径向压电超声传感器在混凝土检测中的应用

发布时间：2018-05-30 17:30

本文选题：超声波检测技术 + 径向压电超声传感器　；参考：《济南大学》2016年硕士论文

【摘要】：近几十年来,建筑行业随经济发展得到了快速发展。混凝土材料不仅被广泛应用于建筑领域中,还被广泛应用于道路和桥梁的建设中,其工程质量与混凝土的结构质量息息相关。工程结构受到各种因素的综合作用,使其不断老化,结构的安全性和耐久性问题也日渐严峻,因此对混凝土结构进行检测具有重要的意义。因压电陶瓷的响应快、价格低和频带宽等性能优点,被广泛应用于土木工程结构检测中。此外,压电陶瓷具有自感知和自驱动的功能,所以基于压电陶瓷的混凝土结构检测得到了国内外学者的广泛关注。本文基于压电陶瓷的特性制备了一种新型径向压电超声传感器,将其应用于混凝土结构检测中,采用超声波检测技术检测混凝土强度以及缺陷。具体的研究工作如下:(1)本文基于压电陶瓷的特性,研究了一种适用于混凝土检测的植入式新型径向压电超声传感器。发射型传感器以PZT-41压电陶瓷管为传感元件,接收型传感器以PZT-52压电陶瓷管为传感元件,由背衬层和匹配层封装后组成。研究了径向压电超声传感器的匹配层厚度、线性度、灵敏度以及指向性四个方面的性能。研究结果表明:当匹配层的厚度设为2.5mm时,首波幅值为1.083V,此时径向压电超声传感器的灵敏度最高,接收的信号最优;此外,当径向压电超声传感器的激励频率为50kHz时,径向压电超声传感器的线性度最好,各传感器的线性相关系数比较相近,且此时灵敏度最高;最后研究发现径向压电超声传感器可以在360°方向上均匀发射和接收超声波信号,且四周发射和接收的信号是相似的。(2)本文制备了不同强度等级的混凝土试块,将发射型径向压电超声传感器埋入混凝土试块的中心位置,采用超声技术连续对混凝土前28天强度进行检测,分析所接收信号的声学参数与混凝土强度的关系,进而表征混凝土的强度。研究结果表明:超声波的传播速度随养护龄期的增加而逐渐增加,最终趋于平稳;与此同时主频向右偏移,即呈现频率增大的趋势,并且主频所对应的幅值也是逐渐增大的。通过声速与强度的拟合曲线得到回归方程,线性相关系数R值相对较高,即线性相关性较好,这表明声速与强度有很大的关系,即强度越大,声速越大。(3)采用MTS疲劳试验机对素混凝土梁进行三点弯曲测试,研究了超声信号的声时、幅值、频率等声学参数与混凝土裂纹之间的关系。研究发现,随着加载载荷的逐渐增大,接收波的波形出现比较杂乱的现象,并且连续出现几个波包;随着载荷的增大,声时出现延长的现象,幅值呈现先增大后减小的趋势。当素混凝土梁表面出现宏观的裂缝时,主频、幅值迅速减小,RMSD值大于0.8,其中以波幅的变化最为明显。因此,可以通过径向压电超声传感器接收信号的幅值、主频对应的幅值、RMSD值等参数的变化来表征混凝土的损伤状况。通过在混凝土内预制空洞,研究径向压电超声传感器接收信号的幅值、频率等参数随检测深度的变化,识别空洞的位置。研究发现:当检测深度为12cm时,传感器所接收的超声波信号的峰值为7.9mV,频率为39.67kHz。由统计学方法得出:在该深度时,混凝土内部存在空洞,这与实际预制空洞时的深度大致相符,因此制备的径向超声传感器可用于检测混凝土内的空洞。
[Abstract]:In recent decades, the construction industry has developed rapidly with the development of the economy. Concrete materials are not only widely used in the construction field, but also widely used in the construction of roads and bridges. The quality of the construction is closely related to the quality of the concrete structure. The engineering structure is subjected to a comprehensive effect of various factors, so that it is aging and structure. The problem of safety and durability is becoming more and more serious, so it is of great significance to detect the structure of concrete. Because of its fast response, low price and wide bandwidth, it is widely used in the detection of civil engineering structures. In addition, the piezoelectric ceramics have self sensing and self driving functions, so the mixture of piezoelectric ceramics is based on the mixing of piezoelectric ceramics. In this paper, a new type of radial piezoelectric ultrasonic sensor is prepared based on the characteristics of piezoelectric ceramics. It is applied to the test of concrete structure, and the ultrasonic testing technology is used to detect the strength and defects of concrete. The specific research work is as follows: (1) this paper is based on the piezoelectric ceramics. A new type of implantable radial piezoelectric ultrasonic sensor suitable for concrete detection is studied. The transmitter sensor uses PZT-41 piezoelectric ceramic tube as sensing element, and the receiving sensor takes PZT-52 piezoelectric ceramic tube as sensing element. The sensor is composed of the backing layer and the matching layer. The matched layer thickness of the radial piezoelectric ultrasonic sensor is studied. The results show that when the thickness of the matching layer is set to 2.5mm, the amplitude of the first wave is 1.083V, and the sensitivity of the radial