6 range is, ,( ) 4 2 2 2 m E a y t sσ π σ δ Δ Δ = (15) Then equation of crack growth rate is ) ( / 4 2 2 2 2 2 2 2 m cycle E a y B dN da s eff ， λ σ π σ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ Δ = × (16) And for different stress ratio, the eff B2 are respectively, [ ] 0) ( / ) /2 ) 24( ( 2 - 2 2 = × = pv m meff s meff s eff v a E B σ σ σ πσ λ ， (17) 0) ( 2 ) ( /2 ) / ) 1 2 4( ( 2 - 2 2 min 2 max 2 2 ≠ × ⎪⎭ ⎪ ⎬ ⎫ ⎪⎩ ⎪ ⎨ ⎧ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + − = pv m s meff meff s meff s eff v a a a E B σ σ σ σ σ σ πσ λ ， (18) Where meff σ is maximal effective stress, s meff σ σ (0.5 ~ 0.55) = . meff a is a maximal effective crack size, ,( ) (0.5 ~ 0.55) 2 2 1 2 2 m K K a s c s eff meff π σ π σ = = (19) (3) Calculation method of combination of the stress and the stress intensity factor For this method, the comprehensive material constant eff B2 in the crack propagation rate equation adopts the stress intensity factor to express, and the crack tip open displacement tδΔ range adopts the stress to express. So their forms are as bellows 2 2 4 2 2 2 2 2 2 2 2 λ λ σ π σ σ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ Δ ⎟⎟ × × ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅ = − E a y v E K dN da s pv s eff ( 0) = mσ (20) ( 0) 2 2 1 / ) 2 2( 2 2 2 2 2 1 2 2 2min 2 2max 2 2 2 ⎟⎟ ≠ ⎠ ⎞ ⎜⎜ ⎝ ⎛ Δ ⎟ ⎟ × ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⋅ + × − = − m s pv eff c s s eff E a y v K K K E K dN da σ σ π σ σ σ λ λ (21)
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