Investigation On The Design Of Dynamic Vibration Absorber For Vibration And Noise Control Of Thin-Walled Structures

Thin-walled structures are widely used in rocket,aircraft,automobile,high-speed railway and ship structures due to their features of high strength-to-weight ratio,low cost and strong integrity.However,due to its low out-of plane stiffness and small damping,the modes of the thin-walled structure are very dense and the acoustic environment is very harsh.Harsh acoustic environment can lead to fatigue which will potentially reduce its service life,and lead to equipments malfunction.Therefore,it is necessary to conduct research of sound and vibration control of thin-walled structures.Traditional vibration and noise reduction structures,such as attaching damping layer,porous materials,can effectively absorb the response within the middle and high frequency range,but they have little effect with respect to the low frequency response.The dynamic vibration absorber(DVA)is widely used to suppress the low frequency response due to its simplicity in structure,low cost and high absorption effect.However,the existing design methods of dynamic vibration absorber is only applicable to the structure with sparse mode,and it can not be used to the thin-walled structure with dense mode.To solve the aforementioned problems,design method of dynamic vibration absorber suitable for thin-wall structure with dense mode is studied in this paper.The detailed work is as follows:To solve the problem that existing dynamic vibration absorber design method is difficult to apply to the thin-wall structure with dense mode,a new design method based on the basis transformation in the modal space is proposed to optimize the dynamic vibration absorber,which can reduce the optimization of dynamic vibration absorber from multiple dimension to one dimension.Then,with the new relationship developed between the DVA design of a single-mode primary system and that of an SDOF primary system,the commonly used fixed-points theory or min-max optimization method can be directly adopted to obtain the optimum parameters of DVA for the sound and vibration suppression.The optimal position of the dynamic vibration absorber should be the maximum amplitude of the reduced Excitation-Structure mode(ESM).Results show that the proposed design method can effectively suppress the sound and acoustic response of thin-walled structures in broad band.In engineering practice,it is difficult to obtain the accurate information of excitation and structure,which will significantly effect the proposed design method.The response of structure actually packs the information of both excitation and structure,therefore,a response-driven dynamic vibration absorber design method for thin-walled structures was proposed.Based on singular value decomposition(SVD),modal parameters can be obtained to finish the optimization of DVA by the use of above-proposed DVA design method.Optimal position and material parameters can be therefore obtained only based on the response data.Results show that the proposed response-driven design theory can effectively reduce the response of structure in broad band by the use of only a few dynamic vibration absorbers.The proposed theory also has strong robustness to noise.Finally,for a certain type of composite fairing model,the proposed design method was applied to the engineering.The equivalent modeling of Nomex paper honeycomb was first established based on honeycomb plate theory to establish the mechanical and acoustic equivalent model of the fairing.Then,the optimization design of vibration and noise reduction of dynamic vibration absorber is conducted based on the equivalent fairing model.Results show that the proposed equivalent modeling method can greatly reduce the model complexity without the cost of precision.The optimization theory of dynamic vibration absorber proposed in this paper can effectively suppress the acoustic and vibration responses of the composite fairing.