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Call number: LD2668 .T4 1966 M648 / Master of Science

Literature reports have indicated that application of sonic pressure waves enhances the rate of impregnation of preservatives in wood. However, these studies have been limited and inconclusive. The technique or process is not in commercial use. In this study a laboratory scale treating cylinder connected to a mechanical sonic wave generator was used to measure the rate of impregnation of water in ponderosa pine at pressures of 0.28, 0.55 and 0.69 MPa and Douglas-fir at pressures of 0.55 and 0.69 MPa at a frequency of 30 Hz. Results were compared with those obtained at the same conditions of static hydraulic pressure. Statistical analysis showed that sonic treatments were at least as effective as, but not consistently superior to, hydraulic pressure treatments in the case of ponderosa pine. Statistical analysis of the results from Douglas-fir treatment showed that sonic treatment was superior than hydraulic treatment. / Graduation date: 1995

No description available.

A presentation is given of an acousto-ultrasonic system for the evaluation of composite materials. First, a brief statement will be made on the acousto-ultrasonic technique and its relative worth compared to other nondestructive testing techniques as applied to composite materials. The following two chapters describe the system instrumentation and system software, respectively. Next, comments are given regarding the implementation of the system for research on graphite/epoxy laminates, with additional remarks concerning efforts to evaluate aluminum/graphite tubes with the system. This includes physical descriptions of the composite systems. Subsequently, results are presented comparing parameters and forms of presentation which can be employed to relate results. Finally, conclusions are made on the application of the acousto-ultrasonic system to nondestructive testing of composite materials, with specific results on its application to graphite/epoxy plates. More specifically, comments are made on the variation of SWF factors with azimuthal angle on the graphite/epoxy plates, the identification of specific frequency peaks, and the relationships these may have to certain modes of vibration and material properties. For example, a low frequency mode was found to vary in a manner reminiscent of E_x and to show characteristics of an extensional Lamb wave. In general, results are presented and discussed in order to show how the system can be implemented to gain physical information on composite materials, such as the property of anisotropy. / Master of Science

This investigation was conducted to provide laboratory scale equipment that will facilitate an accurate study of the affect of ultrasonic energy on mass transfer in two-phase multiple-component liquid systems. A liquid-liquid extractor incorporating an ultrasonic generator and transducer was designed and constructed to the following specifications: (1) insonation frequency of 400 kilocycles per second, (2) insonation intensities equivalent to plate currents of 0 to 200 milliamperes, and (3) flow rate of solvent and feed through the reactor ranging approximately from one-half to 24 pounds per minute, in varying solvent-to-feed ratios. A special glass reactor, or contactor, was constructed from a standard, 60° pyrexx glass funnel and fitted with an acoustical window of 0.001-inch sheet nickel. Photographic studies were made of the two-phase mixing taking place inside the reactor in both the presence and absence of ultrasonic insonation. An all metal reactor, of the same general design as the glass reactor, was constructed for use with the extractor when investigations were to be made that would involve high pressures or sudden liquid surges through the reactor. An evaluation of the extractor was conducted employing the system moetons-water-1,1,2-trichloroethane. Stage efficiencies calculated for the individual tests, eleven in all, varied from 94.3 to 110.0 percent. An observed yellow color in the extract samples, probably due to dissolved impurities in the 1,1,2-trichloroethane, could have been responsible for the observation of refractive index readings that did not give true representation of the acetone concentration of the sample. Cavitation was observed in the reactor which the test system was undergoing ultrasonic insonation. The gross stirring effects resulting from cavitation in the liquids caused a mixing of the two phases that was more intense than that taking place in the reactor without insonation. / Master of Science

A basic physical explanation, a model, and comments on NDE application of the acoustoultrasonic method for composite materials are presented. The basis of this work is a set of experiments where a sending and a receiving piezoelectric transducer were both oriented normal to the surface, at different points, on aluminum plates, various composite plates, and a tapered aluminum plate. Chapter one introduces the purpose and basic idea of the dissertation, while supporting its need. Also, general comments on the AU method are offered. The second chapter offers a literature review of areas pertinent to the dissertation, such as composite materials, wave propagation, ultrasonics, and the AU method. Special emphasis is given to theory which is used later on and past experimental results that are important to the physical understanding of the AU method. The third chapter describes the experimental set-up, procedure, and the ensuing analysis. In the fourth chapter, the experimental results are presented in both a quantitative and qualitative manner. Chapter five furnishes a physical understanding of experimental results based on elasticity solutions, Lamb wave theory, and through-the-thickness-transverse·resonance (TTTR). Computer results are presented for sake of comparison. The sixth chapter discusses modeling and applications of the AU method for composite materials and the seventh chapter states general conclusions. The unique offering of this work is the physical model of the AU method for composite materials, something which has been much needed and sorely lacking. This physical understanding is possible due to the extensive set of experimental measurements, also reported in this dissertation. / Ph. D.

Digitized by Kansas Correctional Industries

Heterogeneities in concrete caused by the random distribution of aggregate in the cement-paste matrix lead to strong scattering of ultrasound waves at wavelengths on the order of the aggregate. Use of these high frequencies is necessary to detect damage at an early stage, something that is not possible with conventional ultrasonic methods. The ultrasound energy density in this regime can be described by the diffusion equation. The objective of this research is to develop a quantitative understanding of the effects of additional scattering sources, such as small cracks in the cement-paste matrix, on the parameters of the diffusion equation; these parameters are the diffusion and the dissipation coefficients. Experimentally measured ultrasonic waves are processed using the diffusion theory to determine the diffusivity and the dissipation coefficients as a function of frequency. The samples employed are made of a Portland cement-paste matrix and regular aggregate such as gravel and sand. The results provide a basic understanding of the repeatability and consistency of diffusion measurements, with an emphasis on the nondestructive evaluation of damage in concrete. In addition, a method to describe concrete in the coherent regime is examined. Existing wave propagation models for inhomogeneous materials deal with two-phase mixtures, mostly the matrix-inclusion system such as fiber-reinforced composites. There are, however, numerous examples of multi-phase materials in which more than one phase is suspended in a matrix-phase. This research considers concrete, in which cement paste and aggregates with different sizes and mechanical properties are mixed together. Most of the models for two-phase composites cannot be extended to a multi-phase composite. Among others, the effective medium theory is considered here for two reasons: first, the formalism in this theory can easily be extended to multi-phase cases; second, the theory does not strictly define a specific microstructure between phases, which allows for a simulation of the microstructure in which different inclusions are in contact. The mathematical formulation is presented that yields the formulae for the effective density and the effective bulk and shear moduli. Finally, the calculated wave speeds and attenuations for different materials are compared with experimental results.

Material damage such as dislocations and microcracks are characteristic of early stages of fatigue. Accumulation of these nascent cracks leads to non-linear elastic response of the material. These non-linearities can be detected from harmonic generation for propagating elastic waves. The long term goal of this study is to investigate the non-linear elastic propagation in parts with complex geometry. Cellular Automata is introduced as a new simulation method, in order to develop new analysis on quadratic non-linearities. An existing linear code was progressively modified to take into account a different constitutive law. Also the boundary conditions need to be reviewed to ensure free stress with the non-linear behavior. The propagation of the longitudinal wave is investigated in detail. Numerical accuracy is validated from comparison with a closed, for both linear and non-linear code. The reflection of the non-linear P-wave gives confirmation for the correct treatment of the boundary condition. Finally the capabilities of the Cellular Automata code are underlined for reflection of Lamb waves for various boundary conditions.