Understanding slowness curves

This WidgeNDT is an interactive tool allowing to predict modes, their velocity and their propagation direction depending on the incidence angle when passing through a plane interface between an isotropic and an anisotropic medium (representative, for instance, of a steel transformed by thermal treatment, of some welds, or of composites).


launch the WidgeNDT (requires Java to run)


The properties of the propagation medium are adjustable through horizontal pointers: the waves’ velocity in the incidental isotropic medium, and the stiffness tensor’s coefficients in the anisotropic medium.

Thus, depending on the selected incidence angle, the possible propagation modes’ velocities are displayed. The graphic also illustrates the phase direction (propagation direction) through a dotted lined arrow, and the energy direction (group velocity) through a full half-line.

An animation on the variation of the incidence angle may be launched by clicking on the “Play” button in the bottom left corner of the page, triggering a dynamic drawing of the slowness curves associated with the propagation modes existing in the anisotropic medium in a defined observation plane (the angle of this observation plane may also be adjusted through a pointer).

The video below illustrates how this WidgeNDT works:

Feel free to play with this tool, inform people around you of its existence, and share with us your comments and critics!