Browsing by Author "Ling, Chih B."

Now showing 1 - 5 of 5
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    Compressive strength of lamina reinforced and fiber reinforced composite materials
    Davis, John G. (Virginia Tech, 1973-05-15)
    Results are presented from a theoretical and experimental investigation on the compressive strength of lamina reinforced and fiber reinforced composite materials when loaded parallel to the reinforcement. An analytical model which replaces the fiber reinforced composite with a laminate containing initially curved laminae has been proposed. By applying the Timoshenko beam equations to each layer of the laminate, an interlaminar shear stress analysis which can be used to predict the behavior of the laminate under compressive loading was developed. Two modes of failure are considered in the analysis, delamination and shear instability, and nonlinear shear stress-strain behavior of the laminae is included. Axial compression tests were performed on aluminum-wax laminates, boron-epoxy tubes and S-glass-epoxy tubes. In addition, torsion tests and combined compression and torsion tests were conducted on the fiber reinforced tubes. Coordinates of fibers in a boron-epoxy laminate were measured. Experimental results indicate that the aluminum-wax laminates failed by delamination and that failure of the boron-epoxy composite in compression is most likely due to shear instabIlity. In addition it was shown that the shear modulus of boron-epoxy is a function of axial compressive stress and that the fibers in a boron-epoxy composite are not parallel but contain initial curvature. Adequate correlation between theory and experiment was obtained for both lamina and fiber reinforced test results.
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    Effect of compressibility, suction, and heat transfer on the nonparallel stability of boundary-layer flows
    El-Hady, Nabil M. (Virginia Tech, 1978-12-31)
    We present an analysis of the effects of heating, suction, and compressibility on the stability characteristics of boundary-layer flows within the framework of a complete nonparallel, linear, spatial stability theory. Included in the theory are disturbances due to velocity, Pressure, temperature, density, and transport properties as well as 'variations of the fluid properties with temperature. The method of multiple scales is used to account for the nonparallelism of the mean flow and equations are derived for the evolution of the disturbance amplitude and wave number vector.
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    Finite difference approach for predicting probabilistic life of a composite cylinder subjected to thermal random loads
    Con, Vu Ngoc (Virginia Tech, 1979-03-05)
    A long hollow cylinder with five layers, subjected to a random thermal environment is analyzed. The random thermal environment includes the ambient air temperature, solar radiation and wind speed. The location of interest is Phoenix, Arizona. The governing differential equation is the so-called one-dimensional Fourier heat conduction equation in cylindrical coordinates. An implicit finite difference scheme is developed to obtain temperature responses inside the cylinder. Given the linear elastic behavior of materials involved, induced stresses and strains are evaluated at the end of each time step of the finite difference scheme. A statistical analysis is then carried out to determine the probability of failure of the propellant and hence the service life of the motor can be computed.
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    On a point defect inside an idealized elastic sphere
    Ling, Chih B.; Houska, Charles R. (American Institute of Physics, 1983)
    This paper presents a method of solution for the displacement, stress, and strain due to a point defect located inside a sphere. The solution is represented by a Love stress function in spherical coordinates, which is biharmonic in character. Two axisymmetric types of the point defect are considered. One is treated as a center of dilatation and the other as a double force without moment, or a doublet, oriented axisymmetrically. The Love stress function for the point defect in an infinite solid is specified in each case by a single biharmonic function. The residual tractions on the surface of the sphere left by this function are annulled by superposing two series of biharmonic functions. When the Love stress function is determined, the displacement, stress, and strain can be derived straightforwardly.
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    The vibration of instrument ball bearings in a controlled environment and the effect of the resulting fretting corrosion on bearing torque
    Hite, Gregory Charles (Virginia Tech, 1970-08-05)
    Fretting corrosion is a form of wear which occurs at the interface of two contacting solid materials as the result of small, relative vibratory motion. It is generally identified by the presence of a red oxide, Fe203. Previously, the majority of the investigators studied the fretting corrosion between two flat specimens or between a single ball and a flat plate held in contact by a normal force. There are a number of interrelated influencing factors involved in fretting corrosion including: the vibration frequency and amplitude, the environmental conditions, the characteristics of the material, and the type of lubrication. The present investigation was conducted in order to investigate the effects of frequency and amplitude of axial vibration and the consequent accelerations acting to produce fretting damage within an unlubricated instrument ball bearing. The effect of bearing axial play on the fretting damage was also examined. The reproducibility of the damage resulting from these variables was determined.