Nonlinear transient impact analysis with contact

[automechanicar]

Hi,

How can I simulate an object impacting a another object at certain speed or just a drop test. Starting with a sphere which impacts a simply shaped object (like a cube) seems the easiest way to begin with, but I simply can't start off. I know that it should be modeled as a nonlinear time-dependant problem including contact, but I dont really know what type of boundary conditions, contact definition and solution method is to be used. I am using NX Nastran with Femap 9.2 as pre/post processor. Is there any tutorial which treats this type of problems?

Kind regrads!

 

[GBor]

A sphere impacting a cube is not a simple problem (Hertzian contact). I would recommend a cube onto a cube. Also, start with 2-D...it runs much faster and you can experiment with different settings. Apply body loads like gravity and only apply one at a time until you are comfortable working with the software. Set up limited contact so you can monitor it closely. Make sure that you are close to contact at one of the time steps (when applying gravity, make sure you have 4-10 time steps before the block would hit -- hand calc the time it would take using standard physics equations).

That's the way I started...

 

[automechanicar]

Hi Gbor,

The problem is that I dont know how to setup an impact analysis. Is there some kind of a tutorial example which adresses an impact problem? Or do you perhaps have an simple example that you may attach to one of your posts? This would be very helpful as I could explore an existing model so I would also be able to ask more relevant questions concering simluation of impact with Nastran.

Thanks ina dvance.

 

[GBor]

I don't use NX, so an example would be pretty useless. Not sure I could translate one in to Nastran format...and translating an impact analysis doesn't usually go too well anyway.

I'm sure there are others that can jump in and help you out.

 

[automechanicar]

OK, thanks anyway.

 

[wvillers]

automechanicar, you didn't mention which solver you were using... To really perform an impact such as a drop test, you'd want to use SOL601 or SOL701 in NX Nastran, do you have access to these modules? If not, you could perform a dynamic response, but you'd have to manipulate the data a bit (i.e. acceleration levels). You could treat it as a shock and perform an SRS type of analysis. Either way, this should be somewhat documented in the NX Nastran manuals...

 

[automechanicar]

Thanks for the info.

I am using the combined package FEMAP/NX Nastran. I think this the socalled basic solver which is not the explicit solver that is most appropirate for these types of problems. This basic implicit solver can handle nonlinearity, however only one a each time, being either material, geometrical or contact. I have also Abaqus Implicit and Explicit a my disposal so I will try to resolve this with Abaqus.