隐蔽裂缝对混凝土波动传播特性的影响规律研究
发布时间：2019-06-07 11:49
【摘要】：混凝土在使用过程中,由于长期荷载、环境腐蚀、材料老化、构件破损等因素作用,混凝土内部逐渐产生损伤积累,使结构的承载能力和耐久性能下降,减少了结构的使用寿命。如何有效地预测在役混凝土的损伤演变情况是当前混凝土工程亟待解决的关键性问题之一。鉴于此,本文在线性及非线性声学波动理论基础上,研究混凝土隐蔽裂缝形态参数与波动传播特性的相关性规律,为更好的实现对混凝土材料探测提供理论基础和应用参考,主要研究内容及结论如下:1)对养护好的含不同形态参数裂缝的混凝土试件进行超声波测试试验,采用快速傅立叶变换和小波分析等信号处理技术实现了对声波信号参数的提取,研究零应力状态下裂缝的存在对混凝土超声参数的影响。试验表明:零应力状态下,混凝土试件内有裂缝时的波速比试件内无裂缝时小,但裂缝尺寸不大时变化幅度小,较难区分;裂缝宽度对波速影响明显,深度其次,裂缝走向与声波传播方向夹角对波速无影响。2)零应力状态下,采用快速傅立叶变换和频谱分析的方法得到混凝土的声学参数,与完整试件相比,有裂缝的试件其裂缝形态参数对最大振幅影响明显,且裂缝走向与声波传播方向重合时最大振幅的值最小,裂缝走向与声波传播方向垂直时时域最大振幅的值最大。除主频外,各参数随裂缝形态参数变化规律相似。裂缝对频域最大振幅和谱面积影响规律基本相同,均随裂缝尺寸的增加而下降。3)开展了单轴受载混凝土的超声波测试试验,分析了裂缝不同形态参数混凝土超声参数与应力相关性的影响,试验结果表明:受荷条件下试件内有裂缝时,基本规律是裂缝尺寸越大,随应力变化波速下降越快,且在试件破坏时其波速的最小值越小。相比于裂缝宽度,裂缝深度对试件波速与应力敏感性的影响较弱。裂缝与超声波传播方向的夹角不同的几种情况中,裂缝与超声波传播方向重合即夹角为0°时随着应力的增加波速下降速率最大。4)通过小波变换得到的加权谱面积,在一定程度上滤除了高频干扰并考虑了不同尺度间权重的差异,对应力有较强的敏感性。含不同形态参数裂缝的试件,加载时加权谱面积变化规律基本相同,即随应力增加,裂缝尺寸越大加权谱面积变化幅度越明显。加权主频幅值与加权谱面积随应力变化趋势大致相同,均在超过试件极限应力的70%后急剧下降,这可能是由于裂缝贯通所致,表明出现了不可逆的塑性变形,试件已接近破坏。5)主频与混凝土内部结构状态和外部应力状态均无关。零应力状态下试件内有无裂缝对主频影响不大,受荷条件下,随着应力的增加,主频也基本不改变6)通过分析零应力状态下缺陷尺度与超声波波长的关系,在此基础上利用含裂缝混凝土的等效弹性参数,建立了零应力状态下不同缺陷分布所引起的超声波慢度的变化关系。通过分析单个微裂纹影响下微裂纹的扩展作用机理和单个微裂纹扩展的混凝土损伤本构关系,建立了用声参数表征的混凝土损伤本构模型,并将理论与试验结果进行了对比,结果表明用波速表示的混凝土损伤本构模型能较好地反映应力变化对波速的影响规律。
[Abstract]:In the process of use, due to the factors such as long-term load, environmental corrosion, material aging and component breakage, the damage and accumulation are gradually generated in the concrete, so that the bearing capacity and the durability of the structure can be reduced, and the service life of the structure is reduced. How to predict the damage and evolution of active concrete is one of the key problems to be solved urgently. In view of this, on the basis of the theory of linear and non-linear acoustic wave, this paper studies the relationship between the morphological parameters and the wave propagation characteristics of the concrete concealed crack, and provides the theoretical basis and application reference for the better realization of the concrete material detection. The main research contents and conclusions are as follows: 1) carrying out the ultrasonic testing test on the cured concrete test piece containing the different shape parameter cracks, and adopting the signal processing technology such as fast Fourier transform and wavelet analysis to realize the extraction of the acoustic wave signal parameters, The influence of the existence of the crack under the zero stress state on the ultrasonic parameters of the concrete is studied. The test shows that under the condition of zero stress, the wave velocity of the crack in the concrete test piece is less than that in the test piece, but the change of the crack size is small, it is difficult to distinguish, the crack width is obviously affected by the wave velocity, the depth is the second, In that condition of zero stress, the acoustic parameters of the concrete are obtained by the method of fast Fourier transform and frequency spectrum analysis. And the maximum amplitude value is the largest when the crack trend coincides with the acoustic wave propagation direction, and the maximum amplitude value of the time domain is the largest when the crack moves to be perpendicular to the sound wave propagation direction. In addition to the main frequency, the parameters of each parameter are similar with the change of the shape parameters of the crack. The influence of the crack on the maximum amplitude and the spectral area of the frequency domain is the same, which decreases with the increase of the size of the crack. In that case of crack in the specimen under load condition, the basic law is that the larger the crack size, the faster the wave velocity decreases with the stress change, and the smaller the minimum value of the wave velocity when the specimen is broken. The effect of crack depth on the test piece's wave velocity and stress sensitivity is weak compared with the crack width. when the included angle between the crack and the propagation direction of the ultrasonic wave is different, the crack is coincident with the propagation direction of the ultrasonic wave, that is, when the included angle is 0 degree, The high-frequency interference is filtered to a certain extent and the difference of the weights between different scales is taken into account, and the sensitivity to the stress is strong. The change of the weighted spectral area of the test piece with different shape parameters is basically the same, that is, with the increase of the stress, the larger the crack size and the change of the weight spectrum area. The weighted main frequency amplitude and the weighted spectral area are about the same as the stress change trend, and are sharply reduced after exceeding 70% of the limit stress of the test piece, which can be caused by the crack penetration, indicating that the irreversible plastic deformation occurs, The test piece has been close to the damage.5) The main frequency is not related to the internal structure state and the external stress state of the concrete. Under the condition of zero stress, the existence of cracks in the test piece has little influence on the main frequency, under the load condition, with the increase of the stress, the main frequency is basically not changed by 6), and by analyzing the relation between the defect scale and the ultrasonic wave length in the zero stress state, the equivalent elastic parameter containing the crack concrete is utilized. The change of the ultrasonic slowness caused by the distribution of different defects in the zero-stress state is established. By analyzing the extension action mechanism of the micro-crack under the influence of a single micro-crack and the concrete damage constitutive relation of a single micro-crack propagation, a concrete damage constitutive model characterized by acoustic parameters is established, and the theory is compared with the test result. The results show that the concrete damage constitutive model expressed by the wave velocity can better reflect the influence of the stress change on the wave velocity.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
