Plastic Strain Determination With Nonlinear Ultrasonic Waves Using In Situ Integrated Piezoelectric Ultrasonic Transducers.

The detection of plastic deformation of metallic alloy materials with second-harmonic Rayleigh ultrasonic wave is first investigated using direct-write piezoelectric ultrasonic transducers, in which piezoelectric poly(vinylidenefluoride/ trifluoroethylene) [P(VDF/TrFE)] polymer coatings and electrodes are directly deposited, processed, and patterned on the alloy to be evaluated. Rayleigh ultrasonic signals, generated by the direct-write transducers on titanium alloy specimens, are characterized by a laser scanning vibrometer. The results show that acoustic nonlinearity increases with plastic strain, and an increase of ~40% in the acoustic nonlinearity corresponding to a plastic strain of 5.1%. The measurement data and technical features with the use of the direct-write transducers are compared with the conventional discrete angle beam piezoelectric transducer. The results and analyses show that compared with the conventional discrete angle beam piezoelectric transducers, implementation of the direct-write piezoelectric transducers has significant technical advantages and is promising for applications in determining nonlinear ultrasonic waves and plastic strain of structural materials.