A small wheel load causes a number of the originally radially directed tread elements to assume a vertical orientation. At zero wheel load, S lies at road level or a little lower (due to air and bearing resistance which slows the wheel down at the expense of some slip). The transition point, at which the crack turned from Stage 1 to Stage 2, occurred at a distance of approximately L/2, thus giving a physical interpretation to the critical distance.įigure 8.14 tries to explain the observation regarding the location of the slip point S: possible locations have been indicated. In general, the initial Stage I growth occurred on the plane of maximum shear stress, whilst the Stage 2 growth coincided with the direction of maximum normal stress. Examination of the specimens showed clear evidence of the two classic stages of crack growth ( Fig. The conventional PM approach was slightly less accurate, with some predictions falling outside the 20% error band. We found that both the LM and the PM/S–L approaches gave good predictions – within 20% of the experimental fatigue limits in all cases. Our procedure was to make predictions at all points on the arc, choosing the prediction which gave the lowest fatigue limit. For example, in using the PM the ‘correct’ point could lie anywhere on an arc of radius L/2 (see Fig. The direction in which to draw the line for the analysis is not obvious. Apparently, the motorcycle tire with narrow contact patch is much less sensitive to this effect. This distance between the line of action of F x and the wheel center plane is suspected to vary due to local road camber variations and possibly tire nonuniformities while the tire rolls. This is supposedly due to the large direct contribution of the braking force times the moment arm. The diagrams concerned, in Figures 4.29 and 4.32, show a rather unpredictable variation of the moment while the brake pressure is increased until wheel lock is reached. An exception is the attempt to (physically) describe the measured course of the aligning torque at braking (except for the motorcycle tire). In general, it is observed that good agreement between computed and measured curves can be achieved with the model. Magic Formula-computed results compared with data from measurements conducted with the TNO test-semi-trailer, equipped with large camber test device (cf. Aligning torque characteristics of a 180/55ZR17 motorcycle tire.

Mirc 7.41 key