Torque/moments in dynamics

[antknee]

I'm trying to understand the dynamics of my system a little better so I thought I would ask for your views on the principles.

I have a 3 part system, it is 2 metal parts glued and and held together by a pzt part. Part 1 is attached to a wall for example with a gentle clamp, so it can move but not fall off. Part 2 is free to move either up or down. The pzt has a voltage applied which makes it vibrate up or down.

The purpose of this system is to get part 2 to move up or down as much as possible. I have 3 options,

Position 1) Place the pzt central to part 1 and 2.
Position 2) Put more of the pzt on part 1
Position 3) Put less of the pzt on part 1

Which would you pick and why?

Thanks.

**broken link removed**

 

[JimB]

I would chose position 1.
In this configuration, there are equal fixing areas between the pzt and the metal parts, I see no advantage in having a greater area on one part or the other.

However, not knowing the structure of your pzt, I cannot comment on how the bending of the pzt will be affected by gluing to a metal bar which is presumably stiffer than the pzt.
I anticipate that the total defelecton of the free metal part will be less than you expect.

JimB

 

[antknee]

That is interesting. I have looked at torque and it depends on the the force applied and the distance from moment/clamping point. So I was leaning towards position 3 - in moving the pzt more across part 2 there would be more pulling power upon it acting up and down and it would have greater length from the clamping point/moment. The deflection will be small, its around 5 micro meters per volt, so it helps to have high volts.

Thanks for your comment

 

[JimB]

You keep refering to torque.
Torque is a turning moment, such a twisting in a shaft which is turning and transmitting power.
I don't have the big picture of what you are trying to do, but I don't see how torque is relevant here.

JimB

 

[antknee]

I think torque is the wrong term to use. I am making the system in the picture, in that I've ordered the pzt, it is 19mm x 12mm x 1.5mm. Now I need to order the metal which means deciding what dimensions I need. I'm looking for advantage and to get the best movement of part 2 by placement of the pzt.

My thought is something like this - the force required to produce displacement is less at F2 than F1, so if I move the pzt towards F2 I will get displacement with less force. The force produced by the pzt is proportional to the volts applied, so I'm looking to use fewer volts.

Thanks.

 

[JimB]

My thought is something like this - the force required to produce displacement is less at F2 than F1, so if I move the pzt towards F2 I will get displacement with less force. The force produced by the pzt is proportional to the volts applied, so I'm looking to use fewer volts.

Your thinking is all screwed up!
What you have written would be true if you were trying to bend a cantilevered beam, but you are not.

You have a cantilevered beam which supports a PZT.
The PZT "bends" creating a deflection at the end of a second beam which is supported by the PZT.

Can you post a link to this PZT?
I do not understand how it is physically configured.

JimB

 

[antknee]

Your thinking is all screwed up!
What you have written would be true if you were trying to bend a cantilevered beam, but you are not.

You have a cantilevered beam which supports a PZT.
The PZT "bends" creating a deflection at the end of a second beam which is supported by the PZT.

Can you post a link to this PZT?
I do not understand how it is physically configured.

JimB

I get it, so actually your first thought put the pzt over the middle was correct!

I can't post a link because its not off the shelf stuff, it has to be specially made.
Regards,

Antknee.