Dynamic Response
J. Akbari; H. Valaei; M. F. Sepahvand
Abstract
Finite-element modeling of structures using elements without rotational degrees of freedom (DOFs) is usually stiffer than their physical behavior. Therefore, the stiffness of a structural system will be smoothed by adding rotational DOFs in the numerical model. In the traditional displacement-based finite-element ...
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Finite-element modeling of structures using elements without rotational degrees of freedom (DOFs) is usually stiffer than their physical behavior. Therefore, the stiffness of a structural system will be smoothed by adding rotational DOFs in the numerical model. In the traditional displacement-based finite-element method, adding drilling rotations is not easy. The main contribution of this paper is performing dynamic analyses using the finite strip element with added drilling rotations to the elements. For this purpose, any quadrilateral area is divided into two independent sets of orthogonal strips comprising truss and Bernoulli-Euler beam elements. Then by using new shape functions, mass, damping, stiffness matrices, and equivalent nodal forces are derived. Finally, time history analysis for plane stress or strain type problems for direct earthquake records is performed using the developed formulations. The numerical studies show that the results of the finite strip method using coarse meshes are competitive with the results of the finite-element method using fine meshes. This advantage is valuable in time-consuming computational problems, e.g., dynamic or nonlinear analyses.
Composite Materials
Aidin Ghaznavi; Mohammad Shariyat
Abstract
In the present article, the dynamic behavior of sandwich plates with embedded shape memory alloy (SMA) wires is evaluated for two cases wherein (i) the stress-strain curve of the superelastic behavior of the SMA wires is symmetric and (ii) the mentioned curve is non-symmetric. A modified version of Brinson’s ...
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In the present article, the dynamic behavior of sandwich plates with embedded shape memory alloy (SMA) wires is evaluated for two cases wherein (i) the stress-strain curve of the superelastic behavior of the SMA wires is symmetric and (ii) the mentioned curve is non-symmetric. A modified version of Brinson’s constitutive model is proposed and used. The high non-linearity in the behavior stems from the SMA wires embedded in the sandwich plate. In this regard, in addition to the proposed advanced algorithm for the determination of the martensite volume fraction, a Picard iterative solution algorithm is used in conjunction with Newmark’s numerical time integration method for solving the resulting finite element equations. To improve the accuracy of the results, the variation of martensite volume fraction and material properties of individual points of the structure are updated continuously. Therefore, the kinetic equations of the phase transformation of the SMA are coupled with the motion equations, to accurately model the nonlinear behavior of the sandwich plate. For analysis of the thick sandwich plate, a higher-order global-local theory with novel 3D-equilibrium-based corrections is utilized. One of the features of this theory is the estimation capability of the nonlinear in-plane displacement components, and precise assessment of the transverse shear stresses through satisfying the continuity conditions of the shear stresses at the interfaces between layers. Another advantage of the proposed theory in comparison with the conventional approaches is the ability to simulate changes in the core thickness. This is especially important in cases where the core is relatively thick or soft.
Composite Materials
Y. Bayat; M. Alizadeh; A. Bayat
Abstract
In this paper, a general solution for torsion of hollow cylinders made of functionally graded materials (FGM) was investigated. The problem was formulated in terms of Prandtl’s stress and, in general, the shear stress and angle of twist were derived. Variations in the material properties such as ...
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In this paper, a general solution for torsion of hollow cylinders made of functionally graded materials (FGM) was investigated. The problem was formulated in terms of Prandtl’s stress and, in general, the shear stress and angle of twist were derived. Variations in the material properties such as Young’s modulus and Poisson’s ratio might be arbitrary functions of the radial coordinate. Various material models from the literature were also used and the corresponding shear stress and angle of twist were individually computed. Moreover, by employing ABAQUS simulations, finite element results were compared with the analytical ones.
Manufacturing Processes
Abstract
Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet ...
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Laser bending is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. In this paper, temperature distribution in a mild steel sheet metal is investigated numerically and experimentally. Laser heat source is applied through curved paths in square sheet metal parts. Finite element (FE) simulation is performed with the ABAQUS/CAE standard software package. Material property of AISI 1010 is used in FE model and experiments. The aim of this study is to identify the response related to deformation and characterize the effect of laser power with respect to the bending angle for a square sheet part. An experimental setup including a Nd:YAG laser Model IQL-10 with maximum mean laser power of 500 W is used for the experiments to verify FE analysis results. It is observed that numerical results are relatively in good agreement with the experimental results. Results also show that increasing laser power increases the bending angle.
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