crimping a small diameter tube 1

[rs8220]

Hi,
I'm trying to calculate the approximate force required to squash a small diameter tube - similar to crimping a ferrule on to a wire. The forces from the crimp tool can be approximated as a load distributed along the top and bottom of the tube, but not distributed around the circumference.

The crimp tube dimensions:
OD = 1.0mm
ID = 0.5mm
length = 10mm
Material = stainless steel

How can I calculate the force required to start to deform the tube?

Thanks for any guidance!

 

[desertfox]

Hi rs8220

Not the perfect solution however it might get you started.
First assume a single point load acting top and bottom and calculate the tensile stress on the outside diameter and the compressive stress on the inside diameter from standard bending formula ie:-

stress = M*y1/I tensile outside diameter

stress = M*y2/I compressive inside diameter

where y1 and y2 are inside and outside radius respectively

the max stresses occur at 90 degrees to the applied load.
I would start with the yield stress for the inside tube diameter and transpose the bending stress formula to get the required bending moment to generate that stress and hence from there get the required point load.
Obviously you will need more load than calculated because of the tube length and possible work harding of the material as it is crushed but with a little bit of trial and error you can adjust the calculated value to achieve what you want.

desertfox

 

[rs8220]

Hi desertfox,

Thanks for your quick response. I followed your suggestion and ended up with a bending moment required for the tube. I could compare this bending moment to one calculated from dimensions and material spec of standard crimps. I'm fairly happy that a standard crimp tool should be able to apply the required force to deform the tube.

cheers,
Rich

 

[desertfox]

hi rs8220

Your welcome.

desertfox