Search

The traditional identification method of surface crack has some shortcomings such as detection equipment complex, high requirements for operator and not suitable for large-scale structure inspection, vibration method is applied to identify surface crack in steel rods in this paper, using the method of calculating modal analysis combined with time-frequency wavelet analysis. The research on damage identification is performed on steel rods with different deep crack. The research results show that the accurate damage location can be judged by wavelet modulus maximum and the quantitative analysis of single crack identification can be achieved by constructing mathematical expressions of a single crack damage degree and damage index Lipschitz index. The research would province some guidance for engineering applications.

When conducting modal analysis to the structure with crack defect using ansys finite element, we usually adopt the method of cutting a rectangular notch to simulate the crack on the model structure. As a result, the different crack simulation requires repeated modeling, which is a waste of time, and we cannot guarantee the accuracy of the calculation. In this paper, mathematical model between the local stiffness and crack size is established based on the finite element simulation of a diameter of 8mm steel bar. Thus, we can simulate varisized crack defects through a fixed crack notch by the method of modifying local stiffness. The method we used is more simple and accurate than the traditionary one by cutting a rectangular notch to form cracks, and reduces the workload, and has certain research significances.

Steel rods are widely used in the areas of petroleum, chemical, architecture and transportation, steel rods with cracks will cause terrible accident and great losses when working in production practice. In view of traditional Non-destructive Testing (NDT) method can only realize static detection, this paper provide the method based on modal calculate analysis, including the choice of damage index and the judgment of damage degree and damage location for cracks of steel rods. The damage location is judged by the strain mode shape difference curve and the function expression of damage degrees and mutation degrees of curvature mode shapes is acquired by the method of least square fitting, which can achieve quantitative analysis of single crack of steel rods, this provide theoretical support and technical reference for experimental modal analysis and dynamic NDT.

This article describes the history of the development of structural damage, and an overview of current research status at home and abroad based on modal analysis of structural damage identification, reviewed in recent years the structure of the early damage recognition technology, from the application point of view of definition of indicators and indicators on the current some indicators of a comprehensive analysis and evaluation, further analysis of the feasibility of several modes of indicators to identify structural damage diagnosis, pointing out that the modal parameters of structural indicators to the validity and accuracy of damage identification and the need to further address the problem. The research will provide a reference for the application of modal analysis method to detect structural damage diagnosis in order to ensure early discovered the damage and accurately identify the site of injury repair in a timely manner.

During bars manufacturing and using process, the use of bars with cracks influenced the service life and sustainable work, on the premise of certain detection system, the choose of signal de-noising method plays an important part in magnetic flux leakage testing process, for which determining the global performance of testing equipment. This paper studies on magnetic flux leakage signals characteristic of cracks on the bar, analyzed the advantages and disadvantages of wavelet analysis and wavelet packet threshold de-noising, and on this basis, in order to give consideration to both the low and high frequency interference signal removing, adopted an integration method that combines wavelet packet threshold de-noising, wavelet packet decomposition and wavelet reconstruction, which greatly improved signal processing results.