Distorsion of HSS Tube

[rapps]

Can someone please offer there insite, here is my situation:

HSS TUBE 4" x 4" x .500"w x 220" Long
Has been machined on 2 sides the full length of the tube with a strip 1" wide by .250" deep.

The HSS was flat when shipped. Was shipped in a truck and sat in the truck for approx. 2 hours at 0 Degrees Celsius (32Fa). The beams were off loaded from the truck and placed on a cart (approx 3ft x 4ft) in the middle of the
beam, inside at room temperature. The beams are now bowed (close to 1") from one side to the other.

I am not an expert on the states of steel or the changing properties of HSS tubing but is it possible and can distortion this extreme happen with the conditions listed above?

 

[rapps]

Forgot to add that there was aprox. 5-10LBS steel brackets welded on either both ends.

 

[desertfox]

Hi rapps

I suspect that the steel tube warped because after machining the residual stresses locked up in the section redistribute themselves.

desertfox

 

[desertfox]

Hi again

Also the welding of the brackets would cause distortion, how do you know the HSS was flat when it was shipped?

desertfox

 

[rapps]

the tube was indicated when machining, the handling was from machine to floor (flat) not placed on horses or wood, simply layed on the concrete.

 

[Compositepro]

Was it clamped down for machining when it was indicated? The tube is flexible so how does the distortion affect the function of the tube? Will it be clamped to other structure so it will be whatever shape it gets clamped to?

 

[rapps]

at this point it cannot be used because a linear rail will be bolted onto the machined flats.

 

[desertfox]

Hi rapps

You need to provide more information ie :- a sketch or drawing would help and some information about what the tube is being used for, drip feeding the information post by post isn't helping us to help you.

desertfox

 

[rapps]

i will post a drawing on monday

 

[desertfox]

hi rapps

Just done a quick calclation, assuming the beam was uniformly loaded ie by its own weight and simply supported, I get a deflection of nearly 11" at the centre, however the stress is still within the elastic range and therefore should not have a permanent set, so I believe if you have distortion on a permanent basis this would have occured during manufacture.
Please check my calcs I did it in a hurry in my lunch break.

Desertfox

 

[arunmrao]

How were the pieces clamped during machining. Was the machining done in stages? Also finally for the finish cut,were soft jaws used. There has been a buildup of internal stresses during machining resulting in a permanent bow.