home bibliography educational materials
Ultrasound Material Characterization
Powder Coated Metal Plate Characterization
The aim of this study was to establish a relationship between the mechanical properties of a powder coating, extracted using ultrasonic analyses, and the extent of its curing. This study was necessitated by the fact that most current methods either focus on in-process temperature monitoring or on laboratory analysis of powder samples and not on post-curing characterization of industrial samples. Working towards the objective the study involved investigating powder coating films by employing transmission mode ultrasound involving multiple reflections to extract the dimensionless material descriptor, tan(δ). It has been demonstrated that trends observed in the mechanical properties of the coatings extracted by processing the ultrasonic signal corresponded to those experimentally extracted using mechanical testing. Results are shown in Figure 1 for three different curing times.

Figure 1
Fig. 1 Multispectral tan(δ) in film (Multiple reflections).

Geopolymeric Material Characterization
This project is conducted in collaboration with Dr. Benjamin Varela in the Mechanical Engineering Department. Current methods of determining the elastic modulus and Poisson's ratio for geopolymeric materials are limited by the destructive nature of compressive strength and bending testing analysis techniques. Since these tests are not repeatable, there is no means of evaluating whether measured properties are a result of the actual materials or the effect of possible mechanical defects. This study applies a relationship between the speed of sound through a material and its elastic properties to determine the elastic modulus and Poisson's ratio of geopolymeric samples. In addition to these elastic properties, the density, percent pore volume, average pore diameter and standard deviation of pore diameter were also evaluated. These material characteristics were determined as a relationship to the Si:Al ratio of sodium activated metakaolin based geopolymers with Si:Al ranging from 1.49 to 6.4. It was found that lower Si:Al values were consistently around 8.5 GPa in samples above 3.1 Si:Al ratio. The Poisson's ratio for each sample decreased proportionally to the Si:Al ratio with a maximum value of 0.22 and a minimum value of 0.05.

Scattering Anisotropy Effect on Nerve Images
The objective of this research is to design a rigorous method to characterize nerve fibers using an ultrasound imaging system. This will allow successful application of regional anesthesia, which is safer and has fewer complications than general anesthesia, particularly in elderly and obese patients. Nerves are not always aligned parallel to the surface of the skin making them challenging to detect. The intensity and appearance of nerves in B-scan images varies with viewing angle. Using a tissue phantom and a high frequency 15Mhz transducer our goal is to define the relationship between the signal from the nerve and viewing angle. If a relationship can be developed, tracking of the nerves and correction of B-scan images can be implemented in software.