Search

• Velocity profile of Circumferential SH waves in concentric cylinders have been investigated. • Cylinders are composed of self-fibre-reinforced, and piezo-magnetic-electric materials. • Phase velocity of ESMO case is found to have higher or equal magnitude compared to EOMS case. • Mechanical imperfect interface parameter has highest impact on the phase velocity. • Initial stress and radii of the cylinder bears a significant impact in altering the velocity of the wave. The present study fundamentally focuses on analyzing the limitations and transference of circumferential shear horizontal (CSH) waves in a four-layered compounded cylinder. The geometrical structure consists of cylinders of infinite length composed of self-reinforced (SR), fibre-reinforced (FR), piezo-magnetic (PM), and piezo-electric(PE) materials. In order to make the structure sensitive to the application pertaining to sensors and actuators, the PM and PE cylinders have been categorically placed in the outer part of the geometry. Whereas in order to provide stiffness and stability to the structure, the inner part consists of SR and FR materials. The common boundary between each of the cylinders has been essentially considered as imperfectly bounded. At the interface of PE and PM media, mechanical, electrical, magnetic, and inter-coupled types of imperfections have been exhibited. The closed-form of dispersion relation has been deduced for two contrast cases i.e. electrically open magnetically short (EOMS) and electrically short and magnetically open (ESMO) circuit conditions. Dispersion curves have been plotted to illustrate the salient features of parameters like normalized imperfect interface parameters, initial stresses, and radii of the concentric cylinders. The comparative effect of each one of these parameters on the phase velocity of the wave has been enlisted and marked individually. Every graph has been presented with two successive modes for a comprehensive understanding. This theoretical study may be implemented to improvise the performance of surface acoustic wave (SAW) sensors, actuators, and Piezo-cables in the form of Piezo-polymer sensors consisting of piezo-electric quartz, piezo-composite concentric cylinders, and coaxial piezo-cables. [ABSTRACT FROM AUTHOR]

• Mode-coupling vibrations in PTF resonators with initial stress are first studied. • The robustness of mode-coupling behaviors to initial stress is revealed. • The out-of-plane initial stress can tune resonance frequency of PTF resonators. • The CSF is defined to judge the coupling intensity of all modes in frequency spectra. Mode-coupling vibrations in thickness-extensional piezoelectric thin-film bulk acoustic wave resonators (FBARs) with initial stress operating in the ultra-high frequency (UHF) range are investigated by employing the Frequency Spectrum Quantitative Prediction (FSQP) method. The uniaxial uniform initial stresses along the in-plane and thickness directions are separately considered. The dispersion relation of the bulk wave in the FBAR with initial stress is obtained and then the solutions of physical fields are constructed by superimposing the eigen-modes in the dispersion curve. The variational formulation considering the initial stress is derived through the perturbation method. Then frequency spectra that predict the coupling strength between the thickness-extensional mode and other eigen-modes are obtained by substituting the solutions into the variational formulation. Mode shapes of mechanical displacements are presented to illustrate the influence of initial stress on mode-coupling behaviors in FBARs. The results show that the initial stress could cause the shifts of frequency spectrum curves, reflecting that the in-plane initial stress leads to the shifts of spectrum curves along the lateral aspect ratio axis, while the out-of-plane initial stress leads to the shifts along the frequency axis (i.e., frequency shifts) and lateral aspect ratio axis simultaneously. Desirable structural parameters should be chosen based on frequency spectra to avoid the increases of mode-coupling strength induced by initial stress. The out-of-plane initial stress could be used to tune the resonance frequency of the FBARs without changing the mode-coupling behaviors. The coupling strength factor is first defined for the convenient and fast judgment of mode-coupling intensity of all data points in the frequency spectra. The obtained results provide a crucial reference to the manipulation of resonance frequency and the mode-coupling strength in FBAR devices. [ABSTRACT FROM AUTHOR]

The effects of small length scale on the torsional surface waves propagating in a pre-stressed dissipative nanoplate were examined in this paper. Biot's incremental deformation principle as well as nonlocal elasticity theory were implemented to form the governing and frequency equations of torsional surface waves in nanoplate under considered conditions. In this work, we proposed a new approach to determine the phase velocity of torsional disturbances. Different categories are used to investigate the dispersion relations such as: wave number, scale coefficient, initial stress parameter, and dissipation coefficient. The results show that small length scale influences causes torsional dispersion of the wave propagation, which disappear in local elasticity theory. In addition, it is recognized that the torsional surface waves propagating in the pre-stressed dissipative nanoplates can be differentiated in a clear manner from those propagated in the absence of small length scale effects. The initial stress parameter can also be utilized to change the characteristics of the torsional surface wave's phase velocity in nanoplates. It is also observed that, the dissipation has a great effect on the phase velocity of torsional surface waves in propagating in the nanoplate. Therefore, this research is theoretically useful to convey information on nonlocal and dissipation properties of the nanomaterials: for example, through a precise measurement of the phase velocity of torsional surface wave propagates in a nanocomposite material by presence of the medium's dissipation. This work could be useful in understanding the way of designing the Nano devices and Nano resonators. [ABSTRACT FROM AUTHOR]

Microwave-assisted rock fragmentation is a clean, safe, and economically viable method in deep energy development. The innovation of this study lies in the first investigation of rock breaking under initial stress using microwave-assisted tunnel boring machines (TBM) cutters. To overcome the problem of inaccurate monitoring of crack information in laboratory tests, a new concept was adopted to simulate the failure process of microwave-irradiated sandstone caused by a TBM cutter. The microscopic parameters of the model were calibrated based on the laboratory test results. The results showed that an increase in the microwave power led to an increase in the damage level of the sandstone. The dominant failure modes at a low initial stress were vertical and diagonal cracks. At a high initial stress, the failure modes were a combination of vertical, diagonal, and subhorizontal cracks. The critical range of the initial stress to inhibit crack expansion was 10–20 MPa. The rock-breaking efficiency was negatively correlated with initial stress and positively correlated with microwave power. The assisted rock-breaking effect of microwave power was evident at 30 MPa. These results serve as a guide for selecting the appropriate microwave power for rock-breaking under initial stresses. • Dominant failure modes under low initial stress are vertical and diagonal cracks. • Rock-breaking efficiency is negatively correlated with initial stress. • High microwave power is more effective in assisting rock breaking at 30 MPa. • Rock-breaking efficiency has a positive correlation with microwave power. • An empirical formula for predicting rock-breaking efficiency is proposed. [ABSTRACT FROM AUTHOR]

