基于声发射-数字图像相关技术的泡沫混凝土冻融破坏特征及损伤演化规律

Freeze-thaw damage characteristics and evolution law of foam concrete based on acoustic emission-digital image correlation technique

  • 摘要: 为研究冻融环境下泡沫混凝土压缩破坏特征及损伤演化规律,对密度为800 kg/m3的泡沫混凝土开展了单轴压缩-声发射(AE)-数字图像相关(DIC)技术联合测试试验,获取了泡沫混凝土加载过程中的应变演化云图以及声发射参数变化特征。结果表明:泡沫混凝土的压缩破坏过程曲线呈现明显的阶段效应,且试件经历的冻融循环次数越多,延性破坏特征越明显;随着冻融循环次数的增加,DIC监测到试件应变集中带面积逐渐递增,应变场均值逐渐下降,同时,试件表面裂缝的形态由最初的垂直型单一裂缝向倾斜的剪切型多裂缝演变;冻融为0、20、40、60和80次的泡沫混凝土试件最终破坏时剪切裂缝所占比例分别为52.5%、57.8%、59.2%、65.3%和69.2%,声发射b值下降阶段分别出现在加载进程的92.3%、89.1%、88.5%、76.5%和72.3%;冻融环境可以促进泡沫混凝土由拉伸破坏向剪切破坏的转变,加剧泡沫混凝土内部损伤,从而在材料内部诱发大尺度破裂现象; AE和DIC的结果相辅相成,它们的结合有助于全面了解泡沫混凝土中微裂缝的发展规律和损伤破坏机制。

     

    Abstract: To study the compression damage characteristics and damage evolution law of foam concrete under a freeze-thaw environment, a joint test combining uniaxial compression, acoustic emission (AE), and digital image correlation (DIC) technology was carried out on foam concrete with a density of 800 kg/m3. The strain evolution cloud diagram and acoustic emission parameter change characteristics of the foam concrete during the loading process were obtained. The results show that the compression damage process curve of foam concrete presents an obvious staged effect. The more freeze-thaw cycles the specimen experiences, the more pronounced the ductile damage characteristics become. With the increase in the number of freeze-thaw cycles, the area of the strain concentration zone of the specimen monitored by the DIC gradually increases, while the average value of the strain field gradually decreases. Meanwhile, the morphology of surface cracks in the specimen evolves from initial vertical single cracks to tilted shear-type multi-fractures. The proportion of shear cracks in the final damage of foam concrete specimens with 0, 20, 40, 60, and 80 freeze-thaw cycles are 52.5%, 57.8%, 59.2%, 65.3%, and 69.2%, respectively. The stages of decreasing acoustic emission b-value appear in 92.3%, 89.1%, 88.5%, 76.5%, and 72.3% of the loading process, respectively. The freeze-thaw environment can promote the transition from tensile to shear damage in foam concrete, exacerbates the internal damage of foam concrete, and thus induces large-scale rupture phenomena within the material. The results of AE and DIC complement each other, and their combination contributes to a comprehensive understanding of the developmental pattern of microcracks and damage mechanisms in foam concrete.

     

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