I am doing an Explicit Impact Analysis on GFRP component. I am getting an error message saying "Minimum Time Step too small". Can anyone please tell me how I should solve this error? According to the Ansys manual, I tried to change the Erosion Controls by changing the Geometric Strain Limit. The problem is solved temporarily, but I am not understanding what exactly this Geometric Strain Limit signifies. What happens when I increase or decrease the value of the Geometric Strain Limit?
in explicit dynamic --> analysis setting --> maximum energy error = a big number like 1e6 and time step safety factor = 0.5
Hello Rushb
If you are controlling the time step yourself, suggest to start with 0.01, with min time step being 0.001...
Do not adjust strain yourself...
Check for type of element and its capability too...
Rgds
LR
If you are performing a transient analysis with an explicit scheme, the solver stability requires a time step small enough that depends in particular on your mesh discretization and global stiffness
I suppose Ansys has a tolerance where the time step it found regarding your total simulation time will be too long. You have to figure out that changing the order of your time step can generate extremely long simulations from the hour scale to the year scale, so that it is better to stop.
The geometric strain limit is a numerical feature that looks like it bounds the geometric hardening effect induced by the large deformations, so this limits your global stiffness increase and thus the decrease of time step required for your solver stability during the simulation.
You may however get a bad solution as your are modifying your model properties by doing so. Imagine that after a certain threshold the geometric stiffness will not vary anymore.
I would suggest testing a coarser mesh and checking your system properties regarding the stresses generated by the impact to see if you are in physically acceptable values. Using a quadratic mesh would also help in the accuracy of your stress fields.
Hello
To overcome the error massage "Minimum Time Step too small" during dynamic analysis in AUTODYN, go to "controls" and set min time step to zero.
Regards
MMA
I faced this problem recently. To overcome the issue of the "Time step too small" in explicit dynamics, I changed the mesh and make it more uniform with no elements much smaller than others. In general I think the solution of this type of problem is to check the mesh for any small/nonuniform elements that could affect the run time because the run time in explicit dynamics depends directly on the element size, the smaller the element the higher the probability of this error.
Hope this Helps.
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