# Uniaxial Compressive Test (UCS) code

**URL:** <https://forum.itascainternational.com/t/uniaxial-compressive-test-ucs-code/307>\
**Category:** UDEC\
**Created:** [March 2, 2022, 6:01am UTC](https://forum.itascainternational.com/t/uniaxial-compressive-test-ucs-code/307 "2022-03-02T06:01:32Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Akash77skyz](https://avatars.discourse-cdn.com/v4/letter/a/8dc957/32.png) [@Akash77skyz](https://forum.itascainternational.com/u/Akash77skyz)\
**Post date:** [March 2, 2022, 6:01am UTC](https://forum.itascainternational.com/t/uniaxial-compressive-test-ucs-code/307/1 "2022-03-02T06:01:32Z")

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Can someone send here the code/data file for UCS test in UDEC 6. Thanks a lot.

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**Author:** ![ddegagne](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.itascainternational.com/ddegagne/32/55_2.png) [@ddegagne](https://forum.itascainternational.com/u/ddegagne)\
**Post date:** [March 8, 2022, 6:25pm UTC](https://forum.itascainternational.com/t/uniaxial-compressive-test-ucs-code/307/3 "2022-03-08T18:25:27Z")

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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).

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**Author:** ![Akash77skyz](https://avatars.discourse-cdn.com/v4/letter/a/8dc957/32.png) [@Akash77skyz](https://forum.itascainternational.com/u/Akash77skyz)\
**Post date:** [March 23, 2022, 8:20am UTC](https://forum.itascainternational.com/t/uniaxial-compressive-test-ucs-code/307/4 "2022-03-23T08:20:43Z")

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@ddegagne Thank you for the advice.