Showing papers by "Subrata Kumar Panda published in 2021"

Numerical investigation of thermal frequency responses of graded hybrid smart nanocomposite (CNT-SMA-Epoxy) structure

Abstract: Thermal frequency of the graded nanotube-reinforced composite structure embedded with shape memory alloy (SMA) fiber has been computed first time numerically using a micromechanical multiscale fini...

Free Vibrational Behaviour of Multi-Directional Porous Functionally Graded Structures

Abstract: The free vibrational frequencies of a multi-directional functionally graded (FG) structure are investigated for the first time in this paper considering the influences of variable grading (power-law, sigmoid, exponential) and porosity distribution (even and uneven type). Also, the structural properties (Young’s modulus, density and Poisson's ratio) varied along with two different directions simultaneously, i.e., the longitudinal and transversional ones, respectively. The present multi-directional grading model of the FG structure is reconstructed mathematically for the numerical analysis by considering adequate state-space deformation kinematics with the help of higher-order displacement functions and shear stress continuity. The general motion equation of a multi-graded structure is expressed using Hamilton’s principle and the finite element method including the necessary porosity effect. Initially, model consistency is verified and the eigenvalues obtained in the analysis are compared with the ones found in the literature. The comparison also includes the directional grading effect on their frequencies. Further, the influence of different parameters, i.e., power exponents (nz and nx), aspect ratio, thickness ratio, geometry, end support conditions, curvature ratio, porosity index, porosity distribution and material grading patterns, on the vibration characteristics of the multi-directional FG structure is computed. The analysis of the numerical results confirms that material grading; porosity distribution pattern and other design parameters have a significant influence on the frequency response characteristics of a single/multi-directional porous FG structure.

Thermal Post-Buckling Strength Prediction and Improvement of Shape Memory Alloy Bonded Carbon Nanotube-Reinforced Shallow Shell Panel: A Nonlinear Finite Element Micromechanical Approach

Abstract: This article reported first-time the post-buckling temperature load parameter values of nanotube-reinforced polymeric composite panel and their improvement by introducing the functional material (shape memory alloy, SMA) fiber. The temperature load values of nanotube composite and SMA activation are modeled using the single-layer type higher-order kinematic model in association with isoparametric finite element technique. To ensure the effective properties of SMA bonded nanotube composite under the elevated temperature, a hybrid micromechanical material modeling approach is adopted (Mori–Tanaka scheme and rule of mixture). The present structural geometry distortion under elevated temperature is modeled through the nonlinear strain kinematics (Green–Lagrange), whereas the strain reversal achieved with the help of marching technique (inclusion of material nonlinearity). Owing to the importance of geometrical distortion of the polymeric structure, the current model includes all of the nonlinear strain terms to accomplish the exact deformation. Further, to compute the post-buckling responses, the governing nonlinear eigenvalue equations are derived by Hamilton's principle. The numerical solution accuracy is verified with adequate confirmation of model consistency. The material model applicability for different structural configurations including important individual/combined parameter tested through a series of examples. Moreover, the final understanding relevant to the post-buckling characteristics of the polymeric structure and SMA influences is highlighted in details considering the prestrain, recovery stress, and their volume fractions.

Thermal buckling strength of smart nanotube-reinforced doubly curved hybrid composite panels

Abstract: The eigenvalue buckling responses of smart carbon nanotube-reinforced hybrid composite shell structure are analyzed under the influence of uniform thermal loading using a multiscale material model. The hybrid nanotube shell structural model is formulated mathematically via a cubic-order shear deformation theory introducing the material nonlinearity due to the shape memory alloy fiber. Additionally, the nanotube-reinforced composite properties are evaluated via two material modeling techniques (Mori–Tanaka technique and rule of mixture) considering the variable scale effect due to hybridization. The final form of the eigenvalue buckling equation is obtained via Hamilton’s principle (a dynamic version of the variational technique) including the temperature-dependent properties and thermal loading. The structural model is derived considering the distortion due to the in-plane thermal loading via the generic type of strain kinematics, i.e. Green–Lagrange nonlinearity. The thermal load values are predicted further by solving the derived eigenvalue equation using a nine-node isoparametric quadrilateral element from the finite element technique. The novelty of this research is that first time the shape memory alloy type functional material has been introduced with nanotube-reinforced composite shell structure to highlight the shape memory effect on the improvement of thermal buckling temperature. The derived numerical model is engaged further to solve varieties of examples for comprehensive testing (accuracy and reliability). Finally, a series of parametric analyzes has been performed for different design considerations associated with geometry as well as the material to show the model applicability.

