Mariusz Banaszkiewicz

By Mariusz Banaszkiewicz

The paper presents the results of numerical analysis of creep-fatigue damage development in a steam turbine rotor under cyclic duty. Investigations were performed for a full cycle representing the most accurate description of real operation and three simplified cycles representative of different levels of simplification in inelastic strains modeling. It was shown by numerical simulations that significant inaccuracies in creep-fatigue damage predictions, reaching an order of magnitude in deviation of inelastic strains, cannot be excluded when simplified models are used. It is thus concluded that full consideration of creep-fatigue damage at real operating conditions requires proper modeling of stress/strain histories using visco-elastic-plastic material models.

Part of the book: Thermal Power Plants

By Mariusz Banaszkiewicz and Janusz Badur

This chapter presents two practical methods of thermoelastic stress calculation suitable for application in online monitoring systems of steam turbines. Both methods are based on the Green function and Duhamel integral and consider the effect of variable heat transfer coefficient and material physical properties on thermal stresses. This effect is taken into account either by using an equivalent steam temperature determined with a constant heat transfer coefficient or by applying an equivalent Green’s function determined with variable heat transfer coefficient and physical properties. The effectiveness of both methods was shown by comparing their predictions with the results of exact three-dimensional (3D) calculations of a steam turbine valve.

Part of the book: Selected Problems of Contemporary Thermomechanics