Not that familiar with this software yet so just been messing around comparing hand calcs to FEM results and have been getting weird reactions at where my bolt holding down this bracket should be (L bracket w/ hole):
My x direction reaction reaction makes sense of -30N, but I was thinking of getting a Z reaction of around -20N (depends if heel toe is accounted for) and am getting a reaction of basically 0. Probably have something wrong with my model/BCs but Im not sure.
For reference the hole is fully fixed.
Thanks
Shouldn’t the horizontal force at the top cause a moment making the bracket pivot about the bottom right corner? Then to stop this clockwise moment the bolt has a reaction in the -Z direction and another reaction (equal but now +Z direction) near the vertical leg to cancel the moment?
Can you include the axes in your screenshot to make it clear which direction is which ?
Is the boundary condition applied directly to the face of the hole ? Try applying it via rigid body constraint where you can read all the reactions easily and fix the rotational DOFs too.
Possibly fixed the issue… I think my boundary conditions were wrong. Ended up creating a reference point at the center of the hole edge and making a rigid body constraint attaching the hole surface to that reference point. This reference point was then fully fixed and another BC was applied to the bottom right corner edge in the Z direction (so the model isn’t trying to spin around the bolt hole about the Z axis).
Now I am getting a correct X reaction at the reference point of -30N (applied load was 30N in + X direction) and a Z reaction of around -25N which is much closer to hand calc.
The reaction forces only occur in the supports. So if you have only one support, the hole, the reaction force appears only in the hole. I assume you have a linear analysis, so the equilibrium of force components is Sum F_x = 0, Sum F_y = 0, and Sum F_z = 0. So if there is only load in the x direction, the only reaction component is x.
But, there should also be an equilibrium of moments. Since you are using solid elements, no moments can appear in nodes, so additional forces appear at the supports to counter the moment of the load. But the sum of those forces caused by the moment must be zero in the x, y, and z directions so as not to affect the force equilibrium.
Hand calculation with one support must not result in forces in the y and z direction.
it seems none is wrong, both models can be verified by stress and deflection results. However, report in reaction force is different due to opposite sign at round holes, also no moment reported in model without rigid body.
below similar case i reproduced, as can be seen vertical reaction at round holes is in range of blue (negative) to red (positive) colors. It becomes zero reactions when sum up as previously described.
That’s why I advised using rigid body constraint in the first place.
I wouldn’t say they were wrong, just different. Rigid body constraint made it possible to fix the rotations too. The rest (about the previous approach) is already explained above.
So in case your goal is to confirm your hand calc with the FE model, you need to fix the corner in X/Y/Z- and the reference point only in Y/Z-direction.
indeed for the case of rigid body or sum of reaction models, initially predicted value by hand calculation is questionable. However, individual node reaction of model without rigid body shown not and probably due to clamping, but the sign seems to make it cancelling.
Yes, there are additional forces in the hole in the numerical model, which are reaction forces that counteract the loading moment. However, these forces do not appear in the hand calculation. There you have the reaction moment.
it seems to be right, the lever arm in moment also negative thus make it an addition not cancelling. Equivalent model can be simplified by simple cantilever beam or freestanding column models.
wouldnt the corner (bottom right of your figure) only be fixed in the Z (vertical) direction? then the left side (where -F2 is) would have that -F2 reaction and the -F1 reaction.
this is due to the pin support at the bottom at the bottom right does not prevent any motion in the x direction and only prevents the bracket from rotating clockwise about Z axis.
also i ran my model with an added BC in the x direction at the bottom right edge and was getting a -80N reaction at the bolt reference node which is off
