Lamb waves in three-layered plates: crossing fundamental branches and wave bifurcation

The analysis of dispersion portraits of Lamb waves propagating in stratified plates satisfying the orthogonal Wiechert condition reveals the crossing of fundamental Lamb modes, leading to a state of possible wave bifurcation, when the wave energy can transfer between fundamental symmetric and asymmetric modes, which results in wave instability. The analysis is based on the combination of Cauchy sextic formalism and the exponential fundamental matrix method.