A Low Cycle Fatigue Analysis on a Steam Turbine Bladed Disk-Case Study

This work concerns the root-cause investigation of the blade damage in a steam turbine bladed disk of a thermoelectric power plant. The purpose of this work is to investigate the low cycle fatigue problem by determining the natural frequencies and the associated modes of vibrations of a bladed disk and comparing with the operational rotation of the turbine and its harmonics. The bladed disk is an assembly of several blades grouped and each group is an assembly of four or five blades, connected by elements named shroud and tie-wire. The computational model of a single blade and of a blades grouped are fitting by modal analysis measurements. Finally, a numerical modal analysis is made on a complete bladed disk in order to investigate the low cycle fatigue problem.