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CBUSH Rotational stiffness calculation

CBUSH Rotational stiffness calculation

CBUSH Rotational stiffness calculation

(OP)
Does anyone have any reference(s) to calculate the rotational stiffness for CBUSH in  FEM to account for the moments due to the heel-to-toe effect for a L-angle?

RE: CBUSH Rotational stiffness calculation

Sych, we have been doing some work on this recently.  Our customer (large aircraft firm beginning with letter A but they dont make buses), has a methodology requirement that simulates the heel/toe or prying effect of L flanges and angles.  We did some work from first principles to derive the appropriate in-line rotational stiffness of the CBUSH element.  Trouble is that the number you get out varies hugely depending up the assumptions.  I did a quick check of the suppliers we know well and the values of Rx stiffness varied by a factor of 10000 or more.  

So the approach we took was to use a more conventional CBUSH plus CGAP FEM approach and then match the shear and pull-thru forces along the flange using variable in Rx.  We found a value that matched pretty good, although it differed from other siuppliers assumptions.

I suggest you use a test FEM to make a comparison analysis and then use the value of Rx that gives best correlation.


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