Development of the technique for independent dual focusing of contact type ultrasonic phased array transducer in two orthogonal planes

•Spatial dual focusing in two orthogonal planes has been performed simultaneously.•Developed special delay line with the convex lens enables to test thin samples.•Dual focusing provided the enhancement of testing resolution.•Achieved improvement in defect detection is from 33% up to 83%.•The interfaces of the multi-layered aluminium composite were detected.

Due to a low lateral resolution in elevation plane, the application of linear ultrasonic phased array transducers (ULPAT) is limited. The objective is to enhance the spatial resolution by means of spatial dual focusing technique of ULPAT in two orthogonal planes - azimuth and elevation.A design of a special delay line possessing a convex cylindrical lens has been proposed. The lens enables fixed geometrical focusing of the excited beam in the elevation plane, while in the other, azimuth, plane the beam is electronically focused at an arbitrary point by the active aperture of the ULPAT. The simulation results demonstrate the extended possibilities of resolution enhancement. Experiments show that the undetectable defect is detected using the designed acoustic lens. In addition, the interfaces of the intermediate layer of metal composite were detected.