Effect of grain size distribution on the acoustic nonlinearity parameter
08 May 2020-Journal of Applied Physics (AIP Publishing LLCAIP Publishing)-Vol. 127, Iss: 18, pp 185102
TL;DR: In this paper, the effect of grain size distribution on the measured acoustic nonlinearity of polycrystalline engineering materials is investigated, and the results predict that the existing models that account for only the mean grain size when characterizing material degradations need to be modified more comprehensively to include the role of grain sizes distribution.
Abstract: The effect of grain size distribution on the measured acoustic nonlinearity of polycrystalline engineering materials is investigated. Results are provided for two austenitic stainless steel materials with comparable mean grain sizes and distinct distribution widths assuming equiaxed grains and random crystallographic orientation. The distribution width is shown to influence the nonlinearity parameter considerably. On the material with a wider distribution, a reduced nonlinearity was noted, and comparable trends were also noted for different frequencies investigated. The results predict that the existing models that account for only the mean grain size when characterizing material degradations need to be modified more comprehensively to include the role of grain size distribution.
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02 Jul 2021
TL;DR: In this paper, Rayleigh waves are propagated through a thick aluminum (Al) plate to evaluate its material nonlinearity based on the second harmonic produced in the response, and numerical simulations are carried out on the pristine and fatigued thick Al specimens, and an amplitude-based Rayleigh wave nonlinear parameter is used to characterize the material non-linearity.
Abstract: In the present study, Rayleigh waves are propagated through a thick Aluminum (Al) plate to evaluate its material nonlinearity based on the second harmonic produced in the response. The experiments and numerical simulations are carried out on the pristine and fatigued thick Al specimens, and an amplitude-based Rayleigh wave nonlinear parameter is used to characterize the material nonlinearity. In addition, a physics-based nonlinear parameter that depends on the sub-structural evolution parameters, and higher-order plastic and elastic constants are also used to characterize the nonlinearity of the pristine and fatigued Al material. They found to be in good agreement for the predefined conditions of tone burst cycles in the actuation signal and propagation distance. The knowledge of material nonlinearity parameters evaluated for the pristine and fatigued thick plate specimens using Rayleigh waves is shown in the present study to be crucial to evaluate the remnant useful life (RUL) of the fatigued specimen with fair accuracy.
2 citations
TL;DR: The von Kármán function is shown to be more accurate than the exponential function and more tractable than the sum of exponentials form and the impact of the SCF on wave propagation and scattering is studied.
Abstract: Analytical functions that describe the spatial heterogeneity in polycrystalline media are highly desirable. These mathematically tractable descriptors can be readily implemented in physical models of static and dynamic material behavior, including wave propagation. This paper explores the suitability of von Kármán spatial correlation functions (SCFs) to describe polycrystalline media with a distribution of grain sizes. The empirical two-point statistics are compared to the von Kármán and other commonly reported SCFs. The von Kármán function is shown to be more accurate than the exponential function and more tractable than the sum of exponentials form. The impact of the SCF on wave propagation and scattering is studied by employing a well-defined analytical model for attenuation. The attenuation varies by over a factor of two for the aluminum case considered. These results provide preliminary insights into the suitability of a closed-form von Kármán SCF to describe polycrystalline media with increasingly complex microstructures.
2 citations
TL;DR: In this paper, the attenuation coefficient of Rayleigh waves is introduced to characterize grain size in heat treated 316L stainless steel, and the measured results are efficient, more stable and less influenced by the surface state when an air-coupled receiver is used.
Abstract: Grain size is an important parameter in evaluating the properties of microstructures in metals. In this paper, the attenuation coefficient of Rayleigh waves is introduced to characterize grain size in heat treated 316L stainless steel. Rayleigh wave attenuation is measured using an angle beam wedge transducer as the transmitter and an air-coupled transducer as the receiver. The results show that the grain size in 316L stainless steel increases due to heat treatment time, the hardness decreases accordingly, and the attenuation coefficient of Rayleigh waves increases. This indicates that the Rayleigh wave attenuation is sufficient in distinguishing the changes in the properties of the heat-treated stainless steel. It is found that compared with the measurement method using an angle beam wedge receiver, the measured results are efficient, more stable and less influenced by the surface state when an air-coupled receiver is used. In addition, comparison results also show that the Rayleigh wave attenuation is more sensitive to changes in material properties than the longitudinal wave attenuation, as the wavelength of the Rayleigh wave is shorter than that of the longitudinal wave at the same frequency.
2 citations
TL;DR: In this article , an explainable nonlinearity-aware multilevel wavelet decomposition-multichannel one-dimensional convolutional neural network is proposed to hierarchically extract multi-level time-frequency features of the acoustic non-linearity and automatically model latent nonlinear dynamics directly from the nonlinear ultrasonic responses.
