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Journal ArticleDOI

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.
Citations
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Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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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Journal ArticleDOI
TL;DR: The results show that the correlation between attenuation and distribution width can be modeled with a power law, and the frequency dependence of attenuation is shown to depend strongly on the distribution width, expected to aid in the development of simplified models to quantify the grain-size distribution.

15 citations

Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: This letter provides proof that a similar bound is present for low-frequency attenuation constants of polycrystals caused by grain scattering, and an additional upper bound to the attenuation ratio is unveiled.
Abstract: A lower bound to the longitudinal and shear attenuation ratio was recently derived for viscoelastic materials [Norris, J. Acoust. Soc. Am. 141, 475-479 (2017)]. This letter provides proof that a similar bound is present for low-frequency attenuation constants of polycrystals caused by grain scattering. An additional upper bound to the attenuation ratio is unveiled. Both bounds are proven to be combinations of wave speeds. The upper and lower bounds correspond with the vanishing of the second-order anisotropy of the bulk and shear modulus, respectively. A link to the polycrystalline Poisson's ratio is highlighted, which completely bounds the attenuation ratio. An analysis of 2176 crystalline materials was conducted to further verify the bounds.

8 citations

Journal ArticleDOI
TL;DR: In this article, a comparative study between the ultrasonic attenuation and the nonlinearity is presented for the characterisation of microstructure in large dimension forgings, and results are provided for two austeni...
Abstract: A comparative study between the ultrasonic attenuation and the nonlinearity is presented for the characterisation of microstructure in large dimension forgings. Results are provided for two austeni...

8 citations

Journal ArticleDOI
TL;DR: In this paper, a multi-frequency nonlinear ultrasonic measurement is used to characterize grain size variations and distributions unambiguously, and frequency dependence of this parameter is found to be a reliable tool for rapid screening of materials where grain size varies widely.
Abstract: A multi-frequency nonlinear ultrasonic measurement is used to characterize grain size variations and distributions unambiguously. The ultrasonic nonlinearity parameter varies linearly with grain size in the Rayleigh scattering regime but deviates from linear behavior at the Rayleigh-to-stochastic transition zone. Frequency dependence of this parameter is found to be a reliable tool for rapid screening of materials where grain size varies widely.

8 citations