Oil film deposition characteristics and judgment of lubrication effect of splash lubricated gears

Feng-xia Lu,Kun Wei,Meng Wang,Mou Li,He-yun Bao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

To study the oil film deposition characteristics of splash lubricated gears and determine whether their meshing area is completely lubricated, this study proposes the concept of judging the splash lubrication-deposition characteristics-inlet oil film thickness-lubrication effect. The critical oil film thickness that characterizes the full lubrication of the gear meshing area was obtained as 14.5428 μm by using elastohydrodynamic lubrication (EHL) theory. Based on computational fluid dynamics (CFD) method, based on the renormalization group (RNG) k-ɛ two-equation turbulence model, dynamic mesh model and volume of fluid (VOF) model, the numerical calculation of the intermediate gearbox in splash lubrication is carried out. The oil film deposition thickness of the gear tooth that was about to enter the meshing area was calculated to be 95.6207 μm. It was found that the meshing area is fully lubricated under the rated operating conditions.

Deterministic surface roughness effects on elastic material contact with shear thinning fluid media

장시열 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.6

The formation of lubrication films is described using the hydrodynamic lubrication theory, which is based on the Reynolds equation that includes shear thinning behaviors of lubricant. Contacting surfaces are considered to undergo elastic deformation owing to concentrated contact pressures that exceed 1.0 GPa in most engineering applications. Under the contact condition of a high load on a relatively small contact area, elastic deformation of contacting bodies directly influences the formation of the lubricated film. Elastohydrodynamic lubrication (EHL) analysis is applied to correctly analyze the lubricated contact. Under an EHL contact, the scale of the lubrication film thickness is frequently less than that of the surface roughness that results from either the manufacturing or running-in processes. In this work, surface roughness is considered in detail, and two-dimensional surface roughness is measured as that characterizing general engineering surface roughness. The deterministic method regarding the surface roughness is considered for computing EHL film formation under several contact conditions such as load, contact velocity, and elasticity of contacting materials.

Enhanced friction model for high-speed right-angle gear dynamics

Zhiheng Feng,Shilong Wang,Teik C. Lim,Tao Peng 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.11

The modeling of elastohydrodynamic lubrication friction and the analysis of its dynamic effect on right-angle gears, such as hypoid and spiral bevel types are performed in the present study. Unlike the classically applied empirical constant coefficient of friction at the contacting tooth surfaces, the enhanced physics-based gear mesh friction model is both spatial and time-varying. The underlying formulation assumes mixed elastohydrodynamic lubrication (EHL) condition in which the division and load distribution between the full film and asperity contact zones are determined by the film thickness ratio and load sharing coefficient. In the proposed time-varying friction model, the calculation of friction coefficient is performed at each contact grid inside the instantaneous contact area that is being subjected to mineral oil lubrication. The effective friction coefficient and directional parameters synthesized from the net frictional and normal contact forces are then incorporated into a nonlinear time-varying right-angle gear dynamic model. Using this model, the effect of friction on the gear dynamic response due to the transmission error and mesh excitations is analyzed. Also, parametric studies are performed by varying torque, surface roughness and lubrication properties to understand the salient role of tooth sliding friction in gear dynamics. The simulation results are included. But experimental verification is needed.

롤러 축방향 프로파일의 형태에 따른 캠-롤러 종동물 접촉 유막 압력 해석 연구

장시열(Siyoul Jang),김완두(Wandoo Kim),김민철(Minchul Kim) 한국트라이볼로지학회 2005 한국트라이볼로지학회 학술대회 Vol.2005 No.11

Roller contacts with the consideration of finite axial length are studied with the respect of elastohydrodynamic lubrication. The profile of the axial direction in rollers is the main design factor in order to increase fatigue life due to the stress concentration along the edge of the roller. Even under the ehl lubrication conditions, the stress concentration along the edge of the roller greatly influences the fatigue life both for the roller and contacting bodies. In this work, several profiles are investigated to verify how the ehl film and pressure are generated and which profile is recommendable for the ehl contact condition.

Mixed Thermo elastohydrodynamic lubrication analysis of finite length cam and follower mechanism

Amir Torabi,Saleh Akbarzadeh,Mohammad Reza Salimpour 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

A considerable portion of the power loss in a valve train mechanism is due to the losses in the cam follower mechanism. The surface of cam and follower experience counterformal contact with a varying nature that makes it a difficult component in an engine to model. Transient contact geometry and entraining may cause the inlet boundary reversal and short lived cessation of entraining motion which can lead to mixed regime of lubrication. Thermal effects and side leakage intensify the adverse governing tribological condition. This paper presents a thermo-elastohydrodynamic model with considering roughness of surfaces for a finite length cam-follower mechanism. Temperature variation, friction coefficient, and film thickness are the outputs of this model which can be used to evaluate the performance of this mechanical element. The results are validated by comparison to other published data. The results show that thermal effects, side leakage and roughness of contacting surfaces play an important role in the tribological performance of the mechanism. A friction analysis considering a comprehensive asperity interaction model is conducted to investigate the proposed lubrication model capability.

