This is the first study on the free vibrational behavior of sandwich panels with flexible core in... more This is the first study on the free vibrational behavior of sandwich panels with flexible core in the presence of smart sheets of oil which is capable of the excitation of magnetic field. In order to model the core, the improved high order theory of sandwich sheets was used by a polynomial with unknown coefficients first degree shear theory was used for the sheets. The derived equations based on Hamilton principle with simple support boundary condition for upper and lower sheets were solved using Navier technique. Accuracy and precision of the theory were investigated by comparing the results of this study with those of analytical and numerical works. In the conclusion section, effect of the intensity of magnetic field and other physical parameters including ratio of sheet's length to width, ratio of sheet's length to thickness, ratio of core thickness to sheet's overall thickness, and ratio of oil layer thickness to sheet's overall thickness on natural frequency was...
Small mass impactors, such as runway debris and hailstones may result in a wave controlled local ... more Small mass impactors, such as runway debris and hailstones may result in a wave controlled local response, which is essentially independent of boundary conditions. The higher-order impact model of sandwich beams presented by . Higher-order impact modeling of sandwich structures with flexible core. International Journal of Solids and Structures 42 (10), 5460-5490] is developed and enhanced to impact analysis of sandwich panels with transversely flexible cores. Therefore, an improved fully dynamic higher-order impact theory is developed to analyze the low-velocity impact dynamic of a system which consists of a composite sandwich panel with transversely flexible core and multiple small impactors with small masses. Impacts are assumed to occur normally and simultaneously over the top face-sheet with arbitrary different masses and initial velocities of impactors. The contact forces between the panel and the impactors are treated as the internal forces of the system. First shear deformation theory (FSDT) is used for the face-sheets while three-dimensional elasticity is used for the soft core. The fully dynamic effects of the core layer and the face-sheets are considered in this study. Contact area can be varied with contact duration. The results in multiple mass impacts over sandwich panels that are hitherto not reported in the literature are presented based on proposed improved higher-order sandwich plate theory (IHSAPT). Finally, for the case study of the single mass impact, the numerical results of the analysis have been compared either with the available experimental results or with some theoretical results. As no literature could be found on the impact of multiple impactors over sandwich panels, the present formulation is validated indirectly by comparing the response of two cases of double small masses and single small mass impacts. Also, in order to demonstrate the applicability of the validation, the analytical relation of minimum distance between two impactors is derived based on Olsson's wave control principle in this paper.
ABSTRACT In this study, an improved high-order theory is presented for temperature-dependent buck... more ABSTRACT In this study, an improved high-order theory is presented for temperature-dependent buckling analysis of sandwich conical shell with thin functionally graded (FG) facesheets and homogenous soft core. First shear deformation theory (FSDT) is used for the facesheets and cubic functions are assumed for the transverse and in-plane displacements of the core. The nonlinear Von-Karman type relations are used to obtain the strain components. The equilibrium equations are derived via principle of minimum potential energy. Analytical solution for static analysis of simply supported sandwich conical shells under axial in-plane compressive load and in the temperature environments is performed using Galerkin’s solution. Numerical modeling is made by ABAQUS finite element (FE) code. The comparison shows that the present results are in good agreement with the results in the literature and the present FE results.
Cancer biomarkers : section A of Disease markers, 2008
Cervical cancer is one of the most common neoplastic diseases affecting women, with a combined wo... more Cervical cancer is one of the most common neoplastic diseases affecting women, with a combined world wide incidence of almost half a million new cases. Reduced DNA repair capacity (DRC) can render a high risk of developing many types of cancer; including cervical cancer. Polymorphisms in DNA repair genes may contribute the genetic instability and carcinogenesis. Smoking experience and use of oral contraceptives have been confirmed to be risk factors for cervical cancer. The purpose of the present study was, therefore to investigate APE-1 genotypes (Asp/Asp, Asp/Glu, Glu/Glu) with different histological subtypes in cases compared with controls. It has been observed that Asp/Glu with Glu/Glu genotypes that combined we observed statistically significant with protective effect for developing of cervix cancer (OR-0.51, 95% CI 0.31-0.83, p-0.006). The combined Asp/Glu with Glu/Glu genotypes who were using oral contraceptives were shown to be statistically significant with reduced risk of ...
