Biotribology of artificial hip joints

Table 4 Theoretical estimation of the lubrication regime according to equation (17)

Head/cup	hmin (μm)	Ra (μm)	λ	Lubricationregime
MoP	0.065-0.144 (0.105)	0.1-2	0.1-1	Boundary to Mixed
CoP	0.076-0.107 (0.092)	0.1-2	0.05-0.9	Boundary to Mixed
MoM	0.020-0.061 (0.041)	0.014-0.071	0.6-2.9	Boundary to Mixed
MoMRHR	0.082-0.049 (0.066)	0.014-0.071	0.9-4.6	Boundary to Fluid-film
CoC	0.035-0.045 (0.04)	0.0014-0.0071	5.7-28.3	Fluid-film

The range of h_min is obtained considering two geometrical cases extracted from Table 1: minimum D_h combined with lowest Cl; maximum D_h combined with higher Cl. The averaged h_min reported in the bracket is used for calculating λ. Test case: W = 2 kN, ω = 2 rad/s, μ = 2.5 mPas.