On the behavior of slackline webbings under dynamic loads and the simulation of leash falls

Abstract

Slackline is a new and rapidly expanding sport, which has had minimal research published on it in terms of sport physics and engineering. Slackline dynamics strongly depend upon the elastic response of used webbing, typically made of polyester or nylon. Depending on the stress and strain rates applied, polymers are known to exhibit a visco-elastic behavior characterized by hysteresis effects. Through a series of carefully executed experiments, this study examined the behavior of slackline webbing under dynamic loads to determine the departures from the respective static response (stress–strain curves). Such knowledge is fundamental for the accurate simulation of slackline dynamics, so as to predict peak forces and aid safe rigging. The results demonstrate that the effective modulus during leash falls was significantly higher than the slope of the respective stress–strain curve, indicating a stiffer response. Also, the effective modulus increased with the applied pretension. Using the moduli determined experimentally for the rigged slacklines with different types of webbing, the respective leash falls were simulated numerically with high accuracy. A standardized test is proposed, to be adopted by the International Slackline Association and slackline webbing manufacturers, is proposed in order to provide key information on the response of each webbing available in the market under typical dynamic loads, similar to the “impact force” test designed for dynamic ropes by the International Climbing and Mountaineering Federation.