What is fatigue? Fatigue is any mechanism that reduces the performance of a rope over time in service. This can be abrasion, UV damage, creep, bending fatigue or one of many lesser causes. This article will focus particularly on bending fatigue of high-performance Dyneema cored ropes.
As modern rope covers are getting more durable, including the increased availability of high-performance blends, they are lasting longer. Also more applications are appearing on boats that place ropes under higher loads and perhaps over smaller sheaves. All this results in fatigue becoming more relevant to sailors, riggers and boat designers than ever before.
A rope is made up of twisted yarns and each yarn contains hundreds of filaments. Every time a rope is flexed the fibres slide across one another, causing the filaments to abrade and eventually to break, thus reducing the strength of the rope. This is a cumulative process and if unchecked the rope will eventually have a strength less than the working load, resulting in an in-service failure. Read on.
Inappropriate title thanks to Linkin Park.