Strength Evaluation in Turbo Machinery Blade Disk Assembly at Constant Speed

Abstract

In the present work, 3D finite element analyses (FEA) of a low pressure (LP) steam turbine bladed disk assembly are carried out at constant speed loading condition. The prime objective of this work is to optimize the geometry of the bladed disk root with the aid of the Peterson’s stress concentration factor (SCF) charts available in the literature. Secondly, design rules are developed for the structural integrity of the blades and disk considering a safety factor for material, manufacturing and temperature uncertainties. These design rules are in turn used as design checks with the aid of finite element analysis results. Special investigations were performed based on Neuber formulae for reducing the local peak stresses at the blade and disk root fillet using linear analysis to identify the equivalent non linear stress values by the strain energy distribution method for estimating the minimum number of cycles required for the onset of crack initiation.