• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1999.11a
• /
• pp.25-34
• /
• 1999

In this study, the sliding wear in spur gears, using Archard's wear model, is analyzed. Formulas of tooth sliding wear depth along the line of action are derived. The tooth profile is modified Id make a smooth transmission of the normal loads and the cylinder profile for reducing the pressure spike is suggested. The sliding wear rate is calculated with these profiling results. We expect these modification methods to contribute to the reduction of sliding wear in the root and the tip of tooth and tooth edge.

• Transactions of Materials Processing
• /
• v.4 no.3
• /
• pp.257-266
• /
• 1995

A simulation method based on upper bound method is developed in order to characterize forging characters in forging of spur gears. In this paper, utilizing a kinematically admissible velocity field and applying it to investigate the effect of inner diameter of holow billet. In the analysis, to predict the variation of inner diameter of hollw billet, neutral surface has been introduced. The neutral surface of each step is assumed as a circle and determined in order to have minimum forging energy by golden section method. By this method, the variation of inner diameter of billet during spur gear forging is successfully predicted. As a result, the selection of inner diameter of initial billet is very important to reduce the forging load.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.144-149
• /
• 1996

In this paper, the clamping type forging of helical gears has been investigated. Clamping type forging is an operation in which the product is constrained to extrude sideways through an orifice in the container wall. Punch is cylindrical shaped. The punch compresses a cylindrical billet placed in a die insert. As a consequence the material flows in a direction perpendicular to that of punch movement. The forging has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduced to represent tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, helix angle, friction factor and initial height of billet on the forging of helical gears.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.5
• /
• pp.46-56
• /
• 1995

As demands on the precision bevel gears are increased in the related industry, the exact kinematical investigations of a pair of spherical involute bevel gears are required for the computer aided design. The exact angular velocity ratio based on the characteristics of the spherical involute tooth is derived and verified from the relationship between rotational angles. Elementary kinematics of the gearsets is investigated by applying the transformation of the coordinate systems. The tooth contact lines based on logarithmic tooth-wise curve are examines in three dimentional space. Contact ratio is formulated and simulated according to the system parameters such as shaft angles, pressure angle, and spiral angles. The condition of teeth interference is dervied and the critical numbers of gear teeth are calculated. The whole surface geometry of a spiral bevel gearsets are discretized and visualized by a computer graphic tool.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.5
• /
• pp.40-45
• /
• 1995

The kinematical relationship of bevel gearsets lies at the root of the gear design. As the demand on precision bevel gears is increased in the related industries, the kinematic analysis of a pair of sperical involute bevel gears needs to be exactly evaluated for the computer aided design. Pitch cone angles of bevel gearsets have been calculated under the assumption that the geared system is equivalent to a coned roller system without slipping. But this kinematical model involves some errors in the value of the ratio of angular velocity. In this paper, the ratio of the angular velocity is exactly derived, based on the perfect involute tooth surface. Four nonlinear equations representing the kinematical relationships are numerically solved to obtain the pitch and base cone angles. The ratios of angular volocities according to pressure and shaft angles are calculated and compared with those of the approximate gear model.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1994.10a
• /
• pp.953-957
• /
• 1994

A performance prediction method is presented in this paper for design of a rotating machinery having power split/circulated transmisson with slip elements and planetary gears. And internal power flow patterns of such systems are theoretically analyzed by using mathematical modeling. To estimate usefulness of the designed machinary, geometrical approach has been adopted through the performance locus diagram which represents overall characteristics of the system. This gives us complect prediction of the qualitative performane and effects of design factors such as system layout, types and gear ratios of planetary gears and disign parameters of slip elements. The results for one of them are compared with experimental ones using dynamometer for verification.

• Journal of the Korean Society for Heat Treatment
• /
• v.27 no.4
• /
• pp.191-201
• /
• 2014

The gear was made of SNC815 case-carburized, quench hardened and tempered steel. The gears were failed far earlier than the expected service life used in the industrial site. Causes of the failed gear were analyzed by microstructure observation. By the SEM and micro structure examinations, the damaged surfaces had been weared and failed by fatigue. Through microscope observation on the damaged surface, it was found that the cause of failure was determined by external overloading and the initial stage of the damage was closely related to complex contact fatigue failure. The overload and contact fatigue contributed to the early failure cause.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.602-603
• /
• 2014

A gearbox can be regarded as a self-exciting dynamic system, which has a vibration source. Transmission error (TE) is considered to be an main excitation source for gear noise and vibration. The TE excitation is transmitted through the gears, shafts, bearings, and housings. Thus, an experimental approach to each mechanical parts is useful in order to understand and evaluate the dynamic behaviour of a gearbox. This study is focused on the transmission and vibration characteristics of a helical gear system in development stage. In addition, by considering the tolerance factors and resonance characteristics, the vibration response of actual dynamic system is analysed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.499-502
• /
• 2014

This paper presents a comparison study between simulation and experiment for fault diagnostics of a spur gear. In simulation, fault diagnostics using transmission error (TE) was performed and concluded to be valid. In a real experiment, however, it is not as easy to detect faults of gears using TE as in simulation. In this paper, after seeding the various faults like tooth crack of different length, tooth breakage and spalling in test rig, TE was calculated. Then, several signal processing techniques were performed to overcome the limitations of an experiment in detecting the fault signals of TE. After signal processing, we could detect the various faults of spur gears and different amplitude of TE sparks from cracks of different length. Then we discussed the difference between simulation and experment.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.738-739
• /
• 2006

This paper will describe a powder and processing method that facilitates single press-single sintered densities approaching $7.5g/cm^3$. At this sintered density, mechanical properties of the powder metal (P/M) component are significantly improved over current P/M technologies and begin to approach the performance of wrought steels. High performance gears have the added requirement of rolling contact fatigue durability that is dependent upon localized density and thermal processing. Combining high density processing of engineered P/M materials with selective surface densification enables powder metal components to achieve rolling contact fatigue durability and mechanical property performance that satisfy the performance requirements of many high strength automotive transmission gears. Data will be presented that document P/M part performance in comparison to conventional wrought steel grades.