Three-dimensional location and characterization of microcracks in controlled fracture tests of hard coal beams were experimentally conducted through the quantitative acoustic emission (AE) technique. The recorded AE events were physically interpreted as displacement discontinuities (DD), i.e. microcracks, involving only opening/closing and shear-sliding mechanisms to describe the fracture modes directly anticipated within a mechanically loaded material. Based on the AE sensor calibration using a scalar sensitivity parameter and the first motion of P-wave, the moment tensor components were determined through minimizing the errors between the measured and calculated displacements at each sensor location, subjected to a restriction from this “crack-only” source model. Source characterization results were presented in a statistical form, which showed mixed mode mechanisms of microcracks with approximately equal contribution of shear and tensile displacements locally due to the considerably tortuous crack path in the microstructural level of coal material. However, the microcrack volume decomposition under the global coordinate system indicated a mode-I opening micromechanisms dominantly, which was compatible with the expected mechanism from the three-point bending test. Additionally, the orientations of microcrack planes were more or less vertical, with an average angle of 20.4° from the global fracture plane. And around 79.6% of the AE sources with an angle, made by the displacement vectors with horizontal direction, less than 30°. AE magnitudes followed the Gutenberg-Richter relation with a b-value of around 1.3 during coal fracture. Owing to the physical basis of energy dissipation and the linear relationship with scalar moment, the so-called “crack volume” |b|ΔA was used as an index of the absolute AE energy. Energy dissipation region moved forward together with the crack propagation, and most of the energy was dissipated above the crack tip by separating the crack face.

通过定量声发射（AE）技术，对硬煤梁的受控断裂试验中的微裂纹进行了三维定位和表征。所记录的AE事件在物理上被解释为位移不连续性（DD），即微裂纹，仅涉及打开/关闭和剪切滑动机制来描述机械负载材料中直接预期的断裂模式。基于使用标量灵敏度参数的AE传感器校准和P波的第一运动，通过使每个传感器位置处的实测位移与计算位移之间的误差最小，从而确定了力矩张量分量，并受到此“裂纹-裂纹”的限制。仅”源模型。来源表征结果以统计形式呈现，结果表明，由于煤材料微观结构中相当大的弯曲裂纹路径，微裂纹的混合模式机制在局部具有与剪切位移和拉伸位移近似相等的贡献。然而，在整体坐标系下的微裂纹体积分解表明，I型开放微机制占主导地位，这与三点弯曲试验所预期的机制是兼容的。此外，微裂纹平面的取向或多或少是垂直的，与整体断裂平面的平均夹角为20.4°。大约79.6％的AE源与水平方向的位移矢量所成的角度小于30°。煤破裂过程中，AE值遵循古登堡-里希特关系，b值约为1.3。由于能量耗散的物理基础以及与标量矩的线性关系，所谓的“裂纹体积” | b |ΔA被用作绝对AE能量的指标。能量耗散区域随着裂纹的扩展而向前移动，并且大部分能量通过分离裂纹面而在裂纹尖端上方消散。