An ultrasonic multi-wave focusing and imaging method for linear phased arrays*

To overcome the inherent limits of traditional single wave imaging for nondestructive testing, the multi-wave focusing and imaging method is thoroughly studied. This method makes the compressional waves and shear waves focused in both emission and reception processes, which strengthens the focusing energy and improves the signal-to-noise ratio of received signals. A numerical model is developed to study the characteristics of a multi-wave focusing field. It is shown that the element width approaching 0.8 wavelengths of shear waves can keep a balance between the radiation energy of two waves, which can achieve a desirable multi-wave focusing performance. And an experiment using different imaging methods for a linear phased array is performed. It can be concluded that due to the combination of the propagation and reflection characteristics of two waves, the multi-wave focusing and imaging method can significantly improve the imaging distinguishability of defects and expand the available sweeping range to a sector of –65° to 65°.