本文编号：2494770
[Abstract]:In the process of use, due to the factors such as long-term load, environmental corrosion, material aging and component breakage, the damage and accumulation are gradually generated in the concrete, so that the bearing capacity and the durability of the structure can be reduced, and the service life of the structure is reduced. How to predict the damage and evolution of active concrete is one of the key problems to be solved urgently. In view of this, on the basis of the theory of linear and non-linear acoustic wave, this paper studies the relationship between the morphological parameters and the wave propagation characteristics of the concrete concealed crack, and provides the theoretical basis and application reference for the better realization of the concrete material detection. The main research contents and conclusions are as follows: 1) carrying out the ultrasonic testing test on the cured concrete test piece containing the different shape parameter cracks, and adopting the signal processing technology such as fast Fourier transform and wavelet analysis to realize the extraction of the acoustic wave signal parameters, The influence of the existence of the crack under the zero stress state on the ultrasonic parameters of the concrete is studied. The test shows that under the condition of zero stress, the wave velocity of the crack in the concrete test piece is less than that in the test piece, but the change of the crack size is small, it is difficult to distinguish, the crack width is obviously affected by the wave velocity, the depth is the second, In that condition of zero stress, the acoustic parameters of the concrete are obtained by the method of fast Fourier transform and frequency spectrum analysis. And the maximum amplitude value is the largest when the crack trend coincides with the acoustic wave propagation direction, and the maximum amplitude value of the time domain is the largest when the crack moves to be perpendicular to the sound wave propagation direction. In addition to the main frequency, the parameters of each parameter are similar with the change of the shape parameters of the crack. The influence of the crack on the maximum amplitude and the spectral area of the frequency domain is the same, which decreases with the increase of the size of the crack. In that case of crack in the specimen under load condition, the basic law is that the larger the crack size, the faster the wave velocity decreases with the stress change, and the smaller the minimum value of the wave velocity when the specimen is broken. The effect of crack depth on the test piece's wave velocity and stress sensitivity is weak compared with the crack width. when the included angle between the crack and the propagation direction of the ultrasonic wave is different, the crack is coincident with the propagation direction of the ultrasonic wave, that is, when the included angle is 0 degree, The high-frequency interference is filtered to a certain extent and the difference of the weights between different scales is taken into account, and the sensitivity to the stress is strong. The change of the weighted spectral area of the test piece with different shape parameters is basically the same, that is, with the increase of the stress, the larger the crack size and the change of the weight spectrum area. The weighted main frequency amplitude and the weighted spectral area are about the same as the stress change trend, and are sharply reduced after exceeding 70% of the limit stress of the test piece, which can be caused by the crack penetration, indicating that the irreversible plastic deformation occurs, The test piece has been close to the damage.5) The main frequency is not related to the internal structure state and the external stress state of the concrete. Under the condition of zero stress, the existence of cracks in the test piece has little influence on the main frequency, under the load condition, with the increase of the stress, the main frequency is basically not changed by 6), and by analyzing the relation between the defect scale and the ultrasonic wave length in the zero stress state, the equivalent elastic parameter containing the crack concrete is utilized. The change of the ultrasonic slowness caused by the distribution of different defects in the zero-stress state is established. By analyzing the extension action mechanism of the micro-crack under the influence of a single micro-crack and the concrete damage constitutive relation of a single micro-crack propagation, a concrete damage constitutive model characterized by acoustic parameters is established, and the theory is compared with the test result. The results show that the concrete damage constitutive model expressed by the wave velocity can better reflect the influence of the stress change on the wave velocity.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
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