# What does traction free mean?

1. Mar 14, 2006

### leoflc

What does "traction free" mean?

What does "traction free" mean?
Is it a boundary condiction that there's no stress action on that boundary?

Or...?

Thanks a lot!

2. Mar 14, 2006

### enigma

Staff Emeritus
It would probably depend on the context, but it sounds like 'frictionless' to me.

3. Mar 14, 2006

### leoflc

Thanks for the reply!
But I have seen it in "finding stress" type of problem.
Not quite sure how to fit "frictionless" into it..

Maybe there are other meaning?

4. Mar 14, 2006

### enigma

Staff Emeritus
There probably is, which is why I mentioned the context. I've never seen that term used before. Can you give an example of a problem which mentions it?

5. Mar 14, 2006

### leoflc

I can't really find any good example.
But I often heard when people say something like:

"Drilled a round hold in the middle of an infinite big plate. If a point that was at 3oc' position of the hold was picked (on the edge), the negative x-direction of the point is traction free."

I can't really explain it very well, hope that will work..

Thanks a lot!

6. Mar 14, 2006

### FredGarvin

Traction sounds like it is longitudinal force in your example. It kind of fits if you think of traction, as in a person in a hospital bed "in traction." It is pretty lousy terminology if you ask me.

7. Mar 14, 2006

### Stingray

I think that traction refers to force applied tangent to a surface.

8. Mar 14, 2006

### leoflc

Thanks for the replies..
So it's probably referring some kinda of direction with no force/stress, or no stress on the surface..?

That kind of makes sense.

9. Mar 15, 2006

### brewnog

Traction is a well defined term in mechanics.

However, I can't quite remember what it is.

Stingray touched on it. It's a vector quantity, but it has to be specific to a surface (ie you can't translate it along the vector's direction). Note that a surface doesn't have to be a literal surface, - it can also refer to an imaginary surface taken by sectioning the solid.

If you have a tractionless boundary condition, then loosely yes, there is no stress applied on the surface boundary in question.