Displacement

[dwarf12]

Hallo,

I have created a sphere (3-D deform solid) 5mm above a steel block (3-D deform solid). I want to set the sphere onto the block (5mm down) and then add a force to the sphere.
For the force I used 'body force'. Works very well. The problem is the displacement at the beginning. The program says i have to define an amplitude - displacement can't be instantaneous.I've choosen tabular as amplitude. But I don't know which input parameters (time/frequnecy , amplitude) i have to choose.

Thank you!

 

[rstupplebeen]

I this a Standard (quasi-static) simulation? If so why not do the translation in the assembly before analysis? If you do want to have the translation in the analysis then have the table be:
0,0
1,1
Or simply choose linear ramp. I hope this helps.

Rob Stupplebeen

 

[Nileo2005]

It seems like you want to move the sphere down in the assembly module before the analysis starts.
If you go the route of an amplitude, you need to apply the movement of the sphere in a boundary condition to apply the amplitude to, making sure not to square your movement with the displacement and the amplitude multiplier, and then turning off the BC at the beginning of the second step. Quite laborious and a waste of computational power, but it is a second option that you could endeavor in leu of moving the part pre-analysis.

 

[dwarf12]

It's an explicit simulation...

@nileo2005: You are writing about 'second option'. What would be the first option. If I put the sphere onto the block in the 'part module' there are sometimes problems with the mesh. But sometimes it works.

But then there is another problem with the amplitude: As the sphere rebounces I want to displace the sphere horizontal to the block. I use a BC and want to give the sphere a certain displacement. Now i need an amplitude again. I don't know the paramters to get it to work as I want to.

Something different:
Is there a way to create a boundary condition which works like this.
Sphere impacts the surface
-> sphere rebounces
-> sphere has the distance x to the block
-> sphere accelerates down again

Thank you very much

 

[rstupplebeen]

Are you trying to model a bouncy ball? If so choose a drop height and hand calc the velocity at impact. Have that velocity as an initial condition for the ball. Also include a gravity load. Now drop it and watch it bounce.

If you really must see the initial drop then choose your height apply gravity and drop.

I hope this helps.

Rob Stupplebeen

 

[dwarf12]

Thanks for your answers.

It's a repeated bouncing of a ball with a definite velocity. After the ball has rebounced it has to be put away from the impact with a definite distance. The calc. is explicit. that's why i have a problem with the displacement /amplitude