Ermüdungsgrenzen

Ermüdungsgrenzen refer to the stress level below which a material can withstand an indefinitely large number of loading cycles without experiencing fatigue failure. This concept is primarily relevant for metallic materials. When a material is subjected to repeated or fluctuating loads, even if these loads are below its static yield strength, microscopic cracks can initiate and propagate. Over time, these cracks can grow until the material loses its load-bearing capacity and fails suddenly and often catastrophically. The fatigue limit, or endurance limit, represents the threshold stress below which this fatigue crack growth is arrested.

For some materials, particularly steels and titanium alloys, a distinct fatigue limit exists. Below this stress level, the material can theoretically endure an infinite number of cycles. However, for many other materials, such as aluminum alloys and composites, a true fatigue limit is not observed. Instead, these materials exhibit a fatigue strength, which is the stress level at which failure occurs after a specified number of cycles, commonly one million or ten million cycles. As the stress level decreases, the number of cycles to failure increases.

The determination of fatigue limits and strengths is crucial in engineering design to ensure the safety and longevity of components subjected to cyclic loading, such as in aircraft structures, automotive parts, and bridges. Fatigue life prediction models are used to estimate the expected service life of a component based on its material properties and the anticipated loading conditions. Understanding and accounting for fatigue is paramount in preventing premature failures and ensuring structural integrity.