Definition - What does Fatigue Strength mean?
The fatigue strength of a material is defined as the highest stress value that a material can be subjected to for a specified number of cycles without resulting in failure. This term should not be confused with fatigue limit, which describes the stress value below which a material can endure an infinite number of stress cycles.
Fatigue strength is typically used for non-metallic materials (such as plastics), which do not have a well-defined fatigue limit.
Trenchlesspedia explains Fatigue Strength
Fatigue strength is a key property (alongside other parameters such as impact strength, flexural strength, stiffness, abrasion resistance, ease of repair etc.) used in the selection of appropriate pipe materials for specified trenchless applications.
Fatigue is generally a cause for concern and a limiting factor in PVC (Polyvinyl chloride) pipes in potable water systems. In this application, fatigue is most commonly caused by pressure surges from rapid change in liquid velocities in the pipeline due to rapid valve closure or pump triggering. In contrast, HDPE (High-density polyethylene) pipes are flexible and ductile making them highly resilient to fatigue loading due to surge events that are common in potable water distribution systems.