The Role of Elastohydrodynamic Lubrication in Rolling-Contact Fatigue

Abstract

The five-ball fatigue tester was used to determine the rolling-contact fatigue life of 1/2-inch-diameter M-1 steel balls with four lubricants at 300 deg F. Film thickness measurements were made with the rolling-contact disk machine under simulated five-ball test conditions. Under certain conditions, elastohydrodynamic lubrication was found to exist at initial maximum Hertz stress levels up to 800,000 psi. There appears to be a correlation among the following variables: Plastically deformed profile radius of the ball specimen at ambient temperature; lubricant type; and rolling-contact fatigue. No correlation was found between contact temperature obtained with different lubricants and fatigue life.

NASA Five-Ball Fatigue Tester—Over 20 Years of Research

“…It was reported in [14,15] that plastic deformation can reduce the contact stress as much as 10 percent at theoretical maximum hertz stress levels between 4.10 and 5.52 GPa (600,000 and 800,000 psi) in the five-ball fatigue tester. Therefore, where plastic deformation does occur under rolling contact, the calculated Hertz stress may only be approximate [14,16] [17,18] and summarized in Fig.…”

“…While it may be difficult, although not impossible, to predict actual bearing life [59] from them, or based on them, bench-type fatigue tests, such as those run in the NASA five-ball fatigue tester, can rank material, lubricant, or operating variables on a relative life basis [5,[14][15][16][17][18]36]. This is illustrated in Fig.…”

An Intelligent Assessment Method of Contact Fatigue Reliability for Rolling Bearing under EHL

“…However, due to the function of lubricant in the actual working condition, a ball is separated from raceway by oil film thickness, which reduces wear and prolongs fatigue life that has exponential relation with the EHL film thickness [2,6,18,20]. Therefore, it is necessary to consider the influence of the EHL on contact fatigue reliability of rolling bearing.…”

Rolling-Element Fatigue Testing and Data Analysis—A Tutorial

“…It was found that the resultant Hertz stress is not only affected by the applied load, material hardness and structure but also by the elastohydrodynamic film formed (Ref. 14). For many applications where gross plastic deformation occurs, it is necessary to calculate the effective Hertz stress or the contact stress after plastic deformation occurs (Ref.…”