Learning Forum

[sinyin]

Hi everyone,

I am new to ansys and would like to know how to do a simulation (compression test) on my bone model. How do i do with the analysis setting and displacement? Also, how do i make the platen rigid? Could anyone kindly help me out?

Thank you in advance.

[peteroznewman]

nFind the platen body in the outline and in the Details window, you can change the Stiffness Behavior from Flexible to Rigid.nAdd a frictional contact between the bottom face of the platen and the face of the bone. You must pick the platen face to be the Target and the bone face to be the Contact side of the contact pair.nUnder the Connections folder, insert a Contact Tool and Evaluate Initial Contact Status. The contact must show as Closed. If it is Near Open with a tiny gap, edit the Contact and under Geometric Modification, Interface Treatment, use Adjust to Touch.nAdd a Remote Displacement to the top face of the platen. Change all values from Free to 0 to hold the platen fixed, except for the Y displacement, which you will make -2 mm.nAdd a Fixed Support to the bottom face of the bone.nUnder Analysis Settings, turn on Large Deflection.nUnder Step Controls, set Auto Time Stepping to OnnMake the Initial Substeps to be 100.n

[sinyin]

can I make Y displacement -10mm instead? nUnder analysis setting, may i know if i should keep the other step controls as:nNo. Of steps = 1nCurrent step number = 1nStep End Time = 1.snMinimum substeps = 10nMaximum substeps = 100n

[sinyin]

For this step: Add a frictional contact between the bottom face of the platen. nIs it ok to input friction coefficient value as 0?n

[peteroznewman]

nYes, try -10 mm, but only after you see -2 mm converge. If -2 converges by -10 doesn't, then make it a 2-step solution and -10 can be the displacement in step 2.nI recommend you try the solution with a friction coefficient of 0.1 because that helps to stabilize the structure. But you can try to solve with a 0 value instead.nFor screen snapshots, it is better if you learn to use the Windows Snipping Tool rather than your cellphone camera to insert images into the forum.n

[sinyin]

i tried -10mm with 2 steps, but it still does not converge. There is no problem with -2mm.nThere is also warning message: One or more MPC contact regions or remote boundary conditions may have conflicts with other applied boundary conditions or other contact or symmetry regions.n

[peteroznewman]

Try making step 2 be -4 mm and see if that converges. nThat is a common warning and is often safe to ignore once you have seen that the solution is behaving the way you expect. However, by carefully applying contact and boundary conditions, you can avoid getting this warning. n

[sinyin]

it does not converge with -4mm at step 2.n

[sinyin]

do you have any suggestions on how could i change the settings so that it will converge at 10mm?nI have ensured that all contacts are closed.nFor force reaction, is the boundary condition= remote displacement?n

[peteroznewman]

nWhy do you need to go to 10 mm? Do you have experimental data that showed a test sample being compressed that far? Did the sample fracture before reaching that point?nWhat is the exact error message in the Solution Output (solve.out file) when the solver stops?nThere are different corrective actions depending on the specific error.nYes, use the remote displacement in the Force Reaction probe.n

[sinyin]

yes there are experimental data with 10mm displacement using abaqus. I am trying to reproduce the data in ansys. The experimental data shows convergence and plotted vertical reaction force against displacement.nI have attached to error message.nn