Numerical determination of Paris law constants for carbon steel using a two-scale model

6th International Conference on Fracture Fatigue and Wear

Mlikota, M.^1 ; Staib, S.^2 ; Schmauder, S.^1 ; Boi, .^2

Institute for Materials Testing, Materials Science and Strength of Materials (IMWF), University of Stuttgart, Pfaffenwaldring 32, Stuttgart

70569, Germany^1

Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, I. Luia 5, Zagreb

10000, Croatia^2

关键词: Engineering alloys;    Long fatigue crack growths;    Material constant;    Numerical calculation;    Standard specimens;    Stress levels;    Test procedures;    Two-scale model;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/843/1/012042/pdf
DOI  :  10.1088/1742-6596/843/1/012042

来源: IOP

【 摘 要 】

For most engineering alloys, the long fatigue crack growth under a certain stress level can be described by the Paris law. The law provides a correlation between the fatigue crack growth rate (FCGR or da/dN), the range of stress intensity factor (ΔK), and the material constants C and m. A well-established test procedure is typically used to determine the Paris law constants C and m, considering standard specimens, notched and pre-cracked. Definition of all the details necessary to obtain feasible and comparable Paris law constants are covered by standards. However, these cost-expensive tests can be replaced by appropriate numerical calculations. In this respect, this paper deals with the numerical determination of Paris law constants for carbon steel using a two-scale model. A micro-model containing the microstructure of a material is generated using the Finite Element Method (FEM) to calculate the fatigue crack growth rate at a crack tip. The model is based on the Tanaka-Mura equation. On the other side, a macro-model serves for the calculation of the stress intensity factor. The analysis yields a relationship between the crack growth rates and the stress intensity factors for defined crack lengths which is then used to determine the Paris law constants.