The exciting sources for axial vibration of disk

especially the new axial gas dynamic force induced by travelling waves and its properties

and influence on the vibration of disks are studied.It is shown that the travelling wave induces new gasdynamic force which can damp out the foreward traveling wave vibration and induces the self exciting vibration for the backward travelling wave vibration.Because it is unavoidable that various distributed stationary forces act on the disk

the resonance in company with the self exciting stationary wave vibrations is excited during the critical speeds of disk.The resonance

in essentials the self exciting vibration

is the reason for dangerous stationary wave vibration.This is a new conception.The equation for calculating the instabitity of the stationary wave vibration of the disk is also given in the paper.