Analysis and Modeling of Diffuse Ultrasonic Signals for Structural Health Modeling

漫反射超声波信号的结构健康监测分析与建模随着用于测量温度、湿度和应变等物理量的传感器变得更小、更可靠，使用永久安装的传感器来监测飞机、桥梁和建筑物等关键结构的健康状况正迅速成为现实。然而，这些设备仅限于点或局部测量，因此不能真正询问结构的体积状态。稀疏阵列的永久安装的超声波传感器，作为源和接收器，可以将超声波能量发送到整个结构体积，从而有可能检测到关键变化。在这一目标成为现实之前，必须在接收到的超声波信号的分析和处理方面取得革命性的进展，以便能够以可接受的低误报率可靠地检测到可能导致灾难性故障的结构变化。一个显著的复杂性是，良性的环境影响，如温度和表面条件的变化，可以导致更大的变化，在超声波信号比实际的缺陷。智力优点：这里提出的研究是一个实验和波形建模相结合，并考虑发展和验证的信号处理，分类和识别方法的基础上定量变化的超声波信号。考虑的测试模式是扩散超声波，从而一个点样的脉冲激励被用来产生多modalelastic波，充满了声音的结构。超声扩散波理论模拟了能量衰减的速率，但不能预测复杂时域信号的细节。拟议的研究将联合收割机的时间相关的相干性分析与特征提取，分类方法，信号建模和仿真，以及数据融合，以解决具有挑战性的问题，检测和表征损伤。一个固有的问题，在使用分类方法，如神经网络为这个应用程序是需要有一个大的信号集，从各种各样的缺陷，这是不切实际的结构外的实验室。本研究的一个关键方面是发展一种方法来扰动来自未受损结构的基线信号，以模拟各种各样的结构和环境变化。信号处理和分类方法。发展定量微分方法来确定信号变化是否是由于结构或环境影响，并表征结构变化的位置，严重程度，类型等。漫射超声信号的建模与仿真。漫射超声波信号的建模，以及环境和结构变化的模拟.传感器放置和数据融合。分析传感器的最佳组织和位置，以及多传感器数据的融合.实验测量的设计与实现。更广泛的影响：这一多学科的研究计划将导致超声传感器的有效使用，用于持续监测关键结构的健康状况，这将使适当的行动发生之前，灾难性的故障。此外，所开发的方法将广泛应用于其他学科，如声纳，雷达和生物医学信号处理。教育影响的一个关键部分是本科生和研究生的参与，并将作出协调努力，招募妇女和代表性不足的少数民族。还提出了在超声波传播和信号处理的研究生课程的发展，将声波和弹性波传播的基础与信号处理方法相结合，适用于超声波。这项研究计划还将补充格鲁吉亚理工学院的其他工作，有效地创造了一个临界质量的研究超声波结构健康监测。

Analysis and Modeling of Diffuse Ultrasonic Signalsfor Structural Health MonitoringThe use of permanently mounted sensors to monitor the health of critical structures such as airplanes,bridges and buildings is quickly becoming a reality as sensors for measuring such physical quantities astemperature, moisture and strain become smaller and more robust. However, these devices are limitedto point, or local, measurements and thus do not truly interrogate the volumetric state of the structure.Sparse arrays of permanently mounted ultrasonic sensors, acting as both sources and receivers, can sendultrasonic energy throughout the entire structural volume and thus have the potential to detect criticalchanges. Before this goal can become a reality, revolutionary advances must be made in the analysisand processing of the received ultrasonic signals so that structural changes that may lead to catastrophicfailure can be reliably detected with an acceptably low false alarm rate. A significant complication isthat benign environmental effects such as changes in temperature and surface conditions can causelarger changes in the ultrasonic signals than actual flaws.Intellectual Merit: The research proposed here is a combination of experiments and waveformmodeling, and considers the development and verification of signal processing, classification and datafusion methods based upon quantitative changes in the ultrasonic signals. The testing mode consideredis that of diffuse ultrasonic waves whereby a point-like impulsive excitation is used to generate multi-modalelastic waves that fill the structure with sound. Ultrasonic diffuse wave theory models the rateof energy decay but does not predict the details of the complex time domain signals. The proposedresearch will combine time-dependent analysis of coherence with feature extraction, classificationmethods, signal modeling and simulation, and data fusion to tackle the challenging problem of detectingand characterizing damage. One inherent problem in using classification methods such as neuralnetworks for this application is the need to have a large set of signals from a wide variety of flaws; thisis not practical for structures outside the laboratory. A key aspect of the proposed research is todevelop methods for perturbing the baseline signal from the undamaged structure in order to emulate awide variety of structural and environmental changes.Four tasks are defined as follows:1. Signal Processing and Classification Methods. Development of quantitative differential methods todetermine if signal changes are due to structural or environmental effects, and to characterizestructural changes as to location, severity, type, etc.2. Modeling and Simulation of Diffuse Ultrasonic Signals. Modeling of diffuse ultrasonic signals, andsimulation of environmental and structural changes.3. Transducer Placement and Data Fusion. Analysis of optimum transducer organization andplacement, and fusing of data from multiple transducers.4. Design and Implementation of Experimental Measurements. Ultrasonic diffuse wavemeasurements using metallic, composite and cement-based structures.Broader Impact: This multidisciplinary research program will lead to effective use of ultrasonicsensors for continuously monitoring the health of critical structures, which will enable appropriateaction to take place prior to catastrophic failure. Furthermore, the methodologies developed will havebroad application to other disciplines such as sonar, radar and biomedical signal processing. A key partof the educational impact is the participation of undergraduates as well as graduate students, and aconcerted effort will be made to recruit women and underrepresented minorities. Also proposed is thedevelopment of a graduate course in ultrasonic wave propagation and signal processing that willcombine the fundamentals of acoustic and elastic wave propagation with signal processing methods asapplied to ultrasonics. This research program will also complement other efforts at Georgia Tech,effectively creating a critical mass of research in ultrasonics for structural health monitoring.