• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.44 no.2
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• pp.59-65
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• 2018

Objectives: This study aimed to optimize the thread depth and pitch of a recently designed dental implant to provide uniform stress distribution by means of a response surface optimization method available in finite element (FE) software. The sensitivity of simulation to different mechanical parameters was also evaluated. Materials and Methods: A three-dimensional model of a tapered dental implant with micro-threads in the upper area and V-shaped threads in the rest of the body was modeled and analyzed using finite element analysis (FEA). An axial load of 100 N was applied to the top of the implants. The model was optimized for thread depth and pitch to determine the optimal stress distribution. In this analysis, micro-threads had 0.25 to 0.3 mm depth and 0.27 to 0.33 mm pitch, and V-shaped threads had 0.405 to 0.495 mm depth and 0.66 to 0.8 mm pitch. Results: The optimized depth and pitch were 0.307 and 0.286 mm for micro-threads and 0.405 and 0.808 mm for V-shaped threads, respectively. In this design, the most effective parameters on stress distribution were the depth and pitch of the micro-threads based on sensitivity analysis results. Conclusion: Based on the results of this study, the optimal implant design has micro-threads with 0.307 and 0.286 mm depth and pitch, respectively, in the upper area and V-shaped threads with 0.405 and 0.808 mm depth and pitch in the rest of the body. These results indicate that micro-thread parameters have a greater effect on stress and strain values.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.138-150
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• 2000

This study is concerned with computerized multi-level substructuring methods and stress analysis of coil springs. The purpose of substructuring methods is to reduce computing time and capacity of computer memory by multiple level reduction of the degrees of freedom in large size problems which are modeled by three dimensional continuum finite elements. In this paper, a super element has been developed for stress analysis of coil springs. The spring super element developed has been examined with tension and torsion simulation of cylindrical bars for demonstrating its validity. The result shows that the super element enhances the computing efficiency while it does not affect the accuracy of the results and it is ready for application to the coil spring analysis.

• Transactions of Materials Processing
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• v.19 no.8
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• pp.447-451
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• 2010

In this paper, a useful die system for warm plate forging of a large axle housing of heavy-duty trucks is presented. A die system composed of material flow guide pin as well as upper die and lower die is proposed to reduce the inherent thickness reduction along the bent corner of the product which deteriorates structural strength and fatigue life in its service. The role of the pin assembled in the upper die is to prevent formation of sharp corner in early forming stage and to supply material in the lower die cavity sufficient enough to thicken the bent corner at the final stroke. The mechanism of the die system is given and its effect on corner thickness of the product is revealed by two-dimensional finite element analysis under plain strain assumption. Three-dimensional finite element solutions are also given to verify validity of the two dimensional approach and to show the mechanics of the die system in detail. The die system has been successfully applied to manufacturing the axle housing of heavy-duty trucks.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.507-514
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• 2003

Most of CAE analyses for injection molding have been based on the Mele Shaw's approximation: two-dimensional flow analysis. in some cases, that approximation causes significant errors due to loss of the geometrical information as well as simplification of the flow characteristics in the thickness direction. Although injection molding analysis software using three-dimensional solid elements has been developed recently, such as Moldflow Flow3D, it does not contain a deformation analysis function yet. The present work covers three-dimensional deformation analysis or injection molded plastic parts using solid elements. A numerical scheme for deformation analysis has bun proposed from the results of injection molding analysis using Moldflow Flow3D. The accuracy of the proposed approach has been verified through a numerical analysis of rectangular plates with various thicknesses in comparison with the classical shell-based approach. In addition, the reliability of the approach has also been proved through an industrial example. an optical plastic lens, in comparison of real experiments.

• International Journal of Concrete Structures and Materials
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• v.9 no.1
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• pp.89-118
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• 2015

The geometric nonlinearity of off-diagonal bracing system (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three dimensional finite element modeling. Nonlinear static analysis is considered to obtain performance level and seismic behaviour, and then the response modification factors calculated from each model's pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behaviour and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.

