Piezoelectric Actuator Position Constraint

[mhdiab]

Hey,

I am trying to mount a piezoelectric actuator(PZT) on a plate. The PZT is rectangular and I have created a tie constraint between a surface on the bar and one of the PZT's surfaces. How do I put the PZT at a certain location on the bar in the assembly? I am assigning a coincident point position constraint between a point on the bar and a point on the PZT, is that sufficient? Thank you.

Regards.

 

[IceBreakerSours]

Firstly: Wow! You've posted this question on almost all online FEA groups, haven't you?

Secondly: I am simply trying to figure out what you are thinking because either this is too easy a question or you need to do a better job at explaining what the problem is.

*If* this question is simply about placing one instance next to another, then terms related to your specific problem (i.e., PZT) do not help. Assuming that is really the case, then what do you think should be the answer? Why do you have this question in the first place? What makes you think there may be more to it than a position constraint?

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[mhdiab]

Yes I have posted to multiple forums, usually I don't get responses when posting questions about piezoelectric simulations.
So I am trying to simulate an experiment I am performing in the lab. I have a rectangular bar and I have glued a piezoelectric sensor (acting as a transmitter) to the surface of the bar. I supply an sinusoidal electric potential to the pzt and a Lamb wave is generated in the bar. I then pick up the signals with another pzt sensor (acting as a receiver) which converts the wave to electric potential which is recorded.
For my simulation, I have created two different parts , the bar and two identical pzts ( I created the transmitter and created an identical copy of it to be used as the receiver). When I create the assembly, I first assign a tie constraint between the top surface of the bar and the bottom surface of the pzts. Now my question is : if I am trying to place the transmitter and the receiver at specific locations on the bar, do I use simple position constraint and assign a coincident point constraint between 2 points on each of the pzts and specific points on the bar?
For example , for the transmitter , let's say I am trying to place the pzt at a certain location 10 cm from the left edge of the bar, do I simply constraint one point of the pzt with an appropriate point on the bar to satisfy the condition? I honestly do not feel very confident about this method, mainly because when I apply the electric potential to one of the pzt's surfaces, it will expand and contract ( which generates the wave in the bar), however, I think that by constraining only one point , I am changing the way the wave will propagate.

Thank you for your time !

 

[IceBreakerSours]

You have not mentioned what type of analysis you plan on or are running. Are you planning on simulating sinusoidal wave generation using pzt1 and voltage recovery at pzt2? What do you gain by putting those pzt's in the model geometry? Is your focus structural analysis or a coupled analysis involving conversion of structural undulations into voltages and vice-versa? Here's why I am confused:

All of what you mentioned is simply the geometry of the test set-up i.e., bar, pzt1, and pzt2. Now, from the experiment, you said pzt2 measures voltage. What does that voltage mean? Displacement/velocity/acceleration .. ? If it is one of these variables, why do you even need pzt2? Likewise, why do you need pzt1 when all you need is a source of excitation or a forcing function (if I recall my wave equation well)?

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[mhdiab]

I am running a dynamic/implicit analysis. Yes, I am simulating sinusoidal wave generation using pzt1 and voltage recovery at pzt2. I am using the set-up for structural health monitoring.
The voltage means displacement. You are right, it would be possible to output displacement without the pzt2 , however, I am trying to simulate my experiment in which I use pzt2 to record voltage( which is proportional to displacement) so I am trying to make the simulation as close as possible to the experiment in the lab. Moreover, it is also possible to apply a point source excitation,but that would not be very similar to the experiment and it is hard to find the exact magnitude of displacement that pzt1 is applying to the bar.

 

[IceBreakerSours]

Perhaps you could experimentally measure the decay in displacement magnitude along the length of the bar or the displacement history for a few microseconds at a node or a displacement map along the length etc. and have measures like these compared against FEA results. If this approach does not result in a reasonable agreement, then think of incorporating one little additional "detail" at a time while keeping your assumptions/limitations in your mind.

Coming to your question, ideally, you may want to have displacement continuity between the surfaces i.e., merge the instances together. I know you must be using some sort of silicone gel between the surface of the transducer and the bar, but I'd try this first. An equation constraint between the opposing surfaces will do the job just fine.

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[mhdiab]

In the lab , the PZT and the bar are glued together. In Abaqus, I am using a tie constraint which is basically a perfect bond. My issue is not what constraint to apply, but how to place the PZT in a specific location on the bar. When you add parts to the assembly, the are separate parts until you constrain them. First, I apply the tie constraint which is like the glue in my experiment. Then, I need to tell Abaqus to place the PZT at a specific location on the bar. I was thinking, and I believe if I make 2 points on the PZT coincident with two point on the bar, that should do the job, don't you think? Thank you.

 

[IceBreakerSours]

Yes.

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