• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.2 s.119
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• pp.177-184
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• 2007

The purpose of this study is to investigate experimentally the characteristics of rotational, radial, and axial vibration for helical gears with different contact ratios. For this purpose, the gear box is specially designed and manufactured. Two helical gears with different face widths and reduction ratios are investigated. The gear vibration in each direction is measured by accelerometers attached to the gear body. Rotational vibration is the highest and radial vibration is the lowest in the gear frequencies. While the increase of rotational speed increases gear vibration, it does not always increase with torque. It is not also linearly related to the contact ratio. In addition, axial vibration is not proportional to rotational vibration.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.4
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• pp.59-65
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• 2010

This paper presents the study on the contact stress analysis of a pair of mating spur gears during rotation. Contact stress analysis is performed between two spur gear teeth at different contact positions during rotation. An example is presented to investigate the variation of contact stress on a pair of mating gears with contact positions. The variation of contact stress during rotation is compared with the contact stress at lowest point of single tooth contact(LPSTC) and AGMA Equation for contact stress. The results show that contact stress varies along the contact position and gets maximum values in the beginning and end of the contact. In this study, the gear design considering the contact stress on a pair of mating gears is more severe than that of AGMA standard.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.15-20
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• 2017

This study analyzed the load change of the gear generated by the operation of the vehicle recliner through Finite Element Analysis. The basic model of the recliner used was a commercial product, and the effect of the seat frame was excluded. The load conditions applied to the recliner were set considering gravity, the mass of the seat's back frame, and the weight of a person. The operating mode was set to move the seat back from the vertical to the reclined position. As a result, it was found that the tooth bending amount of the gear rim and wheel increased from the cam rotation angle of 450 degrees, and a change in the contact ratio occurred. Furthermore, excessive torque fluctuations occurred in the ranges of 390 to 450 and 750 to 710 degrees. It was found that this occurred in the region of about 30 degrees before and after the point where the x-axis direction load is larger than the y-direction load. From this torque fluctuation it was determined to likely to cause chattering noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.669-674
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• 2013

To design the optimized low noise planetary gear sets, a program called pRMC(planetary run many cases) is developed. The pRMC is especially using a combination analysis method for all gear specifications and also able to analyze any type of planetary gear sets. The pRMC is composed of the 5 sections those are generate, setting, evaluate, combine and analysis. After calculating all candidate gear sets, the pRMC could show many results that represent the character of each gear set including the transmission error which is the main gear noise factor, the contact ratios, the bending stress and so on. By comparing the results objectively, user could predict and select the optimized gear set which has quiet noise level and desired durability. The planetary gear designed by pRMC could have reduced noise and vibration level from 5 to 10 dB than previous-designed one.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.296-303
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• 1987

The composite gear which is composed of involute curve and circular arc has been studied. In the vicinity of pitch point, its profile is an involute curve, and in the dedenum, a circular arc. The curve in the dedendum is generated by the circular arc of the mating gear. Though the available range between minimum and maximum radius of circular arc can be given by existing tooth profile equation, there was no formulation which relates design parameters to the desired radius. It is attempted to get the formula for the radius of circular arc as a function of design parameters, such as unwounded angle, number of teeth, module, and pressure angle. The radius of circular arc, the chordal tooth thickness at working root circle, nominal bending stress, Hertz stress and contact ratio obtained from derived formula are compared with those of the existing design criteria. And these are compared with those of involute gear.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.1-10
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• 1993

A design method of gear tooth profile which can reduce the noise of gear is studied. The tooth profile is generated by combining involute and cycloid tooth curves in which the involute tooth profile is near the pitch point and cycloid tooth profile at the addendum and the dedendum. Considering parameters which have an influence on the reduction of gear noise and building up a design conditions for the noise reduction of gear, the lower-noise combined gear tooth profile is designed. For the check of noise reduction of the combined gear profile, two pairs of combined profile gear, two pairs of involute gear, and a pair of cycloid gear were manufactured by the NC Wire Cutting Machine, and the experiment for measuring of gear noise was carried out on each pair. The noise reduction of the combined profile gear was obtained.

