Learning Forum

[dinhan0394]

Dear all,

 

I tried to perform a simple piezoelectric using LS-DYNA: a piezoelectric block with a fixed bottom surface and a pressure load on the top surface.

 

I have referred to the results from some other examples, the voltage results are evenly distributed.

As done in LS-DYNA, the results do not have such a distribution but are skewed as shown in Figure 2.

- Reference:

 

LS-DYNA result:

Does anyone know how to fix this or have a simple example?

Thanks

[peteroznewman]

To get a uniform voltage response across the body, I suggest you delete the Fixed Support and replace it with three displacements: X=0 on one face with an X-axis normal, Y=0 on one face with a Y-axis normal and Z=0 on one face with a Z-axis normal. In each displacement boundary condition, the other two displacements are left Free. This will allow the body to freely expand on the free sides due to Poisson's Ratio effect as the pressure compresses through the thickness.

[dinhan0394]

Dear peteroznewman,

Thank you for your suggesstion. I tried it but the results are the same.

Voltage result:

When I active the piezo effect, all results look not good (it is always skewed in a certain position)

Here is X-displacement (direction of force)

[peteroznewman]

The results are not the same, but I see it is not what you want.
The voltage in your original post goes from   -66 to +25 volts.
The voltage with the new boundaries is from -71 to +16 volts.

Maybe someone else will have a suggestion.

[ErKo]

 

 

 

 

 

 

 

Hi 

In the ABAQUS image – bottom is grounded – do the same in your model (ground -> volt=0).

Finally I think in the ABAQUS model has pressure both on top and bottom

In general it is hard to use the PZT as the anisotropic mat. properties are hard to set up.

Alternatively:

Easier in Mechanical – see this example in the ansys help manual:

Chapter 39: Wire Bonding Ultrasonic Transducer

All the best

Erik

 

 

 

 

 

 

 

[dinhan0394]

Dear Erik

Thanks for your suggestions.

I have solved this problem using Ansys Mechanical. Now I want to use LS-DYNA due to some technical requirements.

As you said, the difficulty in this problem is related to the material definition. In LS-DYNA, the keyword MAT_ADD_PZELECTRIC is used to declare the piezo property but I did not understand the direction of the quantities in it clearly which leads to the error.

Now I have a good solution after changing the values ​​of some parameters in that model but I did not really understand it clearly.

If you can share any document to explain the material parameters, it would be very helpful.

Thank you.

[nishant.singh]

Dear dinhan0394.

May I know, how you are setting up the output to see voltage ?

[dinhan0394]

Hi nishant.singh 

In this problem, Z-acceleration result is Voltage output.