Allowable shear stresses in shafts 1

[lukem]

When designing a hollow circular drive shaft, what is the allowable shear stress in the shaft? How does the allowable shear stress relate to UTS or yield strength of the material (in this case 304 S/S)? Is it correct to say that the allowable shear stress is independant of cross section because it is a material property?

Background:
We had a drive shaft fail and I am trying to work out the allowable torques in some components of the drive system to make sure that all components are matched correctly, but need the allowable shear stresses to do this.

Thanks.

 

[corus]

Design stresses are commonly equal to 2/3 yield stress and the allowable shear stress is normally half the design stress. Allowable stresses are independent of shape, yes.

If you've had a shaft fail then the probable cause is fatigue of a rotating component. You need to look at where it failed and what the stress concentration is there. There are additional factors you also need to consider such as surface finish, size of the component etc. when looking at fatigue. When the stress is calculated then compare that with the fatigue stress limit in rotating bending.

corus

 

[drgauf]

304 stainless can mean so much, be specific, manufacturer, state, location and time of manufacturing.

Also look at the storage time and conditions of the stock. I fthe world was perfect than 304 would be also!!