piezoelectric ultrasonic sensor is the highest and the received signal is the best. In addition, when the excitation frequency of the radial piezoelectric ultrasonic sensor is 50kHz, the radial piezoelectric ultrasonic sensor is used. The linearity of the device is the best, the linear correlation coefficient of each sensor is similar and the sensitivity is the highest at this time. Finally, it is found that the radial piezoelectric ultrasonic sensor can transmit and receive the ultrasonic signals evenly in the direction of 360 degrees, and the signals around and received are similar. (2) the concrete test blocks with different strength grades are prepared in this paper. The radial piezoelectric ultrasonic sensor is embedded in the central position of the concrete block, and the strength of the concrete before 28 days is tested by ultrasonic technology. The relationship between the acoustic parameters of the received signal and the strength of concrete is analyzed, and the strength of concrete is characterized. The results show that the propagation speed of ultrasonic wave increases with the age of curing. At the same time, the main frequency shift to the right, at the same time, the frequency of the main frequency is increasing, and the amplitude of the main frequency is gradually increasing. The regression equation is obtained by the fitting curve of the sound velocity and the intensity. The linear correlation coefficient R value is relatively high, that is, the linear correlation is better, which indicates that the sound speed and the intensity are very good. The bigger the relationship is, the greater the strength and the greater the sound speed. (3) the MTS fatigue test machine is used to test the three point bending of the plain concrete beam, and the relationship between the acoustic parameters of the ultrasonic signal, amplitude, frequency and other acoustic parameters is studied. With the increase of the load, the sound time is prolonged and the amplitude appears to increase first and then decrease. When there is a macro crack on the surface of the plain concrete beam, the main frequency and amplitude decrease rapidly and the RMSD value is more than 0.8, and the amplitude is the most obvious. Therefore, the radial piezoelectric ultrasonic sensor can be used to connect it. The amplitude of the signal, the amplitude of the main frequency and the change of the RMSD value are used to characterize the damage of the concrete. The amplitude of the receiving signal of the radial piezoelectric ultrasonic sensor is studied by prefabricating the cavity in the concrete. The frequency and other parameters are identified with the change of the depth of the detection. The research shows that when the depth of detection is 12cm, the sensor is found. The peak value of the received ultrasonic signal is 7.9mV, and the frequency is 39.67kHz. by statistical method. At this depth, there is a hole in the concrete, which is approximately consistent with the depth of the actual prefabricated cavity. Therefore, the radial ultrasonic sensor prepared can be used to detect the void in the concrete.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU755.7;TP212

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