The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Brian R. Mace - One of the best experts on this subject based on the ideXlab platform.
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A robust spot weld model for structural vibration analysis
Finite Elements in Analysis and Design, 2014Co-Authors: R. O. De Alba Alvarez, Neil Ferguson, Brian R. MaceAbstract:A finite element spot weld is proposed. The model is only weakly sensitive to element size, in contrast to some existing models, for which predictions of the static and dynamic responses can be strongly sensitive to the size of the elements in the substructures to which the spot weld is connected, to such an extent that numerical results may not converge. The proposed model comprises a number of Multipoint Constraint connections to the attached substructures, so that they may have incompatible meshes. It involves stiffness elements distributed around the perimeter of the spot weld. The case of two plates connected by three spot welds is considered. Numerical results are presented and compared with those of CWELD models and with experimental measurements. The results from the proposed spot weld model show good accuracy, low sensitivity to the element dimensions and good convergence properties.
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A robust spot weld model for structural vibration analysis
Finite Elements in Analysis and Design, 2014Co-Authors: R. O. De Alba Alvarez, Neil Ferguson, Brian R. MaceAbstract:A finite element spot weld is proposed. The model is only weakly sensitive to element size, in contrast to some existing models, for which predictions of the static and dynamic responses can be strongly sensitive to the size of the elements in the substructures to which the spot weld is connected, to such an extent that numerical results may not converge. The proposed model comprises a number of Multipoint Constraint connections to the attached substructures, so that they may have incompatible meshes. It involves stiffness elements distributed around the perimeter of the spot weld. The case of two plates connected by three spot welds is considered. Numerical results are presented and compared with those of CWELD models and with experimental measurements. The results from the proposed spot weld model show good accuracy, low sensitivity to the element dimensions and good convergence properties.
Amit Karmakar - One of the best experts on this subject based on the ideXlab platform.
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Free vibration characteristics of delaminated composite pretwisted stiffened cylindrical shell
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2017Co-Authors: Mrutyunjay Rout, Sasank Shekhara Hota, Amit KarmakarAbstract:Effects of delamination on free vibration characteristics of laminated stiffened cylindrical shells with pretwist are analyzed by finite element method. The investigation is carried out using an eight-noded quadratic isoparametric shell element, which incorporates the transverse shear deformation and rotary inertia along with a three-noded beam element for the stiffener. The Multipoint Constraint algorithm has been included to guarantee the compatibility of deformation, equilibrium of resultant forces, and moments at delamination crack tip. The general dynamic equilibrium equation is derived from Lagrange’s equation of motion for moderate rotational speeds for which the Coriolis effect is neglected. The standard eigenvalue problem is solved utilizing QR iteration algorithm. The accuracy of the present formulation is validated with benchmark solutions is available in the literature. The present work concerns about the effects of delamination, fiber orientation, twist angle, stiffener depth-to-shell thickne...
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Time dependent response of low velocity impact induced composite conical shells under multiple delamination
Mechanics of Time-Dependent Materials, 2014Co-Authors: Amit KarmakarAbstract:This paper presents the time dependent response of multiple delaminated angle-ply composite pretwisted conical shells subjected to low velocity normal impact. The finite element formulation is based on Mindlin’s theory incorporating rotary inertia and effects of transverse shear deformation. An eight-noded isoparametric plate bending element is employed to satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. A Multipoint Constraint algorithm is incorporated which leads to asymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark’s time integration algorithm. Parametric studies are conducted with respect to triggering parameters like laminate configuration, location of delamination, angle of twist, velocity of impactor, and impactor’s displacement for centrally impacted shells.
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Effect of Twist and Striker Velocity of Torsion Stiff Composite Conical Shells under Multiple Delaminations
Procedia Engineering, 2014Co-Authors: Sudip Dey, Saikat Das, Manoj Roy, Amit KarmakarAbstract:Abstract The low velocity impact response of torsion stiff composite pretwisted conical shells is portrayed in the present study. The formulation is based on Mindlin's theory incorporating rotary inertia and effects of transverse shear deformation. An eight noded isoparametric plate bending element is employed to satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. A Multipoint Constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. The modified Hertzian contact law is employed to simulate the contact force and the time dependent equations are solved by Newmark's time integration algorithm. Parametric studies are conducted with respect to triggering parameters like twist angle, target displacement, initial velocity of striker considering low velocity centrally impacted spherical mass.
