Total Energy Decreasing During the Dynamic Front Crash Analysis of Chassis

Altair Community Member

Feb 16, 2022

Updated Feb 22, 2022 by AshwaniMittal

Hello everyone,

I am performing the dynamic front crash analysis of the chassis of a vehicle in Radioss. During the post-processing of the results obtained, I have plotted the total energy, kinetic energy, and internal energy graph. Theoretically, the total energy of the system should remain constant during the whole analysis but contrary to that it remains constant initially for some time but then starts decreasing gradually. For your information, I have used the M2_PLAS_JOHN_ZERIL as the material card image. (Please refer to the image attached for the material parameters used)

Does anyone know the reason behind it and how to correct it? Any help would be appreciated. (I have attached the image of the respective energy graphs with stress plots for reference)

Thanks in Advance

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Adriano_Koga

Altair Employee

Feb 16, 2022

Updated Feb 16, 2022 by Adriano_Koga

i'm not an expert in expliocit, but what anout Hourglass energy?

How much of hourglass do you have?

Sometimes the hourglass energy rises, which is not desired. I believe the Altair ebook about Radioss explicit analysis covers hourglass effects.

Varun Venkateswaran

Altair Employee

Feb 16, 2022

Updated Feb 16, 2022 by Varun Venkateswaran

This might be due to hourglassing. If I remember correctly, Radioss has other energy output that will includes this also and that should remain constant.

AshwaniMittal

Altair Community Member

Feb 16, 2022

Updated Feb 16, 2022 by AshwaniMittal

Hello @Adriano A. Koga and @Varun Venkateswaran,

Thanks for your replies. For your information, the hourglass energy remains constant for the whole time during the analysis. You can refer to the image below.

Thank You

Ingeniorator

New Altair Community Member

Feb 17, 2022

Updated Feb 17, 2022 by Ingeniorator

Is friction activated on the rigid wall? Plot the external work as well.

PaulAltair

Altair Employee

Feb 22, 2022

Updated Feb 22, 2022 by PaulAltair

Yes, you should compare to TTE (total translational energy) rather than just TE, TE does not include RKE (rotational kinetic energy), CE (contact energy) or HE (Hourglass, but your HE is likely 0 here because you are using QEPH elements?)

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Total Energy Decreasing During the Dynamic Front Crash Analysis of Chassis

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