المؤلفون: Zhao, Wusheng¹ (AUTHOR) wszhao@whrsm.ac.cn, Qin, Changkun² (AUTHOR) 1280183931@qq.com, Chen, Weizhong³ (AUTHOR) wzchen@whrsm.ac.cn, Tan, Xianjun³ (AUTHOR) xjtan@whrsm.ac.cn

المصدر: International Journal of Geomechanics. Dec2023, Vol. 23 Issue 12, p1-12. 12p.

مصطلحات موضوعية: *ELASTIC wave propagation, *MODEL airplanes, *STRESS waves, *ELASTIC waves, *SEISMIC waves, *ADHESIVES, *THEORY of wave motion

مستخلص: Wave propagation in a layered rock mass is a common problem in geotechnical engineering. The bedding planes in a layered rock mass are generally in situ stressed and adhesively bonded. This study extended the time-domain recursive method to analyze the wave propagation in a layered rock mass with adhesive bedding planes. The maximum stress criterion was used to indicate the adhesive failure of bedding planes. The Bandis–Barton and Coulomb slip models were used to characterize the normal and tangential behaviors of bedding planes after the adhesive bond fails. Based on the backward differentiation formula, an analytical solution reflecting four possible states of the bedding plane and the in situ stresses in rock mass was established. Subsequently, the solution was verified for various conditions. Besides, parametric studies were carried out to assess the influences of adhesive properties of bedding planes and in situ stresses on wave transmission. The transmission coefficient of seismic waves increases linearly as the adhesive strength of the bedding plane increases. The in situ normal stress could facilitate wave transmission across the bedding plane, while the in situ shear stress causes the direction-dependency of transmitted waves. Furthermore, the impacts of bedding plane adhesion and in situ stresses on wave propagation were influenced by the amplitude, frequency, and impinging angle of incident waves. The welded model that ignores the adhesion failure of the bedding plane and the unbonded models that neglect the interface adhesion could overestimate or underestimate the transmitted wave across a bedding plane. [ABSTRACT FROM AUTHOR]

المؤلفون: Kamel, Omar A.¹ (AUTHOR) oalaaeldein@mun.ca, Abouhussien, Ahmed A.² (AUTHOR) aabouhussien@mun.ca, Hassan, Assem A. A.³ (AUTHOR) ahassan@un.ca, AbdelAleem, Basem H.⁴ (AUTHOR) b.abdelaleem@mun.ca

المصدر: Journal of Materials in Civil Engineering. Nov2023, Vol. 35 Issue 11, p1-11. 11p.

مصطلحات موضوعية: *ACOUSTIC emission, *ACOUSTIC wave propagation, *RUBBER powders, *COLD (Temperature), *CRUMB rubber, *CONCRETE testing, *RUBBER

مستخلص: This study investigates the change in the acoustic emission (AE) parameters emitted in rubberized concrete under abrasion action at a sub-freezing temperature (−20°C). Seven concrete mixtures were developed with two coarse-to-fine aggregate ratios (C/F) (2.0 and 0.7), various crumb rubber (CR) content (0%, 10%, 20%, and 30%), and different rubber particle sizes [4.5 mm CR and 0.4 mm powder rubber (PR)]. Rotating cutter tests were conducted on three 100 mm cubic samples from each mixture at −20°C and 25°C while monitored via an AE system. AE parameters such as amplitude, number of hits, and signal strength were collected and underwent two parameter-based analyses: b -value and intensity analysis approaches, resulting in three additional parameters: b -value, severity (Sr), and the historic index [ H(t) ]. Results showed that testing concrete samples under abrasion at cold temperature, −20°C , resulted in a decrease in the emitted number of hits, cumulative signal strength (CSS), Sr , H(t) , and an increase in b -values compared to testing at 25°C. Furthermore, incorporating rubber particles was found to decrease the AE signals' amplitudes significantly at 25°C and slightly at −20°C , which manifested the higher wave attenuation occurrence at ambient temperature compared to cold temperature. AE analysis also showed a decrease in the abrasion resistance for mixtures with higher C/F, higher CR content, and larger rubber particle size. These decreases were more noticeable at 25°C compared to −20°C. Finally, the study developed two damage classification charts to estimate the ranges of abrasion mass loss percentage and wear depth in terms of the intensity analysis parameters: Sr and H(t). [ABSTRACT FROM AUTHOR]

المؤلفون: Saini, Poonam¹ (AUTHOR) poonam.kkr@gmail.com

المصدر: Journal of Engineering Mechanics. Jun2023, Vol. 149 Issue 6, p1-12. 12p.

