• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1399-1406
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• 2011

The reducer of the mixer is one of the main parts of the processor used for water and wastewater treatment. In this study, an advanced reducer with a drywell structure was developed in order to prevent oil leakage during operation in the field. During the development of the advanced reducer prototype, a mockup, a metal mold, and a cast were made using CAD and a CNC machine. The structural safety of the reducer prototype's lower housing (drywell structure) was checked using the ALGOR commercial FEM analysis code, which yielded a von Mises stress of about 123 N/mm2, which is below the yield stress of 250 N/$mm^2$, and a natural frequency of about 650-700 Hz. In addition, the torque transmission efficiency for the advanced prototype was 95.87%, which is about 8% more than that found in a previous study, 88.45%, and the sound level was below 75 dB. Furthermore, no oil leakage or abnormal sound or vibration occurred. Therefore, an optimally designed advanced reducer prototype has been successfully developed.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.2_2
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• pp.327-332
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• 2023

As interest in eco-friendly and fuel-efficient electric vehicles has increased globally, there has also been a growing interest in the efficiency, vibration, and noise of motors for electric vehicles Electric vehicles generally have significantly lower driving ranges per charge compared to the maximum driving range per fueling of internal combustion engine vehicles. Additionally, there are issues with various vibrations and noise generated by the motor that can cause discomfort for passengers. Therefore, research is necessary to reduce losses, vibration, and noise of the motor to improve the driving range of electric vehicles. IPMSM with a purchased design can obtain additional reluctance torque by utilizing the difference in inductance between the d and q axes. However, due to this reluctance torque, torque ripple occurs larger than other motors. The increase in torque ripple also increases noise and vibration. Since the reluctance torque, which is the main cause of torque ripple, is determined by the shape of the motor components, torque ripple can be reduced through shape optimization. In this paper, a rotor shape for reducing torque ripple and core loss that causes vibration, noise, and efficiency to decrease of IPMSM for electric vehicles was proposed. Optimization design was carried out by changing the shape of the q-axis path of the rotor to reduce the difference in inductance of the d and q-axis of the rotor. Finally, in order to verify the validity of the design variables derived through the optimal design, the original model and the improved model were compared through the FEM. Compared to the original model, the improved model's torque verifying ripple was reduced by about 62% and core loss was reduced by about 29%, the superiority of the improved model.

• Steel and Composite Structures
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• v.24 no.2
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• pp.249-264
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• 2017

In this paper free linear vibration of lattice composite conical shells will be investigated. Lattice composite conical shell consists of composite helical ribs and thin outer skin. A smeared method is employed to obtain the variable coefficients of stiffness of conical shell. The ribs are modeled as a beam and in addition to the axial loads, endure shear loads and bending moments. Therefore, theoretical formulations are based on first-order shear deformation theory of shell. For verification of the obtained results, comparison is made with those available in open literature. Also, using FEM software the 3D finite element model of composite lattice conical shell is built and analyzed. Comparing results of analytical and numerical analyses show a good agreement between them. Some special cases as variation of geometric parameters of lattice part, effect of the boundary conditions and influence of the circumferential wave numbers on the natural frequencies of the conical shell are studied. It is concluded, when mass and the geometrical ratio of the composite lattice conical shell do not change, increment the semi vertex angle of cone leads to increase the natural frequencies. Moreover for shell thicknesses greater than a specific value, the presence of the lattice structure has not significant effect on the natural frequencies. The obtained results have novelty and can be used for further and future researches.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.55-60
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• 2009

The present study investigated temperature and thermal stress distributions in a film cooling system with normal injection cooling flow. 3D-numerical simulations using the FEM commercial code ANSYS were conducted to calculate distributions of temperature and thermal stresses. In the simulations, the surface boundary conditions used the surface heat transfer coefficients and adiabatic wall temperature which were converted from the Sherwood numbers and impermeable wall effectiveness obtained from previous mass transfer experiments. As a result, the temperature gradients, in contrast to the adiabatic wall temperature, were generated by conduction between the hot and cold regions in the film cooling system. The gradient magnitudes were about 10~20K in the y-axis (spanwise) direction and about 50~60K in the x-axis (streamwise) direction. The high thermal stresses resulting from this temperature distribution appeared in the side regions of holes. These locations were similar to those of thermal cracks in actual gas turbines. Thus, this thermal analysis can apply to a thermal design of film cooling holes to prevent or reduce thermal stresses.

