In this paper, case wise studies have been made to investigate the possibility of propagation of Rayleigh-type wave in a composite structure comprised of two transversely-isotropic material layers with viscoelastic effect. The common interface between the layers is considered to be rigid whereas the base has been considered as rigid, stress-free and yielding in three different cases (Case-I, II and III). Closed-form of frequency equation and damped velocity equation has been established analytically for propagation of Rayleigh-type wave in a composite structure for all three cases. In special cases, frequency equations and damped velocity equations for the case of composite structure with rigid, stress-free and yielding base have been found in well-agreement to the established standard results pre-existing in the literature. Numerical and graphical computation of phase and damped velocity of Rayleigh-type wave propagating in the composite structure comprised of double transversely-isotropic viscoelastic Taylor sandstone material layers (Model-I) and double isotropic viscoelastic material layers (Model-II) have been carried out. Significant effect of anisotropy and width ratio of layers, dilatational and volume viscoelasticity associated with viscoelasticity of layer medium and yielding parameter associated with yielding base of composite structure on phase and damped velocities of Rayleigh-type wave for the considered models have been traced out. The comparative study has been performed to unravel the effect of viscoelasticity over elasticity and anisotropy over isotropy in the present problem.

The position determination for rock bolt support design based on rock stress distribution is important in ensuring full mobilization of rock bolt tensions during excavation process. The monitoring of the progressive rock stress variation in magnitude and orientation can play an important role in optimal installation of rock bolt. The aim of this paper is to determine the optimal positions for rock bolt installation by computing the progressive directional variation of rock stresses and plot the stress distribution in a two-dimensional stereographic projection to capture the stress transformation during excavation process. Finally, an algorithm based on stress transformation determination for optimal rock bolt installation is proposed.

Most topology optimization methods seek optimal topologies that satisfy a minimum compliance with a pre-specified volume constraint in the design domain. However, practical designs often include various functional constraints and the optimal solid volume ratios are unknown a priori, which implies a gap between topology optimization methods and practical designs in industries. This paper studies the performance-based topology optimization (PTO) problem that searches for the optimal topology with minimum compliance to satisfy the pre-specified functional constraints without a pre-specified volume constraint. A novel element-based evolutionary switching method (ESM), which can automatically adjust solid volume ratio and material distribution, is developed and implemented using the commercial finite element software ABAQUS. The effects of displacement constraints on the optimal topologies are investigated, and the differences between PTO problems and the topology optimization problem which has a volume constraint are discussed. Numerical examples demonstrate that the optimal topologies are mainly determined by the load pattern and locally changed with respect to the location of the active displacement constraints. In addition, the displacement constraints to a large extent control the solid volume ratio of optimal topologies according to the allowable displacements in PTO problems. Finally, the proposed ESM could provide conservative solutions to the topology optimization with multiple displacement constraints problems.

A family of structure-dependent integration methods has been proposed by Gui et al. for time integration. Although it has desirable numerical properties, such as unconditional stability, explicit formulation and second-order accuracy, it has some adverse properties, such as a poor capability to capture structural nonlinearity, an overshoot in a high frequency steady- state response and a weak instability in the high frequency response of nonzero initial conditions. The causes of these adverse properties are explored. A poor capability to capture structural nonlinearity may originate from the convergence rate of 1 in velocity error. This family method has an overshoot in a high frequency steady-state response and this overshoot can be eliminated by adding a load-dependent term into the displacement difference equation. It is also analytically verified that the family method generally has no weak instability. However, the special member with λ = 4, i.e., CR explicit method, is shown to have a weak instability. Thus, it must be prohibited from practical applications although many applications of this method were found in the literature.

The present study is to focus on the two dimensional problem of micropolar porous circular plate with three phase lag model within the context of two temperatures generalized thermoelasticity theory. The problem is solved by applying Laplace and Hankel transforms after using potential functions. The expressions of displacements, microrotation, volume fraction field, temperature distribution and stresses are obtained in the transformed domain. To show the utility of the approach, normal force and thermal source are taken. The numerical inversion techniques of transforms have been carried out in order to evaluate the resulting quantities in the physical domain. Finally, the resulting quantities are depicted graphically to show the effect of porosity, two temperatures and phase lags.

The effect of sulcus vocalis on vocal folds function is investigated. A type II sulcus vocalis is defined, parameterized and incorporated into a three-dimensional, fully coupled finite element model of vocal folds and laryngeal airway. The proposed Fluid-Structure Interaction (FSI) model is utilized in computational fluid dynamics, Arbitrary Lagrangian-Eulerian (ALE), incompressible continuity and Navier-Stokes equations and in a structure range of a three-layer elastic linear model. Flow parameters, vibration behavior and glottal jet aerodynamics of healthy and patient vocal folds models are compared with each other. Flow visualization is utilized to characterize Coanda effect and three dimensionality of flow patterns. The vibration frequency of vocal folds having sulcus vocalis decreases in comparison with that of healthy ones. Upon increasing the volume flux in the sulcus vocalis model, the non-periodic and disordered behavior of it is visible for patient vocal folds. Underlying mechanisms for the observed changes, possible implications for treatments of sulcus vocalis and human perfect voice production are also discussed.

