Energy Error Limit Reached

Altair Forum User

Hi,

 

I want to do a structural analysis using RADIOSS. I get the following Error message:

 

** WARNING ZERO OR NEGATIVE VOLUME : 3D-ELEMENT ID : 508967
   ELEMENT IS SWITCHED TO SMALL STRAIN OPTION
MESSAGE ID :          205
 ** RUN KILLED : ENERGY ERROR LIMIT REACHED
 NC=    1076 T= 1.0760E-02 DT= 1.0000E-05 ERR= 99.9% DM/M= 3.5526E+07
 ELAPSED TIME=         70.55 s  REMAINING TIME=       1896.46 s
     ANIMATION FILE: PS5x15_RADIOSSA006 WRITTEN

 

Where does this error come from? How can I avoid it?

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Simon Križnik

Hi @PhilippFr

 

this error is common with inappropriate mass scaling, that is when you impose a time step which is too high. Check the mass error due to mass scaling in the engine .out file: in your model the mass scaling increases the system's mass by more than 100 times! It is suggested to keep the overall mass increase below 2% and even then it has to be checked if the mass is added to parts that are moving, which would increase the kinetic energy and therefore decrease the simulation accuracy. A short video on energy and timestep error

https://altair-2.wistia.com/medias/osd349gz4k

 



 

Alternatively, you could try with advanced mass scaling (AMS) which does not add mass.

 

You can find more information from Introduction to Explicit Analysis using RADIOSS – A Study Guide in Time Step Control chapter. Also recommended is 2017 Radioss user guide starting from page 30.

 

However, the model you presented is not suited for explicit simulation as the minimum natural timestep due to CFL condition is 1e-11, which is practically unsolvable with the current computational capabilities. Rethink your modeling approach (beam instead of solid) or solve the problem with implicit. 

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