Experimental Study on the Transition between Static and Kinetic Frictions of Steel/Shale Pairs

Table 3

Values of D_c for different materials [36, 38].

Materials	Un-/lubricated			()	Ref.
Mild steel on copper	Unlubricated	0.54	0.39	0.9	Rabinowicz, [35]
	Lubricated	0.58	0.40	0.7
Mild steel on titanium	Unlubricated	0.63	0.45	6.0
	Lubricated	0.61	0.45	5.0
Acrylic on wood	Unlubricated	0.3	0.06	290.0	Mendez and Miguel [36]
Wood on wood	Unlubricated	0.2	0.07	420.0
Steel on shale	Unlubricated	0.51	0.41	160.3	This paper
	Lubricated	0.144	0.13	2.19