Nonlinear free vibration analysis of composite conical shell panel with cluster of delamination in hygrothermal environment

Abstract: The nonlinear eigenvalue responses of conical composite shell structure with cluster of multiple delaminations are investigated numerically using the displacement-type finite element technique including the influence of the moisture and elevated thermal environment. The governing equation for the free vibrated structure case of the layered conical panel is obtained through a generalization of the principle of virtual displacement. The numerical solutions are obtained through a customized computer code developed via the higher order displacement field model imposing the zero stresses at the top and bottom surfaces of the laminate. The panel model has been discretized using an eight-nodded isoparametric element to maintain the desired C0 continuity and to avoid the mathematical complexity involved in C1-type continuity. A delamination model is developed by accounting single and cluster of delaminations. The delamination is located at centre of the laminates, either in cluster form or segregated over the lamina. The model is developed by considering the laminate is exposed to elevated moisture and temperature environment. The contribution of moisture and temperature effects on delaminated lamina is examined. The solution methodology is validated with published results. Influence of various parameters such as lamination schemes, aspect ratios, support conditions, thickness ratios, curvature ratios and material properties of the linear and nonlinear free vibration frequencies are analysed in detail and presented. The inferences from the study signify the reduction trend of fundamental frequency due to the presence of single/multi-delamination and moisture content.

Multidirectional grading influence on static/dynamic deflection and stress responses of porous FG panel structure: a micromechanical approach

Abstract: This is the first time the multidirectional-graded porous panel structure modeled numerically using an equivalent single-layer higher-order polynomial model considering the cubic variation of extensional displacement to maintain the necessary stress/strain. The effect of porosity (even and uneven distributions) and variable grading patterns also included achieving the generality. Further, the deflection and stress values, the proposed bidirectional functionally graded (2D-FG) structure, are predicted under the variable loadings, i.e. static and dynamic. Three different types of grading pattern, i.e. power-law, exponential and sigmoid are introduced by varying the material constituents along their principal material axes (longitudinal and transverse). The current numerical solutions (deflection and stress) are obtained through a customized computer code (prepared in MATLAB), under the influences of the static and time-dependent loadings utilizing the higher-order finite element formulations. The dynamic deflections are obtained through the constant acceleration type Newmark’s time-integration steps. The predicted result accuracy is checked by comparing the previously published values in literature and different simulation models (ANSYS and ABAQUS). Besides, the batch input technique is adopted for the simulation material models for both the ANSYS and ABAQUS. Moreover, the python scripting is adopted first time to modify ABAQUS input files for the present 2D graded structure. The influential structure input parameter (power-law exponents, thickness ratio, aspect ratio, end conditions, geometry and curvature ratio) is varied to compute a few final responses (deflection and stress data) of multidirectional FG structure via the derived mathematical model and the final understandings listed the details.

Numerical Nonlinear Static Analysis of Cutout-Borne Multilayered Structures and Experimental Validation

Abstract: The influence of two different types of nonlinear strain-displacement kinematics (Green–Lagrange and von Karman) and their importance are investigated in this analysis by computing the static defle...

Optimal deflection and stacking sequence prediction of curved composite structure using hybrid (FEM and soft computing) technique

Abstract: The bending deflections and the corresponding optimal fiber angle sequences of the subsequent layers have been predicted in this article using a hybrid technique. The structural static responses are computed numerically via the isoparametric finite element steps in association with Reddy’s higher order mid-plane theory. The final stacking sequences of individual layers are further predicted through two types of soft computing techniques (particle swarm optimization, PSO; teaching–learning-based optimization, TLBO). The responses (deflection and optimal angle) are obtained via a customized computer code (MATLAB) using the current mathematical model in association with two different optimization algorithms. The accuracy of the currently derived higher order hybrid model is established by conducting a few numerical experimentations. The study indicates the superiority of TLBO technique over PSO for any particular problem when compared to the minimum deflection constraint whereas not many deviations for stacking sequences. Finally, the influences of the different structural parameter are explored by solving a variety of numerical examples and the corresponding inferences provided in detail.

