eNERGY eRROR
I am conducting a rollover simulation.
After collision my energy is constantly rising
The loads in the model are gravity and initial angular velocity.
The tube material mostly used is contributing to the internal energy and overall total energy, Such that internal energy is exceeding total Energy
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the internal energy of material used for structure tube is most contributing to this .
The material Card used is MAT36 and Sliding with friction is used for ground.
Below is the graph for Kinetic energy and internal energy of tube material along with Global Kinetic and internal Energy
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Answers
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Hi,
Please search the forum to see other questions about energy error. Also plot your external work, contact energy, and Rotational kinetic energy. I believe the kinetic energy you are plotting is only translation so also check the rotational kinetic energy. Typically if you plot it should be constant since you don't have any external work.
Thanks,
Andy
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Hi,
the reason for total energy rising is due to the external work (Total Energy = Internal Energy + Kinetic energy + External Work). External work is any external loading applied in the simulation. This can include Imposed movement (displacement, velocity or acceleration), force (/CLOAD or /GRAV), and pressure to name a few. Work done by an external force on a system is always a transfer of energy to some other form of energy and this negative work represents the transfer of energy during the simulation and this is fine. The work being done by gravity is gradually increasing, which can be plotted in HG as External forces work.
A similar query was already posted:
https://community.altair.com/community?id=community_question&sys_id=25468c761b2bd0908017dc61ec4bcb63Check the following research papers on bus rollover, where energy balance graphs show total energy increasing.
https://advancedstructures.in/blogs/bus-rollover-simulation-analysis/
http://ijsetr.org/wp-content/uploads/2016/05/IJSETR-VOL-5-ISSUE-5-1815-1820.pdf
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Below is the graph for RKE , CE and Hourglass Energy , together these do not contribute much to the Total Energy
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The total Energy graph and total Trans Energy and Total rotational Energy are almost same.
below is the graph for Energies and External forces work.<?xml version="1.0" encoding="UTF-8"?>
The HTC paper itself mentions that Energy should remain constant and is more or less constant throughout Simulation.
Can total energy increase in such analysis when no energy is created ?
What can contribute to it? I think Energy should remain constant in such analysis.
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actually, also in the HTC paper the total energy does increase slightly at 50 and 325ms. Like mentioned before, additional external energy is due to gravity body loads. If gravity is turned off there will be no total energy increase.
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