Papers by Salahuddin Ahmed
Effects of Layer Properties on the Ultrasonic Resonance of Composite Spheres
AIP Conference Proceedings
The efficient calculation of the resonance frequencies is required for the effective application ... more The efficient calculation of the resonance frequencies is required for the effective application of resonant ultrasound spectroscopy (RUS) to determine the relevant properties of an elastic object. If a suitable number of the resonance frequencies of an elastic object are known, in principle, one can deduce a number of its physical properties like elastic constants, density, dimensions, shape, etc. However, general analytic expressions are not available for the normal mode free vibrations of a body with arbitrary shape and elastic properties. It was noticed by Holland and Demarest (1971) that a simple variational principle can be applied to compute the normal mode frequencies of an elastic body with free boundaries. Based on this variational method, Visscher et al. (1991) developed the XYZ algorithm which can be applied to compute the resonance frequencies of a body with arbitrary shape and elastic properties. Since layered systems are finding increasing use in engineering applications, computational studies are being carried out to investigate the suitability of RUS as an NDE technique to determine imperfections in a layered system. Specifically, the normal mode frequencies of a four-layered sphere are computed by the XYZ algorithm. It will be shown that the deviations from specified layer properties cause noticeable shifts on the resonant frequencies.
Review of Progress in Quantitative Nondestructive Evaluation
Ultrasonic Attenuation as Influenced by Elongated Grains
AIP Conference Proceedings
Reliable nondestructive evaluation of structural/machine components fabricated from polycrystalli... more Reliable nondestructive evaluation of structural/machine components fabricated from polycrystalline materials require the knowledge of attenuation and dispersion of an ultrasonic wave propagating through such microscopically inhomogeneous medium. ...
AIP Conference Proceedings
An ultrasonic wave propagating through a microscopically inhomogeneous medium, such as polycrysta... more An ultrasonic wave propagating through a microscopically inhomogeneous medium, such as polycrystalline materials, is subject to scattering at the grain boundaries. The fraction of energy removed from the incident wave is responsible for important phenomenon like attenuation, dispersion, and background "noise" associated with a given ultrasonic inspection system. Since the backscattered signals tend to mask the signals from small and subtle defects, the estimation of probability of detection of such defects requires the quantitative description of these signals. Although considerable attention has been given to the understanding of mean propagation characteristics of an ultrasonic beam, until recently there have been relatively little efforts devoted towards rigorous treatments of backscattered signals. In this research, we attempt to include some degree of multiple scattering in the calculation of the backscattered signals by developing a formalism that relates mean wave propagation characteristics to the noise.
Ultrasonic beam fluctuation and flaw signal variance in inhomogeneous media
AIP Conference Proceedings
Inversion of Ultrasonic Attenuation for Textural Information of Polycrystals
Description/Abstract The mechanical properties of polycrystalline materials depend on the individ... more Description/Abstract The mechanical properties of polycrystalline materials depend on the individual physical properties of the constituent grains. When grains are randomly oriented with respect to a fixed coordinate system, the average elastic properties are isotropic. A ...
Attenuation of Ultrasonic Waves in Cubic Metals Having Elongated, Oriented Grains
Http Dx Doi Org 10 1080 10589759208952729, Nov 28, 2010
Rapid, on-line determination of particle size and concentration is required for the efficient pro... more Rapid, on-line determination of particle size and concentration is required for the efficient process measurement and control of many processes in government and industrial applications such as waste remediation for the Department of Energy sites and process control for chemical and pharmaceutical manufacturing. However, existing methods based on ultrasonic attenuation can become inaccurate for highly concentrated suspensions due to careful transducer alignment and the complicated mathematics required to describe multiple scattering, which controls the attenuation. Two measurements that help to overcome these difficulties are the ultrasonic backscattering and diffuse field. Backscattering is attractive because the single scattering theories typically used to describe backscattering are mathematically simpler than attenuation theories and lend themselves to more stable inversion processes. Also, the measurements of backscattering and diffuse fields do not require long travel distances and can be made with a single transducer thus eliminating alignment problems. We will present ultrasonic measurements on solid liquid suspensions designed to elucidate the particle size and concentration at high concentrations.
