tode
Aerospace
- Jan 24, 2014
- 1
Hello,
I am performing an explicit analysis on a COREVALVE stent. The structure is made of beam elements. I performed an eigenvalue analysis before starting with the explicit analysis.
First to begin with the contact analysis I want to perform a crimping step and after an expansion step. For both step I chose smooth steps amplitudes. The time period I have been chosen is an order of magnitude bigger than the inverse of the first eigenfrequency.
For the crimping steps I apply radially some displacements so that the stent crimps into an uniform cylinder.
The same thing for the expansion, just with opposite sign. All the nodes at the bottom of the stent are constrained to move only radially (respect the stent axis).
When I monitor the energies I notice that everything is as expected for the crimping. The kinetic energy moves smoothly from 0 to the maximum value at the middle of the time period and return to 0. The internal energy has the same shapes of the smooth step (smoothly from 0 ti the maximum value). Finally the total energy is almost 0 for all the period. For the expansion step I am expecting the same thing, with the internal energy going from the maximum to 0.
But when the next step begins there is suddently a big jump in kinetic energy. In fact the next step doesn't begin with a 0 kinetic energy but with a KE of 4. The total energy goes immediately from 0 to -80 and the internal energy goes from 450 to 470.
I tried to change time step, I tried mass scaling without, change boundaries without results.
Thanks for the replies
I am performing an explicit analysis on a COREVALVE stent. The structure is made of beam elements. I performed an eigenvalue analysis before starting with the explicit analysis.
First to begin with the contact analysis I want to perform a crimping step and after an expansion step. For both step I chose smooth steps amplitudes. The time period I have been chosen is an order of magnitude bigger than the inverse of the first eigenfrequency.
For the crimping steps I apply radially some displacements so that the stent crimps into an uniform cylinder.
The same thing for the expansion, just with opposite sign. All the nodes at the bottom of the stent are constrained to move only radially (respect the stent axis).
When I monitor the energies I notice that everything is as expected for the crimping. The kinetic energy moves smoothly from 0 to the maximum value at the middle of the time period and return to 0. The internal energy has the same shapes of the smooth step (smoothly from 0 ti the maximum value). Finally the total energy is almost 0 for all the period. For the expansion step I am expecting the same thing, with the internal energy going from the maximum to 0.
But when the next step begins there is suddently a big jump in kinetic energy. In fact the next step doesn't begin with a 0 kinetic energy but with a KE of 4. The total energy goes immediately from 0 to -80 and the internal energy goes from 450 to 470.
I tried to change time step, I tried mass scaling without, change boundaries without results.
Thanks for the replies