مصطلحات موضوعية: *ELASTIC wave propagation, *PARTICLE size determination, *SPECTRAL element method, *ELASTIC analysis (Engineering), *RAYLEIGH quotient, *THEORY of wave motion, *GROUP velocity

مستخلص: The accuracy of the optimally blended spectral-element method for wave propagation in a homogeneous transversely isotropic elastic medium was investigated. A nonstandard quadrature rule obtained by combining Gauss quadrature rule and Gauss–Lobatto–Legendre quadrature rule was used to compute elementary matrixes. The mass and stiffness matrixes were represented as the triple tensor-product of elementary matrixes as second-order tensors. The solution of the eigenvalue problem representing the semidiscretized version of elastic wave equation for plane harmonic wave propagation was obtained using the Rayleigh quotient approximation technique. The resulting eigenvalues subsequently were used to estimate the phase and group velocity of three bulk waves. The variations of the errors in these velocities of the bulk waves with the number of grid points per wavelength were depicted graphically. These variations were shown for different polynomial orders and various angles of deviation from the symmetry axis. The effect of a change in the order of time discretization on error variation also was shown. The solution obtained by the optimally blended spectral-element method was found to be more accurate than that from the classical spectral-element method for low-order polynomials. The improvement in solution accuracy was demonstrated through dispersion analysis. [ABSTRACT FROM AUTHOR]

المؤلفون: Thiyagarajan, Jothi Saravanan

المصدر: Journal of Engineering Mechanics; Sep2022, Vol. 148 Issue 9, p1-19, 19p

مصطلحات موضوعية: WIRE, STRAINS & stresses (Mechanics), PRESTRESSED concrete beams, DEGREES of freedom, CURVILINEAR coordinates, ASYMPTOTIC expansions, FINITE element method, ELASTIC wave propagation

مستخلص: Studying ultrasonic guided wave modes in multiple steel wires helps extend and apply wave dynamics theory to practical engineering. This research focused on elastic wave propagation for investigating dispersion behavior in a helical waveguide under the prestressed state. For the guided wave theory of one-dimensional propagation, the physical system represented as a curve must satisfy translation invariance. Elastic wave propagation in a helical waveguide was analyzed using the semianalytical finite element (SAFE) method. The scaled Frenet–Serret and twisted basis dispersion curves were analyzed for comparison. The bases were used to define covariant and contravariant bases where the strain and stress tensors were expressed. Then, by proving the translational invariance of the system in the curvilinear coordinates, a Fourier transform of the displacement was deployed to distinguish plane waves based on their wavenumber and reduce the study of the waveguide according to its cross-section. Later, the SAFE method derived from the twisted cylindrical coordinate system was compared with the standard axisymmetric SAFE method. Analysis of an outer steel wire of the seven-wire helical strand was carried out for undamped and damped cases with initial prestress conditions to investigate the dispersion behavior of the helical waveguide. Static analysis of the entire seven-wire helical strand was carried out by considering an initial prestress field, and a finite-element method based on asymptotic expansion theory was used to solve contact stress field calculation. Correspondingly, the proposed method was verified with the classical Machida and Costello calculation theories for calculating the stress field on its respective axial cross-section for each wire. A very complex band diagram needs to be investigated while performing a dynamic analysis of the helical waveguide. The current work introduces the modal filters via the so-called coupling conditions to parse the complex dispersion characteristics. When the SAFE method is used to analyze its dynamic wave properties, the employed coupling condition reduces the degrees of freedom of the system and improves calculation efficiency. Henceforth, the proposed methodology for calculating the prestressed state is the potential health monitoring scheme for a helical multiwire. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Engineering Mechanics is the property of American Society of Civil Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Saini, Poonam

