Mass + Velocity Loads & Dynamic Response

[Anonymous]

Hello,

I was wondering whether anybody knew if Robot was capable of modelling collision type loads?  I have trawled through the help files and cannot find anythign that helps me wiht my specific problem.

Essentially I wish to apply a mass with a specific initial velocity to a beam/plate and get values for deflection, moment, reactions etc as various time steps similar to a time history analysis for an initial force (but effectively working backwards to discover a similar static force would be from this loading).

If anyone has any information on whether Robot is able to perform this type of analysis and if so how we would go about setting this up I would be very grateful.

Kind Regards,

Richard 

[Anonymous]

You can add masses with acceleration for the loads definition toolbar.  It's on the tab with "self weight and mass"

You could then potentially use this in conjunction with a time history. 

Tony

[Pawel.Pulak · Accepted solution]

Attached the simple model I made some time ago (long time ago:)).

It is modeling impact of some weight falling from specified height.

It is done using linear time history (no plactic effects etc.)

Some simplifying assumptions are made concerning constant force during the impact but they do not influence significantly the results because the response is resulting from the change of momentum corresponding to integral of force in time domain (details in attached file).

More advanced models of impact (separating of objects after impact, forces during impact resulting also from elastic properties of objects) can be also created using for instance compatible nodes with gaps and elastic properties.  In such case time history analysis should be used too.

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Regards,

[Anonymous]

Hi, Pawel. I tried to simulate a similar problem and found your answer is very helpful. I also downloaded your model, and I can understand these assumptions and theoretical parts. However, I still do not know how to define these settings in Robot as I cannot see the detailed settings in your model as well. Could you tell me the process of defining the relavant parameters?

Thank you so much.

[Artur.Kosakowski]

After opening the Analysis Type dialog double click on modal or time history case to access their parameters. Being in the time history case parameters press the Function definition button to see the function itself.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

Thank you. Artur. I've found it out by trying clicking everywhere. 😊

Sent from my iPhone