EXPERIMENTAL STUDY ON GRADUALLY VARYING THICKNESS PATCH FOR ELASTIC WAVE MANIPULATION USING PIEZO DISK ACTUATORS

In recent years, there have been several studies focused on manipulating elastic waves in thin plate structures to achieve shock reduction or energy harvesting, without being limited by frequency. An elastic patch is a promising method for such manipulation, as it can be easily applied to practical structures without compromising their stiffness or strength. Refraction of the bending wave is achieved by mismatching the effective stiffness between the host plate and the region where the patch is attached. In this study, we explored the characteristics of GVT (Gradually Varying Thickness) patches for elastic wave manipulation, modeling various types of patches (such as triangular wedge/pyramid and circular cone) and predicting wave paths using ray-tracing and density estimation algorithms. For experimental investigation, an out-of-plane vibration scanning system with a 2D auto-stage and an LDV (Laser Doppler Vibrometer) was built, and a 1-D array of 15 piezoelectric-disk actuators was attached to the host plate for generating bending waves. All the patches showed excellent performance for shock reduction in specific areas, and their propagation paths were compared with ray-tracing results. The proposed method has potential applications in protecting sensitive components from intensive shock or noise without any degradation of structural stiffness or strength.