Staff members at Los Alamos National Laboratory (LANL) produced a summary of the structural health monitoring literature in 1995. This presentation will summarize the outcome of an updated review covering the years 1996 2001. The updated review follows the LANL statistical pattern recognition paradigm for SHM, which addresses four topics: 1. Operational Evaluation; 2. Data Acquisition and Cleansing; 3. Feature Extraction; and 4. Statistical Modeling for Feature Discrimination. The literature has been reviewed based on how a particular study addresses these four topics. A significant observation from this review is that although there are many more SHM studies being reported, the investigators, in general, have not yet fully embraced the well-developed tools from statistical pattern recognition. As such, the discrimination procedures employed are often lacking the appropriate rigor necessary for this technology to evolve beyond demonstration problems carried out in laboratory setting.

A review of structural health monitoring literature 1996-2001

Guided Lamb waves for identification of damage in composite structures: A review

The capability of embedded piezoelectric wafer active sensors (PWAS) to excite and detect tuned Lamb waves for structural health monitoring is explored. First, a brief review of Lamb waves theory is presented. Second, the PWAS operating principles and their structural coupling through a thin adhesive layer are analyzed. Then, a model of the Lamb waves tuning mechanism with PWAS transducers is described. The model uses the space domain Fourier transform. The analysis is performed in the wavenumber space. The inverse Fourier transform is used to return into the physical space. The integrals are evaluated with the residues theorem. A general solution is obtained for a generic expression of the interface shear stress distribution. The general solution is reduced to a closed-form expression for the case of ideal bonding which admits a closed-form Fourier transform of the interfacial shear stress. It is shown that the strain wave response varies like sin a, whereas the displacement response varies like sinc a. ...

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Tuned Lamb-Wave Excitation and Detection with Piezoelectric Wafer Active Sensors for Structural Health Monitoring

Preface Acknowledgments 1. Introduction 2. Dispersion principles 3. Unbounded isotropic and anisotropic media 4. Reflection and refraction 5. Oblique incidence 6. Waves in plates 7. Surface and subsurface waves 8. Finite element method for guided wave mechanics 9. The semi-analytical finite element method (SAFE) 10. Guided waves in hollow cylinders 11. Circumferential guided waves 12. Guided waves in layered structures 13. Source influence on guided wave excitation 14. Horizontal shear 15. Guided waves in anisotropic media 16. Guided wave phased arrays in piping 17. Guided waves in viscoelastic media 18. Ultrasonic vibrations 19. Guided wave array transducers 20. Introduction to guided wave nonlinear methods 21. Guided wave imaging methods Appendix A: ultrasonic nondestructive testing principles, analysis and display technology Appendix B: basic formulas and concepts in the theory of elasticity Appendix C: physically based signal processing concepts for guided waves Appendix D: guided wave mode and frequency selection tips.

Ultrasonic Guided Waves in Solid Media

Guided wave signal processing and image fusion for in situ damage localization in plates

Damage detection in composite laminated panels using Lamb waves is demonstrated with an innovative use of a sensor array and processing algorithm. Two models were developed to characterize the Lamb wave propagation properties of orthotropic panels. Predictions of the dispersion relations were made for a fiber-reinforced composite laminate. Experiments were conducted to empirically characterize the wave propagation behavior in a manufactured laminate. Piezoelectric patches were used as sensors and actuators in the experiments. Comparisons were made between analytical predictions and experimental results, which demonstrate that the higher order model captured essential wave propagation behavior at frequencies of interest. Sensor arrays and associated processing were used for wavenumber decomposition and filtering of the Lamb wave modes. Composite laminates were manufactured with an embedded defect to simulate inter-ply delamination. Experiments were conducted to detect the presence of delamination damage in...

Damage Detection in Thin Composite Laminates Using Piezoelectric Phased Sensor Arrays and Guided Lamb Wave Interrogation

Phased array filters using piezoelectric sensors are presented as an approach to detect damage in isotropic plates. Plate dynamics can be described in terms of wave propagation. Boundaries and other discontinuities, such as damage, produce reflections from incident wavefronts. Phased arrays, acting as a directional filter, can be used along with a wave propagation approach to look in different directions on a plate. Damage to the plate can be inferred if there is a significant change in the transient response of the plate. The location of this damaged area can be determined using the phased sensor array response. This paper presents results from simulated damage on an isotropic plate. A piezoelectric sensor array is used to actively interrogate the plate to determine the presence and location of damage using low frequency Lamb waves.

http://iopscience.iop.org/article/10.1088/0964-1726/13/4/022/pdf

Directional piezoelectric phased array filters for detecting damage in isotropic plates

A damage detection method based on an innovative 2D phased sensor array made of piezoelectric paint is proposed for in situ damage detection of a thin isotropic panel using guided Lamb waves A design analysis of candidate 2D arrays based on spiral, cruciform and circular element layouts is performed In this study, a 2D phased sensor array with a spiral configuration is fabricated using a piezoelectric composite (piezopaint) patch and used for detecting damages in an aluminum panel Steered array responses are generated from the raw sensor signals using a directional filtering algorithm based on phased array signal processing The fundamental flexural (or transverse), A0 mode, of the guided Lamb waves is used though the sensing and analysis technique is not limited to the mode used in this work To enhance the proposed analysis technique, empirical mode decomposition (EMD) and a Hilbert–Huang transform (HHT) are applied A new damage detection algorithm including threshold setting and damage index (DI) calculation is developed and implemented for detecting damages in the form of holes and a simulated crack The characteristic damage indices consistently increase as damage size grows

https://iopscience.iop.org/article/10.1088/0964-1726/19/7/075017/pdf

Piezoelectric-paint-based two-dimensional phased sensor arrays for structural health monitoring of thin panels

This study addresses the experimental validation of a design methodology for an energy harvesting device utilizing macro-fiber composite (MFC) materials. The energy harvesting device is composed of...

Energy Harvesting Devices Using Macro-fiber Composite Materials:

This study presents the performance evaluation of a vibration-based energy harvester using macro-fiber composite (MFC) elements, which can harvest power from environmental or ambient vibration and shock. An innovative multi-tier energy harvester (MTEH), comprised of a small number of vibrating beam elements with same fundamental frequencies, is developed in this study to overcome the harvested power limitations of single-tier energy harvesters (STEHs) with only a single vibrating beam element. First, the governing equations of motion of an MTEH were theoretically obtained for series and parallel connections of pairs of MFC patches on each tier surface. Based on the theoretical model, a vibration-based MTEH, having three tiers with MFC patches adhered to the bottom and top of each tier surface, was designed and fabricated. MTEH performance, which included generated voltage, current, and power, was experimentally and theoretically evaluated in the frequency domain and compared with that of a similar STEH.

Ashish S. Purekar

Papers

Damage Detection in Thin Composite Laminates Using Piezoelectric Phased Sensor Arrays and Guided Lamb Wave Interrogation

Directional piezoelectric phased array filters for detecting damage in isotropic plates

Piezoelectric-paint-based two-dimensional phased sensor arrays for structural health monitoring of thin panels

Energy Harvesting Devices Using Macro-fiber Composite Materials:

Performance Evaluation of Multi-tier Energy Harvesters Using Macro-fiber Composite Patches