Femap with Nei Nastran rivet forces 1

[trainguy]

Hi all.

Can you aerospace types (or others) remind me how you typically extract shear flows for sizing skin to frame member connections? I have not modeled discrete fasteners, but just used glued contact in my FEA. What is the usual method with "older" FE approaches, i.e. merged shell elements, etc?

tg

 

[rb1957]

I'd work off element shears

another day in paradise, or is paradise one day closer ?

 

[trainguy]

rb:

I have done the same many times - however, do you take the total shear over all the elements in a line and divide by total length (giving average shear flow) or is there another approach?

tg

 

[rb1957]

you need to be careful using shears ... are they all aligned the same ? is it a straight forward connection (like the change in endload of strgr) or (more likely) a situation where shears are moving between several different members ?

but summing different element contributions is reasonable for ultimate static design, or you might consider the peak load applied to a representative number of fasteners.

another day in paradise, or is paradise one day closer ?

 

[trainguy]

rb,

Is there a standard or guide that helps define "representative number of fasteners"?

tg

 

[rb1957]

any sizeable point load would be introduced via a fitting.

if you've got a lot of skin panel shear, and are splicing the skin panel, how many rivets would fit within the element ?

you could average over like a frame pitch.

if there's one shear spike, does it look reasonable to smear over three rivets ?

another day in paradise, or is paradise one day closer ?