Fatigue is among the most important factors in the long-term performance of metallic materials. Cycling of stress tends to initiate microscopic cracking and eventual fracture even when stress levels remain well below the yield strength of the material. ASTM E468 standard practice defines methods for reporting results of constant amplitude fatigue tests so that engineers and researchers can produce and interpret S–N (stress-life) curves in a uniform method. By standardizing reporting techniques, it guarantees consistency between laboratories and industries, hence the reliability of fatigue data for design increases.
ASTM E468 Test Method
| Stress Application | Repeated constant amplitude loading cycles are applied to metallic specimens until failure or a predetermined cycle limit is reached |
| Data Representation | Results graphed as stress amplitude or maximum stress against number of cycles to failure (S–N curve) |
| Fatigue Life Definition | The number of cycles a specimen will endure prior to fracture under the prescribed constant amplitude loading |
