Compliant mechanisms with NO stiffness!?! -
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- Опубліковано 19 жов 2024
- #VeritasiumContest
I am posting this video in response to a contest announced by Veritasium challenging educators to explain a counter intuitive concept in one minute or less (www.veritasium....
Since the prize money is coming from a UCLA professor who lost a physics bet to Derek from Veritasium, this is my attempt as a fellow UCLA professor to redeem my university’s reputation.
This video explains how compliant mechanisms can use prestressed flexures to achieve zero stiffness at their resting position. This property is highly counter intuitive because compliant mechanisms deform by definition and one would think that deformations always produce resistance and thus stiffness. But they don’t if the principles of stiffness cancelation and static balancing are implemented!
The compliant mechanisms presented at the end of the video were designed by Reinier Kuppens ( / mrreinish ) while he was visiting my lab at UCLA from Delft University. The designs are published in the journal, Extreme Mechanics at the following link:
www.sciencedir...
Apologies to my subscribers if they have already seen my lengthier videos about this concept. You can check them out on my channel “The FACTs of Mechanical Design” ( / thefactsofmechanicalde... ) at these links if you haven't seen them:
• “Binary Stiffness Comp...
• “Binary Torsional Stif...
Also if you are interested to learn more about compliant mechanisms, check out the compliant mechanism course videos on my channel, or see the following Veritasium video:
• Why Machines That Bend...
The part files for these mechanisms can be downloaded from Thingiverse at:
www.thingivers...
Acknowledge: This work would not have been possible without the help of Reinier Kuppens, Just Herder, and Miguel Bessa.
Donate to help support my channel:
If you’d like to make a one-time donation, you can use the following link:
PayPal.me/FACTsMechDesign
Thank you for your support! It is much appreciated and helps enable me to make more content.
Disclaimer: Responsibility for the content of this video is my own. The University of California, Los Angeles is not involved with this channel nor does it endorse its content.
that ending shot almost made me spit out my drink. i was like okay man how will u put that pre-flexed part in bro and then CLICK and he does it
man where tf you been
bro man’s csgo content and robs stores by day, designs compliant mechanisms by night.
Honestly, this one might be a winner. Really amazing principle! Puts my submission to shame... :( I wish I had a 3D printer to test it out
This is almost like virtual particles in that it's a useful abstraction that highlights a truth about how compliant mechanisms move, but also not meant to be literal, even though it can be used in a literal way.
No
Somewhat related: When chemical bonds are stretched then there is a point where with additional stretching the restoring force no longer grows but shrinks and the bond breaks if the applied force stays constant. Zero stiffness.
Also an oddity from non-linearity of atomic bonding forces: Nanoscale bearings can be stably centered even if the axle/shaft is attracted to the sleeve/wheel. Only when stiffness becomes zero and negative the axle/shaft becomes unstable and sticks to a side of the sleeve/wheel (van der Waals forces).
Almost, except that the compliant mechanisms shown at the end are still self centering.
Still seems reasonable.
Even if you don’t win this competition thing I just found, you earned my sub!
Very good video already! I would recommend editing the initial section of the video shorter to allow better demonstration of the mechanism and its advantages at the end within the 60 second limit.
Now I know a thing which I don't understand which I didn't knew.
Strong contender
And a weak one here ==> ua-cam.com/video/ZqvlSIksrIQ/v-deo.html
Oh man this is getting heated 🔥🔥
nice pun !
I hope you have more of that for this video ==> ua-cam.com/video/ZqvlSIksrIQ/v-deo.html
@@SimplementEddo That's pretty good English, I wish I knew French. Alas, too difficult and not enough time. Good luck on the contest!
@@cognitiveconsonancescience2937 Thank you man !
You could pick an other language though :) Spanish is apperently easier to learn and VERY usefull worldwide.
It looks to me that the systems have a low stiffness not NO stiffness.
Yes because achieving zero stiffness with this approach is as hard as achieving any other stiffness with even usual flexures. You'll always be off by some small percentage (for instance 3.000001 instead of perfectly 3 because of imperfections etc). But theoretically this approach could be used to achieve zero stiffness just as any flexure can achieve any other stiffness value. And yes the mechanisms at the end were just very low stiffness--not zero. You can see my other videos that explain them in more detail. In any case, in a one minute video I'm comfortable claiming zero stiffness to teach the concept.
@@TheFACTsofMechanicalDesign 1) Yes the 1 min limited makes et impossible to explain something like this well enough to not leave some questions.
2) I have seen your other videos, and i loved the part where you showed measuring the stiffness... 0.08 N/mm is close to zero, but maybe a competition in designing a konstruktion with as close to 0 stiffness as possible could end up with some good designs.
