$a_l$	Effective depth of heat penetration ($\mathrm{m}$)
$A_a$	Area of the nominal contact region (${\mathrm{m}}^2$)
$c_l$	Specific heat ($\mathrm{J}{\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$)
$f$	Coefficient of friction (dimensionless)
$J_k(\cdot )$	Bessel functions of the first kind of the k-th order
$k_l$	Thermal diffusivity (${\mathrm{m}}^2{\mathrm{s}}^{-1}$)
$K_l$	Thermal conductivity ($\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$)
$p$	Contact pressure ($\mathrm{Pa}$)
$p_0$	Nominal value of the contact pressure ($\mathrm{Pa}$)
$q$	Specific power of friction ($\mathrm{W}{\mathrm{m}}^{-2}$)
$q_0$	Nominal value of the specific power of friction ($\mathrm{W}{\mathrm{m}}^{-2}$)
$t$	Time ($\mathrm{s}$)
$t_i$	Time of the contact pressure increase ($\mathrm{s}$)
$t_s^0$	Stop time at braking with constant deceleration ($\mathrm{s}$)
$t_s$	Stop time ($\mathrm{s}$)
$T$	Temperature (${}^{\circ }\mathrm{C}$)
$T_a$	Initial (ambient) temperature (${}^{\circ }\mathrm{C}$)
$V$	Velocity ($\mathrm{m}{\mathrm{s}}^{-1}$)
$V_0$	Initial velocity ($\mathrm{m}{\mathrm{s}}^{-1}$)
$W_0$	Initial kinetic energy of the system ($\mathrm{J}$)
$x,y,z$	Spatial coordinates ($\mathrm{m}$)
lower $l$	Number of the main ($l=1$) and frictional ($l=2$) elements of the friction pair
${\gamma }_l^{}$	Parameter of material gradient (${\mathrm{m}}^{-1}$)
${\gamma }_l^{*}$	Parameter of material gradient (dimensionless)
${\mathsf{\Theta }}_l$	Temperature rise (${}^{\circ }\mathrm{C}$)
${\mathsf{\Theta }}_l^{*}$	Temperature rise (dimensionless)
${\mathsf{\Theta }}_0$	Temperature scaling factor (${}^{\circ }\mathrm{C}$)
${\rho }_l$	Density ($\mathrm{kg}{\mathrm{m}}^{-3}$)
$\tau$	Time (dimensionless)
${\tau }_i$	Time of contact pressure increase (dimensionless)
${\tau }_s^0$	Braking time at constant deceleration (dimensionless)
${\tau }_s$	Braking time (dimensionless)
$\zeta$	Spatial coordinate in axial direction (dimensionless)