Department of Civil Engineering

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Subject: search.filters.subject.Dynamic buckling

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    Nonlinear Dynamic Buckling and Failure Study of Laminated Composite Plates Subjected to Axial Impulse Loads
    (Springer, 2020-03) Patel, S. N.; Kumar, Rajesh
    In this paper, the nonlinear dynamic buckling of laminated composite plate is studied along with the failure of the plates. The balanced and symmetric cross-ply laminated composite plates are subjected to in-plane impulse compressive loads. The dynamic buckling load is calculated using Volmir’s criterion. The nonlinear dynamic equations are solved using the finite element method. Imperfections are incorporated in the plate in order to simulate the actual behavior. The effect of imperfection, loading function, and duration of loading is studied. The first ply failure load for the plate is calculated to check the precedence of dynamic buckling and first ply failure. It is observed that the first ply failure for balanced and symmetric cross-ply laminated composite plates occurs after the plate has buckled due to dynamic impulse loads.
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    Dynamic buckling analysis of a composite stiffened cylindrical shell
    (Korea Science, 2011) Patel, S. N.
    The paper investigates the dynamic buckling behaviour of a laminated composite stiffened cylindrical shell using the commercial finite element code ABAQUS. The numerical model of the composite shell is validated by static tests. In particular, the experimental collapse test is numerically simulated by a quasi static analysis carried out by both ABAQUS/Standard and ABAQUS/Explicit. The behaviour in the post-buckling field and the collapse load obtained by the analyses are close to the experimental data. The validated model is then used to study the dynamic buckling behaviour with ABAQUS/Explicit. The effects of the loading magnitude and of the loading duration are investigated, implementing in the analysis also first-ply failure criteria. It is observed that the dynamic buckling load is highly affected by the loading duration.
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    Stability and Failure Study of Suddenly Loaded Laminated Composite Cylindrical Panel
    (World Scientific, 2019) Patel, S. N.; Kumar, Rajesh
    In this paper, nonlinear dynamic buckling of laminated composite cylindrical panels subjected to in-plane impulsive compressive load is studied along with the failure analysis. Balanced and symmetric angle-ply laminated composite curved panels are considered. Convergence study is performed, and results are validated with the results from the existing literature, and then the dynamic buckling loads are calculated. The failure index of laminated composite curved panel is also calculated to check the precedence of first ply failure load over nonlinear dynamic buckling load. The effect of aspect ratio, loading function, and radius of curvature is studied. The analysis is carried out using finite element method. It is observed that the first ply failure for balanced and symmetric angle-ply laminated composite curved panels occurs after the panel has buckled due to dynamic impulse loads.
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    Non-Linear Stability and Failure of Laminated Composite Stiffened Cylindrical Panels Subjected to In-Plane Impulse Loading
    (Elsevier, 2021-02) Patel, S. N.; Kumar, Rajesh
    In this article, the non-linear dynamic buckling behavior and failure of laminated composite stiffened cylindrical (LCSC) panel is performed in the finite element framework when subjected to sinusoidal and rectangular in-plane pulse loading. Balanced symmetric cross-ply laminates and balanced symmetric angle ply laminates are considered in this study. The first ply failure load (FPFL) of the panel is evaluated and checked whether it occurs before the non-linear dynamic buckling phenomenon considering four different failure theories. Convergence and validation studies are carried out using the present mathematical formulation and compared with the results from the existing literatures. The effect of loading duration, loading function, aspect ratio of stiffener and the ply orientation of the skin and stiffener on the non-linear dynamic buckling of LCSC panel is studied in detail and the results are reported. It is observed that the non-linear dynamic buckling load (DBL) of balanced and symmetric angle ply (45°/−45°/−45°/45°) stiffened panel is lower than those of unstiffened composite cylindrical panel upto aspect ratio of the stiffener (ds/bs) equal to 8 when subjected to rectangular pulse load. In case of balanced and symmetric cross ply (0°/90°/90°/0°) stiffened panel the DBL of stiffened panel is lower than those of unstiffened panel when the aspect ratio of the stiffener is less than 4 with rectangular pulse load. Further, the free vibration, static buckling and static post-buckling analyses of the panels are carried out as and when required.
