Abstract
To calculate more exactly the value of side force of pneumatic tire on the theory of E. Fiala, the applicability of the new theoretical equation which was expanded under the assumptions that the coefficient of friction increased linearly with the deflection of tire to the coefficient of maximum friction (f) in the adhision zone of contact patch of tire and turned to the coefficient of dynamic friction (μ) soon after moving into slip zone, was investigated on smooth and agricultural tires.
Main results are as follows;
1. The relations between side force (S) and side slip angle (β) are assumed as follows;
When 0≤β<βn,
S={Ctanβ-C2/3f(2-μ/f)tan2β+C3/27f2(3-2μ/f)tan3β}W
and when βn<β≤90°, S=μW,
where, βn=tan-1(3f/C),
and C is a factor of cornering coefficient. Using the chi-square criterion, the hypothesis that the side force calculated with these assumptions is equal to the experimental value acceptable at a level of 0.01.
2. As the dynamic frictional resistance of tire is directional and is indicated by the half length of the diameter of elliptical shape, experimental value is evaluated on the values of side force calculated by the upper equation on both circle and ellipse of friction. From the results of these calculations, it is recognized that the method by the ellipse of friction is more suitable than another for the agricultural tire, though it is slightly better for the smooth tire.
3. The values of f and μ, obtained from the results using a least squares method become larger with the increase of tire inflation pressure and with the dicrease of supporting weight of tire, respectively. The value of C becomes smaller with the increase of supporting weight of tire.
