Reply To: shell element with orthotropic materials gives very different results from experimental data

[emirdegirmenli]

Thank you very much, Peter, you gave very important information. Twisting modes are very important for us, so I will use shell element. Generally, we use modal analysis both free conditions (ex. violin plate tuning) and full body (top glued body or ready for playing). I know full body FEA is very complicated because we have to consider other parameters such as coupling together the top, back and air inside (especially Helmholtz resonance). So First I've focused on the free plate analysis and later, I will be interested in the full body resonances by using FEA.

As I understand that there is a problem with identifying the material properties of wood. I can measure longitudinal and transverse elasticity by using resonance method ( http://ukuleles.com/?page_id=793). This method is very useful for instrument maker because getting results is easy, quick and cheaper than other techniques. But I can't obtain Poisson ratio or Shear modulus. So I need to borrow this data from other works, and I think this is causing a problem. Best,

Emir

from my measurement setup (Chladni Method):

Elasticity results according to Resonance Method,

Ey Young's modulus, h thickness, Fy bending mode frequency (dividing y-direction), Ly y-dimension length, d density (Another direction modulus can be found by using same formula)

Ex= 9,9e6 Pa

Ey= 5,1e8 Pa

Exy= 7,5e8 Pa