The fracture occurring in many metallic structures made of steel is mainly fatigue fracture. Fatigue fracture is a dangerous one that decreases the safety of structures. Fatigue fracture occurring in metallic structures is predicted by fracture mechanics method.
Paris suggested a propagation equation for fatigue crack and many researchers found other crack propagation equations by correcting and supplementing Paris’s equation.
However, very few studies have focused on the prediction of the fatigue life of structures and components from the characteristic data of structures comprising metallic materials. For example, the relationship between the metallographic parameters of steel like hardness, volume ratio, grain size and distribution of non-metallic inclusion, etc., and its fatigue life was not quantified.
Kim Mun Chol, a researcher at the Faculty of Materials Science and Technology, simulated the fatigue procedure of a steel structure using a crack-tip sliding model based on continuous distribution dislocation theory and calculated the rest fatigue life of an inertia train structure.
Through the simulation, he found that the hardness of microstructure exerts decisive effects on the fatigue life of steel structures of ferrite-pearlite structure while the grain size and volume ratio hardly affect it, and slip-band crack sharply decreases as inclusion grain size decreases below 7㎛.
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