• 한국정밀공학회지
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• 제29권6호
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• pp.671-679
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• 2012

This paper presents an estimation procedure for axial displacement in spindle equipped with angular contact ball bearings due to rotational speed. High-speed spindle-bearing system experiences axial displacement due to thermal expansion and rotational speed-dependent characteristics of angular contact ball bearings. This paper deals with the axial displacement caused by the rotational speed-dependent effects such as centrifugal force and gyroscopic moments. To this end, a bearing dynamic model is established that includes all the static and dynamic properties of angular contact ball bearing. An analytical formula to calculate the axial displacement based on contact angles between ball and races is derived to discuss the physics regarding the axial displacement in spindle. The proposed dynamic model is compared with a reference and a commercial program. Numerical examples are presented to show the effects of centrifugal force and gyroscopic moment on the axial displacement. The proposed model is also validated with an experimental result.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.389-392
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• 1997

This paper presents the dynamic analysis and experiment for rotor systems supported by angular contact ball bearings subjected to axial displacement preload. A dynamic software, which has been developed by the authors for the analysis of rotor systems supported by angular contact ball bearings, is used to simulate a uniform shaft system supported by two angular contact ball bearings with the axial displacement preload varied. Experiments are also performed to validate the simulation. An experimental system is constructed which consists of a uniform shaft, two bearings and a device for adjusting the axial displacement preload. Through a series of simulation and experiment, the dynamic characteristics of rotor systems with angular contact ball bearings subject to axial displacement preload are investigated.

• 대한기계학회논문집B
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• 제21권4호
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• pp.562-569
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• 1997

The axial position of an impeller is misaligned in the process of manufacturing and assembling. For a single suction centrifugal pump with balancing holes, the effect of axial displacement of impeller on the performance, leakage loss and axial thrust acting on the impeller is experimentally investigated. The axial displacement decreases the pump efficiency, increases the leakage through the clearance between wearing ring and impeller, and affects the characteristics of axial thrust.

• 한국생산제조학회지
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• 제5권4호
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• pp.121-128
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• 1996

In order to examine spindle deformation characteristics that affects the performance of dynmic cutting acuracy due to tool weight variation in a experimental spindle. thermal deformation value of operrative spindle by the axial displacement and the radial run out was measured according to the rise of spindle temperature through the laps of operation time and the change of rotational speed under the tool weight variation. A qualitative summary is as follows ; 1) The results show that the tool weight affcets the spindle temperature variation in a experimental spindle. 2) Radial run out and axial displacement was measured according to the rise of the spindle temperature and the performance of dynamic cutting accuracy was affected by the tool weight variation. 3) Axial displacement is 1.3 times larger than the radial run out in a experimental spindle conditions. 4) Axial displacement is continuously elongated when the tool weight is repeatly exchanged since the spindle themal deformaion, however, when the same tool weight is used. the displacement is still constant.

• The Journal of Advanced Prosthodontics
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• 제11권6호
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• pp.305-312
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• 2019

PURPOSE. The purpose of this study was to compare computer-aided design/computer-aided manufacturing (CAD/CAM) abutment and prefabricated abutment in Morse taper internal connection type implants after cyclic loading. MATERIALS AND METHODS. The study was conducted with internal type implants of two different manufacturers (Group Os, De). Fourteen assemblies were prepared for each manufacturer group and divided into 2 groups (n=7): prefabricated abutments (Os-P, De-P) and CAD/CAM abutments (Os-C, De-C). The amount of axial displacement and the removal torque values (RTVs) were measured before and after cyclic loading (10⁶ cycles, 3 Hz with 150 N), and the tensile removal force to dislodge the abutments was measured after cyclic loading. A repeated measures ANOVA and a pattern analysis based on the logarithmic regression model were conducted to evaluate the effect of cyclic loading on the axial displacement. The Wilcoxon signed-rank test and the Mann-Whitney test was conducted for comparison of RTV reduction% and tensile removal forces. RESULTS. There was no significant difference between CAD/CAM abutments and prefabricated abutments in axial displacement and tensile removal force; however, significantly greater RTV reduction% after cyclic loading was observed in CAD/CAM abutments. The correlation among the axial displacement, the RTV, and the tensile removal force was not significant. CONCLUSION. The use of CAD/CAM abutment did not significantly affect the amount of axial displacement and tensile removal force, but presented a significantly greater removal torque reduction% than prefabricated abutments. The connection stability due to the friction at the abutment-implant interface of CAD/CAM abutments may not be different from prefabricated abutment.

