Acoustic emission behavior of prestressed reactive powder concrete under flexural loads
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摘要: 为研究钢纤维增强活性粉末混凝土(SF/RPC)复合材料的受弯破坏微观机制,对10根试验梁进行抗弯试验研究。基于声发射技术,采用宽频传感器对试验过程中的声发射信号和波形进行了采集。分析研究了SF/RPC材料的声发射特征参数,在对波形进行信号处理的基础上对波形频谱进行了深入研究。通过传感器之间互相发射和接受信号,对SF/RPC材料的声发射波速进行了测定。同时与普通混凝土(NC)材料声发射特性进行了对比分析研究。结果表明:相同荷载作用下SF/RPC的撞击累计数远大于NC梁,声发射活跃性高于NC材料;预应力SF/RPC梁的声发射特征参数与NC梁有着明显区别,SF/RPC短上升时间段(<30 μs)的声发射撞击平均比例为64.2%,明显高于NC的比例51.2%;SF/RPC材料波形频域特性也与NC材料明显不同;荷载作用前,SF/RPC材料内平均波速为4 342.8 mm/s,NC材料内平均波速为2 337.7 mm/s。通过引入Gutenberg-Richter理论,计算了声发射信号损伤参数(bI),对预应力SF/RPC损伤开裂过程与bI值的关系进行了分析研究。本研究结果为有效识别SF/RPC材料的声发射特性提供试验依据。Abstract: To study the micro mechanical behavior of steel fiber reinforced reactive powder concrete (SF/RPC) composite material under flexural loads, 10 experimental beams were fabricated and tested. Based on the acoustic emission technique, the acoustic emission signals and waveforms during the test were collected by using the broadband sensors. The acoustic emission parameters of SF/RPC material were analyzed, and the waveform spectrum was studied deeply on the basis of the signal processing of the waveform. The acoustic emission velocity of the SF/RPC material was measured by emitting and receiving signals between the sensors. The acoustic emission characteristics of normal concrete(NC) material were explored for comparison. The results show that the accumulate number of hits is much larger than that of NC beam under the same load, and the acoustic emission activity is higher than that of NC. The acoustic emission characteristic parameters of prestressed SF/RPC are obviously different from NC beam. The average acoustic emission hits proportion of SF/RPC for the short rise time period (<30 μs) is 64.2%, while the proportion of NC is 51.2%. The frequency domain characteristics of SF/RPC material are also significantly different from those of NC material. Before the load, the average wave velocity of SF/RPC is 4 342.8 mm/s, while the velocity of NC is 2 337.7 mm/s. The acoustic emission damage parameter (bI) value is calculated based on the Gutenberg-Richter theory. The relationship between bI value and the damage fracture process of prestressed SF/RPC was explored. This study provides experimental basis for the effective identification of the acoustic emission characteristics of SF/RPC material.
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