Edge wave propagation in an Electro-Magneto-Thermoelastic homogeneous plate subjected to stress

Rajneesh Kakar,Shikha Kakar 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6

This paper introduces the combined effect of electric field, magnetic field and thermal field on edge wave propagating in a homogeneous isotropic prestressed plate of finite thickness and infinite length. The dispersion relation of edge wave has been obtained by using classical dynamical theory of thermoelasticity. The phase velocity has been computed and shown graphically for various initial stress parameter, electro-magneto parameter, electric parameter and thermoelastic coupling parameter.

Vertical-slate-like MoS2 nanostructures on 3D-Ni-foam for binder-free, lowcost, and scalable solid-state symmetric supercapacitors

Rajneesh Kumar Mishra,Ajay Kumar Kushwaha,김승엽,서승기,진성훈 한국물리학회 2019 Current Applied Physics Vol.19 No.1

Here, we report binder-free vertical-slate-like MoS2 nanostructures on 3D-Ni-Foam (VSL-MoS2@3D-Ni foam) for low-cost high-performance solid-state symmetric supercapacitors (SSCs). The cost-effective, ecofriendly and scalable solvothermal method and its direct incorporation of VSL-MoS2@3D-Ni-foam yield SSCs with excellent electrochemical properties with a wide potential window of 1.0 V. Furthermore, high specific capacitance of 34.1 F g−1 at a current density of 1.3 A g−1, an energy density of 4.7Wh kg−1 at a high-power density of 650Wkg−1, and excellent stability with ∼82.5% capacitance retention after 10,000 cycles were demonstrated even for SSCs with a binder free MoS2 electrodes on 3D-Ni-foam. These excellent features of the SSCs with VSLMoS2@ 3D-Ni-foam substantiate their potential opportunity for future energy applications.

Effects of Hall current in a transversely isotropic magnetothermoelastic with and without energy dissipation due to normal force

Rajneesh Kumar,Nidhi Sharma,Parveen Lata 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.1

This investigation is concerned with the disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperature, in the presence of the combined effects of Hall currents and magnetic field due to normal force of ramp type. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi Theories of Type-II and Type-III. Laplace and Fourier transform technique is applied to solve the problem. The analytical expressions of displacements, stress components, temperature change and current density components are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerically simulated results are depicted graphically to show the effects of Hall current and anisotropy on the resulting quantities. Some special cases are also deduced from the present investigation.

SH-wave in a piezomagnetic layer overlying an initially stressed orthotropic half-space

Rajneesh Kakar,Shikha Kakar 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.2

The existence of SH-wave in a piezomagnetic layer overlying an initially stressed orthotropic half-space is investigated. The coupled of differential equations are solved for piezomagnetic layer overlying an orthotropic elastic half-space. The general dispersion equation has been derived for both magnetically open circuit and magnetically closed circuits under the four types of boundary conditions. In the absence of the piezomagnetic properties, initial stress and orthotropic properties of the medium, the dispersion equations reduce to classical Love equation. The SH-wave velocity has been calculated numerically for both magnetically open circuit and closed circuits. The effect of initial stress and magnetic permeability are illustrated by graphs in both the cases. The velocity of SH-wave decreases with the increment of wave number.

Shear wave in a fiber-reinforced anisotropic layer overlying a pre-stressed porous half space with self-weight

Rajneesh Kakar,Shikha Kakar 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.5

The main purpose of this paper is to study the effects of initial stress, gravity, anisotropy and porosity on the propagation of shear wave (SH-waves) in a fiber-reinforced layer placed over a porous media. The frequency equations in a closed form have been derived for SH-waves by applying suitable boundary conditions. The frequency equations have been expanded and approximated up to 2nd order of Whittaker\'s function. It has been observed that the SH-wave velocity decreases as width of fiber-reinforced layer increases. However, with the increase of initial stress, gravity parameter and porosity, the phase velocity increases. The results obtained are in perfect agreement with the standard results investigated by other relevant researchers.

Dynamic problem of generalized thermoelastic diffusive medium

Rajneesh Kumar,Tarun Kansal 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1

The equations of generalized thermoelastic diffusion, based on the theory of Lord and Shulman with one relaxation time, are derived for anisotropic media with rotation. The variational principle and reciprocity theorem for the governing equations are derived. The propagation of leaky Rayleigh waves in a viscous fluid layer overlying a homogeneous isotropic, generalized thermoelastic diffusive halfspace with rotating frame of reference is studied.

