Design of a wide-angle spectrum source for a non-destructive material characterization: low-frequency ultrasonic point sensor

To develop further instrumentation for the industrial monitoring in test and control, low-frequency ultrasonic techniques with highly sharpened end sensors that behave as point sources were examined. Due to their particular shape, these sensors eliminate coupling problems during the analysis of media. The vibration behavior of these sensors was studied using a simplified analytical approach to obtain the longitudinal vibration mode on the basis of the resonant frequency and the amplification coefficient of velocity at the sensor ends. A numerical study, based on the finite elements method, was also developed and confirmed the validity of the simple analytical approach to define the main parameters that are useful for sensor design. All the vibration modes of the sensor, that were also found experimentally by electrical impedance analysis, were calculated.