How can I plot mode shapes from a rectangular plate?

I computed natural frequencies, damping ratios and mode shapes of a rectangular plate from experimental measures (I don't have M, C and K matrices). So I have the complex mode shapes and I want to plot them on a 3D model of the plate without thickness (even a wireframe model would be good). I created a matrix that represents the plate and placed the values coming from the components of mode shapes (after some manipulations since they are complex) in the element of the matrix that correspond to the positions of the accelerometers on the plate, but obviously all the other elements remain equal to zero. So I decided to interpolate the values giving weigth 0 to the zero elements of the matrix and 1 to the measured points, but the result is not good.

I used Curve Fitting tool.

Has anybody faced a problem like this? Thank you for your help.

[jonas]

Can you upload the data prior to interpolation?

[Donato Foggetti]

Let's say that this is my matrix (it's just an example). Every element corresponds to a "node" (so to speak) and the ones different from zero are the measured nodes.

z = [0   0   0   0;
     0  0.5  0   1;
     0   0 -0.3  0;
     1.2 0   0   0];

Remember that the computation is not a FEA, so it's not correct to talk about nodes.

[jonas]

That matrix seems very sensitive to interpolation/extrapolation method. Do you want to replace those zero by interp?

[Donato Foggetti]

Yes, I tried with a polynomial interpolation with different orders but I didn't get the result I expected.

Answer 1

[KSSV]

Have a look here: https://in.mathworks.com/matlabcentral/fileexchange/32719-postprocessing-in-fem

[Donato Foggetti]

It seems a quite complicated set of function and I wonder if there is a simpler solution, since basically I want to "plot a matrix".