• Rock cracking in tunnel contour blast under initial stress is experimentally tested. • Effects of stress magnitude and dimension on perimeter excavation are investigated. • The fractal characteristics of cracks in tunnel perimeter blasting are examined. • Tunnel contour blasting under initial stress is 3D numerically modelled. • Smooth blasting performs better than presplitting in tunnel contour excavation. In tunnel contour blasting, the rock fracturing is generally subjected to in-situ stress. In this investigation, the rock cracking and damage in tunnel contour blasting (smooth blasting and presplitting) under various initial stresses are experimentally and numerically studied. Eight model tests are conducted on tunnel contour blasting with 400 × 400 × 50 mm granite plates. High-speed digital image correlation is employed to identify blast-induced rock fracturing, and image-processing with ImageJ is used to analyse the detailed fracture pattern and rock fragmentation. The variations in fracture networks, fragment size, fractal dimension of rock cracks and fractal damage to rock are thereby examined with increasing stress magnitude and stress dimension. Subsequently, the stress evolution and rock fracturing in model tests are simulated in LS-DYNA, and the energy dissipation during tunnel perimeter blasting is analysed. The investigation results demonstrate that initial stress results in the reduction of length and number of rock cracks under tunnel contour blasting, leading to smaller fractal dimension of crack pattern, less damage into rock and coarser rock fragmentation. Tunnel perimeter excavation performs well under low biaxial stress but tends to fail as the biaxial stress continually increases. Under uniaxial stress, smooth excavation peripheries can be achieved when the centreline of adjacent perimeter holes is parallel to the stress direction, while perimeter excavation is unsatisfactory when the connection line of adjoining boreholes is perpendicular to the initial stress. Comparing smooth blasting with presplitting, it is found that more explosion energy is consumed in rock fracturing during smooth blasting, especially in the excavation zone, leading to a better control of rock fracture and damage in tunnel contour excavation. Therefore, smooth blasting is preferentially recommended for deep tunnelling. Additionally, small burden is also recommended for deep tunnelling with smooth blasting to avoid potential oversize fragmentation in the excavation zone. [ABSTRACT FROM AUTHOR]

The semiconductor elastic medium in the context of the photothermal theory under the influence of rotation field is studied. A novel model of the governing equations is investigated due to the refined multi-phase-lags with the thermal relaxation times of the heat equation with the hydrostatic initial stress during transport process of the photothermal phenomenon. The interaction between the multi-waves of elastic-thermal-plasma is obtained. The normal mode method in the two dimensions is applied to obtain the exact solutions of the basic physical quantities under investigation. Plasma, thermal and mechanical loads have been applied on the free surface of the semi-infinite semiconductor elastic medium to get the complete solutions of the basic physical fields. Some comparisons are shown graphically and they are discussed as a function of thermal memories with the variation of some parameters. Silicon (Si) material is used to make the numerical simulation and to display the sensitivity to the variation of the rotation parameter. [ABSTRACT FROM AUTHOR]

• The effects of the initial stresses on the tunable propagation behavior in nonlinear phononic crystal and elastic wave metamaterial are presented. • The influences of the initial stresses on both in-plane and anti-plane modes are discussed. • The initial stresses can result in the movement to the low frequency regions of the central frequencies of the band gaps and the nonreciprocal zones. In this investigation, the nonreciprocal transmission of elastic waves is achieved by the combination of asymmetric structure and nonlinear material. Our attention is focused on the effects of the initial stresses on the tunable propagation behavior in nonlinear phononic crystal and elastic wave metamaterial. Different components of the initial stresses are considered for both in-plane and anti-plane modes. Based on the Bloch's law and transfer/stiffness matrix method, the corresponding band structures and transmission coefficients of the generated fundamental and second harmonic waves are calculated and discussed. We find that the central frequencies of the band gaps and the nonreciprocal zones shift towards the low frequency regions as the initial stresses increase. This present work can be expected to provide a way to tune the transmission behaviors in nonlinear elastic wave metamaterial and mechanical diodes. [ABSTRACT FROM AUTHOR]

• Damage of specimens are investigated by blasting tests with different coupling mediums. • The potential ability of STFs to adjust rock fracture is tested. • The effect of pre-stress on crack extension is studied using fractal theory. The performance of rock blasting is significantly influenced by the coupling medium between the explosive and borehole wall. In this study, two shear-thickening fluids (corn starch suspension (CSS) and silica dioxide suspension (SDS)) and water, were used as coupling mediums. The blasting tests were conducted on cement mortar specimens under coupled blasting load and uniaxial static stresses ranging from 0 to 7.5 MPa at intervals of 2.5 MPa. Fractal theory was employed to analyze the extent of damage, crack extension and fractal characteristics of the 3D reconstructed specimens after blasting. The experimental findings revealed that specimens using SDS showed a decrease in damage followed by an increase with increasing static stress, presenting an opposite trend compared to specimens using CSS. The specimens using water exhibited intermediate results. Furthermore, numerical simulations were performed to understand the stress transmission from explosive transferring coupling medium to rock under blasting loads. The variable viscous characteristics of the coupling medium led to divergence in blast load propagation and decay, directly influencing the damage to the specimen. Under blasting load, CSS with a stronger shear-thickening effect played a beneficial buffering role, reducing the strength of the blasting load and minimizing specimen damage. On the other hand, SDS with a weaker shear-thickening effect demonstrated better stress wave propagation ability compared to water. This was reflected in the higher maximum pressure exerted by SDS, as well as the more uniform distribution of pressure, maximum shear stress, and resultant velocity along the borehole wall. The study also highlighted the potential for adjusting blast stress wave distribution by changing the detonation point's location and emphasized the advantages of CSS and SDS as stemming materials in boreholes. [ABSTRACT FROM AUTHOR]

