Abstract: The dispersion curves of Lamb wave in orthotropic plate is solved in this paper. By virtue of wave equation of guided wave in orthotropic plate, the analytical expressions of displacement components in plate is obtained based on the solution of eigenvalue problems. Taking traction free conditions on the top and bottom surface of plate into account, the dispersion equation of Lamb in orthotropic plate is derived. Based on this dispersion equation, the range of wave numbers in different phase velocities is analyzed. Taking the dispersion equation of symmetry mode as an example, the reasonable search interval for the root of the dispersion equation is determined, and the bisection method is used to calculate the dispersion equation. Two kinds of plate, isotropic and orthotropic, are taken as numerical examples. And their dispersion curves are plotted, which are significantly different from those in isotropic plate.

Key words: orthotropic plate, Lamb wave, dispersion equation, bisection method