Research On Structure Cracks Location Based On Time-Difference Of Arrival

In the long-term use or service of the structure, structure will produce microcracks due to various loading, environmental erosion, materials aging, fatigues. When the crack beyond a certain tolerance limit due to the slowly accumulation and spread. It’s prone to failure or damage and cause huge loss of life and property. Therefore, the real-time detection of crack initiation and propagation and taking measures to prevent or repair timely has a very important practical significance of engineering.The thesis comprehensively introduces the development summary of structural damage identification, the current identification and cracks detection, the current identification technology, basic damage identification methods and common damage index. For the problem considered in this paper, details of the acoustic emission theory, fractal principle and particle swarm optimization. Based on the time difference location principle, apply the fractal box dimension method to calculate fractal dimension of the crack propagation signals. Use the improved energy difference method to pick up the beginning time of the crack propagation signals automatically. According to the principle of crack location, crack orientation converted problem to the function optimization problems. Then the Particle swarm optimization(PSO) is applied to search for the optimal solution and obtain the positioning results.In order to verify the feasibility and applicability of the method, two experiments were carried out,the plexiglass verify experiment and concrete water fracturing experiment. The former experiment used a homogeneous plexiglass, the pencil break signal simulated crack propagation signals. Made several broken pencil test at three known coordinates, and obtained the location results finally. The results showed that this method is feasibility and the accuracy is good. The latter experiment was to press water into the concrete and produced cracks. Through the data that acquired to locate the position of the cracks. Through compared the experimental results and the photo pictures,the results can show the method is applicability in engineering.