Localized elastic fields in periodic waveguides with defects

The variational method for determining localized waves (trapped modes) is modified for periodic elastic waveguides with partially clamped surfaces. Two sufficient conditions for the existence of localized fields in waveguides with defects (cavities with positive volume and cracks) are established. In the presence of elastic and geometrical symmetries, localized fields were also found in periodic elastic waveguides with surfaces free of external loads.