The S-N curve in fatigue testing shows the relationship between:

Explanation:

Fatigue Testing and the S-N Curve

Definition: Fatigue testing is a method used to determine the durability and lifespan of a material under cyclic loading conditions. It is crucial in predicting how a material will behave when subjected to repeated stress or strain over time. The S-N curve, also known as the Wöhler curve, is a graphical representation that illustrates the relationship between the stress amplitude (S) and the number of cycles to failure (N).

Working Principle: During fatigue testing, a sample material is subjected to repeated cyclic loading until failure occurs. The stress amplitude and the number of cycles to failure are recorded. This data is then used to plot the S-N curve, where the x-axis represents the number of cycles to failure (N) on a logarithmic scale, and the y-axis represents the stress amplitude (S).

Correct Option Analysis:

The correct option is:

Option 2: The number of cycles and stress amplitude

This option accurately describes the S-N curve in fatigue testing. The S-N curve shows the relationship between the number of cycles to failure (N) and the stress amplitude (S). The curve typically displays how the material's endurance limit or fatigue limit is determined, which is the stress level below which the material can endure an infinite number of cycles without failing.

The S-N curve is critical for engineers and designers to understand the fatigue behavior of materials and to ensure the reliability and safety of components subjected to cyclic loading in various applications, such as in automotive, aerospace, and structural engineering