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

Ultrasonic guided wave inspection is expanding rapidly to many different areas of manufacturing and in-service inspection. The purpose of this paper is to provide a vision of ultrasonic guided wave inspection potential aswe move forward into the new millennium. An increased understanding of the basic physics and wave mechanics associated with guided wave inspection has led to an increase in practical nondestructive evaluation and inspection problems. Some fundamental concepts and a number of different applications that are currently being considered will be presented in the paper along with a brief description of the sensor and software technology that will make ultrasonic guided wave inspection commonplace in the next century.

A Baseline and Vision of Ultrasonic Guided Wave Inspection Potential

Lamb waves are the most widely used acousto-ultrasonic guided waves for damage detection. The method is generally complicated by the coexistence of at least two highly dispersive modes at any given frequency. Furthermore pure Lamb wave modes may generate a variety of other modes by interacting with defects and/or by crossing different boundaries. Knowledge and understanding of Lamb wave propagation is important for reliable damage detection. However, the theoretical analysis of guided wave scattering forms an extremely difficult problem. This paper reports an application of the local interaction simulation approach for wave propagation in metallic structures. The focus of the analysis is on damage detection applications. The study also involves wave propagation in a piezoceramic actuator/sensor diffusion bond model in which one of the piezoceramics generates the thickness mode vibration. The simulated results are validated experimentally. The results show the potential of the method for wave propagation analysis in damage detection applications.

https://iopscience.iop.org/article/10.1088/0964-1726/12/5/018/pdf

Modelling of Lamb waves for damage detection in metallic structures: Part I. Wave propagation

Modelling of wave propagation in composite plates using the time domain spectral element method

The interaction of the low-order antisymmetric (a0) and symmetric (s0) Lamb waves with vertical cracks in aluminum plates is studied. Two types of slots are considered: (a) internal crack symmetrical with respect to the middle plane of the plate and (b) opening crack. The modal decomposition method is used to predict the reflection and transmission coefficients and also the through-thickness displacement fields on both sides of slots of various heights. The model assumes strip plates and cracks, thus considering two-dimensional plane strain conditions. However, mode conversion (a0 into s0 and vice versa) that occurs for single opening cracks is considered. The energy balance is always calculated from the reflection and transmission coefficients, in order to check the validity of the results. These coefficients together with the through-thickness displacement fields are also compared to those predicted using a finite element code widely used in the past for modeling Lamb mode diffraction problems. Experiments are also made for measuring the reflection and transmission coefficients for incident a0 or s0 lamb modes on opening cracks, and compared to the numerical predictions.

Modal decomposition method for modeling the interaction of Lamb waves with cracks

Absfrucf-A method ol the solution of scattering of the fundamental symmetric Lamb wave in an elastic plate waveguide is described. The approach is a combination of the finite-element and the analytical method. The numerical examples on the scattering by a wedge-shaped internal crack and a wedge-shaped surface crack in a plate are given. The reflection coefficient of the internal crack is considerably influenced by the wedge apex angle and the resonance phenomena arise in the region of the crack. On the other hand, the reflection coefficient of the surface crack is not very much affected by the wedge apex angle. The validity of the method is confirmed by comparing numerical results for an infinitely thin internal crack normal to the surface of a plate with the results of the variational method.

/pdf/finite-element-analysis-of-lamb-wave-scattering-in-an-18t65ykmkq.pdf

M. Suzuki

Papers

Finite-Element Analysis of Lamb Wave Scattering in an Elastic Plate Waveguide