المصدر: Journal of Engineering Mechanics; Jul2022, Vol. 148 Issue 7, p1-12, 12p

مصطلحات موضوعية: ELASTIC waves, SPECTRAL element method, NUMERICAL functions, RAYLEIGH quotient, ELASTIC wave propagation, TENSOR products

مستخلص: Dispersion is studied for the two-dimensional propagation of elastic waves in transversely isotropic media using the Lagrange spectral element method. Spectral element matrices are derived as the tensor product of elementary second-order tensors. Gauss-Lobatto-Legendre points are used for the interpolation of Lagrange-type shape functions as well as for the numerical integration to obtain elementary matrices. The Rayleigh quotient approximation technique is employed to find the solution of the eigenvalue problem, which is obtained from the semidiscretized form of the elastic wave equation for propagation of plane harmonic waves. Variations of errors in the phase/group velocities of bulk waves are depicted graphically with the order of interpolation polynomial, angle with the symmetry axis, and the time discretization. Error analysis clearly demonstrated the effectiveness of the Lagrange spectral element method for wave simulation in a transversely isotropic medium. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Engineering Mechanics is the property of American Society of Civil Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: De, Subhayan, Ebna Hai, Bhuiyan Shameem Mahmood, Doostan, Alireza, Bause, Markus

المصدر: Journal of Engineering Mechanics; Mar2022, Vol. 148 Issue 3, p1-18, 18p

مصطلحات موضوعية: ULTRASONIC propagation, MACHINE learning, STRUCTURAL health monitoring, CONVOLUTIONAL neural networks, KRIGING, ACOUSTIC wave propagation

مستخلص: Structural health monitoring (SHM) systems use nondestructive testing principles for damage identification. As part of SHM, the propagation of ultrasonic guided waves (UGW) is tracked and analyzed for the changes in the associated wave pattern. These changes help identify the location of a structural damage, if any. We advance the existing research by accounting for uncertainty in the material and geometric properties of a structure. The physics model employed in this study comprises a monolithically coupled system of elastic and acoustic wave equations, known as the wave propagation in fluid–structure and their interface (WpFSI) problem. Because the numerical simulation of the WpFSI problem becomes computationally extremely expensive for many realizations of the uncertainty, we developed an efficient algorithm in this work that employs machine learning techniques like Gaussian process regression and convolutional neural networks to predict UGW propagation in a fluid–structure and their interface under uncertainty. First, a small set of training images for different realizations of the uncertain parameters of the inclusion inside the structure is generated using the computationally costly physics model. Next, Gaussian processes trained with these images are used for predicting the propagated wave with convolutional neural networks for further enhancement to produce high-quality images of the wave patterns for new realizations of the uncertainty. The results indicate that the proposed approach provides an accurate prediction for the WpFSI problem in the presence of uncertainty. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Engineering Mechanics is the property of American Society of Civil Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Wang, Jinchao, Xu, Hanhua, Chen, Wei, Wang, Chuanying, Han, Zengqiang

المصدر: International Journal of Geomechanics; Jan2022, Vol. 22 Issue 1, p1-13, 13p

مصطلحات موضوعية: EVALUATION methodology, SPEED of sound, DIGITAL images, ACOUSTIC wave propagation, ENGINEERING mathematics

مستخلص: Given the single and one-sided problems of traditional rock mass structure integrity evaluation methods, this paper will use borehole test data that were obtained by conventional logging methods to extract the key geological data that will be used for integrity evaluation from digital images and digital signals. Based on a comprehensive method of multivariate data analysis, an evaluation method for rock mass structure integrity will be established, which reflects the differences in rock mass structure, rock mass fragmentation, and rock acoustic response. The rock mass combination function [C(h)], rock mass fragmentation function [F(h)], and sound velocity function of a rock mass [U(h)] will be constructed, which could realize the quantitative description of rock mass integrity multiple parameters. Then, the rock mass combination degree, rock mass fragmentation, and rock mass propagation sound velocity parameters will be classified using fuzzy mathematics, and the rock mass structure integrity evaluation index [Mc(h)] based on multivariate data will be constructed. Finally, the method will be combined with practical engineering for verification and analysis. Compared with the traditional evaluation method, the method in this paper considers more factors that affect the stability of rock mass, which combine the degree of rock mass combination, rock mass fragmentation, and rock mass sound velocity. The method in this paper will realize the integrity evaluation of a borehole rock mass structure from different dimensions. Compared with the traditional method, the integrity evaluation results will consider more comprehensive factors. [ABSTRACT FROM AUTHOR]

