Wire Rope Shearing Force

[jdkuhndog]

Has anybody ever seen published data for the shearing force of wire rope ?

I have an application on an overhead crane in a nuclear facility where they would like to cut the wire rope and drop a load as a last ditch effort. So we are using an Enerpac Hydraulic Cutterhead as our means of cutting the wire rope.

We have done experiments to get a relatively good idea of what forces will be required (prob. about 4200# for 5/16" wire rope and 7500# for 1/2" wire rope). But in the calculations which we will provide to the customer, we really have no means of demonstrating the required force (other than by experience). There seems to be no linear correlation between the force required/effective area/shear modulus.

Any insights would be greatly appreciated.

Thanks !

 

[Chapstick]

Well another thing to consider when shearing a rope/wire/cable is that the load will play a role.

A cable under tension will shear more easily than one that is not. The more the tension, the less shear force required.

Just another thing to complicate your study.

 

[pennpoint]

One more thought. The shape of the shearing edge(s) will also infuence the force required.

pennpoint

 

[CoryPad]

jdkuhndog,

Shear modulus is for elastic deformation, therefore it has no effect on the fracture behavior of interest to you.

If you use the correct cross-sectional area and ultimate shear strength of the wire material, there is no reason you can't get an accurate calculation. The cross-sectional area should be immediately available to you. The ultimate shear strength may not be available - if you can't have it tested, then use 0.6*ultimate tensile strength. Lastly, use a combined stress formula (such as distortion energy/von Mises) to account for combined loading as alluded to above by Chapstick.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ruble3]

Just a thought but can you calculate what the same force would be for a pin or rod the same diameter as the wire rope?
I think manufacturers of NDT equipment for wire ropes have based their equipment on 'metallic area', therefore a 5/16" wire rope is equivalent to a 5/16" rod or pin ( obviously less metal in a wire rope of same diameter but that's factored in)
A search of wire rope non-destructive testing companies may provide some insight

 

[jdkuhndog]

Thanks for the input...I will keep doing research into it.

Cory - if you look at the test data that we do have (portion of it in my first post) you will see that there is no linear relationship between cross sectional area and force required to break as would be anticipated.

Thanks again

 

[CoryPad]

jdkuhndog,

I don't dispute your data. However, it seems that this likely is due to complex loading rather than pure shear. This illustrates the problems associated with initial assumptions, boundary conditions, etc. If you cannot develop a suitable model, prediction is impossible. Therefore, perhaps physical testing is your best method.


Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[RichLeimbach]

I would say that the construction of the wire rope will make some difference also. I think that wire rope of 1x7 construction would be much harder to cut than a 7x19 rope of the same cross-sectional area, since in the 1x7 rope the individual wires you are shearing have much larger size.
I would approach the problem from the perspective of each individual wire being cut. If you can estimate how many strands are being cut at each time by your cutter, I think you'll get a better idea of the forces required.


- Rich