Reaction force measurement
Reaction force measurement
(OP)
Hi, I'm trying to model a force test. I want to extimate the reaction force resulting from a surface of 1mm width (made of rubber material) which is under pressure on a side and on the other one is encastred. What I want to model is a 1 second test. in this time, the pressure has to increase from 0bar to 1 bar and the force exerted from the opposite face (encastred) has to be measured. Anyone can help me setting this problem?
I have already performed a simulation, I have my geometry and I set as time of the step 1s, a load (pressure) of 0.1MPa on a face(which is 1 bar since I have all dimensions in mm scale), an amplitude, tabular, on the total step time 0--->0(first row)
1--->1 (second row). Anyway this simulation take long times and values are much higher than experimental data.
In the picture there is my geometry, a side view, just to help. i simulated the displacement of the top place, now i want fix the top face and get the force exerted by pressure
thank you
I have already performed a simulation, I have my geometry and I set as time of the step 1s, a load (pressure) of 0.1MPa on a face(which is 1 bar since I have all dimensions in mm scale), an amplitude, tabular, on the total step time 0--->0(first row)
1--->1 (second row). Anyway this simulation take long times and values are much higher than experimental data.
In the picture there is my geometry, a side view, just to help. i simulated the displacement of the top place, now i want fix the top face and get the force exerted by pressure
thank you





RE: Reaction force measurement
are you saying that the FEA is predicting very large displacements ? typical with plate theory.
why apply the load in steps ?
another day in paradise, or is paradise one day closer ?
RE: Reaction force measurement
RE: Reaction force measurement
I think that may be Abaqus' standard.
RE: Reaction force measurement
Was the material model done after several load/unload cycles (typically this is done to try and reduce the Mullin's effect which is the softening of as-molded rubber due to those same load/unload cycles)? Do you test your sample after a similar number of load/unload cycles to similar strain ranges?
"What I want to model is a 1 second test"
It is likely that the rubber material model testing was done at much slower strain rates, with the result that the model predicts a much wider contact patch (larger deflections) and higher resultant forces than the test you are performing.
RE: Reaction force measurement
btrueblood, the material is Ecoflex0050 and I meshed it with hexaedrical elements. I acquired a load/unload cycle (10mm/min) data, then performed a material test on abaqus, the result is that Ogden model (N=3) is optimal. I te experimental test, I have the same structure I posted in the pic, I pull air at pressure of 1bar with compressor in it. The structure is in contact with a load cell to acquire force data (there is no gap between the top surface of my structure and the sensitive surface of the load cell, so there are no displacemets). with this set-up I have 6.5N force @1bar. I want to model the same (or similar) in Abaqus. you're right, maybe 1s of simulation is too small, and it is not my experimental case. I'll try to augment the simulation time. Anyway, if you'll have to simulate a pressure that starts from 0bar and reach 1bar in, let's say 10s for example, how do you will set the step, amplitude, and load? this could help me in understanding how to reason.
Thank you
RE: Reaction force measurement
How certain are you that the full reaction force is sensed by the load cell? Have you played with the contact boundary condition, with a "no slip" versus a frictionless contact boundary, and compared the resultant load from both cases?