Elastic‐Plastic Fretting Fatigue Contact‐Regime Map for Aluminum 2024‐T3: FE Validation of Invariant Bulk Shear Stress Stiffness and Transition Criteria

The Nowell–Hills bulk stress formulation is extended and validated for elastic–plastic fretting contacts of the industrially well‐known Aluminum 2024‐T3 using finite element analysis. Over 150 simulations spanning friction coefficients μ = 0.1–1.5, stress ratios R = 0–0.9, and normal loads P = 67.875, 135.75, and 271.5 N/mm reveal a key finding: The bulk‐stress–induced shear stiffness remains invariant despite extensive cyclic plasticity. Analytical expressions for the critical bulk stresses governing transitions between partial slip, mixed slip, and gross sliding regimes are derived and validated against FE results with maximum errors below 4%. Furthermore, the second transition boundary can be expressed directly in terms of the first boundary and R . A closed‐form fretting regime map constructed using the validated stiffness and transition criteria accurately classifies the simulated cases. This enables rapid fretting fatigue regime prediction for the present Aluminum 2024‐T3 without requiring computationally intensive cycle‐by‐cycle finite element analysis.