Fatiguetesting

Fatigue testing is a type of mechanical testing that determines how long a material, component, or structure can withstand cyclic loading before failure. It seeks to characterize fatigue life, typically expressed as the number of cycles to failure under a given stress level. Fatigue behavior is commonly divided into high-cycle fatigue (HCF) and low-cycle fatigue (LCF). Data are often summarized with stress–number of cycles (S–N) curves for metallic materials, and may be supplemented by alternative representations for nonmetals.

Tests use specimens subjected to cyclic loading in axial, bending, torsional, or multiaxial configurations. Methods include constant-amplitude and variable-amplitude loading, with rotating bending, axial tension–compression, four-point bending, and torsion among standard setups. Tests are performed at controlled frequencies and environments; temperature, corrosion, and surface finish influence results. Results are plotted as S–N curves, and analysis may employ damage accumulation rules such as Miner’s rule, or fracture mechanics approaches like crack-growth models when applicable.

Standards from organizations such as ASTM and ISO provide procedures for test methods, specimen geometries, loading profiles, data analysis, and reporting. Fatigue testing yields estimates of fatigue life, endurance limits or safety factors, and reliability bounds that reflect data scatter. Material quality, manufacturing processes, and surface treatments can significantly affect outcomes and should be documented.

Applications span aerospace, automotive, civil and mechanical engineering, energy, electronics, and medical devices. Fatigue testing supports material selection, design validation, fatigue life prediction, and certification. Limitations include the challenge of extrapolating lab results to real-world service conditions, the influence of environment and residual stresses, and the simplifications inherent in many fatigue models.