• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.29-40
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• 2004

The bearing capacity of drilled shaft is affected by several factors, such as shaft length, shape, surface roughness, young's modulus of geomaterials and shaft, soil strength, confining stress and so on. However, there has been no design method of drilled shaft considering all factors mentioned above. Moreover, since geomaterials are simply classified as sand, clay and rock, there was no design criterion for IGM (Intermediate Geomaterials). Therefore, the rigorous design approach of drilled shaft was not possible by classical design method. However, since these characteristics were not considered in classical theories, bearing capacity was generally different ken practical value. In this study, the bearing capacity of drilled shaft with the IGM's theory was compared with those of classical theories. The results showed that classical method showed smaller values of bearing capacity than those of field load transfer data. Moreover, the evaluated value of bearing capacity with IGM theory corresponded fairly well with those of field data.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.49-59
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• 2022

This study was conducted to find out the rational and appropriate design of drilled shaft. In other words, in order to find out the variation of ultimate bearing capacity according to the change in the support layer of drilled shaft, back analysis was performed using the bi-directional pile load test performed on drilled shaft. Based on the back-analyzed data, numerical analysis of the pile head load was performed, and the ultimate bearing capacity in the target ground was evaluated using the Davisson method. As a result of numerical analysis of one case where the end of the pile was seated on the top of the weathered rock layer, and three cases where the end of the pile was embedded at different locations in the weathered soil, it was found that sufficient ultimate bearing capacity was secured in all cases. In other words, the case where the end of the pile is seated on the top of the weathered rock layer, not embedded the weathered rock, and the drilled shaft embedded into the weathered soil also have sufficient bearing capacity, so it can be used as a support layer for drilled shaft.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2409-2420
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• 1996

This paper describes the development of a general program for the design and part load performance analysis of single-shaft-heavy-duty gas turbines. Efforts are made to fully represent the real component features by the characteristic models and special emphasis is put on the modeling of cooled turbine stages. The design analysis routine is applied to simulate the performance of current gas turbines and its appropriateness for system analysis is validated. Meanwhile, the component parameters of real engines which describe the technology level are obtained. The program is extended to predicting the part load operation of gas turbines with the aid of models for the off-design characteristics of compressor, turbine and other main components. Part load simulation can be carried out only with limited numbers of input data. It is demonstrated that the program accurately estimates the part load characteristics of real turbines.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.830-836
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• 2011

Most of pitch/yaw reducers consist of several planetary geartrains. Planetary geartrains make gearboxes to be small and light, low noise and good efficiency. Most important thing in the planetary geartrain is load distribution on the gear tooth flank. In this study, the effect of output shaft bearings on the load distribution of gear tooth flank has been investigated. The commercial software was employed to compare the load distribution of two models depending on the bearing type. The spherical roller bearing(SRB) and the cylindrical roller bearing(CRB) were used as output shaft bearings in the $1^{st}$ model, and two taper roller bearings(TRB) were used in the $2^{nd}$ model. As a result, it was found that the $2^{nd}$ model. showed better performances on the load distribution of gear tooth flank, this results stated that the output shaft bearing system could be important consideration when designing reducers for wind turbine systems.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.539-548
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• 1998

This study was intended to develop a load spectrum acting on a transmission of agricultural tractors. Transmission loads were measured at the input shaft of the transmission and final drive shaft of the tractors. The measurement were conducted in five field conditions at two speed levels under plowing operations in Korea. Two torque transducers were developed for the respective load measurements and other necessary instrumentations were made to collect the data and store them in a data logger. The time-histories of the torque loads were analyzed and transformed into the load spectra using the rainflow counting and Smith-Watson-Topper methods. Comparisons of the load spectra developed under different conditions were made to investigate their characteristics. The effects on the load levels of soil and plowing speeds were also investigated. Finally, a load spectrum combining the results of the spectrum analysis was developed and proposed as a load source for the reliability test of transmissions.