A parametric study of the 2D model of solar air heater with elliptical rib roughness using CFD

Rajneesh Kumar,Varun Geol,Anoop Kumar 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

The heat transfer can be improved by providing artificial roughness on absorber plate of the solar air heat. Many studies are available on circular, semi-circular, triangular and rectangular rib roughened solar air heater. But in present study heat transfer enhancement by providing elliptical ribs on absorber plate was analyzed by developing CFD code on non-commercial ANSYS (Fluent) 12.1 software. The simulations were performed on 2-D CFD model and analysis was carried out to study the effect of relative roughness width, relative roughness height and relative roughness pitch on heat transfer and friction factor. The Reynolds number range from 4000 to 15000 and turbulence phenomena is modeled by using Reynolds-average Navier-Stokes equations (RANS). The mathematical modeling is validated and compared with available results. The strong vortex formation takes place in the main stream flow because of elliptical roughness, which improved heat transfer augmentation in the solar air heater. The local turbulence kinetic energy strongly influenced by orientation of the elliptical ribs. The value of average Nusselt number increases by increasing relative roughness height but it decreases with the increase of relative roughness width and relative roughness pitch. The rib width has significant effects on heat transfer enhancement and maximum Nusselt number is observed for relatively small roughness width (i.e., 0.5) among the considered range of 0.5 mm to 2.0 mm. The maximum value of Nusselt number and friction factor is observed for relative roughness width of 0.5, relative roughness height of 0.045, and relative roughness pitch of 6.

Shear waves propagation in an initially stressed piezoelectric layer imperfectly bonded over a micropolar elastic half space

Rajneesh Kumar,Kulwinder Singh,D.S. Pathania 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.2

The present study investigates the propagation of shear waves in a composite structure comprised of imperfectly bonded piezoelectric layer with a micropolar half space. Piezoelectric layer is considered to be initially stressed. Micropolar theory of elasticity has been employed which is most suitable to explain the size effects on small length scale. The general dispersion equations for the existence of waves in the coupled structure are obtained analytically in the closed form. Some particular cases have been discussed and in one particular case the dispersion relation is in well agreement to the classical-Love wave equation. The effects of various parameters viz. initial stress, interfacial imperfection and micropolarity on the phase velocity are obtained for electrically open and mechanically free system. Numerical computations are carried out and results are depicted graphically to illustrate the utility of the problem. The phase velocity of the shear waves is found to be influenced by initial stress, interface imperfection and the presence of micropolarity in the elastic half space. The theoretical results obtained are useful for the design of high performance surface acoustic devices.

Dispersion of shear wave in a pre-stressed hetrogeneous orthotropic layer over a pre-stressed anisotropic porous half-space with self-weight

Rajneesh Kakar,Shikha Kakar 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.6

The purpose of this study is to illustrate the propagation of the shear waves (SH-waves) in a prestressed hetrogeneous orthotropic media overlying a pre-stressed anisotropic porous half-space with self weight. It is considered that the compressive initial stress, mass density and moduli of rigidity of the upper layer are space dependent. The proposed model is solved to obtain the different dispersion relations for the SH-wave in the elastic-porous medium of different properties. The effects of compressive and tensile stresses along with the heterogeneity, porosity, Biot‟s gravity parameter on the dispersion of SH-wave are shown numerically. The wave analysis further indicates that the technical parameters of upper and lower half-space affect the wave velocity significantly. The results may be useful to understand the nature of seismic wave propagation in geophysical applications and in the field of earthquake and material science engineering.

Propagation of love-type wave in a temperature dependent crustal Layer

Rajneesh Kakar,Shikha Kakar,Rajeev Kumar Narang 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.3

The present study deals with the propagation of Love wave (a type of surface wave) in crustal layer having temperature dependent inhomogeneity. It is assumed that the inhomogeneity in the crustal layer arises due to linear temperature variation in rigidity and density. The upper boundary of the crustal layer is traction free. Numerical results for Love wave are discussed by plotting analytical curves between phase velocity against wave number and stress against depth in the presence of inhomogeneity and temperature parameters. The effects boundary condition on the Love wave propagation in the crustal layer is also analyzed. The results presented in this study would be useful for seismologists and geologists.