Fatigue Life Prediction Based on Crack Closure and Equivalent Initial Flaw Size

Area of Science:

• Materials Science
• Mechanical Engineering
• Fracture Mechanics

Background:

• Accurate fatigue life prediction is crucial for engineering structural integrity.
• Existing models may not fully capture crack closure effects across different crack growth regimes.

Purpose of the Study:

• To propose a general methodology for fatigue life prediction of smooth and circular-hole specimens.
• To incorporate crack closure effects and the equivalent initial flaw size (EIFS) concept.
• To validate the proposed method using experimental data from various alloys.

Main Methods:

• Utilized a crack closure model and the equivalent initial flaw size (EIFS) concept.
• Determined EIFS using fatigue limit and fatigue threshold stress intensity factor (ΔK).
• Calculated ΔK via a back-extrapolation method and validated against experimental data for Al2024-T3, Al7075-T6, and Ti-6Al-4V.

Main Results:

• The proposed methodology demonstrated good agreement between model predictions and experimental fatigue life data.
• Effectively considered the distinct impacts of crack closure on small and long crack growth.
• Validated for semi-circular surface cracks and quarter-circular corner cracks in different specimen types.

Conclusions:

• The developed methodology provides a reliable approach for fatigue life prediction.
• The integration of crack closure and EIFS enhances prediction accuracy.
• Further research can explore additional material types and complex geometries.