• 한국지진공학회논문집
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• 제28권1호
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• pp.59-65
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• 2024

This paper describes the seismic performance evaluation of reinforced concrete bridge columns under constant and varying axial forces. For this purpose, nine identical circular reinforced concrete columns were designed seismically by KIBSE (2021) and KCI (2021). A comparison of lateral forces with theoretical strength shows that the safety factor for columns under varying axial forces is less marginal than those under constant axial forces. In addition, columns under varying axial forces exhibit significant fluctuations in the hysteretic response due to continuously varying axial forces. This is particularly prominent when many varying axial force cycles within a specific lateral loading cycle increase. Moreover, the displacement ductility of columns under varying axial forces does not meet the code-specified required ductility in the range of varying axial forces. All varying axial forces affect columns' strength, stiffness, and displacement ductility. Therefore, axial force variation needs to be considered in the lateral strength evaluation of reinforced concrete bridge columns.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권8호
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• pp.368-372
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• 2003

This paper deals with the cogging torque analysis of a BLDC Motor, which has the axial displacement of its rotor. In order to improve the torque performance of the BLDC motor, Brushless motor is commonly designed to minimize its cogging torque. Therefore, a skewed model is used to reduce the cogging torque. However, even though the rotor or stator is skewed, the cogging torque could be increased by the axial displacement of the rotor, which occurs when the BLDC Motor is manufactured. Therefore, this paper investigates the effect of the axial displacement of the rotor on the cogging torque. In order to investigate the effect, an analysis method, which is 3D-EMCN in combination with 2D-FEM, is proposed to analyze the cogging torque of the BLDC motor with the axial displacement of its rotor, and the result of the analysis is verified by comparison with the experimental result.

• 대한치과보철학회지
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• 제59권1호
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• pp.126-133
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• 2021

여러 연구에서 임플란트 지지 보철물의 수직 침하에 대해 보고되고 있지만, 구강내 임플란트 지지보철물의 기능 시 수직침하 양상에 대해서는 알려진 바 없다. 본 증례에서는 2명의 환자에서 구치부 단일 치아 임플란트 지지 보철물의 3차원적인 변화를 평가하였다. 내부연결형 임플란트를 식립하였으며 통상적인 방법으로 Screw-Cement Retained Prosthesis(SCRP) 형태의 보철물을 제작해 장착하였다. 구강스캐너(Cerec Omnicam, Dentsply Sirona, USA)를 이용해 보철물 장착 시, 장착 1주, 1개월, 1년 후 구강 스캔을 시행하였으며 디지털 분석 프로그램(Geomagic Control X, 3D systems, USA)을 이용해 기간에 따른 위치 변화를 3차원적으로 평가하였다. 인접 치아를 기준으로 보철물 장착 후 임상적인 위치 변화가 나타났으며 변화량은 시간이 지남에 따라 증가하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.369-376
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• 1998

The purpose of the present study is to analyze the response of pipelines subjected to liquefaction-induced permanent ground displacement and to discuss the failure prediction of domestic waterway pipelines. Initially here, characteristics of liquefaction are reviewed and then permanent ground displacement is investigated base on previous earthquake hazard cases. Next, considering the distribution of the transverse permanent ground displacement and equivalent spring constant effect, formulas obtained by a beam theory are established to analyze continuous pipelines. This analysis was performed without consideration of axial effects. So the finite element analysis was used in order to consider the axial stiffness of soil. As a result, degree of liquefaction, width of deformed ground and axial stiffness are crucial points for evaluation the failure of pipelines subjected to permanent ground displacement.

• Journal of Periodontal and Implant Science
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• 제47권4호
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• pp.251-262
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• 2017

Purpose: The purpose of this study was to investigate the effects of implant tilting and the loading direction on the displacement and micromotion (relative displacement between the implant and bone) of immediately loaded implants by in vitro experiments and finite element analysis (FEA). Methods: Six artificial bone blocks were prepared. Six screw-type implants with a length of 10 mm and diameter of 4.3 mm were placed, with 3 positioned axially and 3 tilted. The tilted implants were $30^{\circ}$ distally inclined to the axial implants. Vertical and mesiodistal oblique ($45^{\circ}$ angle) loads of 200 N were applied to the top of the abutment, and the abutment displacement was recorded. Nonlinear finite element models simulating the in vitro experiment were constructed, and the abutment displacement and micromotion were calculated. The data on the abutment displacement from in vitro experiments and FEA were compared, and the validity of the finite element model was evaluated. Results: The abutment displacement was greater under oblique loading than under axial loading and greater for the tilted implants than for the axial implants. The in vitro and FEA results showed satisfactory consistency. The maximum micromotion was 2.8- to 4.1-fold higher under oblique loading than under vertical loading. The maximum micromotion values in the axial and tilted implants were very close under vertical loading. However, in the tilted implant model, the maximum micromotion was 38.7% less than in the axial implant model under oblique loading. The relationship between abutment displacement and micromotion varied according to the loading direction (vertical or oblique) as well as the implant insertion angle (axial or tilted). Conclusions: Tilted implants may have a lower maximum extent of micromotion than axial implants under mesiodistal oblique loading. The maximum micromotion values were strongly influenced by the loading direction. The maximum micromotion values did not reflect the abutment displacement values.