Identificaiton Of Impact Force And Location On Composite Structure

After the impact happens, identifying the impact location and reconstructing the impact force history timely and quantitatively play a very important role in the research of composite structural health monitoring. This dissertation studies methods and techniques about impact identification in structural health monitoring of composite structures. These techniques can detect the impact events in/near real time, identifying the impact location and reconstructing the impact force history actively. The main contents of this dissertation are as follows:The impact location identification problem for composite structures is studied, based on an intelligent optimization algorithm called immune genetic algorithms (IGA). First, after obtaining a set of impact-induced stress wave signals from pre-determined impact tests, wavelet transform is applied to analyze these stress wave signals in the time-frequency domain to obtain the propagation velocity of the impact-induced stress waves in the composite structures. Then, considering the anisotropic properties of stress wave propagation in composite structure, IGA is employed to identify the location of unknown impact. After locating the impact on the composite structures, a method used to reconstruct the impact force history based on the ARX model is proposed. First generating a mesh division on the surface of the composite structure, then training the model on every node and obtaining the system parameters by applying the system identification theory, so the composte model could be equivalent to ARX model comprised of system parameters on state-space expression. After that,the reverse relation between the input and output of the ARX model could be reduced, which is used to form a set of reverse transfer function matrix. Finally, the input singal of the impact on arbitrary location could be reconstructed based on output singal by the matrix set and isoparametric element theory. Experimental and Numerical simulation results have demonstrated the applicability and effectiveness of two methods mentioned above separately.Experimental studies on a stiffened composite panel is performed to validate the accuracy and effectiveness of the impact identification system, the results demonstrate:the algorithm is simple, the process of the method is clear and reasonable, the identification result is accuracy.