The mathematical simulation is strongly influenced by the used assumptions. In mathematical models, the natural frequencies are found for an elastic and homogeneous structure. As is known, the finite element model is a pure mathematical model on which are added some boundary conditions (blocked degrees of freedom, contacts between different parts, loads, electrical or thermal fields, etc.) As any numerical method, the finite element method induces errors but, generally, by this method it is found a global image of the analysed phenomenon.
The structural complexity of the parts and of the assembly imposes the use of finite element method as numerical method for natural frequencies determination.
To find the natural modes it was considered the modal mass contribution for each mode.