A new approach is proposed for automatically detecting crack defects with dark colors and low contrasts in magnetic tile images using the fast discrete curvelet transform (FDCT) and texture analysis. In this methodology the original images were first decomposed and reconstructed based on the FDCT. Then the thresholds of decomposition coefficients were calculated by texture feature measurements. With these thresholds the surface textures in the images can be eliminated. Finally by extracting contours from the reconstructed images, the expected images without textures but with crack defects contours were obtained. Experimental results show that the proposed method could eliminate the contours of the textures, and extract from the image cracks longer than 0.8 mm.

Detection of surface crack defects on ferrite magnetic tile

An automatic system is developed for internal cracks detection in magnetic tiles based on the impact acoustics, using wavelet packet transform (WPT), principal component analysis (PCA) and hidden Markov model (HMM). In this system, the detecting device is considered as core part to collect and analyse the impact sounds. The original impact sounds are first decomposed up to six levels based on WPT to extract the features. PCA is then performed for dimension reduction and clustering analysis. By adopting the features extracted based on WPT and optimised by PCA as inputs, an HHM classifier is developed for automatic inspection. The results of classification show that the accuracy rate is 100%, demonstrating that the system has significant potential in detecting magnetic tile internal cracks.

Inspection of magnetic tile internal cracks based on impact acoustics

A visual automatic detection method is proposed for defect detection on end surface of ferrite magnetic tile to tackle the disadvantages generated by human work which has low efficiency and unstable accuracy. Because the defects on end surface of ferrite magnetic tile with dark colors and low contrasts are negative for defect detection, uniform illumination is provided by LED light source and a dedicated optical system is designed to extract defects conveniently. The approach uses comparison of the fitting and actual edge curves to detect defects mainly with most defects located on the edge. Firstly improved adaptive median filter is used as the image preprocessing. Subsequently the appropriate threshold is calculated by Otsu algorithm based on the extreme points in the gray-level histogram to segment the preprocessing image. Then the Sobel operator can be used to extract the edge of end surface precisely. Finally through comparing the ideal fitting and actual edge curves of end surface, to detect the defects with some relevant features. Experimental results show that the proposed scheme could detect defects on the end surface of ferrite magnetic tile efficiency and accurately with 93.33% accuracy rate, 2.30% false acceptance rate and 8.45% correct rejection rate.

Defect detection for end surface of ferrite magnetic tile

Abstract. For the analysis of the quality of metallurgical products, it is important to use techniques that identify the internal and external unconformity of the product without destroying it. These techniques are non-destructive testing (NDT). Although these techniques identify the unconformity of the product, they do not indicate the source of their creation. The purpose of the study was to develop a hybrid method to make decisions about the causes of product incompatibility. This hybrid method was created as a combination of NDT and quality management techniques, i.e.: 5W2H method, Ishikawa diagram, 5Why method. The subject of the study was an unconformity detected in the tube made of the magnesium alloy AMS 4439. Research was carried out using the FPI method. In the analyzed case, its application allowed the detection of a linear indication in the product. To identify the root of the linear indication, the 5W2H method, the Ishikawa diagram, and the 5Why method were used sequentially. The main causes were bad casting and pollution. The root cause was defective supplier material. Integration of the FPI method, the 5W2H method, the Ishikawa diagram, and the 5Why method in the performance of a comprehensive qualitative analyze of products, after which it is possible to identify the unconformity and the root of its occurrence. The integration of FPI and quality management techniques can be practiced to analyze the quality of products (including metallurgical products) in manufacturing and service enterprises. 

pdf/development-of-a-hybrid-method-for-identifying-the-causes-of-4d2gx5v5dq.pdf

Development of a Hybrid Method for Identifying the Causes of Product Incompatibility in Metallurgical Manufacturing

Fatigue cracks are typical damage of threaded steel rods under dynamic loads. This paper presents a study on ultrasonic guided waves-based, fatigue-crack detection of threaded rods. A threaded rod with given sizes is theoretically simplified as a cylindrical rod. The propagation characteristics of ultrasonic guided waves in the cylindrical rod are investigated by semi-analytical finite element method and the longitudinal L(0, 1) modal ultrasonic guided waves in low frequency band is proposed for damage detection of the rod. Numerical simulation on the propagation of the proposed ultrasonic guided waves in the threaded rod without damage shows that the thread causes echoes of the ultrasonic guided waves. A numerical study on the propagation of the proposed ultrasonic guided waves in the threaded rod with a crack on the intersection of the smooth segment and the threaded segment shows that both linear indexes (Rf and ARS) and nonlinear indexes (βre′ and β′) are able to detect the crack. A constant-amplitude tensile fatigue experiment was conducted on a specimen of the threaded rod to generate fatigue cracks in the specimen. After every 20,000 loading cycles, the specimen was tested by the proposed ultrasonic guided waves and evaluated by the linear indexes and nonlinear indexes. Experimental results show that both the linear and nonlinear indexes of the ultrasonic guided waves are able to identify the crack before it enters the rapid growth stage and the nonlinear indexes detect the crack easier than the linear indexes.

/pdf/crack-detection-of-threaded-steel-rods-based-on-ultrasonic-pliss7mu.pdf

Crack Detection of Threaded Steel Rods Based on Ultrasonic Guided Waves

The design of an automated unit for magnetic fluorescent-penetrant inspection of end faces of pipes in in-line production is described. The structural diagram of the unit is given. The problem of measuring the magnetic field induced by the unit is considered. A procedure for the preparation of a reference specimen required for checking the work capability of the unit is described.

Increasing the Reliability of Magnetic-Particle Testing by Means of a УМЛК-10 Automated Unit for Magnetic Fluorescent-Penetrant Inspection of Pipe End Faces

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Increasing the Reliability of Magnetic-Particle Testing by Means of a УМЛК-10 Automated Unit for Magnetic Fluorescent-Penetrant Inspection of Pipe End Faces