Effect of surface hardness and roughness produced by turning on the torsion mechanical properties of annealed AISI 1020 steel

"This paper presents the results of experimental work carried out to study the influence of surface integrity, measured as hardness (HV) and roughness (Ra) on torsional properties of annealed AISI 1020 steel machined by turning using carbide insert tools. The results showed a reduction in ductility when hardness and roughness increase, caused by the plastic deformation induced after machining. It was shown that the shear yield strength increases, as a consequence of the material strengthening by work-hardening and the rise of stress concentrators. Further, the ultimate shear strength increases with surface hardness, having the opposite effect when the surface roughness caused greater stress concentration."