• Journal of KSNVE
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• v.8 no.6
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• pp.1069-1077
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• 1998

A dynamic model of turbo compressor having helical gear pairs is developed. The model accounts for the shaft and bearing flexibilities, gyroscopic effects and the force couplings among the transverse, torsion. and axial motions due to gearings. For the mode analysis of turbo compressor, a transfer matrix method is used. The excitation sources caused by the mass unbalances of the rotors and misalignment of the shafts, the transmitted errors of the gearings. and the vane passing frequencies of the Impeller are studied qualitatively. By introducing the perturbation method, the generated forcing frequencies are defined and devided into three groups. With the field data, two critical speeds are analytically found and the corresponding modal characteristics are examined.

• Tribology and Lubricants
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• v.29 no.6
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• pp.378-385
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• 2013

An epicyclic gearing system is compact and lightweight. However, it is difficult to share the driving force equally because the system has closed gear trains with multiple driving points, and it always has geometrical errors in the elements. Thus, in the case of planetary gears, the first problem is how to distribute the load evenly to the numerous planets. The method widely used abroad for this purpose is to utilize the elastic deformation of the components of the structure. However, the deflection is very complicated, and it is very easy for vibration problems to occur because of the decrease in the natural frequencies. Therefore, to equalize the load on the planets, this paper discusses the principle and theory behind the functioning of a floating intermediate ring. This magnifies the displacement of a planet's center arising from the equilibrium of the load and the lubricating film pressure, which improves the compliance of the planets. The results show that load equalization of the planets is possible through this improvement in their compliance.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.40-45
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• 1995

The kinematical relationship of bevel gearsets lies at the root of the gear design. As the demand on precision bevel gears is increased in the related industries, the kinematic analysis of a pair of sperical involute bevel gears needs to be exactly evaluated for the computer aided design. Pitch cone angles of bevel gearsets have been calculated under the assumption that the geared system is equivalent to a coned roller system without slipping. But this kinematical model involves some errors in the value of the ratio of angular velocity. In this paper, the ratio of the angular velocity is exactly derived, based on the perfect involute tooth surface. Four nonlinear equations representing the kinematical relationships are numerically solved to obtain the pitch and base cone angles. The ratios of angular volocities according to pressure and shaft angles are calculated and compared with those of the approximate gear model.

• Journal of Power System Engineering
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• v.17 no.5
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• pp.128-137
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• 2013

Modern transmission technologies such as automated manual transmission(AMT) and dual clutch transmission(DCT) are interested to all manufactures due to their fuel efficiency and driver's convenience, especially in a hybrid system. AMT has advantages in that they have a high efficiency of manual transmissions(MT) and offer operation convenience similar to automatic transmissions(AT), but it has some disadvantages in that they have torque gap during gear shift and shift time. To reduce disadvantages, it is necessary to evaluate errors and characteristics as a developing simulation model before experimental verification. The purpose of this study is to develop virtual components and simulate the transient response of AMT. A dynamic AMT model and a control logic for an integrated vehicle model have been developed using Matlab/Simulink as a simulation platform. In this paper, the clutch model to describe the stick-slip transition mode and the transmission model to describe the neutral gear shifting is introduced and compared with each other.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1005-1011
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• 2016

The fundamental reason for gear noise is transmission error. Transmission error occurs because of STE (static transmission error) and DTE (dynamic transmission error), while a pair of gears is meshing. These errors are generated by the deflection of the teeth and the friction on the surface of the teeth. In addition, the vibration generated by transmission error leads to excited bearings. The bearings support the shafts, and the noise is radiated after exciting the gear casing. The analysis of the contact stress in helical gear tooth flanks indicates that it is due to impact loading, such as the sudden engagement and disengagement of a gear. Stress analysis is performed for different roll positions, in order to determine the most critical roll angle. Dynamic analysis is performed on this critical roll position, in order to evaluate variation in stresses and tooth contact force, with respect to time. In this study, transmission error analysis was implemented on a spur and helical gear with involute geometry and a modified geometry profile. In addition, in order to evaluate the intensity of impact due to sudden engagement and significant backlash, the impact factor was calculated using the finite element analysis results of static and dynamic maximum bending stresses.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.85-91
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• 2014

