can a very high torque results in bending of a shaft?

[ebyk]

hi everyone
in our plant(wide plate mill)we have a leveling machine to flat the steel plates that have small waves.it has 11 rolls,5in a top cassette and 6 in bottom that are connected to the drive system-electromotor,gear unit&pinion- via 11 cardan shaft spindles.cardan shafts are equipped with safety couplings to protect them from high torque.recently due to mis-operation of the machine a very high torque exerted to cardan spindles causing plastic torsion and bending in 3 spindles.the question is that when we have only pure torsion(no bending or axial force)in the spindles,why they are bended?in other words ,can a very high torque results in bending of a shaft?

 

[desertfox]

Hi ebyk

If the cardan shafts are hollow, then the high torsion that was placed on them could have caused them to buckle, on this link is a shaft that as failed by torsional buckling.

http://www.scribd.com/doc/20945815/3/Torsional-Members

Can you post any pictures of your failed shafts


desertfox

 

[BrianE22]

What sort of angles were on the joints? If the two shafts on either side of the cardan joint are not parallel then you can develop bending moments on the shafts.

 

[MiketheEngineer]

Stuff break all the time from over use or misuse. You just experienced one!!

While I have seen this happen - it usually seems some gear or motor breaks first - but not necessarily!!

 

[dvd]

... as I am sure my neighbors and friends can attest, a little eccentricity goes a long ways.

 

[ebyk]

Thank you,desertfox
Yes our cardan shafts are hollow(dia.170 x tick.12mm)but i think buckling take place in compression members or where there is compressing force .The picture in the link you addressed,f-18
engine shaft,it seems that the shaft is only twisted,because in bucking members there is some deflection perpendicular to axis of member.
Thank you brianE22
The 2 shaft on either side of our joint shaft are horizontal and parallel.you can find attached photo and drawing of joint shaft.
Tank you "MiketheEngineer" and "dvd" for your sympathy.

 

[BrianE22]

Not "joint shaft" but "joint". There looks to be a 4.6 degree angle on the joint shown in the top right view. That would give you a bending moment on the shaft (between the joints) of

M = torque x sine (4.6 degrees)

There may be a joint angle on the shaft in the other plane also. I couldn't quite figure out some of the views.

 

[ebyk]

BrianE22 , for one (cardan) joint you are right .sinusoidal rotation speed and moment on "joint shaft" is normal operation.i think the variable moment on joint shaft is "torsional moment" not "bending moment".so the bending problem is remained.
you can find the exact equation of motion of cardan joint in Wikipedia :

http://en.wikipedia.org/wiki/Universal_joint

The 4.6 degree you mentioned, is inclination angle (beta)of joint shaft.as you can see in the equation of motion , the lower the angle"beta",the variable effect of rotation speed and moment is lower.

 

[desertfox]

Hi ebyk


Look at this article it describes bending moments due to misalignments in the joints:-

http://www.daltonbearing.com/uploadFiles/supplier/brochure_174.pdf

desertfox