# External Forces Work

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HI All,

I am running a crash analysis.

I have no external force applied to my model except initial velocity and gravity.

the model is set to impact on a rigidwall

Will the External Forces Work remains constant or increase or decrease??

Regards,

SUBHU

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The External Work Forces is Decreasing. Is this Good??

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Hi Subhu,

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 by done 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.

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Hi,

Please let me know below mentioned energy relations are correct or not.

External work = Internal energy+kinetic energy+contact energy+hourglass energy

Total energy = Internal energy + kinetic energy

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32 minutes ago, jsk459 said:

Hi,

Please let me know below mentioned energy relations are correct or not.

External work = Internal energy+kinetic energy+contact energy+hourglass energy

Total energy = Internal energy + kinetic energy

@jsk459 Yes the above relation is correct.

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Quote

External work = Internal energy+kinetic energy+contact energy+hourglass energy

This is NOT correct.

External Work includes the work from Imposed movement (displacement, velocity or acceleration), force (/CLOAD or /GRAV), and pressure.  It also include the frictional energy from a /RWALL (when FRIC!=0.0)

If there are only an initial velocity, gravity and a rigid wall in the model then I would assume the high negative external work is caused by the friction on the rigid wall and maybe gravity.  It is difficult to say without seeing the model.

Thank,

Andy

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