# Help with setting up the analysis

**URL:** <https://prepomax.discourse.group/t/help-with-setting-up-the-analysis/2267>\
**Category:** General Questions\
**Created:** [December 16, 2024, 9:25am UTC](https://prepomax.discourse.group/t/help-with-setting-up-the-analysis/2267 "2024-12-16T09:25:22Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Alueks](https://avatars.discourse-cdn.com/v4/letter/a/a88e4f/32.png) [@Alueks](https://prepomax.discourse.group/u/Alueks)\
**Post date:** [December 16, 2024, 9:25am UTC](https://prepomax.discourse.group/t/help-with-setting-up-the-analysis/2267/1 "2024-12-16T09:25:22Z")

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Hi,

I will upload my prepomax file and would like some help if possible.  
Is it set correctly?  
And why when I run it, my reaction forces are incredibly low, plus when I increase the displacement from 4mm to 5mm, it doesn’t coverge.  
Plus how can I put the displacement agaist the force.

[https://fileport.io/GkHLzwecBKX6](https://fileport.io/GkHLzwecBKX6) - file is too big to upload here.

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**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\
**Post date:** [December 16, 2024, 9:42am UTC](https://prepomax.discourse.group/t/help-with-setting-up-the-analysis/2267/2 "2024-12-16T09:42:59Z")

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You have a boundary condition on the contact surface, this should be avoided. You may need a different modeling approach here because of that. Maybe make the pin rigid or even exclude it and use the compression-only constraint instead: [https://www.youtube.com/watch?v=yYuvUbu6Sw8](https://www.youtube.com/watch?v=yYuvUbu6Sw8)

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**Author:** ![Gunnar](https://avatars.discourse-cdn.com/v4/letter/g/ed655f/32.png) [@Gunnar](https://prepomax.discourse.group/u/Gunnar)\
**Post date:** [December 17, 2024, 10:54pm UTC](https://prepomax.discourse.group/t/help-with-setting-up-the-analysis/2267/3 "2024-12-17T22:54:51Z")

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You requested the reaction force on the slave surface. For contact this does not work, instead you shoud select the fixed edge and select “Totals - only” to sum up all node values. The summed Y-Forces at the edge should then be similar to FN of the requested contact output CF (not necessary to select “Total - only” here).  
In the same output, you requested U for this node set. Instead you should create a separate node output and select only one suitable slave node here. Unfortunately, in prepomax you cannot choose any other node output for the x-axis than time (would be nice to have this feature like in paraview). So you need to copy the results of these two outputs for x and y and plot the curve in excel.

You selected a Time period of 120s and initial time increment of 0.2s. I don’t quite understand, why don’t you leave the period at 1s and reduce the increments accordingly? It’s just a static step. Also the specified amplitude of 0,0/120,1 is redundant.

I wonder why the mesh is so extremely fine. Of course, a finer mesh generally leads to more accurate results, but in this case i would start with a significantly coarser mesh. It doesn’t really help speed up convergence if this was your intention.

I had no convergence problem with your selected BCs.

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**Author:** ![Alueks](https://avatars.discourse-cdn.com/v4/letter/a/a88e4f/32.png) [@Alueks](https://prepomax.discourse.group/u/Alueks)\
**Post date:** [December 18, 2024, 8:27am UTC](https://prepomax.discourse.group/t/help-with-setting-up-the-analysis/2267/4 "2024-12-18T08:27:14Z")

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My real life experiment the max distance was 4.6mm and max force 27.6 kN. So It took around 150secs to reach that. I thought using this time period and the specified amplitued that it will match the tensile machine or I am in big mistake/ not understanding of PrePoMax