Shaft Design

[Charlesi]

This may seem like a simple problem but is causing me some grief. Can anyone explain the modes of stress experienced by a shaft under bending and torque. The easy ones are normal bending stress and torsional shear stress. What about direct shear stress and transverse shear stress? From what I understand direct stress occurs in colinear members (members not bending), and transvers stress occurs in members that are experiencing bending but occurs as a maximum in the centre of the shaft and zero on the surface.


Thanks

 

[cranekiran]

Hi,

What you are saying is correct from a theorytical point.What actually happens practically would be a combination of direct stress,bending & shear.Depends on the application & the type of valve.

See,In the case of a wedge type of gate valve you have axial forces & bending forces acting on the shaft.

In case of Butterfly valve It is a combination of Torque & bending.

You have to analyse the forces acting on your application before calculating the dia. or material of your shaft.

The rest are simple undergraduate design calculations.

Hope this Helps.

Cheers!

 

[ibrahimdemir]

Hi Cranekiran and others,

In case of large size of butterfly valves, how do you determine the torsion on the shaft?
Do you have a chart, formula or test results to determine moment on the shaft under different attack angle of the valve disk?
I am looking for this information for the buterflt valves with ordinary and biplane disks. Any suggestion and help welcome.

Thanks in advance.

Ibrahim Demir
Design Engineer
Clyde Babcock Hitachi
idemir@cbh.net.au