• Transactions of Materials Processing
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• v.18 no.2
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• pp.150-155
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• 2009

A shaft for laser printers has to be produced with high dimensional accuracy of a few micrometers. Most companies produce the shaft, therefore, by machining. These days, forging process is tried to be employed in manufacturing the shaft for productivity. In this study, the dimensional inaccuracy of straightness is studied and the underfill is not focused because the shaft shape is simple and the load capacity of press is sufficient. The straightness and concentricity of the shaft is important for the operation of a laser printer. Many design parameters such as preform shapes, tooling dimensions, forging load, and billet geometries may affect on the dimensional accuracy. In the forging process of shafts, a billet which is cut from wires is used. The billet, therefore, may be a little bit curved but not always straight. The elastic recovery is considered to cause the dimensional inaccuracy. Therefore, the effect of the forging load on the elastic recovery and straightness is investigated through the finite element analyses using DEFORM-3D and ABAQUS.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.160-166
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• 2011

Weight reduction while maintaining functional requirements is one of the major goals in the automotive industry. The use of lightweight magnesium alloys offers great potential for reducing weight because of the low density of these alloys. However, the formability and the surface quality of the final magnesium alloy product for auto-body structures are not acceptable without a careful optimization of the design parameters. In order to overcome some of the main formability limitations in the stamping of magnesium alloys, a new approach, the so-called "hybrid technology", has been recently proposed for body-in-white structural components. Within this approach, necessary level of mechanical joining can be obtained through the use of lightweight material-steel adhesion promoters. This paper presents the development process of an automotive hybrid hood assembly using magnesium alloy sheets. In the first set of material pairs, the selected materials are magnesium alloy AZ31B alloy and steel(SGCEN) as inner and outer panels, respectively. In order to optimize the design of the inner panel, the stamping process was analyzed with the finite element method (FEM). Laser welding by CW Nd:YAG were used to join the magnesium alloy sheets. Based on the simulation results and mechanical test results of the joints, the determination of die design variables and their influence on formability were discussed. Furthermore, a prototype based on the proposed design was manufactured and the static stiffness test was carried out. The results demonstrate the feasibility of the proposed hybrid hood with a weight reduction of 25.7%.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.2
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• pp.48-53
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• 2014

The shield effect of 4 layered shield case was investigated in this paper. The material of the case was non-oriented SiFe sheet with a thickness of 0.5mm. The size of the case was 100mm wide, 100mm high and 300mm long. Relative permeability of SiFe sheet was needed to calculate shield effect. It was obtained from the measurement by a ferrite yoke and from the calculation by eddy current FEM analysis. Three configurations were used to connect both ends of SiFe sheet. First one is a connection by double-welded butt. Second one is to put the sheet the same material above the confronted both ends of the sheet to avoid a leakage magnetic flux. The last one is ideally without any connection. The shield effect of the second one agreed well with the last one and showed the shield effect of -40dB.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.250-255
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• 2008

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression. principle of virtual work is adapted. And this theory was programming using MATLAB software. To compare FEM using MATLAB software was applied MSC. Nastran software. The geometry model for MSC. Patran was produced by 3-D design modeling software. Finite element model was produced by MSC. Patran. Finite element was applied tetra (CTETRA) having 10 node. The analysis results of the MATLAB and MSC. Nastran are fairly well agreed with those of various experiments. Using MATLAB program proposed in this paper and MSC. Nastran, spring constants and stresses can be predicted by input of few factors.

• Computers and Concrete
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• v.26 no.2
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• pp.151-159
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• 2020

This paper presents an evaluation of shear transfer across cracks in reinforced concrete through finite element modelling (FEM) and analytical predictions. The aggregate interlock is one of the mechanisms responsible for the shear transfer between two slip surfaces of a crack; the others are the dowel action, when the reinforcement contributes resisting a parcel of shear displacement (reinforcement), and the uncracked concrete comprised by the shear resistance until the development of the first crack. The aim of this study deals with the development of a 3D numerical model, which describes the behavior of Z-type push-off specimen, in order to determine the properties of interface subjected to direct shear in terms cohesion and friction angle. The numerical model was validated based on experimental data and a parametric study was performed with the variation of the concrete strength. The numerical results were compared with analytical predictions and a new equation was proposed to predict the maximum shear stress in cracked concrete.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.136-140
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• 2006

We are developing a vol-oxidizer which transforms the spent $UO_2$ pellets into the $U_3O_8$ power through oxidizing process. The vol-oxidizer consists of furnace, filter, heater and valve etc. When the filter is blocked by the powder, the internal pressure of the furnace is increased owing to the air flow restriction. Then, the furnace vessel is swelled and deformed by it. In this paper, we proposed a procedure of the thermal analysis for furnace vessel design of spent fuel vol-oxidizer. In this work, we determined the thickness of the furnace through analyzing the internal pressure and the thermal stress of the furnace with respect to various pressure and temperature. To analyze the thermal stress, we used ANSYS 8.0 for constructing a FEM model of the furnace, and then analyzed it based on the ASME code. We also surveyed the material property and yield stress of SUS304 with various temperature. Analysis results are compared with the yield stress of the material. We manufactured the furnace and conduct the verification experiments.