help with non linear materials, acceleration vs time loading, and more block tutorials in general.

Altair Forum User

1)Hi, first I want to thank all the support forum moderators for helping us with our questions and models  . And I am also grateful for all tutorials available online which have been really helpful.
2)I have recently started to use and learn Radioss Block data. I saw the getting started with radioss bulk videos on this forum ( car crash). I tried the cell phone drop test tutorial. I wonder if there are any more tutorials available to get the basics of radioss bulk. And any way to get more practice using radioss bulk ( e.g, partially completed hm files like we have for hypermesh tutorials)
3) I would like to know how to use acceleration vs time curve (which we can get from experiments like impact/drop etc ) as load in the FEA.
4) I think I am getting how to use some non-linear materials like M36_plas_tab using stress strain curves. But I would like to know more e.g, about hyperelastic materials/ foam materials.

Thanks!

Altair Forum User

Hi Arbhaval,

thank you for your compliments. my best suggestion would be go through the online help (users guide, theory manual etc.. under RADIOSS Block), there are lots of examples for implicit and explicit analysis available with a very good explanation of cards (material, property etc..) and also tutorials. This shall help you to understand different types of contacts, materials, how to use curve data etc..

http://www.altairhyperworks.com/hwhelp/Altair/hw12.0/help/altair_help/altair_help.aspx

Altair Forum User

Arbhaval,

I presume you are only interested in RADIOSS block, is that right?

Hereon RADIOSS bulk data is part of and called Optistruct, RADIOSS only represents RADIOSS block.

By tutorials in this forum do you mean the training center?

Have you gone through the videos in this post?

http://www.altairuniversity.com/support-forum/?mingleforumaction=editpost&id=2113&t=385.0

The list of examples in the help documentation is a good place to start
Altair RADIOSS > RADIOSS Tutorials and Examples > Examples: List of Examples
These use model files that are ready for analysis already and part of the HW installation, just go to the demo folder in the installation directory and you will find these files.

The tutorials in the help documentation is also a good place to start
Altair RADIOSS > RADIOSS Tutorials and Examples > Tutorials > Large Displacement Finite Element Analysis > HyperMesh

Altair Forum User

In examples, example 18 deals with force Vs time please refer to that. Also please refer to examples where you see imposed velocities, imposed displacements, imposed acceleration (time dependent).

this gives you good idea on time functions, curves  

Altair Forum User

arbhaval,

Use the step 7 of Altair RADIOSS > RADIOSS Tutorials and Examples > Tutorials > Large Displacement Finite Element Analysis > HyperMesh: RD-3500: Tensile Test Setup using HyperMesh as a guide to create imposed accelerations
with the difference being that you need to Use the BC manager and pick imposed acceleration for the type. The general procedure after that is
Under direction pick X, Y or Z for direction of the acceleration.
The scale X and scale Y are scale factors for the curve you define under Curve ID. So the scale X is a mulitplier for the abscissa of the input curve. and scale Y is a multiplier of the ordinate of the input curve.
Let us know if there are any concerns when you apply this boundary condition.

Altair Forum User

Thanks. I tried a similar model as that of my bulk data one. I have done material non linearity, general contacts and force vs time load. I am not sure about what errors I might have made. Can you please take a look and give me some suggestions? Thanks!

I tried to follow the getting started with radioss block data video wherever possible.

Also why do we get this error : '** ERROR TRAPPED' ?

Altair Forum User

Arbhaval,

update the elements in RADIOSS block. go to 3D page > Elem types > select all the elements and click update.

check for intial penetration. If there are no penetrations, card edit the interface card and change Inact to 6

also, edit the component and change the card image to PART

Altair Forum User

Many thanks Prakash! The file works. I can see the results in hypermesh now. Very exciting. This is my first radioss block model!
Now I want to try applying pressure instead of conc force. I tried to create face elements then surf from FE and then moved this surf to new component. But I cannot select this surf in BC manager to apply my pressure. Any suggestion?
Thanks a lot..!

Altair Forum User

surface sets are a group of nodes/elements which represent a surface.

please try this: create a element set and after that create a surf set with SURF as card image and select the element set created.

Now you can use the newly created surf set to apply pressure load.

Altair Forum User

Method I
1) create a element set/ node set
2) use the same set to create a surface set with surf as card image and select the created element/node set
3) when applying pressure select the surface set created in step 2 to apply pressure.

method II (simple method)
1) create a contact surface with nodes and surf seg as card image
2) use the same as surface set to apply pressure un BC manager

see example 47 and 44 for more on appying pressure load.

Altair Forum User

I tried both ways but they did not work for me.
But now I have moved on to impacting the model by a rigid plate from top which is moving at 9 m/s. I have created a model but it requires very small time step and takes too long to run. Can you please offer some suggestions.. I have attached the hm file.
I am sorry to keep bothering you but my university doesn't have anyone who knows hyperworks well enough.
Thanks

Altair Forum User

You can make the impactor as a rigid by card editing the component.

also, when creating RBEs' make sure the independent node is not a part of the impactor. create a node a little offset to the impactor and connect to the elements.

In type 7 change the Istf to 4, this way solver will calculate the stiffness of the contact interfaces.

Altair Forum User

thanks..
I just know the initial velocity of the impact and don't really know how to set the engine file...
do you mean use the rbody/admas in the card edit to make the impactor as rigid?
Can you explain the second statement in your comment please?
I am translating the indep node and applying the ini vel to it..
Can I just create a rigid wall with initial velocity instead of using the impactor?

Altair Forum User

Hi,

Sorry for a late reply, yes, card edit the component and make it to rigid and check.

the independent rigid node shouldn't be shared by any other component. In which case translate the node and try applying load on it (in your case velocity)

yes, you can create a rigid wall and apply velocity to the rigid wall.

go to Analysis page-->Rigid walls--> create a rigid wall and after that you can add a motion in the same panel.