• Tribology and Lubricants
• /
• 제39권1호
• /
• pp.1-7
• /
• 2023

Fluid pumps in chemical processes are typically driven by electric motors. Even if the motor is separated from the pump with seals, wear resulting from friction and misalignment can lead to leakage of chemical fluid, causing corrosion in the bearing supporting the motor, and, eventually, failure of the motor. It is thus a standard procedure to replace bearings at regular intervals. In this article, we propose 3D-printed plastic ball bearings for use as an alternative to commercial stainless-steel ball bearings. The plastic bearings are easy to manufacture, require less time to replace, and are chemically resistant. To validate the applicability of the plastic bearings, we first conducted chemical resistance tests. Bearings were immersed in 30 caustic acid and 30 nitric acid for 30 min and 24 h, respectively. The test results showed no corrosive damage to the bearings. A test rig was set up to compare the performance of the plastic bearings with that of the commercially equivalent deep-groove ball bearings. Loading test results showed that the plastic bearings performed as well as the commercial bearing in terms of vibration level and load-handling capability. Finally, a plastic bearing was subjected to a clean-in-place process for three months. It actually outperformed the commercial bearing in terms of chemical resistance. Thus, 3D-printed plastic bearings are a viable alternative to stainless-steel ball bearings.

• Tribology and Lubricants
• /
• 제40권4호
• /
• pp.111-117
• /
• 2024

Due to global CO₂ emission reductions and fuel efficiency regulations, the trend toward transitioning from internal combustion engine vehicles to electric vehicles (EVs) has accelerated. Consequently, the problem of EV failures has become a focal point of active research. The parasitic capacitance generated during motor-shaft rotation induces voltage that deteriorates the raceway and ball surfaces of bearings, causing electrical damage in EVs. Despite numerous attempts to address this issue, most studies have been conducted under high viscosity lubricant and low load conditions. However, due to factors such as high-speed operation, rapid acceleration and deceleration, motor heating, and motor system-decelerator integration, current EV applications have shown diminished stability in lubrication films of motor bearings, thereby leveraging the investigation to address the risk of electrical damage. This study investigates the electrical damage to rolling bearing elements in EV motor drive systems. The experimental analysis focuses on the effects of electric currents and operational loads on bearing integrity. A test rig is designed to generate high-rate voltage specific to a motor system's parasitic capacitance, and bearing samples are exposed to these currents for specified durations. Component evaluation involves visual inspections and vibration measurements. In addition, a predictive model for electrical failure is developed based on accumulated data, which demonstrates the ability to predict the likelihood of electrical failure relative to the duration and intensity of current exposure. This in turn reduces uncertainties in practical applications regarding electrical erosion modes.

• 한국도로학회논문집
• /
• 제3권3호
• /
• pp.135-146
• /
• 2001

기존의 교면포장공법의 근본적인 문제점으로 인해 새로운 교면포장 공법이 점차 부각되고 있는 실정이며, 새로운 교면포장 공법으로 연구되고 있는 것이 라텍스 개질 콘크리트를 이용하는 것이다. 따라서, 본 연구에서는 신설 콘크리트 교량 교면포장으로 덧씌우기된 LMC의 강도발현 특성과 덧씌우기 될 때의 기존콘크리트와의 부착특성을 파악하고자 하였다. 이런 연구를 위해 라텍스 혼입률에 따른 라텍스 개질 콘크리트의 압축강도와 휨강도, 그리고 기존콘크리트와의 부착강도를 측정하였다. 본 연구결과 라텍스 혼입량 증가로 폴리머 입자들의 볼베어링 작용, 연행된 공기 및 라텍스 안에 있는 계면활성제의 분산작용에 의하여 LMC의 작업성과 휨강도를 증가시킨다는 사실을 파악 할 수 있었고, LMC와 기존 콘크리트 슬래브와의 부착강도는 크게 증진함을 알 수 있었다.

• 한국건설순환자원학회논문집
• /
• 제2권1호
• /
• pp.46-51
• /
• 2014

본 연구에서는 단위수량 저감에 따른 하이볼륨 플라이애시 콘크리트의 강도 발현 특성을 평가하였으며, 목표강도 3수준 (40, 30 및 20MPa) 및 단위수량 변화에 따라 콘크리트를 제조하였다. 실험결과, 향상된 유동성은 50%이상의 플라이애시를 사용한 경우 플라이애시 구형 입자들의 볼베어링 효과, 플라이애시의 정전기적 반발력 및 플라이애시의 입도분포의 결과로 얻어졌으며, 이를 통하여 플라이애시 혼합이 콘크리트에 요구되는 물의 양을 감소시키는 것으로 나타났다. 또한 단위수량을 저감한 하이볼륨 플라이애시 콘크리트의 조기 강도는 일반적인 단위수량의 배합보다 약 66% 이상 향상되는 것으로 나타났다.