Highlights • A strain energy function for initially stressed Mooney-Rivlin materials is derived. • The strain energy functions for initially stressed Mooney and Neo-hookean materials are given explicitly. • Our constitutive model does not require the a priori knowledge of a virtual stress-free configuration. • The derived strain energy functions can be used to design non-destructive methods to measure the initial stresses. Abstract Initial stresses originate in soft materials by the occurrence of misfits in the undeformed microstructure. Since the reference configuration is not stress-free, the effects of initial stresses on the hyperelastic behavior must be constitutively addressed. Notably, the free energy of an initially stressed material may not possess the same symmetry group as the one of the same material deforming from a naturally unstressed configuration. This work assumes that the hyperelastic strain energy density is characterized only by the deformation gradient and the initial stress tensor, using an explicit functional dependence on their independent invariants. In particular, we consider a subclass of constitutive behaviors in which the material constants do not depend on the choice of the reference configuration. Within this theoretical framework, a constitutive equation is derived for an initially stressed body that naturally behaves as an incompressible Mooney-Rivlin material. The strain energy densities for initially stressed neo-Hookean and Mooney materials are derived as special sub-cases. By assuming the existence of a virtual state that is naturally stress-free, the resulting strain energy functions are proved to fulfill the required frame-independence constraints for this special class of constitutive models. In the case of plane strain, great simplifications arise in the expression of the constitutive relations. Finally, the resulting constitutive relations prove useful guidelines for designing non-destructive methods for the quantification of the underlying initial stresses in naturally isotropic materials. [ABSTRACT FROM AUTHOR]

The present article deals with Rayleigh surface wave propagation in homogeneous magneto-thermoelastic orthotropic medium. Effect of initial stress and magnetic field on Rayleigh waves is studied in the context of three-phase-lag model of generalized thermoelasticity. The normal mode analysis is used to obtain the exact expressions for the displacement components, stresses and temperature distribution. Various frequency equations are derived and compared with the existing literature. The path of surface particles is elliptical during Rayleigh wave propagation. Effect of phase-lags on Rayleigh wave velocity, attenuation coefficient and specific loss are presented graphically. It is observed from graphical presentation that the effect of magnetic field and initial stress on different wave characteristics is pronounced. [ABSTRACT FROM AUTHOR]

Shot peening is the most common surface treatment employed to enhance the fatigue performance of structural metallic materials and often carried out after other surface treatments. This paper mainly focuses on the effects of initial conditions of surface such as initial stress filed and hardness profile on shot peening residual stress field. The residual stress distribution induced by shot peening is obtained using Hertzian contact theory and elastic–plastic evaluation after yielding occurred during impingement and rebound of shots. Elastic plastic calculations are performed using different hardening models considering Bauschinger effect. The present model is able to predict redistribution of residual stresses in shot peening process by considering the initial conditions of target surface. Initial stress distribution and yield stress variation produced by previous surface treatments are taken into account by measuring residual stresses and hardness profile at near surface layers. An analytical parametric study is performed to evaluate the influence of initial conditions induced by surface pretreatments on shot peening residual stress field. The results of analytical model are validated by experimental data obtained in the literature as well as by our own measurements. The analytical results generally agree with the experimental measurements. [ABSTRACT FROM AUTHOR]

The present manuscript studies the effect of the initial stress in micropolar magneto-thermoelasticity with microtemperatures heated by a laser pulse. The modified Ohm’s law illustrates the temperature gradient and the charge density effects in the governing equations of the studied problem. The used analytical method was the normal modes. The physical quantities are established numerically and represented graphically. [ABSTRACT FROM AUTHOR]

This paper is focused on the initial stress affected wave dispersion in mounted graphene. To capture the size-dependent and shear deformation effects, the second-order shear deformation theory (SSDT) and nonlocal strain gradient elasticity theory are used to model the graphene. A size-dependent shear deformation plate model is established on the basis of the orthotropic constitutive equations, the nonlocal strain gradient theory as well as the SSDT. Analytical solutions are developed for the wave frequency and phase velocity. The influences of small-scale parameters, initial stress and elastic medium on wave propagation behaviors of the graphene sheets are explored. It is found that the developed model reasonably interprets the softening effects of flexural frequencies and phase velocities. Unlike the classical (scaling-free) model, the developed size-dependent model shows a reasonably good agreement with the experimental frequencies and phase velocities. The wave frequencies and phase velocities of single layer graphene sheets (SLGS) will decrease with increasing compression load, and can increase by increasing tension load. The developed size-dependent 2D continuum model is hopeful to provide a possible theoretical approach to explore the wave behaviors of Graphene-like 2D materials. [ABSTRACT FROM AUTHOR]

The current study deals with forced vibration analysis of a pre-stressed piezoelectric plate with finite lengths resting on a rigid foundation, exposed to an inclined time-harmonic force. The present investigation is modeled according to a new theoretical consideration in the context of the three-dimensional linearized theory of elasticity for solids under initial stress (TLTESIS). It is assumed that the plate exhibits a polarization effect in both vertical and horizontal directions to the top surface and there is an exact clamping condition at the interface between the plate and the rigid foundation, that is, no jumping in the quantities. For obtaining the governing and boundary condition equations of our problem, the virtual work principle is used according to Hamilton's principle and the piecewise homogeneous body model. The three-dimensional displacement-based finite element model is developed for solving the system of partial differential equations and analyzing the dynamic behavior of the plate. The reliability of the solution procedure is proved by convergence analysis and comparing the results to the current literature. The target of the paper for surveying the numerical results and findings is divided into two sections. The first one presents the influence of the inclination of the dynamic external force on the forced vibration characteristics of the current model. In the second one, the influence of inclination angle, thickness ratio, aspect ratio, and initial stress parameter on the frequency response of the harmonic force are investigated in detail. As a desirable result for the designer, while a decrease in the angle of the force with the vertical axis exceeds the resonant mode of the stress, increasing values of the initial stress prevents that mode. [ABSTRACT FROM AUTHOR]