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A comparative study on free vibration analysis of delaminated torsion stiff and bending stiff composite shells
Journal of Mechanical Science and Technology, 2013Co-Authors: Amit KarmakarAbstract:This paper presents a finite element method to compare the effects of delamination on free vibration of graphite-epoxy bending stiff and torsion stiff composite pretwisted shallow conical shells. The generalized dynamic equilibrium equation is derived from Lagrange’s equation of motion neglecting the Coriolis effect for moderate rotational speeds. An eight noded isoparametric plate bending element is employed incorporating rotary inertia and effects of transverse shear deformation based on Mindlin’s theory. The Multipoint Constraint algorithm is utilized to ensure the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The standard eigen value problem is solved by applying the QR iteration algorithm. Mode shapes for typical configurations are also depicted. Numerical results obtained are the first known non-dimensional frequencies which could serve as reference solutions for the future investigators.
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Free Vibration Characteristics of Multiple Delaminated Cross-ply Composite Conical Shells
International Journal for Computational Methods in Engineering Science and Mechanics, 2013Co-Authors: Sudip Dey, Amit KarmakarAbstract:This paper investigates the free vibration of multiple delaminated graphite-epoxy cross-ply composite pretwisted rotating conical shells. The generalized dynamic equilibrium equations are derived from Lagrange's equation, neglecting the Coriolis effect for moderate rotational speeds. The formulation is based on Mindlin's theory considering an eight-noded isoparametric plate-bending element. The Multipoint Constraint algorithm is employed and a QR iteration algorithm is utilized to solve the standard eigenvalue problem. The mode shapes for a typical laminate configuration are also depicted. Numerical results obtained are the first known value, which could serve as reference solutions for future investigators.
R. O. De Alba Alvarez - One of the best experts on this subject based on the ideXlab platform.
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A robust spot weld model for structural vibration analysis
Finite Elements in Analysis and Design, 2014Co-Authors: R. O. De Alba Alvarez, Neil Ferguson, Brian R. MaceAbstract:A finite element spot weld is proposed. The model is only weakly sensitive to element size, in contrast to some existing models, for which predictions of the static and dynamic responses can be strongly sensitive to the size of the elements in the substructures to which the spot weld is connected, to such an extent that numerical results may not converge. The proposed model comprises a number of Multipoint Constraint connections to the attached substructures, so that they may have incompatible meshes. It involves stiffness elements distributed around the perimeter of the spot weld. The case of two plates connected by three spot welds is considered. Numerical results are presented and compared with those of CWELD models and with experimental measurements. The results from the proposed spot weld model show good accuracy, low sensitivity to the element dimensions and good convergence properties.
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A robust spot weld model for structural vibration analysis
Finite Elements in Analysis and Design, 2014Co-Authors: R. O. De Alba Alvarez, Neil Ferguson, Brian R. MaceAbstract:A finite element spot weld is proposed. The model is only weakly sensitive to element size, in contrast to some existing models, for which predictions of the static and dynamic responses can be strongly sensitive to the size of the elements in the substructures to which the spot weld is connected, to such an extent that numerical results may not converge. The proposed model comprises a number of Multipoint Constraint connections to the attached substructures, so that they may have incompatible meshes. It involves stiffness elements distributed around the perimeter of the spot weld. The case of two plates connected by three spot welds is considered. Numerical results are presented and compared with those of CWELD models and with experimental measurements. The results from the proposed spot weld model show good accuracy, low sensitivity to the element dimensions and good convergence properties.
Neil Ferguson - One of the best experts on this subject based on the ideXlab platform.
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A robust spot weld model for structural vibration analysis
Finite Elements in Analysis and Design, 2014Co-Authors: R. O. De Alba Alvarez, Neil Ferguson, Brian R. MaceAbstract:A finite element spot weld is proposed. The model is only weakly sensitive to element size, in contrast to some existing models, for which predictions of the static and dynamic responses can be strongly sensitive to the size of the elements in the substructures to which the spot weld is connected, to such an extent that numerical results may not converge. The proposed model comprises a number of Multipoint Constraint connections to the attached substructures, so that they may have incompatible meshes. It involves stiffness elements distributed around the perimeter of the spot weld. The case of two plates connected by three spot welds is considered. Numerical results are presented and compared with those of CWELD models and with experimental measurements. The results from the proposed spot weld model show good accuracy, low sensitivity to the element dimensions and good convergence properties.
