The Experts below are selected from a list of 2604 Experts worldwide ranked by ideXlab platform
M Shariyat - One of the best experts on this subject based on the ideXlab platform.
-
Eccentric impact analysis of pre-stressed composite sandwich plates with viscoelastic cores: A novel global–local theory and a refined Contact Law
Composite Structures, 2014Co-Authors: M Shariyat, S H HosseiniAbstract:Abstract A novel double superposition power-exponential global–local theory and a refined Contact Law are developed to investigate eccentric low-velocity impact responses of rectangular sandwich plates with viscoelastic cores. The continuity conditions of the transverse normal and shear stresses at the interfaces between layers is satisfied a priori. Stiffness of the underneath layers is considered in the Contact Law as well, for the first time. The non-linear integro-differential governing equations are solved by a second-order finite element and a special numerical time integration procedure. Effects of the pre-stresses on the indentation and Contact force are investigated for the first time. Moreover, effects of the eccentricity on the impact responses of the sandwich plates are discussed in detail, for the first time. Verification of the results is accomplished through comparing present results with experimental results of a known reference. Results show that in the eccentric impacts, the Contact force and the absorbed energy increase. Therefore, the failure occurrence can be more likely in the eccentric impacts. Furthermore, by utilizing a viscoelastic core, the apparent stiffness of the Contact region increases and consequently the impact force and the absorbed energy increase. Biaxial tension increases the impact force and consequently, leads to premature failures.
-
eccentric impact analysis of pre stressed composite sandwich plates with viscoelastic cores a novel global local theory and a refined Contact Law
Composite Structures, 2014Co-Authors: M Shariyat, S H HosseiniAbstract:Abstract A novel double superposition power-exponential global–local theory and a refined Contact Law are developed to investigate eccentric low-velocity impact responses of rectangular sandwich plates with viscoelastic cores. The continuity conditions of the transverse normal and shear stresses at the interfaces between layers is satisfied a priori. Stiffness of the underneath layers is considered in the Contact Law as well, for the first time. The non-linear integro-differential governing equations are solved by a second-order finite element and a special numerical time integration procedure. Effects of the pre-stresses on the indentation and Contact force are investigated for the first time. Moreover, effects of the eccentricity on the impact responses of the sandwich plates are discussed in detail, for the first time. Verification of the results is accomplished through comparing present results with experimental results of a known reference. Results show that in the eccentric impacts, the Contact force and the absorbed energy increase. Therefore, the failure occurrence can be more likely in the eccentric impacts. Furthermore, by utilizing a viscoelastic core, the apparent stiffness of the Contact region increases and consequently the impact force and the absorbed energy increase. Biaxial tension increases the impact force and consequently, leads to premature failures.
-
nonlinear eccentric low velocity impact analysis of a highly prestressed fgm rectangular plate using a refined Contact Law
Archive of Applied Mechanics, 2013Co-Authors: M Shariyat, F FarzanAbstract:In the present paper, a nonlinear analysis is presented for response prediction of a low-velocity eccentric impact between a functionally graded rectangular plate and a rigid sphere or a projectile with a spherical nose. Some of the novelties of the present paper are (i) considering the more general case of eccentric impact, (ii) investigating effects of the initial in-plane loads on the impact responses of the functionally graded plates, especially for compressive loads that are comparable but not equal to the buckling loads, (iii) using a Contact Law that incorporates influences of the transverse variations of the material properties of the substrate layers and the plate thickness, and (iv) using nonlinear strain-displacement relations instead of using the traditional infinitesimal deformations assumption for assessment of influences of the initial preloads. Due to using von Karman strain-displacement relations and a nonlinear Contact Law, the governing equations are highly nonlinear. For this reason, an iterative solution scheme is employed. A sensitivity analysis is performed to investigate influences of the specifications of the plate and the indenter, the eccentric value, and the in-plane preloads on the indentation and force time histories. Results reveal that due to the resulting increase in the Contact force, slightly higher damages may be expected for impacted FGM plates subjected to initial compressive in-plane loads.
