循环荷载下砂岩疲劳损伤过程的声学特性分析

Analysis of acoustic property of sandstone fatigue damage under cyclic loading

利用电液伺服疲劳试验机系统研究了砂岩在单轴受压循环荷载作用下的疲劳损伤特性,配合智能型超声波检测设备及损伤在线实时监测系统,对砂岩试件在疲劳损伤过程中的声学参数(超声波速、时域波幅、波形)进行了实时的测量及详细地分析研究。结果表明,在循环加载过程中横向超声波速随损伤的发展变化比较敏感,呈现有规律的倒S型三阶段衰减现象,可以客观地描述砂岩的疲劳损伤特性及直观地反映疲劳损伤的各个阶段;超声波时域幅值在砂岩疲劳损伤过程中变化不稳定;波形在砂岩损伤过程中从有规则的纺锤形逐渐发生畸变,波形相关系数随循环次数的增长呈现整体下降趋势。研究成果进一步丰富了声学数据在疲劳损伤过程中的应用,从声学角度探讨了岩石疲劳损伤过程的微观机制,为进一步选择声学参数进行岩石疲劳损伤过程的跟踪识别提供试验依据。

By means of uniaxial closed-loop system and real-time observation system,with the measurement of ultrasonic wave velocity and strain at the same time;the experiments on sandstones fatigue damage are performed under constant amplitude cyclic loading.The acoustic parameters during sandstone fatigue damage including ultrasonic wave velocity,amplitude and waveform are real-time measured and analyzed in detail.Results show that the ultrasonic wave velocity varies temperamentally and reduces following inversed S-shaped line,which can be divided into three phases during fatigue damage of sandstones.The amplitude of ultrasonic wave fluctuates with damage.The waveform alters from regular fusiform to malformation;and its correlation coefficient is descending as a whole with the damage development.The micro destructive mechanism of the sandstones under cyclic loading is analyzed according to the variance of acoustic parameters.The testing results offer a choice of choosing acoustic parameters identifying rock fatigue damage process.