What is the physics behind cutting a metal rope AKA metal cord.?

Question

My question is multi-part.

1. When you cut a metal rope, what actually happens at an atomic or molecular level? Does the knife slide between molecules or atoms or something? What give a metal it's particular strength, is it due to the density of the material or mass or something else?

2nd part
Assumptions:
1. Ignore the material the knife is made out of. It is the same for both plans.
2. The same exact amount of force is being applied in plan 1 as in plan 2.

Compare 1 & 2

Plan 1: When you cut a metal cord on the ground with a sharp knife, there is a certian physics involved. You are pressing the knife against the metal cord and against a rock or something. It takes a certain amount of force to cut that rope.

Plan 2: What about if the rope is tied between 2 trees. If you apply the exact same amount of force to cut the rope in that scenario is it easier to cut the metal rope? If so, why. Is it because the bonds of the atoms are being weakend or something. If not, why.

Does anyone know the terms that I need to use in order to research this question properly?

Answer 1

I think that you should be looking at the concepts of molecular bonding/crystal structure in determining strength characteristics.
You should be looking at hardness issues, ( also linked to the above) to determine how one material deforms and exceeds the elastic limit of another material to the point of failure. (there is a point of deformation where structure destruction becomes catastrophic and loss of strength is no longer linear)
You are looking at the molecular level for these events.
Tempering, annealing, etc. are metal treating processes that can effect the values existing within your scenarios.

Answer 2

Hi. Most materials tend to be stronger in compression than tension. Pulling your metal rope apart will cause the thinner remaining section to have less cross sectional area, concentrating the force, while at the same time pulling against the forces binding them together.