Fir tree fastening of turbomachinery blades—II

Blade-root fastening of the fir-tree shape, used in securing turbomachinery blades to the rotor has been analysed by considering it as an assembly of the step-segments, the stiffness characteristics of which are already obtained in Part-I. The general equation of equilibrium as well as the compatability of deformation between the steps of the blade and the disc give the necessary ‘ n ’ linear algebraic equations for the evaluation of the step loads in the n- step root. The method can accommodate the centrifugal body forces of the root itself, the friction between the blade and disc-steps and the difference in the material of the blade and the disc.