Estimation of dynamic behaviors of hydraulic forging press machine in slow-motion manufacturing process

Abstract

In this paper, stick–slip phenomenon of hydraulic forging press machine (HFPM), a nonlinear manufacturing system subjected to weak rigidity and negative friction velocity gradient, was investigated in slow-motion process. Dynamic characteristics of non-smooth motion were investigated experimentally under various operating conditions in slow-motion process. Taking into account the quadratic and cubic nonlinearities, the governing equation of the HFPM was derived. The method of multiple scales was employed to obtain approximate solution for velocity oscillation during slow motion. The steady-state responses for each case (i.e., non-resonance, primary, super-harmonic and sub-harmonic oscillation) were examined to investigate the correlation between velocity oscillation and nonlinear vibration in slow motion. The effects of viscous damping coefficient, hydraulic stiffness, friction parameters, excitation amplitude and frequency on the amplitude–frequency response characteristics were studied, and the interaction between system dynamics and tribological effects were presented. The stability of operational conditions and the critical velocity of the forging process were analyzed through the bifurcation techniques. Experimental results conducted on the HFPM verify the effectiveness of the proposed method.