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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.

Synthetic aperture focusing ultrasound imaging technique used signal processing method to analysis ultrasonic echo data. It let the performance of transducer with small apertures be as well as the transducer with large aperture. It can still obtain high azimuth resolution image and form three-dimensional image, when it was operated at lower operating frequency. This paper describes the history and the theory of synthetic aperture focusing ultrasound imaging technology. It also contains the development of the synthetic aperture focusing ultrasound imaging technology in China and at abroad. And lots of excellent synthetic aperture focusing ultrasound imaging algorithms were listed in this paper. We analyzed the deficiencies and problems of the existing ultrasound focusing algorithms. And we made forecast about the development of synthetic aperture technology in nondestructive testing.

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.

In this paper, we consider the global error bound for the generalized complementarity problem (GCP) with analytic functions. Based on the new technique, we establish computable global error bound under milder conditions, which refines the previously known results.

Introduced the history of development of crack damage detection technology and summarized the current state of damage detection technique based on modal analysis. Finite element method is the main method for mechanical structure modal analysis at present. Many researchers studied a single crack or multiple cracks impact on different structure’s dynamic characteristics, however, these studies only limited to the current state of structures with damage. Considering damage extending when mechanical structure being on work, a new method combines modal analysis and theory of damage extend is proposed to analysis the extending trend of damage, which make it easy to assess remaining life of mechanical structures and make structures that meeting design life can still being on work before they lose their effectiveness, this can save lots of costs

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.

The steel rod is an important part for project fields , and it is large-scale to be used. it is apt to crack, corrosion and so on in the poor working conditions. In order to recognize correctly the type of defects, a method was presented to extract frequency band energy feature by using wavelet package decomposition. In the meantime, to extract the peak-peak value in the time-domain and make the mixed feature vector. With the way of pattern recognition, the best recognition way was got by comparing the BP artificial neural network(ANN), PNN(probability neural network) artificial neural network and "one-versus-one" support vector machine(SVM).The result showed that the recognition rate of SVM was more suitable for defects’ identification in steel rod.

In this paper, we establish a error bound for the generalized linear complementtarity problem in engineering modeling(GLCP)which can be viewed as extensions of previously known results, based on which the famous Levenberg-Marquardt (L-M) algorithm is employed for obtaining its solution, and we show that the L-M algorithm is quadratically convergent without nondegenerate solution which is a new result for GLCP.

This paper addresses the generalized linear complementarity problem (GLCP) over a polyhedral cone. To solve the problem, we first equivalently convert the problem into an affine variational inequalities problem over a closed polyhedral cone, and then propose a new type of method to solve the GLCP based on the error bound estimation. The global and R-linear convergence rate is established. The numerical experiments show the efficiency of the method.

Sucker rod is the hey component for the rod pumping system. In the working process, there are mainly four kind of defects: cracks, corrosion, partial wear and artificial damage, which will cause downhole accidents, so feature extraction is a premise to distinguish different defects. In the paper, by using wavelet energy spectrum, sucker rod defects signals that came from magnetic flux leakage (MFL) detection method are decomposed to the different frequency bands by arbitrary time-frequency resolution, the frequency signal energy is an eigenvectors to judgment sucker rod defects. In practice, the detection method is effective and feasible, and there is a new way for the sucker rod defects pattern recognition.