13th International Conference on Fracture June 16–21, 2013, Beijing, China With varying the crack size, the corresponding ΔKblock can be obtained by the use of J-integral method[12], as shown in Table 2. The ΔKblock is fitted by a least square method as follow： (2) 2 -0.0724 +4.131 26.198 block K a a Δ = + where the correlation coefficient R2=0.9934. The crack growth life prediction under HLCCF loading is based on Paris crack growth law which gives the expression between the crack growth rate da/dN and the stress intensity factor range ΔK: (3) / = ( )m da dN C KΔ where the two parameters of C and m can be obtained experimentally. Referred to [10], the values of C and m in equation (3) are 1.0527×10-8, 3.1826 respectively. Then crack growth life is derived by integrating Paris equation (3) over the crack length. Substituting equation (2), we can get 0 8 3.1826 1 1.0527 10 ( ( )) a block a N K a − = × Δ ∫ da (4) The crack growth life for the turbine component is 7691cycles, which is equal to flight life 2673.8 hours . If the safety factor is set as 2.0 referred to [13], then the life prediction is 1336.9hours which agrees well with the experimental result. Figure 9. Mesh of turbine component Figure 10. Singular finite elements at the crack tip Table 2. Stress intensity factor value through FM analysis Crack size a/mm Stress intensity factor range ΔK/(MPa√m) 0.8 24.04 4.5 45.61 8.2 59.00 11.9 67.99 15.6 74.31 19.3 78.71 23 81.63 -7-
RkJQdWJsaXNoZXIy MjM0NDE=