Abstract: Characterization of grain microstructures of metallic materials is crucial to materials science and engineering applications. Unfortunately, the universal electron microscopic methodologies can only capture two-dimensional local observations of the microstructures in a time-consuming destructive way. In this regard, the nonlinear ultrasonic technique shows the potential for efficient and nondestructive microstructure characterization due to its high sensitivity to microstructural features of materials, but is hindered by the ill-posed inverse problem for multiparameter estimation induced by the incomplete understanding of the complicated nonlinear mechanical interaction mechanism. We propose an explainable nonlinearity-aware multilevel wavelet decomposition-multichannel one-dimensional convolutional neural network to hierarchically extracts multilevel time-frequency features of the acoustic nonlinearity and automatically model latent nonlinear dynamics directly from the nonlinear ultrasonic responses. The results demonstrate that the proposed approach establishes the complex mapping between acoustic nonlinearity and microstructural features, thereby determining the lognormal distribution of grain size in metallic materials rather than only average grain size. In the meantime, the integration of the designed nonlinearity-aware network and the quantitative analysis of component importance provides an acceptable physical explainability of the deep learning approach for the nonlinear ultrasonic technique. Our study shows the promise of this technique for real-time in situ evaluation of microstructural evolution in various applications.
2 citations
References
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TL;DR: In this paper, electron backscattering diffraction (EBSD) was used to improve the characterisation of both the WC and Co phase size, and contiguity between them, and a good correlation was shown between the EBSD and optical techniques.
Abstract: Accurate measurements of grain size are required to underpin development of models to predict properties, particularly of hybrid and multiphase materials. The conventional method for WC grain size determination in WC/Co is to use linear intercept measurements from light microscope or scanning electron microscopic images, usually requiring lengthy manual measurements, and subjective interpretation of grain boundary positions according to the level of etching and change in contrast. The possibilities offered by electron backscattering diffraction (EBSD) for improving the characterisation of both the WC and Co phase size, and contiguity between them, has been investigated. Samples covering a range of grain sizes have been examined by both EBSD and conventional methods to determine mean values and size distributions, with a special emphasis on the measurement of small grains. Diameters determined by both area (to give a circle equivalent diameter) and linear intercept from EBSD data are compared with the SEM image linear intercept method. It is shown that although the EBSD method is automated, great care must be taken in data analysis to identify and handle consistently small size values. If care is taken in the data handling then a good correlation can be shown between the EBSD and optical techniques.
115 citations
TL;DR: In this paper, the nonlinear differential equation describing the propagation of a finite amplitude ultrasonic wave in a cubic crystal is shown to take the same form as that describing a fluid, and the propagation distance required for discontinuity in the particle velocity is calculated for various directions in the crystal.
Abstract: The non‐Hookeian behavior of a solid is studied using the distortion of an initially sinusoidal ultrasonic wave. The nonlinear differential equation describing the propagation of a finite amplitude ultrasonic wave in a cubic crystal is shown to take the same form as that describing a fluid. The propagation distance required for discontinuity in the particle velocity is calculated for various directions in the crystal. It is shown that in a typical experiment the path length can be appreciably less than the discontinuity distance, so that the distortion can be represented as a linear increase of second harmonic content with path length. Experimental results are given for copper single crystals which have been annealed or neutron irradiated.
113 citations
TL;DR: Techniques that utilise ultrasonic bulk waves to size flaws, including amplitude, temporal, imaging and inversion, are reviewed.
112 citations
TL;DR: In this article, a nonlinear domain (second harmonic amplitude) was used to evaluate the second harmonic amplitude (SHA) of a titanium alloy for in-service evaluation of creep damage.
93 citations
TL;DR: In this article, nonlinear ultrasound was used to monitor radiation damage in two reactor pressure vessel (RPV) steels, and the results showed a clear increase in the measured acoustic nonlinearity from the unirradiated state to the medium dose, and then a decrease from medium dose to high dose.
Abstract: Nonlinear ultrasound was used to monitor radiation damage in two reactor pressure vessel (RPV) steels. The microstructural changes associated with radiation damage include changes in dislocation density and the formation of precipitates, and nonlinear ultrasonic waves are known to be sensitive to such changes. Six samples each of two different RPV steels were previously irradiated in the Rheinsberg power reactor to two fluence levels, up to 1020 n/cm2 (E > 1 MeV). Longitudinal waves were used to measure the acoustic nonlinearity in these samples, and the results show a clear increase in the measured acoustic nonlinearity from the unirradiated state to the medium dose, and then a decrease from medium dose to high dose.
90 citations