This paper intends to study the dispersion and attenuation characteristics of Love-type wave propagation due to a disturbance point source in a hydrostatic stressed magneto-viscoelastic layer, lying over a heterogeneous fibre-reinforced elastic half-space. The shear elastic moduli and mass density of half-space are the functions of depth and heterogeneity parameters. The coupled field equations are solved with the aid of Green's function technique and Fourier transform. The dispersion and damping equations have been obtained for the wave. The deduced equations coincide with the classical Love-wave condition for the uniform homogeneous isotropic structure. Numerical computations are carried out for involved parameters and demonstrated with the help of graphs. The effects of hydrostatic stress, magnetic coupling parameter, dissipation factor, attenuation coefficient, reinforcement parameters, heterogeneity parameters and order of the depth variation on the dispersion and damping curves are highlighted.

This article focus on the rigid-liquid coupling dynamics of the spacecraft with arbitrary axisymmetrical tanks with curved walls and top. The carrier velocity potential function was obtained according to the motion equations of a representative point in the tank of spacecraft, and the relative velocity potential function can be expressed as Gauss hypergeometric series. The Hamilton's variational principle was applied to derive the governing equations of liquid sloshing based on the profile of hydrostatic shape of free liquid surface. The dynamic equations of modal coordinates were established through the Galerkin method. The state equations of coupled motion of main rigid platform of the spacecraft were deduced by using the Lagrange's equations in term of general quasi-coordinates. Thruster firing was actuated to the coupled system to analyze the rigid-liquid coupled dynamic behaviors. Computer numerical simulations was carried out to confirm the validity of the method developed in this paper.

In engineering industries, composite laminates have been widely applied for various applications. This work presents an efficient analysis of the interlaminar stresses in three-dimensional thin layered anisotropic composites by the boundary element method (BEM). Due to the nearly singular integrals in the boundary integral equation, the conventional BEM approach cannot be applied to analyze the composite layers that are very thin. The present work employs the self-regularization scheme to analyze the interlaminar stresses in thin anisotropic composites. In the end, a few benchmark examples are presented to show the applicability of the present approach.

In the recent years, the development of wind turbines has been so hectic in Taiwan. The design of the turbine blades directly impacts power effectiveness. In this study, the effects of manufacturing parameters and environmental factors on the mechanical properties of carbon fiber/epoxy composites that are used in turbine blades are discussed. Parameters of the manufacturing process affect the mechanical properties. Carbon composites made by a different numbers of layers are tested on various aspects of performance such as mechanical strength and corrosion resistance.

In this article, surface and nonlocal effects are explored in the analysis of buckling and vibration in rectangular single-layered graphene sheets embedded in elastic media and subjected to coupled in-plane loadings and thermal conditions. The small-scale and surface effects are taken into account using the Eringen's nonlocal elasticity and Gurtin-Murdoch's theory, respectively. Using the principle of virtual work, the governing equations considering small-scale are derived for the nanoplate bulk and surface. The differential quadrature method (DQM) is utilized for the solution of the relevant problems and the results are validated against Navier's solutions. The impacts of the nonlocal parameter, Winkler and shear elastic moduli, temperature rise, boundary conditions, and the in-plane biaxial, uniaxial, and shear loadings on the surface effects of buckling and vibration are investigated. Numerical results show that increasing nonlocal parameter leads to enhanced surface effects on both buckling and vibration. This is in contrast to those reported elsewhere. Moreover, increasing in-plane loads are observed to enhance surface effects on vibration. On the other hand, the nonlocal parameter is observed to have more pronounced effects on shear buckling and vibration of plates subjected to coupled in-plane shear loads than those subjected to biaxial and uniaxial loads. This is while surface effects have greater impacts on biaxial buckling and vibration of nanoplates than on shear buckling and vibration.

The dynamic ground effect enhances the swimming of fish. The dynamic ground effect affects the kinematic conditions of fish, causing them to swim more efficiently. However, predicting the degree to which the dynamic ground effect can improve the swimming performance of fish is difficult. The dynamic ground effect can potentially save energy for biomimetic underwater vehicles. Therefore, a theoretical model was developed to investigate the effect of a planar boundary on the swimming performance of a two-dimensional undulating plate. General expressions for the thrust, power input, efficiency, and energy loss of the plate were obtained. As examples, cases in which an undulating plate with linearly varying amplitude swam far from and close to a wall under a range of different kinematic conditions were studied. The dynamic ground effect improved the swimming performance of the plate by reducing the power input while maintaining an almost constant thrust; the degree of improvement depended on the kinematic conditions of the plate. Furthermore, the swimming performance of the plate was improved over a range of distances from the wall; this range of distances also depended on the kinematic conditions of the plate.