13th International Conference on Fracture June 16–21, 2013, Beijing, China -10- 4. Conclusions In this work, hierarchical approach to link the micro-structural characteristics of multi-phase steel and ductile crack growth resistance of a structural component was proposed (see. Fig. 19). This approach consists of macro-scopic approach and meso-scopic approach. The macro-scopic approach can provide a guideline to control mechanical properties for improving ductile crack growth resistance of a cracked structural component. And the meso-scopic approach can correlate micro-structural characteristics with mechanical properties of two-phase steel. Through the proposed hierarchical approach, micro-structural characteristics of two-phase steel to improve ductile crack growth resistance of a structural component can be discussed, however further verification works should be conducted. Figure 19. Hierarchical approach to correlate multi-scale characteristics i.e., micro-structural characteristics, mechanical properties and structural performance. References [1] M. Ohata, T. Fukahori and F. Minami, Damage Model for Predicting the Effect of Steel Properties on Ductile Crack Growth Resistance, International Journal of Damage Mechanics, 19 (2010) 441-459. [2] M. Ohata, M. Toyoda and G-B, An, Effect of Strength Mismatch on Ductile Crack Initiation Behavior from Notch Root, Welding in the World, 48, N°11/12 (2004) 9-13. [3] M. Ohata and M. Toyoda, Damage Concept for Evaluating Ductile Cracking of Steel Structure Subjected to Large-Scale Cyclic Straining, Science and Technology of Advanced Materials, 5 (2004) 241-249. [4] M. Ohata and M. Toyoda, Damage Mechanism for Controlling Ductile Cracking of Structural Steel with Heterogeneous Microstructure, Materials Science Forum, 512 (2006) 31-36. [5] M. Ohata, M. Suzuki, A. Ui and F. Minami, 3D-Simulation of Ductile Cracking in Two-Phase Structural Steel with Heterogeneous Microstructure, Engineering Fracture Mechanics, 77, 2 (2010) 277-284. [6] A.L. Gurson, Continuum Theory of Ductile Rupture by Void Nucleation and Growth: Part I - Yield Criteria and Flow Rules for Porous Ductile Media, Journal of Engineering Materials and Technology, 99 (1977) 2-15. Micro-structural ! characteristics Mechanical properties Structural performance Multi-phase steel 3D micro-structural model != " ! # $ %% & ' (( 2 +a1D*exp a 2 "m ! # $ % & ' ()1=0 3D homogeneous model Numerical damage model Bending Tension Cracked component
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