• Legendre Orthogonal Polynomial Expansion (LOPE) method mapping the relationship between the wave velocity and initial stresses was developed to generate the input characteristics of linear and non-linear variation for deep neural network. • A Deep Neural Network (DNN) was combined with LOPE for the inverse of initial stress based on Lamb wave dispersion date rather than objective function obtained from wave equations. • The performances of ReLU activation function and Sigmoid activation function were illustrated in detail for current inverse work. The prediction of the initial stress in composites is essential for the non-destructive testing (NDT) and structural health monitoring (SHM) of carbon fibre reinforced polymer (CFRP). This paper examines the potential of Lamb waves in the inverse of initial stress by calculating the influence of initial stress on the dispersion characteristics of Lamb waves propagating in multilayered CFRP laminates. By introducing the mechanics of incremental deformation into the linear three-dimensional elasticity theory, the Legendre orthogonal polynomial expansion (LOPE) method is used to mathematically model the Lamb wave propagating in multilayered CFRP laminates subjected to horizontal and vertical homogeneous initial stresses. Then, a three-hidden-layers Feed Forward Deep Neural Network (DNN) with Back Propagation (BP) algorithm is constructed to invert the magnitude and direction of the initial stresses. The input features are the phase velocities of fundamental Lamb wave A 0 mode at five different frequencies. Both training and testing samples are obtained by LOPE forward calculation. An ablation experiment is presented to compare the two different activation functions. Finally, the accuracy of the inverse is verified by comparing with the available outcomes of LOPE forward calculation. [ABSTRACT FROM AUTHOR]

This article studies a mode-I crack embedded in a material with microstructure and initial stress. The couple stress theory is adopted to analyze the mechanical behavior of a prestressed cracked medium. The governing equations and associated boundary conditions are derived. By using the Fourier transform, the mixed boundary-value problem associated with a mode-I crack is converted to two integral equations with weakly-singular and hypersingular kernels. The two integral equations are numerically solved by expanding the solution as a Chebyshev series. The convergence of the numerical solution is confirmed. The present results are capable of capturing the size-dependent behaviors through the characteristic length l. Introduction of l decreases the opening displacement and energy release rate. A tensile initial stress retards the crack to advance and vice versa. When the characteristic length and initial stress vanish, all the results reduce to the classical counterparts. • Mode-I crack in a medium with microstructure and initial stress is studied. • Size-dependent energy release rates are shown. • Force-stress has no singularity and couple-stress has an inverse square-root singularity. • Introduction of the characteristic length decreases the energy release rate. • Tensile initial stress retards the crack to advance and vice versa. [ABSTRACT FROM AUTHOR]

Multiferroic devices often serve under harmonic vibration. Resonance induced cracking is a common failure of them. The present work studies the resonant fracture of a multiferroic cylindrical structure by the combined methods of variable separation, infinite series, singular integral equation and Lobatto–Chebyshev collocation. It is found that complex modulus and residual stress are two important factors governing the resonant fracture behavior. Generally, the loss factors only affect the resonant amplitude of the fracture parameter, but the residual stress affects both the resonant amplitude and frequency. The obtained conclusions can provide guidelines for the anti-fracture optimal designs of multiferroic devices. [ABSTRACT FROM AUTHOR]

This paper addresses the transference of Rayleigh waves in orthotropic layer with corrugated boundary over a pre-stressed orthotropic half-space with self-weight . This study is confined to identify the Rayleigh wave propagation under the effect of initial stress and gravity in orthotropic medium. Variable separable method has been adopted to get an analytic solution for the problem. Effects of corrugation, height of the layer, initial stress, density and gravity on Rayleigh wave propagation are marked separately. Frequency equations are obtained under certain boundary conditions. Frequency curves are plotted against phase velocity, wave number and wavelength. Some particular cases have been deduced. Numerical results have been presented by means of graph. [ABSTRACT FROM AUTHOR]

In this paper we study the propagation of Rayleigh-type wave in a heterogeneous transversely isotropic elastic layer with initial stress resting on a rigid foundation. Frequency equation is obtained in closed form. The frequency equation being a function of phase velocity, wave number, initial stress and heterogeneous parameter associated with the rigidity and density of inhomogeneous layer reveals the fact that Rayleigh-type wave propagation is greatly influenced by above stated parameters. In Numerical and graphical computation the significant effects of distortional velocity have been carried out. Moreover, the obtained dispersion relation is found in well–agreement to the classical case in isotropic and transversely isotropic layer resting on a rigid foundation. [ABSTRACT FROM AUTHOR]

The main objective of the study is to investigate the effects of parameters on wave propagation in a viscoelastic sandy medium lying over an elastic orthotropic half-space under initial stress. The frequency equation for Love waves has been deduced in a closed form. To examine the effects of initial stress, sandiness and viscoelastic parameters, we have calculated the numerical values for phase velocity and attenuation coefficient. The phase velocity and attenuation coefficient have been plotted against wave number of different values of initial stress, sandiness and viscoelastic parameters. It is observed that the phase velocity and attenuation coefficient have been influenced by the increase of proposed parameters. The theme can be of interest for geophysical applications in propagation of Love waves in the Earth's crust. [ABSTRACT FROM AUTHOR]

The present paper devotes the propagation of SH-wave in an irregular anisotropic self-reinforced layer lying over an initially stressed porous half-space. The various affecting parameter viz. irregularity depth, initial stress and porosity have their prominent effects on the phase velocity of SH-wave. To detect the substantial effect of these affecting parameters on the phase velocity of SH-wave, analytical computation and correspondingly graphical demonstration have been done. The dispersion equation has been established in closed form and found to be in good agreement with the Classical Love wave equation. The comparative study has been made between with reinforcement and without reinforcement structure models. Moreover, as and illustration, the overall effects of reinforcement and without reinforcement consolidated with irregularity and porosity are accentuated through graphs. [ABSTRACT FROM AUTHOR]

