'secondary bending'?
'secondary bending'?
(OP)
hello,
does anyone know something about "secondary bending" or "secondary tension load"?
for instance if you have a so called lap joint configuration with two splice plates fastened with 3 rivet rows and with a tension stress at the ends of the plates:

i'm asking myself how to calculate or at leat to estimate the resulting secondary bending moments in the plates around the rivets in order to calculate the bending stresses there...
because it is a non-linear problem i expect some differential equations but i hope that there is a more simplyfied and convenient way to estimate the moments and bending stresses, isn't it?
i hope anyone can help me, 'cause i couldn't find anything about it in my mechanics-books...
best regards
solari
does anyone know something about "secondary bending" or "secondary tension load"?
for instance if you have a so called lap joint configuration with two splice plates fastened with 3 rivet rows and with a tension stress at the ends of the plates:

i'm asking myself how to calculate or at leat to estimate the resulting secondary bending moments in the plates around the rivets in order to calculate the bending stresses there...
because it is a non-linear problem i expect some differential equations but i hope that there is a more simplyfied and convenient way to estimate the moments and bending stresses, isn't it?
i hope anyone can help me, 'cause i couldn't find anything about it in my mechanics-books...
best regards
solari





RE: 'secondary bending'?
As far as I know, back in the days when they did a lot riveting on steel, no one ever got into that much detail.
You'll notice for example, that you show a 2-dimensional version of what is a 3-dimensional problem. You omit the rivet heads, and likely omit the initial tension in the rivets. And quite often when there were three rows of rivets, they would be offset, not in line. My point is that if you solve your problem exactly, you still have a very appoximate solution to the actual physical situation.
If this is a cylindrical shell, check Timoshenko's Theory of Plates and Shells or other more modern references. Roark's Formulas for Stress and Strain also has formulas for bending of cylinders.
RE: 'secondary bending'?
If it is just a lap joint and not cylinderical as J. Stephen
also states then you wouldn't consider bending in the joint and it would be analysed purely on the basis of shearing the rivets, bearing failure of the parent metals connected with the rivet and tearout of the rivet through the edge of the connected parent metals.
regards
desertfox
RE: 'secondary bending'?
Roughly the moment will be Ft, which from M/I=sigma/y will cause stresses of the order of t/2*Ft/(1/12bt^3) whereas the axial tension will cause a stress of F/(bt)
so the fractional error is of the order of 6*t^2*F/(bt^3)/F*bt = 6*t^2*F/t^2/F, ie 6
hmm that is an awful lot!
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: 'secondary bending'?
RE: 'secondary bending'?
RE: 'secondary bending'?
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: 'secondary bending'?
RE: 'secondary bending'?
You will be doing a great favor by putting up the file on an ftp server and post the url here for the benefit of interested members of the forum.
Thanks a lot.
RE: 'secondary bending'?
first of all thank you all very much for your comprehensive answering!
and prost, i'm very much interested in your visual basic spreadsheet! it would be really nice if you put the file on your ftp server!
thank you very much in advance!
solari
RE: 'secondary bending'?
ftp://ftp.apesolutions.com/pub
I put a small picture there to show you some of the nomenclature.
If you don't mind paying $100 for a VB library of LINEAR1 and other numerical routines, then I have instructions for getting that code. But you won't need it, if you don't mind using the Excel matrix functions.
RE: 'secondary bending'?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: 'secondary bending'?
RE: 'secondary bending'?
RE: 'secondary bending'?
RE: 'secondary bending'?
RE: 'secondary bending'?
Oops...I'm remembering a certain fiber-reinforced composite material...not isotropic, homogeneous, beautiful metal!
Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
RE: 'secondary bending'?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: 'secondary bending'?
if you do a compliance model of load going into a doubler then the outer row carries more than 50% (65% is a reasonable) of the load transferred into the doubler, and the 2nd row carries the remaining load (35% in this case).
but you're right if you have a two splice joint, each row has to carry 50% by symmetry (same result if three rows, again by symmetry) assuming the thicknesses of both splice pieces is the same (if not then the joint isn't symmetrical).