• 한국건축시공학회지
• /
• 제20권4호
• /
• pp.313-319
• /
• 2020

본 연구에서는 70MPa급 고강도 콘크리트에서 유공유리분말(HGP)의 적용성을 확인하기 위하여 HGP 사용량에 따라서 프레쉬 상태와 경화 상태의 물성을 검토하였고, 그 실험결과는 다음과 같다. 유동 특성은 HGP의 사용량이 증가할수록 슬럼프플로가 약간 증가하는 하는 것으로 나타났고 T₅₀₀은 HGP의 사용량이 증가할수록 약간 단축되었으며, 철근 통과성은 HGP의 볼베어링 효과로 인해 개선되는 것으로 나타났다. 특히 사용량 1.0kg/㎥에서 통과성 0등급으로 가장 양호한 철근통과성을 발휘하였다. 레올로지 특성으로는 HGP 1.0kg/㎥에서 소성점도가 Plain 대비 40% 정도 감소하여 HGP가 고강도 콘크리트의 소성점도를 낮추는 효과가 있는 것으로 확인되었다. 하지만 HGP 2.0kg/㎥에서는 1.0kg/㎥보다 오히려 소성점도가 크게 나타났다. 실험을 통하여 HGP가 고강도 콘크리트의 작업성 향상에 도움이 되는 것을 확인할 수 있었으며 사용량 1.0kg/㎥ 이 가장 적절한 것으로 판단된다. 또한 HGP가 콘크리트 압축강도에 영향을 미치지 않는 것으로 확인되었다.

• 한국정밀공학회지
• /
• 제22권4호
• /
• pp.113-120
• /
• 2005

This paper presents the development of the design of the robot element. Robot element design is an important part of robot design since it decides the performance and life time of the robot. It is necessary that the robot kinematics and the robot dynamics are accomplished to design the robot elements. The robot kinematics and dynamics determine the design parameters of the element. We developed a robot element design program with which a designer can design the robot element with convenience and reliability. The program is composed of motor, harmonic driver and ball-screw design. The program is founded on the virtual robot design program. The virtual robot design program is the powerful software which may be used to solve various problems of the robot kinematics and dynamics. The robot element design program may be used to calculate the design parameters of the element that are necessary to design robot element. Therefore, the designer can decide upon the available robot elements available to perform the objective of the robot. The robot element design program is expected to increase the competitiveness and efficiency of the robot industry.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2004년도 춘계학술대회 논문집
• /
• pp.416-423
• /
• 2004

This paper presents the thermal characteristic analysis of a high-speed horizontal machining center with spindle speed of 50,000rpm and feedrate of 120m/fin. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motors and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guides. The thermal characteristics such as the temperature distribution, temperature rise, thermal deformation and step response, are estimated based on the finite element model of machining center and the heat generation rates of heat sources related to the machine operation conditions. Especially, the thermal time constant assessed from the step response function is introduced as an index of thermal response characteristics.

• 대한기계학회논문집
• /
• 제11권6호
• /
• pp.935-944
• /
• 1987

본 연구에서는 금속 표면의 정밀가공법을 연구대상으로 하여 구상흑연주철시 편을 미량의 테이퍼로 연삭가공하고 NACHI 6000ZZ 볼 베어링을 로울러로 사용하여 로 울러 다듬질을 행함으로써 로울러 지름 변화에 따른 가압력이 표면조도에 미치는 영향 을 구명하는데 목적을 두었으며 아울러 로울링(rolling)회수에 따른 펴면조도, 경도 및 직경의 변화량을 실험적으로 구명하였다.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2004년도 학술대회지
• /
• pp.339-349
• /
• 2004

The method for fatigue life prediction of ball bearing is proposed applying the algorithm of contact fatigue prediction based on stress analysis. In order to do this, a series of simulation such as initial surface stress analysis, EHL analysis, subsurface stress analysis and fatigue analysis are conducted from the loading at each ball location calculated for a bearing subjected to external bearing load and contact shape function. And uniaxial fatigue tests are performed to obtain fatigue parameter of AISI 52100 steel. It was found that since stress is usually higher at the inner raceway contact than at the outer raceway contact, fatigue failure occurs on the inner raceway first. When the fatigue life calculated in the stress-based method are compared with $L_{50}$ life of L-P model, Crossland criterion for the radial load increment is similar to $L_{50}$ life and Dang Van criterion for the axial load increment is similar. In the case of EHL contact. there is no difference of fatigue life between dry contact and EHL contact, when maximum Hertz pressure exceeds 2.5GPa.

• Tribology and Lubricants
• /
• 제21권6호
• /
• pp.278-282
• /
• 2005

Deep groove ball bearing is installed in a control element of an integral nuclear reactor, where water is used as coolant and lubricant. This bearing is made of STS440C stainless steel for the raceways and the balls to use in radioactive environment and water. It is known that the retainer design affects ball bearing operability and endurance life, however there is no verified retainer design and material for water lubricated ball bearing. Four kinds of retainers are manufactured for the endurance test of water lubricated deep groove ball bearing. Three of them are commercially developed types and the other is designed for this research. It is verified that ball bearings with steel pressed and general plastic retainer can not survive to required life in the water, however bearings with machined type and cylinder type retainer can survive. This proves that one of the major design parameters for water lubricated ball bearing is retainer type and material. In this paper, experimental research of endurance test for water-lubricated ball bearing are reported.