不同荷载作用下拉破裂的声发射特征研究

Acoustic emission properties of tensile fractures under different load patterns

采用类岩石材料研究了不同加载条件下的张拉裂纹的破裂过程,并利用声发射(AE)测试技术分析了劈拉试样和三点弯曲试样在断裂过程中裂纹的萌生、起裂、扩展和破裂全过程的声发射特征。试验结果表明,声发射的阶段性突发特征反映了张拉裂纹阶段性扩展的力学机制。但是,在不同的加载条件下,张拉破裂的声发射特征有所差异:在弯拉应力作用下,试样拉破裂的声发射特征表现可分为声发射数的渐进增长、快速增长、突发式增长和逐渐下降4个阶段;而在劈拉应力作用下,试样破裂的声发射特征可分为声发射数缓慢增长、声发射数突发和声发射数的稳定发展3个阶段。在弯拉应力作用下,裂纹的萌生和聚集阶段的声发射特征明显,但在劈拉应力作用下几乎观察不到其声发射特征变化。不同破裂模式下的声发射特征值得进一步研究。

Under different load patterns,some experiments using special mortar specimen are carried out.The whole process of initiation,cracking,growth and fracture of cracks is analyzed by using acoustic emission (AE) technique.Experimental results show that the AE properties of tensile fractures are different under loading types.The AE properties of crack propagation process under bending action contain four stages:gradual increase,quick increase,sudden increase and gradual decrease of AE numbers.But those under splitting load,it contains three stages:slow increase,sudden increase and stable increase of AE numbers.The AE characters of crack initiation and coalescences under bending are obvious,but not clear under splitting load.It deserved to further study the AE properties under different loading conditions.