基于声发射参数的玄武岩纤维混凝土抗弯断裂及声波衰减特性研究

发布时间：2018-03-01 06:16

本文关键词： 玄武岩纤维混凝土声发射四点弯曲弯曲断裂声波衰减　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着国内外对新型建筑材料需求的不断提升,纤维增强混凝土得到广泛的应用和重视。目前针对钢纤维、聚丙烯纤维等改良混凝土已有学者做了大量研究,但对玄武岩纤维改良混凝土的研究相对较少。然而玄武岩纤维具有较好的耐化学腐蚀性和耐热性、生产工艺简单、制造成本低廉、相容性好、综合性能强等优点,将其用于混凝土性能改良具备良好的应用前景。声发射作为一种重要的无损检测手段,有着灵敏度高、反应及时和可实现全周期在线监测等诸多优点,在材料和结构健康监测领域拥有广阔的前景。不同于其它技术,声发射是材料自身损伤引起的,使其更具有可信性,是无损检测领域热点研究问题。目前,针对玄武岩纤维混凝土的声发射特性研究急需开展。所以,本文以玄武岩纤维混凝土作为研究对象,声发射检测技术作为研究手段,对玄武岩纤维增强混凝土的力学性能和声发射特性进行研究,探究玄武岩纤维增强混凝土的断裂机理和损伤规律,为玄武岩纤维混凝土的推广和声发射技术在混凝土结构健康监测领域的应用提供基础数据和理论参考。本文所开展的主要研究工作包括:(1)制作了3组不同龄期的玄武岩纤维增强混凝土梁,以相同龄期的素混凝土梁作为对比组,共18个相同规格尺寸的长方体小梁试件。对试件分别进行四点弯曲试验,得到不同龄期材料的抗弯极限强度。结果表明,随着龄期的增长,纤维的增强作用不断增加,7d、14d和28d的混凝土强度提高率分别为5.53%、6.10%和8.33%。(2)通过对试件断裂过程的声发射参数进行统计分析,分析了混凝土试件的受荷载断裂过程。整个断裂过程可分为三个阶段,每个阶段对应着不同的声发射特征。这些特征反映了混凝土不同的受力状态和相应的内部裂缝扩展情况,验证了声发射对于玄武岩纤维混凝土监测的适用性。基于声发射特征参数,阐述了纤维的增强机理和增强效果。(3)针对声发射的统计参数,通过与相应的受力状态进行对比分析,分析结果表明:声发射参数的统计值特性可以用于玄武岩纤维混凝土材料的断裂预测分析。此外,提取了新的声发射特征参数,即最大信息熵。最大信息熵可以进行材料的断裂前兆分析,新的特征参数具有良好的分析效果。在混凝土断裂过程中运用了声发射特征统计量平均频率(AF)和RA值对内部裂缝情况进行了分析。(4)针对声发射信号在玄武岩纤维混凝土中的传播衰减情况,制作了三根相同的钢筋混凝土悬臂梁,进行等距声发射信号接收测试。通过对信号进行傅立叶变换和参数提取,总结了声波的衰减规律。结果表明:声发射信号振幅随距离的传输成二次函数衰减趋势;声发射的能量和波速成指数函数衰减趋势;对于声发射的频率衰减,其信号高频部分快速衰减,并引起结构一阶和二阶频率之间频率分布的增加。随着声信号的传播,各个频带分布比例都大幅减小。
[Abstract]:With the increasing demand for new building materials at home and abroad, fiber reinforced concrete (FRC) has been widely used and paid more attention. At present, many scholars have done a lot of research on improved concrete, such as steel fiber and polypropylene fiber. However, basalt fiber has the advantages of good chemical corrosion resistance and heat resistance, simple production process, low manufacturing cost, good compatibility and strong comprehensive properties. As an important nondestructive testing method, acoustic emission has many advantages, such as high sensitivity, timely response and the ability to realize the whole cycle on-line monitoring. It has a broad prospect in the field of material and structural health monitoring. Unlike other technologies, acoustic emission (AE) is caused by materials' own damage, which makes it more credible and is a hot research issue in the field of nondestructive testing (NDT). The study on acoustic emission characteristics of basalt fiber reinforced concrete is urgently needed. Therefore, this paper takes basalt fiber reinforced concrete as the research object and acoustic emission detection technology as the research means. The mechanical properties and acoustic emission characteristics of basalt fiber reinforced concrete are studied, and the fracture mechanism and damage law of basalt fiber reinforced concrete are explored. This paper provides basic data and theoretical reference for the application of basalt fiber reinforced concrete and acoustic emission technology in the field of concrete structure health monitoring. Basalt fiber reinforced concrete beams, Taking plain concrete beams of the same age as control group, 18 cuboid trabeculae of the same size were tested. The bending ultimate strength of materials of different ages was obtained by four point bending test. With the increase of age, the strengthening effect of fiber increases continuously. The concrete strength increases by 5.536.10% and 8.33% in 14d and 28d, respectively. The acoustic emission parameters of the fracture process of the specimens are analyzed statistically. The loading fracture process of concrete specimen is analyzed. The whole fracture process can be divided into three stages, each stage corresponds to different acoustic emission characteristics. These characteristics reflect the different stress state of concrete and the corresponding internal crack propagation. The applicability of acoustic emission to the monitoring of basalt fiber reinforced concrete is verified. Based on the characteristic parameters of acoustic emission, the reinforcement mechanism and enhancement effect of the fiber are expounded. The results show that the statistical characteristics of acoustic emission parameters can be used to predict the fracture of basalt fiber reinforced concrete materials. In addition, new acoustic emission characteristic parameters are extracted. That is, the maximum information entropy. The maximum information entropy can be used to analyze the fracture precursors of materials. The new characteristic parameters have good analysis effect. In the process of concrete fracture, acoustic emission characteristic statistics (AFF) and RA value are used to analyze the internal cracks. 4) Acoustic emission signals in basalt fibers are analyzed. Propagation attenuation in concrete, Three same reinforced concrete cantilever beams were made, and the isometric acoustic emission signals were tested. The signals were analyzed by Fourier transform and parameter extraction. The attenuation law of acoustic wave is summarized. The results show that the amplitude of acoustic emission signal propagates with distance into a quadratic function attenuation trend, the attenuation trend of energy and wave velocity exponential function of acoustic emission, the frequency attenuation of acoustic emission, The frequency distribution between the first and second order frequencies of the structure increases rapidly, and the frequency distribution ratio of each frequency band decreases greatly with the propagation of the acoustic signal.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528.572

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