Study On The Dynamic Modeling And Peformance Matching Of The Rubber-damped Torsional Vibration Damper For The Crankshaft System Of The Engine

Torsional vibration is the inherent properties of the crankshaft system in the engine for the vehicle.The Torsional Vibration Damper(TVD)is attached to the front end of the crankshaft to reduce the torsional vibration of the crankshaft system.The rubber-damped TVD is most widely used in modern vehicle due to its low cost,simple construction and greater reliability.In this dissertation,the rubber-damped TVD of an in-line 4-cylinder gasoline engine is studied according to a three-level "rubber material-TVD component-crankshaft system" solution procedure,and the dynamic modeling and performance matching are researched in different ways of theoretical simulation,optimal design and experimental analysis.Firstly,the nonlinear shear properties of the rubber ring of the rubber-damped TVD are studied which can reveal the relationship among the material properties,the rubber hardness and the compression ratio of the rubber ring.The double-shear-type rubber specimens and a test fixture are designed,and the shear properties of the rubber specimens are got with different rubber hardness and the compression ratio of the rubber ring.Based on the dynamic models of the rubber isolator,three constitutive models based on the above-mentioned Kelvin-Voigt,Maxwell and fractional derivative models are formulated,whose parameters are identified using the least squared method according to the measured dynamic shear stiffness of the rubber specimen.Then the relations for the parameters of the constitutive models with compression ratio under different rubber hardness are obtained.Secondly,the natural frequency of a nonlinear rubber-damped TVD is predicted using the methods of theoretical calculations and finite element method(FEM),which provides a reliable method for predicting the nature frequency of the rubber-damped TVD prior to prototyping.The theoretical calculation methods of the natural frequency are obtained from the above-mentioned dynamic models of the rubber-damped TVD,the torsional stiffness and damping coefficients are calculated according to the relationship among the material properties,the rubber hardness and the compression ratio of the rubber ring,and then the natural frequency obtained from different models are got and compared with the measured data which shows that the fractional derivative dynamic model can provide more effective estimations of the natural frequencies of the damped TVD over the entire range of excitation magnitudes in this study.In consideration of the little deformation of the rubber ring,the hyper-elastic and visco-elastic properties of the rubber material are considered using the FEM.The hyper-elastic property of the rubber material is characterized with Mooney-Rivlin constitutive model,and the visco-elastic property is characterized with Prony serials constitutive model.Then the nature frequencies of the rubber-damped TVD under different rubber hardness and different compression ratio are obtained using the ABAQUS software and compared with the measured data which show that the relative errors are small.At last,the multi-objective performance matching and robust optimization design of the rubber torsional vibration damper are performed.The lumped parameter models of the engine crankshaft are built respectively before and after the rubber-damped TVD are attached to the crankshaft.According to the energy equivalent principle,the fractional derivative dynamic model of the the rubber-damped TVD is equivalent to the mass-spring-damper dynamic model,and the equivalent model is introduced into the crankshaft lumped parameter model.The differential equation of torsional vibration of the crankshaft system is established and solved using numerical method,and then the torsional vibration analysis of the crankshaft system is performed.The multi-object performance optimization of the rubber-damped TVD is performed using NSGA-? genetic algorithm,and the global optimal solutions of the design parameters such as rubber hardness,compression ratio of the rubber ring and the moment inertial of the inertial ring are got.The performance robust design of the rubber-damped TVD is performed using Taguchi method and the optimal levels(i.e.the local optimal solutions)of the design parameters are got,which are better theoretically than the global optimal solutions for the control of the torsional vibration of crankshaft system.The torsional vibration responses of the crankshaft system with different rubber-damped TVD are measured,and the experimental results show that the final design parameters of the rubber-damped TVD using Taguchi method are reasonable and the performance robustness of the TVD is enhanced.The research results of this dissertation have certain directive significance to the design of rubber-damped TVD and the control of torsional vibration of the crankshaft system for the engine.