1.15 Fitting Factor
1.15 Fitting Factor
(OP)
Can someone summarize in laymans terms the application of 1.15 "fitting factor" in aircraft joint analysis?
Thanks!
Thanks!
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RE: 1.15 Fitting Factor
Use the factor when you don't have allowables based on a test program (and subsequent statistical reduction) or derived from industry standard methods and allowables (such as rivets in sheet metal per MMPDS).
Its basically a requirement for an "extra" ~13% of margin for non-standard or untested installations.
RE: 1.15 Fitting Factor
RE: 1.15 Fitting Factor
"Many uncertainties exist concerning the stress distribution in fittings. Manufacturing tolerances are such that bolts never fit the holes perfectly, and small variations in dimentions may affect the stress distribution. An additional margin of safety of 15 percent for military airplanes and 20 percent for civil airplanes is used in the design of fittings".
Hope that helps.
RE: 1.15 Fitting Factor
RE: 1.15 Fitting Factor
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Nert
RE: 1.15 Fitting Factor
RE: 1.15 Fitting Factor
Now compare that to the case of a machined or cast "fitting", where you are determining the allowable load via a stress anlysis based on material properties and joint geometry. This allowable load DOES represent the load at which you would predict failure of the part. In this case, there is no built in safety factor. (I wouldn't consider material properties as having a built in factor of safety for stress analysis since they represent minimums for material cert - though if I were to place a wager on a failure load I might). So in these types of cases, I would apply the fitting factor.
I would apply the same general principals to most joints, especially critical ones, whether or not they meet a given definition of "fitting".