• Advances in nano research
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• v.4 no.3
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• pp.229-249
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• 2016

In this paper, buckling characteristics of nonhomogeneous functionally graded (FG) nanobeams embedded on elastic foundations are investigated based on third order shear deformation (Reddy) without using shear correction factors. Third-order shear deformation beam theory accounts for shear deformation effects by a parabolic variation of all displacements through the thickness, and verifies the stress-free boundary conditions on the top and bottom surfaces of the FG nanobeam. A two parameters elastic foundation including the linear Winkler springs along with the Pasternak shear layer is in contact with beam in deformation, which acts in tension as well as in compression. The material properties of FG nanobeam are supposed to vary gradually along the thickness and are estimated through the power-law and Mori-Tanaka models. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. Nonlocal equations of motion are derived through Hamilton's principle and they are solved applying analytical solution. Comparison between results of the present work and those available in literature shows the accuracy of this method. The obtained results are presented for the buckling analysis of the FG nanobeams such as the effects of foundation parameters, gradient index, nonlocal parameter and slenderness ratio in detail.

• Computers and Concrete
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• v.29 no.2
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• pp.69-79
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• 2022

For long underground box utility tunnels, post-tensioned precast concrete is often used. Between precast tunnel segments, sealed waterproof flexible joints are often specified. Fault displacement can lead to excessive deformation of the joints, which can lead to reduction in waterproofing due to diminished contact pressure between the sealant strip and the tunnel segment. This paper authenticates utilization of a finite element model for a prefabricated tunnel fault-crossing founded on ABAQUS software. In addition, material parameter selection, contact setting and boundary condition are reviewed. Analyzed under normal fault action are: the influence of fault displacement; buried depth; soil friction coefficient, and angle of crossing at the fault plane. In addition, distribution characteristics of the utility tunnel structure for vertical and longitudinal/horizontal relative displacement at segmented interface for the top and bottom slab are analyzed. It is found that the effect of increase in fault displacement on the splice joint deformation is significant, whereas the effects of changes in burial depth, pipe-soil friction coefficient and fault-crossing angle on the overall tunnel and joint deformations were not so significant.

• Journal of Ocean Engineering and Technology
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• v.23 no.5
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• pp.39-44
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• 2009

The hydrostatic slipper bearing is generally used in high pressure axial piston pumps to support the load generated from two surfaces which are sliding relatively at low speed. The object of the bearing is to remove the possibility of direct contact by maintenance of an adequate oil film thickness between two metal surfaces. Because the bearing performance is influenced by the bearing deformation, it is highly dependent on the injection pressure, the bearing surface profile and so on. In this study, the deformation characteristics of a hydrostatic slipper bearing is investigated according to the injection pressure by the finite element analysis. In the analysis, the special boundary condition to take the fluid-structure interaction (FSI) into account is used on the interactive surface. The results, such as bearing deformation, stress and lifting force, obtained from the fully coupled analysis are compared with those from the single step sequential method.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.140-148
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• 1993

When a large automobile sheet metal part is formed in a draw die, the binder wrap is first calculated to predict the initial punch contact location for avoiding wrinkles and severe stretching of its thin blank sheet. Since the boundary of a pseudo blank in calculating a binder wrap by means of a geometrically nonlinear finite element method is unknown in advance, an iteration method is generally used. This paper presents an effective iteration method for correction of the pseudo blank in a binder wrap calculation. For the performance test, two examples are adopted. The calculated results for both examples show the good convergence which wasted solutions are obtained in the second iteration step.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.538-543
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• 2008

A roller with a shaft and hot oil paths for pressing electrodes of polymer batteries were modeled and analyzed by FEM. There are many hot oil tubes in the roller and shaft, through which $72^{\circ}C$ hot oil flows for heating the surface of a roller and shaft. Thermal deformations and temperatures distributions of the roller and shaft were calculated and a convection boundary condition on surfaces was used. The influence of existence of a groove in the shaft on the flatness of a roller surface caused by thermal deformation was investigated. In addition, the amount of spring-back of electrodes under vacuum pressure and heating was calculated after the hot rolling process. It was shown from this study that the groove in one shaft had a favorable effect on the surface flatness.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.425-430
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• 2000

In the analysis of deformation in which the stiffness is greatly different between the adjacent materials, the desired results have been obtained by using the interface element method compared with those secured by the conventional method of the concept of continua. This study deals with the deformation analysis of soft foundation by the introduction of interface element. The physical conditions of interface element are divided into three categories by Mohr-Coulomb failure criterion ie. sliding, separation, and contact. Finally the accuracy of the program proposed in this paper is proved highly accurate by performing the comparison of the theoretical values numerical results of a model element with simplified boundary conditions.

