Showing papers by "Nantu Sarkar published in 2022"

Nonlocal elasticity and thermal dual‐phase‐lag effect on the vibration analysis of transversely isotropic electro‐magneto generalized thermoelastic sphere with voids

Abstract: The nonlocal elasticity together with electro‐magneto thermal dual‐phase‐lag (DPL) model to a transversely isotropic generalized thermoelastic hollow sphere with voids is addressed in radial direction. The governing equations and stress–strain‐displacement relations have been resolved by applying time harmonics technique. The elimination technique is employed to resolve the homogeneous equations to find the unknowns. The unknowns such as dilatation, displacement, voids volume fraction, temperature change, and radial/de‐hoop stresses have been calculated analytically. In order to discover the vibration analysis, the numerical Iteration method has been applied to thermally insulated/isothermal boundary conditions. For computation purpose the software like MATLAB tool has been used. The real parts of generated data obtained from the frequency equations have also been shown graphically to frequency shift and natural frequencies. The effects of DPL model of the theory of generalized transversely isotropic thermoelasticity with voids have been represented with and without the effects of magnetic field for nonlocal/local elastic materials and validated with existing literature.

Plane waves in nonlocal generalized thermoelasticity

Abstract: The Lord–Shulman (LS) model of generalized thermoelasticity and the Eringen's model of nonlocal elasticity are used to formulate the new constitutive relations and the field equations. The propagation of plane thermoelastic waves are then probed in a homogeneous isotropic nonlocal thermoelastic solid by employing this new model. We found two sets of the coupled longitudinal waves and one independent shear‐type wave. All these waves are found to be dispersive and attenuating in nature in the presence of nonlocality in the medium. We found that the shear‐type wave faces a critical frequency, while the coupled longitudinal waves may face critical frequency conditionally. A reflection of thermoelastic waves at a stress‐free thermally insulated and isothermal boundary of a thermoelastic half‐space are also considered in case of incident coupled longitudinal thermoelastic wave. The amplitude ratios of the reflected waves to that incident wave are determined analytically. For a particular model, various graphs are plotted to analyze the behavior of the phase speeds, attenuation coefficients and reflection coefficients. To investigate the effect of elastic nonlocal parameter on the variations of phase speeds, attenuation coefficients and amplitude ratios of the reflected waves are presented graphically. Some interesting results are noticed: All the waves are detected to be influenced by the nonlocality of the medium. The longitudinal waves are influenced by the thermal parameters but the shear‐type wave is independent of the thermal effect. Moreover the presence of elastic nonlocality reduces the classical shear‐type wave speed.

Vibration analysis of electro-magneto transversely isotropic non-local thermoelastic cylinder with voids material

Abstract: The free vibrations of transversely isotropic nonlocal electro-magneto thermoelastic hollow cylinder with voids are addressed in the preview of generalized thermoelasticity. The governing equations and the constitutive relations are transformed into coupled ordinary differential equations by applying time harmonic variations. The boundary conditions of the outer and the inner surfaces of the hollow cylinder are considered to be traction free, no change in voids volume fraction and thermally insulated/isothermal temperature field. The analytical results for frequency equations are presented and validated with existing literature. To explore the free vibration analysis from the considered boundary conditions, the numerical iteration method has been generated to create data by using MATLAB software tools. The obtained analytical results are represented graphically with the assistance of numerical computations and simulations in absence/presence of magnetic field for nonlocal/local thermoelastic materials. To verify the elastic nonlocal effects in different models of thermoelasticity, the field functions are represented graphically with and without magnetic field effects. The study may find applications in the field of seismology for drilling and mining in the earth's crust appliances, lightweight armors, geophysics, acoustics, and oil prospecting etc.

Influence of Structural Parameters on the Buckling of Longitudinal Steel Bar in RC Structural Wall

Abstract: Reinforced Concrete (RC) structural wall is widely used in multistoried RC frame buildings to enhance lateral stiffness and lateral strength for earthquake resistance. One of the possible failure modes, observed during strong earthquake shaking, is the buckling of longitudinal steel reinforcement in the boundary elements of the wall. This also assumes importance in establishing damage states for seismic fragility analysis of RC wall. Although a few past studies have focussed on longitudinal bar buckling in RC members, detailed parametric study is absent particularly for such instability of bars in the boundary elements of the wall. In the present study, displacement-controlled nonlinear static analysis of several wall specimens is carried out using fibre-discretization of cross-section and distributed plasticity modelling in OpenSEES. Here, 27 different models of the isolated slender wall are created considering variations in six structural parameters, namely (a) length ratio of the boundary element to the wall, (b) axial force ratio, ratios of (c) longitudinal steel in web, and (d) transverse steel and (e) longitudinal steel in the boundary elements. The effect of wall thickness is accounted for through variation in axial force ratio. Using the analytical results from the nonlinear analysis of the wall models, the trends in drift ratio at the onset of longitudinal bar buckling damage states as functions of various key structural wall properties, has been investigated.

Reflection of temperature rate–dependent coupled thermoelastic waves on a non-local elastic half-space

Abstract: Based upon the Green–Lindsay (GL) theory of thermoelasticity and the Eringen non-local elasticity theory, we describe the new constitutive relations and the field equations for generalized non-local thermoelastic model. The propagation of harmonically time-dependent thermoelastic plane waves of assigned frequency is studied in a homogeneous, isotropic, non-local infinite elastic solid by employing these equations. Reflection phenomenon of thermoelastic waves at a stress-free thermally insulated or isothermal flat boundary of a non-local thermoelastic solid half-space is also studied in case of incident coupled longitudinal wave. The amplitude ratios of the reflected waves to that of incident wave are determined analytically and numerically by considering an appropriate material. The numerical results are presented graphically to highlight the effects of various parameters of interest.