• Journal of Computational Design and Engineering
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• v.3 no.1
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• pp.63-70
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• 2016

Deep drawing is a forming process in which a blank of sheet metal is radially drawn into a forming die by the mechanical action of a punch and converted to required shape. Deep drawing involves complex material flow conditions and force distributions. Radial drawing stresses and tangential compressive stresses are induced in flange region due to the material retention property. These compressive stresses result in wrinkling phenomenon in flange region. Normally blank holder is applied for restricting wrinkles. Tensile stresses in radial direction initiate thinning in the wall region of cup. The thinning results into cracking or fracture. The finite element method is widely applied worldwide to simulate the deep drawing process. For real-life simulations of deep drawing process an accurate numerical model, as well as an accurate description of material behavior and contact conditions, is necessary. The finite element method is a powerful tool to predict material thinning deformations before prototypes are made. The proposed innovative methodology combines two techniques for prediction and optimization of thinning in automotive sealing cover. Taguchi design of experiments and analysis of variance has been applied to analyze the influencing process parameters on Thinning. Mathematical relations have been developed to correlate input process parameters and Thinning. Optimization problem has been formulated for thinning and Genetic Algorithm has been applied for optimization. Experimental validation of results proves the applicability of newly proposed approach. The optimized component when manufactured is observed to be safe, no thinning or fracture is observed.

• Transactions of Materials Processing
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• v.13 no.3
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• pp.248-252
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• 2004

The mechanical properties of polycrystalline thin-films, critical for Micro-Electro-Mechanical Systems (MEMS) components, are known to have the size effect and the scatter in the length scale of microns by the numbers of intensive investigation by experiments and simulations. So, the consideration of the microstructure is essential to cover these length scale effects. The lattice based stochastic model for the microstructure evolution is used to simulate the actual microstructure, and the fast and reliable algorithm is described in this paper. The kinetics parameters, which are the key parameters for the microstructure evolution based on the nucleation and growth mechanism, are extracted from the given micrograph of a polycrystalline material by an inverse method. And the method is verified by the comparison of the quantitative measures, the number of grains and the grain size distribution, for the actual and simulated microstructures. Finite element mesh is then generated on this lattice based microstructure by the developed code. And the statistical finite element analysis is accomplished for selected microstructure.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.47-55
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• 2013

PURPOSES : The purpose of this study is to investigate the optimal joint positions which can minimize distresses of concrete pavement containing box culvert with horizontally skewed angles. METHODS : The concrete pavement containing the box culvert with different skewed angles and soil cover depths was modeled by 3 dimensional finite element method. The contact boundary condition was used between concrete and soil structures in addition to the nonlinear material property of soil in the finite element model. A dynamic analysis was performed by applying the self weight of pavement, negative temperature gradient of slab, and moving vehicle load simultaneously. RESULTS : In case of zero skewed angle ($0^{\circ}$), the maximum tensile stress of slab was the lowest when the joint was positioned directly over side of box culvert. In case there was a skewed angle, the maximum tensile stress of slab was the lowest when the joint passed the intersection between side of the box culvert and longitudinal centerline of slab. The magnitude of the maximum tensile stress converged to a constant value regardless the joint position from 3m of soil cover depth at all of the horizontally skewed angles. CONCLUSIONS : More reasonable and accurate design of the concrete pavement containing the box culvert can be possible based on the research results.

• Computers and Concrete
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• v.5 no.2
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• pp.155-174
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• 2008

A new approach for nonlinear finite element analysis of corroded reinforcements in RC structures is elaborated in the article. An algorithmic procedure for producing the tension-stiffening curve of RC elements taking into consideration most of effective parameters, e.g.: the rate of steel bar corrosion, bond-slip behavior, concrete cover and amount of reinforcement, is illustrated. This has been established on both experimental and analytical bases. This algorithm is implemented into a nonlinear finite element analysis program. The abilities of the resulted program have been studied by modeling some experimental specimens showing a reasonable agreement between the analytical and experimental findings.

