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用数字图像相关法研究聚合物改性砂浆的力学性能
作者:张朝阳 孔祥明 卢子臣 
单位:清华大学土木工程系建筑材料所 北京 100084 
关键词:数字图像相关法 聚合物改性砂浆 变形 力学性能 
分类号:TU528
出版年,卷(期):页码:2018,46(2):187-192
DOI:
摘要:

数字图像相关法(DIC)是一种新型的非接触式光学测量材料变形的方法,与传统接触式测量方法相比,具有操作简单、大变形测量、精度高、分析区域灵活可变等优点。聚合物乳液常用于改善水泥基材料的力学性能,提高抗拉、抗折强度及其韧性。本文采用三维数字图像相关法(3D-DIC)研究聚合物改性砂浆的在受压状态下的应力应变行为。结果表明,3D-DIC法可以提供试块选定区域的应力-应变全曲线,以及试块开裂性能、断裂模式等丰富的信息。研究发现,在受压模式下,接触法测得的试块轴向总变形大于采用DIC测得的选定中间区域的变形,这是由于试块中部选定区域的变形受到周围部分的约束。这种约束作用会随着聚合物改性砂浆弹性模量的降低而减弱。随着聚合物掺量的增加,由于聚合物的掺入增加了材料的断裂韧性并极大地削弱了应力集中,聚合物改性砂浆的破坏模式逐渐由脆性破坏转变为韧性破坏。此外,聚合物改性砂浆的开裂应变、峰值应变、断裂能随着聚合物掺量的增加而增加。聚合物掺量较低时(<5%),聚合物改性砂浆的Poisson比随着聚合物相的增加而升高。

Digital image correlation (DIC) method is a novel non-contact full field optical method for the measurement of deformation of specimens. Compared to the conventional methods for the deformation measurement that usually involve sensors being directly in contact with the samples, the DIC method has some advantages of easy operation, large scale and high accuracy deformation measurement, and flexible selection of the analysis area, etc.. In addition, polymer latexes are widely used in cementitious materials to improve their toughness and impermeability. This paper was to apply the DIC method to investigate the mechanical properties of polymer modified mortar (PMM). The full stress-strain curves of PMMs at different polymer contents were obtained under a compressive load by the DIC method and the conventional contacting method. The results show that besides the full stress-strain curves, the DIC method provides the additional information on cracking and fracturing of the specimens, which is more advantageous than the contacting methods. Compared to the full stress-strain curves obtained by the DIC method and the contacting method, the strain provided by the DIC methods that represents the deformation of the selected intermediate testing area is generally lower than that measured by the contacting method at a given stress load, which stands for the deformation of the whole sample. This phenomenon is due to the constriction effect of the surroundings for the selected intermediate testing area. A greater polymer content reduces the constriction effect of the surrounding material to the intermediate part. The failure mode of polymer modified mortar changes from brittle failure to ductile failure when the polymer content increases. Moreover, the 1st crack strain, peak strain and fracture energy of polymer modified mortar increase with the increase of polymer content. At low polymer dosages (i.e., <5%), the Poisson ratio of polymer modified mortar increases with the increase of polymer content.

基金项目:
作者简介:
张朝阳(1994—),男,硕士研究生。
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