Mechanical coupling effects on turbomachine mistuned response

Mistuning in turbine engine bladed disks often leads to mode localization, which can result in high vibratory stresses in a single group of blades. Th ese stresses can lower the fatigue life of the blades. Therefore, understan ding mistuning is essential for design of durable rotating machinery. This investigation provides one of the first experimental demonstrations of phen omena associated with mistuning, including frequency splitting and orthogon ality, Results illustrate the role of internal coupling on mistuned respons e. Coupling appears to be dependent on fundamental mode shape. Strong coupl ing prevents localization in bending modes. However, in spite of weak inter nal coupling, localization does not occur in an observed torsion mode. The primary consequence of mistuning is a breakdown of orthogonality between th e nodal patterns of the mode shapes and harmonic excitations, resulting in numerous resonant responses to a single harmonic forcing function. The brea kdown of nodal patterns also leads to increased difficulty with mode descri ption.