The nondestructive assessment of the damage that occurs in components during service plays a key role for condition monitoring and residual life estimation of in-service components/structures. Ultrasound has been widely utilized for this; however most of these conventional methods using ultrasonic characteristics in the linear elastic region are only sensitive to gross defects but much less sensitive to micro-damage. Recently, the nonlinear ultrasonic technique, which uses nonlinear ultrasonic behavior such as higher-harmonic generation, subharmonic generation, nonlinear resonance, or mixed frequency response, has been studied as a positive method for overcoming this limitation. In this paper, overall progress in this technique is reviewed with the brief introduction of basic principle in the application of each nonlinear ultrasonic phenomenon.

Nonlinear ultrasonic techniques for nondestructive assessment of micro damage in material: A review

Ultrasonics of non-linear contacts: propagation, reflection and NDE-applications

Modelling of nonlinear crack–wave interactions for damage detection based on ultrasound—A review

Nonlinear interaction between elastic wave and contact interface, known to result in the so-called contact acoustic nonlinearity, is examined in a one-dimensional theoretical framework. The present analysis is based on a nonlinear interface stiffness model where the stiffness property of the contact interface is described as a function of the nominal contact pressure. The transmission/reflection coefficients for a normally incident harmonic wave, and the amplitudes of second harmonics as well as DC components arising at the contact interface are derived in terms of the interface stiffness properties and other relevant acoustic parameters. Implications of power-law relations between the linear interface stiffness and the contact pressure are examined in detail regarding the linear and nonlinear acoustic responses of the contact interface. Also, a plausible range of the relevant power-law exponent is provided from considerations based on the rough-surface contact mechanics. The analysis clarifies the qualitative contact-pressure dependence of various nonlinearity parameters based on different definitions, A particular power law is identified from existing experimental data for aluminum-aluminum contact, for which some explicit nonlinear characteristics are demonstrated. The theoretical contact-pressure dependence of the second harmonic generation at the contact interface is found to be in qualitative agreement with previous measurements.

On the Acoustic Nonlinearity of Solid-Solid Contact With Pressure-Dependent Interface Stiffness

The nonlinear acoustic applications for material characterization are reviewed. The general theoretical analysis of the effects of nonlinearity, dissipation, dispersion, and diffraction on intense ...

Review / Sythèse Nonlinear acoustic applications for material characterization: A review

CAN: an example of nonclassical acoustic nonlinearity in solids

DC effects, sub-harmonics, stochasticity and "memory" for contact acoustic non-linearity.

Non-linear SAW reflection: experimental evidence and NDE applications

The threshold initiation of popping nonlinearity of the interface as a result of the breaking and subsequent restoration of contact between the boundary surfaces is observed. It is shown that instability and the generation of chaotic vibrations by evolution of successsive multiple bifurcations or the period of the boundary vibrations will be observed at small contact pressures. It is also shown that a square wave popping nonlinearity associated with collisions of the vibrating fre contact surfaces can occur when an initial gap slightly smaller than the vibration amplitude exixts between the surfaces of the contact interface

``Popping'' nonlinearity and chaos in vibrations of a contact interface between solids

Results are reported of an experimental study and NDE applications for the focused slanted transmission mode (FSTM) of air-coupled ultrasound. The FSTM is based on the “resonance” transmission of an acoustic wave through the sample due to Lamb mode excitation and re-radiation. For oblique incidence, the azimuth rotation of the sample changes the direction and phase velocity of the plate wave propagating in anisotropic material. It was shown that to discern the in-plain elastic anisotropy of the plate-like sample one could use the measurements of amplitude and phase of the FSTM-output signal as functions of the azimuth angle. Such an interference technique is shown to be extremely sensitive in discerning the directions of reinforcement in composites and orientation of crystalline Si-wafers. The mechanisms of substantial contrast enhancement demonstrated for the FSTM C-scan imaging of the cracked defects and delaminations in polymers and composites also are discussed.

I. Yu. Solodov

Papers

CAN: an example of nonclassical acoustic nonlinearity in solids

DC effects, sub-harmonics, stochasticity and "memory" for contact acoustic non-linearity.

Non-linear SAW reflection: experimental evidence and NDE applications

``Popping'' nonlinearity and chaos in vibrations of a contact interface between solids

Material characterization and nde using focused slanted transmission mode of air-coupled ultrasound