What is the Prestress of Transducer?

Pre stress design

Due to the weak tension of piezoelectric ceramics, static compressive prestress must be applied to prevent them from bearing tensile stress during ultrasonic vibration of the transducer. Pre stressing ensures good interface contact between piezoelectric ceramics, allowing ultrasonic waves to be transmitted effectively with minimal loss.

Determine the required prestress

The compressive prestress must be sufficient to prevent the piezoelectric ceramic from experiencing any ultrasonic tensile stress and to prevent any lateral sliding of the piezoelectric ceramic. The required prestress is not clearly defined.

The characteristics of piezoelectric ceramics will change under compressive bias. Especially, the maximum safe temperature at which the material can effectively function may be greatly reduced. (This indicates that high compressive stress may lower the Curie temperature, although specific confirmation has not yet been found.)

Excessive preload can lead to significant depolarization, unstable impedance, and aging during operation.

Compressive stress cannot exceed specific limits, as they may cause mechanical depolarization, and strain cannot exceed specific limits; Otherwise, the mechanical losses of piezoelectric ceramics will increase sharply, leading to heating and causing malfunctions. Therefore, a compromise intermediate prestress must be specified. This must be determined through actual testing of specific transducer designs.

A compromise intermediate prestress must be specified. This must be determined through actual testing of specific transducer designs. Test five transducers, each with different prestress. All PZT8 piezoelectric ceramics are from the same production batch (aged for two years) and their performance is verified to be consistent before assembly. After assembly, piezoelectric ceramics are stabilized through heat treatment and cycling.