Issue 35

C. Gandiolle et alii, Frattura ed Integrità Strutturale, 35 (2016) 232-241; DOI: 10.3221/IGF-ESIS.35.27 238   h x I dt t tM K 0 ). ( ). ( 2   (7) with                   2 2 1 2/1 . . 1. )( h t m h t m t tM (8) and 6 2 rC rB A m i i i i    (9) with A 1 =A ref , B 1 =27.9558A ref , C 1 =14.2870A ref , A 2 =0.4070A ref , B 2 =5.3504A ref and C 2 =113.9489A ref . The contribution of mode II was neglected [1]. Finally the effective stress intensity range is obtained following the Eqs. 2 to 4. Crack nucleation life was neglected following the observation of the previous paragraph. The total lifetime was thus equivalent to the propagation life. The loading cycles related to the propagation stage were computed using ΔK eff integrated from b=0 up to failure:        T b b m P T KC db N N 0 (10) Failure was related to K Imax =K IC with K IC =212Mpa. Alternatively, if ΔK eff (b) crosses the crack arrest condition ΔK 0 then the crack stops propagating and crack arrest is reached. Fig. 7 compares the crack length obtained from the potential drop technique with the crack length determined from the predictive method. A rather good correlation is observed. In addition the model tends to overestimate the crack extension rate which indirectly provides a conservative and safe estimation of the fretting fatigue cracking risk. Figure 7 : Comparison of experimental and theoretical crack propagation rates. (R=4.6mm, P, σ F,moy /σ y,flat =0.78, R F =0.85, Q*/P=0.30). Application of prediction method to a mixed load test Three blocks of different fretting fatigue loading were applied successively on the fretting fatigue contact (Tab. 2 and Fig. 8). Individually, block 1 led to failure (Fig. 7), block 2 led to crack arrest and block 3 generated no detectable crack.