The potential of using topology optimization as a tool to optimize the passive constrained layer damping (PCLD) layouts with partial coverage on flat plates is investigated. The objective function is defined as a combination of several modal loss factors solved by finite element-modal strain energy (FE-MSE) method. An interface finite element is introduced to modeling the viscoelastic core of PCLD patch to save the computational space and time in the optimization procedure. Solid isotropic material with penalization (SIMP) method is used as the material interpolation scheme and the parameters are well selected to avoid local pseudo modes. Then, the method of moving asymptote (MMA) is employed as an optimizer to search the optimal topologies of PCLD patch on plates. Applications of two flat plates with different shapes have been applied to demonstrate the validation of the proposed approach. The results show that the objective function is in a steady convergence process and the damping effect of the plates can be enhanced by the optimized PCLD layouts.
Particle filter (PF) is usually used for identifying structural parameters in nonlinear systems. However, the traditional PF method requires that all the external excitations are available or can be measured, which may not be the case for many structures. In this paper, a modified PF method with unknown inputs, referred to as PF-UI, is proposed to identify the augmented states, including structural states and parameters, as well as the unknown excitation inputs.The augmented states are identified by the traditional PF algorithm, and the unknown excitations are simultaneous identified with the least-square algorithm. Such an analytical solution for PF-UI is not available in the previous literature. Numerical studies of two typical nonlinear systems are conducted to demonstrate that the proposed approach is capable of identifying the states and parameters with unknown excitation inputs.
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