Simulation of non-linear thin material in IDEAS for defects

[mirza037]

Hello everybody,

I would like to know what are all the factors effecting the resonance frequency of a structure(non-linear material in particular).

I am using the following properties to define the material in IDEAS , which is paper for food packing purposes.

Youngs modulus - 2755 mpa
bulk modulus - 1059 mpa
poissons ratio - 0.3
mass density - 684 kg/m^3

Unfoutunately i get all the resonance peaks less than zero when i derive the FRF for the structure, which does not correlate with the experimental results.

what else do i need to define for the material to get the correct frequency peaks? Is it damping or stifness or what?

Thanks in advance
Mirza