Hand calculations

[rideway]

thread727-296596

Hello everyone

Im a mechanical engineer and I have two-years FEA experience. I was talking the other day with a friend of mine about hand calculations in order to make sure that the FEA results agree with what the classical theory says.

But normally for my analysis I just need to do equilibrium checks and only once I calculated a beamed structure which I could model as a free body diagram so I could check the results.

I would like to know, for static analysis, which hand calculations do you perform on a daily basis in your calculations?

BR

 

[inline6]

basic buckling of thin panels classical solutions against non linear or buckling analysis. Also general P/A +/- M/Z for nominal stresses in members etc.

 

[rb1957]

personally i wouldn't do equilibrium cheacks. normally i have load and reaction sets and my constraints react rigid body motion; but i still check that these are small. normally i'll take loads from the model and determine stress by hand. often i'll start my model in a very simple state, so i can check it by hand (hoop stress in a fuselage).

 

[Twoballcane]

I typically start an analysis with a free body diagrams just so I can visualize and make sure all loads are accounted (sum of all forces and moments in each axis is equal to zero). From there, I can calculate out the moments for bending stress that will eventually be used in calculating the principle stress. Then build the FEA model and apply constrains and loads (static) and see if the numbers match up. However, I have failed to make it a habit to check the reaction loads at each constrained point to make sure the gravity direction and value, and density are correct first. I usually check the reactions loads when the FEA data is way off my hand calcs and for some reason it is always the last thing I check after an hour or two banging my head against the white board recalculating my had calcs. In a dynamic case, calculate out the max G load and then multiply the mass by it to get new stress levels.

Tobalcane
"If you avoid failure, you also avoid success."
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