• Transactions of Materials Processing
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• v.11 no.8
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• pp.682-690
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• 2002

The formation of adiabatic shearband in tungsten heavy alloys(WHA) was studied in this investigation. Five prismatic specimens were loaded by high velocity impacts and treated as plane strain problems. To find out the effect of particle's volume ratio, specimens containing 81%, 93% and 97% volume percents of tungsten particles were used. Also the effects of particle's geometry and size on the formation of shearband were studied for 81% volume percent alloys by small size particle model, large size particle model and undulated particle models, and the results were discussed.be used to diagnose the causes of necking and fracture in industrial practice and to investigate whether these defects were caused by material property variation, changes in lubrication, or incorrect press settings. In non-axisymmetric deep drawing, three modes of forming regimes are found: draw, stretch, plane strain. The stretch mode for non-axisymmetric deep drawing could be defined when the major and minor strains are positive. The draw mode could be defined when the major strain is positive and minor strain is negative, and plane strain mode could be defined when the major strain is positive and minor strain is zero. Through experiments the draw mode was shown on the wall and flange are one of a drawn cup, while the plane strain and the stretch mode were on the punch head and the punch corner area respectively, We observed that the punch load of elliptical deep drawing was decreased according to increase of die corner radius and the thickness deformation of minor side was more large than major side.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.1
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• pp.10-19
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• 2006

Statement of problem : The various kinds of properties of post and core may affect the stress distribution to the root of endodontically treated teeth Purpose: To evaluate the influence of various kinds of properties of post and core to the stress distribution to the root of endodontically treated teeth. Material and methods: Mandibular first premolar, prepared by general shape of post and core with gold crown, was used to two dimensional axisymmetric modeling for finite element analysis. Then property values of 8 different kinds of post and core was substituted for each. Finally, stress distribution shown areas around the root of post and core was analysed after applying 50N of vortical and oblique load. Results: 1. Stress value of oblique load was much higher than the maximum stress value of vertical load. 2. Under oblique load, very concentrated stress was located on post periapical area and variations in stress were very severe. Contrary to this, stress distribution was relatively uniform in vertical load. 3. Post materials with higher elastic modulus showed relatively more apically focused stress, and post materials with lower elastic modulus showed stress focused on cervical area on the axial wall of post. 4. Stress change according to the properties of core was shown only in the cervical area of post and below core as the higher elastic modulus, then increased in stress. 5. Post and core with medium value of elastic modulus showed relatively uniform stress distribution. Conclusions: Post materials with higher elastic modulus showed relatively more apically focused stress, and post materials with lower elastic modulus showed stress focused on cervical area on the axial wall of post. Stress change according to the properties of core was shown only in the cervical area of post and below core.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.75-80
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• 1991

The purpose of this study is to ascertain the robustness of p-version model with hierarchic intergrals of Legendre shape functions in various applications including plane stress/strain, axisymmetric and shell problems. The most important symptoms of accuracy failure in modern finite elements are spurious mechanisms and a phenomenon known as locking which are exhibited for incompressible materials and irregular shapes which contain aspect ratios(R/t, a/b), tapered ratio(d/b), and skewness. The condition numbers and energy norms are used to estimate numerical errors, convergence characteristics and algorithmic efficiencies for verifying the aforementioned symptoms of accuracy failure. Numerical results from p-version models are compared wi th those from NASTRAN, SAP90, and Cheung's hybrid elements.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03a
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• pp.172-184
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• 1996

Superplastic forming of thin sheet into complex shape is an important manufacturing process especially in aerospace industry. The main interest in modeling the superplastic forming process is to predict the forming pressure cycle to maintain optimum strain rate and the resulting thickness distribution. Many researchers have attemped to model superplastic forming using the various techniques including finite element method. But in most of their researches have disregarded the strain hardening effect which which occurs in several superplastic materials. In this study ABAQUS finite element code was used for prediction of process variables for axisymmetric cup forming of Supral 100 and 7075Al alloys considereing strain hardening. The performance of numerical results were compared with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.153-160
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• 1983

