• 한국군사과학기술학회지
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• 제13권6호
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• pp.1026-1033
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• 2010

The analysis of water-entry impact forces acting on the fin shaft of high speed water-entry body is described. During the entry of high speed body into water, the physical phenomenon and flow properties are analyzed. A proper analysis model is established and the method to estimate the flow force which causes impact torque at the fin shaft is described. It is assumed that the fin shaft is damaged by the force which is induced by contacting with cavity wall. The pressure distribution of fin and the maximum torque are estimated and compared with breaking force. Conclusively, it is hard to resist water-entry impact force in terms of the reinforcement of fin shaft. Additionally safe equipment is essentially required.

• 전력전자학회논문지
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• 제20권4호
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• pp.305-312
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• 2015

In this study, inter-turn short fault models of interior permanent magnet synchronous motors (IPMSM) are developed by adding saliency modeling to surface-mounted permanent magnet motor models. The saliency model is obtained using the deformed flux models based on both fault-winding flux information and inductance variations caused by cross-flux linkages that depend on the distribution of the same phase windings. By assuming the balanced three-phase current injection, we obtain the positive and negative sequence voltages and the fault current in the positive and the negative synchronous reference frames. The output torque model is developed by adding the magnet and the reluctance torque, which are derived from the developed models. To verify the proposed IPMSM model with an inter-turn short fault, finite element method-based simulation and experimental measurement results are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.750-752
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• 2003

This paper presents a method of tolerance analysis for a electric machine. Tolerance analysis technique is required to find the tolerance band of design variables and estimate the characteristic distribution of the electric machine, because that manufacturing tolerances as well as measuring errors have a great influence on the electric machine. Therefore, this paper introduces Stochastic Response Surface Methodology to achieve the tolerance analysis. As an example, the tolerance analysis is applied to the analysis of torque characteristics for a BLDC motor from the electric point of view.

• International Journal of Automotive Technology
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• 제6권5호
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• pp.467-473
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• 2005

A continuously variable transmission (CVT) with an inner spherical traction drive was conceptually designed for bicycle usage. The range of the overall speed ratio is from 1.0 to 4.5. The rated power and pedal speed are 100 Watts and 6 rad/s, respectively. The peculiar packageability, high-level power efficiency and high torque capacity were considered in the design process. A compact CVT that can be installed within a $244\times125\times160mm^3$ space and is above 0.9 in efficiency for the rated values was numerically designed. The distribution of efficiency according to the input torque and input speed were calculated. Gradeability in the prescribed operation mode was simulated.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.43-48
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• 2006

This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system. Under the combination operation of single & three phase load, voltage unbalance will be generated and current unbalance will be more severe by the dropped voltage quality. All power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. Moors may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.61-63
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• 1998

Disk type single phase SRM (DSPSRM) has a specific property of axial flux machine and radial flux machine simultaneously. So, this DSPSRM has a complicated magnetic circuit and it is difficult to analyze characteristics. Therefore, in this paper, the design specification of DSPSRM was calculated based on conventional design theory of electric machine and analyzed by 3D FEM. As the result of analysis, the approximated torque characteristics was obtained by finding the magnetic flux and energy distribution with the rotor position.

• Nuclear Engineering and Technology
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• 제35권2호
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• pp.133-143
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• 2003

Stem-stem nut coefficient of friction(COF) in motor-operated gate/globe valves is one of the important factors which determine the performance of the valve/actuators. The COF is affected greatly by the type and condition of the stem-stem nut lubricants, environmental parameters, surface condition of the stem/stem-nuts, and the number of strokes after the lubrication. In this paper, the measured data of the COFs at stem threads of some safety-related motor-operated gate/globe valves in domestic nuclear power plants are presented. In addition, the performance of the lubricants is evaluated by comparing the COFs among those valves. The results show that the measured COF at torque switch trip are higher than the unwedging COF and conservatively applicable to the unwedging COF. It is also shown that the lubricating performance based on the measured COFs varies with the lubricants.

• 대한치과기공학회지
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• 제42권2호
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• pp.99-105
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• 2020

Purpose: A study analysed the stress distribution of abutment screw and supporting bone of fixture by the tightening torque force of the abutment screw within clinical treatment situation for the stability of the dental implant prosthesis. Methods: The finite element analysis was targeted to the mandibular molar crown model, and the implant was internal type 4.0 mm diameter, 10.0 mm length fixture and abutment screw and supporting bone. The occlusal surface was modeled in 4 cusps and loaded 100 N to the buccal cusps. The connection between the abutment and the fixture was achieved by combining three abutment tightening torque forces of 20, 25, and 30 Ncm. Results: The results showed that the maximum stress value of the supporting bone was found in the buccal cortical bone region of the fixture in all models. The von Mises stress value of each model showed 184.5 MPa at the 20 Ncm model, 195.3 MPa in the 25 Ncm model, and 216.5 MPa in the 30 Ncm model. The contact stress between the abutment and the abutment screw showed the stress value in the 20 Ncm model was 201.2 MPa, and the 245.5 MPa in the 25 Ncm model and 314.0 MPa in the 30 Ncm model. Conclusion: The increase of tightening force within the clinical range of the abutment screw of the implant dental prosthesis was found to have no problem with the stability of the supporting bone and the abutment screw.

• 한국기계가공학회지
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• 제13권5호
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• pp.15-20
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• 2014

The wind industry grew in the first decade of the 21st century at rates consistently above 20% a year. For wind turbine, gearbox failure can be extremely costly in terms of repair costs, replacement parts, and in lost power production due to downtime. In this paper, gear tooth micro-modification for the high speed stage was used to compensate for the deformation of the teeth due to load and to ensure a proper meshing to achieve an optimized tooth contact pattern. The gearbox was firstly modeled in a software, and then the various combined tooth modification were presented, and the prediction of transmission under the loaded torque for the helical gear pair was investigated, the normal load distribution and root stress were also obtained and compared before and after tooth modification under one torque. The simulation results showed that the transmission error and normal load distribution under the load can be minimized by the appropriate tooth modification. It is a good approach where the simulated result is used to improve the design before the prototype is available for the test.

• Tribology and Lubricants
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• 제28권2호
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• pp.70-80
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• 2012

Non-contact type mechanical face seals installed in mechanical systems prevent leakage of working fluid using thin working fluid film between stator and rotor. For that purpose, various kinds of surface profiles, grooves and conings have been applied on seal surfaces of stator and rotor to generate hydrodynamic and hydrostatic pressure. The thickness distribution of working fluid film is one of important factors which affect the working performances of mechanical face seal, and it is strongly affected by the surface height profiles of stator and rotor. Therefore, appropriate design of surface height profiles of stator and rotor is necessary to optimize the working performances and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to estimate the working performances of wavy mechanical face seals which have 36 coning combinations. As results, minimum thickness of working fluid film, leakage volume of working fluid and friction torque in static equilibrium condition of mechanical face seal, and stiffness of working fluid film were obtained. The results show that the working performances of mechanical face seal were affected by the coning combinations which can change the thickness distribution of working fluid film and pressure distribution in sealing region of mechanical face seal.