混凝土表面裂缝的远距离声激励检测数值研究
发布时间：2018-10-22 07:29
【摘要】：混凝土材料是目前土木建筑行业中使用最广泛的建筑材料,由于混凝土是一种脆性材料,其抗拉强度较差,混凝土结构在内外因素的作用下不可避免地发生开裂现象而存在裂缝。目前检测混凝土表面裂缝所使用的传统方法大都是近结构表面(非接触式)或预先埋入结构中(接触式)的检测方法。由于混凝土结构的自身特点的限制,传统的近距离接触式的检测方法存在很大缺点,因此,研究一种远距离、非接触式的无损检测方法很有必要。本文基于有限元软件ANSYS,研究远距离高指向性的声激励检测混凝土表面裂缝的远距离非接触式的检测方法,具体包括以下几个方面的工作:圆形活塞换能器的声场特性研究。使用数值解析软件Matlab根据圆形活塞换能器的辐射声场的声压及指向性函数理论公式进行分析,详细研究了圆形活塞换能器的声压分布特性和指向性。在利用有限元分析软件ANSYS对圆形活塞换能器进行仿真模拟。把ANSYS软件仿真分析的声压与指向性结果与Matlab软件理论分析的结果进行比对,探讨ANSYS软件对声学换能器仿真的准确性与可行性。使用有限元建模的方法,探究远距离高指向性声束对混凝土表面裂缝无损检测方法的可测性。基于Matlab软件,探讨高指向性声激励的选择。基于ANSYS软件,详细探讨了声学参量阵换能器阵作为远距离激励源的方法和模拟步骤。把声激励作用在底面固支和简支两种约束形式的混凝土构件上,并根据不同的约束条件选择合理频率的声激励进行逐点扫描。通过观察构件表面质点竖向振动位移幅值曲线是否出现尖峰区域或不平滑的折线区域,及该区域尖峰幅值大小及其底角的距离可以判断混凝土表面裂缝的位置、宽度及深度大小。得出远距离声激励检测方法可以用来检测混凝土的表面裂缝。基于模拟结果,研究底面固支的混凝土构件在不同表面裂缝宽度、深度、不同混凝土构件尺寸以及实际环境噪音对检测方法的影响,结果表明本检测方法的最大可测混凝土深度的数值与混凝土厚度成正相关。当裂缝深度小于可测裂缝最大深度时,裂缝尖端质点竖向位移幅值随裂缝深度成线性关系,其他因素对远距离声激励检测混凝土表面裂缝影响较小。研究外界噪音对远距离声激励检测底面固支混凝土构件表面裂缝方法的影响,结果发现外界的噪音影响很小,可以忽略不计。
[Abstract]:Concrete is the most widely used building material in the civil construction industry at present. Because concrete is a brittle material, its tensile strength is poor. Under the action of internal and external factors, cracks inevitably occur in concrete structures. At present, most of the traditional methods used to detect concrete surface cracks are near structural surface (non-contact) or embedded in the structure (contact). Because of the limitation of concrete structure's own characteristics, the traditional close contact detection method has great shortcomings. Therefore, it is necessary to study a long distance, non-contact nondestructive testing method. Based on the finite element software ANSYS, this paper studies the long distance non-contact detection method of long distance and high directivity acoustic excitation for detecting concrete surface cracks, including the following aspects: the study of sound field characteristics of circular piston transducer. The sound pressure distribution and directivity of circular piston transducer are studied in detail by using numerical analysis software Matlab according to the theoretical formula of sound pressure and directivity function of the radiation sound field of circular piston transducer. The circular piston transducer is simulated by finite element analysis software ANSYS. The results of sound pressure and directivity analysis of ANSYS software are compared with the results of theoretical analysis of Matlab software, and the accuracy and feasibility of ANSYS software for acoustic transducer simulation are discussed. The finite element modeling method is used to explore the testability of long distance and high directivity acoustic beams for nondestructive detection of concrete surface cracks. Based on Matlab software, the choice of high directional acoustic excitation is discussed. Based on ANSYS software, the method and simulation steps of acoustic parametric array transducer array as a remote excitation source are discussed in detail. The sound excitation is applied to the concrete members with two kinds of restraint forms: the bottom plane clamping and the simple support, and the sound excitation with reasonable frequency is selected according to the different constraint conditions to carry out the point-by-point scanning. By observing whether the vertical vibration displacement amplitude curve of the surface of the member has a peak region or a non-smooth broken line area, and the distance between the peak amplitude and the bottom angle of the area, the position of the crack on the surface of concrete can be determined. Width and depth. It is concluded that the long distance acoustic excitation method can be used to detect the surface cracks of concrete. Based on the simulation results, the effects of different surface crack width, depth, size of concrete members and actual environmental noise on the detection methods are studied. The results show that the maximum measurable depth of concrete is positively correlated with the thickness of concrete. When the crack depth is less than the maximum depth of the measured crack, the vertical displacement amplitude of the particle at the crack tip has a linear relationship with the crack depth, and other factors have little effect on the detection of concrete surface cracks by long-distance acoustic excitation. The influence of external noise on the detection of surface cracks of concrete members with fixed bottom surface by long distance acoustic excitation is studied. The results show that the external noise has little effect and can be ignored.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
