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• The method is suitable for the steel strands of in-service structures. • The prestress of the inside steel strands could be measured outside the structures. • The resistance-prestress relationship is nearly linear. • The average relative errors are about 10%. • The proposed method is suitable for long prestressed steel strands. To test the prestress of internal prestress steel strands, the relationship between the resistance and the prestress was analyzed. The equivalent electrical models of the testing systems were established. The results of the prestress testing experiments showed that there was a nearly linear relationship between the resistance and the prestress. Steel strands with similar physical properties had similar resistance-stress relationships that were not influenced by the prestress variation. Connecting both ends of the steel strand to the testing circuit, the prestress of the inside steel strands could be measured outside the structures. Both in the structural construction phase and the operation phase, the prestress testing errors were about 10%. When testing long steel strands, the proposed method may have higher sensitivity and smaller errors. [ABSTRACT FROM AUTHOR]

Scanning electromagnetic induction thermography (SEIT) has great potential for industrial applications, such as rapid visualising of surface cracks. This dynamic non-destructive testing method has improved detection efficiency but has led to blurred or discontinuous defect boundaries at varying scanning speeds. To alleviate this problem, we explore the use of the patch-based sparse decomposition (PSD) technique. This technique improves dynamic imaging by retaining only the information associated with sparse regression and introducing a locally adaptive threshold. Besides, this method offers a potential thermal image preconditioned scheme for follow-up artificial intelligence detection. Experimental results show that PSD can correct blurred images caused by relative motion, thus improving defect detection accuracy. Moreover, it is suitable for both translational and rotational detection systems. Images reconstructed through the deblurring process demonstrate the ability to visualise holes with a radius of 0.5 mm at velocities up to 150 mm/s, while cracks with a defect width of 0.2 mm on a railroad wheel can be detected at speeds ranging from 25 mm/s to 75 mm/s. [ABSTRACT FROM AUTHOR]

In an actual structure, the arrangement of steel bars is complicated, there are many factors affecting the corrosion of steel bars, and these factors affect each other. However, accurately reflecting the corrosion of steel bars in actual engineering through theoretical calculations is difficult. Besides, it is impossible to detect and evaluate steel bars rust completely and accurately. This article is based on spontaneous magnetic leakage detection technology and adopts the method of stage corrosion and scanning along the reinforcing bar. Based on spontaneous magnetic flux leakage detection technology, the linear change rate of the tangential component curve of the magnetic flux leakage signal generated after the corrosion of a steel bar is studied, and a comparison is made between the steel bar coated concrete samples with different steel bar diameters. In this paper, the "origin of magnetic flux leakage signal" is defined as a reference point, which is convenient for effectively comparing the magnetic signal curves under all operating conditions. Besides, the "rust-magnetic fluctuation parameter" is proposed to accurately reflect the sudden change of leakage magnetic field caused by disconnection due to the corrosion of a steel bar. A new data processing method is provided for the non-destructive testing of steel corrosion using the spontaneous magnetic flux leakage effect, which can effectively reduce the influence of steel bar diameter on magnetic flux leakage signal and improve the precision of non-destructive testing technology of steel bar corrosion using the metal magnetic memory effect. [ABSTRACT FROM AUTHOR]

The non-destructive quantitative evaluation of the rebar corrosion degree is an urgent problem to be solved for corroded reinforced concrete structures. In this study, a non-destructive quantification method for the rebar localized corrosion cross-sectional area was proposed based on the dynamic linkage mechanism of the induced magnetic and self-magnetic flux leakage fields of rebar. As verified by data from the experiment and the finite element simulation, this quantification method could eliminate the adverse influence of the magnetic property differences of the rebar. The results indicated that different quantitative indices for corrosion evaluation could be created based on this method, and an index created by two transformations with the same geometric characteristics had better quantification capability. The four quantitative indices I 1 , I 2 , I 3 , and I 4 created in this study were all linearly related to the rebar localized corrosion cross-sectional area ratio S , and index I 3 had the relatively best quantitative capability and applicability. This quantification method provided an innovative solution for the non-destructive quantitative evaluation of rebar corrosion. • The dynamic linkage mechanism between the IM and SMFL fields of corroded rebar was demonstrated. • An SMFL-based non-destructive quantification method for the rebar corrosion degree was proposed. • Four quantitative indices were created based on this quantification method. • All of the created quantitative indices were linearly related to the corrosion cross-sectional area of rebar. [ABSTRACT FROM AUTHOR]