Approaches for determining the properties of materials by FEM

Finite element modeling (FEM) is a very powerful tool for designing transducers, but precise values of material properties are essential. By the traditional experimental method, a ceramic should be made into a special shape so that only one mode dominates and is treated as a one dimensional problem. Because it is difficult to isolate multi-mode interference, traditional experiment methods yield significant errors. This paper outlines approaches for determining properties of materials by choosing a round disk of ceramic, measuring a set of resonant frequencies and impedances and using finite element modeling. The usual difficulty with this approach is that resonance frequencies are affected by almost all the elastic constants. With the large variety of possible combinations, it is difficult to arrive at a unique solution. We first investigate how the individual elastic constants affect basic eigenmodes differently. We then proceed to determine elastic and piezoelectric constants in an orderly fashion. Practical examples are given step by step