I have a rectangular beam, sitting over another beam. At the moment only gravitational force is acting. I also have a surface-to-surface tiebreak contact between these beams. I simply ran the simulation just to see that there is no fault. But then I took the rcfrc, which I believe is the reaction force at the contact surface. Here I observe that Z-force (vertical force or z is the direction of gravity applied) is increasing over time and it is way more than the weight of the beam sitting on top. Do you think there is something wrong with my model? or is this the way it is supposed to act? Even the defined gravitational force is the same over the time.
Appreciate any thoughts on the matter.
I'm a tad confused. Is the bottom beam also constrained in space so the top beam is slamming into it like in the pipe whip tutorial or somthing? Or do you mean 'the only thing acting is gravity' also means no boundary constraints?
Otherwise, they will both be falling into eternal nothing-ness.
I'll assume the bottom one is fixed for now. Following the golden rule of troubleshooting, the simplest problem I can think of is some issue with your gravity implementation. You might be applying an inappropriate scale factor making it a zillion times higher than it needs to be, or multiplying it over time, or whatever other options are in those cards. So I would double-check those if you have not. Same thing for the gravity value's definition if you defined it with a curve and load_body_z. I hear defining it as a ramp instead of a constant could net you really poor results.
If you haven't looked there, I hope it points you in a good direction. Otherwise, let us know what troubleshooting you have already tried. I never want to be patronizing.
This is not an issue, but I am curious, why tiebreak? Is the plan to rip them apart in your final sim?
😆 @ " .. falling into eternal nothing-ness." Good one!
In addition the excellent suggestions above, here are my two cents:
Are you using the implicit (static or dynamic) or the explicit scheme? As this particular simulation starts off, is contact established or does contact get established in some time steps? Look at the time history of the displacements/velocities/accelerations of some interesting entities (nodes, parts) and get a feel for what is going on in the simulation.
Thank you both for your response.
The bottom of the block at the base is fixed in all directions. The gravitational load is, a curve 10m/s at 0s to 1s. Scale factor is 1 in load body z. So it was a constant value throughout the time scale.
Tiebreak, yes I want to rip it apart like it is an interphase zone between a pin and resin bond. This is my final model. I had some unexplainable results there that made me confused. and that is what brought me to ripping out all other loads, just see what happens when only gravity acts. Like see if software is working properly, and so on.
implicit is being done at the moment. My aim is to have dynamic simulation. Because a stress wave is passing through this bar and I want to see the damage at the contact for the 1st stress wave which is like in 0.0008s.
If you are having issues with gravity, I would suggest following the implementation suggested in this LS-Dyna example:
https://www.dynaexamples.com/introduction/examples-manual/load/gravity
$ Units: mm, kg, ms, kN, GPa, kN-mm
*LOAD_BODY_Z
$
$ lcid df lciddr xc yc zc
1 9.810E-03
$
$
*DEFINE_CURVE
$
$ lcid sidr scla sclo offa offo
1
$
$ abscissa ordinate
0.00 1.000
1000.00 1.000