: Copyright of International Journal of Geomechanics is the property of American Society of Civil Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المصدر: International Journal of Geomechanics. Aug2014, Vol. 14 Issue 4, p-1. 10p.

مصطلحات موضوعية: *ELASTIC wave propagation, *SHEAR waves, *SURFACE cracks, *FIBER-reinforced concrete, *PARAMETER estimation, *COMPARATIVE studies, *STRAINS & stresses (Mechanics)

مستخلص: This paper investigates the effect of reinforcement and nonhomogeneity on the propagation of cracks caused by horizontally polarized shear waves in a heterogeneous fiber-reinforced medium. The effects of reinforcement and heterogeneity on the propagation of the crack are highlighted in this study. The stress intensity factor at the crack tip for a concentrated force of a constant intensity has been calculated and depicted by means of graphs for various cases. It is observed that fiber reinforcement and heterogeneity parameters decrease the stress intensity factor. Remarkably, the stress intensity factor decreases with the increase in the length and speed of the crack. Also, a comparative study was made for the stress intensity factor in reinforced medium over reinforced-free medium and heterogeneous medium over the homogeneous medium. Moreover, some important peculiarities were observed in graphs. [ABSTRACT FROM AUTHOR]

المؤلفون: Dai, Sheng, Wuttke, Frank¹, Santamarina, J. Carlos²

المصدر: Journal of Geotechnical & Geoenvironmental Engineering. Sep2013, Vol. 139 Issue 9, p1504-1511. 8p. 2 Diagrams, 6 Graphs.

مصطلحات موضوعية: *ELASTIC wave propagation, *SOIL mechanics, *STIFFNESS (Mechanics), *SCATTERING (Physics), *INTERFEROMETRY

مستخلص: Small-strain elastic wave propagation is a constant-fabric phenomenon ideally suited to monitor processes in soils. However, the determination of very small changes in travel time limits our ability to resolve changes in soil stiffness caused by internal processes or changes in boundary conditions. The first-arrival reflects the fastest path between the source and receiver of the propagating wave field; later arrivals in the coda correspond to longer paths after multiple boundary reflections and internal scattering. Therefore, time shifts between the codas of two consecutive signals are longer and easier to detect than between the signals' first arrivals. Slight changes in coda waves can be determined by cross-correlating time windows, time-stretched signals, or frequency-stretched spectra. Basic coda analysis assumes a homogeneous velocity change throughout the medium, propagation modes (P, S) that are equally affected by the process and the preservation of ratio during the process. The resolving power of coda wave interferometry is explored in an experimental study conducted with quartzitic sand subjected to loading, creep, and unloading stages. The results reveal that coda wave analysis can be used to detect changes in wave velocity on the order of (this corresponds to a stress change smaller than in uncemented soils). Such a high velocity resolution permits the study of creep, aging, and diagenetic processes even in relatively short duration tests. [ABSTRACT FROM AUTHOR]

المؤلفون: Dong, Z, Quan, W, Ma, X, Cao, L, Zhang, H, Leng, Z

المساهمون: Department of Civil and Environmental Engineering

مصطلحات موضوعية: Asphalt pavement, Dynamic responses, Impact load, Transversely isotropic, Wave propagation approach

الوصف: 202303 bcfc ; Accepted Manuscript ; Others ; National Key R&D Program of China; National Natural Science Foundation of China; Province in Heilongjiang Outstanding Youth Science Fund ; Published ; Green (AAM)

العلاقة: http://hdl.handle.net/10397/97998Test; 147; 2-s2.0-85105289594; 4021021; CEE-0187

الإتاحة: https://doi.org/10.1061/JPEODX.0000271Test
http://hdl.handle.net/10397/97998Test