Validating the Methods to Process the Stress Path in Multiaxial High-Cycle Fatigue Criteria

Area of Science:

• Mechanical Engineering
• Materials Science
• Fatigue Analysis

Background:

• Multiaxial fatigue strength evaluation relies on accurate stress path analysis.
• The choice of stress path analysis significantly impacts equivalent stress calculations for complex load combinations.

Purpose of the Study:

• To describe and analytically evaluate three key stress path analysis methods: minimum circumscribed circle, minimum circumscribed ellipse, and moment of inertia.
• To validate these methods by integrating them into six distinct multiaxial fatigue strength criteria and comparing with experimental data.

Main Methods:

• Analytical solutions for evaluating the minimum circumscribed circle, minimum circumscribed ellipse, and moment of inertia methods under multiaxial stress states with harmonic stress components.
• Integration of these methods into six established multiaxial fatigue strength criteria.
• Validation against available experimental fatigue data.

Main Results:

• The moment of inertia method yields excessively conservative fatigue life predictions.
• The minimum circumscribed circle and minimum circumscribed ellipse methods show comparable results, with the ellipse being slightly less conservative.
• The minimum circumscribed ellipse demonstrates superior performance for critical plane criteria and stress tensor transformations into Ilyushin deviatoric space.

Conclusions:

• The minimum circumscribed ellipse method is recommended for specific multiaxial fatigue criteria, offering a balance between accuracy and conservatism.
• The moment of inertia method should be used with caution due to its overly conservative nature.
• Further investigation into the application of the minimum circumscribed ellipse for integral criteria is warranted to understand its conservative shift.