Hi all, A fixed-free bar has a single natural frequency. When we discretize such a bar in the finite element method, then the natural frequencies are the eigenvalues and an nχn matrix where n is the number of the degree of freedom which is usually large. Thus we obtain up to n natural frequencies. I don't know which one of the frequencies is the (nearly) true one. Anyone has an Idea? Your help would be appreciated. Edit: I think I was wrong and the natural frequency of the bar depends of the point of force(s).