Abstract :
This paper presents weight function approach with piece wise polynomial
interpolation function to determine the stress intensity factors at the
surface and deepest points of a semi elliptical crack induced at the blade
mounting locations of the rotor system. Initially, the mathematical model
representing tapered rotating disc is solved and the equations for radial
stress are obtained. Using the compatibility conditions, these equations are
applied to plot the stress distribution at blade mounting locations in steam
turbine rotor system. In the second part, weight functions with five and six
terms are derived separately at the surface and the deepest points of semi
elliptical crack to determine the stress intensity factors. The coefficients of
these functions are determined assuming piece wise polynomial stress
distribution along the crack. This weight function approach is applied to a
semi elliptical crack at blade mounting locations by considering the stresses
at discrete points of the crack obtained in first part and the stress intensity
factors (SIFs) are determined. The results obtained are validated with the
influence coefficient approach.
Keyword :
Stress intensity factor, blade mounting locations, steam turbine rotor, weight function approach, piece wise polynomial interpolation function