• Steel and Composite Structures
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• v.26 no.6
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• pp.771-791
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• 2018

This paper deals with the low velocity impact response and dynamic stresses of composite sandwich truncated conical shells (STCS) with compressible or incompressible core. Impacts are assumed to occur normally over the top face-sheet and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The displacement fields of core and face sheets are considered by higher order and first order shear deformation theory (FSDT), respectively. Considering continuity boundary conditions between the layers, the motion equations are derived based on Hamilton's principal incorporating the curvature, in-plane stress of the core and the structural damping effects based on Kelvin-Voigt model. In order to obtain the contact force, the displacement histories and the dynamic stresses, the differential quadrature method (DQM) is used. The effects of different parameters such as number of the layers of the face sheets, boundary conditions, semi vertex angle of the cone, impact velocity of impactor, trapezoidal shape and in-plane stresses of the core are examined on the low velocity impact response of STCS. Comparison of the present results with those reported by other researchers, confirms the accuracy of the present method. Numerical results show that increasing the impact velocity of the impactor yields to increases in the maximum contact force and deflection, while the contact duration is decreased. In addition, the normal stresses induced in top layer are higher than bottom layer since the top layer is subjected to impact load. Furthermore, with considering structural damping, the contact force and dynamic deflection decrees.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.747-754
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• 2004

The nonlinear finite element analysis for deformation characteristics of a power steering hose during the swaging process is performed in order to investigate the stress and the strain levels of the hose components. Power steering hose consists of components such as rubber hose, nylon, nipple and sleeve. Moreover, the numerical analysis requires the consideration of material, geometry and boundary nonlinearities. To evaluate the rubber hose strength, the measured stresses and strains are compared with tension and compression test data. Contact force is also a principal factor to examine whether rubber hose is break away from sleeve and nipple or not.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.397-408
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• 1988

The study is concerned with the theoretical and experimental investigation of the elliptical bulge test. The elliptical bulge test is analyzed by using a rigid-plastic finite element method incorporating large deformation and normal anisotropy. Thin elliptical diaphragms of mild steel are bulged for three aspect ratios. The contact problem the die round and the sheet is successfully solved by using a skew boundary condition. It is shown that the proper consideration of die radius and normal anisotropy is very significant. The relation between bulging pressure and deformation is obtained. It has been found that the pole is nearly under proportional straining during deformation. The instability criterion by maximum load condition enables the effective prediction of instability pressure. The computional results are in good agreement with experimental results and to be very useful for a better understanding of the elliptical bulge test.

• Tribology and Lubricants
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• v.30 no.4
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• pp.205-211
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• 2014

Recent studies emphasize the importance of pivot stiffness in the analysis of tilting pad bearings (TPBs). The present paper develops a finite element model of the pad pivot and compares the predicted pivot stiffness to the results of Hertzian contact model calculations. Specifically, a finite element analysis generates tetrahedral mesh models with ~40,000 nodes for a ball-socket pivot and ~50,000 nodes for a rocker-back pivot. These models assume a frictionless boundary condition in the contact area. Increasing the applied loads on the pad in conjunction with increasing time steps ensures rapid convergence during the nonlinear numerical analysis. Predictions are performed using the developed finite element model for increasing the differential diameters between the pad pivot (or ball) and the bearing housing (or socket). The predictions show that the pivot contact area increases with decreasing differential diameters and increasing applied loads. Further, the maximum deformation occurring at the pivot center increases with increasing differential diameters and increasing applied loads. The pivot stiffness increases nonlinearly with decreasing differential diameters and increasing applied loads. Comparisons of results of the developed finite element model to those of Hertzian contact model calculations assuming a small contact area show that the latter model underestimates the pivot stiffnesses predicted by the finite element models of the ball-socket and rocker-back pivots, particularly for small differential diameters. This result implies the need for cautionduring the design of pivot stiffness by the Hertzian contact model.