采用人工通电加速腐蚀的方法模拟混凝土梁内预应力钢筋的自然断裂过程从而获得真实的断丝声发射信号，应用高频声发射传感器和分布式光纤监测系统从水下采集预应力钢筋断裂时产生的声信号，分析信号的时频域特征和时域统计特征参数，结果表明：断丝信号的超声波段在水中传播时发生频散，应采用20kHz以下的时域统计特征识别断丝信号；铠装光缆可以接收到在水中传播的断丝信号，其在时频图上表现为一条竖直的条带，并且能量主要集中分布于100~200Hz。采用时域统计特征参数分析光纤监测信号时，需要设定较小的门槛值截取信号进行分析；对于光纤水声监测工况来说，峰值指标的信噪比较低，裕度和峭度指标更适合于用来识别断丝信号。本研究为开发预应力混凝土结构断丝水下声光纤监测系统奠定了基础。
Abstract
To obtain the actual acoustic emission signal of the corrosion fracture of prestressing steel in concrete beam, the galvanostatic method is applied to simulate the natural corrosion and artificially accelerate the process. High frequency acoustic emission sensors and distributed optical fiber monitoring system are used to collect the acoustic signals underwater when prestressed steel wires are broken. Signal are statistically analyzed in time domain and time-frequency domain. Test results show that only the time domain statistic characteristics below 20kHz can be used to identify the wire fracture, as the frequency dispersion occurs when the ultrasonic band of the wire-breakage signal propagates in the water. The fracture signal propagating in water can be received by the armored optical cable, which appears as a vertical band in the time-frequency diagram, and the energy is mainly concentrated in 100~ 200Hz. Small threshold should be set to intercept the signal from optical fiber monitoring system for the statistical analysis in time domain. For underwater condition, the signal-to-noise ratio of the peak index is low, and the margin and kurtosis index are more suitable for identifying fracture signal. This research lays the foundation for the development of underwater acoustic optical fiber monitoring system of prestressed concrete structure.
关键词
断丝监测 /
声发射 /
分布式光纤 /
水声探测
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Key words
wire breakage monitoring /
acoustic emission /
distributed optic fiber /
underwater acoustic detection
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