Abstract:

A turbine disk is known as one of the important parts of a jet engine. In the design and analysis of its damage tolerance, it is necessary to determine the critical crack length aic exactly. Using the cracks at the bottom of firtree slots of the first stage turbine disk in an existing engine as an example, by means of the breakdown test and elaborate theoretical calculation, the criterion and the solution algorithm to determine the critical crack length aic are provided. It is suggested that the condition under which the engine could not normally operate be regarded as the critical state for the crack. In view fo the complexity of turbine disk shape and loading conditions, the authors have employed "twice evaluation algorithm'' for J-integral in the elasto-plastic fracture mechanics. This algorithm comes out simple and more accurate than those presented in literature.