Strain Energy-based Critical Plane Approach For Multiaxial Fatigue Life Prediction Of A Turbine Disk-Blade Attachment

As one of the main load-bearing components of aero engine,high-pressure turbine disc is listed as the first key component of aero engine due to its adverse working environment.While improving the overall performance of the engine,the structural integrity of its key parts should be given sufficient attentions.As a key component of aero-engine and the main connection form of turbine disc and blade disc,tenon structure bears the coupling effect of complex cyclic thermal load and mechanical load during operation,and is usually the key area where failure occurs frequently in engine structure,among which low cycle fatigue failure is one of the most important failure forms.Therefore,fatigue life analysis of tenon structure in low-cycle fatigue failure mode is of great significance to ensure the safe operation of turbine disc and blade.This dissertation takes a certain type of aero-engine turbine disc-blade attachment as the research object and carries out the following research:(1)A multiaxial fatigue critical plane-damage parameter of equivalent strain based on von Mises criterion.Based on the equivalent strain synthesized by von Mises criterion,a new critical plan damage parameter for multiaxial fatigue is proposed.The fatigue life prediction accuracy of the proposed model is verified by combining the experimental data of smooth thinwalled ring specimens of three materials such as disk alloy GH4169 under different loading paths and four commonly used models of multi-axis critical surface fatigue life prediction.(2)Prediction of multiaxial fatigue life based on critical plane by equivalent strain energy.Based on the study of the equivalent stress life curve,the von Mises equivalent stress is modified.Meanwhile,considering the effect of equivalent strain,a new multiaxial fatigue life prediction model was proposed by coupling energy and critical plane method,then the applicability and prediction accuracy of the new model are verified by combining the test data of smooth thin-walled ring specimens of three materials such as disk alloy GH4169 under different loading paths and four commonly used critical plane life prediction models.(3)Fatigue life prediction for turbine disc blade based on critical plane-energy model.FE analysis of a high-pressure turbine disc under typical working conditions is carried out,and the simulation results of stress and strain under three kinds of rotational speed cyclic loading are obtained.By extracting the stress and strain simulation information of the fractured part of turbine disc under these three working conditions,and combining with the proposed critical plane-energy multiaxial fatigue life model,the service life of the turbine disc is predicted.