Substructure analysis of vibration-assisted drilling systems

Abstract

Designing vibration-assisted drilling (VAD) toolholders requires accurately modeling the dynamics of the mechanical structure and its electromechanical coupling with the piezoelectric actuator. The overall dynamics of the VAD toolholder depends on the dynamics of its individual components (e.g., concentrator, piezoelectric disk, drill bit) and the interactions between them. Modelling by substructure analysis therefore provides an efficient framework for studying the effect of each component on the overall dynamics of the VAD system. Nonetheless, the existing substructure analysis methods are only applicable to holders with basic concentrator geometry, which limits their application in designing high-performance holders. In this paper, Receptance Coupling Substructure Analysis (RCSA) is used to combine the dynamic models of the toolholder’s components to determine its vibration response to the electrical excitation of the piezoelectric actuator. This method allows for combining the 3D finite element models of the concentrator with the simplified and analytical models of the rest of the VAD components, enabling the inclusion of complex concentrator designs in modeling without imposing a large computational load. Furthermore, because this method couples the mechanical model of the structure with the electrical model of the piezo-actuator’s impedance, it can be used as a design tool to modify the toolholder’s natural frequencies by tuning the electrical impedance of its piezoelectric components. This possibility effectively converts the piezoelectric components to mechanical members with adjustable structural dynamics, while they also actuate vibrations. Both axial and axial-torsional VAD toolholders are studied in this work, and the accuracy of the presented modelling approach is verified experimentally.