Modeling on contact fatigue under starved lubrication condition

The lubrication performances of cycloid drives affect the dynamic characteristics, the mechanical efficiency and the contact fatigue behavior of the system. To maintain tranmission precision it is required to minimum the times of disassebly, hence grease lubrication is often applied where starvation might occur in service. Starved lubrication performance of a cycloid gear drive is studied using a numerical finte line starved-elastohydrodynamic lubrication model. The parameter of the inlet oil film thickness is chosen to represent the starved status. Effects of the inlet film thickness on the centralfilm thickness, the friction coefficient and the frictional power loss are investigated. In addition, effects of different shape of inlet oil-supply layer in the same starved degree on lubrication performance are studied. Under the same inlet oil supply volume, the convex type profile would present a better oil film within the nominal contact zone compared with other four different shapes of the inlet film supply.

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A tribological analysis on stuffing box-piston rod system of low-speed marine diesel engines

International Journal of Engine Research ◽

10.1177/1468087418796615 ◽

2018 ◽

Vol 20 (8-9) ◽

pp. 911-930 ◽

Cited By ~ 4

Author(s):

Rui Li ◽

Xianghui Meng ◽

Youbai Xie

Keyword(s):

Film Thickness ◽

Diesel Engines ◽

Oil Film ◽

Low Speed ◽

Rod System ◽

Marine Diesel ◽

Ring Location ◽

Lubrication Condition ◽

Ring Pack ◽

Starved Lubrication

The stuffing box-piston rod system is widely used in the low-speed marine diesel engines to scrape oil and ensure sealing. Its friction power loss and wear rate are great, but the studies about the system are very limited. In this study, based on the special structure and working conditions of the stuffing box, the analytical model for the tribological properties of the stuffing box-piston rod system is developed considering the oil starvation and relative ring location effects. The minimum oil film thickness, friction, oil transportation, and asperity contact are calculated for the stuffing box. The analysis results show that compared with the fully flooded lubrication, the minimum oil film thicknesses of the rings reduce significantly in the middle of the strokes under the starved lubrication condition, but the friction losses of the rings are influenced by the comprehensive effects of the oil film thickness reduction and lubricating area reduction under the starved lubrication condition, which is related to the specific profiles of the rings. In addition, compared with the engine piston ring pack, the relative ring location effect is more obvious in the stuffing box ring pack because there are more rings and the ring intervals are larger. The relative ring location effect makes the minimum oil film thicknesses, friction forces, and asperity contacts of the rings have oscillations after bottom dead center and top dead center.

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Effect of neighboring-microstructure on the rolling contact fatigue around non-metallic inclusion

MATEC Web of Conferences ◽

10.1051/matecconf/201816504015 ◽

2018 ◽

Vol 165 ◽

pp. 04015

Author(s):

Izumi Shimoji ◽

Masahide Natori ◽

Hideyuki Hidaka ◽

Yuji Miyamoto

Keyword(s):

Rolling Contact Fatigue ◽

Contact Fatigue ◽

Rolling Contact ◽

Bearing Failure ◽

Metallic Inclusion ◽

Steel Making ◽

Bearing Life ◽

Improvement Method ◽

Life Improvement ◽

Lubrication Condition

It is well known that the flaking of a raceway causes the bearing failure, and the flaking mechanism depends on the lubrication condition. In the case of ideal lubrication condition with sufficient oil film thickness, the flaking originates from a non-metallic inclusion at the subsurface. It occurs through the formation of butterfly structure due to stress concentration around the inclusion. Therefore, the countermeasure of this type of flaking is to make cleaner steel by the reduction of inclusions. However, further reduction of inclusion imposes an extra challenge for the current steel making process. Therefore, in this paper, the effect of neighbouring microstructure on the butterfly structure is evaluated to propose a new life improvement method for rolling contact fatigue. It was suggested that it’s important to eliminate strain localization near inclusion for improving bearing life.

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Rolling Contact Fatigue Type Analysis of Rolling Bearing by XRD and TEM

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.1679 ◽

2012 ◽

Vol 706-709 ◽

pp. 1679-1684 ◽

Cited By ~ 1

Author(s):

H. Hidaka ◽

Kouji Ueda ◽

N. Mitamura

Keyword(s):

Film Thickness ◽

Fatigue Test ◽

Retained Austenite ◽

Ball Bearing ◽

Rolling Contact Fatigue ◽

Contact Fatigue ◽

Rolling Bearing ◽

Microstructural Change ◽

Rolling Contact ◽

Lubrication Condition

In the rolling bearing, the flaking caused by rolling contact fatigue is classified into two types: surface originated flaking and subsurface originated flaking. It has been recognized that marked microstructural change can occur in subsurface originated flaking due to rolling contact fatigue. But there are few reports in surface originated flaking about microstructural change. In this study, surface originated flaking caused by rolling contact fatigue was investigated based on microstructural change. Thrust ball bearing and radial ball bearing was used for fatigue test. Simulation of dent originated flaking was carried out using the bearing with artificial dent. Another fatigue test subjected to surface originated flaking was done under shortage of oil film thickness lubrication condition. Microstructural change was measured by X-ray Diffractmetry (XRD) and Transmission Electron Microscopy (TEM) during fatigue testing. Microstructure of bearing steel used for fatigue test is consisted of martensite with small amount of retained austenite. XRD measurement reveals that the half peak width of martensite and volume fraction of retained austenite decreasing with increasing testing time, and the amount of decrease in these parameter were small in the surface originated flaking compared with subsurface originated flaking when the specimens were flaking. This suggests that surface originated flaking occurs in spite of mild microstructural change. TEM observation about the surface originated flaking shows plastic flow in the surface layer. Especially, it was confirmed that partial recrystallization occurs in the fatigue test under shortage of oil film thickness lubrication condition. But it was also confirmed that degree of recrystallization is lower in the surface originated flaking than subsurface one, and this reasonably explains XRD result. From these results, it was cleared that recrystallizaiton of martensite is differ in degree but not in kind between surface originated flaking and subsurface originated flaking.

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Predicting Fatigue Life for Finite Line Contact under Starved Elastohydrodynamic Lubrication Condition

Mathematical Problems in Engineering ◽

10.1155/2020/5928621 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Mingyong Liu ◽

Haofeng Ku ◽

Jinxi Zhang ◽

Peidong Xu ◽

Chenhui Wu

Keyword(s):

Fatigue Life ◽

Contact Fatigue ◽

Elastohydrodynamic Lubrication ◽

Operating Conditions ◽

Line Contact ◽

Finite Line Contact ◽

Lubrication Performance ◽

Finite Line ◽

Lubrication Condition ◽

Lubrication Characteristics

Surface contact fatigue is the main failure mode in many mechanical components, such as gears, bearings, and cam-followers. A fatigue life prediction model is proposed for finite line contact under starved thermal elastohydrodynamic lubrication (TEHL) condition in this paper. Then, the effects of inlet oil-supply thickness, slide-to-roll ratio (SRR), and operating conditions on the lubrication performance and fatigue life are investigated. The results show that the lubrication characteristics and fatigue life of finite line contact are obviously different from those of fully flooded situation by introducing the starved lubrication condition. For example, the severe starved conditions lead to a significant increase in friction coefficient and decreased fatigue life. The variation of SRR has an important influence on the fatigue life. With the increase of SRR, the fatigue life decreases firstly and then increases. The stress concentration occurs near the surface when speed is low. In addition, under the low-speed situation, rotation speed variation has little effect on the fatigue life.

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