High-temperature integrated and flexible ultrasonic transducers for nondestructive testing

Structural health monitoring ultrasonic thickness measurement accuracy and reliability of various time-of-flight calculation methods

“…A total of forty four sol-gel sensor element transducers [5,6,7] were directly deposited in 2 x 2 array groups onto a flat step calibration block with a 0.10 ± 0.005 mm step size from 24.00 mm to 25.00 mm as shown in Fig. 2 and previously described [19,22].…”

“…It is prudent to first establish a method to statistically quantify the measurement uncertainty, then apply the method to a significant number of sensors in a baseline scenario on a smooth surface at ambient temperature before taking measurements in more extreme environments at elevated temperatures, for rough back-wall surfaces, and for system degradation over time. This paper addresses sources of uncertainty in structural health monitoring ultrasonic thickness measurements, proposes a weighted censored relative likelihood analysis method to capture asymmetric measurement uncertainty, and demonstrates the method using sol-gel transducers [5,6,7] in calibration of the measurement system and in establishing the baseline thickness measurement error accuracy and precision for a number of relatively simple time-of-flight thickness calculation methods.…”

High temperature guided acoustic wave transducers using mechanical gratings

“…The gratings will be used to convert L waves into SAWs [6,7] and PAWs depending on the substrate thicknesses. Piezoelectric lead-zirconate-titanate composite (PZT-c) films served as L wave integrated UTs (IUTs) were made by a sol-gel sprayed technique [4,10] onto the opposite surface of the metallic substrate having the mechanically gratings. The merit of this approach is that IUT can be at the internal surface of a structure and mechanical gratings at the external surface.…”

“…The sol-gel spray fabrication method of the PZT-c film consists of six main steps [4,11]: (1) preparing a high dielectric constant PZT solution, (2) ball milling of piezoelectric PZT powders to a submicron size, (3) film spraying using slurries from steps (1) and (2) to produce a layer of slurry film onto thin metal membrane substrates, (4) heat treatment to produce a solid PZT-c film on the metal substrates, (5) corona poling to obtain piezoelectricity of the composite ceramic film, and (6) electrode painting of electrical connections. Steps (3) and (4) are performed multiple times to produce the proper film thickness for optimal IUT and FUT ultrasonic operating frequencies.…”

“…For aerospace industry such SHM and NDE may require that the UTs operate from -80°C to 100°C. In other areas the operation temperatures may be required to be higher [3,4]. Guided waves may be surface (SAW) or plate acoustic waves (PAW).…”