  Propagation of monochromatic elastic waves across cracks is investigated in
1D, both theoretically and numerically. Cracks are modeled by nonlinear jump
conditions. The mean dilatation of a single crack and the generation of
harmonics are estimated by a perturbation analysis, and computed by the
harmonic balance method. With a periodic and finite network of cracks, direct
numerical simulations are performed and compared with Bloch-Floquet's analysis.
