Abstract: A new kind of tubular radial composite piezoelectric ultrasonic transducer is presented and studied. The transducer is consisted of an outer metal prestress tube, a metal expandable inner core and a ring group of cylindrical piezoelectric ceramic slice, which are composited in the radial direction. Based on the elastic mechanics theory and the electromechanical analogy, the electromechanical equivalent circuit of a ring group of cylindrical piezoelectric ceramic in quasi-thickness vibration is obtained. The radial vibration equivalent circuit and the resonance frequency equation of the tubular radial composite piezoelectric transducer are derived. The relationship between the resonance and anti-resonance frequency, the effective electro-mechanical coupling coefficient and the geometrical dimensions of the transducer is analyzed. It is illustrated that the first order radial resonance frequency of the transducer are decreased with the inner diameter of the inner core and the wall thickness of the outer prestress tube of it is increased. The effective electro-mechanical coupling coefficient of the transducer decreased with the inner diameter of the inner core increased, while it exist a maximum value as the wall-thickness of the outer prestress tube increases. The radial resonance frequencies of some tubular radial composite piezoelectric transducers are tested. It is shown that the theoretical results are in a good agreement with that of the measurement.

Key words: Composite piezoelectric transducer, Electromechanical equivalent circuit, Frequency equation, Radial vibration