Mitigation strategy for airfoil cracks for integrally bladed rotors

An integrally bladed rotor (IBR), comprising:

• a hub;
• and
• blades, each blade comprising:
• an airfoil section to aerodynamically interact with a flow of air for compressing the air;
• and
• a root fillet integrally formed with the hub and from which the airfoil section integrally extends, the root fillet comprising:
• a curved exterior surface having points of tangency with the airfoil section to define an outboard extent of the root fillet;
• and
• a root fillet body between the hub and the outboard extent of the root fillet and defining a series of cutouts for arresting cracks that are most likely to form and propagate.

A method defining a mitigation strategy for hazardous airfoil cracks for an integrally bladed rotor (IBR) comprising root fillets, each root fillet comprising a curved exterior surface having points of tangency with an airfoil section to define an outboard extent of the root fillet and a root fillet body between a hub and the outboard extent of the root fillet, the method comprising:

• analyzing root fillet dynamic and steady stress fields;
• analyzing field cracking history;
• performing crack growth simulations based on results of the analyses to determine likely crack propagation tracks into the root fillets;
• identifying locations for cutouts in the root fillets along the likely crack propagation tracks;
• analyzing a stress concentration impact of the cutouts;
• and
• machining the cutouts through the root fillets in an event analysis results of the stress concentration impact are indicative of a limited impact.