基于宽频信号的板中缺陷检测

发布时间：2018-03-21 23:13

本文选题：Chirp信号　切入点：缺陷辨识　出处：《上海应用技术学院》2015年硕士论文　论文类型：学位论文

【摘要】：板型结构具有覆盖面广,易于组合形成大的空间体积和表面覆盖,在现今航空航天、风力发电、汽车制造等领域有着广泛应用。设备在长期的使用中会因材料老化、外界侵蚀或撞击而出现不同类型的损伤,影响正常的工作运转。进行板型结构健康监测和缺陷检测,对保证结构的完整性、运行的安全性、提高设备使用寿命等具有重要意义。本文通过有限元模拟和实验两种方式分析Lamb波对不同板中缺陷的检测效果,使用宽频Chirp信号作为激励信号。实验中将Chirp信号加载到压电片换能器(PZT)上激励Lamb波,再由Chirp响应计算得到相同条件下Tone burst激励结果。主要研究内容及成果如下：(1)使用Abaqus有限元模拟软件建立铝板有限元模型,用Chirp信号激励S0模态导波,分析矩形、椭圆形两种穿透缺陷散射到一检测点的波形；由接收到的Chirp响应计算得到模型在不同中心频率5周期Tone burst信号以相同激励加载方式下对应模拟结果；通过计算得到的各缺陷对不同中心频率Tone burst散射信号首次抵达波包峰值组成频率-幅值序列,表征缺陷信息。经BP神经网络对频率-幅值序列进行训练和测试,实现缺陷类型和几何尺寸的辨识。(2)详细描述了椭圆成像算法实现原理。结合Chirp信号和有限元模拟方法分析不同中心频率Tone burst激励Lamb波响应对6mm边长矩形穿透缺陷的成像定位,观察不同频率缺陷散射信号椭圆定位的精度。发现随着激励信号频率的提高,缺陷定位的精度亦出现提升。(3)分析了板中9mm直径穿透缺陷散射信号各向分布情况。基于缺陷对导波传播的干扰效应,分析对称式检测位排布情况下接收信号的差异。利用对称检测位接收信号之差为两检测位接收散射信号之和的特点,提出对称式检测位排布无基准缺陷定位算法。通过有限元模拟验证该算法的正确性,实现缺陷定位成像。并介绍了该算法在实际实验中面临的一些问题。(4)使用Chirp信号作为激励,实验分析16层T300/QY8911碳纤维复合材料板结构中不同频率Lamb波传播速度各向分布。分析了缺陷所处位置和激励接收换能器路径间的关系对接收信号的影响,通过具有阴影效应路径确定板中缺陷位置,缺陷是由直径30mm的钢柱通过横波耦合剂耦合到结构表面模拟而成。结合邻近激励接收传感器路径基准信号和各频率散射信号首次抵达波抵达时刻实现单个缺陷损伤区域的成像。
[Abstract]:Plate structure has a wide coverage, easy to form a large space volume and surface cover, which is widely used in aerospace, wind power generation, automobile manufacturing and other fields. Equipment in long-term use will be due to material aging, Different types of damage occur due to external erosion or impact, which affect normal working operation. Health monitoring and defect detection of plate structure can ensure the integrity of the structure and the safety of operation. It is of great significance to improve the service life of equipment. In this paper, the effect of Lamb wave on the detection of defects in different plates is analyzed by means of finite element simulation and experiment. The Chirp signal is loaded into the piezoelectric transducer to excite the Lamb wave by using the broadband Chirp signal as the excitation signal. Then the results of Tone burst excitation under the same conditions are obtained by Chirp response calculation. The main contents and results are as follows: 1) the finite element model of aluminum plate is established by using Abaqus finite element simulation software, the S0 mode guided wave is excited by Chirp signal, and the rectangle is analyzed. From the received Chirp response, the simulation results of the model are obtained under the same excitation loading mode for the Tone burst signals with different central frequencies. The Tone burst scattering signals with different center frequencies are calculated to form the frequency amplitude sequence for the first time to represent the defect information. The frequency amplitude sequence is trained and tested by BP neural network. In this paper, the principle of elliptical imaging algorithm is described in detail, and the imaging localization of Lamb waves excited by Tone burst at different center frequencies is analyzed by using Chirp signal and finite element simulation method. The accuracy of elliptical localization of scattering signals with different frequencies is observed. It is found that with the increase of the frequency of excitation signals, The distribution of 9mm diameter penetrating defect scattering signal in the plate is analyzed. Based on the interference effect of the defect on the guided wave propagation, the distribution of the scattering signal of the 9mm diameter penetrating defect in the plate is analyzed. This paper analyzes the difference of the received signal in the case of symmetrical detection bit arrangement. Using the difference of the symmetrical detection bit reception signal to be the sum of the received scattering signals of the two detection bits, In this paper, a new algorithm for locating defects without reference in symmetrical position detection is proposed. The correctness of the algorithm is verified by finite element simulation, and the defect location imaging is realized. Some problems faced by the algorithm in practical experiments are also introduced. The Chirp signal is used as the excitation. The velocity distribution of Lamb wave at different frequencies in 16-layer T300/QY8911 carbon fiber composite plate structure is analyzed experimentally. The influence of the position of defect and the path of exciting receiving transducer on the received signal is analyzed. The defect location in the plate is determined by a path with a shadow effect, The defect is simulated by the steel column with diameter 30mm coupled to the surface of the structure by means of a shear wave coupling agent. The imaging of a single defect damage region is realized by combining the reference signal of the path of the adjacent excitation receiving sensor and the scattering signal of each frequency at the first arrival time of the wave.
【学位授予单位】：上海应用技术学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB302.5

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