Thermo-Mechanical Model for Life Prediction of a Turbine Engine Blade to Disk Attachment

ABSTRACT Life prediction of turbine engines is crucial part of the management and sustainment plan to aircraft jet engine. Recently the failure of engines on four jet aircraft overseas during the past few years has prompted the National Transportation Safety Board (NTSB) to issue an "urgent" recommendation to increase inspections of the engines on U.S. aircraft. At issue are older engines found on a small number of jets. The Federal Aviation Administration (FAA) issued a rule in March 2010 requiring inspections of the engines within 50 flights, and repeat inspections every 175 flights thereafter. Fretting is one of the primary phenomena that leads to damage or failure of blade-disk attachments. It is an important problem for the operators of turbine engines. 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 disk blade attachments. Fretting is a complex phenomenon that depends on geometry, loading conditions, residual stresses, and surface roughness, among other factors. These complexities also go beyond the physics of material interactions and into the computational domain. Fretting is often the root cause of nucleation of cracks at attachment of structural components at or in the vicinity of the contact surfaces. The focus of this effort is to introduce a framework to investigate thermal effects on fretting fatigue of blade-disk attachment. A novel thermo-mechanical contact damage mechanics with unified viscoplasticity Bodner-Patom model is developed. It is implemented in a couple thermal-stress simulations to investigate their influence on fretting. Finally, to demonstrate its capabilities, numerical simulations will be presented.