Análise das tensões atuantes ao longo do raio de aresta da ferramenta no corte ortogonal de um aço endurecido

Abstract

On the one hand, mechanical strength and thermochemical stability are important properties for the tool material. On the other hand, edge geometry significantly influences the distribution and direction of forces acting in the cutting region. In finish turning, ceramic tools are frequently used due to their high wear resistance, despite their low fracture toughness, which can lead to sudden and unexpected failure. Thus, evaluating the effect of geometric variation and contact conditions is a key point for achieving stability and cut quality. However, for a correct choice, the acting forces and stresses must be properly mapped. This study aims to propose a new method for analyzing failures and acting stresses in different edge geometries. To this end, an analytical model was developed to calculate the stresses acting along the edge radius for 36 types of rounding (K < 1, K = 1 e K > 1) prepared in mixed ceramic inserts (Al2O3-TiCN), discretized by three chamfers and applied in experimental tests on the orthogonal cutting of hardened AISI 4140 steel with constant parameters. The results demonstrated the effect of the geometric parameters of the edge on the stresses acting during cutting, with the maximum stresses occurring at the wear nucleation points, between the end of the edge rounding and the beginning of the tool rake face. The failure probability map and statistical tests revealed an increasing relationship between the maximum shear stress and the edge failure tendency. For the Weibull distribution, a modulus of 4,08 and a minimum stress of 1605 MPa were obtained for the microgeometry Sα = 103,2 µm and Sγ = 179,3 µm, which led to only 1,10% edge failure, therefore, this microgeometry performed best in terms of preventing wear nucleation in the investigated process.