-
a variational iteration solution for elastic plastic impact of polymer clay nanocomposite plates with or without global lateral deflection employing an enhanced Contact Law
International Journal of Mechanical Sciences, 2013Co-Authors: M Shariyat, E A DarabiAbstract:Abstract In the present paper, characteristics of low/medium velocity impact responses of thin nanocomposite plates impacted by rigid spherical indenters are investigated. The plates may either have lateral deflections or resting on rigid substrates. It is obvious that for thin plates with transverse mobility subjected to impact with rigid indenters, the actual indentation value is much less than that predicted by the traditional Hertz-type Laws. A modified Contact Law that takes into account effects of the plate thickness and boundary conditions is employed in the present research. The variational iteration method is employed to develop a closed form semi-analytical solution. In comparison with the available numerical solution procedures, convergence of the present solution scheme is much higher and the solution algorithm converges unconditionally. Therefore, novelties may be found in the treated subject, modeling procedure, and solution algorithm. Comparisons made with results of the available numerical procedures, reveal the efficiency and accuracy of the presented solution algorithm.
-
A VARIATIONAL ITERATION SOLUTION FOR ELASTIC–PLASTIC IMPACT OF POLYMER/CLAY NANOCOMPOSITE PLATES WITH OR WITHOUT GLOBAL LATERAL DEFLECTION, EMPLOYING AN ENHANCED Contact Law
International Journal of Mechanical Sciences, 2013Co-Authors: M Shariyat, E A DarabiAbstract:Abstract In the present paper, characteristics of low/medium velocity impact responses of thin nanocomposite plates impacted by rigid spherical indenters are investigated. The plates may either have lateral deflections or resting on rigid substrates. It is obvious that for thin plates with transverse mobility subjected to impact with rigid indenters, the actual indentation value is much less than that predicted by the traditional Hertz-type Laws. A modified Contact Law that takes into account effects of the plate thickness and boundary conditions is employed in the present research. The variational iteration method is employed to develop a closed form semi-analytical solution. In comparison with the available numerical solution procedures, convergence of the present solution scheme is much higher and the solution algorithm converges unconditionally. Therefore, novelties may be found in the treated subject, modeling procedure, and solution algorithm. Comparisons made with results of the available numerical procedures, reveal the efficiency and accuracy of the presented solution algorithm.
S H Hosseini - One of the best experts on this subject based on the ideXlab platform.
-
eccentric impact analysis of pre stressed composite sandwich plates with viscoelastic cores a novel global local theory and a refined Contact Law
Composite Structures, 2014Co-Authors: M Shariyat, S H HosseiniAbstract:Abstract A novel double superposition power-exponential global–local theory and a refined Contact Law are developed to investigate eccentric low-velocity impact responses of rectangular sandwich plates with viscoelastic cores. The continuity conditions of the transverse normal and shear stresses at the interfaces between layers is satisfied a priori. Stiffness of the underneath layers is considered in the Contact Law as well, for the first time. The non-linear integro-differential governing equations are solved by a second-order finite element and a special numerical time integration procedure. Effects of the pre-stresses on the indentation and Contact force are investigated for the first time. Moreover, effects of the eccentricity on the impact responses of the sandwich plates are discussed in detail, for the first time. Verification of the results is accomplished through comparing present results with experimental results of a known reference. Results show that in the eccentric impacts, the Contact force and the absorbed energy increase. Therefore, the failure occurrence can be more likely in the eccentric impacts. Furthermore, by utilizing a viscoelastic core, the apparent stiffness of the Contact region increases and consequently the impact force and the absorbed energy increase. Biaxial tension increases the impact force and consequently, leads to premature failures.
-
Eccentric impact analysis of pre-stressed composite sandwich plates with viscoelastic cores: A novel global–local theory and a refined Contact Law
Composite Structures, 2014Co-Authors: M Shariyat, S H HosseiniAbstract:Abstract A novel double superposition power-exponential global–local theory and a refined Contact Law are developed to investigate eccentric low-velocity impact responses of rectangular sandwich plates with viscoelastic cores. The continuity conditions of the transverse normal and shear stresses at the interfaces between layers is satisfied a priori. Stiffness of the underneath layers is considered in the Contact Law as well, for the first time. The non-linear integro-differential governing equations are solved by a second-order finite element and a special numerical time integration procedure. Effects of the pre-stresses on the indentation and Contact force are investigated for the first time. Moreover, effects of the eccentricity on the impact responses of the sandwich plates are discussed in detail, for the first time. Verification of the results is accomplished through comparing present results with experimental results of a known reference. Results show that in the eccentric impacts, the Contact force and the absorbed energy increase. Therefore, the failure occurrence can be more likely in the eccentric impacts. Furthermore, by utilizing a viscoelastic core, the apparent stiffness of the Contact region increases and consequently the impact force and the absorbed energy increase. Biaxial tension increases the impact force and consequently, leads to premature failures.
