Scatter in nonlinear ultrasonic measurements due to crystallographic orientation change induced anisotropy in harmonics generation
TL;DR: In this paper, the scale of crystal orientation change is shown to have a strong correlation with the degree of scatter in nonlinear ultrasonic (NLU) measurements, which arises due to anisotropy in harmonics generation as a result of orientation change of slip systems in polycrystals with respect to the wave propagation direction.
Abstract: Present study endeavors to establish the physical basis of an unprecedented trend in scatter, observed in nonlinear ultrasonic (NLU) parameter, associated with varying degree of crystallographic orientation change across crystallites in a polycrystalline material. It is shown that this scatter arises due to anisotropy in harmonics generation as a result of orientation change of slip systems in polycrystals with respect to the wave propagation direction. A near α titanium alloy has been taken as a model alloy to demonstrate this effect of crystallographic orientation change vis-a-vis change in the orientation of slip systems. Scale of crystal orientation change is shown to have a strong correlation with the degree of scatter in NLU measurements. Further, the study establishes the dominating effect of the scale of crystalline orientation change on harmonics generation as compared to variation in other microstructural parameters such as dislocation density, interface structure etc. Frequency distribution analysis of the scatter indicates that the distribution depends on the colony size which exhibits a linear correlation with standard deviation value. The dislocation string vibration model has been extended for harmonics generation in polycrystalline aggregates to explain the trend in the scatter during measurement of NLU parameter in the material.
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TL;DR: In this article, the authors present a comprehensive review of the current state of knowledge of second harmonic generation (SHG) measurements, a subset of nonlinear ultrasonic non-destructive evaluation techniques.
Abstract: This paper presents a comprehensive review of the current state of knowledge of second harmonic generation (SHG) measurements, a subset of nonlinear ultrasonic nondestructive evaluation techniques. These SHG techniques exploit the material nonlinearity of metals in order to measure the acoustic nonlinearity parameter, $$\beta $$
. In these measurements, a second harmonic wave is generated from a propagating monochromatic elastic wave, due to the anharmonicity of the crystal lattice, as well as the presence of microstructural features such as dislocations and precipitates. This article provides a summary of models that relate the different microstructural contributions to $$\beta $$
, and provides details of the different SHG measurement and analysis techniques available, focusing on longitudinal and Rayleigh wave methods. The main focus of this paper is a critical review of the literature that utilizes these SHG methods for the nondestructive evaluation of plasticity, fatigue, thermal aging, creep, and radiation damage in metals.
271 citations
Cites background from "Scatter in nonlinear ultrasonic mea..."
...[143] correlated cooling rates with scatter in the nonlinear-...
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...100], titanium alloys [97,143], ferritic steels [49,101,144],...
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TL;DR: In this article, the effects of copper precipitates on the acoustic nonlinearity parameter of 17-4PH stainless steel were investigated using nonlinear ultrasonic measurements using Rayleigh waves, consistent with evidence of copper precipitation from hardness, thermo-electric power, transmission electron microscopy and atom probe tomography measurements.
Abstract: This research is part of a broader effort to develop a nondestructive evaluation technique to monitor radiation damage in reactor pressure vessel steels, the main contributor being copper-rich precipitates. In this work, 17-4PH stainless steel is thermally aged to study the effects of copper precipitates on the acoustic nonlinearity parameter. Nonlinear ultrasonic measurements using Rayleigh waves are performed on isothermally aged 17-4PH. Results showed a decrease in the acoustic nonlinearity parameter with increasing aging time, consistent with evidence of copper precipitation from hardness, thermo-electric power, transmission electron microscopy, and atom probe tomography measurements.
45 citations
TL;DR: In this article, the relationship between the ultrasonic attenuation and the microstructures of pure A206 and Al2O3 reinforced MMNCs with/without ultrasonic dispersion was investigated.
Abstract: A206–Al2O3 metal matrix nanocomposite (MMNC) is a promising high performance material with potential applications in various industries, such as automotive, aerospace, and defense. Al2O3 nanoparticles dispersed into molten Al using ultrasonic cavitation technique can enhance the nucleation of primary Al phase to reduce its grain size and modify the secondary intermetallic phases. To enable a scale-up production, an effective yet easy-to-implement quality inspection technique is needed to effectively evaluate the resultant microstructure of the MMNCs. At present the standard inspection technique is based on the microscopic images, which are costly and time-consuming to obtain. This paper investigates the relationship between the ultrasonic attenuation and the microstructures of pure A206 and Al2O3 reinforced MMNCs with/without ultrasonic dispersion. A hypothesis test based on an estimated attenuation variance was developed and it could accurately differentiate poor samples from good ones. This study provides useful guidelines to establish a new quality inspection technique for A206–Al2O3 nanocomposites using ultrasonic nondestructive testing method.
