Design criteria for polyurethane/rubber coated steel roll

[kavkir]

Hallo everybody!

I have a task to calculate the thickness of the polyurethane or rubber coating to be applied to the steel core of a roll. The roll to be used to transport heavy pipes. The polyureathane liner will be casted over the steel body.

Could anyone suggest me what design criteria should I use for my FEA calculations? Should it be max. stresses in the PU material or shear stresses at the adhesive layer with the steel core?

The hyperelastic material model I have already.

Thanks in advance!

Regards,
Kavkir

 

[SacovanLoon]

I did a calculation on the same problem. At the time i did not have access to a non linear solver. I did it in Excel. The problem with a layer of polyurethane on steel is the shear stress in the layer where the polyurethane is connected/cured to the steel. There in most cases the system fails. The bond is lost and the polyurethane is destroyed.
It is a matter of costs. More Poly > more expensive.
From memory i say the deformation of the PU should be limited to 30% of the original thickness.
I calculated the area (an oval) where the polyurethane was compressed. The two cilinders approach eachother untill the polyurethane is deformed enough to build up resisting pressure.
If you need more info i have to search my files. Please let me know what your findings are.

 

[kavkir]

Thank you SacovanLoon !

Well, according to our PU coating supplier, they advise the deformation not higher than 20% of original thickness.

Indeed, the adhesion strength (shear stress at the interface) is driving in this case.
Now I am trying to evaluate the allowed shear stresses based on the peel test results (available), however, it seems that really there is no any straight forward method to relate these two values... Keep looking.

It is also true - thicker the coating better it is, but
we have some space restrictions. The diameter of the steel core plays also an important role.

By the way, have you used a Hertz model to evaluate the stresses in the coating?

 

[SacovanLoon]

No, a model loosely based on Topaloff. I want to mention again that the stresses in the polyurethane are not the limiting factor. The connection to the bearing material is!

Do you have the possibility to make the roller in a V shape? This will increase the surface in contact with the pipes.

 

[kavkir]

Probably I wasn'n clear enough. I do not mean the stresses in the PU itself, but the stresses in the adhesion. Yes, I can make them in Vee, but it does not help a lot since I have an objective to maximixe the lifetime and minimize the costs and dimensions.