# How to set the displacement function (sin (time)) for a grid

**URL:** <https://calculix.discourse.group/t/how-to-set-the-displacement-function-sin-time-for-a-grid/1268>\
**Category:** Uncategorized\
**Created:** [September 20, 2022, 1:25pm UTC](https://calculix.discourse.group/t/how-to-set-the-displacement-function-sin-time-for-a-grid/1268 "2022-09-20T13:25:47Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![daxiangxiang](https://avatars.discourse-cdn.com/v4/letter/d/d9b06d/32.png) [@daxiangxiang](https://calculix.discourse.group/u/daxiangxiang)\
**Post date:** [September 20, 2022, 1:25pm UTC](https://calculix.discourse.group/t/how-to-set-the-displacement-function-sin-time-for-a-grid/1268/1 "2022-09-20T13:25:47Z")

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Good morning all

How do I set motion functions for nodes?

I want to set a driver function (y=sin (time)) for nodes on one of the faces of the model,in order to move the model up and down. I have found a way to set a.txt file to load Amplitude, but in this way, I need to write a.txt file. ([Possible to provide external file as input for loads?](https://calculix.discourse.group/t/possible-to-provide-external-file-as-input-for-loads/442))

Question：Can I input it directly as a function? For example: \*AMPLITUDE=sin (t)?  
Or is reading TXT the only way?  
Thanks

Best regards

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**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\
**Post date:** [September 20, 2022, 1:55pm UTC](https://calculix.discourse.group/t/how-to-set-the-displacement-function-sin-time-for-a-grid/1268/2 "2022-09-20T13:55:06Z")

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Abaqus offers periodic amplitude type for such purposes. In CalculiX you would have to define the amplitude in standard tabular form:

```auto
*AMPLITUDE
time1, amplitude1, time2, amplitude2, …

```

or use the uamplitude.f subroutine.

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<div class="post-metadata">

**Author:** ![daxiangxiang](https://avatars.discourse-cdn.com/v4/letter/d/d9b06d/32.png) [@daxiangxiang](https://calculix.discourse.group/u/daxiangxiang)\
**Post date:** [September 20, 2022, 2:18pm UTC](https://calculix.discourse.group/t/how-to-set-the-displacement-function-sin-time-for-a-grid/1268/3 "2022-09-20T14:18:25Z")

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Thank you very much，I’ll give it a try