Residual stress formation mechanism considering cutting energy in milling of 7075 aluminum alloy

Aluminum alloy has the characteristics of good corrosion resistance and high strength, so aluminum alloy workpiece is widely used in the aerospace field. However, in milling, the surface of the aluminum alloy workpiece generates residual stress due to the coupling of force and heat, which seriously affects the fatigue performance of the workpiece. To investigate the residual stress formation mechanism, an analyzed model of machining-induced residual stress considering energy conversion in milling process was proposed. In this process, the milling force prediction model is established. Then, an effective cutting work model is established based on the milling force model. After that, the strain energy density of the machined surface layer was analyzed and the strain energy solution model was established. Subsequently, the prediction models of mechanical stress, thermal stress, and residual stress are established respectively, and the residual stress values are brought into the strain energy model to obtain the strain energy. Afterwards, the functional transformation relationship between effective cutting work and strain energy storage per unit time is analyzed. Finally, several milling experiments were carried out to verify the predicted milling force and residual stress values. Experimental results show that errors between the predicted values and the experimental values are about 5% and 15%, respectively, and the conversion relationship between work and energy show that the stored strain energy per unit time increases with the increase of the effective cutting work.