Lattice vibrations and atomic level elastic moduli have been studied for a bicrystal containing a fully relaxed symmetrical tilt boundary in Au. Central force many body potentials have been employed to describe atomic...
Lattice vibrations and atomic level elastic moduli have been studied for a bicrystal containing a fully relaxed symmetrical tilt boundary in Au. Central force many body potentials have been employed to describe atomic interactions. In the long-wavelength limit the phonons localized at grain boundaries can be identified with Stoneley waves known from continuum analyses. These waves are localized at the grain boundary and their velocity agrees well with that evaluated using the local effective elastic moduli of the interfacial region. However, the usually used continuum model assuming an ideal match across the interface is not sufficient to analyze these waves fully and an explicit description of interfacial properties need to be included into the continuum models of interfaces.
The problem of crack growth along the interface of two immiscible homopolymers is studied where the interface is strengthened by the addition of a small amount of diblock copolymer. A micromechanical model of the inte...
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The problem of crack growth along the interface of two immiscible homopolymers is studied where the interface is strengthened by the addition of a small amount of diblock copolymer. A micromechanical model of the interface is proposed and a time-dependent Dugdale-Barenblatt model based on this model is used to predict the fracture toughness of the interface as a function of the applied loading, the crack growth rate and the underlying interface properties.
In the examination of glass-reinforced plastic (GRP) pipes and components after failure the fracture is often so catastrophic that much of the evidence is destroyed or hidden. When a leak failure occurred during a hyd...
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In the examination of glass-reinforced plastic (GRP) pipes and components after failure the fracture is often so catastrophic that much of the evidence is destroyed or hidden. When a leak failure occurred during a hydraulic pressure test on a GRP pipe bend the opportunity was taken to examine the bend wall in detail at a number of localities. They included, not only the region where the leak was apparent but also at areas where strain and displacement measurements had indicated the possibility of failure arising. The 250 mm diameter pipe specimen tested consisted of a right-angled pipe bend with flanged, straight lengths each attached by a butt joint. The resin matrix was polyester and the reinforcement was E-glass in the form of chopped strand mat of four layers weighing 2.4 kg/m2. Although the failure pressure was entirely satisfactory from a design point of view, three important areas of weakness were discovered. They were associated with procedures for butt jointing and for moulding of the bend unit. The resulting micrographs were of sufficient quality to act as comparators for examination of possible service failures.
Consolidation of rapidly solidified titanium aluminide (Ti3Al) powders employing explosive shock pressure followed by hot isostatic pressing ("hipping") was carried out successfully. Shock densification was ...
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OSTENDORF, DWLEACH, LEHINLEIN, ESXIE, YF1 David W. Ostendorf is an associate professor in the Environmental Engineering Program of the Civil Engineering Department at the University of Massachusetts (Civil Engineering Department
University of Massachusetts Amherst MA 01003). His research interests include unconfined aquifer contamination hazardous waste site remediation and analytical modeling of problems in environmental fluid mechanics. Dr. Ostendorf is a registered professional engineer in Massachusetts and a member of the American Geophysical Union American Society of Civil Engineers Soil Science Society of America Water Pollution Control Federation and Association of Environmental Engineering Professors as well as the National Water Well Association.2 Lowell E. Leach is an environmental engineer with the Robert S. Kerr Environmental Research Laboratory of the U.S. Environmental Protection Agency (RS Kerr Environmental Research Laboratory U.S. EPA P.O. Box 1198 Ada OK74820). Leach received his B.S. ingeological engineering at the University of Oklahoma in 1959 and has been a registered professional engineer in Oklahoma since 1966. With 29 years of experience in field applications of geological engineering he is responsible for developing methodology for sampling ground water and subsurface materials for the Robert S. Kerr Environmental Research Laboratory.3 Erich S. Hinlein is a research assistant in the Environmental Engineering Program of the Civil Engineering Department at the University of Massachusetts (Civil Engineering Department University of Massachusetts Amherst MA 01003). His research interests include ground water pollution hazardous waste site investigation and transport processes in unconfined aquifers. Hinlein graduated with a B.S. in electrical and computer engineering from the University of Massachusetts at Amherst in May 1985 and entered the Environmental Engineering Master's Degree Program in January 1989.4 Yuefeng Xie is a postdoctoral research associate in the Environmental Engineering Program of the Civil E
Two complementary field sampling methods for the determination of residual aviation gasoline content in the contaminated capillary fringe of a fine, uniform, sandy soil were investigated. The first method featured fie...
Two complementary field sampling methods for the determination of residual aviation gasoline content in the contaminated capillary fringe of a fine, uniform, sandy soil were investigated. The first method featured field extrusion of core barrels into pint-size Mason jars, while the second consisted of laboratory partitioning of intact stainless steel core sleeves. The barrel extrusion procedure involved jar headspace sampling in a nitrogen-filled glove box, which delineated the 0.7m thick residually contaminated interval for subsequent core sleeve withdrawal from adjacent boreholes. Soil samples removed from the Mason jars (in the field) and sleeve segments (in the laboratory) were subjected to methylene chloride extraction and gas chromatographic analysis to compare their aviation gasoline content. The barrel extrusion sampling method yielded a vertical profile with 0.10m resolution over an essentially continuous 5.0m interval from the ground surface to the water table. The sleeve segment alternative yielded a more resolved 0.03m vertical profile over a shorter 0.8m interval through the capillary fringe. The two methods delivered precise estimates of the vertically integrated mass of aviation gasoline at a given horizontal location, and a consistent view of the vertical profile as well. In the latter regard, a 0.2m thick lens of maximum contamination was found in the center of the capillary fringe, where moisture filled all voids smaller than the mean pore size. The maximum peak was resolved by the core sleeve data, but was partially obscured by the barrel extrusion observations, so that replicate barrels or a half-pint Mason jar size should be considered for data supporting vertical transport analyses in the absence of sleeve partitions.
The authors review the basic theory governing the existence of exceptional bulk waves which propagate in an infinite anisotropic elastic medium while leaving a family of parallel planes traction-free. A solution schem...
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Characteristics of both thermoplastic and thermoset composite materials as they pertain to marine vehicle applications are discussed. Comparison of various material selection factors such as strength, damage and moist...
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Characteristics of both thermoplastic and thermoset composite materials as they pertain to marine vehicle applications are discussed. Comparison of various material selection factors such as strength, damage and moisture resistance, and flammability and toxicity as well as cost and availability of thermoset and thermoplastic composite materials are presented. Methods for testing and reducing the flammability and toxicity are discussed. Many commercially available composite systems are reported to provide favorable characteristics for marine applications. Although there seems to be a need for improved production technology for thermoplastics, they present potential advantages in physical properties over thermoset composites.
Point and space group analysis of large T 1 (Al 2CuLi) crystals was performed by convergent beam electron diffraction. The structure of T 1 was determined to be hexagonal, possessing a 6/mmm point group and P6/mmm (No...
Large T 2 (Al 6Li 3Cu) crystals which display apparent five-fold symmetry have been studied using several different electron microscopy techniques. Electron microprobe X-ray analysis was used to determine the phases p...
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