Ik Hyeon Choi - One of the best experts on this subject based on the ideXlab platform.
-
Low-Velocity Impact Damage Prediction of Composite Laminates Using Linearized Contact Law
Key Engineering Materials, 2007Co-Authors: Ik Hyeon ChoiAbstract:Recently, author had presented that impact force history of composite laminates subjected to low-velocity impact could be well analyzed using linearized Contact Law instead of the modified Hertzian Contact Law. If the linearized Contact Law concept is applied in impact response analysis, the impact problem can be transformed as a general structural analysis problem, so general purpose FEM software can be used in this kind of impact response analysis. In the present study it will be shown that impact damage, specially delamination area, as well as impact response can be well analyzed using the linearized Contact Law concept. In order to accurately predict delamination area, geometrical nonlinear analysis considering large deflection effect of plate has been performed and thermal stress analysis to consider thermal residual strain induced in curing process has been performed. Also, a proper failure criterion for delamination estimation has been used. In this failure criterion, in-situ strength values, obtained through matrix crack onset analysis have been used. Finally, analytically predicted delamination areas have been compared with experimental results. It shows that this analytical procedure can well predict delamination area of composite laminates subjected to the low-velocity impact.
-
low velocity impact analysis of composite laminates using linearized Contact Law
Composite Structures, 2004Co-Authors: Ik Hyeon ChoiAbstract:Usually many researchers have used the modified Hertzian Contact Law or experimental static indentation Law to analyze impact response of composite laminates subjected to low-velocity impact. In this study, physical meaning of the analytical method using the Laws was investigated and the difference between the analytical results obtained using the two Laws was also investigated. Furthermore parametric study on Contact coefficient and exponent of the Contact Law was performed. Finally it could be shown that linearized Contact Law could be well applied to the low-velocity impact analysis of composite laminates. If this concept is used, any general-purpose finite element method software can be used to solve impact problem without direct developing any FEM code by each researcher. In this paper, some analytical results analyzed using a general-purpose commercial FEM software were also presented.
-
New approach for simple prediction of impact force history on composite laminates
AIAA Journal, 1994Co-Authors: Ik Hyeon Choi, Chang Sun HongAbstract:A new method for simple prediction of the impact force history on composite laminates subjected to low-velocity impact is proposed. First, the impact force history is calculated from the impact response analysis using the finite element method incorporated with the modified Hertzian Contact Law. Frequency characteristics of the numerical impact force history are investigated from modal analysis and compared with the natural frequencies of the system in which the mass of an impactor is lumped with the plate. The present method can be efficiently applied to isotropic or orthotropic plates with unknown Contact Laws as well as composite laminates with no restraint on the material properties and the geometrical shape
Andreas P Christoforou - One of the best experts on this subject based on the ideXlab platform.
-
analysis of low velocity impacts on sandwich composite plates using cubic spline layerwise theory and semi empirical Contact Law
Composite Structures, 2018Co-Authors: C S Rekatsinas, D K Siorikis, Andreas P Christoforou, Nikolaos A Chrysochoidis, Dimitris A SaravanosAbstract:Abstract The theoretical and numerical framework for the simulation of impacts on thick sandwich composite plates is presented. It encompasses three new elements: 1) A three-dimensional layerwise theory, which approximates the in-plane and transverse displacements through the thickness using third-order Hermite spline polynomials that captures the high inhomogeneity of all interlaminar stresses present in the thick sandwich laminate. 2) The integration of the layerwise theory into a time domain plate spectral finite element with nodes collocated to Gauss-Lobatto-Legendre integration points, which provides a consistent semi-diagonal mass matrix and high-order spatial approximation in the plane of the structure, thus enabling high spatial convergence and fast explicit time integration of impact events. 3) A semi-empirical Contact Law that is derived from analytical expressions and validated with indentation experiments and numerical results, to provide the coupling between the impactor and target structure. Numerical simulations of the transient impact response obtained by the present method are correlated with 3D continuum finite element impact models and experimental results to quantify accuracy and computational speed. It is demonstrated, that the simulation of impacted sandwich composite plates requires integration of all three previous elements to obtain accurate and fast results.
