The Influence of Moving Dent on Point EHL Contacts

Abstract

A transient analysis for a dent passing through the conjunction of a point EHL contact was developed and solved numerically by w i n g the multigrid method. Results show that the presence of sliding produces a noticeable pressure ridge and t h w , a surface indentation at either leading side of the dent if the dent moves slower than the opposite surface, or at the trailing side if the dent moves faster than the opposite sutface. The pressure ridge and surface indentation extend their lengths fonoard or backward from the dent i n the sliding direction at a rate approximately half the sliding speed. The pressure jluctuution associated with the dent increases with increusing slideto-roll ratio a d dent depth, and decreases with increasing dent w d t h i n both x-andy-directions. The agreement between numerical simulation and experimental results obtained by Wedeven and Cusano ( 1 ) is r,emarkably close. a = Hertzian contact half width in x-direction b = Hertzian contact half width in y-direction co,cb = pressure-density coefficients U~X Ca,Cb = C, = c.Ph, Cb = cbPh non-dimensional parameters in density-pressure relationship E' = effective Youngs modulus G I = a l E 1 , Dowson material parameter GI = a2E1 Dowson material parameter G f = a1Ph GB = a2Ph h = film thickness H = Ma, non-dimensional film thickness ha = dent depth h, = central film thickness H, = h,1(2a), non-dimensional dent depth K, = bla, contact ellipticity ratio 1, = dent width in x-direction C, = dent width in y-direction L, = lxla & = hlb p = pressure P = PIPI, non-dimensional pressure pl = break pressure PI = p,/Ph non-dimensional break pressure Ph = nominal Hertzian pressure X. Y X Y a1 a2 rl 'lo = effective contact radius in x-z plane = effective contact radius in y-z plane 2(u1 -. U P ) ----, slide-to-roll ratio U I + UP = time = aLlu = ( U I + u2)12 = surface speeds = ( U P -u1)/2, sliding velocity of Surface 2 with respect to the dented surface 1 -l l o u --, 1)owson speed parameter E'R, = non-dimensional load at time instant i = load W ---13owson load parameter E'R:' = coordinates = xla, non-dimensional coordinate = ylb, non-dimensional coordinate = pressure-viscosity index = pressu1:e-viscosity index = lubricant viscosity = lubricant viscosity at inlet rl = -non-dimensional lubricant viscosity rlo = lubricant density = lubricant density at inlet P = -non-dimensional lubricant density PO

Effects of surface texture on journal-bearing characteristics under steady-state operating conditions

“…A considerable amount of publications have been devoted to EHL problems [7][8][9][10][11][12], where the surface geometric profiles, such as digitized rough surfaces and even measured real engineering surfaces, are involved in lubrication calculations. Only a limited amount of information is available on lubrication solutions for journal-bearing contact systems with real engineering surfaces [13][14][15].…”

Wind Turbine Tribology

“…Hard particles plough through and cut away surface material, leading to loss of clearance and rough surfaces accompanied by high friction Accelerated oil oxidation Catalytic surfaces of fresh metal wear debris accelerate oil oxidation, lead to acidity, oil thickening, and sticky fouling deposits The dynamic clearances between moving parts are on the order of 1 lm, which is the same dimension as many hard contaminant particles. Hard particles trapped in rolling contacts indent raceway surfaces creating raised metal shoulders that act as stress risers [85][86][87][88]. The pressure increase around a dent can surpass the normal Hertzian pressure.…”

Contact Fatigue Analysis of a Dented Surface in a Dry Elastic–Plastic Circular Point Contact

“…The effect of a dent on the EHL lubrication of a line or point contact was the subject of many investigations starting from late 70s, first experimentally [10][11][12][13] and later numerically [14][15][16]. Experimental and theoretical work on particle entrapment in the EHL conjunction, particle deformation and debris denting [17][18][19][20][21][22][23][24][25][26], and subsequent wear or fatigue life reduction [27][28][29][30][31][32][33][34][35][36][37][38] has then been a hot research topic and especially welcomed by leading bearing manufacturers and academia.…”