• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.12
• /
• pp.953-960
• /
• 2020

This paper presents an optimization of gear web design used in a main gear train of an engine reduction gearbox for a rotorcraft. The optimization involves the minimization of a total weight, transmission error, misalignment, and face load distribution factor. In particular, three design variables such as a gear web thickness, location of rim-web connection, and location of shaft-web connection were set as design parameters. In the optimization process, web, rim and shaft of gears were converted from the 3D CAD geometry model to the finite element model, and then provided as input to the gear simulation program, MASTA. Lastly, NSGA-II optimization method was used to find the best combination of design parameters. As a result of the optimization, the total weight, transmission error, misalignment, face load distribution factor were all reduced, and the maximum stress was also shown to be a safe level, confirming that the overall gear performance was improved.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.10a
• /
• pp.622-626
• /
• 1993

비원형기어의 기본적인 특징을 몇 가지 소개하고자 한다. 첫째, 간소한 기구로서 소형화할 수 있고, 둘째, 임의의 부동속 회전 전달을 얻을 수 있으며, 셋째, 맞물린 치면의 미끄럼접촉이 적기 때문에 마모피로가 적고 넷째, 고부하 전달이 가능하다는 장점들이 있다. 본 연구의 목적은 링크, 캠과 같은 동일한 용도에서 사용되는 다른 여러 기구에 비해 많은 이점을 가지고 있는 적합한 타원계 비원형기어(엽형)에서 편평도의 변화에 따른 피치라인을설계하고, 각속비 및 편평도에 따른 형상과 길이의 변화, 물림압력각, 곡률반경등의 연구를 바탕으로 스퍼형과 헬리컬형의 타원계 엽형로타를 AOTOCAD의 script, 3dace를 이용하여 Computer Simulation를 통해 도형화한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1991.06a
• /
• pp.70-75
• /
• 1991

기어는 기계시스템에서 동력전달 및 운동전환을 담당하는 기본 요소로 공작기계, 건설기계, 농업기계 등의 산업기계와 항공기, 자동차, 선박등의 운송분야, 사무용 및 계측기기 등 산업전반에 걸쳐 사용되고 있으며, 최근에는 로보트를 위시한 자동화 장치의 구동 및 동력전달 장치로 사용되고 있다. 최근의 기어시스템은 기계류의 일반적인 경향인 고속, 고부하, 결량화 추세에 따라 고정밀, 소형화되어 가고 있으며 부하한계에 가깝도록 큰 하중에 견딜것이 요구되고 있다. 따라서 기어의 설계 및 제작시, 여유있는 설계가 허용되지 않으며 정밀성을 높이기 위한 설계로, 설계인자의 세분화가 요구되어지고 있다. 국제적으로 통용되고 있는 강도설계 규격에서 면압강도시 표면상태계수(Surface condition factor)를 정의하고 있다. 본 연구에서는 동력순환식 기어 시험장치를 이용하여 표면처리 상태가 다른 3종류(열처리를 하지 않은 기어, 침탄 및 고주파 표면 열처리한 기어)의 스퍼어 기어를 이요하여 회전수별 표면거칠기의 변화 상태를 고찰하고, 변수를 응용하여 물리적 의미를 파아갛고, 윤활해석을 통한 윤활조건과 치면상태와의 상호 관계에 대하여 고찰해 보고자 한다.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.9 no.5
• /
• pp.40-49
• /
• 2010

Conical involute gears are being used for marine gearboxes, automotive transmissions, and robots, and so on, but not much. As involute profile gear, conical involute gear not only can be engaged with spur and helical gear but also can be used for power transmission of parallel, crossed and skewed axis with small angle. Hence, conical involute gears are likely to develop in future. Through a study on the basic theory of conical involute gear, tooth surface compressive stress analysis was performed by using commercial modeling program, comparing before and after profile modification. As a result, it noticed that tooth profile modification is able to relieve more tooth surface compressive stress than before modification.

