8 ( 0) ( /2 1) ) 2 2 (1 2 2 2 2 - 2 2 ≠ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + Δ ⎟⎟ × ⎠ ⎞ ⎜⎜ ⎝ ⎛ − = m s s pv c m eff E a y v dN da σ σ σ πσ δ δ δ λ λ ， (28) Here can take 0≈ mδ . 3. Calculation example A pressure vessel is made with steel 16MnR, its strength limit of material MPa b 573 = σ , yield limit MPa s 361 = σ , modulus of elasticity MPa E 200000 = . Critical stress intensity factor 92.7MPa m 1 2 = = c c K K . Suppose shape correcting coefficient of long crack 1.01 2 = y . Its local stress = max σ 450MPa at stress concentration point, 0 min = σ . Other computing data is all in table 1. Try to calculate the growth rate 2 2 / da dN at crack size m a 0.001 2 = under 391 450 > = = s MP σ σ MPaconditions. Table 1. Calculation data K MPa m c , 1 K MPa m eff , K MPa m th , pv v 2m m fc , 2δ 2λ 2y β 92.7 28.23 8.6 7 2 10− × 3.91 0.00018 2.9 1.01 1 (1) Calculations for relevant parameters 1) According to table 1, take the virtual rate, 2 10 (m/Cycle) -7 = × pv v . 2) Take effective crack tip open displacement, 6.3 10 ( ) 0.35 0.00018 0.35 5 m m c eff − = × = × = × δ δ ; Take 0≈ mδ . 3) Calculation for effective crack size 10 ( ) 4.94537 ( / 1) 3 m E a s s eff eff − × = + = σ σ πσ δ 4) According to (26), calculation for comprehensive material constant eff B2 [ ] [ ] ) / ( 2 10 84151 /200000 2 2 3.1416 361(450 / 361 1) 0.00494537 22 ( ( / 1) / ) 2 2 7 -2.9 - 2 m m cycle v a E B pv eff s s eff ⋅ × × = + × × = × × + = × − λ λ σ σ πσ The experiment value of Steel 16MnR, 84570 2 = B , and here its calculation value 84151, so that it is close to experimental data.
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