2D & 3D FE Analysis of Fir-tree Joints in Aeroengine Discs

grantor: University of TorontoA comprehensive 2-D and 3-D finite element study is undertaken to examine the effect of the critical geometric features and interface conditions in the fir-tree region of a turbine disc upon the stress distribution at the blade/disc interface. Three aspects of the work were accordingly examined. The first was concerned with the stress analysis of the critical geometrical features and interface conditions (friction) of various fir-tree configurations, thus enabling the evaluation of the critically loaded regions in the disc. The second was concerned with the three-dimensional finite element analysis of the assembly, so as to examine the effect of the skew angle upon the triaxial state of stress and load sharing between the teeth in turbine discs. The third aspect was devoted to the validation of the FE predictions using existing photoelastic stress freezing results. The outcome of the work reveals the importance of the contact angle, upper and lower flank angles, number of teeth, and skew angle upon the stress field. Frictional conditions at the interface were also investigated and the results reveal that they play a minor role in determining the level of interface stresses.M.A.Sc