Simulation tools for ultrasonic inspections of multi-layer armor panels

Some armor panels are fabricated from several layers of material including ceramics, graphite and∕or glass composites, and rubber. This multi‐layer makeup can complicate UT inspection, since many possible sound paths (including intra‐layer reverberations) can contribute to observed UT signals. At last year’s QNDE conference we reported on baseline property measurements (density, sound speed, attenuation, etc.) for the constituent layers of one prototype panel, and we discussed how that information was used to design an ultrasonic inspection to look for disbonding at interfaces. We now report on progress to develop better simulation tools for armor panel inspections. In particular we consider normal‐incidence pulse∕echo inspections and use a paraxial beam model to predict time‐domain signals for unflawed panels and those containing large delaminations. The model uses the frequency‐dependent baseline property data as inputs, and treats beam spread and focusing effects. We describe the modeling approach and present comparisons of model predictions to the experimental data gathered last year during inspections of five‐layer armor panels

The Importance of Regional and Landscape Context and Climate Change to Northern Bobwhite Management

Long-term declines in northern bobwhite (Colinus virginianus) in the United States are presumably due to decades of habitat loss or degradation at a national scale. Food and fiber production characterized by replacement of open woodlands and savannas by dense forest, intensification of agriculture, and conversion of native grasslands to nonnative pastures have degraded habitats for most grassland and early successional birds. Declines in bobwhite and associated species occurred within this context at a scale that has overwhelmed wildlife management efforts. However, with understanding of scale and context, managers could sustain these species in some future landscapes. Increasing urbanization over the next century will result in loss of millions of acres of forests, grasslands, and agricultural lands used by bobwhite and associated species, and climate change will affect abundance and distribution of shortleaf (Pinus echinata), loblolly (P. taeda), and longleaf (P. palustris) pine woodlands. I highlight modeling tools and planning efforts that demonstrate how conservation planning can address these changes. I suggest that focusing management in the correct landscape contexts and accounting for land use and climate change is more likely to be successful than management that does not and conservation partnerships and management efforts across public and private lands are required to affect regional bobwhite populations

Anisotropic Gauss-Hermite Beam Model Applied to through-Transmission Inspections of Delaminations in Composite Plates

Manufactured parts containing composite materials can present challenging ultrasonic inspection problems. The inherent anisotropy of such materials acts to distort propagating ultrasonic beams, leading in turn to an associated distortion of defect images. Such distortions complicate the task of estimating the physical dimensions of a defect from its ultrasonic image. In the present work we demonstrate how these difficulties can be overcome by appropriately modelling the ultrasonic inspection process, and using the model to analyze defect images. To illustrate the approach, we consider a normal incidence through-transmission inspection of a flat uniaxial composite plate with an internal delamination. We begin by reviewing our model of the inspection process which incorporates the Gauss-Hermite model for beam propagation in anisotropic materials. The inspection model requires as inputs certain parameters which characterize the transducers, and others which characterize the composite material. We demonstrate how these parameters can be obtained from simple beam-mapping experiments. We then present experimental C-scan images of a seeded circular delamination in a composite plate, and compare these to images predicted by the model. Finally, we demonstrate how the model can be used to accurately size a delamination from its ultrasonic image

Ultrasonic NDE Techniques for Integrally Fabricated Rotors

Solid-state bonding methods, e.g., diffusion bonding and pressure welding, are becoming common manufacture and repair techniques for gas turbine engine components. Effective NDE inspection techniques are crucial to the utilization of this approach due to the high stresses on the bond plane associated with jet engine operation. Recently we have examined ultrasonic techniques for assessing bond quality including leaky Rayleigh waves and critical angle longitudinal waves[1], for which the illuminating waves are nearly normal to the bond plane, and longitudinal waves at near grazing incidence to the bond[1]. Based upon preliminary theoretical analyses[1,2] of ultrasonic reflectivity from imperfect interfaces, it was found that the reflection coefficient for both longitudinal and shear waves increases to unity as the incident angle approaches grazing[1]. In contrast, the bond reflection coefficients for near normal incidence can be quite small, depending upon the degree of imperfection of the bond. A second drawback to the first two approaches mentioned is that surface roughness of the blade can cause scattering noise which dominates the signals reflected from the bond. The grazing incidence technique suffers less from these problems since the probe is oriented nearly normal to the surface of the blade and the interaction of the beam with the surface is minimized