Research On The Defect Identification Of Beam Structure Based On The Dynamic Characteristics

Due to the negative effect of load,corrosion and aging of materials,structures inevitably appear defect accumulation,leading to the gradually decrease of the resistance,and then failure or destruction,severe cases may result in catastrophic tragedy.Therefore,it is of great theoretical significance and engineering application value to study the technology of structural damage identification,which is convenient and reliable.In this paper,the beam structure as the research object,by theoretical analysis and numerical simulation,the mutual relationship between structural detect and natural frequency is studied,and the effective identification of structural detect is realized.The main contents and innovations are as follows:Based on the structural perturbation theory,the relationship between the modal strain energy and the corresponding natural frequency change rate is established.By extracting the ratio of the natural frequency change rate which represent the structure detect,the characteristic vector and pattern vector are constructed,and then the single detect identification of beam structure is realized by using the pattern recognition technique;.The effectiveness of the proposed method is verified by numerical simulation and experiment with a single crack cantilever.By combining the structure element detect factor,the structural modal strain energy and the structure corresponding natural frequency change rate,the target function of multi detect identification is set up.Then,using the least square method to solve the target function and the multi detect identification of structures is realized.On this basis,in order to improve the accuracy of the method,from the point of reducing the number of structural detect units and increasing the frequency information,the finite detect method and the additional mass method are proposed respectively.Finite detect method is to establish the target function with only a small number of elements detect factor,using the nearest neighbor method as the classification principle,so as to realize the identification of multiple detect of the beam structure.The cantilever beam example and experimental results show that this method can achieve the identification of multiple detect of the beam structure with a small number of frequency information.Using the additional mass method to increase the frequency information of the structure,the target function is obtained by combining the frequency information of the original structure and the additional mass structure,and then the least square method is used to realize the multi detect identification of the structure;Using a symmetric beam as an example,the detect identification results show that the method is feasible and has better robustness.Based on the sensitivity analysis method,the relationship between the natural frequency change rate and the adding position of the added mass is established.Then,the principle of adding the additional mass is put forward,and it is applied to the additional mass method to enrich the inherent frequency information and improve the accuracy of multi detect identification.