ABSTRACT In this article, free vibrations of rectangular composite plate with and without a unifo... more ABSTRACT In this article, free vibrations of rectangular composite plate with and without a uniformly distributed attached mass are analyzed using the standard Galerkin procedure. The results of free vibrations without distributed attached mass are validated by some common literatures. The stiffness effect of the distributed attached mass is taken into account and the results are compared with those well-known published results in which this effect is not considered. Various results for isotropic and composite rectangular plates under a variety of conditions such as variation in thickness of the plate, variation in thickness of the distributed attached mass, fiber orientations and layup, and various elastic moduli for the distributed attached mass are presented in this article. In simple cases, to verify the results, other theories such as first-order shear deformation theory and classical lamination plate theory are used. Adding the stiffness of the attached mass increases the natural frequencies of the system.
Dynamic response of fiber metal laminate cylindrical shells subjected to initial combined axial l... more Dynamic response of fiber metal laminate cylindrical shells subjected to initial combined axial load and internal pressure were studied in this paper. First order shear deformation theory (FSDT) was utilized in the shell's equilibrium equations and strain-displacement relations were based on Love's first approximation theory. Equilibrium equations for buckling, free and forced vibration problems of the shell were solved using Galerkin method. The influences of FML parameters such as material properties lay up, Metal Volume Fraction (MVF), fiber orientation and initial stresses on dynamic response were investigated. The results were indicated that the FML lay up, has a significant effect on natural frequencies as well as transient dynamic response with respect to various values of MVF as well as pre-stress.
ABSTRACT Using an improved higher order sandwich panel theory (IHSAPT), the dynamic response of a... more ABSTRACT Using an improved higher order sandwich panel theory (IHSAPT), the dynamic response of a sandwich beam with arbitrary cores (foam or functionally graded materials) subjected to single impact at arbitrary impacted face sheet and arbitrary locations is studied. The formulation uses the first order shear deformation theory for the composite face sheets and a polynomial description of the displacements fields in the core which is based on the displacement field of the second Frostig's model. The unknowns are the coefficients of these polynomials in addition to the displacements of the various face sheets. It is assumed that the impactor impacted normally and simultaneously over the top or bottom face-sheets. The impact force between the impacted face sheet and the impactor is treated as the internal force of the system and in this study for the first time in order to simulate the impact phenomena, two models are presented: first, the linearized spring-mass model with two degrees of freedom (simply called TDOF) which can be solved by a new analytical method, second, the modified Hertz's model which uses the perfect form of contact law (perfect model). An impact problem of sandwich beam is first solved and the results obtained from TDOF and perfect models are validated by comparing with the analytical and numerical results published in the literature and also together. The agreement between the results is quite good. Then, the effect of various types of FGM function and its power and core to beam thickness ratio on the dynamic behavior of sandwich beam are studied.
Effect of some important parameters on low-velocity impact response of the active thin-walled hyb... more Effect of some important parameters on low-velocity impact response of the active thin-walled hybrid composite plates embedded with the shape memory alloy (SMA) wires is investigated in this paper. The interaction between the impactor and the composite plate is considered in the impact analysis. The SMA wires are embedded within the layers of the composite laminate. The effect of the
Optimization of the volume fraction, the orientation and the through thickness location of the sh... more Optimization of the volume fraction, the orientation and the through thickness location of the shape memory alloy (SMA) wires was used in order to minimize the maximum transverse deflection of the hybrid composite plate during the low-velocity impact phenomena. The prediction of optimal conditions of good geometrical properties of SMA wires in smart hybrid composites plays an important role in
ABSTRACT Fiber–metal laminates (FMLs) are high-performance hybrid structures based on alternating... more ABSTRACT Fiber–metal laminates (FMLs) are high-performance hybrid structures based on alternating stacked arrangements of fiber-reinforced plastic (FRP) plies and metal alloy layers. The response of FMLs subjected to low-velocity impact is studied in this paper. The aluminum (Al) sheets are placed instead of some of layers of FRP plies. The effect of the Al layers on contact force history, deflection, in-plane strains and stresses of the structure is studied. The first-order shear deformation theory as well as the Fourier series method is used to solve the governing equations of the composite plate analytically. The interaction between the impactor and the plate is modeled with the use of a two degrees-of-freedom system, consisting of springs-masses. The Choi's linearized Hertzian contact model is used in the impact analysis of the hybrid composite plate. The results indicated that some of the parameters like the layer sequence, mass and velocity of the impactor in a constant impact energy level, and the aspect ratio (a/b) of the plate are important factors affecting the dynamic response of the FMLs. Interaction among the mentioned geometrical parameters and material parameters like the aluminum 2024-T3 alloy layers is studied. The numerical results that are presented in this paper hitherto not reported in the published literature.
