Vibro-acoustics Characteristics Analysis and Suppression Research of Composite Sandwich Stiffened Plate Structure

Author:Fu Tao

Supervisor:yu hong ying

Database:Doctor

Degree Year:2019

Download:68

Pages:185

Size:3664K

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Plate structure is the main component of high-speed train,aircraft and ship and other transport equipment.Due to the diversity of the application background of transport equipment,it is often in a complex environment of high-low temperature alternation,structural vibration and induced noise during operation.When the thermal stress caused by thermal load reaches a certain value,the structure will undergo thermal buckling,and the strong vibration will aggravate the sound source straightness in the cabin.Acquisition noise and aero-elastic coupling effect between external flow fluid and structure will adversely affect the safety of delivery equipment and the suppression of vibration and noise in cabin.Therefore,it is of great significance to study the sound and vibration characteristics of plate structures under complex external environment,to achieve broadband sound and vibration suppression of structures,and to make them have light weight,heat insulation,low vibration and high sound insulation performance for improving the safety and comfort of transport equipment.In this paper,the acoustic-vibration coupling characteristics of composite sandwich ribbed plate structure under external flow field and heat source are studied.The effects of theoretical model of sandwich plate,heat source environment,external uniform fluid,material distribution type and passive vibration suppression control in broadband domain on the acoustic radiation response and sound insulation characteristics of the structure are analyzed theoretically and experimentally.Specific research contents are as follows:Based on the classical sandwich plate theory,the thermal stress is introduced into the thermo-elastic constitutive equation of sandwich structure.The linear temperature field with and without heat source is considered.The transverse vibration displacement of sandwich plate under thermal load is solved by means of double trigonometric series solution.Based on the radiation element method and considering the influence of coupled radiation impedance,the Rayleigh integral equation is derived.The radiated sound power of sandwich plate under thermal load is given,and the formula for calculating sound transmission loss of sandwich plate structure under plane acoustic wave excitation is derived.The validity of the model is validated by comparing with the existing theoretical models and experimental results.At the same time,based on the theoretical model,the effects of different temperature field load parameters on natural frequencies,sound radiation and sound insulation characteristics of sandwich panels are emphatically analyzed.In view of the periodic distribution of sandwich sandwich with three-dimensional light-weight lattice,a three-dimensional lattice sandwich stiffened plate vibration modelis established.The influence of the flexural rigidity of the surface plate and the two-parameter foundation model are taken into account in the model.The coupling effect between the plate and the stiffener is solved by displacement compatibility condition,and the influence of thermal moment is ignored.The critical buckling temperature of sandwich plate in uniform temperature field is derived.The effects of two-parameter elastic foundation and sandwich structure parameters on the natural frequency and critical buckling temperature of sandwich plate are analyzed.The variation rules of structural acoustic radiation and sound insulation characteristics with different sandwich types,material loss factors,sandwich parameters,elastic foundation and temperature loads are given.It is found that compared with Winkle stiffness,the effect of shear stiffness on sound radiation and sound insulation of structures is more significant.Based on the Reddy high-order shear deformation theory and Hamilton variational principle,the vibration control equations of laminated functionally graded composite plates under combined action of thermal environment and two-parameter foundation model are derived.The governing equations under different boundary conditions are solved numerically by differential quadrature method.The temperature loads,boundary conditions,elastic foundation parameters and material laying under dimensionless conditions are investigated and analyzed.The effects of setting angle and mode,number of layers,material distribution type and thickness-to-edge ratio on the bending disturbance and natural frequency of FGM laminates can lay a foundation for the analysis of sound radiation and insulation characteristics of FGM laminates in subsequent thermal environments.Aiming at the three-dimensional lattice sandwich stiffened plate structure with composite material on the surface,based on the vibration equation of the laminated functionally graded composite plate,the equivalent structural impedance of the composite plate is obtained by differential quadrature method,the lateral vibration displacement of the structure under thermal load is solved by the form of double triangular series solution,and the structure is solved by the velocity continuity condition of the fluid-structure interface.By using Rayleigh integral,the radiated sound power and transmission loss of the structure under the action of external uniform fluid are derived respectively.Based on the theoretical model,the effects of different volume fraction,material laying angle and mode,layers and material distribution types on sound radiation and sound insulation characteristics of structures are analyzed.Based on the vibration equation of composite sandwich stiffened plate structure,the transverse vibration displacement of composite sandwich stiffened plate structure with distributed dynamic absorber is theoretically deduced and solved by addingmultiple single-degree-of-freedom dynamic absorbers.The damping ratio,natural frequency ratio,mass ratio and installation position are analyzed.The optimum values of damping ratio,natural frequency ratio,mass ratio and installation position parameters of dynamic vibration absorber are determined.A beam dynamic vibration absorber is designed in the experiment.The validity of the model is verified by comparing with the experimental results.The effects of the additional distributed dynamic absorber on the sound insulation characteristics of the composite sandwich ribbed plate structure are compared and analyzed by experiments.The results show that the beam-type distributed dynamic absorber designed in this paper improves the sound insulation curve of the composite sandwich ribbed plate structure greatly,and its maximum increase is over 20 dB.Compared with the original structure,the sound insulation characteristics of the composite sandwich ribbed plate structure are improved in a wide frequency range.The research in this paper can provide theoretical basis for the design of material composition and structure form of plate sound insulation structure,and the theoretical model can be used to guide the design of broadband sound and vibration suppression of sound insulation structure.