In view of pedestal looseness fault often occurred in the engineering

a finite element model with looseness fault was established and dynamic characteristics of one-support looseness and two-support looseness were studied.The results show that the system motion experiences period-one

period-two

period-six and period-four with the decrease of looseness stiffness in two looseness cases.However

the rotor trajectory is different

since one-support looseness

rotor trajectory is an 8 shape curve with large difference in up and down layers

then becomes two nested 8 shape curves

finally becomes a spiral shape curve.For two-support looseness

rotor trajectory is approximately triangle

then two adjoining 8 shape curves

and finally becomes a spiral curve.The results will provide theoretical references for fault diagnosis

dynamic design

and safe operation of rotor-bearing system.