The flows in an axial flow turbomachine are calculated numerically in the two sets of flow surfaces of H-S and B-B surfaces assuming that the flow is axisymmetric. The calculation is performed by regarding the governing equations as the quasi-Poisson's equations and using the finite element method for the flow regions divided into triangular elements. The results of numerical calculation agree comparatively well with the experimental results and it has been found that the distribution of an axial velocity component at the rotor exit is not necessarily uniform under the influences of the inlet guide vanes and the front shape of the hub even if the rotor is designed by the free-vortex theory. Also it has been found that the existence of the optimum value of the blade number can be estimated from the results of calculation of deviation angles at rotor exit if we consider the viscous flow-loss, and that the flows of B-B surfaces are affected very sensitively by the degree of satisfaction of Kutta condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.221-229
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• 2001

The mechanical stress due to the wheel-rail contact and thermal stress due to the drag braking increase the incidence of wheel failure. So, firstly, stress analyses(mechanical, thermal and combined stress) of wheel plate are performed using 3-dimensional finite element method(FEM). Secondly, the optimum design of wheel plate ;s investigated in order to reduce weight of the wheel based on results of stress analysis. The optimum design is peformed using 2-dimensional axisymmetric F.E. model and its results are verified by 3-dimensional F. E. model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.371-375
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• 2006

A computational work has been performed to investigate the aerodynamics of a projectile which is launched from a ballistic range. A moving coordinate method for a multi-domain technique is employed to simulate unsteady projectile flows with a moving boundary. The variation of a virtual mass and the shape of projectile are added to the axisymmetric unsteady Euler equation systems. The present computational results properly predict the velocity, acceleration, drag histories and the major flow characteristics of the projectile.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.11a
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• pp.107-116
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• 1996

Numerical simulations have been conducted to characterize unsteady flow structures in an axisymmetric supersonic inlet diffuser with sinusoidal pressure oscillations at the diffuser exit. The formulation is based on the unsteady Navier-Stokes equations and turbulence closure is achieved using a two-layer model with a too-Reynolds-number scheme for the near-wall treatment. The governing equations are formulated in an integral form, and are discretized by the four-stage Runge-Kutta scheme for temporal terms and the Harten-Yee upwind TVD scheme for convective terms. Results indicated that the inlet shock characteristics are significantly modified by acoustic oscillations originating from the combustor. The characteristics of shock/boundarv-layer interactions (such as the size of separation bubble, terminal shock shape, and vorticity intensity) are also greatly iufluenced by the shock oscillation due to acoustic waves.

• Steel and Composite Structures
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• v.24 no.3
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• pp.359-367
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• 2017

In this work, transient heat transfer analysis of functionally graded (FG) carbon nanotube reinforced nanocomposite (CNTRC) cylinders with various essential and natural boundary conditions is investigated by a mesh-free method. The cylinders are subjected to thermal flux, convection environments and constant temperature faces. The material properties of the nanocomposite are estimated by an extended micro mechanical model in volume fraction form. The distribution of carbon nanotube (CNT) has a linear variation along the radial direction of axisymmetric cylinder. In the mesh-free analysis, moving least squares shape functions are used for approximation of temperature field in the weak form of heat transform equation and the transformation method is used for the imposition of essential boundary conditions. Newmark method is applied for solution time depended problem. The effects of CNT distribution pattern and volume fraction, cylinder thickness and boundary conditions are investigated on the transient temperature field of the nanocomposite cylinders.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.32.1-32.1
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• 2016

Early-type galaxies (ETGs) are supposed to follow the virial relation M ~ sigma^2 * R_e, with M being the galaxy mass, sigma being the stellar velocity dispersion, and R_e being the (2D) effective radius. I apply this relation to (a) the ATLAS3D sample and (b) the sample of Saglia et al. (2016). The two datasets reveal a statistically significant tilt of the empirical relation relative to the theoretical virial relation such that M ~ (sigma^2 * R_e)^0.92 with zero intrinsic scatter. This tilt disappears when replacing R_e with the semi-major axis of the projected half-light ellipse, a. Accordingly, a, not R_e, is the correct proxy for the scale radius of ETGs. By geometry, this implies that early-type galaxies are axisymmetric and oblate in general, in agreement with recent results from modeling based on kinematics and light distributions.