The present paper is concerned with the study of propagation of torsional surface waves in a non-homogeneous crustal layer under initial stress overlying a viscoelastic half-space. In the layer directional rigidities and density are considered to vary quadratically with depth. The dispersion equation is derived in closed form by means of separation of variables. As a special case when the layer is homogeneous, the dispersion relation coincides with the classical torsional wave equation. To show the nature of torsional waves, dispersion curves have been plotted by taking variation in initial stress, inhomogeneity and viscoelastic parameters. The substantial influence of initial stress, heterogeneity and viscoelastic parameter on the phase velocity are elucidated by means of graphs. This problem may find its applications in the field of earthquake engineering and geophysical prospects. [ABSTRACT FROM AUTHOR]

In the present work, the possibility of torsional surface waves in dry sandy layer under initial stress over an inhomogeneous half-space has been carried out. The inhomogeneities in the lower semi-infinite media arise due to the polynomial variation of rigidity and density. The closed form expression for the dispersion relation of this proposed layer has been delineated by means of separation of variable method in the form of Whittaker function and its derivative retaining up to linear term. An extensive analysis has been achieved through numerical computation which explores the influence of inhomogeneity, initial stresses, sandy parameter on the torsional wave propagation have also been exhibited graphically. The obtained dispersion relation is in perfect agreement with the classical Love wave equation when derived as in particular cases. Using MATLAB software GUI has been evolved to generalize the effect of various parameters. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the influence of magnetism with gravity on propagation of Surface waves. Geometry of the problem is consists of a liquid layer lying over a gravitational, magnetoelastic orthotropic half-space. Frequency equation for Rayleigh wave has been obtained. Some existing results have been deduced as particular case of the present study. Obtained results have been shown through numerical illustrations. It is found that the considered parameters (earth magnetism, density and gravity) have prominent effect on phase velocity of Rayleigh wave. Graphical representation has been made to exhibit the velocity profile of Rayleigh waves for different cases. [ABSTRACT FROM AUTHOR]

The Present Paper devoted to investigate the effect of presence of rigid boundary on the propagation of torsional surface waves in a gravitating earth with a dry sandy medium under initial stress. The mathematical analysis of the problem has been dealt with the Whittaker function. Assuming the expansion of the Whittaker function up to linear term, it is concluded that the gravity field will always allow torsional waves to propagate in elastic and sandy medium under initial stress and rigid layer. Finally, it reveals that the sandy medium without support of a gravity field can not allow the propagation of torsional surface waves in presence of initial stress under rigid layer, where as the presence of a gravity field always supports the propagation of torsional surface waves regardless of whether the medium is elastic or dry sandy under rigid layer. [ABSTRACT FROM AUTHOR]

A novel technique is used to investigate the influence of magnetic field for a two dimensional deformations on a two temperature problem at the free surface of a semi-infinite medium. The investigation is carried out under the effects of both mechanical force and hydrostatic initial stress during a photothermal excitation theory. The equations of elastic waves, heat conduction equation, quasi-static electric field, carrier density, two temperature coefficient, ratios, and constitutive relationships for the thermo-magnetic-electric medium are obtained using the Harmonic Wave Method (HWM) technique. The effects of thermoelastic, thermoelectric and two temperature parameters of the applied force on the displacement component, force stress, carrier density and temperature distribution has been depicted graphically. [ABSTRACT FROM AUTHOR]

The couple-stress elasticity is applied to study an anti-plane shear crack at the interface between two bonded dissimilar elastic media with initial stresses. First, the deviatoric couple stress tensor is proven. The governing equation alongside associated boundary conditions is derived. Using the eigenfunction expansion method, the singularity index is determined. Then, the Fourier transform is employed to convert the mode-III interface crack problem to a hypersingular integral equation. Using the Chebyshev series method, the resulting hypersingular integral equation is numerically solved. The crack-tearing-displacement, couple-/force-stress intensity factors, and energy release rate are evaluated to reveal the influence of the intrinsic characteristic lengths, couple-stress material constants, and initial stresses. • Mode-III interface crack in a bi-material with couple stress and initial stress is studied. • Antiplane shear stresses near the crack tips have an r − 3 / 2 singularity. • Couple stresses near the crack tips have an r − 1 / 2 singularity. • The strains at the crack tips vanish and are no longer singular. • Effects of characteristic lengths and initial stresses on fracture parameters are analyzed. [ABSTRACT FROM AUTHOR]

Concrete-encased CFST (CE-CFST) member refers to a hybrid structure consisting of outer reinforced concrete and inner CFST components. This paper studies the compressive behavior of CE-CFST stub columns with initial stress on steel tube. Nine compression tests on CE-CFST stub columns were completed. The influences of initial stress degree and eccentricity on the failure mode, load-displacement behavior and ultimate strength were investigated. The crushed concretes with locally buckled longitudinal rebars were observed at the middle height of specimens. The ultimate strength of CE-CFST stub column slightly decreases as initial stress degree increasing. The maximum decreasing range on the ultimate compressive strength was 9.3% as the initial stress degree increasing in range of 0–0.5. A finite element model of CE-CFST stub column was developed and verified against test results. The parameters study and full-range compression process analysis were performed using the verified finite element model. The strength contribution provided by the inner CFST and outer RC components and interactions between concretes and steel tube were discussed. The influence mechanism of initial stress on the compressive behavior of CE-CFST stud column was revealed by the test and finite element results. The constraint effect on the core concrete provided by steel tube decreased due to the presence of initial stress, which reduced the strength contribution of the CFST component to the CE-CFST column. A simplified method was proposed to predict the influence coefficient of initial stress on the ultimate strength of the CE-CFST column based on the test and finite element results. • Compression tests of CE-CFST stud column with initial stress on steel tube were completed. • Finite element analysis of CE-CFST stud column with initial stress on steel tube was realized. • The influence mechanism of initial stress on compressive behavior of CE-CFST column was revealed. • The influence coefficient of initial stress on ultimate strength of CE-CFST column was proposed. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the stability of a plane Couette flow over non-linear solids undergoing homogeneous or inhomogeneous initial stresses. Almost all biological and engineering structures are subjected to complex initial residual stresses. We probe here the stability characteristics of a plane Couette flow over these stressed solid surfaces. Since initial stress is commonly inhomogeneous in Nature, our main focus is to analyze the stability of flow over inhomogeneously stressed solids at all Reynolds number regimes, which was not investigated earlier. We apply an initially stressed neo-Hookean solid model which precludes the necessity of using the stress-free reference. A linear perturbation analysis based on an Eulerian–Lagrangian formulation determines the stability associated with short and finite wave modes for zero, low, and high Reynolds number flows. In presence of a uniform initial stress field, the short wave modes are stabilized by tensile stresses and destabilized by compressive stresses in the limit of creeping flow. A similar influence of pre-stress is observed in buckling of columns. On the other hand, the case of spatially varying initial stress is far more intricate due to the inhomogeneous shearing of the solid in the unperturbed state. A linear perturbation introduced to this complicated unperturbed state presents several interesting observations. We find multiple unstable modes for low Reynolds number (R e ≪ 1) creeping flows which were not reported earlier to the best of our knowledge. While literature demonstrates only downstream unstable modes for a plane Couette flow, both upstream and downstream unstable modes are observed for inhomogeneously stressed solids in various Reynolds number regimes. In the creeping flow limit (R e = 0) , the stability depends mainly on the tensile or compressive initial stress at the solid–fluid interface. When this initial stress is compressive at the interface, only the finite wave modes determine the stability for all thicknesses instead of the short-wave modes. At higher Reynolds number, we report many more interesting results for spatially varying stress-fields which includes an unusual scaling of wall-mode validated through eigenmode analysis. [Display omitted] • We uncover the influence of initial stress in solids on the stability of adjacent Couette flow. • New modes of instability are invoked by non-uniform initial stress in solids. • New wall-mode scaling is reported at high Re for spatially-varying stress fields. [ABSTRACT FROM AUTHOR]