-
Transient response of a composite beam subject to elasto-plastic impact
Composites Engineering, 2008Co-Authors: Andreas P Christoforou, Ahmet S. YigitAbstract:Abstract An elastic-plastic Contact Law that includes the effect of permanent deformation in the Contact zone is used to study the transient response of a composite beam subject to impact. The governing differential equations are normalized to yield four nondimensional parameters which completely describe the impact event. A modal analysis procedure is used to spatially discretize the normalized boundary value problem to obtain a set of ordinary differential equations which are integrated numerically. Simulation results show that the local permanent deformations significantly affect the impact response. This indicates the importance of using an adequate Contact Law for an accurate prediction of the impact forces and strains during impact of composite structures.
-
The Efficacy of the Momentum Balance Method in Transverse Impact Problems
Journal of Vibration and Acoustics, 1998Co-Authors: Ahmet S. Yigit, Andreas P ChristoforouAbstract:An elastic-plastic Contact Law that incorporates local permanent deformation in the Contact zone has been used to investigate the efficacy of the momentum balance method in transverse impact problems. The momentum balance solution is compared to the numerical solution of the same equations rising the Contact Law. It is shown that the momentum balance method gives very good results for the post impact behavior of both the impacter and the beam. In certain cases, it is also shown to yield satisfactory results for the dynamic behavior during Contact. It is demonstrated that the momentum balance method with an appropriate coefficient of restitution obtained from the Contact Law, is physically the same as using the Contact Law itself with the difference that the local deformation is neglected.
-
Impact of Composite Structures--The Momentum Balance Method
Journal of Composite Materials, 1996Co-Authors: Andreas P Christoforou, A. S. YigitAbstract:The momentum balance method which is based on the impulse-momentum principle is used to study the transverse impact of a simply supported composite beam. In this method the effects of local Contact behavior is accounted for through the use of an appropriate coefficient of restitution obtained from an elastic-plastic Contact Law. This greatly simplifies the problem by decoupling the equations of motion, and for the problem studied, facilitates an analytical solution. The momentum balance solution is compared to the numerical solution of the same problem using the nonlinear elastic-plastic Contact Law. The proposed method gives very good results for the post impact behavior of both the impacter and the beam. In certain cases, it yields satisfactory results for the dynamic behavior even during Contact. The momentum balance method, with an appropriate coefficient of restitution obtained from the Contact Law, is physically the same as using the Contact Law itself, with the difference that the local deformation...
-
Normalized Impact Response and Damage in a Thin Composite Laminate Supported by a Rigid Substrate
Journal of Composite Materials, 1994Co-Authors: Andreas P Christoforou, A. S. YigitAbstract:The local impact response and damage of thin composite laminates are investigated. The impact model uses a static Contact Law which incorporates damage effects due to local Contact stresses. A major difference between this Contact Law and the others used previously is that the damage is accounted for during the loading rather than during the unloading phase which is expected to yield a more reasonable prediction of the maximum impact force. Normalization of the governing differential equations and initial conditions yields a single governing parameter, which is a dimensionless group of all the pertinent impact parameters (i.e., impact velocity, impactor mass, material and geometric properties). The introduction of this parameter not only simplifies the problem but also provides the necessary scaling rules for model testing.
Arun Shukla - One of the best experts on this subject based on the ideXlab platform.
-
Contact Law effects on wave propagation in particulate materials using distinct element modeling
International Journal of Non-linear Mechanics, 1993Co-Authors: Martin H Sadd, Arun ShuklaAbstract:Abstract The microstructural wave propagation behavior of a granular medium is modeled using the distinct element method. This technique simulates the discrete behavior of the medium by assuming that the motion of each particle may be modeled using Newtonian rigid-body mechanics with particular force-deformation and force-deformation rate Contact Laws. The present work provides a comparison of the effects of various Contact Laws on the wave propagational behaviors including wave attenuation and dispersion characteristics. Specific cases which have been studied include linear, non-linear and non-linear hysteretic force-deformation Contact Laws along with velocity proportional damping. Numerical results are compared with experimental data from dynamic photoelastic and strain gage experiments. Since velocity-dependent Contact damping is not a reasonable model for dry cohesionless granular media, it was desired to determine if a non-linear hysteretic Contact Law could be used to replace the velocity damping. Results indicate that such a non-linear Law does provide a damping mechanism which can predict experimental attenuation data, and that the dispersion characteristics are modeled more accurately with this hysteretic model.