A Crystallographic Approach to Life Prediction Analysis of a Turbine Engine Blade to Disk Attachment

Fretting fatigue raises many challenges in modeling and predicting of a turbine engine blade disk attachment response. It occurs when the blade and disk are pressed together in contact and experience a small oscillating relative displacement due to variations in engine speed and vibratory loading. Fretting causes a very high local stress near the edge of contact resulting in wear, nucleation of cracks, and their growth, which can result in significant reduction in the life of the material. Fretting depends on geometry, loading conditions, residual stresses, nonlinear response, and surface roughness, among other factors. These complexities make fretting a significant driver of fatigue damage and failure risk of disks. That is, fretting is often the root cause of the nucleation of cracks at attachments of structural components, and the cyclic plastic cumulative deformation and damage occur within depths of only several grains. Hence, resolving the deformation at the scale of individual grains, in order to understand the crystallographic orientation dependence of plasticity driven fretting fatigue and its relation to surface contact conditions, is important. In this study, a finite strain computational crystal plasticity constitutive law will be implemented to simulate and investigate time dependent response of turbine engine blade to disk attachment. The present work leverages the computational model of early efforts, which focused on modeling damage initiation and propagation due to fretting fatigue using micro-thermo-mechanical model, and further enhances the capabilities of capturing the micro-scale nature of the fretting small oscillatory relative displacement at grain level. These efforts provided a high fidelity approach to capture the life of the material at the blade to disk attachment and to simulate the realistic mechanism associated with fretting.