Determination of Plastic Properties of Hastelloy C-276 Sheet and AISI 1012 Steel Round Bar Using Finite Element Analysis

The present work addresses the FEA of the full specimen tensile model of Hastelloy C-276 sheet and AISI 1012 Steel round bar. The study includes the determination of various plastic properties (especially von Mises stress and equivalent plastic strain) via experiment—FEM correlation under tensile loading conditions. The deviation between the ultimate stress obtained through FEM and the experiment was below 0.35% in the present study. The correlation plot between von Mises stress and equivalent plastic strain helped to determine the optimal mesh size (0.5 and 2 mm) for FE models. Further, the same plot also helped in determining the value of fracture strain (~ 0.75 ± 0.05 mm/mm) to differentiate the conditions necessary for obtaining fracture via necking from that of flat fracture or no fracture condition in FEA. The slope of the equivalent plastic strain vs. time graph showed two distinct regions, steady rise and steep rise, each defining the different instantaneous state of material deformation when correlated with the corresponding stress–strain plot. ‘Critical element size’ in FEA has been proposed for determining the criteria for element deletion to model the phenomena of specimen fracture upon stiffness reduction. The implementation of directional vectors for the representation of the stress–strain distribution was found helpful in projecting the region of tension and compression during the entire duration of the tensile test. The instantaneous area obtained through FEA helped in plotting the true stress–strain graph which was further used to determine the strength coefficient and strain-hardening exponent for both alloys. The behavior of tensile specimen post-necking was studied via the implementation of the Kim–Tuan hardening to establish an inverse correlation between the hardening function and elongation at higher plastic strain. Finally, a list of optimal FE model parameters to obtain a better match with the experimental results is also presented.