Evaluation of fracture process by simultaneous measurement of acoustic and electromagnetic emission

电磁发射（EME）是介质材料发生断裂时产生的电磁辐射，可作为一种新方法用于评价介质材料内部发生的断裂过程。为了研究新方法的适用性，本研究在岩样的变形试验中同时测量了EME和AE （Acoustic Emission，声发射），从而证实了EME的产生与AE估计的微裂缝的发生之间的关系。从本研究中可以得出以下结论：(1)EME只有在材料内部产生由于开裂而产生的新表面时才会产生。(2)建立了基于裂纹表面电荷偶极矩和裂纹壁振动的电磁辐射产生模型。(3) EME信号幅值与AE信号幅值呈正相关。(4)电磁干扰是研究材料内部断裂过程的有效工具。(5)电磁法作为一种野外应用的方法，在估算岩石地应力方面是非常有用的。

Electromagnetic emission (EME), which is emanated when the fracture of the dielectric materials occurs, may be applicable for evaluating the fracture process occurred inside the materials, as one of the new method. In order to investigate the applicability of the new method, in this study, the simultaneous measurement of EME and AE (Acoustic Emission) was conducted on the deformation tests of rock samples, so that the relationship between the generation of EME and the occurrence of micro fractures, which is estimated by AE, would be confirmed. The following conclusions could be drawn from the present study:(1)EME generates only when the fresh surfaces due to cracking are created in the material.(2)A model for explaining the EME generation has been established based on the dipole moment of electric charges distributed on the crack surfaces and the vibration of crack walls.(3)Positive correlation between the signal amplitudes of EME and AE is found.(4)EME may be useful tools for studying the fracture process occurred inside the materials.(5)EME is very useful for estimating the rock in-situ stress, as a method in the field application.