engleski

The estimation of optimal impact toughness for the material of turbine shaft

The fracture of the turbine shaft in case of overloading can exhibits the brittle or plastic collapse, depending on the material properties, turbine shaft geometry and loading manner. Usually when the toughness increases, the stiffness of the material shaft becomes lower what can lead to the plastic bending of shaft. If the fatigue crack appears in the critical region-section of shaft, then the low impact toughness value may induce the brittle fracture. During retrofit of hydro-power plant the new turbine shaft was produced by quenching and tempering technology. Performed Charpy impact toughness tests show lower values of shaft’ s material than prescribed by project documentation. Since the turbine shaft for hydro-power plant is massive and expensive component, it is necessary to figure out sufficient impact toughness of material by respect geometry and loading manner of turbine shaft. Since, only the yield strength and impact toughness of the material have been prescribed, the level 0 of SINTAP procedure should be applied. Minimal impact toughness values which ensure the ductile fracture of the shaft cracked circumferentially have been estimated. It has been analyzed variation of shaft carrying capacity due to reduction of non-cracked ligament in the transversal direction.

turbine shaft; impact toughness; SINTAP procedure

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