BITS Faculty Publications

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Author: search.filters.author.Watts, GauravSubject: search.filters.subject.Mechanical Engineering

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    Effect of Cutout on the Stability and Failure of Laminated Composite Cylindrical Panels Subjected to In-Plane Pulse Loads
    (World Scientific, 2022) Watts, Gaurav; Kumar, Rajesh; Patel, Shuvendu Narayan
    In this investigation, the nonlinear dynamic buckling analysis and the failure analysis of laminated composite cylindrical (LCC) panel with different shapes of cutouts under the action of rectangular in-plane pulse loads are performed in the finite element framework. Cross-ply laminates which are balanced symmetric are considered in the investigation. The first ply failure load (FPFL) of the panel is evaluated and checked whether it occurs before the nonlinear dynamic buckling phenomenon considering Tsai–Wu failure criterion. Convergence and validation studies are undertaken, and the results are compared with those from the existing literature. The effects of loading duration, cutout area and cutout geometry on the panel are investigated in detail and results are reported. The results indicate that for the panel with cutout, its dynamic buckling load (DBL), in certain cases, compared to the static buckling load (SBL), can be lower even if the loading duration is half of its first natural period. Additionally, the vibration and the static buckling analyses of the panels are carried out as and when required.
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    Effect of Cutout on the Stability and Failure of Laminated Composite Cylindrical Panels Subjected to In-Plane Pulse Loads
    (World Scientific, 2022) Patel, S. N.; Kumar, Rajesh; Watts, Gaurav
    In this investigation, the nonlinear dynamic buckling analysis and the failure analysis of laminated composite cylindrical (LCC) panel with different shapes of cutouts under the action of rectangular in-plane pulse loads are performed in the finite element framework. Cross-ply laminates which are balanced symmetric are considered in the investigation. The first ply failure load (FPFL) of the panel is evaluated and checked whether it occurs before the nonlinear dynamic buckling phenomenon considering Tsai–Wu failure criterion. Convergence and validation studies are undertaken, and the results are compared with those from the existing literature. The effects of loading duration, cutout area and cutout geometry on the panel are investigated in detail and results are reported. The results indicate that for the panel with cutout, its dynamic buckling load (DBL), in certain cases, compared to the static buckling load (SBL), can be lower even if the loading duration is half of its first natural period. Additionally, the vibration and the static buckling analyses of the panels are carried out as and when required.
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    Nonlinear dynamic instability of laminated composite stiffened plates subjected to in-plane pulsating loading
    (Taylor & Francis, 2023-06) Patel, Shuvendu Narayan; Watts, Gaurav; Kumar, Rajesh
    A nonlinear finite element dynamic instability analysis of laminated composite stiffened plates subjected to in-plane harmonic edge loading is presented in this article along with the linear and nonlinear dynamic response study. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the stiffened plates. Bolotin method is applied to analyze the dynamic instability regions in linear case. Incremental Harmonic Balance (IHB) method is applied to solve the nonlinear frequency response equations and Newmark-β method is used to solve the linear and nonlinear time history response equations.
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    Size-Dependent Nonlinear Free and Forced Vibration Analyses of a Functionally Graded Microplate Subjected to Transverse Patch Loading
    (ASCE, 2023) Kumar, Rajesh; Watts, Gaurav
    This paper presents a semianalytical methodology for the nonlinear vibration of a functionally graded microplate under transverse patch loadings. The higher-order shear deformation theory (HSDT) is combined with the modified strain gradient theory (MSGT) to model the microplate. The power-law function is used to model the functionally graded material. Hamilton’s principle is used to obtain the governing partial differential equations of motion, which are then solved using Galerkin’s method. The nonlinear free and forced vibration responses are obtained using the incremental harmonic balance (IHB) method, where the incremental part is performed using the arc-length continuation methods. The dependence of the steady-state amplitude on the amplitude of initial perturbation is studied using time history plots. These are plotted using the Newmark-β method. The effects of various parameters such as the power-law index, thickness of plate, thickness to material length scale parameter ratio, damping coefficient, different boundary conditions, and different positions of patch loading and its concentrations on the nonlinear free and forced vibration characteristics are examined in detail.
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    Postbuckled vibration behaviour of skew sandwich plates with metal foam core under arbitrary edge compressive loads using isogeometric approach
    (Elsevier, 2023-03) Watts, Gaurav; Kumar, Rajesh
    In the present work, nonuniform rational B-spline (NURBS) based isogeometric formulation in conjunction with refined higher-order theory is used to investigate the linear buckling, post-buckling, and post-buckled vibration behaviour of initially imperfect skew sandwich plates. The face sheets are functionally graded carbon nanotube-reinforced composite (FGCNTRC), and the core layer is made up of aluminium foam. The effects of three types of CNT distributions (uniform, FGX and FGO) in the face sheets, two types (uniform, symmetric) of porosity distribution functions for the core layer and five types of in-plane compressive loads are examined in the present investigation. The pre-buckling stresses are calculated using static analysis to evaluate accurate, critical loads. The post-buckling paths are traced using the modified Riks method. The accuracy of the present results is ascertained by comparing the results for critical loads and post-buckling paths with those available in the literature. Subsequently, the influence of CNT distribution functions, porosity functions, compressive loads, skew angle and the side-to-thickness ratio is studied on the nonlinear stability and free vibration behaviour of the post-buckled skew sandwich plates. The obtained results highlight that the buckling strength can be improved by increasing the skew angle, increasing the concentration of CNTs towards the surface of the face sheets and by using a metal foam core with nonuniform porosity distribution.
