Fatigue tests are experiments designed to assess how materials or structures behave under repeated loading and unloading cycles. These tests help determine the durability and lifespan of components, such as those used in automobiles, aircraft, and bridges. By simulating real-world conditions, engineers can identify potential failure points and improve design safety. During a fatigue test, a sample is subjected to controlled stress levels over many cycles until it fails. The results provide valuable data on the material's fatigue limit, which is the maximum stress it can endure without breaking. This information is crucial for ensuring the reliability of various engineering applications.