A mathematical model of fractional order two-temperature generalized thermoelasticity with diffusion and initial stress is proposed to analyze the transient wave phenomenon in an infinite thermoelastic half-space. The governing equations are derived in cylindrical coordinates for a two dimensional axi-symmetric problem. The analytical solution is procured by employing the Laplace and Hankel transforms for time and space variables respectively. The solutions are investigated in detail for a time dependent heat source. By using numerical inversion method of integral transforms, we obtain the solutions for displacement, stress, temperature and diffusion fields in physical domain. Computations are carried out for copper material and displayed graphically. The effect of fractional order parameter, two-temperature parameter, diffusion, initial stress and time on the different thermoelastic and diffusion fields is analyzed on the basis of analytical and numerical results. Some special cases have also been deduced from the present investigation. [ABSTRACT FROM AUTHOR]

A new numerical approach based on the weak form quadrature element method is proposed to study attenuation zones of initially stressed periodic Mindlin plates on an elastic foundation. The proposed method is validated by the results available in the previous studies of initially stressed homogeneous plates on elastic foundations. A comprehensive parametric study is conducted to highlight the effects of initial stress, geometric parameters and elastic foundation on the attenuation zones. The results show that the compressive initial stress shifts the attenuation zones to lower frequencies and enhances the attenuation of waves in the attenuation zones, while the tensile initial stress shifts the attenuation zones to higher frequencies and weakens the attenuation of waves in the attenuation zones. The elastic foundation shifts the attenuation zones to higher frequencies and narrows the width of the attenuation zones. In addition, wave propagation and attenuation in a periodic Mindlin plate with finite unit cells on an elastic foundation are examined. The results achieved in this paper are very useful for the design and application of periodic plates in vibration reduction in most of engineering fields. [ABSTRACT FROM AUTHOR]

Layered periodic foundations have been proposed to isolate seismic waves and support upper structures. Before seismic waves arrive, initial stress exists in the layered periodic foundation due to the load from the upper structures. Based on the weak form quadrature element method, this paper proposes a novel numerical approach to study the effect of initial stress on the attenuation zones of layered periodic foundations. Comparisons with existing results in special cases are conducted to validate the proposed method, and good agreement is found. The theoretical results illustrate that the compressive initial stress shifts the attenuation zones to a lower frequency range. In addition, the maximum attenuation coefficient in each attenuation zone is not affected by the initial stress. Furthermore, frequency-domain and time-domain response analyses of a building with a finite-unit cell layered foundation are conducted. The present work is very helpful for the design and application of periodic foundations in seismic isolation. [ABSTRACT FROM AUTHOR]

In this paper the propagation of small amplitude surface waves guided by a layer with a finite thickness on an incompressible half-space is studied. The layer and half-space are both assumed to be initially stressed. The combined effect of initial stress and finite deformation on the speed of Rayleigh waves is analyzed and illustrated graphically. With a suitable simple choice of constitutive law that includes initial stress, it is shown that in many cases, as is to be expected, the effect of a finite deformation (with an associated pre-stress) is very similar to that of an initial stress (without an accompanying finite deformation). However, by contrast, when the finite deformation and initial stress are considered together independently with a judicious choice of material parameters different features are found that do not appear in the separate finite deformation or initial stress situations on their own. [ABSTRACT FROM AUTHOR]

The paper aims to study, the effect of rigid boundary on the propagation of torsional surface waves in initially stressed gravitating dry sandy half space. The mathematical analysis of the problem has been dealt with the Whittaker function. Assuming the expansion of the Whittaker function up to linear term, it is concluded that the gravity field will always allow torsional waves to propagate. The expansion of the Whittaker function up to quadratic terms shows two such wave fronts may exist in the medium. Finally, it is concluded that the sandy medium without support of a gravity field cannot allow the propagation of torsional surface waves, where as the presence of gravity field always supports the propagation of torsional surface waves regardless of whether the medium is elastic or dry sandy. Numerical results analyzing the velocity equations are discussed and presented graphically. It has been observed that density, rigidities play an important role for the propagation of torsional surface waves. It has been seen that as the non-homogeneity parameter in the layer increases, the velocity of torsional surface wave also increases. It has also been observed that an increase in compressive initial stresses decreases the velocity of torsional surface wave. [ABSTRACT FROM AUTHOR]

