Abaqus small sliding vs finite sliding, when to use which one?

[tugni925]

Small sliding assumes there is little sliding between the two contact surfaces, while finite sliding allows for great displacement between the surfaces. Is there a limit when its necessary to use finite instead of small sliding? Say two square surfaces that are in contact are 400 m2 (20m x 20m). Then one of the surfaces slides on the surface by 20 cm - would small sliding then still be viable? Are there any specific guidelines for this?

 

[FEA way]

There's no rule like that, it all depends on particular model. Generally, in most cases we use finite sliding and choose small sliding only when we are absolutely sure that relative sliding of the surfaces involved in contact is very small and can be completely ignored in calculations. Small sliding contact solves faster but may cause large errors when used improperly. What's more, the surfaces should be relatively flat for the small sliding contact to be accurate.

You can use the CSL_NORMALIZED output variable to determine whether the assumption of small sliding is appropriate for particular case. If its value is higher than 0.5 then small-sliding may not be a good choice.

 

[tugni925]

So if this value is lower than 0.5, say its 0.1, but the surfaces in contact are not flat, they bend for example. Do you think I can use small sliding?

And can I use CSL_NORMALIZED output variable if im using surface-to-surface contact? Is there an equivalent output I can use, for example CDISP?

 

[FEA way]

In the case of small sliding formulation, the master surface is approximated as a planar surface. The more curved the actual surface, the lower the accuracy of this approximation. That’s why it’s not recommended to use small sliding in case of surfaces with relatively large curvature.

The CSL_NORMALIZED output variable is available for general contact and is calculated as CSLIPEQ divided by the normalization distance.

 

[DanStro]

I too almost always use finite sliding. But if I want to look into whether small sliding might be appropriate the criteria I use is based on how much movement there is between contacting nodes. If they move less than 1/2 the mesh size than that I might try it. It's not a hard and fast rule but it should be in the ballpark in most cases.