• Structural Engineering and Mechanics
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• v.40 no.6
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• pp.783-800
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• 2011

This paper addresses the finite strip formulations for the stability analysis of viscoelastic composite plates with variable thickness in the transverse direction, which are subjected to in-plane forces. While the finite strip method is fairly well-known in the buckling analysis, hitherto its direct application to the buckling of viscoelastic composite plates with variable thickness has not been investigated. The equations governing the stiffness and the geometry matrices of the composite plate are solved in the time domain using both the higher-order shear deformation theory and the method of effective moduli. These matrices are then assembled so that the global stiffness and geometry matrices of a moderately thick rectangular plate are formed which lead to an eigenvalue problem that is solved to determine the magnitude of critical buckling load for the viscoelastic plate. The accuracy of the proposed model is verified against the results which have been reported elsewhere whilst a comprehensive parametric study is presented to show the effects of viscoelasticity parameters, boundary conditions as well as combined bending and compression loads on the critical buckling load of thin and moderately thick viscoelastic composite plates.

• Structural Engineering and Mechanics
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• v.48 no.3
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• pp.351-365
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• 2013

In this paper, unified nonlocal shear deformation theory is proposed to study bending, buckling and free vibration of nanobeams. This theory is based on the assumption that the in-plane and transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. In addition, this present model is capable of capturing both small scale effect and transverse shear deformation effects of nanobeams, and does not require shear correction factors. The equations of motion are derived from Hamilton's principle. Analytical solutions for the deflection, buckling load, and natural frequency are presented for a simply supported nanobeam, and the obtained results are compared with those predicted by the nonlocal Timoshenko beam theory and Reddy beam theories.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.199-203
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• 2004

In this paper, a simplified model is studied to predict analytically the radiated noise from the helical gear system due to an axial excitation of helical gear. The simplified model describes gear, shaft, bearing, and housing. To obtain the axial force of helical gear, mesh stiffness is calculated in the load deflection relation. The axial force is obtained from the solution of the equation of motion, using the mesh stiffness. It is used as a longitudinal excitation of the shaft, which in turn drives the gear housing through the bearing. In this study, the shaft is modeled as a rod, while the bearing is modeled as a parallel spring and damper only supporting longitudinal forces. The gear housing is modeled as a clamped circular plate with viscous damping. For the modeling of this system, transfer function from the shaft to the clamped plate are used, using a spectral method with four pole parameters. Out-of-plane displacement for the thin circular plate with viscous damping is derived and sound pressure radiated from the plate is also derived. Using the model, parameter studies are carried out.

• Steel and Composite Structures
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• v.45 no.4
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• pp.501-511
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• 2022

In this study, a two-dimensional model of the contact problem has been examined using the finite element method (FEM) based software ANSYS and based on the multilayer perceptron (MLP), an artificial neural network (ANN). For this purpose, a functionally graded (FG) half-infinite layer (HIL) with a crack pressed by means of two rigid blocks has been solved using FEM. Mass forces and friction are neglected in the solution. Since the problem is analyzed for the plane state, the thickness along the z-axis direction is taken as a unit. To check the accuracy of the contact problem model the results are compared with a study in the literature. In addition, ANSYS and MLP results are compared using Root Mean Square Error (RMSE) and coefficient of determination (R2), and good agreement is found. Numerical solutions are made by considering different values of external load, the width of blocks, crack depth, and material properties. The stresses on the contact surfaces between the blocks and the FG HIL are examined for these values, and the results are presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the contact stress distributions, and also, FEM and ANN can be efficient alternative methods to time-consuming analytical solutions if used correctly.

• Journal of the Korean Chemical Society
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• v.21 no.5
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• pp.330-338
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• 1977

In order to elucidate the plastic deformation of solids, the following assumptions were made: (1) the plastic deformation of solids is classified into two main types, the one which is caused by dislocation movement and the other caused by grain boundary movement, each movement being restricted on a different shear surface, (2) the dislocation movement is expressed by a mechanical model of a parallel connection of various kinds of Maxwell dislocation flow units whereas the grain boundary movement is also expressed by a parallel connection of various kinds of Maxwell grain boundary flow units; the parallel connection in each type of movements indicates that all the flow units on each shear surface flow with the same shear rate, (3) the latter model for grain boundary movement is connected in series to the former for dislocation movement, this means physically that the applied stress distributes homogeneously in the flow system while the total strain rate distributes heterogeneously on the two types of shear planes (dislocation or grain boundary shear plane), (4) the movement of dislocation flow units and grain boundary units becomes possible when the atoms or molecules near the obstacles, which hinder the movement of flow units, diffuse away from the obstacles.Using the above assumptions in conjunction with the theory of rate processes, generalized equations of shear stress and shear rate for plastic deformation were derived. In this paper, four cases important in practice were considered.ted N${\cdot}{\cdot}{\cdot}$O hydrogen bond and the second of two normal N${\cdot}{\cdot}{\cdot}$O hydrogen bonds, both of which exist between the amino group and the perchlorate, groups. A p-phenylenediamine group is approximately planar within an experimental error and bonded to twelve perchlorates: ten perchlorates forming hydrogen bonds and two being contacted with the van der Waals forces. A perchlorate group is surrounded by six p-phenylenediamines and four perchlorates; among the six p-phenylenediamines, five of them are hydrogen-bonded, and the rest contacted with the van der Waals force.