This is the first study on the free vibrational behavior of sandwich panels with flexible core in... more This is the first study on the free vibrational behavior of sandwich panels with flexible core in the presence of smart sheets of oil which is capable of the excitation of magnetic field. In order to model the core, the improved high order theory of sandwich sheets was used by a polynomial with unknown coefficients first degree shear theory was used for the sheets. The derived equations based on Hamilton principle with simple support boundary condition for upper and lower sheets were solved using Navier technique. Accuracy and precision of the theory were investigated by comparing the results of this study with those of analytical and numerical works. In the conclusion section, effect of the intensity of magnetic field and other physical parameters including ratio of sheet's length to width, ratio of sheet's length to thickness, ratio of core thickness to sheet's overall thickness, and ratio of oil layer thickness to sheet's overall thickness on natural frequency was...
Small mass impactors, such as runway debris and hailstones may result in a wave controlled local ... more Small mass impactors, such as runway debris and hailstones may result in a wave controlled local response, which is essentially independent of boundary conditions. The higher-order impact model of sandwich beams presented by . Higher-order impact modeling of sandwich structures with flexible core. International Journal of Solids and Structures 42 (10), 5460-5490] is developed and enhanced to impact analysis of sandwich panels with transversely flexible cores. Therefore, an improved fully dynamic higher-order impact theory is developed to analyze the low-velocity impact dynamic of a system which consists of a composite sandwich panel with transversely flexible core and multiple small impactors with small masses. Impacts are assumed to occur normally and simultaneously over the top face-sheet with arbitrary different masses and initial velocities of impactors. The contact forces between the panel and the impactors are treated as the internal forces of the system. First shear deformation theory (FSDT) is used for the face-sheets while three-dimensional elasticity is used for the soft core. The fully dynamic effects of the core layer and the face-sheets are considered in this study. Contact area can be varied with contact duration. The results in multiple mass impacts over sandwich panels that are hitherto not reported in the literature are presented based on proposed improved higher-order sandwich plate theory (IHSAPT). Finally, for the case study of the single mass impact, the numerical results of the analysis have been compared either with the available experimental results or with some theoretical results. As no literature could be found on the impact of multiple impactors over sandwich panels, the present formulation is validated indirectly by comparing the response of two cases of double small masses and single small mass impacts. Also, in order to demonstrate the applicability of the validation, the analytical relation of minimum distance between two impactors is derived based on Olsson's wave control principle in this paper.
ABSTRACT In this study, an improved high-order theory is presented for temperature-dependent buck... more ABSTRACT In this study, an improved high-order theory is presented for temperature-dependent buckling analysis of sandwich conical shell with thin functionally graded (FG) facesheets and homogenous soft core. First shear deformation theory (FSDT) is used for the facesheets and cubic functions are assumed for the transverse and in-plane displacements of the core. The nonlinear Von-Karman type relations are used to obtain the strain components. The equilibrium equations are derived via principle of minimum potential energy. Analytical solution for static analysis of simply supported sandwich conical shells under axial in-plane compressive load and in the temperature environments is performed using Galerkin’s solution. Numerical modeling is made by ABAQUS finite element (FE) code. The comparison shows that the present results are in good agreement with the results in the literature and the present FE results.
Cancer biomarkers : section A of Disease markers, 2008
Cervical cancer is one of the most common neoplastic diseases affecting women, with a combined wo... more Cervical cancer is one of the most common neoplastic diseases affecting women, with a combined world wide incidence of almost half a million new cases. Reduced DNA repair capacity (DRC) can render a high risk of developing many types of cancer; including cervical cancer. Polymorphisms in DNA repair genes may contribute the genetic instability and carcinogenesis. Smoking experience and use of oral contraceptives have been confirmed to be risk factors for cervical cancer. The purpose of the present study was, therefore to investigate APE-1 genotypes (Asp/Asp, Asp/Glu, Glu/Glu) with different histological subtypes in cases compared with controls. It has been observed that Asp/Glu with Glu/Glu genotypes that combined we observed statistically significant with protective effect for developing of cervix cancer (OR-0.51, 95% CI 0.31-0.83, p-0.006). The combined Asp/Glu with Glu/Glu genotypes who were using oral contraceptives were shown to be statistically significant with reduced risk of ...
