Samenvatting

This paper presents the results of a study regarding the cyclic bending over sheave fatigue life of five different type of small diameter cables (d <=2.5 mm) in a simple bending test around a D = 10 mm sheave. The goal of the study is to estimate the lifespan of cables in prosthetic applications. Three fiber cables (Dyneema®) and two steel wire cables were subjected to a tension of 150 N for all cables and a normalized tension of 20 N/mm2 for each individual cable, number of cycles to failure was recorded. None of the cables that were in this research withstood the limit of 50,000 bending cycles at a tension of 150N, which was stated as a minimum for prosthetic applications. Based on the data from tests performed at a normalized tension it is concluded that Dyneema® SK78 has superior performance compared to all other cables when the diameter is equal for all cables. The Dyneema® SK78 cable is therefore regarded as the cable most suited for usage in prosthetic applications, surviving a minimum of 31,826 cycles to failure. The steel wire cables with and without nylon coating show inferior cyclic bending over sheave fatigue life compared to all fiber cables. The steel cables survived 1100 and the nylon coated steel cables 3400 bending cycles to failure. Further research regarding the amount of active hand movements made by prosthesis users at a certain tension is needed for a more accurate estimation of the lifespan of these cables within prosthetic applications.