Rotational traction behaviour of artificial turf

Within artificial turf testing for player-surface interaction, traction is a key system property that needs to be measured for comfort, performance and injury risk. The purpose of this study was to modify a FIFA rotational traction test device to provide the full torque-angle time history and to use the modified device to compare the behaviour of five different football and rugby studs. A strain-gauge sensor and rotational sensor were incorporated to provide continuous measurement of the torque resistance and rotational angle throughout the rotation of the test disc. Data was collected on a standard laboratory made (3G) artificial turf surface. From the torque-angle plot, an initial high stiffness region followed by a lower stiffness region was identified and comparisons made between studs. In general, as stud length increased, the stiffness increased in both regions. Furthermore, as the stud length increased for both football and rugby studs there was a pattern of increasing peak torque but no clear trend for the peak angle. The actual foot rotation measured in subject testing is observed in general to be much smaller than the angular rotation required to produce the peak torque resistance from the mechanical testing, suggesting that the initial stiffness resistance behaviour may be a better indicator of the mechanisms involved in the traction mobilised by subjects.