17 citations
Cites background from "Scatter in nonlinear ultrasonic mea..."
...[36] measured the nonlinear ultrasonic (NLU) parameters at different locations of b heat treated near a titanium alloys under different cooling rates....
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TL;DR: In this paper, the grain growth associated with isochronous annealing in polycrystalline pure copper is studied using nonlinear ultrasonic method and micro-hardness measurements as well as metallographic results are presented.
Abstract: In this work grain growth associated with isochronous annealing in polycrystalline pure copper is studied using nonlinear ultrasonic method. In isochronous annealing, holding time is constant but annealing temperatures vary. It is observed that, grain growth due to isochronous annealing significantly influences the ultrasonic nonlinearity parameter, β. A decrease in nonlinearity parameter with increase in grain size is noticed. Further, micro-hardness measurements as well as metallographic results are presented to underscore the utility of the nonlinear ultrasonic method in gauging the progress of annealing. As the time and effort involved in this method is less, with suitable calibration, this method may be gainfully employed for determination of grain size on annealing.
14 citations
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TL;DR: The microstructural changes of the fully heat treated alloy exposed at 980 °C for different hours of thermal exposure have been characterized using ultrasonic methods to non‐destructively characterize such detrimental changes in the microstructure that controls the mechanical properties and limits the life of components.
7 citations
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68 citations
TL;DR: In this article, a non-linear ultrasonic technique has been used to assess the fatigue damage in low carbon structural steel and the percentage of total harmonic distortion, which is the ratio of the amplitude of 2nd harmonic and the fundamental, has been introduced as the measurement parameter in this paper.
65 citations
TL;DR: In this article, the authors determined the nonlinear ultrasonic parameter β and the ultrasonic longitudinal phase velocity vL for a series of martensitic steel specimens which varied in carbon content.
Abstract: We have determined the nonlinear ultrasonic parameter β and the ultrasonic longitudinal phase velocity vL for a series of martensitic steel specimens which varied in carbon content. The specimens were measured in the as-quenched state to ensure that the carbon was present primarily as an interstitial in the martensite. β increased monotonically with carbon content and hardness over the range 0.10–0.40 mass % C (39.0–57.5 Rockwell C hardness). However, vL remained virtually the same for all specimens. Therefore we conclude that β is sensitive to microstructural variations between the specimens, but vL is not. X-ray diffraction experiments indicate that the dislocation density in the specimens is large (∼1011–1012/cm2) and increases with increasing carbon content. These results support the hypothesis that the observed increase in β can be attributed to dislocation-related effects in the specimens.
64 citations
TL;DR: An analytical model of the effects of the Peierls-Nabarro barrier stress on the nonlinear dynamics of dislocation motion in crystalline solids resulting from a perturbative ultrasonic wave is derived in this article.
Abstract: An analytical model of the effects of the Peierls–Nabarro barrier stress on the nonlinear dynamics of dislocation motion in crystalline solids resulting from a perturbative ultrasonic wave is derived. The nonlinearity is quantified by a material nonlinearity parameter β extracted from measurements of the amplitudes of the fundamental and harmonically generated ultrasonic waveforms. The β parameter is found to be functionally dependent on the magnitude of the Peierls–Nabarro barrier stress, the dislocation loop length, the shear modulus, and the Burgers vector of the crystal. The parameter is shown to exhibit a Bessel function oscillatory dependence on the stress amplitude of the fundamental ultrasonic wave resulting directly from the Peierls–Nabarro barrier stress. A sharp increase in the magnitude of β is shown to occur at low ultrasonic amplitudes where the dislocation motion is confined between adjacent lattice planes bounding the unperturbed dislocation. The generalization of the model to polycrystall...
44 citations
TL;DR: In this paper, a nonlinear ultrasonic (NLU) harmonic generation system was used to characterize the fatigue damage in a flat hourglass, high strength Al-Cu-Zn-Mg alloy, AA7175-T7351 specimens.
Abstract: Nonlinear ultrasonic (NLU) harmonic generation system was used to characterize the fatigue damage in a flat hour-glass, high strength Al–Cu–Zn–Mg alloy, AA7175-T7351 specimens. Experiments were carried out to introduce controlled levels of fatigue damage under constant amplitude loading to determine the NLU response using surface acoustic wave (or Rayleigh mode) at regular intervals of fatigue life. The NLU parameter (A2/A12) plotted as a function of percentage of fatigue life shows two peaks for all the samples tested, independent of the amplitude of fatigue loading. The first peak appeared between 40%–50% of fatigue life and the second peak between 80%–90% of fatigue life. Among the two flat surfaces of the specimen, a higher nonlinearity response was observed on the surface which had the first crack initiation. The appearance of two peaks in the nonlinear response during fatigue damage progression is explained based on the dislocation dynamics and dislocation-crack interaction present in the specimens ...
42 citations