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Energy limit reached.

Dear Experts,

In one of my simulations. After half the run time the simulation stopped giving an error that energy error reached. What could be the reason for this? Is it with the time step or could be of anything else!! By the way I am employing AMS in the model.

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Radioss

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Altair Forum User

Hi Raghav,

This energy error can happen due to too low time step because of mesh size or penetrations in structure. Also check for any incompatible kinematic conditions in the model which can result in high energy error.

Please correct them and try running the model.

Altair Forum User

Hi,

I increased the time step and also changed the the stiffness of interfaces as per the recommended values.however the the energy error is showing as 99% which means energy is getting created.. It's against to the expectation in a crash simulation.. As said previously I am using AMS instead of NODA/CST.. Can you suggest some solution. Initially the run is happening and after a few steps it is showing energy error as 99% . I am also using /DT/INTER/DEL and /DT/BRICK/CST ... in the engine file..

My time step is 4 micro seconds. The energy error is shooting up to 99% and the time step has reduced to 1,6e-9 second. However the mass ratio is constant.

What could be the reason for this??

Thanks in advance..

Altair Forum User

Hi Raghav,

Check what is responsible for the low time step (.out file). It can be an element, a node or an interface.

For an element, check the related material.There must not be an error in the units system that this data is given in. check the element size also

For a node, check the characteristics of connected elements. If the node is on the master side or the slave side of an interface, this interface must be verified.

For an interface, the gap of the interface must be verified if some failure happens on the master or the slave side of the interface.

Check the starter out file also for any initial penetrations reported.

Please share the engine out and starter out files.

Altair Forum User

Thanks for the insight . It's because of one of the interfaces. It's a type 7 interface I have made the interface stiff and used recommended parameters for AMS such as Iform to 2 Inactiv 5, Istf to 4 .. Currently I am using a standard gap of 0.5 mm. And with the same parameters it is working with /DT/NODA/CST. So do you think the gap to be increased???

Altair Forum User

Hi,

Set Inacti to 6. Slightly increase the Gapmin and rerun the analysis. Meanwhile share starter out and engine out files also.

Altair Forum User

Hi,

I still have the same problem even after doing implementing inactiv 6 and gap min... I then changed the value for inter /del in engine. And it seems to be working. However after few cycles of run the output file is not getting updated with latest run time data... Any idea why this happens??

Altair Forum User

Hi Raghav,

That can be because of time step dropping. Without the .out (starter and engine) files we will not get a good idea.