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

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Art of electronics

http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

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

Surface integrity in material removal processes: Recent advances

Experimental data have demonstrated that damage induced by alkali-silica reaction (ASR) in concrete, even in its very early stage, can cause changes in the acoustic nonlinearity parameter β. This provides a means to characterize ASR damage in concrete nondestructively. However, there is currently no model that explains the relationship between the acoustic nonlinearity parameter and ASR damage. In this work, we present a micromechanics-based chemo-mechanical model that relates the acoustic nonlinearity parameter to ASR damage. The mechanical part of the model is developed based on a modified version of the generalized self-consistent theory. The chemical part of the model accounts for two opposing diffusion processes. One is the diffusion of alkali ions in the pore solution into aggregates, and the other is the permeation of ASR gel from the aggregate surface into the surrounding porous cement matrix. Furthermore, a fracture model is used to simulate crack initiation and growth, so that the crack density and total expansion can be obtained. Finally, the acoustic nonlinearity parameter is determined as a function of exposure time by accounting for the gel pressure and the crack density. This model provides a way to quantitatively predict the changes in the acoustic nonlinearity parameter due to ASR damage, which can be used to guide experimental measurements for nondestructive evaluation of ASR damage.

A chemo-mechanical model for the acoustic nonlinearity change in concrete with alkali-silica reactions

Problems of dynamic fracture have been studied, both theoretically and experimentally, to obtain information about unstable crack extension and arrest. Investigation of bodies containing stationary cracks subjected to rapidly varying applied loads, show: (1) crack initiation; (2) dynamic crack growth; and (3) crack arrest are the dominant features. Experimental observations show that a stationary crack, subjected to a pulse loading, begins to propagate at sometime after the transient loading is applied [1–4]. It is also observed that this elapsed time varies with the magnitude of the pulse loading only [3,4]. Homma et al [5] examined the time history, of the crack-tip, of a semi-infinite Mode I crack under a finite duration pulse load. In this approach, Freund’s fundamental solution [6] was utilized and the crack initiation and arrest times were obtained in closed form. A more complete and detailed analysis of the same approach was given by Freund [7].

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2769&context=qnde

Crack Initiation and Arrest under Dynamic Loading

This research develops an analytical model (using Stroh’s formalism) to predict the affect of applied stress on the wave speed and the polarization of Rayleigh surface waves. Simulation results are then used to demonstrate that the polarization of a Rayleigh wave (which is reference-free) could be more sensitive than wave speed as an indicator of the state of stress.

Short communication Relationship between Rayleigh wave polarization and state of stress

Laser ultrasonic techniques are used to investigate interfacial losses in concrete. The experimental methodology uses a pulse ruby laser for optical generation and a heterodyne interferometer for laser detection. Concrete is a heterogeneous material made up of both fine and coarse aggregate. The presence of this aggregate, in addition to voids and flaws, causes elastic wave scattering in concrete. This study examines the propagation of ultrasonic waves in both “plain” mortar and concrete. In addition, it develops a one-dimensional model for the losses due to the interface between the mortar and the aggregate. Laser ultrasonic techniques are essential for this study because they allow for the broad band generation and detection of ultrasonic waves without influencing their frequency content.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=2087&context=qnde

Investigation of Interfacial Losses in Concrete with Laser Ultrasonics

The complete physical process of the nonlinear reflection of an incident P‐wave from a stress‐free boundary has been investigated analytically. The objective of this research is to evaluate the feasibility of using the second harmonic generation technique in reflection mode. The primary wave field consists of an incident plane P‐wave and linearly reflected P‐ and SV‐waves. Self‐ and cross‐interaction of these primary waves generate secondary waves, which, together with the primary waves, produce the nonlinear stress field at the boundary. The involved nonlinear boundary value problem (BVP) is decomposed into two linear BVPs by perturbation and general solutions of them are given. The obtained solution for the secondary field shows that the generation of second harmonic waves in the bulk is strongly affected by the nonlinear stress field at the boundary. Changes in the second harmonic amplitudes upon the boundary reflection are calculated numerically for different angles of incidence for aluminum. The case...

Laurence J. Jacobs

Papers

A chemo-mechanical model for the acoustic nonlinearity change in concrete with alkali-silica reactions

Crack Initiation and Arrest under Dynamic Loading

Short communication Relationship between Rayleigh wave polarization and state of stress

Investigation of Interfacial Losses in Concrete with Laser Ultrasonics

Nonlinear reflection of an obliquely incident longitudinal wave at a free surface