A mathematical model has been developed for the analytical study of propagation of crack due to horizontally polarized shear wave (SH-wave) in an initially stressed inhomogeneous poroelastic strip. The expression of stress intensity factor for the force of constant intensity has been determined in closed form. The emphatic impact of various affecting parameters viz. speed of the crack, length of the crack, horizontal compressive or tensile initial stress, vertical compressive or tensile initial stress, heterogeneity parameter, porosity parameter and anisotropy parameter on the stress intensity factor in an initially stressed inhomogeneous poroelastic strip has been depicted by means of graphs. In order to solve the problem, Wiener–Hopf technique specified by Matczynski has been employed. Moreover, some special cases have been deduced from the procured expression of stress intensity factor for the force of constant intensity. [ABSTRACT FROM AUTHOR]

The dispersion relations of elastic waves in a one-dimensional phononic crystal formed by periodically repeating of a pre-stressed piezoelectric slab and a pre-stressed piezomagnetic slab are studied in this paper. The influences of initial stress on the dispersive relation are considered based on the incremental stress theory. First, the incremental stress theory of elastic solid is extended to the magneto-electro-elasto solid. The governing equations, constitutive equations, and boundary conditions of the incremental stresses in a magneto-electro-elasto solid are derived with consideration of the existence of initial stresses. Then, the transfer matrices of a pre-stressed piezoelectric slab and a pre-stressed piezomagnetic slab are formulated, respectively. The total transfer matrix of a single cell in the phononic crystal is obtained by the multiplication of two transfer matrixes related with two adjacent slabs. Furthermore, the Bloch theorem is used to obtain the dispersive equations of in-plane and anti-plane Bloch waves. The dispersive equations are solved numerically and the numerical results are shown graphically. The oblique propagation and the normal propagation situations are both considered. In the case of normal propagation of elastic waves, the analytical expressions of the dispersion equation are derived and compared with other literatures. The influences of initial stresses, including the normal initial stresses and shear initial stresses, on the dispersive relations are both discussed based on the numerical results. [ABSTRACT FROM AUTHOR]

We study the behavior of torsional surface waves when they propagate through inhomogeneous fluid saturated porous layer over a homogeneous porous half space. The layer has three types of inhomogeneity, viz; linear, quadratic and exponential, varies with depth as rigidity, density and initial stress. We assume both media under compressive initial stresses and the analysis is based on the Biot’s theory. The effect of inhomogeneity of the layer in the propagation of torsional surface waves have been studied. The dispersion equations are derived for each case and solved by an iterative method (Newton–Raphson method). It is observed from the numerical calculation that the presence of initial stress and inhomogeneity of the medium affect significantly to the phase velocity of torsional surface waves. Also, propagation of torsional surface waves depend upon the medium in which they propagate as torsional surface waves propagate fastly in presence of elastic half space in comparison to porous half space. [ABSTRACT FROM AUTHOR]

An analytical approach is taken to investigate shear horizontal wave (SH wave) propagation in layered cylinder with initial stress, where a piezomagnetic (PM) material thin layer is bonded to a piezoelectric (PE) cylinder. Two different material combinations are taken into account, and the phase velocities of the SH waves are numerically calculated for the magnetically open and short cases, respectively. It is found that the initial stress, the thickness ratio and the material performance have a great influence on the phase velocity. The results obtained in this paper can offer fundamental significance to the application of PE/PM composite media or structure for the acoustic wave and microwave technologies. [ABSTRACT FROM AUTHOR]

Fracture of a pre-stressed thin elastic layer is studied and modelled as bending of double clamped beams with axial force. Using the beam theory, the strain energy in bending state of the beam with an axial force is derived. Explicit expressions for energy release rate and stress intensity factor (SIF) for a crack with initial transverse stress (T-stress) are obtained. Results show that tensile (compressive) initial T-stress decreases (increases) the SIF and impedes (promotes) crack growth. The influence of compressive initial stress is greater than that of tensile initial stress in the same magnitude. [ABSTRACT FROM AUTHOR]

The presence of initial stress in solids changes the material's response to finite and infinitesimal deformations. This paper presents a study on the effects of initial stress, finite deformation, and material properties on the speed of interfacial waves which are assumed to travel at the joint boundary of two incompressible half-spaces. The theory of infinitesimal deformations superimposed on finite deformations is used along with the theory of invariants. Boundary conditions at the interface result in an explicit secular equation, which is analyzed generally. For each half-space, a prototype strain–energy function is assumed, which is a function of the deformation gradient and initial stress tensors. The effect of different governing parameters is observed on the wave speed and is analyzed theoretically. Graphical illustrations are also presented to elaborate on the theoretical results. It is observed that for admissible values of parameters, a real wave speed exists and is bounded by values depending on the governing parameters. A comparison between Rayleigh and interfacial wave speeds is also made and supported with graphs of dimensionless wave speeds with respect to initial stresses. • The effect of initial stress on the interfacial waves is studied. • An explicit secular equation is obtained which is analyzed generally. • For a particular strain–energy function, a real wave speed exists which is bounded. • A comparison between Rayleigh and interfacial wave speeds is also presented. • It is found that the interfacial wave speed is affected by the initial-stress. [ABSTRACT FROM AUTHOR]

Periodic pile barriers exhibit unique dynamic property, i.e., the frequency attenuation zones. When wave frequencies fall in the attenuation zones, the amplitude of the elastic waves could be reduced by the periodic pile barriers. In the present paper, out-of-plane waves propagating in two-dimensional periodic pile barriers are investigated. A novel numerical approach based on the weak form quadrature element method (WFQEM) is developed to study the effect of initial stress on the attenuation zones of the pile barriers. The proposed method is verified to be with significant advantages in both accuracy and convergence with regard to the lumped-mass method (LMM) in particular cases. The theoretical results show that the initial stress significantly alters the position and width of the attenuation zones, however, it does not affect the maximum attenuation coefficient. In addition, elastic waves propagating in periodic pile barriers with finite number of unit cells is simulated at the end of this paper. The results obtained in the present paper are very useful for the design and application of periodic pile barriers in ambient vibration reduction. [ABSTRACT FROM AUTHOR]

