrated damage model was applied to FE simulations of in-situ tensile tests for numerical study of the experimentally observed fracture phenomenon. The extracted numerical results showed a good agreement with experimental observations comparing load-displacement plots with a margin of error within 5%. A better ductile fracture predictions were captured in 90° specimens. The location of fracture initiation, crack growth orientation and the displacement at fracture zone in numerical studies also showed close correspondence with experiments.