Can someone send here the code/data file for UCS test in UDEC 6. Thanks a lot.
For uniaxial testing simulations we general use a very-low velocity boundary condition for the specimen top/bottom to represent the platens and then apply a stress boundary to the sample left/right edges for triaxial confinement cases. It’s important to use a very-low platen velocity (e.g., 1e-5 m/s) else the model can start to behave dynamically and not be a good representation. However, you want to avoid unnecessarily low velocities so the model doesn’t take longer than it needs to. You want to select a velocity and then repeat the test at a different magnitudes (higher or lower) and create and inspect it’s stress-strain curve history. If the response is stronger than the base case, its behaving dynamically (also look to see if you’re getting crushing – plasticity – primarily along the platens). When you find a velocity that produces the same response regardless of low slow the platens are – you know you’re safe with the previous velocity tested that gives same result. At this point you can also try half-magnitude changes – if want to try and speed up a bit more – but if run time is reasonable, just go with it as is. Of course, for unloading we can reverse the platen velocities.
While the above is more common, sometimes a servo-control model might be desirable (and avoids checking velocities). This is a bit more advanced on the FISH side though.
You can see a number of material testing type examples in the UDEC 7 Manual PDFs (under the UDEC Help menu) – specifically Section 1: Block Constitutive Models (e.g., Example 1.6).
@ddegagne Thank you for the advice.