Investigation of aluminum alloy properties during helical roller burnishing through finite element simulations and experiments

Abstract

Industry is always looking for ways to increase the lifetime of assemblies, especially the fatigue lifetime, from the production phase of fastening holes onwards. Helical roller burnishing is presented here as an innovative mechanical surface treatment. Applied directly after orbital drilling, this technique induces superficial plastic strains that reduce surface roughness and increase hardening and compressive residual stresses. Several studies on 3D finite element models of burnishing have been carried out but they are very time-consuming. In this review, a comparative numerical study of helical burnishing (in terms of calculation time and results on residual stress) between one 3D and two 2D plane strain finite element simulations is performed on 2024-T351 aluminum alloy drilled parts. The impact of the process operating parameters is also investigated. This comparison shows fairly similar results regarding the residual stress profiles but levels are rather different. This could be explained by the complex kinematics of helical roller burnishing, which is strongly three-dimensional. The numerical results of one of the cases studied reveal compressive residual stresses of around −100 and −490 MPa in the radial and circumferential directions of the hole, respectively. Burnishing depth and spindle rotation speed have a great impact on the final residual stress profiles. These simulations are then confronted with experimental results obtained during tests carried out using an orbital drilling unit (ORBIBOT). This demonstrates the interest of the modeling implemented and also points out ways to improve the developed models.