-Environmental fatigue plays an important role in safety design, operation, maintenance, safety assessment, life prediction and life extension assessment. Considering the effects of temperature, dissolved oxygen and strain rate on the corrosion fatigue performance, the environmental fatigue design model was established. Combined with advanced microscopic analysis and characterization, the influence mechanism of different factors on corrosion fatigue crack initiation and propagation was revealed and the corrosion fatigue damage mechanism model was established.

Fig.1.Corrosion fatigue behavior and life evaluation.

-In recent years, the failure of materials and components reported mainly comes from surface defects (scratches, dents, cracks, etc.). Systematic research has been conducted on the stress corrosion cracking and corrosion fatigue failure mechanisms induced by surface defects, as well as damage tolerance evaluation. The research mainly includes the influence of different defect types, depths, and environments on service failure behavior, as well as online detection of crack growth rates in materials containing defects, and establishment of corresponding life prediction models.

Fig.2. Stress corrosion cracking behavior and mechanism of scratched specimen.

- With the increasing size and complexity of modern mechanical equipment structures, the evaluation of large-sized or full-size domain components has become particularly important. A series of studies on size and environmental effects were conducted on components such as main bolts, flanges, and main pipelines. The failure mechanisms of components in different size domains were analyzed, and a full-scale component life evaluation model was established.

Fig.3. Fatigue life prediction of main bolt based on temperature effect and size effect.