sliding between blocks

[raffaele.derisi]

Hi all,

is it possible to slide these two blocks one on the other and get a reaction compatible with the friction force (i.e. N*mu)?
As it is now, it does not appear to work correctly.

I appreciate any help you can provide.

Raffaele

[STKO Team]

Try this:

BLOCK_ON_BLOCK.zip

(189.97 KiB) Downloaded 259 times

Issues:

• The triangular time series, used for the cyclic disp history, was used also in the pushover load. This is not possible. When doing disp-control analysis, the controlled loads must have a linear time series
• The "distributed" option in the contact element can be tricky. It is typically used when your contact element is modeling a deformable cohesive zone (not physically modeled). In this case, you give finite stiffness values that will then be multiplied by the tributary size.
  In this case, instead, you assigned penalty values (1.0e9 which is already sufficiently high knowing that your material is about 1e4 and your mesh 1.0e2, the 1.0e9 is already > 1.0e6 which is the typical stiffness value).
  This 1.0e9, with the distributed option, will be multiplied by the tributary size, but since you are modeling in mm, the tributary size is large and increases this number too much introducing numerical instabilities.
  Tip: when using large penalty values, don't use the distributed option
• The input displacement history has very large displacements (400 mm) compared to the expected yield displacement at the given pressure (which is much smaller when the tangential stiffness gets higher!). I reduced it so that you can check it.
• When you have these situations, try to switch off the IMPLEX option. Keep in mind that the IMPLEX option requires small time steps. For example, in your case, you can estimate the time step to be comparable with the yield displacement.
  That would be UY = Fy/Kt = mu*FV/Ky = 0.2*16200/1e9 = 1.6e-5 mm.
• When doing surface-to-surface contact, make the master (stiffer) mesh coarser. I swapped the master-slave surfaces in the interface (I made the steel the master) and made the master mesh coarser