Incorporating Micro-Thermo-Mechanical Damage Model in Life Prediction Analysis of a Turbine Engine Blade to Disk Attachment

Fretting is an important problem for the operators of turbine engines, and 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. It is a significant driver of fatigue damage and failure risk of disks. The present effort focuses on the damage initiation and propagation due to fretting fatigue. It introduces a micro-thermo-mechanical damage model that is capable of capturing the micro-scale nature of the fretting small oscillatory relative displacement. The micro-scale capability of the damage model is required to capture the effect of very high local stress near the edge of contact, which results in wear, nucleation of cracks, and their growth. It also provides a high fidelity approach to capture the significant reduction in the life of the material at the blade to disk attachment. To further understand the role of damage in the fretting initiated fracture, a specially developed novel fretting crack initiation model is incorporated in the analysis. Such combination makes it possible to simulate the realistic mechanism associated with fretting. The models are incorporated in a fretting fatigue simulation of an actual blade and disk attachment configuration. The results are validated with data obtained from an actual blade and disk attachment test using a representative loading mission. The results show consistency and accuracy with experimental data.© 2013 ASME