Fatigue analysis is crucial in engineering to predict and enhance the lifespan of materials under cyclic loading. The following are the primary methods used in fatigue analysis: Stress-Life Method (S-N Curve): The S-N curve is a traditional method that involves plotting the material's stress amplitude against the number of cycles to failure. The S-N curve method is suitable for high-cycle fatigue analysis where the stresses are within the elastic range. Strain-Life Method (ε-N Curve): This approach is used for low-cycle fatigue analysis where the stress levels are high enough to cause plastic deformation. It involves plotting the strain amplitude against the number of cycles to failure. Fracture Mechanics Method: The fracture mechanics method is used to predict the growth of pre-existing cracks under cyclic loading. It's particularly useful for structures with crack-like defects and is based on principles from fracture mechanics. Fatigue Crack Growth Rate (da/dN vs. ΔK): This technique focuses on the rate at which an existing crack grows per loading cycle as a function of the stress intensity factor range (ΔK). It's crucial for predicting the remaining life of a cracked component. Multiaxial Fatigue Analysis: This approach is used when the stress state is complex, involving multiple directions. It requires more sophisticated models to predict failure, such as the critical plane approach. Energy Methods: These methods, such as the hysteresis energy approach, consider the energy absorbed in a material during cyclic loading as the primary driver for fatigue damage. Finite Element Analysis (FEA): FEA is a computational tool to predict stress, strain, and displacement of materials and structures under load. Combined with fatigue life models, it helps identify critical locations and estimate fatigue life. Each method has its specific applications, advantages, and limitations, and the choice of method depends on the type of material, the nature of the cyclic loading, and the available data.