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This how task goes: i need to find deformation and stress of piston in moment of hit between piston and tool (tool is stationary). Velocity of a piston is (5-7 m/s) and forces are in picture below. I was analyzing it in "Transient Structural" because of a low velocities, but it seems not to work out.

  1. Why i can't fixate a tool by "Fixed Support" or "Displacement" (i can't choose any geometry)?

  2. Do i need to make any "Contact" or "Body Interaction"?

  3. What time to put for a solution? (I didn't quite understand this part)

enter image description here

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    $\begingroup$ Why not consider things like impact testing, see google.com/… $\endgroup$ – Solar Mike Apr 27 '20 at 9:10
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I have no knowledge of ANSYS workbench, I cannot speak for the details of the implementation in your first question. However, for the remaining two here are some comments:

  • You say that the velocity is low, but I do not completely agree. With respect to other applications it might be, but nonetheless dynamic effects definitely have to be considered. Indeed after the contact, a sort of "stress front" will be created that will propagate through the part. The problem is not quasi-static, which is usually the case when you state the the velocities are low.
  • You definitely need to set a contact between the part and the tool, otherwise one will penetrate the other with no interaction, and I assume that it is not what you want! Again, I do not know how you implement that in Ansys, but I guess that as in any FE software you have a dedicated tool.
  • "Time for a solution" is something asked by the software? I guess it might be the total time of the analysis. Considering that to model car crashes we usually run 250ms simulation, in your case 100 ms might be enough... You will have to verify it though by checking that the stress field in the part of interest has reached a stable state (that the wave of stress created by the shock should have gone through all your part). You can also estimate it better by using the speed of sound $v$ of your the material that your part is made of and its dimension $L$:
    $$ t \approx L/v$$
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  • $\begingroup$ To estimate the analysis time required, the effect of the impact will travel through the tool and the hammer at about the speed of sound in the material, which will be of the order of about 3 km/s for metal. Take the time for the stress wave to travel through the objects, reflect off the end, and come back, and multiply that by about 2 or 3. The answer will probably be much smaller than 100ms. If you want to try "transient structural," set the initial time step so you do a few hundred steps for the analysis time. Personally I would use an explicit dynamics solution. $\endgroup$ – alephzero Apr 27 '20 at 11:29
  • $\begingroup$ I totally agree that according to me the best numerical method for such an analysis would be explicit dynamic, I forgot to mention it in my answer $\endgroup$ – ClariB Apr 27 '20 at 11:35

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