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摘要随着材料科学和机械制造业的高速发展板状结构在航空航天工业、汽车工业、船舶工业以及压力锅炉和大型化工容器等方面均有广泛的应用。但由于板材在成型过程中难免会有各种缺陷，如分层，裂纹等，会对制件的安全使用造成严威胁，因此对各种应用于生产，生活中的板材定期进行检测，做到早发现严重缺陷及时处理具有十分重要的现实意义。
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本论文通过Lamb波无损检测对3mm厚铝板上的缺陷定位进行了研究，主要通过激励汉宁窗调制信号在铝板上进行扫描检测，用多点圆弧定位法对设定的缺陷进行相对精确地定位。使用汉宁窗调制信号作为激励信号，各个信号接收点接收信号，得到传输时间，再根据传播速度可得到每个接收点到激励点的距离，也就得到了各个传感器接位置的成像图，为了确定激励信号发射点的具体位置，将各接收传感器的定源图像依次加性融合成像，由于实验中激励压电片不同、信号线屏蔽噪声性能不佳、PZT粘合程度不同，所求的差值信号同理论有很大出入。为了更好的进行成像，对信号第一波包峰值以前的数据进行置零处理。同样的，单一的一对传感器无法确定缺陷的具体位置，所以我将各对传感器成像进行加型融合来确定其位置，经过此次叠加融合后，由各融合成像可以看出椭圆定位至少需要三对传感器信号。6768
综上所述，利用超声Lamb波技术对板状构件进行缺陷的可视化研究，具有重要的学术意义和很好的应用前景。
关键词：兰姆波；无损检测；缺陷成像；板结构；椭圆定位
Abstract With the materials science and the rapid development of machinery manufacturing sheet-like structure in the aerospace industry, automobile industry, shipbuilding industry as well as pressure boilers and large chemical containers, etc. are widely used. However, due to sheet metal forming process will inevitably be in a variety of defects such as delamination, cracks, etc., will cause serious parts of the safe use of threat, so the variety used in the production and life of the plate on a regular basis to detect, so early detection of serious flaws in a timely manner is of great practical significance.
This paper Lamb wave nondestructive detection of defects 3mm thick aluminum positioning of research, mainly by stimulating the modulation signal Hanning scan test on the aluminum plate with a circular multi-point positioning method set relatively accurate positioning defect . Hanning window used as an excitation signal modulated signals, each signal point of a received signal received, to obtain the transmission time, then the propagation velocity is obtained for each received point to the excitation point distance, will obtain the position of each sensor on imaging of, for excitation signal to determine the specific location of the launch point for each of the receiving sensor is incremented by a fixed source image fusion imaging, because different experimental excitation piezoelectric film, the signal line shield noise performance is poor, PZT bonded to different degrees, the required differential value signal with very different theory. For better imaging, the peak of the signal before the first wave of the data packet zero process. Similarly, a single pair of sensors can not determine the specific location of defects, so I will be adding each type of sensor fusion imaging to determine its location, after the superposition fusion, fusion imaging can be seen by the ellipse positioned at least three the sensor signal.
In summary, the use of ultrasound technology to the plate member Lamb wave defect visualization research has important academic significance and a good prospect.
Key Words：Lamb wave；Nondestructive testing；Defect imaging；Plate-like structure；Ellipse location
目 录
1绪论 1
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STC89C51单片机控制的机器鱼结构设计+电路图
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PD前馈结构的单臂机械手控制系统设计+源程序
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复杂多相空泡流动数值模拟与流场结构分析
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几种数据结构演示软件开发
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STC89C52单片机光开关的光纤型延迟线结构图
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含水簇的新型磷钼酸盐的合成与结构研究
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