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Multi-wire cables are widely used in suspension bridges and cable-stayed bridges as primary load bearing structural elements. Broken Wires in cables can lead to catastrophic accidents such as bridge collapse. Magnetostrictive guided wave testing technology has been employed to detect the broken wire defects in multi-wire cables, and the defect size is estimated by analyzing the defect echo signals. However, there are many studies on the guided wave testing for the seven-wire steel strands but fewer for the bridge cables which have a large number of wires. Moreover, the relationship between the guided wave testing signal features and the defect size of multi-wire structures is imprecise, which means the defect size estimated by the features may deviate significantly from the real defect size. In this paper, large-scale topological features are extracted by using persistent homology from the dynamical reconstruction topology of the guided wave testing signals to characterize broken wire defects in the bridge cable. The broken wire experiments were performed on a 61-wire cable. The experimental results show a good linear relationship (the goodness of fit 0.9946) between the large-scale topological features and the number of broken wires in the cable. It indicates that it is feasible to extract topological features from the topological domain of the testing signals to characterize the broken wire defects of bridge cables. [ABSTRACT FROM AUTHOR]

According to the requirements for the beam collimation system of the rapid cycling synchrotron (RCS) of China Spallation Neutron Source (CSNS), the main structure of a scraper of primary collimator is made by W/Cu brazing, in which the thickness of tungsten slice is 0.17 mm. In order to get the best mechanical properties, the brazing temperature is suggested to be controlled under the recrystallization temperature of tungsten, while the recrystallization temperature is affected directly by the thickness of tungsten. Because of little research and application on the brazing of thin tungsten slice of 0.17 mm and copper, tensile tests are done to get the mechanical properties of tungsten slices which experience different brazing temperatures. In keeping the inner relationships between the mechanical properties and temperature, another experiment is done by using SEM to scan the microstructures including the size and distribution of crystals. Finally we determine the recrystallization temperature of tungsten slice of 0.17 mm, and get the best parameters of W/Cu brazing for scrapers of primary collimator in CSNS/RCS. [ABSTRACT FROM AUTHOR]

Antechamber which composes the arc vacuum chamber of storage rings is one of the key devices of BEPCII. It has the characteristic of various specifications, large size, complex structure, and high dimension accuracy. This paper gives a review on the structure features and the procedure of production, including the mechanical machining process, cleaning and welding process of high vacuum aluminum alloy, ultrahigh vacuum test and so on. In view of the occurrence of the concave deformation, the reasons are analyzed and the correction method developed is introduced too. [ABSTRACT FROM AUTHOR]