• Geomechanics and Engineering
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• v.5 no.5
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• pp.447-462
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• 2013

An analysis model for predicting the tip bearing capacity of drilled shafts in cohesionless soils is improved in this study. The evaluation is based on large amounts of drilled shaft load test data. Assessment on the analysis model reveals a greater variation in two coefficients, namely, the overburden bearing capacity factor ($N_q$) and the bearing capacity modifier for soil rigidity (${\zeta}_{qr}$). These factors are modified from the back analysis of drilled shaft load test results. Different effective shaft depths and interpreted capacities at various loading stages (i.e., low, middle, and high) are adopted for the back calculation. Results show that the modified bearing capacity coefficients maintain their basic relationship with soil effective friction angle ($\bar{\phi}$), in which the $N_q$ increases and ${\zeta}_{qr}$ decreases as $\bar{\phi}$ increases. The suggested effective shaft depth is limited to 15B (B = shaft diameter) for the evaluation of effective overburden pressure. Specific design recommendations for the tip bearing capacity analysis of drilled shafts in cohesionless soils are given for engineering practice.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.2
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• pp.53-63
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• 1991

This study suggests a new type shaft generator driven by hydraulic power suitable for small size vessels. Since the shaft generator system is very easy to be affected by disturbances such as speed variation of main engine and load variation of the generator, a robust servo control must be implemented to obtain stable electric power with constant frequency. Thus, in this study two types of controller design method-the reference following optimal control method and robust servo control method-are adopted to the controller design. In the experiment, static and dynamic characteristics of the shaft generator system according to the variation of input frequency setting, the speed variation of the pump and the load variation of the generator are investigated. From the considerations on the computer simulation results and experimental results, it is ascertained that the shaft generator system proposed in this study has good control performances.

• Transactions of Materials Processing
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• v.14 no.1 s.73
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• pp.57-64
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• 2005

This study deals with the cold forging process design for shaft in the main part of automobile motors with rectangular deep groove. In forging process, the accuracy and die lift is very important because it have influence on reduction of the production cost and the increase of the production rate. Therefore, it is necessary to develop the manufacturing process of shaft by cold forging., process variables are the cropped face angle of billet and the eccentric load of punch. The former is derived from cropping test, the latter is occurred by clearance between container and preform. Also, grooved preform select the process variable for decrease in punch deflection. We investigate that a deflection of punch and a deformation of preform to every process variables. Through this investigation, we suggest the optimal preform and process design, expect to be improved the tool life in forging process.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.201-211
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• 2001

The influence of aerated oil on high-speed journal bearing is examined by classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of aerated oil in fluid-film bearing. Convection to the walls, mixing with supply oil and re-circulating oil, and some degree of journal misalignment are considered. The considered Parameters for the study of bubbly lubrication are oil aeration level, air bubble size, shaft misalignment and shaft speed. The results show that deliberate oil aeration can more clearly bring on the increasing load capacity under high-speed operation of plain journal hearing than previous normal speed operation. And the load capacity may be increased more by oil aeration under the conditions of shaft misalignment and the increasing speed.

• Smart Structures and Systems
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• v.30 no.2
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• pp.209-219
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• 2022

The determination for bearing capacity of precast nodular piles is conventionally time-consuming and high-cost by using numerous experiments and empirical methods. This study proposes an intelligent method to evaluate the bearing capacity and shaft resistance of the nodular piles with high efficiency based on long short-term memory (LSTM) approach. A series of field tests are first designed to measure the axial force, shaft resistance and displacement of the combined nodular piles under different loadings, in comparison with the single pre-stressed high-strength concrete piles. The test results confirm that the combined nodular piles could provide larger ultimate bearing capacity (more than 100%) than the single pre-stressed high-strength concrete piles. Both the LSTM-based method and empirical methods are used to calculate the shift resistance of the combined nodular piles. The results show that the LSTM-based method has a high-precision estimation on shaft resistance, not only for the ultimate load but also for the working load.