Fatigue life of 7075-T6 aluminium alloy under fretting condition

Fretting fatigue tests have been carried out on 7075-T6 aluminium alloy and En24 steel as a pad material to study the fretting fatigue failure life cycles. A theoretical model is developed using strain energy density criterion to estimate the process zone size at the contact edge for the three axial stresses 290 MPa, 300 MPa and 325 MPa. The number of cycles required to initiate a crack to the length of critical process zone size is termed as fretting fatigue crack initiation life cycles, NI. The fretting fatigue crack propagation life is calculated using crack analogue model. The total fretting fatigue total life is the sum of crack initiation life and crack propagation life. The estimated process zone size decreases with the increase in axial stress. Theoretically calculated crack initiation lives based on the critical process zone size model compares well with the experimental results.