Identification of Critical Speeds of Turbine Blade Along with Stress Stiffing and Spin Softening Effects

Turbo machinery blades pass through several natural frequencies during start up and shut down operations. That will cause the resonance and cumulative damage to the turbine blades. Hence it is important to identify critical speeds. Critical speed is theoretical angular velocity which extends natural frequency of a rotating object, such as shaft, propeller, lead screw or gear. As of the speed of the rotation approaches the objects natural frequency, the object begins to resonate which dramatically increases systematic vibration. The resulting resonance occurs regardless of orientation. In this project the natural frequencies of turbine blade are identified using FINITE ELEMENT modal analysis at different speeds with spin softening and stress stiffening effects. Then the critical speeds are obtained by plotting Campbell diagram.