Hi all,
i am doing dynamic impact analysis on a civil structure. And the impact load is a moving load with a certain magnitude of velocity. And i have to analyse the effect of impacting body in the last step of analysis after gravity load analysis. For this i have to disable dynamic impact load effect on initial and first step, and enable in last step.
Velocity using predefined field is like defining initial velocity. An object with initial velocity, if impacted to other object, may loose energy to other object. But, total energy in the system will remain constant at any given time.
If the velocity is defined using BC (like imposed velocity), the object has to maintain that velocity throughout the simulation. If there is any obstruction, still the object continues to move with the defined velocity. Total energy of the system may increase with time, depending upon the energy transferred to other object or internal energy etc.
Regards,
Chandrashekhar
Hi Chandrashekhar,
First of all, thanks for response. If i provide velocity using predefined filed, i cannot assign on specific analysis step. For my analysis, i need to inactive the moving part for my first step of analysis for the gravity load analysis only. If i going through boundary conditions then only i can make velocity active for specific step of analysis. And i am providing mass of moving body using inertai/ mass option. That means i cannot specify effect of mass of moving vehicle for a final step of analysis. Can you please give certain ideas for this case, if you are aware of this kind of analysis.
I hope that it works:
- use the initial conditions to give the moving part the velocity
- deactivate/remove the elements of the moving part in the first step
- activate the elements of the moving part in the second step
These changes can be done in the step definition:
*MODEL CHANGE, REMOVE/ACTIVATE
ELSET_MOVE
Element and contact pair removal/reactivation:
•can be used to simulate removal of part of the model, either temporarily or for the remainder of the analysis;
•allows reactivation of elements strain-free or with strain;
•can be used to save computational time when a contact pair is not needed;
•can be used only in general analysis steps; and
•can be used in a restart analysis only if it was used or activated in the original analysis.
But i am doing dynamic/ explicit analysis for my research work. And this method only work for a general analysis. steps.
Ok, I have used this method in an implicit dynamic analysis. There it worked well. Then maybe the following procedure (?):
- Solve in the first step the static problem for the whole model (gravity load analysis). Place the impact body far away from the other part.
- In the second step the impact body is accelerated to the required velocity. After reaching the velocity, the acceleration must be zero. The impact body should be stress-free before the impact.
I hope it's understandable. Maybe someone has a better idea?
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