4. Appendix A: Plate vibration

4.1 Propagation wave velocity in solids

In a solid, the coefficient of proportionality between stress and strain is an elasticity constant, usually expressed in N/m ² .

We distinguish :

• longitudinal modulus of elasticity or Young's modulus E (N/m ² ) ;

• transverse modulus of elasticity or modulus of rigidity G (N/m ² ).

For all materials, there is a relationship between E and G defined by the Poisson's ratio: $\nu =1-\frac{E}{2G}$...