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

电磁辐射(EME)是评价材料内部断裂过程的一种新方法，它是介质材料发生断裂时所产生的辐射。为了考察这种新方法的适用性，本研究对岩石样品的变形试验进行了电磁辐射和声发射的同步测量，以确定电磁辐射的产生与由声发射估计的微裂缝的发生之间的关系。本研究得出以下结论：(1)只有在材料中产生新的裂纹表面时，才会产生电磁辐射。(2)根据裂纹表面电荷的偶极矩和裂纹壁的振动建立了电磁辐射产生的模型。(3)电磁辐射的信号幅度与声发射呈正相关。(4)电磁辐射可能是研究材料内部断裂过程的有用工具。(5)电磁辐射作为一种现场应用的方法，对于估计岩石的地应力是非常有用的。

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.