PSI - Issue 2_A

Dong-Jun Kim et al. / Procedia Structural Integrity 2 (2016) 832–839 Dong-Jun Kim et al. / Structural Integrity Procedia 00 (2016) 000–000

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(c) (d) Fig. 4. Comparison of FE results for opening stress at r/a=0.005 with the proposed equation Eqn. (17) under load control condition: (a) m=n=5, (b) m=5, n=10, (c) m=10, n=5, (d) m=n=10. Fig. 5 shows comparison of FE results on normalized crack opening stresses by reference stress under displacement control condition with Eqn. (18). The stress fields are also calculated at r/a = 0.005 and show the characteristics for the time of secondary loading. Eqn. (18) is a good prediction for the crack-tip stress fields under transient creep. In Fig. 4 and 5, the error between FE results and proposed equation is occurred from the constraint effect. 5. Conclusion In this paper a crack-tip stress field under creep condition is characterized from the modified existing equations. The prediction equation presented respectively according to the primary loading and the secondary loading. In order to verify the proposed equations, finite element analysis for single-edge-crack bend specimen under elastic-plastic creep was performed. For applying the primary loading the SEB specimen was subjected by load control and for the secondary loading the specimen was subjected by displacement control. In displacement control condition elastic follow-up factor was determined by comparing FE results with existing equation. The proposed equation was verified by comparing with FE results and was similar to FE results. In future work, constraint effect under creep condition will be studied and the proposed equation in the present study will be improved by considering the constraint effect for various specimen.