• Tribology and Lubricants
• /
• v.9 no.2
• /
• pp.1-8
• /
• 1993

기어가 비교적 큰 하중과 고속의 운전상태에서 사용되는 경우 되풀이 응력에 의한 피로를 대상으로 하는 면압이나 굽힘강도 이외에 치면에서 발생되는 긁힘이나 융착(瀜着) 또는 용착(溶着)을 대상으로 한 스코어링(scoring) 강도를 고려하여야 한다. 스코어링은 주로 치의 이끝 부분에서 접촉방향으로 긁힘이 나타나는 손상으로 특징지워진다. 미국기어제조협회(AGMA)에서는 윤활막 파손에 의한 금속과 금속과의 접촉에 기인하여 발생되는 여러형태의 손상, 예를 들면 scuffing, seizing, galling 등을 광범위하게 스코어링으로 통칭하고 있다. 미국계통의 기술분야에서는 스코어링을 고온 스코어링(hot scoring)과 저온 스코어링(cold scoring)으로 구분하고 있다. 고온 스코어링은 고속 운전시 표면의 섬광온도(flash temperature)에 기인한 용착과 접촉방향으로 재료를 이탈시키는 형태를 나타내고, 저온 스코어링은 저속의 기어에서 윤활막 파단으로 표면에 줄질(filing)한 듯한 손상이 발생되는 것을 나타낸다. 유럽에서는 고온 스코어링 손상은 스커핑이라 하고 저온 스코어링손상만을 스코어링이라 부르고 있다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.11
• /
• pp.1391-1397
• /
• 2012

A cam ring gear (CRG) system based on a hypotrochoid curve consists of a pinion with roller teeth and its conjugated internal CRG. In this study, we investigated contact forces, contact stresses, and load stress factors to predict the surface pitting life using an exact CRG profile by introducing the profile modification coefficient. The results show that the pitting life can be extended significantly by increasing the profile modification coefficient without any other change of parameters in the CRG system.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.571-582
• /
• 2010

Typically nondestructive inspection methods of the large gear units are applied to penetrate non-destructive inspection. Nondestructive penetrating inspection put into the small openings of the defect to penetration liquid, remove to excess penetration liquid on the surface of the gear units, spread with developing solution and we can find the small defect by coating with penetration liquid. However, this method has so many issues because of penetrate nondestructive tests on the gear assembly. The steep angle of screw is hard to achieved full penetration and has the problem to remove the excess. In contrast, the magnetic nondestructive inspection is easy to detect subsurface defects and subtle defects. According to the inspection results the stress concentrates in gear surface, some internal defects and microscopic flaws exist on the gear units are not found to penetrate the nondestructive inspection, but magnetic nondestructive inspection could have found many defect. Therefore, a reasonable method of nondestructive inspection for the large gear units is suitable to magnetic nondestructive inspection.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.11
• /
• pp.1453-1459
• /
• 2011

A roller pinion gear (RPG) system composed of either a pin or a roller and its conjugated cam gear can improve the gear endurance from that of a conventional gear system by reducing the sliding contact while increasing the rolling motion. In this paper, we first proposed the exact cam gear profile and the self-intersection condition obtained when the profile shift coefficient is introduced. Then, we investigated the Hertzian contact stresses and the load stress factors while the varying the shape design parameters to predict the gear surface fatigue life, which is strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.

• Tribology and Lubricants
• /
• v.19 no.6
• /
• pp.357-364
• /
• 2003

The sub­surface stress field beneath the gear's contact surface caused by the contact pressure in lubricated condition has been calculated. To evaluate the influence of the clearance shape on the stress field, two kinds of tooth profile models were chosen. One is the conventional cylinder contact model and the other is the new numerical model. Love's rectangular patch solution was used to obtain the sub­surface stress field. The analysis results show that the sub­surface stress is quite dependent on both the contact pressure and the profile model. The maximum effective stress of the new model is lower than that of the old model. The depth where the maximum effective stress occurs in the new model is not proportional to the intensity of the external load.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.3
• /
• pp.80-88
• /
• 2010

A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.