About the critical speed of the drive shaft of the plum coupling

　　The drive shaft of plum coupling is often affected by structural asymmetry, inhomogeneity of material organization, manufacturing and assembly errors, etc., and centrifugal inertia force will be generated when rotating.This inertial force is a periodic interference force, which will inevitably cause lateral vibration of the drive shaft.When the frequency of this interference force coincides with the natural frequency of the drive shaft, bending resonance will occur.At this time, theoretically, the amplitude (deflection) of the drive shaft will increase indefinitely. In fact, due to the internal friction of the sub-shaft material and the limiting effect of the surrounding medium, the amplitude of the shaft will not immediately increase indefinitely, but it is also restricted by the internal friction of the sub-shaft material and the limiting effect of the surrounding medium. It will increase considerably, and in severe cases it will cause the drive shaft to break.

　　The rotational speed at which the drive shaft of the plum coupling resonates is called the critical speed of the drive shaft.The drive shaft of the plum blossom coupling can be regarded as a shaft hinged at both ends.It should be pointed out that the critical speed of the above-mentioned transmission shaft is obtained under the condition that the two ends of the transmission shaft are assumed to be hingedly supported, and the cross-sectional dimensions along the full length L of the shaft are the same, but the actual sunny conditions are different from the assumed ones. In addition, the static state during manufacturing , Dynamic balance accuracy and wear and other factors will affect the actual critical speed