Numerical transient responses of cut-out borne composite panel and experimental validity:

Abstract: The effect of cut-out parameters (shapes: square and circular; position: concentric/eccentric) on the dynamic deflection values of the curved/flat layered composite panel are verified experimentall...

Thermal frequency analysis of FG sandwich structure under variable temperature loading

Abstract: The thermal eigenvalue responses of the graded sandwich shell structure are evaluated numerically under the variable thermal loadings considering the temperature-dependent properties. The polynomial type rule-based sandwich panel model is derived using higher-order type kinematics considering the shear deformation in the framework of the equivalent single-layer theory. The frequency values are computed through an own home-made computer code (MATLAB environment) prepared using the finite element type higher-order formulation. The sandwich face-sheets and the metal core are discretized via isoparametric quadrilateral Lagrangian element. The model convergence is checked by solving the similar type published numerical examples in the open domain and extended for the comparison of natural frequencies to have the final confirmation of the model accuracy. Also, the influence of each variable structural parameter, i.e. the curvature ratios, core-face thickness ratios, end-support conditions, the power-law indices and sandwich types (symmetrical and unsymmetrical) on the thermal frequencies of FG sandwich curved shell panel model. The solutions are helping to bring out the necessary influence of one or more parameters on the frequencies. The effects of individual and the combined parameters as well as the temperature profiles (uniform, linear and nonlinear) are examined through several numerical examples, which affect the structural strength/stiffness values. The present study may help in designing the future graded structures which are under the influence of the variable temperature loading.

Influence of debonding on nonlinear deflection responses of curved composite panel structure under hygro-thermo-mechanical loading–macro-mechanical FE approach

Abstract: The excess geometrical deformation due to the in-plane hygrothermal and transverse mechanical loading are computationally (through a customized MATLAB code) obtained for the weakly bonded structure using the different kinematic theories in combination with the finite element steps. To evaluate the nonlinear deflection data a macro mechanical model is prepared mathematically considering the stretching effect (through the thickness), as well as the constant functions of displacement. The model includes the variation of composite properties due to the change in environmental temperature and moisture content including the necessary continuity assumptions between the separated layers for the weak bonding. The role of delamination i.e. location, position and size on the nonlinear deflection parameters are also computed under the combined loading (Hygral/Thermal/Mechanical/Hygro-Thermo-Mechanical). The solution accuracy and the elemental sensitivity have been computed for the proposed macro mechanical finite element model. Moreover, a set of numerical examples are solved to show the environmental effect on the flexural strength of a weakly bonded composite panel including the design-dependent parameters. The final results are indicating the necessity of the various kinematic model for the analysis of laminated structure with/without hygrothermal loading as well as the debonding.

Thermal post-buckling analysis of graded sandwich curved structures under variable thermal loadings

Abstract: In the present research, finite element solutions of thermal post-buckling load-bearing strength of functionally graded (FG) sandwich shell structures are reported by adopting a higher-order shear deformation type kinematics. For the numerical calculation, nine nodes are considered for each element. A specialized MATLAB code is developed incorporating the present mathematical model to evaluate the numerical buckling temperature. The Green–Lagrange nonlinear strain is adopted for the formulation of the sandwich structure. The eigenvalue equation of the FG sandwich structure is solved to predict the post-buckling temperature values of the structure. Moreover, three kinds of temperature distributions across the panel thickness are assumed, viz., uniform, linear and nonlinear. In addition, the properties are described using the power law distributions. The numerical solutions are first validated and, subsequently, the impact of alterations of structural parameters, viz., the curvature ratios, core–face thickness ratios, support conditions and power law index (nZ) including the amplitude ratio on the thermal post-buckling response of FG sandwich curved panels have been studied in details. The investigation reveals different interesting outcomes, which may help for future references for the analysis and design of the graded sandwich structure.

