Ultrasonic Characterizaion of Subsurface 2D Corrugation

Abstract

Abstract:The ultrasonic backscattering technique is employed for the characterization of a (hidden) 2D surface corrugation which is superposed on a polycarbonate sample. Previous studies varied the incident angle at the symmetry orientations of the surface structure in order to extract the characteristic periodicities. Here, we additionally vary the orientation of the vertical insonification plane. As such the characteristic periodicities as well as the surface symmetries can be extracted without any prior knowledge of the surface structure. In addition, we apply this extended methodology to the investigation of a 2D subsurface corrugation. Although the diffraction conditions do not change in comparison with a visible 2D surface corrugation, some additional attention is required as the elastic properties of the substrate material put further restrictions to the range of applicable ultrasonic frequencies. The characterized periodicities and symmetries are in excellent agreement with the design parameters of the (hidden) 2D surface grating. ABSTRACTThe ultrasonic backscattering technique is employed for the characterization of a 2D surface corrugation which is superposed on or hidden on the backside of a polycarbonate sample. In contrast to previous studies where the incident angle at well-defined and a-priori known symmetry orientations of the surface structure is varied in order to extract the characteristic periodicities, the backscatter polar scan method incorporates an additional variation of the orientation of the vertical insonification plane within the experimental measurement protocol. As such, the characteristic periodicities as well as the surface symmetries can be extracted without any prior knowledge of the surface structure. As a benefit compared to optical methods, we have also validated this extended methodology for the investigation of a 2D subsurface corrugation. Although the diffraction conditions do not change in comparison with a visible 2D surface corrugation, we remark that additional attention is required in the sense that the elastic properties of the substrate material put further restrictions to the range of applicable ultrasonic frequencies. The characterized periodicities and symmetries are in excellent agreement with the design parameters of the (hidden) 2D surface grating.

The Ultrasonic Polar Scan for Composite Characterization and Damage Assessment: Past, Present and Future

“…Recording of the backscattered signal according to the UPS principle then results in an ultrasonic backscatter polar scan (UBPS). Depending on the employed wave, we speak of P-UBPS for ultrasonic pulses [24] and H-UBPS for quasi-harmonic ultrasound [25] (similarly as done for H-UPS and P-UPS). A schematic of the UBPS method, together with a H-UBPS recording for a [0˝] 8 C/E laminate, is presented in Figure 8.…”

“…A schematic of the UBPS method, together with a H-UBPS recording for a [0˝] 8 C/E laminate, is presented in Figure 8. Typically, a H-UBPS image is characterized by well-defined high amplitude backscatter spikes, which can be linked to diffraction phenomena under the Bragg condition [25][26][27][28]. As such, these spikes directly expose geometrical characteristics of (sub)surface structures.…”

Recent Advances in the Ultrasonic Polar Scan Method for Characterizing (Degraded) Fiber Reinforced Plastics

“…as a function of the incidence angle      , , then results in the ultrasonic backscatter polar scan (UBPS). We speak of P-UBPS [14] or H-UBPS [15] when employing a pulsed or a quasi-harmonic wave respectively. A schematic of the UBPS method, together with the H-UBPS recording for a [0°] 8 C/E laminate is presented in Figure 5.…”

A novel ultrasonic strain gauge for single-sided measurement of a local 3D strain field

“…periodicities and symmetry orientations, can be ultrasonically characterized in the Bragg scattering regime [11], simply by evaluating the backscattered wave amplitude for a wide range of oblique incidence angles ψ(φ,θ) [12]. A schematic of the so-called harmonic ultrasonic backscatter polar scan (H-UBPS) method is shown in Fig.…”