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The dynamic behaviors of cracked rotating components (shaft
and blade)of rotor systems were investigated. With the crack
released energy, thelocal flexibility due to crack was
evaluated. An energy principle inconjunction with the assumed-
modes method or the weighted residual methodwere applied to
yield the discrete equations of motion. In this paper, three
different topics with cracked shaft and crackedblades were
discussed, numerical examples were given for each case.
(1)rotating shaft with a transverse crack: The two times
component of rotatingspeed of response amplitudes excited by
crack breathing was taken as theindex for crack identification.
A feasible technique for the identificationof crack depth and
crack location by intersecting the two equi-amplituderesponse
curves of two separated sensing probes was presented. The
stabilityof!the system caused by a crack was examined via the
Floquet Theory and themultiple scale method. (2) rotating blade
with a transverse crack : Theinfluences of crack depth, crack
location and rotating speed on the bendingnatural frequencies
were then studied. Numerical results showed that thecrack
effects were appreciable only if it was relatively deep and
occurrednear the root. (3) rotating shaft-disk lades system with
a cracked blade:Numerical examples were given for cases between
two and five symmetricallyarrayed blades. There existed both
torsion-bending coupled modes andblade-coupled modes, which
occur at repeated frequencies. When there is acracked blade, the
frequencies of torsion-bending coupled modes decreased,and
blade-coupling modes had the phenomena of frequency bifurcation.
Finally,torsional responses of the shaft due to a harmonic
excitation were illustrated.
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