不同应力路径下大理岩声发射特性试验研究

利用TAW-2000高温岩石三轴伺服试验机和德国VallenAMSY-6声发射信号采集系统,对大理岩在单轴压缩、等幅循环加卸载和分级循环加卸载条件下损伤破坏全过程的声发射特性进行研究,并用快速傅里叶转换(FFT)对单轴压缩试验全过程的声发射信号、循环加卸载过程中Kaiser点和Felicity点的声发射信号频谱特性进行了分析。试验结果表明:单轴压缩试验过程中,声发射主频带主要位于两个区域——低于200 kHz区间和300 kHz附近,并且随着加载应力的增加,主频由低频向高频转移,主频幅值总体呈下降趋势;提出一个新的反映声发射波形信息的指标——次主比α,并指出单轴压缩过程中次主比呈上升趋势。分级循环加卸载过程中Kaiser点和Felicity点的主频变化不明显,Felicity点的次主比总体大于Kaiser点;采用第2次循环中与首循环峰值应力等值应力点的AE数作为Kaiser效应中"明显增多"的尺度能够观察到明显的Felicity效应。

Experimental on acoustic emission characteristics of marble with different stress paths

Using TAW-2000 servo testing machine and Germany VallenAMSY-6 acoustic emission signal acquisition system，the acoustic emission characteristics of marble under uniaxial compression，constant amplitude cyclic loading and unloading and tiered cyclic loading and unloading were studied.In addition，using Fast Fourier Transformation(FFT)，the acoustic emission spectrum characteristics of marble under uniaxial compression and Kaiser points and Felicity points in the process of tiered cyclic loading and unloading were analyzed.Test results show that：Firstly，main frequency locate mainly in two areas，which are the regions less than 200 kHz and near 300 kHz，and the main frequency varies from low frequency to high frequency and the amplitude of main frequency declines on the whole with the increasing stress.Secondly，a new indicator to reflect acoustic emission waveform information，namely SF(secondary frequency)-by-MF(main frequency)ratio α，was put forward and in the process of uniaxial compression test SF(secondary frequency)-by-MF(main frequency)shows ascendant trend.Thirdly，the change of main frequency at Kaiser point and Felicity point is not obvious and the SF(secondary frequency)-by-MF(main frequency)ratio at Felicity point is higher than the one at Kaiser point in the hierarchical cyclic loading and unloading process.At last，by regarding AE(Acoustic Emission)counts at the point of stress in the second cycle whose stress is equal to the peak stress of first cycle as the “significant increased” scale of Kaiser effect，obvious Felicity effect is showed.