Reaction Force at Time Zero

Altair Forum User

Dear All,

 

I have imposed time vs disp curve as a loading.

but getting reaction force value= 6.9 KN  at time =0 sec at first frame, 

and at second frame t=0.001sec value is showing 8N then after increase in next frames it is showing linear increase in reaction force from 8N to 1KN.

 

My question is, why the value of rection force is high at time =0

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Nachiket Kadu_22143

Hi 

Can you share H3D for it?

Altair Forum User

I cant because of confidentiality

Altair Forum User

@Ganesh Munge

 

Can you plot the same on HG?

Andy_20955

I believe this is caused by using the imposed displacement.  If you differentiate your imposed displacement curve you will get a non-zero velocity curve at T=0.    Thus RADIOSS has to apply a force to get that initial velocity.  You could try an imposed velocity and see if that gives you the zero force at t=0.  If not and you have contact then maybe the issue is initial penetrations.  

Usually the initial force caused by imposed displacements does not change the results later in the simulation as compared to using an imposed velocity.

Karthic_22061

Hi,

Try increasing the initial gap b/w the parts, also check for  penetrations.

Try slow load rate initially

Nachiket Kadu_22143

Hi @Ganesh Munge

I assume the same nature of kinetic energy as in your previous post. If that is the case u need to make kinetic energy as low as possible by gradual loading. 

Altair Forum User

thanks @Nachiket Kadu, it is sorted out with gradual loading.