| Popis: |
Damping matrices have been formulated based on a simple model such as the proportional or structural damping when building a numerical model of a dynamic system. Such simple models, which were proposed largely for mathematical convenience, match only the overall effect of damping but ignore the actual mechanism or spatial distribution of damping. Motivated by the desire to obtain a more accurate damping matrix, various approaches have been proposed, which typically utilize some form of experiment. Among these methods, the dynamic stiffness matrix (DSM) based damping identification method is attractive because of its simplicity and generality. However, the damping matrices identified by the method were found to have unexpected forms, and also be heavily contaminated by experimental errors. Through numerical simulations and experimental work, the sources of experimental errors are identified and studied in this work. Based on the understanding obtained from the study, an improved experimental procedure is developed to minimize the errors involved in the DSM method. The test procedure is applied to two simple experimental cases to demonstrate the feasibility of the DSM based damping identification method. The development of the DSM based damping matrix identification method was motivated by the desire to apply it to building an experimental-analytical hybrid model by combining the damping matrix expanded from the experimentally identified damping matrix with analytically formulated stiffness and mass matrices. To enable this, two methods are developed to expand the experimental damping matrix to the size of the analytical model. A simple but effective method is developed to find the frequency range in which the matrix expansion is valid. As another important application of the DSM based damping identification method, the method is applied to the measurement of the property of viscoelastic materials. It is shown that how the method can be utilized to identify the structural properties of viscoelastic materials. |
