• Journal of the Korean Institute of Gas
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• v.20 no.3
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• pp.73-77
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• 2016

This paper presents the displacement behavior safety of hollow shafts with an equivalent volume for various cross sectional area using a finite element method. The FEM results indicate that the hollow shafts with X-type or Y-type columns between outer tube, middle tube and inner tube may reduce a maximum displacement at the middle length of hollow shafts. Especially, the load-bearing column of X-type or Y-type hollow shaft is directly connected between outer tube and inner tube without a shift for reducing the vertical displacement. And increased thickness of a load-bearing column is recommended for reducing the vertical displacement and increasing the displacement behavior safety for an equivalent volume of a hollow shaft.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.5 s.236
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• pp.689-697
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• 2005

This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, $B_{10}$ life and its lower bound with $90\%$ confidence at worst case use condition are estimated by analyzing the accelerated life test data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1022-1027
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• 2002

This paper describes the fluttering characteristics of the upper pad in a tilting pad journal bearing(6-pad, LOP type) using a steam turbine. In order to investigate the phenomena of the upper pad fluttering experimentally, the absolute vibration of the upper pads the relative vibration between bearing and shaft and the circumferential distribution of the film thickness are measured under the different values of supply oil flow rate, shaft speed and bearing load. It can be known that the fluttering mechanism of the upper pads has a tendency of the self-excited vibration from the study of fluttering frequencies and amplitudes with the change of shaft speed. furthermore, it is observed that the incipient upper pad fluttering velocity is increased by the increase of oil supply flow rate and fluttering amplitude of the upper pads is increased by the decrease of the oil flow rate and by the increase of the bearing load.

• Journal of Biosystems Engineering
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• v.13 no.3
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• pp.20-31
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• 1988

This study was undertaken to investigate the load characteristics of the head-feed thresher, which may be affected by various factors such as physical properties of grain, thresher design parameters and its operational condition. The study was conducted at an initial step toward developing an automatic feed-rate control system of the head-feed thresher. A microcomputer-based data acquisition system for the load-speed characteristic of the thresher-shaft and the rail-deflection of the feeding device in accordance with a varied feeding thickness was developed. The sensors being developed and used for sensing the torque and speed of the cylinder and the power-input-shaft and the feeding thickness showed a high accuracy. A microcomputer-based data acquisition system developed in this study was assessed as adequate for a rapid acquisition and analysis of data. The effect of the feed-rate on the torque and speed of the thresher shaft, when fed intermittently by bundles, affected not by the rice varieties but by the dryness of threshing material tested. When fed by the continuous constant thickness, the torque and speed of the cylinder due to the increase of the feed-rate or feeding thickness were given by the relation by the second order parabola.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.842-847
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• 2008

Despite of the increasing number of the application of the drilled shaft pile in construction site, most of the study of pile capacity has been centered side shear resistance. But it is common that the drilled shaft is socketed on the rock so as to use the bearing resistance, so prediction of the toe's movement and characteristic of the bearing capacity is important as the side shear resistance. Therefore the model tests were performed in order to study the characteristic of bearing capacity on rock mass. The material of the test blocks were the mortar which was mixed with sand, cement and water, and test block size was $240{\times}240{\times}240mm$. Load was pressed by the 45mm of diameter of miniaturized pile and plate jack and steal plate were used to the confined stress for representing the underground condition. The relation of load-displacement was measured in many different conditions of rock mass such as direction of discontinuities, spacing and strength, and q-w curves of the toe of the pile were verified in each condition.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1166-1171
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• 2008

Despite of the increasing number of the application of drilled shaft piles in construction site, most studies on pile capacity have been focused on the side shear resistance. But it is common that the drilled shaft is socketed on the rock so as to use its bearing resistance. The prediction of the end movement and characteristics of the bearing capacity of the pile is great important as well. Therefore, a series of scaled model tests were carried out in order to study the characteristics of the bearing capacity on rock mass. The material of the test block was cement mortar which was mixed with sand, cement and water, and the size of a test block size was $240{\times}240{\times}240mm$. The axial load was applied by a miniaturized pile of 45mm in diameter and flat jacks and steel plate were used for confinement to simulate the real underground loading conditions. The relation of load-displacement was measured in various different conditions of rock mass such as strength, discontinuity of the rock mass and in-situ stress, so q-w curves of the end of the pile were presented for each condition.

• KSTLE International Journal
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• v.7 no.2
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• pp.35-44
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• 2006

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure, then the friction and load of journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• Tribology and Lubricants
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• v.23 no.5
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• pp.207-218
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• 2007

Turbocharger bearings are under the circumstance of high temperature, moreover rotated at high speed. It is necessary to be designed overcoming the high temperature. So the type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing inside temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of air-oil mixture in fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure distribution, then the friction in a journal bearing at high speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high temperature effects are canceled out each other. So, the bearing load and friction show almost no difference between the aerated oil and pure oil.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.6
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• pp.484-491
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• 2016

The purpose of this development is weight reduction of hollow type steel torque bar by changing the material from steel to composite. Structure analysis is executed by the finite element model generated by the structural load condition and geometric structure requirement. According to this analysis result, optimized ply sequence and wall thickness are defined. To simulate analysis result, torsion test for composite torque bar was performed. Throughout the test result, the stiffness and strength requirement of composite torque bar was verified.

• Proceedings of the Korean Reliability Society Conference
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• 2004.07a
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• pp.303-311
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• 2004

This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, B$_{10}$ life and its lower bound with 90% confidence at worst case use condition are estimated by analyzing the accelerated life test data.a.