Ermüdungskonzepte

Ermüdungskonzepte, often translated as fatigue concepts, refers to the theoretical frameworks used to understand and predict the failure of materials under repeated or cyclic loading. This phenomenon, known as fatigue, occurs when a material weakens and eventually fractures due to the cumulative effect of these stresses, even if the applied loads remain below the material's static yield strength.

Several key concepts underpin the study of material fatigue. One fundamental idea is the S-N curve, also known as the Wöhler curve, which plots the stress amplitude (S) against the number of cycles to failure (N). This curve illustrates that higher stress amplitudes lead to fewer cycles before failure, and conversely, lower stress amplitudes allow for a greater number of cycles. Another crucial concept is the fatigue limit or endurance limit, a stress level below which a material can theoretically withstand an infinite number of load cycles without failing. Not all materials possess a distinct fatigue limit; some, like certain steels, do, while others, like aluminum alloys, exhibit a fatigue strength that continues to decrease with increasing cycles.

Crack initiation and propagation are central to understanding fatigue. Under cyclic loading, microscopic flaws or stress concentrations on the material's surface or within its bulk can develop into small cracks. These cracks then grow incrementally with each load cycle, a process known as crack propagation. Eventually, when the crack reaches a critical size, it can lead to rapid fracture of the remaining material. Fatigue damage is often described as a cumulative process, meaning the damage incurred at each cycle adds up over time. This cumulative nature makes it challenging to predict fatigue life accurately, as various factors like surface finish, environmental conditions, and the presence of defects can significantly influence the material's behavior.