ABSTRACT In this article, free vibrations of rectangular composite plate with and without a unifo... more ABSTRACT In this article, free vibrations of rectangular composite plate with and without a uniformly distributed attached mass are analyzed using the standard Galerkin procedure. The results of free vibrations without distributed attached mass are validated by some common literatures. The stiffness effect of the distributed attached mass is taken into account and the results are compared with those well-known published results in which this effect is not considered. Various results for isotropic and composite rectangular plates under a variety of conditions such as variation in thickness of the plate, variation in thickness of the distributed attached mass, fiber orientations and layup, and various elastic moduli for the distributed attached mass are presented in this article. In simple cases, to verify the results, other theories such as first-order shear deformation theory and classical lamination plate theory are used. Adding the stiffness of the attached mass increases the natural frequencies of the system.
Dynamic response of fiber metal laminate cylindrical shells subjected to initial combined axial l... more Dynamic response of fiber metal laminate cylindrical shells subjected to initial combined axial load and internal pressure were studied in this paper. First order shear deformation theory (FSDT) was utilized in the shell's equilibrium equations and strain-displacement relations were based on Love's first approximation theory. Equilibrium equations for buckling, free and forced vibration problems of the shell were solved using Galerkin method. The influences of FML parameters such as material properties lay up, Metal Volume Fraction (MVF), fiber orientation and initial stresses on dynamic response were investigated. The results were indicated that the FML lay up, has a significant effect on natural frequencies as well as transient dynamic response with respect to various values of MVF as well as pre-stress.
ABSTRACT Using an improved higher order sandwich panel theory (IHSAPT), the dynamic response of a... more ABSTRACT Using an improved higher order sandwich panel theory (IHSAPT), the dynamic response of a sandwich beam with arbitrary cores (foam or functionally graded materials) subjected to single impact at arbitrary impacted face sheet and arbitrary locations is studied. The formulation uses the first order shear deformation theory for the composite face sheets and a polynomial description of the displacements fields in the core which is based on the displacement field of the second Frostig's model. The unknowns are the coefficients of these polynomials in addition to the displacements of the various face sheets. It is assumed that the impactor impacted normally and simultaneously over the top or bottom face-sheets. The impact force between the impacted face sheet and the impactor is treated as the internal force of the system and in this study for the first time in order to simulate the impact phenomena, two models are presented: first, the linearized spring-mass model with two degrees of freedom (simply called TDOF) which can be solved by a new analytical method, second, the modified Hertz's model which uses the perfect form of contact law (perfect model). An impact problem of sandwich beam is first solved and the results obtained from TDOF and perfect models are validated by comparing with the analytical and numerical results published in the literature and also together. The agreement between the results is quite good. Then, the effect of various types of FGM function and its power and core to beam thickness ratio on the dynamic behavior of sandwich beam are studied.
Effect of some important parameters on low-velocity impact response of the active thin-walled hyb... more Effect of some important parameters on low-velocity impact response of the active thin-walled hybrid composite plates embedded with the shape memory alloy (SMA) wires is investigated in this paper. The interaction between the impactor and the composite plate is considered in the impact analysis. The SMA wires are embedded within the layers of the composite laminate. The effect of the
Optimization of the volume fraction, the orientation and the through thickness location of the sh... more Optimization of the volume fraction, the orientation and the through thickness location of the shape memory alloy (SMA) wires was used in order to minimize the maximum transverse deflection of the hybrid composite plate during the low-velocity impact phenomena. The prediction of optimal conditions of good geometrical properties of SMA wires in smart hybrid composites plays an important role in
ABSTRACT Fiber–metal laminates (FMLs) are high-performance hybrid structures based on alternating... more ABSTRACT Fiber–metal laminates (FMLs) are high-performance hybrid structures based on alternating stacked arrangements of fiber-reinforced plastic (FRP) plies and metal alloy layers. The response of FMLs subjected to low-velocity impact is studied in this paper. The aluminum (Al) sheets are placed instead of some of layers of FRP plies. The effect of the Al layers on contact force history, deflection, in-plane strains and stresses of the structure is studied. The first-order shear deformation theory as well as the Fourier series method is used to solve the governing equations of the composite plate analytically. The interaction between the impactor and the plate is modeled with the use of a two degrees-of-freedom system, consisting of springs-masses. The Choi's linearized Hertzian contact model is used in the impact analysis of the hybrid composite plate. The results indicated that some of the parameters like the layer sequence, mass and velocity of the impactor in a constant impact energy level, and the aspect ratio (a/b) of the plate are important factors affecting the dynamic response of the FMLs. Interaction among the mentioned geometrical parameters and material parameters like the aluminum 2024-T3 alloy layers is studied. The numerical results that are presented in this paper hitherto not reported in the published literature.
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Papers by K. Malekzadeh