13th International Conference on Fracture June 16–21, 2013, Beijing, China -9The equation of the line is shown as below. lg( / ) 1.4231 lg( ) 8.7221 ⋅ ∆ − = K dN da . (31) The Paris equation is m K C dN da ( ) / = ∆ . (32) In order to get the values of Cand m, the paper takes the logarithm on both sides of the equation (32). C K m dN da/ ) lg( ) lg lg( = ⋅ ∆ + . (33) The values of the Paris constants Cand mare obtained by comparing the equation (31) with (33). C=1.896E-09, m=1.4231. The lg(da/dN)~lg(ΔK) curve of region II of the lugs subjected to 30 degrees oblique pin-load can be got by the same method. Figure 19 shows the lg(da/dN)~lg(ΔK) curve. * * Fitted line Data points lg(da/dN) l g (ΔK) * * * * * * * * * * * * * * * * * * * * * * * * * * * -6.55 -6.6 -6.65 -6.7 -6.75 -6.8 1 .5 1.6 1.7 1.8 Figure 19. lg(da/dN)~lg(ΔK) curve of the 30 degrees oblique pin-load case The equation of the line and the values of the Paris constants Cand mare shown as below. lg( / ) 0.7649 lg( ) - 7.8902 K dN da = ⋅ ∆ (34) C=1.2877E-08, m=0.7649. 6. Conclusions Analytical and experimental investigations for fatigue crack growth behavior of 30CrMnSiA straight attachment lugs were performed. From this investigation followings are concluded. 1. The boundary conditions of the finite element model is consistent with the true condition, cosine distributing load is the key of ensuring precision of FEM analysis. 2. The expressions of the SIFs of straight lugs subjected to axial or less than 45 degrees oblique pin-load are determined and validated. Based on this, the stress intensity factor range (ΔK) can be calculated. 3. The fatigue crack growth model of the typical straight lugs is established, offering an analytical as well as experimental method for assessing and designing damage tolerant attachment lugs in engineering. References [1] R. Rigby, M.H. Aliabadi. Stress intensity factors for cracks at attachment lugs. Eng. Failure Anal. 1997;4(2):133-146. [2] Liu, A. F., Kan, H. P.. Test and Analysis of Cracked lugs. Frac. 1977;3: 567-664.
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