Kevin Rudd

Simulation of guided waves in complex piping geometries using the elastodynamic finite integration technique

Although many technologies exist for inspecting piping systems, they are most successful on straight pipes and are often unable to accommodate the added complexities of pipe elbows, bends, twists, and branches, particularly if the region of interest is inaccessible. This paper presents a numerical technique based on the elastodynamic finite integration technique for simulating guided elastic wave propagation in piping systems. Comparisons show agreement between experimental and simulated data, and guided wave interaction with flaws, focusing, and propagation in pipe bends are presented. These examples demonstrate the ability of the simulation method to be used to study elastic wave propagation in piping systems which include three-dimensional pipe bends, and suggest its potential as a design tool for designing pipe inspection hardware and ultrasonic signal processing algorithms.

Wavelet Thumbprint Analysis of Time Domain Reflectometry Signals for Wiring Flaw Detection

We describe a signal processing technique for time‐domain reflectometry (TDR) detection of flaws in wiring. For subtle flaws the backscattered TDR voltage pulses are too slight to be identified by amplitude‐based peak‐detection methods. Here, a wavelet transform is used here to convert the 1D time traces into 2D binary “thumbprint” images. Flaws are then identified according to their unique 2D time‐scale patterns in these wavelet thumbprints. The method is demonstrated for RG58 coaxial cables with varying amounts of damage to the shielding.

Simulations of Ultrasonographic Periodontal Probe Using the Finite Integration Technique

Periodontal disease is one of the most pervasive dental diseases in older adults. It involves the loss of connective tissue attachment with subsequent destruction of tooth-supporting bone, leading to loss of teeth. Periodontal pocket depth is currently measured with an invasive manual probe, but adapting diagnostic ultrasound to this purpose can avoid the pain and inaccuracy inherent in manual probing. In this paper, 3D simulations of ultrasonic periodontal probe measurements are described, using a parallel finite integration technique which is adaptable enough to create realistic anatomical geometries. The outputs of the simulation include 3D pressure values distributed throughout the periodontal anatomy, 2D vertical cross sections of the acoustic pressure waves, and the pressure across the face of the transducer which is used to synthesize the ultrasonic echo. Experimental comparison with a simple phantom is also shown. Lastly, the energy values for different simulations are calculated from the 3D pressure values to describe the amount of energy reaching different zones, especially the junctional epithelium. The simulations as well as the energy studies show that only a small portion of the ultrasonic energy is reaching the junctional epithelium, and so sophisticated mathematical techniques are required to ultrasonically measure pocket depth.

SIMULATION OF INCIDENT NONLINEAR SOUND BEAM AND 3D SCATTERING FROM COMPLEX TARGETS

This paper presents an integrated simulation method for investigating nonlinear sound beams and three-dimensional (3D) acoustic scattering from any combination of complicated objects. A standard finite-difference simulation method is used to model pulsed nonlinear sound propagation from a source to a scattering target via the Khokhlov–Zabolotskaya–Kuznetsov equation. Then, a parallel 3D acoustic simulation method based on the finite integration technique is used to model the acoustic wave interaction with the target. Any combination of objects and material layers can be placed into the 3D simulation space to study the resulting interaction. Several example simulations are presented to demonstrate the simulation method and 3D visualization techniques. The combined simulation method is validated by comparing experimental and simulation data and a demonstration of how this combined simulation method assisted in the development of a nonlinear acoustic concealed weapons detector is also presented.

Non-linear acoustic concealed weapons detection (CWD)

In this paper we describe an acoustic weapons detection concept that is based on ultrasonics and nonlinear acoustics. An ultrasonic projector is used to create an acoustic field at the site of inspection. The field is composed of multiple ultrasonic waves interacting at the interrogation site. The ultrasonic field creates acoustic interactions at that site which are used as the primary probe. The acoustic field is tailored to excite the target in an optimum fashion for weapons detection. In this presentation, we present aspects of this approach highlighting its ability to confine the interrogation field, create a narrow-band probing field, and the ability to scan that acoustic field to image objects. Ultrasonic propagation parameters that influence the field will be presented as will data of field characteristics. An image obtained with this system will be shown, demonstrating its capability to achieve high resolution. Effects of cloth over a weapon are shown to alter the image, yet not hide the weapon. Luna will report on its most recent findings as to the nature of this detection technology and its ability to generate information important to CWD.

Benchmarking of computational scattering models using underwater acoustic data from a corrugated wax slab

Measured time series for underwater acoustic scattering from a 30 cm x 30 cm x 5 cm wax slab with a two‐dimensional corrugated (rippled) surface are compared with simulation results. The experimental geometry and directionality of the sensors allowed for ensonification of the rippled surface and the appearance of shadowing effects at low grazing angles. The acoustic source transmitted impulses at 200‐800 kHz (wavelengths between 0.75‐0.19 cm). The height and spacing of the ripples were 0.3 cm and 3 cm, respectively, and the slab had negligible shear speed and a measured attenuation. We simulate the experiment with the following methods listed in increasing levels of physical accuracy and computational cost: Kirchhoff Approximation (KA), Second‐order Small‐Slope approximation (SSA2), the Wide‐angle On‐Surface Radiation Condition method (WOSRC), a Pseudo‐differential Impedance Operator method (PIO), a 2‐domain Integral Equation method (IE‐2DOM), and an Elastodynamic Finite Integration Technique (EFIT). The ...