The Dynamic Characteristic Analysis Of The Sandwich Plate

As the hazards of vibration and noise are known, there is an active demand for damping and denoising. Viscoelastic material is one of the important methods of vibration and noise control, and especially it is fit for the control of wider frequency and multi-peak resonant vibration. Due to the wide use of viscoelastic material in engineering to control the vibration and the appearance of new viscoelastic material in recent years, the dynamic problem of viscoelastic complex structures becomes more and more important.As everyone knows, there are two different layouts of viscoelastic coating.one is free layer damping, another is constrained layer damping. The former dissipates the mechanical energy by the tension and compression deformation of viscoelastic material. The latter dissipates the mechanical energy by shearing deformation of viscoelastic material. And the latter can work better than the former in the effectiveness of vibration reduction. Theoretical analysis and numerical computation for dynamic characteristic of the sandwich plate with constrained damp layer are presented in this paper.In this paper, the authors briefly introduce the fundamental character, mathematical model, dissipation mechanics and the performance indices of weighing viscoelastic material. And the same time, the authors research the finite element dynamic equations of elastic structures and present the finite element dynamic equations of viscoelastic and elastic-viscoelastic structures in time domain. The end, the authors briefly introduce how to handle the damping when the elastic structures are be laid down viscoelstic material and several corresponding finite element methods. But maority of them regard the material characteristics of viscoelastic material as constants, which is not fit for time-temperature characteristics of viscoelastic material. So the conclusions drawn from them have more error. Although minor of them take into account the time-temperature characteristic, the methods are complicated and difficult to apply to complex sandwich structures.In the paper, the authors focus on finding a finite element method for computingthe natural frequency and loss factor in sandwich plate considering the time-temperature characteristics. As we known, the value of loss factor of viscoelastic material is equal to the ratio of dissipative modulus and storage modulus at some frequency. Based on ANSYS, we can get the natural frequency and loss factor in sandwich structures by modal strain energy iteration method and the validity of the method is verified. How the viscoelastic material boundary conditions, thickness, stiffness, level number to affect the natural frequency and loss factor is discussed in the paper, then some useful conclusions are drawn from them, which will give engineers a guideline to choice the optimum damping. The method can be used in large-scale and complex sandwich structures, and it can give an assurance of practicability and accuracy.