Hello FEAnalyst!
I am currently working on an simulation using PrePoMax/CalculiX and I am encountering some persistent issues with an explicit dynamic analysis and I am struggling to identify the root cause of the problem.
I am trying to simulate the impact of a pneumatic cylinder piston against a cylinder head. To simulate the moving mass, I have applied an initial velocity (v0) of 6000 mm/s to the piston assembly and a point load of 100 N on the piston rod along the axis of symmetry. However, the simulation is failing to give realistic results.
I would be happy to share the model files with you; however, the project exceeds the maximum file size limit for attachments.
Hoping in your help, I look forward to hearing from you.
Best regards
You could use some hosting website. However, the explicit dynamics procedure in CalculiX is very limited and underdeveloped. It has several nasty limitations (especially for 1D/2D elements, so it might be better to use 3D solids) and is (often unusably) slow. Thus, I would recommend using OpenRadioss or implicit solver procedure.
In explicit dynamics, it is crucial to set the incrementation properly. I explained it in this tutorial: https://www.youtube.com/watch?v=-X0Shj7UXE0
But also see this thread on the CalculiX forum: Can't get simple explicit dynamics impact analysis to work - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).
Note that your analysis time is 1.2e-8 s, so the incrementation settings are the key here.
Also, be careful with point loads and make sure that you use amplitudes for all loads/prescribed displacements (because the default amplitude applies the whole load immediately instead of ramping it up linearly like in static simulations).
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