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    Non-linear response and buckling of imperfect laminated composite plates under in-plane pulse forces
    (Sage, 2021-05) Patel, S. N.; Kumar, Rajesh; Roy, Nishant 
    This study presents a semi-analytical solution of the non-linear dynamic response, shock spectrum, and dynamic buckling of an imperfect angle-ply laminated composite plate under various types of in-plane pulse forces. The laminated composite plate is modeled using a higher-order shear deformation theory and von-Kármán geometric nonlinearity. The non-linear governing partial differential equations (PDEs) of imperfect laminated composite plates are derived via Hamilton’s principle. Using Galerkin’s method, the non-linear PDEs are transformed into non-linear algebraic equations for the static stability problems and non-linear ordinary differential equations for the dynamic problem such as dynamic response, shock spectrum, and dynamic buckling. The buckling load of the plate is obtained through the associated eigenvalue problem. The static failure load of the composite plate is evaluated using the post-buckling analysis based on the Tsai-Wu failure criterion. The dynamic response and shock spectrum of the composite plate are determined via Newmark’s method. The dynamic failure load of the plate is evaluated using Newmark’s method based on the Tsai-Wu failure criterion. Dynamic buckling is to be characterized by dynamic load factor (DLF), which is represented as the ratio of the dynamic failure load to the static failure load. Based on the pulse/shock duration time, the pulse forces are divided into three loading regimes known as impulsive, dynamic, and quasi-static. The study revealed that the DLF values are > 1, < 1, and ≈1 respectively for the case of impulsive, dynamic, and quasi-static loading regimes of pulse force. The influences of various types of in-plane pulse forces, amplitude and time duration of pulse forces, and amplitude of initial geometric imperfections on the non-linear dynamic response, shock spectrum, and dynamic buckling behavior of the laminated composite plate are addressed in detail. The results will help in the appropriate design of the laminated composite plate against dynamic buckling.
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    Dynamic Buckling of Laminated Composite Curved Panels Subjected to In-plane Compression
    (Springer, 2018-08) Patel, S. N.
    This paper deals with dynamic buckling of laminated composite curved panels subjected to in-plane dynamic compressive loads. Results from the available literature are used to validate the static buckling load of curved panels, and the dynamic buckling loads of the same panel are predicted using finite element software ABAQUS/Explicit. Volmir’s criterion is used to find the dynamic buckling load. Dynamic load of various magnitudes in the form of pulse load is applied on the panel for various duration. The effect of aspect ratio and radius of curvature are studied. It is observed that smaller loads require longer duration of loading and vice versa for dynamic buckling to occur. The dynamic buckling load is observed to be lesser than static buckling load for longer duration of loading which is an important aspect to be considered in designing.
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    Non-Linear dynamic pulse buckling of laminated composite curved panels
    (TechnoPress, 2020-01) Patel, S. N.
     In this paper, non-linear dynamic buckling behaviour of laminated composite curved panels subjected to dynamic in-plane axial compressive loads is studied using finite element methods. The work is carried out using the finite element software ABAQUS. The curved panels are modelled with S4R element and the nonlinear dynamic equilibrium equations are solved using the ABAQUS/Explicit algorithm. The effect of aspect ratio, radius of curvature and thickness are studied. The importance of orientation of plies in the direction of loading is also reiterated in this study. Vol\'mir\'s criterion is used to calculate the dynamic buckling loads. The panels are subjected to rectangular pulse load of various amplitude and durations and the responses are observed. For particular loading amplitude, a critical value of loading duration is observed beyond which the variation of dynamic buckling load is insignificant. It is also observed that, the value of dynamic bucking load reduces as the loading duration is increased though the reduction is not much after a particular loading duration.
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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
    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.