Design and analysis of thickened acoustic phase reversal Fresnel lens with high-focusing performance

The accurate measurement of the contact stress of an aero-engine rotor mating surface is crucial for aviation safety. The focusing performance of ultrasonic lenses directly determines the accuracy of contact stress measurement. Phase reversal Fresnel zone plate (PR-FZP) is a new ultrasonic focusing lens suitable for contact stress measurement. A thickened phase reversal Fresnel zone lens (TPR-FZL) is proposed to improve the concentration ability. The lens replaces the path of sound waves travelling through the liquid with the Fresnel lens material, which reduces the energy loss of sound waves in the liquid and the interface of different materials, thus increasing the focus sound energy. The results showed that TPR-FZL, made of polymethyl pentene (PMP) and polyethene (PE), had relatively higher focal sound intensity. The larger the diameter of the piezoelectric plate, the stronger the focusing ability of TPR-FZL. When the material of TPR-FZL is PMP, the diameter of the piezoelectric plate of the transducer is 25 mm, TPR-FZL is the intermediate transmission type, and the thickness of the body is 35 mm, the focusing ability of TPR-FZL is the strongest. This study is of great significance for accurately measuring the contact stress on the mating surface of aero-engine rotors.