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

Lamb waves can propagate over long distances which means that they are attractive for the quick, long range inspection of large structures, and they can also be useful for localized inspection, particularly in thin structures. This paper discusses the selection of the appropriate mode and frequency range for different inspection requirements and reviews the possible methods of excitation, response measurement and signal processing. It is usually desirable to transmit a single, non-dispersive mode, and excitation methods to achieve this are discussed. A variety of signal processing techniques from simple time domain to relatively complex two-dimensional Fourier analysis are available. Time domain processing can often be applied satisfactorily in low frequency-thickness regions where only two modes can propagate, but tends to be unreliable above the cut-off frequency of the a 1 mode. As an example of the design of a Lamb wave testing regime, a set of tests on a butt-welded steel plate with simulated weld defects of different depths is described. It is shown that by operating below the a 1 cut-off frequency with judicious selection of testing technique, the presence of defects can be detected reliably from changes in the shape of the received waveform.

Optimization of Lamb wave inspection techniques

Wave propagation in layered composite laminates under periodic surface loads

A method with which standard finite element programs can be used to compute dispersion relations in periodic composites is proposed. The method is applied to two composite microstructures: a two-phase laminate and a fiber composite. The dispersion relations computed for the laminate are compared with a known analytical solution and the agreement is very good. The dispersion relations computed for the fibrous composite are compared with an existing approximate model and experimental results from the literature. The agreement between the approximate model, the experiments, and the computations is very good in the wave guide case and satisfactory for the wave reflect case.

The usage of standard finite element codes for computation of dispersion relations in materials with periodic microstructure

A semi-analytical finite element formulation for modeling stress wave propagation in axisymmetric damped waveguides

A stiffness method has been used in this article to study dispersive wave propagation in a laminated anisotropic plate. The advantage of this method is in its usefulness in obtaining numerical results for the dispersion characteristics of waves propagating in a plate with an arbitrary number of arbitrarily anisotropic laminae. This method has been applied here, as a way of illustration, to a plate made up of transversely isotropic laminae with the axis of isotropy of each lamina lying in the plane of the lamina. Results thus obtained are shown to agree well with the exact solutions for isotropic and transversely isotropic single layered plates. Numerical results are presented for cross‐ply (0°/90°/0°) laminated composite plates and show that the frequency spectrum in this case differs considerably from that for a single layered (0°) plate.

Wave propagation in laminated composite plates

Elastic wave propagation in laminated composite plates

Elastic Wave Propagation in Laminated Composite Plates

Transient response of a laminated composite plate: Results from homogenization and discretization

Inspection of coated material is vital in order to ensure the integrity of the protective barrier. In some cases, the inspection process is complicated by the fact that the surface of the protective coating may not be accessible, thus the inspection must proceed with only access to the surface of the opposite side (this will be referred to as the inner surface). One method which can be applied in such a situation is the excitation of guided waves or Lamb waves in the coated material. Lamb waves excited from the inner surface will sense the variation in the coating conditions as well as flaws in the steel plate. Therefore for a correct and unambiguous interpretation of Lamb wave data for corrosion-related flaws, the effects of the coating and how they differ from the effects of corrosion-related flaws must be understood. To this end this paper will concentrate on the effects of the coating and its influence on dispersive characteristics of a soft layer bonded to a steel plate. By calculating the dispersion relations for a bare and coated steel plate and comparing the calculated results, unique new modes are seen to emerge in the coated plate. In addition, the coated plate is also modeled as a thin layer on a halfspace allowing a comparison between the problem of a coated halfspace and a coated plate. The comparison demonstrates that only limited information can be obtained by treating the problem as a layered halfspace. More detailed information can be obtained by treating the problem as a coated plate of finite thickness.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2913&context=qnde

R. L. Bratton

Papers

Wave propagation in laminated composite plates

Elastic wave propagation in laminated composite plates

Elastic Wave Propagation in Laminated Composite Plates

Transient response of a laminated composite plate: Results from homogenization and discretization

Analysis of Guided Waves in a Bilayered Plate