带裂缝混凝土动态轴拉的声发射特性研究

为研究带裂缝混凝土在动态轴向拉伸荷载作用下的声发射信号特性,采用张口位移控制加载的方式,开展了张口位移速率为10~(-5)~10~(-2)/s的混凝土动态轴向拉伸断裂试验,分析了不同加载速率下声发射特征参数振铃计数、状态参数事件计数率和荷载随时间的变化曲线。试验表明:振铃计数包络曲线和荷载曲线具有良好的对应关系,且随着加载速率的提高,声发射活动越集中,试件断裂时间越短,更偏向脆性破坏,声发射能很好地揭示试件动态拉伸的受载情况和破坏状态。基于声发射特征参量的能量分析揭示了混凝土断裂破坏能量释放规律。结果表明:带裂缝混凝土动态轴向拉伸破坏不具有典型的3阶段特征,声发射信号在破坏瞬间突发性增强;随着张口位移速率的提高,混凝土断裂破坏时间缩短,极限强度增加,释放的能量呈指数增长。

Acoustic emission characteristics of cracked concrete under dynamic axial tension

In order to clarify the acoustic emission signal characteristics of cracked concrete under dynamic axial tensile loading, the dynamic axial tensile fracture test is carried out by controlling crack mouth opening displacement rate ranging from 10-5/s ~10-2/s. The curves of time and acoustic emission characteristic parameters such as sound emission ring-down count, the event count rate and load are analyzed at different loading rates. It is found that the ring-down count envelope curve and load curve have good correspondence; the higher the loading rate, the more concentrated acoustic emission activity is revealed; and the shorter the fracture time, the more prone to brittle failure. Acoustic emission can well reveal the loading condition and failure state of the concrete specimen under dynamic axial tension loading. The energy release law of concrete fracture failure is analyzed based on the energy of acoustic emission characteristic parameters. It is indicated that the dynamic axial tensile failure of cracked concrete does not have typical three stages characteristics. The emission signal abruptly enhanced in a moment. As the mouth crack opening displacement rate increases, the fracture failure time of concrete decreases, ultimate strength increases and the released energy increases exponentially.