PSI - Issue 14

Manish Kumar et al. / Procedia Structural Integrity 14 (2019) 839–848

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Manish Kumar et. al/ Structural Integrity Procedia 00 (2018) 000–000

4. Conclusion In this paper, mixed mode creep crack growth is estimated in the turbine disc of an aero-engine consists of Inconel 718 at 650 °C using XFEM as numerical technique. Ramberg-Osgood material model with von-Mises yield criterion is used to model elasto-plastic behavior of the material. Relaxation and redistribution of stress state due to creep strain is considered in the mathematical formulation through creep law. To capture all the three phases: small scale creep, transition creep and extensive creep,   C t -integral is used as creep crack characterization parameter. The crack growth direction is computed by the maximum principal stress criterion which requires mode-I and mode II stress intensity factors (SIFs). Interaction integral approach is implemented for the evaluation of SIFs for different modes. Plasticity and creep data is taken to new configuration after each crack growth using proper data transfer and null step analysis. In this manner, the irreversibility of the creep phenomenon is maintained during crack growth. The main advantage of the proposed scheme is that there is no need of priori crack path for mixed-mode creep crack growth simulations.

(a)

(b) Fig. 4 : Schematic of an aero engine turbine disc with crack subjected to boundary conditions (a) Actual model, (b) Computational model