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    Postbuckling and postbuckled vibration behaviour of imperfect trapezoidal sandwich plates with FG-CNTRC face sheets under nonuniform loadings
    (Elsevier, 2022-08) Kumar, Rajesh; Watts, Gaurav; Patel, Shuvendu Narayan
    The present work investigates the postbuckling, and postbuckled vibration behaviour of initially imperfect trapezoidal sandwich plates with functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets and FG porous metal foam core under the influence of non-uniform edge compression. The plate's kinematic assumptions are based on a refined higher order theory and the strain-displacement relations include von Karman assumptions for geometrical nonlinearity. The weak form of governing equations derived using Hamilton's principle is transformed into a discretized form of algebraic equations using the element free Galerkin (EFG) method in conjunction with moving kriging (MK) interpolation functions. The pre-buckling stresses are determined using static analysis to evaluate accurate critical buckling loads. Modified Riks technique is used to trace nonlinear equilibrium paths. Parametric studies include the effect of CNT distribution in face sheets, porosity distribution in the core layer and edge loading conditions on the nonlinear stability and vibration behaviour of sandwich plates. New results on trapezoidal sandwich plates with initial imperfections, hitherto not found in the literature, are presented for the first time, which can be used as benchmark solutions for further research.
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    Nonlinear bending analysis of isotropic plates supported on Winkler foundation using element free Galerkin method
    (Elsevier, 2014) Watts, Gaurav
    In the present work, constraint effects on growth curves of a mode-I crack are determined using a triaxiality dependent cohesive model. Plane strain elastic-plastic analysis based on the modified boundary layer formulation is performed and for modeling the fracture process, the cohesive parameters and the mechanical properties for a mild steel are taken from literature. From the analysis, the resistance curves for a range of constraint parameter are obtained. A discussion is developed on the effectiveness of the triaxiality dependent model in capturing the well-known effect of constraint and also on the effect of the two model parameters on the resistance curves.
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    Elastic Properties and Nonlinear Elasticity of the Noncarbon Hexagonal Lattice Nanomaterials Based on the Multiscale Modeling
    (ASME, 2021-04) Watts, Gaurav
    This study presents the elastic properties and nonlinear elasticity of the two-dimensional noncarbon nanomaterials of hexagonal lattice structures having molecular structure XY. Four nitride-based and two phosphide-based two-dimensional nanomaterials, having graphene-like hexagonal lattice structure, are considered in the present study. The four empirical parameters associated with the attractive and repulsive terms of the Tersoff–Brenner potential are calibrated for noncarbon nanomaterials and tested for elastic properties, nonlinear constitutive behavior, bending modulus, bending and torsional energy. The mathematical identities for the tangent constitutive matrix in terms of the interatomic potential function are derived through an atomistic–continuum coupled multiscale framework of the extended version of Cauchy–Born rule. The results obtained using newly calibrated empirical parameters for cohesive energy, bond length, elastic properties, and bending rigidity are compared with those reported in the literature through experimental investigations and quantum mechanical calculations. The continuum approximation is attained through the finite element method. Multiscale evaluations for elastic properties and nonlinear stretching of the nanosheets under in-plane loads are also compared with those obtained from atomistic simulations.
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    An analytical solution for the static bending of smart laminated composite and functionally graded plates with and without porosity
    (Springer, 2022-02) Watts, Gaurav
    In this paper, an analytical solution for smart laminated composite and functionally graded material plates with and without through-thickness porosity is presented. The kinematics of the deformation in smart structures is modelled through the newly proposed five non-polynomial higher-order shear deformation theories. The relative performance and accuracy of the different theories are assessed for the static bending response of the smart structures under a combined electromechanical loading. The proposed theories assume a nonlinear variation of the transverse shear strain through the thickness of the plate with transverse shear stress-free top and bottom surfaces. The governing differential equations of the plate derived through Hamilton’s principle are solved by Navier’s solution technique with simply supported boundary conditions. To demonstrate the accuracy and applicability of the proposed higher-order shear deformation theories, a wide range of numerical examples for static bending under mechanical and electrostatics loads are considered. The accuracy of the present theories is compared against the three-dimensional elasticity solution, and thereafter, several benchmark solutions for the functionally graded plates with and without porosity are reported.
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    A numerical study on the nonlinear behavior of corner supported flat and curved panels
    (Springer, 2017-11) Watts, Gaurav
    The nonlinear behavior of corner supported plates and curved shell panels is investigated here using the first-order shear deformation theory based on Marguerre’s membrane strains for shallow shells and von Kármán’s nonlinearity. The nonlinear differential equations are transformed into a set of nonlinear algebraic equations by using the element-free Galerkin method. The moving kriging shape function with two different types of correlation formulae (Gaussian and quartic spline) is employed here. After studying the effectiveness of the method, a detailed parametric study is conducted to examine the effect of support size on the displacements and bending moments of corner supported rectangular plates. Thereafter, the numerical study is extended to the nonlinear bending and stability behaviors of corner supported shallow cylindrical and spherical shell panels.