angle 4 and the uncertainty of the inclination angle, u(4), has to be made. A reasonable
value for potential visual misalignment when placing a one inch disk sample into a set
screw is assumed to be around 0.035 radians. For this reason a value of 0.035 radians is
used for both <4 and u(4)). The influence of varying the value of 4 on the value of the
uncertainty in the friction coefficient is addressed in Appendix E, but for this analysis a
value of 0.035 radians is used for all calculations.
4.3.3.2 (gf'): Tribometer reported friction coefficient
The tribometer reported forward sliding friction coefficient is determined from the
ratio of the horizontal and vertical forces read by the tribometer.
,f = eqn 4.38
Fv
The variance in f' can be found using eqn 4.39.
u2. (.)=u2(FH) P J+u2(Fv)[.] eqn 4.39
The evaluated partial derivatives in eqn 4.39 are expressed in eqns 4.40 and 4.41.
/.I', 1 9/.' F,,
F =F F Fff eqns 4.40,4.41
4.3.3.3 (p): Roll misalignment angle
The sample roll misalignment angle P was established in eqn 4.31 to be a function
of the forward and reverse horizontal forces (FHf, Far) and vertical force (Fv) read by the
tribometer.