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A robust spot weld model for structural vibration analysis
Finite Elements in Analysis and Design, 2014Co-Authors: R. O. De Alba Alvarez, Neil Ferguson, Brian R. MaceAbstract:A finite element spot weld is proposed. The model is only weakly sensitive to element size, in contrast to some existing models, for which predictions of the static and dynamic responses can be strongly sensitive to the size of the elements in the substructures to which the spot weld is connected, to such an extent that numerical results may not converge. The proposed model comprises a number of Multipoint Constraint connections to the attached substructures, so that they may have incompatible meshes. It involves stiffness elements distributed around the perimeter of the spot weld. The case of two plates connected by three spot welds is considered. Numerical results are presented and compared with those of CWELD models and with experimental measurements. The results from the proposed spot weld model show good accuracy, low sensitivity to the element dimensions and good convergence properties.
Kikuo Kishimoto - One of the best experts on this subject based on the ideXlab platform.
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Free Vibration Analysis of Delaminated Composite Pretwisted Rotating Shells : A Finite Element Approach
JSME International Journal Series A, 2006Co-Authors: Amit Karmakar, Kikuo KishimotoAbstract:In this paper a finite element method is presented to study the effects of delamination on free vibration characteristics of graphite-epoxy composite pretwisted rotating shells. Lagrange’s equation of motion is used to derive the dynamic equilibrium equation and moderate rotational speeds are considered wherein the Coriolis effect is negligible. An eight noded isoparametric plate bending element is employed in the formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin’s theory. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front, a Multipoint Constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. Parametric studies are performed in respect of location of delamination, fibre orientation, rotational speed and twist angle on natural frequencies of cylindrical shallow shells. Numerical results obtained for symmetric and unsymmetric laminates are the first known non-dimensional frequencies for the analyses carried out here.
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Transient dynamic response of delaminated composite rotating shallow shells subjected to impact
Shock and Vibration, 2006Co-Authors: Amit Karmakar, Kikuo KishimotoAbstract:In this paper a transient dynamic finite element analysis is presented to study the response of delaminated composite pretwisted rotating shallow shells subjected to low velocity normal impact. Lagrange's equation of motion is used to derive the dynamic equilibrium equation and moderate rotational speeds are considered wherein the Coriolis effect is negligible. An eight noded isoparametric plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin's theory. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front a Multipoint Constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark's time integration algorithm. Parametric studies are performed in respect of location of delamination, angle of twist and rotational speed for centrally impacted graphite-epoxy composite cylindrical shells.
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Transient Dynamic Response of Delaminated Composite Twisted Cylindrical Shells Subjected to Low Velocity Impact
Key Engineering Materials, 2005Co-Authors: Amit Karmakar, Kikuo KishimotoAbstract:In this paper a transient dynamic finite element analysis is presented to study the response of centrally impacted delaminated composite pretwisted cylindrical shells. An eight noded isoparametric plate bending element is employed in the finite element formulation. Effects of transverse shear deformation and rotary inertia are included. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front a Multipoint Constraint algorithm is incorporated. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark’s time integration algorithm. Parametric studies are performed in respect of relative size of delamination and angle of twist for graphite-epoxy composite cylindrical shallow shells subjected to low velocity normal impact.
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Free vibration analysis of delaminated composite pretwisted shells
Aircraft Engineering and Aerospace Technology, 2005Co-Authors: Amit Karmakar, H. Roy, Kikuo KishimotoAbstract:Purpose – To investigate the effects of delamination on free vibration characteristics of graphite‐epoxy composite pretwisted cylindrical shallow shells of various stacking sequences considering length of delamination as a parameter.Design/methodology/approach – A Multipoint Constraint algorithm which leads to unsymmetric elastic stiffness matrix is incorporated into an eight noded isoparametric plate bending finite element to satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The study is focused upon long, intermediate and short cylindrical shells as defined by Aas‐Jakobsen's parameters and considers symmetric and unsymmetric composite laminates.Findings – The non‐dimensional fundamental natural frequencies are obtained for angle ply (45/−45/45, 45/−45) and cross ply (0/90/0, 0/90) configurations corresponding to different crack lengths and twist angles. The study implies the importance of the symmetric laminate as well as the long s...
