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任会兰, 宁建国, 宋水舟, 王宗炼. 基于声发射矩张量分析混凝土破坏的裂纹运动[J]. 力学学报, 2019, 51(6): 1830-1840. DOI: 10.6052/0459-1879-19-170
引用本文: 任会兰, 宁建国, 宋水舟, 王宗炼. 基于声发射矩张量分析混凝土破坏的裂纹运动[J]. 力学学报, 2019, 51(6): 1830-1840. DOI: 10.6052/0459-1879-19-170
Ren Huilan, Ning Jianguo, Song Shuizhou, Wang Zonglian. INVESTIGATION ON CRACK GROWTH IN CONCRETE BY MOMENT TENSOR ANALYSIS OF ACOUSTIC EMISSION[J]. Chinese Journal of Theoretical and Applied Mechanics, 2019, 51(6): 1830-1840. DOI: 10.6052/0459-1879-19-170
Citation: Ren Huilan, Ning Jianguo, Song Shuizhou, Wang Zonglian. INVESTIGATION ON CRACK GROWTH IN CONCRETE BY MOMENT TENSOR ANALYSIS OF ACOUSTIC EMISSION[J]. Chinese Journal of Theoretical and Applied Mechanics, 2019, 51(6): 1830-1840. DOI: 10.6052/0459-1879-19-170

基于声发射矩张量分析混凝土破坏的裂纹运动

INVESTIGATION ON CRACK GROWTH IN CONCRETE BY MOMENT TENSOR ANALYSIS OF ACOUSTIC EMISSION

  • 摘要: 从细观上看, 混凝土是一种由骨料、水泥浆基体、裂纹等组成的非均匀复合材料. 单轴准静态加载条件下, 应力应变曲线表现出明显的准脆性特征. 其变形破坏过程实质上是内部微裂纹产生、扩展和汇合的过程, 研究细观尺度的裂纹扩展演化将有助于深入了解混凝土的变形和破坏过程. 声发射作为一种物理检测方法可以获取材料内部细观损伤演化的物理信息. 本文基于声发射技术, 结合改进的时差定位算法和矩张量理论对声发射信号进行分析, 反演了混凝土巴西劈裂破坏中裂纹位置、裂纹类型以及裂纹面运动方向, 揭示了混凝土宏观拉伸破坏的细观裂纹扩展机制. 结果表明: 裂纹运动过程清晰地显示了混凝土内裂纹源首先在试件与载荷接触面附近产生, 之后聚集形成局部损伤区域, 并沿轴线向中心扩展(加载平面)以及裂纹从试件中间向表面扩展的动态过程(厚度方向); 裂纹运动体积可以作为裂纹形成、扩展过程中弹性能释放的度量, 初始裂纹成核时体积参数较小, 峰值载荷时, 裂纹运动体积最大达到5.93\times10^-4 mm^3; 混凝土宏观尺度的拉伸破坏在细观尺度上存在有拉伸裂纹、混合裂纹以及剪切裂纹; 拉伸裂纹最多, 占裂纹总数约为60%, 剪切裂纹最少, 约占裂纹总数的10%; 拉伸裂纹运动主导了试件的宏观劈裂破坏.

     

    Abstract: On meso-scale, concrete can be considered as a kind of non-homogeneous composite mainly composed of aggregates, cement paste and cracks. Under uniaxial quasi-static loading condition, quasi-brittle characteristics can be observed in the stress-strain curves. Failure process of concrete is essentially a process of nucleation, propagation and convergence of internal micro-cracks.Therefore, investigation on the crack growth process on meso-scale is beneficial to understand the deformation and failure process of concrete. Acoustic emission is a physical detection method which can be used to obtain the physical information of the mesoscopic damage evolution inside many kinds of materials. Acoustic emission technique, modified time of arrival approach and moment tensor theory were applied to analyze the AE sources obtained in the Brazilian test and the locations, types and orientations of cracks in the specimens were investigated. Relationship between the failure on macro-scale and the mechanisms of cracking on meso-scale of concrete was revealed. The results show that the micro-cracks generate near two contact surfaces between specimen and loading plates firstly. Then the nucleation of the micro-cracks occur at the local zone. Finally, cracks propagate from top and bottom to the center of specimen along the loading direction in the elevation view. In the side view, cracks propagated from the internal zone to the surface. Volume of micro-cracks could be regarded as a measure of elastic energy released from the nucleation of micro-cracks. The volume of micro-cracks is small at the early stage of nucleation. When the load reached its peak value, the maximum volume of the micro-crack was 5.93\times 10^ - 4 mm^3. Tensile cracks, shear cracks and mixed-mode cracks on meso-scale could be observed in the tensile failure process of concrete on macro-scale. The failure process of the concrete was dominated by tensile cracks (nearly 60%) and the shear cracks had the minimum proportion (nearly 10%). The motion of tensile cracks dominate the macro-scale failure of specimen.

     

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