• Computers and Concrete
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• v.26 no.2
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• pp.107-114
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• 2020

In this study, a two dimensional model of receding contact problem has been analyzed using finite element method (FEM) based software ANSYS and ABAQUS. For this aim finite element modeling of elastic layer and two homogeneous, isotropic and symmetrical elastic quarter planes pressed by means of a rigid circular punch has been presented. Mass forces and friction are neglected in the solution. Since the problem is examined for the plane state, the thickness along the z-axis direction is taken as a unit. In order to check the accuracy of the present models, the obtained results are compared with the available results of the open literature as well as the results of two software are compared using Root Mean Square Error (RMSE) and good agreements are found. Numerical analyses are performed considering different values of the external load, rigid circular radius, quarter planes span length and material properties. The contact lengths and contact stresses of these values are examined, and their results are presented. Consequently, it is concluded that the considered non-dimensional quantities have noteworthy influence on the contact lengths and contact stress distributions, additionally if FEM analysis is used correctly, it can be an efficient alternative method to the analytical solutions that need time.

• Structural Engineering and Mechanics
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• v.15 no.3
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• pp.331-344
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• 2003

The plane contact problem for two infinite elastic layers whose elastic constants and heights are different is considered. The layers lying on a Winkler foundation are acted upon by symmetrical distributed loads whose lengths are 2a applied to the upper layer and uniform vertical body forces due to the effect of gravity in the layers. It is assumed that the contact between two elastic layers is frictionless and that only compressive normal tractions can be transmitted through the interface. The contact along the interface will be continuous if the value of the load factor, ${\lambda}$, is less than a critical value. However, interface separation takes place if it exceeds this critical value. First, the problem of continuous contact is solved and the value of the critical load factor, ${\lambda}_{cr}$, is determined. Then, the discontinuous contact problem is formulated in terms of a singular integral equation. Numerical solutions for contact stress distribution, the size of the separation areas, critical load factor and separation distance, and vertical displacement in the separation zone are given for various dimensionless quantities and distributed loads.

• Journal of Environmental Science International
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• v.12 no.8
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• pp.871-879
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• 2003

The complexation of co-contaminant mixtures between Ag(I) and polycyclic aromatic hydrocarbon (PAH) molecules (naphthalene, pyrene, and perylene) were investigated to quantify the equilibrium constants of their complexes and elucidate the interactions between Ag(I) and PAH molecules. The apparent solubilities of PAHs in aqueous solutions increased with increasing Ag(I) ion concentration. The values, K$_1$ and K$_2$ of equilibrium constants of complexes of Ag(I)-PAHs, were 2.990 and 0.378, 3.615 and 1.261, and 4.034 and 1.255, for naphthalene, pyrene, and perylene, respectively, The K$_1$and K$_2$ values of PAHs for Ag(I) increased in the order of naphthalene ＜ pyrene ＜ perylene and naphthalene ＜ pyrene ≒ perylene, respectively, indicating that a larger size of PAH molecule is likely to have more a richer concentration of electrons on the plane surfaces which can lead to stronger complexes with the Ag(I) ion. For the species of Ag(I)-PAH complexes, a 1:1 Ag(I) : the aromatic complex, AgAr$\^$＋/, was found to be a predominant species over a 2:1 Ag(I) : aromatic complex, Ag$_2$Ar$\^$＋＋/. The PAH molecules with four or more aromatic rings and/or bay regions were observed to have slightly less affinity with the Ag(I) ion than expected, which might result from inhibiting forces such as the spread of aromatic $\pi$ electrons over o wide molecular surface area and the intermolecular electronic repulsion in bay regions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1754-1761
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• 2003

The atomic force microscopy (AFM) based lithographic technique has been used directly to machine material surface and fabricate nano components in MEMS (micro electro mechanical system). In this paper, three-dimensional molecular dynamics (MD) simulations have been conducted to evaluate the characteristic of deformation process at atomistic scale for nano-lithography process. Effects of specific combinations of crystal orientations and cutting directions on the nature of atomistic deformation were investigated. The interatomic force between diamond tool and workpiece of copper material was assumed to be derived from the Morse potential function. The variation of tool geometry and cutting depth was also evaluated and the effect on machinability was investigated. The result of the simulation shows that crystal plane and cutting direction significantly influenced the variation of the cutting forces and the nature of deformation ahead of the tool as well as the surface deformation of the machined surface.

• Journal of the Korean Society for Railway
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• v.1 no.1 s.1
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• pp.30-39
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• 1998

The functions of diaphragms at abutments and piers of PSC box girder railway bridge are to transfer forces from the superstructure onto bearings or columns and to stiffen the superstructure cross-section against in -plane deformation. Due to stress disturbance at diaphragm, the design for the diaphragm using conventional design method is relatively irrational than those for other structural members. And, due to contribution to boundary condition of deck slab by the diaphragm, the behavior of deck slab near the diaphragm is different from that of the deck slab obtained from two dimensional analysis of the bridge, which is basis for the design of deck slab. In this paper, three dimensional behavior of deck slab near the diaphragm of prestressed concrete (PSC) box girder railway bridge constructed by the precast span method are analyzed by using three dimensional finite element modeling and using the strut-and-tie model design of the diaphragm are presented. The modeling techniques used in this paper can be applied effectively to examine the causes of cracks at deck slab near diaphragm and to design diaphragm rationally.