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Help with mass error and energy error

Altair Forum User

Thank you George for the reply. So for any analysis until we use the control card for Implicit, will it always run an explicit analysis?? Also I have one more question, what is the error and mass error here ?

CYCLE TIME TIME-STEP ELEMENT ERROR I-ENERGY K-ENERGY T K-ENERGY R EXT-WORK MAS.ERR

3500 0.3713E-02 0.1048E-05 SHELL 106239 0.1% 0.1060E+07 0.7229E+08 0.1347E+05 -0.2986E+06 0.000

Is it the error, the error of the external force to the internal force?

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gopal_rathore

Hi Datta,

This is the energy error % value. Its physical meaning is to understand whether there is energy dissipation (-ve energy error) or it is increasing in the system (+ve energy error).

I have attached a snapshot for the same , refer it for more details.

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi Datta,

Unless implicit cards are provided, RADIOSS implicit will not be activated.

In the .out file there will be energy error and mass error. User can analyse these parameters:

The Energy Error computed by RADIOSS is a percentage and If the error is negative, it means that some energy has been dissipated. If the error is positive, there is an energy creation. If the positive energy error is high, the source of this energy has to be identified. Incompatible kinematic conditions can lead to such a situation. Normally, the energy error must be negative and decreasing (except for the first cycle ). The error must be less than 15% at the end of computation (5% for a good model). If the error increases a little, then decreases may be normal. If the error increases, this means that a problem has occurred. Then, the error may grow to 99.9% with computation failure message.

When the model is imposed with a time step (/DT/NODA/CST) mass error is monitored. In order to maintain the imposed time step, the solver will add mass to the model and this will be shown as mass error. For a perfectly imposed time step, the mass error should be less than 2-3 percent. Please refer this video which explains about time step and monitoring the .out file: https://altair-2.wistia.com/medias/o0bfml9ah5