The Stiffness Identification Method Of FRP Laminated Beam And Plate Based On Strain Mode

The dissertation came from the central university special funding for basic scientific research business expenses “Composite materials and structural damage inversion study based on adaptive hybrid genetic algorithm ”(No.2014-Ia-036).This dissertation is to identify the stiffness of beam and plate which are made of glass fiber reinforced plastic(FRP) based on strain mode. The problem is solved by ANSYS software, while the inverse problem is based on improved genetic algorithm program through MATLAB software. We combine the simple search with traditional adaptive genetic algorithm to increasing the speed of convergence and avoid being trapped in local optimal solution. The Specific research contents are as follows:1. Getting the theoretical formula of cantilever beam which is damaged. And doing strain mode experiment of cantilever beam. We attach an additional mass on an element of cantilever beam to simulating the damage. Identifying the element stiffness on both two conditions whether it has an additional mass or not. And then checking the results by the finite element method. The experimental results show that strain mode is very sensitive to element damage. And it can accurately identify the damaged position. The element stiffness identified by improved genetic algorithm keep high coherence with finite element method results.2. Doing strain mode experiment of cantilever FRP plate, achieving the longitudinal strain mode. And then identifying the element stiffness on the basis of experiment results. Comparing the improved genetic algorithm and unimproved genetic algorithm on the recognition performance. Then we study the relationship between the size of element and recognition performance. The results show that the improved genetic algorithm is more accurate and has a less number of iterations than unimproved genetic algorithm. And if the element size is smaller, we can achieve more accurate results. But this may cause more work in practical engineering to get global information of the structure.3. Doing numerical simulation experiment on cantilever FRP plate and achieving the strain mode. We change the horizontal and vertical stiffness of some elements,and identify the stiffness on the basis of the strain mode in longitudinal and 45 °direction. Comparing the two methods and studying the relationship between thesensitivity and recognition accuracy. At last, we identify the stiffness of different elements which have different extent of damage. It find that the results is the best when identifying is based on first strain mode in 45°direction. And if the strain mode is more sensitive to damage, the results are more accurate. At last we achieved accurate results of different elements which have different extent of damage on the basis of strain mode in 45°direction. Also it has no relationship between the number of damaged elements and the speed and accuracy of iteration.