Creep damage and fracture of turbine blade roots

Abstract

An approach to modeling creep fracture under a complex stress state using the Finite Element Method is proposed. The model of the turbine blade root was studied. The methodology of the transition in the analysis from the general 3D to the 2D stress state is proposed. For the models of the roots, the characteristics of the damage accumulation were obtained and the analysis of subsequent fracture in roots made of different materials was performed.The novel results of the description the creep fracture behavior after the period of damage accumulation were obtained. Based on the analysis of the numerical results, it was established that for different materials qualitatively different fracture processes occur in different places of the blade root. They were as follows: the fracture with separation of the main part of the root between the lower teeth; destruction of a separate tooth with a transition inside the root, as well as of a separate tooth jointly with the root’s lower part. A novel approach to obtaining the form of an equation for description the current length of a creep crack by use of numerical results is proposed.