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The repeatability of superconducting DC limiters has not been introduced by other literature. Understanding the performance degradation characteristics of high-temperature superconducting (HTS) tapes under the overcurrent is of great significance for popularizing the application of a resistive-type DC superconducting fault current limiter. In this paper, the threshold experiment and repeated DC overcurrent experiment of HTS tape were carried out. With the critical current decay of the tapes under repeated DC overcurrent recorded, the current threshold under the DC overcurrent was obtained. And the performance degradation characteristics of the tapes under different repeated overcurrents were analysed, the resistance characteristics of the samples during different currents were compared. The results show that the DC overcurrent threshold of the copper-encapsulated second-generation (2G) YBCO tapes samples of Suzhou Advanced Materials Research Institute is 2.3/4 ms/3700 A. Under the repeated overcurrent, the performance degradation of the samples is abrupt, and the critical value is between 2.3/4 ms/3500 A and 2.3/4 ms/3550 A. The overcurrent has a limited influence on the magnitude of the resistance and will not affect the change trend of the resistance. The resistance at the falling edge of the current was greater than that at the rising edge of the current. The simulation was carried out by using COMSOL Multiphysics, and the simulation results matched the experimental results. The life prediction model of the samples was established and it was found that there is a custom equation relationship between the reliability of superconducting tapes and the number of the overcurrent, and the performance decline of this kind of samples is catastrophic.

A new grouting model test device has been developed to model the fracture grouting process and improve understanding of the crack propagation regularity during grouting. It was concluded that the propagation process of crack is not one-time formed but undergoes the sequential mode of “expansion, stagnation, re-expansion, re-stagnation” after fracture initiation. The smaller the grouting pressure is, the longer the stagnation time is, and the smaller the crack propagation velocity is. The crack width increases rapidly when the crack tip stagnates or the expansion speed is small. Research results can help achieve better grouting aims and realize grouting safety in practice

Diamond sawblade is an efficient tool to building renovation or demolition. Concrete used in construction is a typical composite material with random distribution, which is difficult to accurately identify and predict even under the same processing conditions, and tool life of diamond sawblade is difficult to control. In this paper, by cutting out single component of the hard and soft aggregate separately from concrete, the single component and concrete experiments were carried out to understand the sawing characteristics of different components. The wavelet decomposition was used to analyze the characteristic of each frequency band of the different components sawing force and vibration signals, and the sensitive frequency bands after correlation coefficient and energy ratio variation of each wavelet layer were extracted to judge the bluntness status of sawblade. By taking the Root-Mean-Square (RMS) value, the energy ratio of d2 and d5 wavelet layers and the standard deviation of sawing force and vibration signal as the characteristic values of the sawblade, a neural network optimized by bat algorithm was established to analyze the concrete processing signals and predict the working state of the sawblade. Evidence theory was adopted to combine the prediction results of sawing force and vibration samples to increase the overall prediction accuracy and reliability. The test sample showed that this method can correct inconsistent individual sensor predictions while being as close to the actual status value as possible. It provides an effective tool life prediction way of the diamond sawblade and a theoretical method for the monitoring of non-metallic materials with inhomogeneous components.