# Amplitude function error **URL:** \ **Category:** Uncategorized\ **Created:** [June 15, 2023, 2:16pm UTC](https://calculix.discourse.group/t/amplitude-function-error/1708 "2023-06-15T14:16:58Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![daxiangxiang](https://avatars.discourse-cdn.com/v4/letter/d/d9b06d/32.png) [@daxiangxiang](https://calculix.discourse.group/u/daxiangxiang)\ **Post date:** [June 15, 2023, 2:16pm UTC](https://calculix.discourse.group/t/amplitude-function-error/1708/1 "2023-06-15T14:16:58Z")
Hi， I was using calculix, precice, openfoam to implement fluid-structure coupling and was having strange problems running calculix, so I tried to run calculix’s inp file separately and the inp file looked like this: ```auto *INCLUDE, INPUT=all.msh *INCLUDE, INPUT=fix1.nam *INCLUDE, INPUT=surface.nam *MATERIAL, Name=EL *ELASTIC 5.6000E+6, 0.4 *DENSITY 1000 *SOLID SECTION, Elset=Eall, Material=EL *STEP, INC=1000000 *DYNAMIC, ALPHA=0.0, DIRECT 0.0005, 0.5 *BOUNDARY Nfix1, 1, 3 **------The "MyTimeFunction-sin-fun.txt" file is a sin function and the "mynewamplitude-line-fun.txt" file is a linear function. **------File "MyTimeFunction-sin-fun.txt" runs incorrectly, and file "mynewamplitude-line-fun.txt" runs successfully. *AMPLITUDE,NAME=MyAmplitude *INCLUDE, INPUT="MyTimeFunction-sin-fun.txt" **INCLUDE, INPUT="mynewamplitude-line-fun.txt" **0,0,0.36,0.05 *BOUNDARY,AMPLITUDE=MyAmplitude Nfix1, 2, 2 ,1 *CLOAD Nsurface, 1, 0.0 Nsurface, 2, 0.0 Nsurface, 3, 0.0 *NODE FILE U *EL FILE S, E *END STEP ``` **The diagram below is a schematic of my simulation model** ![0000](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/3/32092fbfdfbbf3d4465d0e1c9f8e9e95e71b9792.jpeg) **The question is this:** Give the fix1 node set a **sin function** displacement amplitude, the plate produces a chaotic motion: ![error1](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/a/ac13d8c7ab797159e4b58c59671038d2f76933cc.jpeg) Given the fix1 node set **linear function** displacement amplitude, the plate moves normally: ![linear-correct](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/9/992b19aebccc8b4f0500607f0540916fd8c4f4f7.jpeg) I used the **same inp fil** e and changed **only** these three lines of code,but the results varied widely.What is the reason for this? ```auto *AMPLITUDE,NAME=MyAmplitude *INCLUDE, INPUT="MyTimeFunction-sin-fun.txt" **INCLUDE, INPUT="mynewamplitude-line-fun.txt" ``` **MyTimeFunction-sin-fun.txt** file looks like this： ```auto 0,0 0.0005,0.000125 0.001,0.000249999 0.0015,0.000374996 0.002,0.000499992 0.0025,0.624985 0.003,0.000749972 0.0035,0.000874955 0.004,0.000999933 0.0045,0.001124905 0.005,0.00124987 ...... ``` **mynewamplitude-line-fun.txt** file looks like this： ```auto 0,0 0.0005,6.94E-05 0.001,0.000138889 0.0015,2.08E-04 0.002,0.000277778 0.0025,3.47E-04 0.003,0.000416667 0.0035,4.86E-04 0.004,0.000555556 0.0045,0.000625 0.005,6.94E-04 0.0055,0.000763889 0.006,8.33E-04 ...... ``` The simulation files are stored here: [https://drive.google.com/drive/folders/1PQcixcik2-4xOIXbKCXKt1DsvhPx0TwI?usp=sharing](https://drive.google.com/drive/folders/1PQcixcik2-4xOIXbKCXKt1DsvhPx0TwI?usp=sharing) Any help is appreciated! xiangxiang ---
**Author:** ![daxiangxiang](https://avatars.discourse-cdn.com/v4/letter/d/d9b06d/32.png) [@daxiangxiang](https://calculix.discourse.group/u/daxiangxiang)\ **Post date:** [June 15, 2023, 2:23pm UTC](https://calculix.discourse.group/t/amplitude-function-error/1708/2 "2023-06-15T14:23:01Z")
The running results of the two functions (sin and linear) are stored here, which is the result file of steps 0-100 **Very strange results** : [[linear-fun.avi - Google Drive](https://drive.google.com/file/d/11u6fqta-90jj5LYcmORQolXFR8VKG-XS/view?usp=sharing), [sin-fun.avi - Google Drive](https://drive.google.com/file/d/19R6n-hIrtUsvJKWvXnO_FZ5U4osSmiED/view?usp=sharing)] ---
**Author:** ![daxiangxiang](https://avatars.discourse-cdn.com/v4/letter/d/d9b06d/32.png) [@daxiangxiang](https://calculix.discourse.group/u/daxiangxiang)\ **Post date:** [June 15, 2023, 2:27pm UTC](https://calculix.discourse.group/t/amplitude-function-error/1708/3 "2023-06-15T14:27:58Z")
Different attempts: I tried to modify the time step and elastic modulus, which did not seem to be the cause of the problem, because I only modified the \*AMPLITUDE function. ---
**Author:** ![fgr](https://avatars.discourse-cdn.com/v4/letter/f/f4b2a3/32.png) [@fgr](https://calculix.discourse.group/u/fgr)\ **Post date:** [June 15, 2023, 6:57pm UTC](https://calculix.discourse.group/t/amplitude-function-error/1708/4 "2023-06-15T18:57:38Z")
@daxiangxiang Your sine function has some weird errors, look below, I believe if you correct these values the sine function will run comparable to your line function. ```auto 0,0 0.0005,0.000125 0.001,0.000249999 0.0015,0.000374996 0.002,0.000499992 0.0025,0.624985 <<<<<< value doesn't belong to the sine function 0.003,0.000749972 0.0035,0.000874955 0.004,0.000999933 0.0045,0.001124905 0.005,0.00124987 0.0055,0.001374827 0.006,0.001499775 0.0065,0.001624714 0.007,0.001749643 0.0075,0.001874561 0.008,0.001999467 0.0085,0.212437 <<<<<< value doesn't belong to the sine function 0.009,0.002249241 ``` ---
**Author:** ![daxiangxiang](https://avatars.discourse-cdn.com/v4/letter/d/d9b06d/32.png) [@daxiangxiang](https://calculix.discourse.group/u/daxiangxiang)\ **Post date:** [June 16, 2023, 2:17am UTC](https://calculix.discourse.group/t/amplitude-function-error/1708/5 "2023-06-16T02:17:51Z")
Thank you, Sir. I will carefully examine the cause of the problem. Have a good weekend.