• Social Workers
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• no.3 s.35
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• pp.32-35
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• 2005

사회복지공동모금회에 의하면 지난 '희망 2005 이웃사랑캠페인'에서 전년보다 개인기부나 기업기부가 각 60% 이상씩 늘어났다고 한다. 경제가 최악이라고 다들 말하지만 국민들의 따뜻한 마음은 최악이 아니였던 것이다. 이렇게 모인 금액은 우리가 흔히 말하는 불우이웃, 즉 빈곤층과 소외계층에 나누어져 지원된다. 그런데 문제는 이러한 분위기가 정부보다는 국민들에게 더 강하게 어필되고 있는 느낌이다. 우리나라 빈곤층은 1997년 경제위기 이후 급격히 늘어 1999년 정점에 이른 뒤 2000년부터는 감소추세였다. 그러나 2003년 기점으로 절대빈곤률과 상대빈곤률이 다시 높아지고 있으며, 특히 상대빈곤층은 최악의 상태였던 1999년보다 높아졌으며 중산층은 줄고 고소득층은 늘어 사회가 양극화 되고 있다. 가난의 굴레를 벗어나기가 쉽지 않다고는 하지만 그나마 사회안전망이라 할 수 있는 국민기초생활보장제도도 빈곤층에게 인간다운 아름다운 삶을 보장받게 해주지 못하고 있는 것이 사실이다. 또한, 정부의 복지정책의 근간이 되는 기본 실태조사좌도 그 신뢰성에 문제로 제기하고 있는 현 상황과 대책을 알아보고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.242-248
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• 2017

The purpose of this research is investigate the perception of first aid and differentiate between factors. The research subjects were 188 childcare teachers who work for day care centers in Chungchungnam-do, Republic of Korea and 70 pre-service childcare teachers who major in childcare in colleges in the same area. Collected data were converted to frequency and percentage, and cross correlation analysis was conducted for difference verification. The survey results are as follows. First, regarding the perception of first aid, there was a difference between childcare teachers and pre-service childcare teachers in their ability to cope with an emergency situation and responses to questions regarding frequent emergency situation. Second, the percentage of incorrect answers was high in the questions about impaction, poisoning, and biting. There were significant differences between the answers of childcare teachers and pre-service childcare teachers in questions about bleeding(injury), high fever, and CPR. In all of these questions, the percentage of correct answers of childcare teachers was higher. Regarding this result, clinical training for various emergency situations is needed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.124-130
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• 1995

연삭작업에 있어서 요구되는 가공능률과 가공정밀도를 얻기 위해서는 적절한 결합도를 갖는 연삭숫돌을 선택하 는 것이 중요한 요건이 된다. 본 연구에서는 결합도를 평가하기 위한 일정한 기준을 설정할 목적으로 AE계측 시스템을 이용하여 대월식결합도시험방법에 따라 연삭숫돌표면의 일부를 파괴시켰을 때 발생되는 AE신호를 검출 하고 연삭숫돌의 파괴량과 AE 신호특성과의 관계 및 AE를 이용한 결합도평가의 가능성을 검토하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.572-578
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• 1985

A composite gear with involute-circular are tooth profile and a tooth profile of the rack to cut this gear are theoretictically obtained. The composite gear has involute tooth profile in the vicinity of pitch point and has circular arc tooth profiles at addendum adn dedendum. The contact ratio(M$_{c}$), chordal tooth thickness (chordal tip tooth thickness S$_{t}$, chordal root tooth thickness S$_{t}$) of the composite gear are compared with those of involute gear. When module, number of teeth and pressure angle eqaul, S$_{t}$ of composite gear is much larger than that of involute gear. Under the same conditions, S/sib t/ and M$_{c}$ of composite gear become smaller than those of involute gear.lute gear.