Dynamic Characteristics Analysis And Experimental Research Of Powertrain Vibration Isolation And Torsional Vibration Of Crankshafts

The dynamic characteristics of powertrain mounting system in vehicles and vessels and torsional vibration systems of shafting is investigated theoretically,simulatively and experimentally.A general transfer matrix model for three-dimensional coupled system with multi-mounts when excited by combined multi-directional forces and moments is developed,in which the general excitation forms,multi-dimensional wave effects in the elastic mounts and foundation flexibility are taken into account.Modes decoupling method of rigid body is confirmed combined with engineering situation,and the power transmission of vibration isolation system with complex flexible foundation is analyzed through power flow method and finite element method(FEM).Also,torsional vibration power transmission characteristics of crankshaft axle plate model is developed that inspired from power flow theory.At last,the model for dynamical characteristics measurement in flexible isolation system is investigated.Transfer matrices for three-dimensional coupled system with multi-mounts when excited by combined multi-directional forces and moments is developed,in which the general excitation forms,multi-dimensional waves effects in the elastic mounts,foundation flexibility and spatial power distribution are taken into account.It is shown that the coupled rigid body mode and resonant flexural modes of foundation plate have notable effects on the power input to the system and transmitted to the foundation at lower and higher frequency domains respectively,when combined excitation of axial and transverse forces and moment act on the source.In particular,the power transmission excited by the moment induces more flexural wave power in the supporting structure than that excited by the axial force.The first two resonance of the standing longitudinal waves and the first resonance of the standing flexural wave in the mount have obvious effects on the power transmission.The axial power component transmitted through all the mounts is almost equal to the total power transmitted,and the angular or transverse power is smaller,even negative.Dynamic model of powertrain mounting system is derived to explore multi-dimensional coupling vibration of powertrain.Then six degree-of-freedom natural frequencies were calculated and decoupling conditions of the most important vibration modal are confirmed.According to previous conclusions,a powertrain mounting system of heavy truck is designed and verified.FEM and power flow theory are combined to explore flexible vibration of complex foundation in engineering.Vibration power transmitted in vibration isolation system with complex flexible foundation can be obtained.The results show that obvious and dense peaks of vibration power appear because of foundation flexibility,isolation effect has deteriorated at middle and high frequencies.Foundation flexibility is essential to vibration transmission in the whole system.The new method is practically significant to explore flexible vibration isolation system with complex foundation in engineering.Two kinds of dynamical models of crankshaft torsional vibration system in whether or not considering the distributed mass parameters of crankjournal are derived.The torsional power input to system and transmitted to flywheel when excited by torsional moment is calculated by transmission matrix method.It is shown that the overall torsional resonance modes of system and the first resonance of standing torsional waves in crankjournal have notable effects on the torsional power input to the system and transmitted to the flywheel at lower and higher frequency domains respectively.The changes of internal damping of crankjournal and moment of inertia of torsional vibration damper both have effects on torsional vibration power transmission.The investigation of torsional power transmission in crankshaft system have significance for the whole power transmission system.The measurement of flexible isolation system is investigated.One-stage isolation system with beam foundation is built to measure power flow and acceleration mobility and to test experimental modes and relevant modal damping.Test results are compared with theoretical calculation and FEM validation results.