Mechanical and thermal properties of the contacting materials.

	E (GPa)	ν (—)	ρ (kg m−3)	κ (W m−1 K−1)	C p (J kg−1 K−1)
Steel ball	210	0.3	7850	46	470
Glass disc	81	0.208	2510	1.114	858
Sapphire disc	360	0.34	4000	40	750