Prediction of residual stresses in ball burnishing TI6AL4V thin sheets
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ORIGINAL ARTICLE
Prediction of residual stresses in ball burnishing TI6AL4V thin sheets Haydar Livatyali 1
&
Ergül Has 2 & Mevlüt Türköz 3
Received: 24 February 2020 / Accepted: 27 July 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract The static-implicit finite element method was used to simulate the low plasticity ball burnishing process using two-dimensional (2-D) and three-dimensional (3-D) models. The simulations were performed using an elastic-rigid strain hardening plastic flow model. The residual stress distribution along the surface layer of the Ti6Al4V thin sheet is predicted, and the results are compared with limited experimental data from the industry. The simulated residual stresses matched with the measured ones in terms of trends; however, some deviations were observed for the peak and boundary values. The 2-D model is practical to construct, and the simulations are fast; however, it does not provide the planar stress distribution. The 3-D model is more realistic, yet still very sensitive to boundary conditions as well as friction. More realistic results are possible with large models where the effects of boundary conditions get weaker. Keywords Low plasticity ball burnishing (LPB) . Finite element method . Residual stress
1 Introduction Finishing processes have always been considered crucial in the manufacturing environment, due to the effects of surface quality on the performance and service life of mechanical components. The surface integrity of an engineered surface is generally characterized in terms of surface finish, state of residual stress, and micro-hardness. These properties are critical for the fatigue life of a functional surface put under highly stressed conditions. In general, fine surface finish, compressive residual stress, and a high degree of hardness on the surface layer prolong the fatigue life of the parts and improve the service performance [1]. Therefore, the final surface finish operation directly influences the functionality of the components under actual service conditions. Regardless of the manufacturing method, all surfaces consist of a series of peaks and valleys at variable heights. In the
* Haydar Livatyali [email protected] 1
Department of Mechatronics Engineering, Yıldız Technical University, Istanbul, Turkey
2
Department of Mechanical Engineering, Istanbul Technical University, Istanbul, Turkey
3
Department of Mechanical Engineering, Konya Technical University, Konya, Turkey
low-plasticity burnishing (LPB) process, to deform the surface layer and flatten these peaks, a smooth free-rolling spherical ball (or cylindrical roller) is employed at a single pass or several passes under limited normal force [1]. The ball is rolled across the surface of a component while being supported by a constant volume flow of fluid that enables single-point contact. Consequently, a strain hardened smoother surface with compressive residual stress on the surface and towards the depth of the material is introduced (Fig. 1). The compressive residu
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