Mass. Discrete Rigid Body. 2

[supernest]

Hello all,

I have a problem when I am trying to define de mass of a discrete
rigid body.
I know that is necesary to define a reference node for each rigid
body.

after that, What I must make to end up defining the mass of the
rigid solid.

I calculate for different values from the mass and in all the cases I obtain the
same one reaction vs displacement curve when rigid solid hits the thin sheet in punching simulation, and I know that this is not possible since to greater mass of the rigid solid, they would have greater damages on the plate.

somebody could say to me that I am making bad?


Thanks.

 

[IceBreakerSours]

You are going to have to explain the model (analysis, element type, how are you measuring reaction, etc.)

Are you new to this forum? If so, please read these FAQ:

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http://www.eng-tips.com/faqs.cfm?fid=1083

 

[supernest]

It is a dynamic analysis of a punch impacting with a plate and is resolved with the explicit solver Abaqus.
The mesh elements are C3D8R.

The outer faces of the plate are fully restrained, and I measure reaction in the Y direction, the axis perpendicular to the plate.

With reaction data, and the displacement of the rigid punch, I generate the force-displacement curve.

Thanks,

 

[supernest]

Please, help!

 

[bkal]

You need to clarify what are you doing and how are you modelling it. How is a movement of your punch / rigid mass defined, have you given it initial velocity or are you "driving" it in a prescribed way. You are stating that the force displacement cuvre is a function of your "missile" and not your "target" - is that correct?

 

[supernest]

bkal hello , thanks for your reply .

well, I 'm doing a punching simulation, launched my projectile with a inicial speed (predefined fields ) , and then the projectile hits the plate .

Force is the reaction due to the restriction of the lateral faces in the perpendicular direction. Imagine a cylinder with a small thickness and a large diameter , which has the circular sides restricted completely , so the reaction in the direction perpendicular to the flat face of the cylinder is the force of my curve. And the displacement is the displacement of the projectile to impact with the plate .

I hope you can understand me now.

Greetings.

 

[bkal]

Am I correct in assuming that you have followed a procedure given in the section 33.3 of the manual (V6.11)?

Can you compare kinetic energies between the models with different rigid body masses?

 

[supernest]

Hello again , bkal , thanks for your reply

I have the Abaqus 6.10, but suppose that the manual will be the same . I read section 33.3 in the manual, and it teaches as you should apply loads. But I don't apply loads in my model, it is a rigid solid, which I apply an initial velocity in the section of Predefined Fields. Once I run the program , the rigid solid, or proyectil, is moved to the rated speed and penetrates the plate.

Regarding your cuestion about comparing kinetic energies between models with different masses , I have little experience with the program , so I still have some troubles to find several things. In the results section, I can create a XY Data and then, in ODB history output, I have the option to plot the kinetic energy of the entire model. I am not sure if this is what you refire , but I did it for two different mass models , and results varied in the graphs obtained .

Different masses affect the graph of kinetic energy. However, when I graph the force - displacement curve with different masses , the curves are almost equal, and it doesn't matter that I assign so different masses.

Regards, and many thanks for the help.

 

[bkal]

It is difficult to say without more detail, but is it possible that your force - displacement curve is only a function of the target properties (so is independent of the mass of the punch), but that a total final deformation is a function of the mass of the punch.