• International Journal of Railway
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• v.6 no.2
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• pp.69-77
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• 2013

In this study, numerical analysis and model experiments were conducted to analyze behavioral characteristics acting on the track roadbed with excavation through steel pipe injection, a non-exclusive method of crossing construction under railroad as primary target. In model experiments that simulate injection excavation behaviors with an increase in the depth of soil cover, the upper displacement was measured by construction of the first and the second pipes in order to predict actual behaviors, and the behavior characteristics were verified through numerical analysis. The investigation results showed that surface displacement was smaller under the condition of higher soil cover. In the case of injecting two pipes, when the first pipe was injected, deformation of the surface increased linearly in both settlement and uplift experiments. However, when the second pipe was injected, the amount of change was found to be very small due to the relaxation and plastic zones around the first pipe. In addition, the results of numerical analysis on the same cross section with the model experiment found that the results of investigation into settlement ratio and volume loss were in very good agreement with those obtained by the model experiment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.315-325
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• 2009

The thickness of the material can be thinned because arch cut-and-cover tunnel has the support mechanism by the axial force, and the ground reaction force due moderate deformation can be expected thereby making it be dynamically advantageous, therefore the arch cut-and-cover tunnel has become more widely used. An important characteristic of the arch cut-and-cover tunnel is that the thickness of the material can be thinned because precast arch type has the support mechanism by the axial force. However, there is a different stress state surrounding the structures between normally excavated tunnels and cut-and-cover tunnels, it should be considered at designing. Therefore, finite element method was carried out to examine the mechanical behavior of the precast arch cut-and-cover tunnel considering construction procedure.

• Structural Engineering and Mechanics
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• v.28 no.2
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• pp.239-257
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• 2008

Double-sided punched metal plate timber fasteners present projections on both sides, which offer improved joint fire resistance and better joint aesthetics. In this paper, 3-D nonlinear finite element models were developed to simulate double-sided nail plate fastener timber joints. The models, incorporating orthotropic elasticity, Hill's yield criterion and elasto-plasticity and contact algorithms, are capable of simulating complex contact between the tooth and the timber and between the base plate and the timber in a fastener. Using validated models, parametric studies of the double-sided nail plate joints was undertaken to cover the tooth length and the tooth width. Optimal configuration was assumed to have been attained when increase in nail plate tooth width did not result in a raise in joint capacity, in conjunction with the optimum tooth length. This paper presents the first attempt to model and optimise tooth profile of double-sided nail plate fastener timber joints, which offers rational designs of such fasteners.

• Structural Engineering and Mechanics
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• v.6 no.8
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• pp.883-899
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• 1998

The strength, deformation and buckling of a large engineering structure consisting of four ellipsoidal shells, two cylindrical shells with stiffening ribs and large holes, one conical shell and three pairs of large flanges under external pressure, self weight and heat sinks have been analysed by using two kinds of five different finite elements - four assumed displacement finite elements (shell element with curved surfaces, axisymmetric conical shell element with variable thickness, three dimensional eccentric beam element, axisymmetric solid revolutionary element) and an assumed stress hybrid element (a 3-dimensional special element developed by authors). The compatibility between different elements is enforced. The strength analyses of the top cover and the main vessel are described in the paper.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.49-57
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• 2008

One of the most important design concerns for undersea tunnels is to establish design water load and flow rate. These are greatly dependent on the hydraulic factors such as water head, cover depth, hydraulic boundary conditions. In this paper, the influence of the hydraulic design factors on the ground loading and the inflow rate was investigated using the coupled finite element method. A horse shoe-shaped tunnel constructed 30 m below sea bottom was adopted to evaluate the water head effect considering various water depth for varying hydraulic conditions and relative permeability between lining and ground. The effect of cover depth was analysed for varying cover depth with the water depth of 60 m. The results were considered in terms of pore water pressure, ground loading and flow rate. Ground loading increases with an increase in water head and cover depth without depending on hydraulic boundary conditions. This points out that in leaking tunnels an increase in water depth increases seepage force which consequently increases ground loading. Furthermore, it is identified that an increase in water head and cover depth increases the rate of inflow and a decrease in the permeability ratio reduces the rate of inflow considerably.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.4
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• pp.46-53
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• 1991

In the present study, Navier-Stokes equation is numerically solved by use of a Finite analytic method to obtain the 2-dimensional flow field in the square cavity. The basic idea of F.A.M. is the incorporation of local analytic solutions in the numerical solution of linear or non-linear partial differential equations. In the F.A.M., the total problem is subdivided into a number of all elements. The local analytic solution is obtained for the small element in which the governing equation, if non-linear, to be linearized. The local analytic solutions are then expressed in algebraic form and are overlapped to cover the entire region of the problem. The assembly of these local analytic solutions, which still preserve the overall nonlinearity of the governing equations, results in a system of linear algebraic equations. The system of algebraic equations is then solved to provide the numerical solutions of the total problem. The computed flow field shows the same characteristics to physical concept of flow phenomena.