Method and integrally bladed rotor for blade off testing

A method for performing blade off testing on an integrally bladed rotor for a gas turbine engine, comprising:

• providing an integrally bladed rotor having:
• a hub having a forward end, an aft end, a circumferentially extending exterior surface disposed between the forward end and the aft end;
• a plurality of rotor blades integrally attached to the hub and circumferentially spaced around the hub, the plurality of rotor blades including a test blade, each rotor blade of the plurality of rotor blades extending radially out from the hub exterior surface, and each rotor blade of the plurality of rotor blades having an airfoil with a leading edge, a trailing edge, a suction side surface, a pressure side surface, a base end, and a width extending between the suction side surface and the pressure side surface, and each airfoil comprised of an airfoil material having one or more mechanical strength properties;
• wherein the airfoil of the test blade includes at least one slot defining a void in the airfoil, the at least one slot extending a lengthwise distance into the airfoil along a direction generally between the leading edge and trailing edge of the airfoil, the at least one slot terminating at a slot end surface, and at least one internal cavity extending lengthwise from the slot end surface;
• disposing at least one heating element disposed in the at least one internal cavity, wherein the at least one heating element is configured to selectively produce an amount of thermal energy sufficient to heat the airfoil material proximate the internal cavity from a first temperature to a second temperature and at the second temperature the one or more mechanical strength properties of the airfoil material proximate the internal cavity are decreased;
• operating the gas turbine engine to test operating conditions;
• and
• selectively operating the at least one heating element to produce the amount of thermal energy sufficient to heat the airfoil material proximate the internal cavity from the first temperature to the second temperature to cause the test blade to be liberated from the integrally bladed rotor.

An integrally bladed rotor for a gas turbine engine, the integrally bladed rotor configured for use in blade off testing, comprising:

• a hub having a forward end, an aft end, a circumferentially extending exterior surface disposed between the forward end and the aft end;
• a plurality of rotor blades integrally attached to the hub and circumferentially spaced around the hub, the plurality of rotor blades including a test blade, each rotor blade of the plurality of rotor blades extending radially out from the hub exterior surface, and each rotor blade of the plurality of rotor blades having an airfoil with a leading edge, a trailing edge, a suction side surface, a pressure side surface, a base end, and a width extending between the suction side surface and the pressure side surface, and each airfoil comprised of an airfoil material having one or more mechanical strength properties;
• wherein the airfoil of the test blade includes a plurality of internal passages disposed in the airfoil proximate the base end, the plurality of passages extending between the suction side surface and the pressure side surface;
• and
• a plurality of heating elements, each disposed in a respective one of the plurality of internal passages, wherein each of the plurality of heating elements is configured to selectively produce an amount of thermal energy sufficient to heat the airfoil material proximate the respective internal passage from a first temperature to a second temperature and at the second temperature the one or more mechanical strength properties of the airfoil material proximate the internal passages are decreased;
• wherein at the second temperature the one or more mechanical strength properties of the airfoil material proximate the respective internal passages are decreased to a point where the airfoil material proximate the respective internal passages will fail during a blade off test.