Vibration Analysis And Optimization Of Sandwich Structure Treated With Viscoelastic Constrained Layer Damping

Viscoelastic damping materials for its large dissipation capability of vibrationenergy are widely used in the passive damping technology of automotive industry.Constrained layer damping (CLD) structure with viscoelastic core is a more efficientway in reducing and controlling vibration and noise of vibrating structure than freelayer damping treatment in which the damping material is either sprayed or bonded tothe structure. Due to the material properties of viscoelastic materials dependsignificantly on environmental condition such as temperature, vibration frequency andso on, the accurately modeling of damping composite structure has been the difficultyin engineering analysis. The author introduces the modal strain energy (MSE) methodto calculate the natural frequencies and loss factors of constrained layer dampingstructure, and applies “Genetic Algorithm”(GA) and evolutionary structural topologyoptimization (ESO) method to improve the design of damping treatment.Firstly, the important environmental factors affecting the dynamic properties ofdamping materials are analyzed and a mathematical model is developed to representthis behavior. Additionally the author uses ANSYS/APDL to build the constraineddamping structure and calculate the natural frequencies and loss factors based onmodal strain energy (MSE) method, by which the complex eigenproblem wassimplified to real eigenvalue problem. This method is available in analyzing anddesigning viscoelastic damping structure, which can be expected to approximate thecomputationally more expensive complex eigenvalue results.Secondly, considering the property of environmental and frequency dependencyof viscoelastic damping material, the modified modal strain energy iteration method,applying co-simulation of ANSYS and MATLAB is presented to model the lossfactor of constrained layer damping structure. In study of vibration characteristics theeffects of environmental conditions, structural design parameters and dampingtreatment type on natural frequencies and modal loss factors of CLD were analyzed.Calculation results show that the co-simulation method is flexible on the vibrationcharacteristics analysis and has a certain theoretical and practical significance onvibration damping technology.Thirdly, a multi-objective optimization model of CLD is established for CLDdesign parameters and solved by “Genetic Algorithm”(GA). The optimization objectives are maximizing each mode loss factor, minimizing each frequency shiftand reducing additional mass of damping treatment. Simultaneously the CLD startplacement, CLD treatment length, viscoelastic layer thickness and constrained layerare chosen as design variables. The coding is done in MATLAB optimization tool anddifferent optimization programs can be included. It is demonstrated that GAoptimization can be a powerful tool to further improve the design of dampingtreatment.At last, the sensitivity formula of modal loss factor to damping treatment elementis derived. Using evolutionary optimization method, the method and flow chart isestablished for damping material optimal placement and topology optimization ofconstrained damping structure. Building topology optimization program withANSYS/APDL parametric programming language, the topological configuration ofmaximum modal loss factor of constrained layer damping structure is obtained undercertain damping material volume constraint.The results show that environmental temperature，CLD layer thickness anddamping treatment type are important parameters that affect the performance ofvibration damping structure. Vibration analysis and optimization of CLD structurebased MSE meet the accuracy requirements of engineering analysis and have value inengineering...