Research On Fractional Order Damping Characteristic Of Viscoelastic Buffer Structure For Constructin Vehicle

The construction vehicle is one of the major components of the equipment industry.Due to the terrible working environment,the special acting object and the large power output,the vibration level of the construction vehicle is considerable,which not only has a strong impact on the performance and the reliability of the vehicle structure,but also exerts negative influence on the surrounding environment and the operator health.Thus,the vibration hazard of the construction vehicle has become one of the most important issues urgently needing further investigation in equipment manufacturing industry with high quality.The viscoelastic damping structure was widely used in the vibration and noise control of the construction vehicle because of its high vibration dissipation capability,simple structure and lower maintenance cost.The mechanical behavior of the viscoelastic materials displays anelastic feature and temperature and frequency dependence,so the precise dynamic modeling is the key step in the design and vibration damping analysis process of the viscoelastic structure.The fractional derivative based on global definition can precisely represents the history dependence of the system function,and be extensively applied to the viscoelastic models with less parameters and better data fitting.The research in this thesis develops fractional models of the viscoelastic oscillator(VEO)and TTSP and analyzes their dynamic damping characteristic by taking VEO,the basic element of the dynamic analysis of the viscoelastic structure,as the study object,synthesizing the viscoelastic mechanical theory and the fractional derivative theory.The main research work in this dissertation is outlined as follows.The general dynamic modeling of FVEO considering the geometric factor and its numerical solution is developed,and three classical FVEOs are demonstrated.The VES installed in a certain type crawler vehicle is selected as the engineering case and modeled as FVEO with 2DOF to investigate its vibration damping effect and parameter influence.The results show that the history relation coefficient in the FVEO model of VES embodies the long range correlation of the viscoelastic material,and parameter including the geometric factor and the fractional order display notable influence on the vibration control effect.The frequency responses function(FRF,including amplitude-frequency characteristic and phase-frequency characteristic)of FVEO are derived according to the Laplace transform of the fractional calculus.Furthermore,the parameter influence on the FRF is discussed.The results show that there are harmonic peaks in the amplitude-frequency characteristic and corner frequencies in the phase-frequency characteristic,which are both affected by the system parameters.Fractional time-temperature superposition principle model(FTTSPM)of dynamic behaviors of the viscoelastic material is proposed,together with its experiment-based parameter identification.For application and comparison purposes,the master curve and nomogram of viscoelastic dynamic behaviors are constructed by FTTSPM and made comparison with WLF equation.To validate the theory models,the uniaxial tension test and DMA test are carried out to derive the stress-strain curves,dynamic temperature spectrum and frequency spectrum,respectively.The results demonstrate that the parameter of FTTSPM is physically defined and closely linked with test data,which allows better fitting of the master curve from FTTSPM to the theoretic one.On the other hand,the representation of the viscoelastic behaviors is simplified by nomogram through condensing the temperature and frequency relation to the 2D plane.This provides some theoretic reference for the research on aging,creep and long-term mechanical prediction of viscoelastic materials.To address the vibration hazard of a certain type of explosion proofing rubber-tyred vehicle,the tubular suspension with two constrained layers(TSTCL)possessing high structure loss factor is developed theoretically and experimentally.The validation experiment shows that the measured vibration level of the engine with TSTCL is obviously reduced.In particular,the RMS of the comprehensive vertical acceleration transformed to the seat in the cab is reduced by 65.13%,adequately validating the vibration control effect.In conclusion,the achievement in this dissertation can provide an innovative research approach for modeling and analyzing the complex viscoelastic damping structure and developing new high-performance viscoelastic materials and structures.