Uniform TitleUltrasonic nondestructive evaluation of armor ceramics
NameBrennan, Raymond (author), Haber, Richard (chair), Niesz, Dale (internal member), Sigel, George (internal member), McCauley, James (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectCeramic and Materials Science and Engineering,
DescriptionCeramic materials have been incorporated into armor systems to reduce their weight while providing high hardness, strength, and elastic response to stress. However, the presence of defects and flaws in armor ceramics can lead to ballistic failure. Nondestructive evaluation (NDE) techniques have been studied to locate and characterize defects and inhomogeneities in these materials.
High frequency ultrasound NDE has been explored for detecting and locating micron-range defects and identifying microstructural changes in dense armor ceramics such as silicon carbide (SiC). Ultrasound parameters such as transducer frequency have been analyzed to determine system conditions necessary for obtaining C-scan image maps based on differences in intensity of the collected ultrasound signals (reflected signal amplitudes) or transit time of ultrasound energy through materials (time-of-flight TOF). While TOF has have been used to evaluate changes in thickness, velocity, density, and acoustic impedance, reflected signal amplitude has been used to analyze attenuation, or loss, through a test specimen. Reflected signal amplitude and TOF C-scan imaging have been useful for identifying and locating isolated defects and microstructural differences. Elastic property maps have been developed to plot differences in Poisson's ratio, elastic modulus, shear modulus, and bulk modulus.
Quantitative analysis techniques have been used to evaluate cumulative effects of reflected signal amplitude and TOF changes over scanned regions and their distributions over selected areas. Amplitude and TOF histogram curves, which have been characterized by area-under-the-curve values, full-width at half-maximum values, and critical tail regions, have provided a valuable means of sample comparison. Generally, more narrow distributions of amplitude and TOF values have corresponded to high density armor-grade samples, while broad distributions have indicated defects or inhomogeneous regions in the samples. In addition to developing techniques for determining individual defect size distributions within a bulk specimen, histogram simulations have been explored to study amplitude and TOF distribution trends by analyzing how the addition of defects of varying size, quantity, and acoustic impedance affect histogram characteristics. These data have been utilized to establish a representative materials fingerprint that provides defect input data which can be further quantified and applied to property, design, and performance modeling of armor ceramic materials.
NoteIncludes bibliographical references (p. 494-501).
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.