But, you are right this rule is coming from fatigue analysis. > I know that four other companies are using Neuber's rule to correct the linear FEA stresses.
So, nonlinear analysis is computationally 50 times more expensive. I prefer the Linear FEA + Neuber's rule versus Nonlinear FEA, because linear model with 848,664 DOFs runs in 29 minutes, but the same model with nonlinear material runs in 1444 minutes. By using Neuber's elastic stress correction, I found 73.9 ksi. For the same mesh and load, Linear Solver found the peak Von Mises Stress a 119 ksi and Nonlinear solver results to 70 ksi. > I apply this rule to a static analysis to avoid nonlinear analysis. RE: Margin of Safety for Ultimate Loads with FEM rb1957 (Aerospace) 28 Sep 10 18:02įollowing are responses to your questions: Before you start your FEM or get anything useful out of it, I would think you should better understand that.
Calculate margin of safety how to#
But those are generally high strength steels, which have very different static and fatigue behavior than would a "typical" aluminum.Ĭould you better define the material, failure model, fatigue approach? By asking whether or not use max principal or von mises, indicates to me that you are not sure about which failure model to use (and how to apply it properly). What SW mentions about landing gear is true as well, at least for typical aerostructure landing gear that we are used to.
If it is ductile, but the elongation limit will be reached within then ultimate load, then you could apply something like a plastic factor (i.e. For example, the ultimate tension strength of plate with a hole is close to that of Ftu*(net section). If it is ductile, how large of a region is in the high Kt area? If it is relatively small, you might generally neglect the Kt completely. Do you have a reference to using Neuber's rule for a static analysis? I suppose it could be done, but it seems like you are mixing concepts? If it is "brittle", then you might directly use the Kt. I suppose I could see some correlation to a static analysis, but I have never seen that used. Why are you using Neuber's rule? That has been developed for fatigue analysis.
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