Influence of turning parameters on residual stresses and roughness of 42CrMo4+QT

Abstract

Residual stress and surface roughness have been recognized to play a critical role in the fatigue strength of metal components. Machining processes can induce different roughness and residual stress conditions depending on the parameters used in the process. Therefore, it is essential to develop knowledge that helps to predict the residual stresses and roughness that would be obtained from different machining conditions. The main aim of this work is to establish two phenomenological models to accurately predict residual stress and roughness values on specimens turned from 42CrMo4+QT. The models are derived on data of 4 process variables: (a) insert tip radius; (b) feed rate; (c) cutting speed; and (d) depth of cut. For this purpose, a wide experimental campaign has been developed, which includes the machining of 68 specimens under various cutting scenarios, and their subsequent measurement of residual stresses and roughness. Once the experimental data were obtained, the response surface method based on the central composite design was used to fit the models, obtaining a correlation index higher than 0.9 in both cases. In this article, it is concluded that feed rate and insert radius have a greater effect on the residual stress and roughness obtained, while cutting speed and depth of cut have a lesser impact on the results. It is hoped that the findings will establish a groundwork for the machining of this material type, ensuring controlled conditions of residual stress and roughness.