How to apply pressure to a Radioss Model

Altair Forum User

I try to create a /PLOAD entry for Radioss, that will define a constant pressure on the outside of a cylinder. Therefore I use the Radioss BCs Manager from the utility menu, where I find the option 'Surface type' to which I can apply a pressure. What is the type of data that is needed here and how can I apply pressure for a Radioss simulation?

 

In addition I would like to know whether to use Radioss or OptiStruct simulation for my type of task: I want to simulate a contact between a shaft - hub - joint connection. Both parts are initially in contact which they might loose upon increasing the rotation velocity. Would Radioss Implicit or OptiStruct Implicit NLGEOM be a correct way to approach this task?

 

thank you

 

 

Altair Forum User

Hello,

 

to apply the Radioss pressure, you need to have a '/SURF/' definition for this solver. There are multiple ways to define a /SURF for Radioss (which is not to mixed with a geometry surface definition --> /SURF is a Radioss solver keyword). One would be to define a 'contactsurf' entity in HyperMesh and apply the correct card image + correct elements. The following video shows how it works:

http://screencast.com/t/nmwXkyH0sp1a

 

For your second question: This is a bit tricky to answer. If you want to simulate the 'quasi static' behaviour of the moment when the contact between shaft and hub is lost, I would recommend OptiStruct, either as 'non-linear quasi static' or as 'non-linear quasi static plus lgdisp option'. This lgdisp will replace the 'NLGEOM' solver (which is in fact a Radioss solver running in the background). You need to have HyperWorks 13 with the latest solver patches installed to use lgdisp. HOwever, lgdisp is only needed, if the displacements are very high. If they are not, non-linear quasi static without lgdisp will do the job. See the help manual --> OptiStruct --> User's Guide > Structural Analysis > Nonlinear Analysis to see the differences between the solutions. Summarized they are:

1) non-linear quasi static = only contact, no large displacement

2) non-linear quasi static + lgdisp = contact plus large displacements occur

3) NLGEOM = contact plus large displacement (pre HW 13) - Radioss is running in the background. You might still need this option e.g. when having shell instead of solid elements in v13

 

So there isn't really a need to directly set up Radioss implicit for your analysis. However if you are interested in a time-dependent analysis of the few milliseconds when the parts loose contact, you can simulate with Radioss EXPLICIT to see about this dynamic (time - dependent) behaviour. This might give you more insight into what is happening at the critical rotation verlocity.

 

Regards

 Jan