本文编号：2286502
[Abstract]:Concrete is the most widely used building material in the civil construction industry at present. Because concrete is a brittle material, its tensile strength is poor. Under the action of internal and external factors, cracks inevitably occur in concrete structures. At present, most of the traditional methods used to detect concrete surface cracks are near structural surface (non-contact) or embedded in the structure (contact). Because of the limitation of concrete structure's own characteristics, the traditional close contact detection method has great shortcomings. Therefore, it is necessary to study a long distance, non-contact nondestructive testing method. Based on the finite element software ANSYS, this paper studies the long distance non-contact detection method of long distance and high directivity acoustic excitation for detecting concrete surface cracks, including the following aspects: the study of sound field characteristics of circular piston transducer. The sound pressure distribution and directivity of circular piston transducer are studied in detail by using numerical analysis software Matlab according to the theoretical formula of sound pressure and directivity function of the radiation sound field of circular piston transducer. The circular piston transducer is simulated by finite element analysis software ANSYS. The results of sound pressure and directivity analysis of ANSYS software are compared with the results of theoretical analysis of Matlab software, and the accuracy and feasibility of ANSYS software for acoustic transducer simulation are discussed. The finite element modeling method is used to explore the testability of long distance and high directivity acoustic beams for nondestructive detection of concrete surface cracks. Based on Matlab software, the choice of high directional acoustic excitation is discussed. Based on ANSYS software, the method and simulation steps of acoustic parametric array transducer array as a remote excitation source are discussed in detail. The sound excitation is applied to the concrete members with two kinds of restraint forms: the bottom plane clamping and the simple support, and the sound excitation with reasonable frequency is selected according to the different constraint conditions to carry out the point-by-point scanning. By observing whether the vertical vibration displacement amplitude curve of the surface of the member has a peak region or a non-smooth broken line area, and the distance between the peak amplitude and the bottom angle of the area, the position of the crack on the surface of concrete can be determined. Width and depth. It is concluded that the long distance acoustic excitation method can be used to detect the surface cracks of concrete. Based on the simulation results, the effects of different surface crack width, depth, size of concrete members and actual environmental noise on the detection methods are studied. The results show that the maximum measurable depth of concrete is positively correlated with the thickness of concrete. When the crack depth is less than the maximum depth of the measured crack, the vertical displacement amplitude of the particle at the crack tip has a linear relationship with the crack depth, and other factors have little effect on the detection of concrete surface cracks by long-distance acoustic excitation. The influence of external noise on the detection of surface cracks of concrete members with fixed bottom surface by long distance acoustic excitation is studied. The results show that the external noise has little effect and can be ignored.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
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