9 5) According to equation (23), computing for crack tip open displacement range tδ Δ 9.204 10 ,( ) 200000 /2 1) 1 3.1416 361(450 / 2 361 1)0.001 ( -6 2 2 m E a y s s t = × × + × × = + Δ Δ = σ σ πσ δ (2) Calculation for crack growth rate under s MPa σ σ > =450 condition. According to equation (24), at m a 0.001 2 = , its crack growth rate is [ ] [ ] ) ,( / 2.4869 10 2.062 10 84151 200000 3.1416 361(450 / 2 361 1)0.001 2 10 /200000 2 2 3.1416 361(450 / 361 1) 0.00494537 ( /2 1) 22 ( ( / 1) / ) -10 -15 2.9 7 -2.9 2 2 - 2 2 2 2 m cycle E a y v a E dN da s s pv eff s s × = × ⎥ = × ⎦ ⎤ ⎢⎣ ⎡ × + × × × × + × × = × ⎥⎦ ⎤ ⎢⎣ ⎡ + Δ × + = × − λ λ σ σ πσ σ σ πσ 4. Conclusions (1) The correlating equation 2' 2 2 /2 c fc fc t N Δ = × δ δ between half-cycle of crack tip open displacement amplitude tδΔ /2 and life fc N2 , the correlating equation 2 2 2 2 c c fc t N B Δ × = − δ between one-cycle of crack tip open displacement range tδΔ and life fc N2 and the correlating equation 2 2 2 2 / λδ t da dN B= Δ between one-cycle of crack tip open displacement range tδΔ and crack growth rate 2 2 / da dN , which the interrelations among three of kinds relation- expressions actually are consistent. (2) The crack growth rate equations (10), (16), (20), (21), (24) and (28) of suitable for elastic-plastic steels are also consistent with the rate equation (3) in [3, 4]. But the material constant 2B in latter (3) is obtained from experiment under constant stress ratio condition, so that only applying to corresponding loading. And the former, they can respectively do calculations for cracks growth rates of suitable for different stress ratio and loading conditions which they are only in combination with a small number of experiment data, Therefore they can expand the application ranges, and increase the calculating reliabilities and safeties. (3) The comprehensive materials constants 2B and eff B2 in crack growth rate equations are to have interdependent functional relationships with parameters eff δ , 2λ, mδ and pv v . Its physical
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