Using a single transducer ultrasonic imaging method to eliminate the effect of thickness variation in the images of ceramic and composite plates

Comparative evaluation of aerospace composites using thermography and ultrasonic NDT techniques

“…Among the different ultrasonic testing configurations, the pulse-echo method is the most widely used approach involving the detection of echoes produced when a fraction of the initially generated ultrasonic beam is reflected by an internal discontinuity or interface. In the case of pulse-echo approach, both the generation of the ultrasonic energy and the capturing of the reflected signal can be achieved through different ways, either using a single transducer or through the aid of a phased array configuration [9,10]. Regardless the instrumentation (single transducer or multiple elements), data can be displayed in a variety of modes with the B-scan and C-scan representations being the most appropriate when internal inhomogeneities have to be assessed [11].…”

A Novel Ultrasonic Method for Accurate Characterization of Microstructural Gradients in Monolithic and Composite Tubular Structures

“…performance) of monolithic and composite [1,3,6,12]. A weakness of conventional ultrasonic velocityltime-of-flight imaging (as well as to a lesser extent ultrasonic peak amplitude c-scanning where back surface echoes are gated [17] is that the image shows the effects of thickness as well as microstructural variations unless the part is uniformly thick. This limits this type of imaging's usefulness in practical applications.…”

“…plate-like shapes [5,8,17] and incorporated into a commercial scan system [17,16]. Figure 1 shows a schematic of the immersion pulse-echo testing set-up required to use this method and the resulting ultrasonic waveforms.…”

“…Figure 1 shows a schematic of the immersion pulse-echo testing set-up required to use this method and the resulting ultrasonic waveforms. The mathematical derivation for the method [17] results in ultrasonic velocity being calculated according to: (3) where c is water velocity, 2"t is the pulse-echo time-of-flight as previously defined, and 6.t is the pulseecho time-of-flight difference between the first echo off the reflector plate front surface with and without the sample present, respectively. Water velocity (c) is determined from known relations between water velocity and temperature [2] or by direct measurement using the time difference of ultrasonic wave travel between two transducer linear positions.…”

“…This thickness-independent ultrasonic imaging method does not require prior knowledge of sample thickness as shown in equation (3) and if engineered for scanning, the effect of thickness variation is eliminated in the resulting image. Precision and relative accuracy associated with this method are estimated at near 1 percent for plate-like samples having machined surfaces [17]. The thickness-independent methods noted here [5,[7][8][9][10][16][17]20] require access to both sides of the sample, i.e., there is not a single-sided technique available for scanning that wi11 result in thickness-independence.…”