Effect of variable moment of inertia on torsional vibration of a crankshaft-absorber system

摘要

Moment of inertia of crankshaft system is variable with crank angle, which may induce complex torsional vibration of reciprocating machines. In this paper, a two-degree-of-freedom dynamic model of a crankshaft-absorber system considering the variable moment of inertia of crankshaft is established by the application of Lagrange's equations. Using the method of multiple scales, average equations under primary and 1:2 internal resonances are obtained to determine the steady-state amplitudes. Theoretical analyses are employed to investigate the effect of variable moment of inertia on system modes. It is found that a critical variable moment of inertia exists in this system. When the actual variable moment of inertia is close to it, stable amplitudes of the system are extremely small, or a rebound phenomenon will appear. Besides, the effects of physical parameters on this threshold are studied and an approximate formula is derived. Finally, the correctness of theoretical analyses are verified by contrast with numerical integration.