Issues on the pulse-width dependence and the shape of acoustic radiation induced static displacement pulses in solids
TL;DR: In this paper, a numerical simulation of the finite amplitude longitudinal ultrasonic wave propagation in solids has been performed to further verify the pulse width independence of the static displacement pulse and the flat top shape of static displacement.
Abstract: Recent experimental results showing the pulse width independence and the flat topped shape of static displacement generated during finite amplitude sinusoidal ultrasonic tone burst propagation in solids and the contradicting previous results reported in the literature are considered. The pulse width independence is analytically confirmed and the flat topped shape is explained by considering the progressive spatial and time domain shapes of the static strain and displacement pulses. A numerical simulation of the finite amplitude longitudinal ultrasonic wave propagation in solids has been performed to further verify the pulse width independence of the static displacement pulse.
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TL;DR: Harmonic generation from non-cumulative fundamental symmetric and antisymmetric modes in plate is studied from a numerical standpoint and the phenomenon of mode-interaction to generate sum and difference frequencies is demonstrated.
78 citations
TL;DR: In this article, the use of non-linear ultrasonic techniques for the characterization of material degradation in 99.98% pure copper due to high-temperature creep was described, where flat dog-bone-shaped specimens were subjected to constant load creep testing at different stress and temperature levels.
78 citations
TL;DR: In this article, a new nonlinear ultrasonic (NLU) technique for creep damage characterization is described, where dislocations are constrained between two quiescent lattice planes as defined by Cantrell.
53 citations
TL;DR: In this paper, the static component wave packets generated from the primary S0, A0 and S1 modes share the almost same group velocity equal to the phase velocity of S0 mode tending to zero frequency c plate.
Abstract: Under the discipline of nonlinear ultrasonics, in addition to second harmonic generation, static component generation is another frequently used nonlinear ultrasonic behavior in non-destructive testing (NDT) and structural health monitoring (SHM) communities. However, most previous studies on static component generation are mainly based on using longitudinal waves. It is desirable to extend static component generation from primary longitudinal waves to primary Lamb waves. In this paper, static component generation from the primary Lamb waves is studied. Two major issues are numerically investigated. First, the mode of static displacement component generated from different primary Lamb wave modes is identified. Second, cumulative effect of static displacement component from different primary Lamb wave modes is also discussed. Our study results show that the static component wave packets generated from the primary S0, A0 and S1 modes share the almost same group velocity equal to the phase velocity of S0 mode tending to zero frequency c plate . The finding indicates that whether the primary mode is S0, A0 or S1, the static components generated from these primary modes always share the nature of S0 mode. This conclusion is also verified by the displacement filed of these static components that the horizontal displacement field is almost uniform and the vertical displacement filed is antisymmetric across the thickness of the plate. The uniform distribution of horizontal displacement filed enables the static component, regardless of the primary Lamb modes, to be a promising technique for evaluating microstructural damages buried in the interior of a structure. Our study also illustrates that the static components are cumulative regardless of whether the phase velocity of the primary and secondary waves is matched or not. This observation indicates that the static component overcomes the limitations of the traditional nonlinear Lamb waves satisfying phase velocity matching condition to achieve cumulative second harmonic generation. This nature also enables the primary Lamb waves excited at a low center frequency to generate static component used for inspecting large-scale structures with micro-scale damages.
30 citations
TL;DR: It is shown that an eigenstrain is induced when a wave propagates through an elastic solid with quadratic nonlinearity, but the mean stress and the total mean strain are not.
Abstract: This letter demonstrates that an eigenstrain is induced when a wave propagates through an elastic solid with quadratic nonlinearity. It is shown that this eigenstrain is intrinsic to the material, but the mean stress and the total mean strain are not. Instead, the mean stress and total means strain also depend on the boundary conditions, so care must be taken when using the static deformation to measure the acoustic nonlinearity parameter of a solid.
26 citations
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TL;DR: In this article, the second-order acousto-elastic coefficient (SOC) was measured in a variety of materials including plastics, metals, composites and adhesives.
430 citations
TL;DR: In this article, a model of ultrasonic wave-dislocation dipole interactions is developed that quantifies the wave distortion by means of a material nonlinearity parameter (beta).
404 citations
TL;DR: In this article, the dislocation contribution to the generation of the second harmonic of an ultrasonic wave in solids is measured through the changes, as a function of static bias stress, in the amplitude of a fundamental wave (10 Mc/sec compressional wave) propagating in the specimen.
Abstract: The experimental evidence and the associated theory are presented for the dislocation contribution to the generation of the second harmonic of an ultrasonic wave in solids. The contribution is measured through the changes, as a function of static bias stress, in the amplitude of the second harmonic of a fundamental wave (10 Mc/sec compressional wave) propagating in the specimen.In aluminum single crystals the amplitude of the second harmonic, for a given amplitude of the fundamental, changes markedly with static bias stresses ranging from 0 to 106 dyn/cm2. In alloys, there are essentially no changes of the amplitude of the second harmonic even for bias stresses up to 107 dyn/cm2. These observations are consistent with the predicted dependence of the amplitude on dislocation loop length and on the static stress. The effects of small amounts of plastic deformation were consistent with the proposed model.
267 citations
TL;DR: In this paper, the second order harmonic of a Lamb wave propagating in a metallic plate is measured using a hybrid wedge generation and laser interferometric detection system, and the results show that the proposed procedure is able to characterize the inherent material nonlinearity of two different aluminum plates whose absolute nonlinearness parameters are known from longitudinal wave measurements.
Abstract: The objective of this research is to develop an accurate and reliable procedure to measure the second order harmonic of a Lamb wave propagating in a metallic plate. There are two associated complications in measuring these nonlinear Lamb waves, namely, their inherent dispersive and multimode natures. To overcome these, this research combines a time-frequency representation with a hybrid wedge generation and laser interferometric detection system. The effectiveness of the proposed procedure is demonstrated by characterizing the inherent material nonlinearity of two different aluminum plates whose absolute nonlinearity parameters are known from longitudinal wave measurements.
198 citations
TL;DR: In this paper, an analysis was made for the purpose of relating higher-order elastic constants to the growth of harmonics in an initially sinusoidal wave, where the face of a semi-infinite nondissipative elastic medium was considered.
Abstract: An analysis was made for the purpose of relating higher‐order elastic constants to the growth of harmonics in an initially sinusoidal wave. It is supposed that the face of a semiinfinite nondissipative elastic medium—for which the equation of one‐dimensional motion is u = (∂2u/∂x2)g(∂u/∂x)—is subjected to the sinusoidal displacement u = u0 cos(ωt−φ). The function g(∂u/∂x) is given as g(ξ) = (1/ρ0)[M2+M3ξ+M4ξ2+⋯+Miξi−2], where Mi depends on elastic constants up to and including order i. A solution, including the effects due to terms as high as M5 in the function g(ξ), is expressed as u = u0 Σn{Dn sin[n(ωt− Kx)]+En cos[n(ωt− Kx)]}+F(x), where the summation over n goes from 1 to ∞. Dn and En are expanded in powers of a Mach number M and a dimensionless distance X (M = ωu0/c0, X = ωx/c0, c02 = M2/ρ0). It is found that as u0 → 0, the limiting value of the ratio of the second‐harmonic amplitude, H2 = u0(D22+E22)12, to u0M is given by −M3X/8M2, independently of M4, M5, etc. Thus, with M2 already known, M3 can be...
99 citations