Design and performance study of a bionic damping boring bar based on the woodpecker

Deep hole machining is a typical challenging process in the aerospace industry, where long overhang boring bars are prone to vibrations, resulting in poor surface quality, reduced tool life, and noise. To address the vibration issues in deep hole machining, this study proposes a bionic damping boring bar inspired by the woodpecker’s shock-absorbing head. The study first analyzes the structure of the woodpecker's head and establishes nonlinear vibration equation, which is solved using the Harmonic Balance Method (HBM). A preliminary bionic design of the boring bar was then proposed, consisting of two main structures: constrained-layer damping (CLD) shaft and bionic absorber. A three-stage biomimetic damping system was developed using metal, particulate materials, damping materials, and carbon fiber reinforced polymer (CFRP). A dynamic model of the boring bar is established to analyze the effect of structural parameters on amplitude response. Subsequently, particle swarm optimization (PSO) and orthogonal experiments are used to optimize the tool body and the bionic absorber. Finally, modal and cutting experiments are conducted, comparing the bionic damping boring bar with carbide boring bars. The results show that the bionic damping boring bar improves modal parameters and cutting stability. Compared to carbide boring bars, it has a 20 % higher natural frequency, 5 times higher damping ratio, and 1.7 times higher stiffness. At the same cutting depth, it provides smoother acceleration amplitude response in the time domain, lower harmonic amplitude in the frequency domain, and improved surface quality, resulting in higher machining accuracy.