• Steel and Composite Structures
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• v.39 no.3
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• pp.291-306
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• 2021

Based on Reissner's mixed variational theorem (RMVT), the authors develop a semi-analytical finite element (FE) method for a three-dimensional (3D) bending analysis of nonhomogeneous orthotropic, complete and incomplete toroidal shells subjected to uniformly-distributed loads. In this formulation, the toroidal shell is divided into several finite annular prisms (FAPs) with quadrilateral cross-sections, where trigonometric functions and serendipity polynomials are used to interpolate the circumferential direction and meridian-radial surface variations in the primary field variables of each individual prism, respectively. The material properties of the toroidal shell are considered to be nonhomogeneous orthotropic over the meridianradial surface, such that homogeneous isotropic toroidal shells, laminated cross-ply toroidal shells, and single- and bi-directional functionally graded toroidal shells can be included as special cases in this work. Implementation of the current FAP methods shows that their solutions converge rapidly, and the convergent FAP solutions closely agree with the 3D elasticity solutions available in the literature.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.809-815
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• 2002

For clarifying the mechanical phenomena of thermal elasto-plastic behavior on the multi-spot welded joints, this study has tried to carry out three-dimensional thermal elasto-plastic analysis on them. However, because the shape of multi-spot welded joints is not axi-symmetric, unlike the case of single-spot welded joint, the solution domain for simulation should be three-dimensional. Therefore, in this paper, from the results analyzed using the developed the three dimensional unstationary heat conduction and thermal elasto-plastic programs by an iso-parametric finite element method, mechanical characteristics and their production mechanism on single- and multispot welded joints were clarified. Moreover, effects of pitch length on temperature, welding residual stresses and plastic strain of multi-spot welded joints were evaluated, indicating that a pitch of 30mm was advantageous compared to a pitch of 15mm.

• The korean journal of orthodontics
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• v.54 no.2
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• pp.108-116
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• 2024

Objective: A three-dimensional-printed individual titanium plate was applied for maxillary protraction to eliminate side effects and obtain the maximum skeletal effect. This study aimed to explore the stress distribution characteristics of sutures during maxillary protraction using individual titanium plates in various directions and locations. Methods: A protraction force of 500 g per side was applied at forward and downward angles between 0° and 60° with respect to the Frankfort horizontal plane, after which the titanium plate was moved 2 and 4 mm upward and downward, respectively. Changes in sutures with multiple protraction directions and various miniplate heights were quantified to analyze their impact on the maxillofacial bone. Results: Protraction angle of 0-30° with respect to the Frankfort horizontal plane exhibited a tendency for counterclockwise rotation in the maxilla. At a 40° protraction angle, translational motion was observed in the maxilla, whereas protraction angles of 50-60° tended to induce clockwise rotation in the maxilla. Enhanced protraction efficiency at the lower edge of the pyriform aperture was associated with increased height of individual titanium plates. Conclusions: Various protraction directions are suitable for patients with different types of vertical bone surfaces. Furthermore, when the titanium plate was positioned lower, the protraction force exhibited an increase.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.1016-1023
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• 2000

The present work is concerned with three-dimensional finite element analysis of the hollow section extrusion process using a porthole die. The effects of related design parameters are discussed through the finite element simulation for extrusion of a triply-connected rectangular tubular section. For economic computation, mismatching refinement, an efficient domain decomposition method with different mesh density for each subdomain, is implemented. In order to obtain the uniform flow at the outlet, design parameters such as the hole size and the hole position are investigated and compared through the numerical analysis. Comparing the velocity distribution with that of the original design, it is concluded that the design modification enables more uniform flow characteristics. The analysis results are then successfully reflected on the industrial porthole die design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1912-1920
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• 1997

In the analysis of metal forming process, ALE(Arbitrary Lagrangian Eulerian) finite element methods have been increasingly used for the capability to control mesh independently from material flow. The methods can be divided into two groups i.e., coupled and split formulations. In the present work, the split ALE formulation is used for computational efficiency. A split ALE finite element method developed for rigid-viscoplastic materials and applied to the analysis of hot square die extrusion. Since thermal state greatly affects the product quality, an ALE scheme for temperature analysis is also presented. As computational examples, profile shapes as square and cross-like sections are chosen.