Abstract: Experimental data of notched specimen of LY12 aluminium alloy was gained through fatigue test with different stress ratios and stress levels.Based on fracture mechanics and material parameters,an extrapolated backwards model was established to calculate the initial discontinuity state (IDS) values.The results indicated that the calculated IDS values of LY12 aluminium alloy scattered widely.A statistical analysis showed that the distribution of IDS values fitted well with Weibull distribution.Based on this work,a holistic engineering model was developed.The predicted fatigue lives were in good agreement with the experimental data.Thus,the feasibility for the establishment of link between the classical fatigue and modern damage-tolerance methodologies is demonstrated.