The paper studies the effects of the magnetic field and initial stress on the reflection of a plane magneto-thermoelastic wave from the boundary of a solid half-space. The basic dynamical equations of thermoelasticity in presence of Lorentz force and the heat conduction equation of Green–Lindsay theory have been solved to derive the wave equations for the reflected P-, SV- and thermal waves. By considering the boundary to be a stress-free and insulated one, the boundary equations that contain the ratios of the amplitude of the reflected components to that of the incident wave have been obtained. The analytical solution has been cast in matrix form for each of the incident plane waves at the boundary, namely the P-wave, SV-wave and thermal wave. The numerical calculations of the absolute values of the amplitude ratios for an incident SV-wave have been carried out for different values of both magnetic pressure number and initial stress parameter. The initial stress parameter shows a marked influence on the magnitude of the amplitude ratios. The reflection coefficients for different values of magnetic pressure number in absence of initial stress have also been included for the sake of comparison. [ABSTRACT FROM AUTHOR]

The present paper investigates the propagation of horizontally polarised shear wave in distinct vertically heterogeneous double layers overlying an isotropic half-space under horizontal initial stress. The vertical heterogeneity in the uppermost layer is caused due to quadratic variation only in rigidity, whereas vertical heterogeneity in the sandwiched layer is caused due to exponential variation in rigidity and density both. The closed form of velocity equation is obtained which leads to the dispersion equation as its real part and damping equation as its imaginary part. The validation of dispersion relation with the classical case is made by using Debye asymptotic expansion which is the major highlight of this study. The significant effect of the width ratio of the layers, heterogeneity parameters of both the layers and horizontal compressive/tensile initial stress on the phase velocity and damped velocity of SH-wave have been traced out. The comparative study and some important peculiarities have been revealed by means of graphical illustrations. [ABSTRACT FROM AUTHOR]

Residual stresses existing in a multi-pass butt joint with a thickness of 70 mm, using a flux-cored arc welding process, were measured by an inherent strain method (ISM). Since such a thick plate before welding contains a large amount of initial residual stresses (−300 to +100 MPa), the initial stresses were integrated with conventional ISM in order to determine the total residual stresses in a welded joint. Two methods named as initial stress integrated ISM and initial inherent strain integrated ISM were suggested for the consideration of the initial stress distributions through the thickness of base plates. The results show that there is a significant difference between the integrated ISM with initial stresses or initial inherent strain and the conventional ISM without initial stresses. The residual stresses measured by any of the initial stress integrated ISM and initial inherent strain integrated ISM agreed well with the neutron diffraction measurement. Thus, the proposed initial stress integrated ISM is a proper destructive measurement method in the case of thick weld joints. [ABSTRACT FROM AUTHOR]

This paper investigates the electro-thermal nonlocal wave propagation of fluid-conveying single-walled Boron Nitride nanotubes (SWBNNTs) using nonlocal piezoelasticity with surface stress, initial stress and Knudsen-dependent flow velocity effect. SWBNNT is embedded in a vicsoelastic medium which is simulated as visco-Pasternak foundation. Using Euler–Bernoulli beam (EBB) model, Hamilton׳s principle and nonlocal piezoelasticity theory, the higher order governing equation is derived. A detailed parametric study is conducted, focusing on the combined effects of the electric parameters, viscoelastic medium, initial stress, surface stress, Knudsen number ( K n ) and small scale on the wave propagation behaviour of the fluid-conveying SWBNNT. The results show that for smaller values of wave number the dispersion relation for different fluid viscosities seems to be similar. At the higher values of wave numbers, increase in the wave frequency values is remarkable due to increase in fluid viscosity. The electric field as a smart controller, surface effect, initial stress, temperature change and slip velocity effect have significant role on the wave frequency. The results of this work is hoped to be of use in design and manufacturing of smart MEMS/NEMS in advanced medical applications such as drug delivery systems with great applications in biomechanics. [ABSTRACT FROM AUTHOR]

In this paper, a nonlocal continuum plate model is developed for the transverse vibration of double-piezoelectric-nanoplate systems (DPNPSs) with initial stress under an external electric voltage. The Pasternak foundation model is employed to take into account the effect of shearing between the two piezoelectric nanoplates in combination with normal behavior of coupling elastic medium. Size effects are taken into consideration using nonlocal continuum mechanics. Hamilton?s principle is used to derive the differential equations of motion. The governing equations are solved for various boundary conditions by using the differential quadrature method (DQM). In addition, exact solutions are presented for the natural frequencies and critical electric voltages of DPNPS under biaxial prestressed conditions in in-phase and out-of-phase vibrational modes. It is shown that the natural frequencies of the DPNPS are quite sensitive to both nonlocal parameter and initial stress. The effects of in-plane preload and small scale are very important in the resonance mode of smart nanostructures using piezoelectric nanoplates. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effects of both initial stress, radially varying and gravity field on the peristaltic flow of an incompressible MHD Newtonian fluid in a vertical annulus have been studied under the assumption of long wavelength and low-Reynolds number. The analytical solution has been derived for the temperature, concentration and velocity. The results for velocity, concentration and temperature obtained in the analytical form have been evaluated numerically and discussed briefly. The effect of the non-dimensional wave amplitude, the coefficient of viscosity, Sort number, Schmidt number, initial stress, gravitational field and the dimensionless time-mean flow in the wave frame are analyzed theoretically and computed numerically. The expressions for pressure rise, temperature, concentration field, velocity and pressure gradient are sketched for various embedded parameters and interpreted. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of initial stress and gravitational field. [Copyright &y& Elsevier]

Abstract: This article presents an analytical study, by considering the initial stress presence, for the transverse vibrations of single-walled carbon nanotubes under longitudinal magnetic field. The behavior of single-walled carbon nanotube is modelled as a Timoshenko beam. The explicit solutions are derived for both a combined stress/strain and a combined strain/inertia gradient elasticity theories. A numerical application is carried out for a simply supported single walled carbon nanotube. The numerical results showing the effects of initial stress and longitudinal magnetic field are presented in detail, for the different length scale parameters. This analysis reveals new significant findings for the critical buckling stress and the different capabilities of scale parameters under the magnetic field. This work carried out for the effect of longitudinal magnetic field on the wave propagation in the carbon nanotubes containing the initial stress may be useful particularly in the design and applications of nano electro mechanical systems. [Copyright &y& Elsevier]