ROPS -rollover protection systems

[chicagobob]

Anyone have any info on modeling the ground contact event in FEA or any info on surface contact perameters, e.g., concrete?

 

[GregLocock]

Could you explain what you are trying to do? Model the vehicle structure as it hits concrete or what?

You could probably get an idea with a coefficient of friction (steel on concrete) of 0.3, and a surface compliance of (WAG) 5000 N/mm




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[chicagobob]

thanks- modeling ground contact to figure out structural requirements -does adams do this or do I need lsdyno (?)

 

[GregLocock]

Ooh, nasty. (but fun)

Is this a roll over hoop, in which case you could probably get away with a simple beam element model in ADAMS? or is it the seat back pop up headrests, in which case I'd suggest a flex model in ADAMS, or LS DYNA. As you know, the crash guys use the latter.


I've never done any serious impact stuff, that's interesting. Have you got any test data to look at or are you flying blind?



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[chicagobob]

Heavy truck problem-class 8 semi's No data at all that's the problem. Probably go with external tublar steel 4130 or better, ~ 100k tensile. This " surface compliance of (WAG) 5000 N/mm " is not quite clear. Is this penetration resistence. What kind of indentor? Is the material presumed to fail if you get beyond this -what's the resistance past this failure point?

Thanks

 

[GregLocock]

Sounds like you are interestetd in different things than I was thinking of.

No, WAG=wild ass guess for the stiffness, which I don't think will affect your result on second thoughts. I don't think good quality concrete will fail in your scenario.

ADAMS will give you a good idea of the impact laods in your bar, but you should feed those loads into a proper FE program if you are interested in the structural stresses, or you can do the whole job in one hit (hoho) in LS DYNA.




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[vpg101]

LS-DYNA is the code for this type of impact event. ADAMS Flex won't get you very close, since this is a pretty nonlinear event.

 

[bcochran]

chicagobob,

SAE has standards you need to adhere to. The standards are for physical testing.

http://www.sae.org/servlets/product?PROD_TYP=STD&PARENT_BPA_CD=GV&TECH_CD=PROTS

best of luck,

buddy

 

[chicagobob]

thanks all

RCE