Hardness Effect on Three-Body Abrasive Wear Under Fluid Film Lubrication

Abstract

Under fluid film lubrication, the particulate contaminants in the fluid cause three-body abrasive wear on critical surfaces. The wear not only depends on the hardness of the wearing surface (Hj), but also on the hardnesses of its opposing surface (Hb) and the involved abrasives (Ha). In this paper, the hardness effect, particularly the relationships among these three hardnesses, is studied, by exploring the interdependence between two hardness ratios: the ratio between two rubbing surfaces (Hb/Hj) and the ratio between the surface to be protected (usually the harder surface) and the abrasives (Hj/Ha). Three types of journal-bearing pairs (Hb/Hj = 0.75, 0.6, and 0.3) were tested, subjected to four abrasive particles (Hj/Ha ranges from 0.14 to 2.75). The wear linearly varies with the Hj/Ha value at each metal hardness ratio on log-log diagram. The empirical constants in the wear function are obtained. The critical hardness ratio and the wear coefficient are also analyzed.

Tribological properties of epoxy nanocomposites

“…It was noticed that the wear rate of the three-body abrasion was sometimes 10 times lower than that of two-body wear [8]. Most analyses assumed that the apparently reduced wear rate resulting from three-body abrasion is caused by a rolling effect of the particles which strongly depends on the particles' size, shape, as well as the hardness and sliding conditions of the material pairs [13,[15][16][17][19][20][21][22][23]. The favourable benefit of the rolling effect is mainly attributed to following two items: (i) the remarkable reduction of the frictional coefficient, and (ii) the spontaneous restriction of the grooving/cutting wear by hard particles.…”

Strain-rate effects on the plastic indentation and abrasion of elastohydrodynamic contacts by debris particles

“…A yield stress at the reference strain rate _ " 0 B pre-exponential factor at the reference strain rate _ " 0 c specific heat capacity C strain-rate factor D initial spherical-particle diameter E elastic modulus E p elastic modulus of the particle E 1 , E 2 elastic moduli of the contact solids g strain-gradient coefficient G shear modulus G p shear modulus of the particle h contact gap height ( Figure 1) " h 1 , " h 2 micro-hardnesses of the contact solids at average local temperature (equation (7)) h c central film thickness in the absence of the particle H height of a particle block ( Figure 1) H p dynamic hardness of the particle (equation (9)) H ð0Þ p nominal, cold hardness of the particle H 1 , H 2 cold macro-hardnesses of the contact solids i, j discrete coordinates of a particle block K f thermal conductivity of the lubricant at bulk temperature f K x , K y , K z principal thermal conductivities of a contact solid m thermal-softening exponent n strain-hardening exponent Nu surface-length Nusselt number p contact pressure on a particle block p f local fluid static pressure ( Figure 1) q thermal power of frictional heating (equation (10)) q b thermal power transmitted by a peripheral block to the lubricant during one time step (equation (12)) q c thermal power transmitted by a surface sector to the lubricant (equation (13)) q p thermal power generated at the core of a particle block (equation (11)) r effective radius of spherical indenter (equation (8)) R radius of the deforming particle disc (Figure 1) t time u 1 , u 2 tangential velocities of the contact surfaces ( Figure 1) u 1 , u 2 magnitudes of the tangential velocities of the contact surfaces U, V, W thermoelastic displacements (equation (14)) V extr particle extrusion velocity (equation (4)) V M speed of the particle in relation to a contact surface V x , V y local tangential velocities (equation (3)) w 1 , w 2 normal surface displacements w e ð Þ 1 , w e ð Þ 2 normal elastic displacements of the contact surfaces w ðrÞ 1 , w ðrÞ 2 local indents of the contact surfaces x, y, z spatial coordinates ( Figure 1) x b , y b continuous coordinates of a particle block x M , y M coordinates of particle's centre (Figure 1) Y 0.2%-offset yield strength Y p yield stress in uniaxial compression of the particle thermal expansion coefficient 1 , 2 local, normal plastic displacements of the contact surfaces (equation (17)) Áh approach of the contact solids during a time step Ás dimension of a particle block (Figure 1 -bottom) Át time step Á temperature change (equations (15) and (16)) "…”

The effect solid particle lubricant contamination on the dynamic behavior of compliant journal bearings

“…Some of the noteworthy research works in this area are as follows. Xuan et al examined the hardness effect on 3 body abrasive wear under fluid film lubrication using a journal bearing wear specimen, and discussed the effect of hardness ratios and wear coefficient. Broeder and Heijnekamp presented measurements of worn shaft and bush surfaces as well as friction torque.…”

“…Xuan et al established that in addition to the hardness ratio of the shaft and liner, the hardness of the abrasive contaminant should also be taken into consideration. They introduced a ratio of the contaminant hardness to that of the surface to be protected.…”

“…Again, the embedding mechanism of an abrasive contaminant in the liner, which, in turn, abrades the shaft was thought to be responsible for this phenomenon. Xuan et al 15 established that in addition to the hardness ratio of the shaft and liner, the hardness of the abrasive contaminant should also be taken into consideration. They introduced a ratio of the contaminant hardness to that of the surface to be protected.…”