Mathematical model of the energy absorbing stitch brake used in via ferrata climbing

Via ferrata climbing become more and more popular, but currently no appropriate safety equipment is available for lightweight climbers. The only criterion to get a safety certification for an energy absorbing system is to fulfill the safety requirements specified in European standard EN 958 for an 80 kg mass. But in case of a fall, the braking force which is necessary to full the existing European standard results in high decelerations on lightweight users. Therefore a modification of the standard had to be carried out. The goal of this study was the development and validation of a mathematical model of the energy absorbing systems for analyzing injury risks for lightweight people. A model of the energy absorption technology was developed using the multi-body simulation software SIMPACK. In tension the force element starts with a reversible deformation and switches to irreversible deformation when a maximum elastic force is reached. During the rebound only the elastic deformation is reversed whilst the plastic deformation remains. For the validation of the model comparisons with experimental tests according to standard EN 958 were carried out using iron masses of 34 kg, 48 kg, 77 kg and 80 kg. The simulation results showed a good accordance with the experimental data, e.g. the irreversible deformations differ with 9.5 % for 34 kg, 1.6 % for 48 kg, 5.1 % for 77 kg and 3.3 % for 80 kg. With the developed model realistic falling situations will be analyzed and an optimization of the safety equipment with a modification of the standard can be established.