Calculating Tensile Strength

[Chairs]

We are using a 100 ton Ram to break steel cables. How would you calculate the tensile strength of the Cable using only the gauge pressure? I'm also having a problem because it seems that the pressure required to simply move the Ram is adding to the pressure required to break the cable. Does that even matter once you start pulling on the cable itself?

 

[btrueblood]

Yes, it matters. The friction will also increase once the ram starts to see some load, and the cylinder pressure rises. You could likely map the output load vs. cylinder pressure, but that implies a device that measures the output load (google "load cell").

 

[Chairs]

Yeah we already have a load cell in mind. I just wanted to calculate the tensile strength with the gauge pressure first to see how close it is to what its rated for before we go ahead and spend the money. Is there a fairly accurate way to calculate it?

 

[btrueblood]

You need to know the piston cross section area (or diameter) and rod XC area (diameter). Force on rod = Prod x (piston area - rod area) - Pcylinder x( piston area) - Ffriction, where Prod is the rod side cylinder pressure, and Pcylinder is the pressure on the opposite side of the piston. Put a gage on both the rod side and the opposite side of the piston, so you can see if there are some things happening in the hydraulic circuit that affects the pressure required to create first motion.