Multiphysics Hemodynamic Behavior of Polylactic Acid-Based Stent: A Coupled Simulation Approach

Abstract: This study investigates the structural and hemodynamic behavior of bioresorbable polylactic acid (PLA)-based stent designs for applications in treating coronary artery disease. Three stent designs were chosen and their geometry was modeled in SolidWorks and appropriate meshing was done before importing into the finite element analysis platform (ANSYS). The behavior of the stent designs was analyzed for structural loading conditions equivalent to human arterial blood pressure and similarly, the hemodynamic analysis was carried out under conditions simulating the blood flow. The stent porosity, structural stresses, wall shear stresses (WSS) and the velocity were analyzed, and the results from this multiphysics analysis show that the stresses occurring in the modified cordis stent (MCS) design present a maximum von Mises stress (273.01 MPa). Besides, the maximum WSS of 12.67 Pa is obtained from the hemodynamic flow analysis. The current findings are in the line of literature data for the possible usage of PLA as stent materials that pose a reduced risk of restenosis.

Dynamic deflection responses of glass/epoxy hybrid composite structure filled with hollow-glass microbeads

Abstract: The dynamic deflection characteristics of the hybrid composite structure (hollow-glass microsphere and multi-layer glass/epoxy composite) were computed numerically using in-house MATLAB code and verified with experimental results. The physical hybrid structural model is derived in the framework of equivalent higher-order single-layer kinematic theory considering the continuity of inter-laminar shear stresses to imitate the actual deformation behavior. The solutions are computed through the computer code prepared in MATLAB in conjunction with the prepared mathematical model. The model stability and accuracy have been verified by comparing the present results with the available benchmark solutions. Additionally, the hybrid multi-layered composite panel is fabricated by taking different volume fractions of the hollow-glass microsphere and the composite properties recorded from the experimental test for the subsequent utilization. Furthermore, the experimental transient data are compared with the finite element solutions to show the model adequacy. Finally, a few primary input parameters affecting the structural stiffness and the related design aspect, including the geometrical configuration efficacy, have been explored using the currently developed finite element model.

Implementation of Multiple Regression Technique for Detection of Gait Asymmetry Using Experimental Gait Data

Abstract: This study reports the implementation of different regression (multivariate and step-wise) techniques towards determining the gait asymmetry and comparison with the symmetry indices (SI) values. To predict the gait asymmetry between two different legs, a set of gait trials (thirty-five participants) via a three-dimensional motion capture setup and force platform available at the parent institute, has been acquired. Two separate regression fit models are prepared to indicate the significant gait parameters for the right and left legs utilizing the recorded foot data. The significant sets of coefficients for the right and left leg parameters are compared with the SI values to validate the gait asymmetry. The calculated mean SI from the experimental results correspond to the predicted regression model responses, and 18 of the 27 regression fits present different sets of significant coefficients for the right and left leg parameters. The regression fits show gait parameter dependency on the different sets of predictor variables. The method can be adopted for different patient data sets to detect the influence of the causative factors on pathologic gait.

Creep behavior of Nickel–Titanium shape-memory alloys under static and dynamic loadings: an FEM approach

Abstract: The shape-memory effect and superelasticity properties of NiTinol alloys make them a versatile candidate for various engineering and biomedical applications. The use of these alloys as biomedical implants necessitates the study of any long-term creep failure possibility. The present study utilizes the finite element method to investigate this creep behavior of NiTinol alloys under static and dynamic loading conditions over a long period. The Maxwell creep model has been implemented, as well as validated with the polypropylene and low-density polyethylene. Further, the same model has been utilized for the creep analysis of NiTinol with suitable material properties and assumptions, for a time of 10,000 h. The results demonstrated the application of sinusoidal varying loads, the creep strain observed was lower as compared to other loading conditions, and in the case of static load, higher creep strain values were experienced than that of the dynamic smooth step loading case.

Experimental verification of multi-fibre hybridization influence on dynamic deflection and stress values of curved composite panel:

Abstract: The finite-element time-dependent deflection and stress responses of the shallow composite panels subjected to variable mechanical loadings (uniformly distributed load and sinusoidally distributed ...