The rotation of a spindle unit must be accurate for high-quality machining and to improve the quality of the machine tools. Therefore, the proper measurement of the rotation accuracy and ensuring a proper analysis are very important. Separate processes are necessary because spindle errors and roundness errors associated with the test balls can both factor into the measured rotation error values. We used three methods to discern test ball errors and analyzed which could be deemed as the most proper technique in a test of the rotation accuracy of the main spindle of a machine tool.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.3 s.168
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• pp.162-169
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• 2005

The functional external fixator system fur bone deformity near joints in legs using the worm gear was developed for curing the difference angles in fracture bone and the lengthening bar for curing the difference length in fracture bone. Both experiments and FE analysis were performed to compare the elastic stiffness in several loading modes and to improve the functional external fixator system for the bone deformity. The FE model using the compressive and bending FE analysis was applied to the FE analysis due to the angle differences. The results show that the compressive stiffness value in experiment was 175.43N/mm; the bending stiffness value in experiment was 259.74N/mm; compressive stiffness value in FEM was 188.67N/mm; bending stiffness value in FEA was 285.71N/mm. The errors between experiments and FEA were less than 10%. The maximum stress (157MPa) to the angle of clamp was lower than the yield stress (176.4MPa) of SUS316L. The stiffnesses in both axial compressive and bending of the new fixator are about 2 times higher than other products except EBI (2003).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1248-1251
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• 2004

The functional external fixator system for bone deformity near joints in legs using the worm gear was developed for curing the difference angles in fracture bone and the lengthening bar for curing the difference length in fracture bone. Both experiments and FE analysis were performed to compare the elastic stiffness in several loading modes and to improve the functional external fixator system for bone deformity near joints in legs. The FE model using the compressive and bending FE analysis was applied the FE analysis due to the angle differences. The results show that the compressive stiffness value in experiment was 175.43N/mm, the bending stiffness value in experiment was 259.74N/mm, compressive stiffness value in FEM was 188.67N/mm, bending stiffness value in FEA was 285.71N/mm. The errors between experiments and FEA were less than 10％. The maximum stress (157MPa) to the angle of clamp was lower than the yield stress (176.4MPa) of SUS316L. The stiffnesses in both axial compressive and bending of the new fixator are about 2 times higher than other products except EBI (2003).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1096-1101
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• 2000

In machine tools, often a gearbox is installed to control the rotating speed of spindle, which sometimes generates problems of noise and vibration due to errors in tooth-meshing. In this study, the characteristics of, noise and vibration of given gearbox for a machine tool are analyzed experimentally. From the measurement, it was observed that the tooth-meshing component of the sound pressure level from the gearbox took its maximum at a specific operational speed. Therefore, the main content of this study is to investigate the reason why the above mentioned characteristics are observed. By investigating the natural frequencies of the components in gearbox, it was found that the natural frequencies of the rotating gear-shaft and gearbox for twisting mode were closely related to the first and second peak of sound pressure levels respectively. Thereform, in this study, those relations were identified by the impact test of rotating gear-shaft and-gearbox. In addition, we inserted the rubber between housing and bed, and analyze the effect of the rubber insertion on noise reduction by Operational Deflection Shapes.

• Journal of Mechanical Science and Technology
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• v.20 no.2
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• pp.234-241
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• 2006

A functional external fixator system for bone deformity near the joints using worm gear was developed for curing the angle difference in fracture bones while the lengthening bar was developed for curing the differences in length, also in fracture bones. Both experiments and FE analysis were performed to compare the elastic stiffness in several loading modes and to improve the functional external fixator system for bone deformity near joints. The FE model using compressive and bending FE analysis was applied due to the angle differentiations. The results indicate that compressive stiffness value in the experiment was 175.43N/mm, bending stiffness value in the experiment was 259.74 N/mm, compressive stiffness value in the FEA was 188.67 N/mm, and bending stiffness value in the FEA was 285.71 N/mm. Errors between experiments and FEA were less than $10\%$ in both the 'compressive stiffness and the bending stiffness. The maximum stress (157 MPa) applied to the angle of the clamp was lower than the yield stress (176.4 MPa) of SUS316L. The degree of stiffness in both axial compression and bending of the new fixator are about 2 times greater than other products, with the exception of EBI (2003).