Effects of Crank Length on the Dynamics Behavior of a Flexible Connecting Rod

Global dynamics behavior of a damped flexible connecting rod is considered in this paper with emphasis on the effects of the rigid crank length. Nonlinear equations of motion in terms of axial and transverse deflections are derived based on Lagrangian strain formulation. When the crank length is small compared to the connecting rod, it is found that only one periodic solution exists in the speed range up to 1.5 times the first bending natural frequency of the connecting rod. As the crank length increases, however, multiple solutions may exist and the associated domains of attraction can be identified by cell-to-cell mapping technique. Moreover, the steady state response may become chaotic, which renders precise prediction of the dynamics response meaningless. The onset rotation speed of chaotic vibration decreases when the crank length increases. This result shows that previous research utilizing simplified or linearized models can predict the dynamics response of the flexible connecting rod only when both the crank length and the rotation speed are small.