Stress concentration factors in re-evaluation of design solution

Abstract

The failures of various parts of mechanical systems in powe industry are the lessons that should be learned thoroughly. Every behaviour of structure close to design encelope must be ecxamined carefully in order to minimize financial losses in future and subsequently increase energy efficiency. Better design procedure or procedures that will gain more accurate results are major request to engineers and researchers last few decades. The verified methods that have proven potentials in application on power industry components coul be used ub assessment and evaluation of critical conditions that could lead to failures. A case study from hydro power plant turbine shaft was chosen as subject for design re-evaluating methodology. The classic analytical calculation of this shaft uses the Peterson's elastic stress concentration factor and calculates stress concentration factors and maximum stresses for different stress components of combined load and then calculate analytical valuesof total stress by hypothesis of maximal normal stress. On the opther hand, presented Finite Element Analysis simulates shaft stress state under real conditions of complex load by simulataneously applying all load components (bending, torsion and tension). Both of calculations are performed for few different radii in shaft-flange sections, as basis for re-evaluation of application of stress concentration factors.