• Tribology and Lubricants
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• 제37권2호
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• pp.48-53
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• 2021

Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

• 한국분말재료학회지
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• 제4권4호
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• pp.258-267
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• 1997

The powder forging process is an attractive manufacturing route for bevel gears. It offers beneficial material utilization and the minimization of finishing operations over that of conventional hot forging. The paper describes the process conditions for the powder forging of bevel gear, for example, powder alloy design, preform design, deformation of sintered preform, forging processes. The characteristics of prototype gear are investigated with microstructure, the density distribution, surface roughness of tooth, bending strength test of tooth, etc. The results of the bending strength test may prove the mechanical properties of powder forged gear.

• 대한기계학회논문집
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• 제18권3호
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• pp.591-599
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• 1994

A design system for power transmission bevel gears(straight, zerol, and spiral) is developed, in which the strength and durability of bevel gears can be estimated and the size of bevel gears can be minimized by introducing optimal techniques. The size of bevel gear pair as the object function to be minimized is the volume of equivalent spur gear pair at mean normal section, and the design variables to be determined are considered as the number of teeth, face width, diametral pitch, and spiral angle in spiral bevel gear. The strength(bending strength, pitting resistance) according to the AGMA standards, geometrical quantities, and operating characteristics(interference of pinion, contact ratio, etc.) are considered as the constraints in design optimization. The optimization with these constraints becomes nonlinear problem and that is solved with ALM(Augmented Lagrange Multiplier) method. The developed design method is applied to the example designs of straight, zerol, and spiral bevel gears. The design results are acceptable from the viewpoint of strength and durability within the design ranges of all other constraint, and the bevel gears are designed toward minimizing the size of gear pair. This design method is easily applicable to the design of bevel gears used as power transmitting devices in machineries, and is expected to be used for weight minimization of bevel gear unit.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.393-398
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• 2002

In this study, the increasing gear boxes for the high speed vertical in-line centrifugal pump are developed through rotor dynamic analysis. The developed increasing gear boxes are two kinds for 18000rpm and 25000rpm at the output shaft. The gear sets suitable for high speed and high load are manufactured by investigating AGMA bending strength and AGMA surface strength severely. The rotor dynamic analysis on gear sets and bearings is performed in order to avoid the critical speeds and other troubles. As a result of study, the two increasing gear boxes for the high speed vertical in-line centrifugal pump are designed and manufactured.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.343.1-343
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• 2002

In this study, the increasing gear boxes for the high speed vertical in-line centrifugal pump are developed through rotor dynamic analysis. The developed increasing gear boxes are two kinds fur 18000rpm and 25000rpm at the output shaft. The gear sets suitable for high speed and high load are manufactured by investigating AGMA bending strength and AGMA surface strength severely. The rotor dynamic analysis on gear sets and bearings is performed in order to avoid the critical speeds and other troubles. As a result of study, the two increasing gear boxes for the high speed vertical in-line centrifugal pump are designed and maunfactured.

• 드라이브 ㆍ 컨트롤
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• 제14권4호
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• pp.71-78
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• 2017

The power train of hydro-mechanical continuously variable transmission (HMCVT) for 8-ton class forklift includes hydro-static units, hydraulic multi-wet disc brake & clutches and complex helical & planetary gears. The helical & planetary gears are key components of HMCVT's power train wherein strength problems are the main concerns including gear bending stress, gear compressive stress, and scoring failure. Many failures in power train gears of HMCVT are due to the insufficient gear strength and resonance problems caused by major excitation forces, such as gear transmission error of mating gear fair in the transmission. In this study, wherein excitation frequencies are the gear tooth passing frequencies of the mating gears, a Campbell diagram is used to calculate the power train gears' critical speeds. Mode shapes and natural frequencies of the power train gears are calculated by CATIA V5. These are used to predict resonance failures by comparing the actual working speed range with the critical speeds due to the gear transmission errors of HMCVT's power train gears.

• Tribology and Lubricants
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• 제38권1호
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• pp.22-26
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• 2022

A 1.7-ton grade small excavator is a construction equipment that can perform various functions in limited spaces where heavy equipment cannot enter easily. Owing to the recent acceleration of urbanization, it has been used increasingly in drainage and gas pipes, as well as for road repair works in urban areas. The power train of a traveling reducer for a 1.7-ton grade small excavator utilizes a complex planetary gear system. Complex planetary gears are vital to the power train of a traveling reducer as it mitigates the fatigue strength problem. In the present study, the specifications of a complex planetary gear train are calculated; furthermore, the gear bending and compressive stresses of the complex planetary gears are analyzed to achieve an optimal design of the latter in terms of cost and reliability. In this study, the actual gear bending and compressive stresses of a planetary gear system are analyzed using a self-developed gear design program based on the Lewes and Hertz equation. Subsequently, the calculated specifications of the complex planetary gears are verified by evaluating the results with the data of allowable bending and compressive stress based on curves of stress vs. number of cycles of the gears.

• 대한기계학회논문집
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• 제14권3호
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• pp.594-602
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• 1990

본 연구에서는 동력전달용 인벌류우트 원통치차(스퍼어 및 헬리컬 기어)의 강 도 및 각종 영향인자를 충분히 고려하면서 크기를 최소로 하는 치차장치의 설계법을 개발하고, 이 설계법을 기본으로 하여 퍼스널 컴퓨터 상에서 누구나 손쉽게 설계에 이 용할 수 있는 설계 시스템을 개발하여 그 평가를 수행한다.

• 한국자동차공학회논문집
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• 제2권6호
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• pp.1-8
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• 1994

To enhance the strength of gears for transmission, Generally caburizing heat treatment is applied. But there are some problems in this technology the distortion of gears during heat treatment process, and the discontinuity of manufacturing process. For these reasons, the high frequency induction hardening process is widely used. This method is one of the surface hardening process to improve the wear resistance and fatigue life of the machine components. In this study, to compare the bending fatigue strength of caburized gear with that of induction hardened gear, bending fatigue testing of gears with two different cases was performed by using an electrohydraulic servo-controlled fatigue testing machine and double tooth bending fatigue test fixture. Fatigue life distributions at constant stress levels were established directly from fatigue data. For gear design, the fatigue strength distribution at specified life is more important. This distribution is obtained by statical transformation from fatigue life distribution. Reliability of bending fatigue strength was estimated by P-S-N curves and Weibull distribution.

• 항공우주시스템공학회지
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• 제14권6호
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• pp.91-99
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• 2020

This study proposes a finite element (FE) model for predicting the bending strength of small gears used in electro-mechanical actuators for aircraft. First, a strain gauge was attached to the tooth root of test gear, and the strain was measured. Subsequently, the FE model was applied to calculate the strain of the test gear, and the modeled strain was compared with the experimental strain. The results confirmed that the FE strain was very close to the experimental strain and the FE model was valid. This FE model was extended to the bending strength analysis of several small gear tooth models. The bending strengths of all the tooth models were almost identical to the ISO theoretical bending strength. Finally, the FE model was validated and the reliability of the modeled bending strength was evaluated through the strain measurement experiment.