Research On The Energy Transmission Characteristics Of Coupled Structures

In the key engineering fields such as aerospace and transportation,the problem of high frequency vibration of coupled structures has become increasingly prominent.When using the Statistical energy analysis,Energy finite element method or radiation energy transfer method to solve the high-frequency problems,the energy interaction between subsystems is a key problem that must be solved.In the statistical energy analysis,the energy transmission coefficients are the key for calculating the coupling loss factor;in the energy finite element method,the coupling matrix is established by the energy transmission coefficients;in the radiation energy transfer method,the energy transmission coefficients are used to determine the virtual sources at the coupling boundaries.Most of the current researches focus on coupled beams,coupled plates,and beam-plate coupling,and the research on plate-shell coupling systems dealt only the isotropic materials.The coupling system of laminated structures has not been involved yet and needs to be developed urgently.Based on previous theories,first of all,this dissertation will conduct a detailed revisit to the energy transmission analysis methods of one-dimensional coupled beam structures,and then review those of two-dimensional isotropic plate-shell coupled struc-tures.On this basis,based on the Classical laminated plate theory(CLPT),we solve the energy transmission characteristics of the composite laminated plate-shell coupled sys-tem.Finally,based on the First-order shear deformation theory(FSDT),we discuss the energy transmission characteristics of the composite laminated plate-shell coupled systems.The main research content is:(1)Energy transmission analysis of one-dimensional coupled beam structuresBased on the Euler-Bernoulli hypothesis,first of all,we review the free vibra-tion analysis methods of isotropic beams and composite laminated beams considering tension-bending coupling.Then we derive the formulae of common coupling struc-tures such as coaxial coupled beams,bifurcated beams and branch beams.The energy transmission coefficients of one-dimensional structures and the calculation formulae of the coupling loss factor are given.Finally,the influences of the beam cross-sectional area ratio,excitation frequency,coupling angle,and layering angle on the energy trans-mission coefficients and coupling loss factors are discussed.It is verified that CLF and modal density satisfy the reciprocity principle in SEA.(2)Energy transmission analysis of laminated plate-shell coupling structures based on CLPTBased on the review of the energy transmission solution process of the isotropic plate-shell coupled structures,the energy transmission coefficient and the coupling loss factor of the composite laminated plate-shell coupled system are obtained according to the Snell law of refraction and reflection of the waves,the continuity of displacements and the force balance conditions at the coupling boundaries.By comparing with the literature,we demonstrate that the energy transmission coefficient satisfies reciprocity and energy conservation relationships,which verifies the correctness of the theoreti-cal formulation in this dissertation.Finally,the influence of parameters such as laying method,laying angle,coupling angle and excitation frequency on the energy transmis-sion characteristics is discussed.(3)Energy transmission analysis of laminated plate-shell coupling structure based on FSDTBased on the FSDT,the equilibrium differential equation of laminated cylindrical shell(plate)is derived,and the dispersion curve of the circumferentially open laminated cylindrical shell is calculated and compared with related literature,which verifies the correctness of the theoretical derivation.Then,the flexural wave,shear wave and longi-tudinal wave are respectively set as incident wave,the energy transmission coefficients of the laminated plate-shell coupling structure with respect to the incidence angle are calculated,and the necessity of introducing FSDT is analyzed.Finally,by changing the material thickness,and by comparing the differences between the CLPT solution and the FSDT solution,the law of the transmission of the three incident waves is summarized.