used an ultrasonic pulse transmission method to record the change in waveform across this transition during fracturing experiments. The transition from elastic to inelastic deformation coincides with a minimum in ultrasonic attenuation
(i.e., maximum wave amplitude). Prior to this attenuation minimum, the existing microfractures close. After this minimum, new microfractures form and attenuation increases until peak stress conditions, at which point, larger fractures form leading to complete sample failure. In our experiments, velocity changes are not sensitive enough to be indicative for the transition from elastic to inelastic deformation. Analysis of attenuation, not velocity, may thus
detect imminent failure in materials. Our results may help detect fracturing in borehole casings or the near-wellbore area, or they may help predict imminent release of energy by seismic rupture.
Stress, strain, velocity and attenuation data of shale, limestone and sandstone samples brought to failure
Barnhoorn, A. (Creator), Verheij, J. (Creator), Frehner, M. (Creator), Zhubayev, A. (Creator) & Houben, M. E. (Creator), TU Delft - 4TU.ResearchData, 2018