understanding stressing components in abaqus

[MohdAc1412]

Hello,
I'm trying to find out the tension transmission along a rod or bar, if I model a bar spanning in the x direction, fixed from one end and point loads are applied on all corners on the other end in the x direction, then I create a path running on the surface of the bar and plot S11 (stress in x direction), I get the right value of the stress, if for example I apply 4 N and the cross section is 4 mm2 , I get a stress plotted equal to 1 N/mm2, and by multiplying that stress with the area I get the force transmitted along the bar... But my problem is when the forces are acting in the y direction, and I try to find S11, I get different values depending on where I create the path, if it is on the upper surface I get a very high stress, and I find the opposite of this stress in the bottom surface, even when I try to create the path in the middle of the bar, I don't get reasonable plots...
what is the best way to find the tension stress transmission along the bar?
Thank you

 

[IceBreakerSours]

If there are more than four nodes on the loading side of the bar, then make sure all nodes are being used to load the bar. You may use equation to simply load one of the nodes (while constraining the rest to move as the loading node is moving). Then, use the reaction force variable (RF) and displacement (U) variables from the loading node to get your load vs. displacement plot. You could, then, divide the load with the initial cross-sectional area and the displacement with the initial length to get your stress and strain values.

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[MohdAc1412]

IceBreaker, thanks a lot for your reply,if you could just bear with me and explain a bit more on how to do the procedure you explained I will be grateful, I'm not very sure of what you meant by finding the reaction variable and loading all nodes... please correct me if I'm wrong...
So what you mean by loading all the nodes is that the bar has four corners (nodes) on the loading side, I will just apply 1 N in the y direction on each node, right?
then I will create a path a long any side or edge and plot the displacement in the x direction, and plot the reaction in the x direction along the same path... I don't understand how this can help in finding the tension force transmitted in the x direction? because it will just give the same S11 value that doesn't make sense, right?
I'm not sure but I think the main problem being where I create the path

thanks

 

[bkal]

Am I right in understanding that in your first case (when you get expected results) you are applying the axial load (load in the direction of your rod), while in the second case you are applying the load which bends the rod? (i.e. the load is applied in the direction perpendiculr to the line of the rod).

 

[rb1957]

X forces are axial, Y forces cause bending ... you should see tension on one side of the beam and compression on the other.


Quando Omni Flunkus Moritati

 

[MohdAc1412]

yes, x forces are axial... but what is confusing me is that I'm trying to model the pulling out mechanism of a thread from between fabrics... so what the model is actually like is two plates with a curved entry surrounding a thread (attached picture will show the model), I've been trying for a long time now, the last thing I did was that I modeled the plates as solid, the thread as a wire, in 3d, and the the thread is embedded inbetween the two plates, and the plates are fixed on all directions, so actually the job of the plates is just to constrain the deformation of the wire, and will make the wire follow the shape of the curve if there is contact ... the thread has a fatigued segment where there is a drop in the modulus of elasticity, I partitioned that segment and applied a different material property... by applying a vertical force, and since the modulus of elasticity in general is low, and there is a fatigue, the deformation will be significant and tension will develop along the thread... trying to figure out the profile of that axial force is very confusing as I'm not getting the right stresses if I use S11 (stress in the direction that's the thread is spanning)...

 

[MohdAc1412]

i tried to output SF (section forces and moments), but as you might already know, this output can't be used for solid parts... it seems the only way to avoid this problem is by modelling the wire in 2D... but then I won't be able to model the plates