tube bending 1

[toolman87]

I want to use a hydraulic cylinder to bend a tube.  Is there a formula to use to calculate bend pressure of mild steel tubing.

 

[ecampos]

Yes. Perhaps you can use the simple equation for bending.&nbsp;&nbsp;sigma=load*distancefromcentertoappliedload/areamomentI<br>If you know your materials properties, then you can figure out what load it will take to exceed the yield strength of the tube.&nbsp;&nbsp;This should be the theoretically correct force.&nbsp;&nbsp;I would add a litle more to be certain, it bends.<br><br>sigma is in psi. so is the yield.<br><br>Let me know if you need anymore help.<br>

 

[DonLeffingwellPE]

The above POST is recomending that you use the fexure formula for a beam in bending.<br><br>stress = Mc/I<br><br>M is the maximum Moment applied to the beam <br>c&nbsp;&nbsp;is the centroidal distance to the top of the beam. Use tube radius<br>I is the moment of inertia for the tube. (pi/4)*(ro^4 - ri^4)<br><br>Look in your Machinery Handbook under Strength of Materials.<br><br>Don Leffingwell PE<br><A HREF="mailto:dleffingwell@snet.net">dleffingwell@snet.net</A>

 

[MikeVV]

The formula referenced is applicable to bending up to the yield point of the material.&nbsp;&nbsp;Beyond that point, plastic deformation (permanent) occurs and the formula will predict higher forces than actual which, if you are only sizing for worst case loads, should be acceptable.&nbsp;&nbsp;Several other factors could affect your situation however.&nbsp;&nbsp;The ratio of the bend radius to the pipe diameter will affect the loads and final shape of the bend pipe.&nbsp;&nbsp;If the bend radius is too small, the pipe will buckle at the bend.&nbsp;&nbsp;This ratio also affects the permanent deformation of the pipe and cracking can occur if any part of the bent pipe experiences strains in excess of its capability.&nbsp;&nbsp;The loads are also a function of the amount of bend (degrees).&nbsp;&nbsp;Most common steel has a relatively large region in which permanent deformation can occur without failure.&nbsp;&nbsp;Some steels, particularly those that are high strength, have a smaller region and may crack during bending.&nbsp;&nbsp;Pipe steels could fall into this range.&nbsp;&nbsp;Steel tubing is designed for bending and the manufacturers will provide bending information.<br><br>Mike Van Voorhis<br><A HREF="mailto:MJVanVoorhis@CS.com">MJVanVoorhis@CS.com</A><br>&nbsp;