Analysis of Barreling and Tolerance Effects of Blade Attachments

Abstract: In a gas turbine rotor, the Blade-Disc attachment is often a critical part. This part needs to endure both high contact stress and high temperature. Thus, the prediction of the life of the attachment becomes important.  Furthermore, the refinement of the Blade-Disc attachment is worth to study, to extend the lifetime of the turbine rotor. In this work, the Blade-Disc attachment is belonging to the gas turbine section.    Geometry modifications based on a 2D FE-model of a blade-disc attachment are performed. Besides of flat contact surface, an alternative curved contact form which creates a barrel on the contact surface is studied. The effect of the different geometries, is studied with respect to high local stresses. The results are evaluated using different methods; deterministic LCF life using EVAL, probabilistic LCF life using ProbLCF and fretting damage parameter evaluation  using the Ruiz-Chen Model.    During this work, geometry modifications based on a 2D Blade-Disc attachment is performed first to study the effect of the different modification results. Then a fretting damage parameter evaluation is carried out, to discuss the crack initiation position of the models with respect to different modification cases. Finally, low cycle fatigue tests are performed to analyse the life cycle of the models.    The result of the work shows at manufactory tolerances can cause a maximum stress increase by at least 60% in the model, especially in the contact surfaces. Also, comparison results shows apply a barrel to the contact surface can effectively decrease the maximum stress in the model, and extend the cyclic life of the attachment. The most suitable barrel height for this work is between 0.05[mm] and 0.015 [mm].