Sonoluminescence and multi-bubble cavitation phenomena for selected research and industrial applications
Journal of The Acoustical Society of America, 2003
Single bubble sonoluminescence (SBSL), multi-bubble sonoluminescence (MBSL), multi-bubble sonoche... more Single bubble sonoluminescence (SBSL), multi-bubble sonoluminescence (MBSL), multi-bubble sonochemiluminescence (MBSCL) and other high power ultrasound cavitation and noncavitating ultrasound process stream interaction phenomena are known to produce a wide range of both physical and chemical effects that depend upon the system and operating conditions employed. Three interacting regimes are under investigation (a) high power and high frequency (including noncavitating systems),
Effect of preferred grain orientation and grain elongation on ultrasonic wave propagation in stainless steel
Review of Progress in Quantitative Nondestructive Evaluation Vol 11b, 1992
Using Scattering Theory to Determine Orientation Distribution Coefficients of Polycrystals with Preferred Grain Orientations
Description/Abstract The mechanical behavior of single-phase polycrystalline materials depend on ... more Description/Abstract The mechanical behavior of single-phase polycrystalline materials depend on the elastic constants of individual grains. Most engineering metals are polycrystalline aggregates possess macroscopic texture resulting from preferential grain ...
Proceedings of the 20th IEEE Instrumentation Technology Conference (Cat. No.03CH37412), 2003
Computation of Two-Dimensional Incompressible Turbulent Boundary Layer Flows with Equilibrium and Nonequilibrium Turbulence Models
International Journal of Modern Physics C, 1994
Two-dimensional incompressible turbulent boundary layer flows over a flat plate were predicted us... more Two-dimensional incompressible turbulent boundary layer flows over a flat plate were predicted using turbulent boundary layer equations. Reynolds stresses were calculated using Cebeci-Smith, Baldwin-Lomax, and Johnson-King eddy viscosity models. Computational results of mean-flow properties based on Cebeci-Smith model and Baldwin-Lomax model are in excellent agreement with experimental data, and, those based on Johnson-King model are not as accurate as the other two models.
One of the tasks of the U.S. Nuclear Regulatory Commission-sponsored project titled "Reliability ... more One of the tasks of the U.S. Nuclear Regulatory Commission-sponsored project titled "Reliability of Nondestructive Examination (NDE) for Nuclear Power Plant (NPP) Inservice Examination (ISI)" is to provide collaborative assistance to Commissariat à l'Energie Atomique (CEA) in France through theoretical predictions of ultrasonic scattering by grains of cast stainless steels (CASS) components. More specifically, a mathematical treatment of ultrasonic scattering in media having duplex microstructure is sought because cast stainless steel components often contains larger-scale macrograins that are composed of sub-grains/colonies.
The goal of this proposed work is to directly address the need for rapid on-line characterization... more The goal of this proposed work is to directly address the need for rapid on-line characterization of the physical properties of HLW slurries during all phases of the remediation process, from in-tank characterization of sediments to monitoring of the concentration, particle size, and degree of agglomeration and gelation of slurries during transport. This will be done with both optical and ultrasonic methods. There are three tasks: 1) develop optical and acoustic measurements to provide the fundamental science needed for successful device development and implementation, 2) develop theories that describe the interrelationship between wave propagation and the physical properties of the slurry, and 3) solve, in the framework of these theories, the inversion problem and compare them with the experimental measurements to non-intrusively characterize slurries. Research Progress and Implications The optical measurements are based on the investigation of slurries with Optical Low-Coherence Reflectometry (OLCR). OLCR is a white-light interferometric technique that incorporates a broadband light source with a classical Michelson
Modeling of resonant ultrasound spectroscopy based nondestructive evaluation using the xyz-algorithm
Proceedings of the Interntional Congress on Ultrasonics, 2007
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Papers by Salahuddin Ahmed