3) If I wanted to make a system with a stiffness of 3 N/mm, I would make it adjustable such that I could fine tune it af afterwards, maybe this is also possible for designes aiming for 0 stiffness.
4) also... how dit you release 100 videos without making a announcement video for you subscribers...
It is going to be a hard weekend with 100 videos....
Thanks for them, it is really cool of you.
@@TheFACTsofMechanicalDesign If only they'd given you 90 seconds! :)
as i understand it the actual stiffness for real flexures is nonlinear so you would need an infinite number to cancel out all the elastic force at all points, that being said you can make a finite system that really has zero stiffness at multiple points (all flexures have at least one point with 0 stiffness or else you could make a free energy device)
Wonderful video. You explain everything so well.
Incidentally, I have also discovered this. Put your opposite finger pads together with all five fingers of the hand. Then press your fingers against each other and focus on the pentagon formed by them. Now while pressing with a constant force, make that pentagon shrink and grow a couple times. I can describe the feeling of this like my fingers sliding on a flat sheet of slippery glass.
just tried it out and you are right, it does feel like slippery glass. thanks for the cool new sensory illusion!
quite interesting and impressive, well done!
That’s SO COOL!
Man is on a highway to victory
This man is getting all the views while us with 0 subscribers are suffering 😭😭😭
yeah we got no chance to even make it to the qualifiers
Promote your videos tp friends and families and ask them to share.
Another really nice one!
Bounced on my boys non-compliant mechanism to this until it became zero stiffness.
why are you all over my youtube
also why are these videos so good
This mechanism is remarkable and well described.
good job good luck
I didn't understand anything but I liked what I saw
I see I see I have lost this video is great good job
What about roller flexures?
really strong opponent, good luck mate, gonna try to match you, haha but in all due respect, that was amazingly put
IIRC tensegrity structures have exactly zero stiffness at their equilibrium unloaded position.
The graphs did it for me, but I'm an engineer... :)
guy: "this mechanism has no stiffness"
video: literally shows the thing spring back
It's zero in the center
@@blinded6502 The it's non-linear stiffness not zero stiffness.
@@henrychan720 Non-linear stiffness with zero stiffness in the region around center
All of compliant mechanisms are meant to be used only in some small range of translations
@@blinded6502 But it's clearly not zero, or it would not auto-centre, it would stay wherever in the zero range it was placed. Clearly the stiffness merely approaches zero, it never achieves it except possibly at zero-size points.
Hey, great video but do you mind explain what do it means by 0 stiffness? Like do it become unmoveable, less moveable or something?
Something with zero stiffness can't produce a resisting force if you try to move or deform it
It means that a body constrained with appropriate flexures can move easily without resistance.
@@TheFACTsofMechanicalDesign Wouldn't it also meant that the mechanism wouldn't automatically return to the original position? Do you mean that the force pushing towards to original position is not increased when the deflection from the original position is increased? I think that would actually be constant force instead of zero stiffness. For example, springs cause non-constant force towards the original position.
If the slope of the force displacement plot is perfectly flat at the origin but then increases slightly to the right of the origin, the mechanism still has zero stiffness when its at rest but if perturbed will return to its original position. Also although the approach theoretically allows one to design mechanisms with zero stiffness at their resting position, in practice, when you build the mechanism you'll never actually get perfect zero stiffness and so you'll never really achieve true zero stiffness, just like you can never achieve true any other stiffness value you aim for. (e.g., If you shoot for 2N/m you'll be lucky to get 2.0001N/m etc.). So although the approach presented allows for zero stiffness theoretically, the mechanisms shown just have really small stiffness values as reported in the published paper if you're curious to read it. But yes if something had zero stiffness over its full range like a disconnected stage from its ground and you moved the stage, it would not return it its original location so you understand the principle.
@@TheFACTsofMechanicalDesign Technically it is only not stiff in one dimensional making it anisotropic, a 2D or 3D zero stiffness device would look sick
So no stiffness around center, yet it still self centers and springs back and forth.
You should pay attention to how graph looks.
Can we design high precision (for sub-micron positioning) flexure (metal) with 3D printing?
Sub micron? This would be a MEMS application.
Well, the mechanism returns to centre, so by definition, the stiffness is not zero.
It's zero in the center.
It is still not 0 stiffness though, as it clearly self-centers
I think you can only approximate zero stiffness by this method.
Great explanation
Эээ... а где эстиэльки??!
I hear words
sir, how do you make those graphics?
0:41 is where I struggle…🤔
😲😲
what
i'm gonna need you to take down your videos i don't need stiff competition, the indians are already giving me a run for the money.
超级酷！
witchcraft.gif