# Snap-through-stability

Snap-through-stability experiment
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amandaghassaei says: Oct 16, 2012. 10:14 AM
this is very cool! so how to do you explain the difference between the experimental and theoretical curves?
skorpijon in reply to amandaghassaeiOct 17, 2012. 12:59 AM
Hi, you have a lot of questions for me ;)
It is explained on 4 and 5 slide.
The difference is:
- curve shifting -> air is compressible, so to get the generated force you must first compress it and then the experimental curve follows the theoretical curve (curves are parallel). This is why in first 5mm force rises so quick and than it follow the curve.
- critical force for snap through -> we can blame friction, why? error of 5% is not a big deal, because all the theoretical and experimental results are in thiswindow of error. If we had 10% of error, than sometnig woudl be wrong adn we would have to change the experiment or there would be something wrong with our mathematical model or we would look for an error in equations. So, the reason for 4,7% error is friction betwean shoch absorber that rotates arround the screw and friction between the slider and the bar in the middle.
skorpijon in reply to skorpijonOct 17, 2012. 1:31 AM
Best example would be with one shock absorber. Than you woul see the error for one spring. But the problem would be the slider and then the force of adhesion and friction. Or you can make an example with 2 shock absorbers and I guarantee you, that the results are better (less error), but you will have problem with force. Force will be 170N so the exercise will be over very quickly and students will show no interest or you can change the angle to 30 or 40Â°, fut then you will not have a shallow like structure and students will again loose their interest.
With this exercise they become interested and than they themselves want to change the angle and go to less shock absorbers.
skorpijon in reply to skorpijonOct 17, 2012. 1:33 AM
At 170N you would not need any force, the system would snap by itself.