Friction Assessment of Canola Oil on Contact Bearing Materials

Nicholas Nnaemeka Okechukwu,JaeYoung Byun,JongSoon Kim,JongMin Park,SoonGoo Kwon,SungWon Chung,SoonHong Kwon,WonSik Choi 한국트라이볼로지학회 2020 한국윤활학회지(윤활학회지) Vol.36 No.1

In manufacturing operations, oil plays a crucial role in reducing friction and wear among interacting surfaces at varying velocities, loads, and temperature. Hydrocarbon oil is considered the origin of lubrication oils. However, this base oil has been limited in its use as it is a principal cause of pollution. This research focuses on identifying a biodegradable base oil lubricant that possesses a stable coefficient of friction and viscosity with temperature. Friction analysis is conducted by employing a pin on a disk tribotester with a fixed load of 10 N at varying sliding speeds ranging from 0.06 m/s to 0.34 m/s. Oil viscosity analysis is perfomed at room temperature by using a rotary viscometer. Tests are performed using canola oil and paraffin oil as lubricants. The results indicate that the viscosity of canola oil is more efficient than paraffin oil. The non-dimensional characteristic number according to the Stribeck curve reveals an elastohydrodynamic lubrication regime with canola oil lubrication. A comparison of both lubricants reveals that, the friction efficiency of canola oil and paraffin oil does not differ considerably. However, the friction in canola oil is observed to decrease more than that in paraffin oil at an elevated sliding speed. The tests confirm that canola oil is potent in minimizing the friction coefficient of SCM440 bodies interacting with one another as well as acted upon by load.

Tribological performance evaluation and sensitivity analysis of piston ring lubricating film with deformed cylinder liner

Usman, Ali,Ahmad Cheema, Taqi,Woo Park, Cheol SAGE Publications 2015 Proceedings of the Institution of Mechanical Engin Vol.229 No.12

<P>The interface between piston ring and cylinder liner is lubricated with an oil film to improve wear resistance and operating life of the engine. The high combustion pressure, variable loadings, manufacturing errors, and thermal distortions in the engine cylinder deform the cylinder liner, thus making a significant effect on the lubricant performance. To investigate the effects of cylinder liner deformation on the piston ring lubrication, a 2D model of elastohydrodynamic lubrication under fully flooded conditions was considered. Various elliptically deformed profiles of the cylinder liner were tested to evaluate conformability, lubricating film thickness, friction, power loss, and lubrication flow rate for a complete four-stroke engine cycle. Comparative analysis of the simulation results was conducted to evaluate the dependency of engine performance on deformed bore shape. Results showed that the lubricating film thickness and engine performance parameters strongly depend on the cylinder liner shape and the degree of distortion.</P>

Lubrication Characteristics Between the Vane and the Rolling Piston in a Rotary Compressor Used for Refrigeration and Air-Conditioning Systems

Jung, Jae-Youn,Oh, Seok-Hyung,Cho, Ihn-Sung The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.5

The rolling piston type-rotary compressor has been widely used for refrigeration and air-conditioning systems due to its compactness and high-speed operation. The present analysis is part of a research program directed toward maximizing the advantages of refrigerant compressors. The study of lubrication characteristics in critical sliding components is essential for the design of refrigerant compressors. Therefore, theoretical investigation of the lubrication characteristics of a rotary compressor used for refrigeration and air-conditioning systems was studied. The Newton-Raphson method was used for the partial elastohydrodynamic lubrication analysis between the vane and the rolling piston of a rotary compressor. The results showed that the rotational speed of a shaft and the discharge pressure significantly influence the friction force and the energy loss between the vane and the rolling piston.

롤러 프로파일링을 고려한 박용 디젤기관 캠-롤러사이의 탄성유체윤활해석

구영필,조용주 한국마린엔지니어링학회 2000 한국마린엔지니어링학회지 Vol.24 No.6

A numerical procedure to analyze 3-dimensional elastohydrodynamic lubrication was applied on the cam-roller contact of the valve mechanism for a marine diesel engine. Both the pressure distribution and the film thickness between the cam and roller follower were calculated for each time step of the whole cycle. The pressure spike is shown at the outlet of the roller edge and it is getting higher as the external load is increased. An effective profiling method for the roller edge was suggested using the results of elastohydrodynamic lubrication analysis and the peak pressure was removed completely with the new profiling.

Development of Algorithm for 3D Mixed Elasto-Hydrodynamic Lubrication Analysis

조용주,김태완 한국정밀공학회 2011 International Journal of Precision Engineering and Vol.12 No.6

In this study, new 3-dimensional mixed lubrication algorithm is developed. For a converged solution of the mixed lubrication problem, the asperity contact pressure is calculated for the amount of asperity contact occurred due to insufficient lubricant pressure, then the procedure adding the asperity contact pressure to the hydrodynamic pressure is continually iterated until the further asperity contact amount does not occur. This algorithm has advantage that the pressure and the film shape can be calculated from Reynolds equation for all mixed lubrication region without any specific boundary condition for edge of asperity contact region. In order to investigate usefulness of this algorithm, we conducted the mixed lubrication analysis for the spherical contact with a single asperity and a rough surface and showed that the developed algorithm gives a stable convergent solution even in which severe contact takes place due to asperity height being considerably large.