大坝混凝土动态弯拉声发射特性试验

为了研究大坝混凝土在不同加载速率下的弯拉声发射特性，并进一步理解不同加载速率下混凝土的损伤发展过程，在MTS试验机上以四种不同的加载速率进行了无开口湿筛混凝土梁的三弯点试验。结果表明，随着加载速率的提高，声发射撞击累计数减少，而撞击率峰值增加，低振幅（35-40 dB）的声发射信号所占比例有所增加，声发射振铃数、信号能量和持续时间的平均值都有提高的趋势；在低加载速率时，混凝土在破坏过程中产生较少数的微裂缝，其破坏机制受少数主要裂缝（跨中位置）控制，而在高加载速率时，微裂缝分布在较宽的范围之内。

Experiment on Acoustic Emission Characteristics of Dam Concrete Under Dynamic Bending Tension

In order to study the acoustic emission（AE） characteristics of dam concrete under bending tension in different loading rate, and to get further understanding about the dynamic damage process of dam concrete, unnotched wet-screened concrete beams were tested in MTS materials test system under bending tension in four different loading rates. The results showed that, with the increase of loading rate, the accumulated hit number decreased and the peak value of AE hit rate increased, the percentage of AE hits in low amplitude （ 35 - 40 dB） increased, and the average values of count, signal energy and duration of AE hits were increased, as well, Less AE events（microcracks） generated and the AE events tended to distribute in a smaller range, while in lower loading rate. Oppositely, AE events tended to distribute in a wider range.