Calculating Pressure Applied via Threads
Calculating Pressure Applied via Threads
(OP)
We want to calculate the pressure we apply to a piece of tube via a set of squeeze rolls. The rolls are in a vise like stand. Question; If I know the amount of pounds being applied to the the threaded rod (via torque wrench) can I then calculate the force being applied to the squeeze rolls? If I need to be clearer please let me know what info you would need.





RE: Calculating Pressure Applied via Threads
If the force applied to the threaded rod doesen't get magnified in any way and is the force directly applied to the squeeze rollers then yes that is the force crushing the tube.
The difficulty I see in calculating the pressure on the tube being squeezed is the contact area between that and the squeeze rollers.
regards
desertfox
RE: Calculating Pressure Applied via Threads
RE: Calculating Pressure Applied via Threads
With a 4" offset between threads and centre of the tube you will encounter a bending moment and without seeing the set up I cannot comment on how rigid these squeezing rolls are.
However now you mention crushing the tube till the weld fails, have you considered calculating the strength of the weld on the tube and thus arriving at a theoretical pressure that the weld will fail at.
I can help you along those lines however I would need the type of weld, size and wall thickness of tube and material you are using, in addition how is the weld loaded in service.
Once you have a theoretical figure you can still test the weld the way you have been doing and compare results.
regards desertfox
RE: Calculating Pressure Applied via Threads
RE: Calculating Pressure Applied via Threads
The tube is 1.000" in diameter x .110 gage and the material is c1018 Steel. The weld is actually a "forging" We use induction to heat the strip edges then they are pressed together with a 3 roll weld box. The ID and OD beads are removed. This is all done continuously on a tube mill. The weld is located at 0 degrees based on the squeeze rolls being at 90 and 270.
RE: Calculating Pressure Applied via Threads
I am looking at some formula which may help you with your problem, however the formula I have is for tensile loading of thick and thin rings as your compressing the tube in two places then the mode of failure will be buckling of the tube
which will occur at a lower value than these formula will probably predict.
From your last description it seems that your producing tubing with a seam which if I am correct there should be standards for testing this product?
Can you confirm how this tube will be loaded in service, because if this tube is subjected to either internal or external uniform pressure then the calculation becomes a lot easier and your current method of testing by crushing at two diametrically opposite points is not representative of service conditions.
regards
desertfox
RE: Calculating Pressure Applied via Threads
As an alternative you might consider measuring strain of the sample and calculating the resulting stress at failure. Those equations would be use fewer uncontroled variables.