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Showing resultant stresses on a volume element

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Mairi
#1
Nov26-12, 05:35 AM
P: 5
Me again, (this is what happens when you make a designer do mechanics, and give her a lecturer she doesn't understand :P ).

I'm stuck on a combined loadings question. This is the question:

"The 60 mm diameter rod (fixed at end C on the wall) is subjected to the loads shown.
1) Transform all the loads (forces and moments) to the centre of section A-B, determine the values, and draw them on a graph clearly showing the directions of coordinate axes and all loads
2) Calculate the normal stresses at point A, caused by the normal force, by the bending moments, and by the combined loading respectively
3) Calculate the shear stresses at point A, caused by the shear forces, by the torsional moment, and by the combined loading respectively
4) Show the final resultant stresses at point A on a volume element
"

I can do all the normal/shear stress sections, I've just got no idea how to show the resultant stresses on a volume element!

I've got normal stress at A as being 9.71MPa, shear stresses ([itex]\tau[/itex]zx) at A as 2.15MPa. I'm not sure how to split this up into σx, σy and itex]\tau[/itex]xy, which is how I'm used to seeing elements.

Any help with how I go about this would be greatly appreciated!
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SteamKing
#2
Nov26-12, 09:26 AM
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PF Gold
P: 6,729
If you attach a diagram showing the loading of the beam, you may get some feedback.
Vadar2012
#3
Nov26-12, 10:52 PM
P: 208
Yeah, a diagram always helps. You pretty much answered your own question though. You have NORMAL stresses and SHEAR stresses. Look up the definition of these and the direction they act accroding to the coordinate sytem you are using in the problem.


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