Dynamic Analysis of the Forced Vibration Drilling Process

For aircraft application, the mechanical assembly of composite and metallic structures using fastener (rivet, nuts and bolt) remains the preferred technology. For aeronautical structure, it is then necessary to drill a huge amount of holes both in the composite and the metallic parts. For CFRP/Ti6Al4 V stacks, the drilling remains a critical issue. Indeed the abrasive wear and the thermo-mechanical stress induced by the cutting process lead to a fast damaging phenomena on the tool. To cope with the high quality standards required on the drilled hole, it is necessary to limit the burr height, the delamination of the composite, the roughness and the diameter tolerance. One of the proposed technical solutions is the forced vibration drilling. This process makes it possible to generate segmented and easy to evacuate chip without overloading the cutting tool. This paper presents a new vibration assisted device (VAD) which allows the adjustment of the amplitude of the forced vibration. A dynamical model is developed to optimize the vibration amplitude during the drilling process. This model is based on the identification of the static and the dynamic behavior of the VAD. An experimental protocol using monitored drilling tests was developed to identify the several parameters of the dynamical model. The good correlation between the simulation and the experimental results allows the validation of the proposed methodology.