Hi,

I am working on a frequency study for a long pump drive shaft.

I have used a fixed hinge constrain on all radial surfaces of the drive shaft.

This is the function of the fixed hinge constrain according to help:

Use the Hinge restraint to specify that a cylindrical face can ONLY rotate about its own axis. The radius and the length of the cylindrical face remain constant under loading.

This condition is similar to selecting the On cylindrical face restraint type and setting the radial and axial components to zero.

As shown here the result i get have a changed radius and length???? how is this possible? (shorter and thicker)

(original shape on the left / result frequency analysis on the right)