Research On The Optimal Sensor Placement Of The Bar For Crack Damage By Modal Identification

Bars, which are widely used in practical engineering, are the basic component unit of large structures, and many will appear cracks in the work process. Due to the early initial crack is not easy to be found, the crack expansion will cause the destruction of the whole structure, and even lead to a major accident, therefore, it is an important research direction to rapidly forecast the position of the early cracks in the field of damage identification. For bars with large aspect ratio, the traditional method of non-destructive testing test has the shortcomings of a long test time and the complex operation, thereby dynamical methods based on modal have been widely used, while, the test results of this method mainly depend on sensors arranged on the structure, therefore, it has important practical value and research significance to select the best number of sensors, and arrange them in the optimum position of the steel bar. In this paper, optimal sensor placement calculation of bars is researched by using different optimal methods based on theoretical modal analysis, and thus the best number and position of sensor are obtained. The efficiency and practicality of optimal sensor placement scheme in crack damage identification are verified through experimental modal analysis. This study provides non-destructive monitoring of dynamic and complex structures with a theoretical basis and practical application foundation. The main contents of the paper are as follows:(1)Firstly outline the research status of optimal sensor placement, introduce the domestic and foreign research status of comparison criteria of optimization and optimal sensor placement based on different methods, and describe the theoretical model of vibration system of modal analysis and the principle of optimal sensor placement.(2)Build and analyze the modelings of different bars based on ansys finite element analysis, and program calculations based on MATLAB software; get the best optimal sensor placement methods for bars based on the standards of the minimum MAC value and the minimum MSE value, and determine the optimal number and location of sensors for bars.(3)Built the vibration test bench, carry out the vibration experiment of the bar based on optimal sensor placement and modal analysis for experimental data, verify the optimization results of optimum sensor layout programs through contrasting the theoretical and experimental modal data.(4)Conduct cracke damage identification of bars based on optimal sensors placement, and compare with the recognition results of before optimization, prove that optimization layout scheme has advantages of identifying signal obviously and high efficiency in damage identification.