Chattering in composite deep-hole boring can directly affect surface processing quality and efficiency and has always been a research hotspot in machining mechanics. In this study, based on Euler–Bernoulli beam theory, the fine control equations for the cutting stability of composite variable-section boring bars were established using the Hamilton principle, in which the sectional change and internal damping of the material were considered. Next, using the Galerkin method and semi-discrete method, the effects of the taper ratio, damping ratio, length-to-diameter ratio, and ply angle on the free vibration characteristics and cutting stability were analyzed in detail. The results show that at a low damping ratio, both the first-order inherent frequency and boring stability can be enhanced with the increase in the taper ratio; at a large damping ratio, increasing the taper ratio can reduce the first-order inherent frequency and boring stability. Finally, the effects of the sectional change on the inherent frequency, displacement response, and convergence were analyzed. A numerical simulation was performed for the model reliability validation. The present research results can provide a theoretical basis and technical guidance for analyzing the cutting stability and fine control of composite variable-section boring bars with large length-to-diameter ratios.

The free vibration behavior and stability of composite milling bar with large aspect ratio are analyzed. Specifically, the free vibration equations are derived based on Euler Bernoulli beam theory and Hamilton’s principle and solved by Galerkin method. In addition, to investigate the stability of the cutting system with a rotating composite milling bar, this study develops an analytical model for regeneration and cutting force fluttering, in which the internal damping, external damping, gyroscopic effect, and inertial effect are considered. The subsequent stability lobes are obtained by the time domain method. Then, the stability of composite and conventional metal milling bar is compared. The effects of internal damping, external viscous damping, ply angle, gyroscopic effect, and inertial effect on cutting stability are analyzed.