T. Quick

Magnesium-salinity relation in the saline lake ostracode Cyprideis americana

Magnesium concentration in the carapace of live specimens of the euryhaline ostracode Cyprideis americana from lakes of varying salinity on San Salvador Island, Bahamas, is inversely related to salinity. Temperature exerts little if any control of Mg content over the range observed. Magnesium concentration in well-preserved fossil specimens of C. americana reveal paleosalinities in close agreement with results obtained from fossil ostracode assemblages, apparent sea-level-salinity relations, and sedimentological observations.

Iron transformations induced by an acid-tolerant Desulfosporosinus species.

ABSTRACT The mineralogical transformations of Fe phases induced by an acid-tolerant, Fe(III)- and sulfate-reducing bacterium, Desulfosporosinus sp. strain GBSRB4.2 were evaluated under geochemical conditions associated with acid mine drainage-impacted systems (i.e., low pH and high Fe concentrations). X-ray powder diffractometry coupled with magnetic analysis by first-order reversal curve diagrams were used to evaluate mineral phases produced by GBSRB4.2 in media containing different ratios of Fe(II) and Fe(III). In medium containing Fe predominately in the +II oxidation state, ferrimagnetic, single-domain greigite (Fe3S4) was formed, but the addition of Fe(III) inhibited greigite formation. In media that contained abundant Fe(III) [as schwertmannite; Fe8O8(OH)6SO4 · nH2O], the activities of strain GBSRB4.2 enhanced the transformation of schwertmannite to goethite (α-FeOOH), due to the increased pH and Fe(II) concentrations that resulted from the activities of GBSRB4.2.

Controlled Release Temephos: Laboratory and Field Evaluations

The development of controlled-release pesticides based upon the monolithic dispersion of a chemical agent in a polymer has been described in detail elsewhere.1 Temephos, 0,0,0’,0’-tetramethyl-0,0-thiodi-p-phenylene phosphorothioate (C.A. Registry #3383–96–8), was incorporated in elastomeric matrices and a diffusion-dissolution type release mechanism was established.2 Although a continuous release of the agent occurred for over three years, commercialization was not undertaken. Later it was discovered that long-term toxicant release from a plastic matrix could be achieved through a leaching process keyed to the use of a water-soluble additive whose emission led to the development of the necessary porosity in the matrix.3 The processing costs for such materials are relatively inexpensive, and consequently a number of controlled-release temephos materials are now commercially available. Unlike conventional formulations which are limited to solutions, emulsions, granules, and wettable powders, controlled-release plastic dispensers can be manufactured in any geometry conducive to the particular environment to be treated.

Mechanical Behavior of Two High Strength Alloy Steels Under Conditions of Cyclic Tension

The results of a recent study aimed at understanding the conjoint influence of load ratio and microstructure on the high cycle fatigue properties and resultant fracture behavior of two high strength alloy steels is presented and discussed. Both the chosen alloy steels, i.e., 300M and Tenax™ 310 have much better strength and ductility properties to offer in comparison with the other competing high strength steels having near similar chemical composition. Test specimens were precision machined from the as-provided stock of each steel. The machined specimens were deformed in both uniaxial tension and cyclic fatigue under conditions of stress control. The test specimens of each alloy steel were cyclically deformed over a range of maximum stress at two different load ratios and the number of cycles to failure recorded. The specific influence of load ratio on cyclic fatigue life is presented and discussed keeping in mind the maximum stress used during cyclic deformation. The fatigue fracture surfaces were examined in a scanning electron microscope to establish the macroscopic mode and to concurrently characterize the intrinsic features on the fracture surface. The conjoint influence of nature of loading, maximum stress, and microstructure on cyclic fatigue life is discussed.

The Quasi-static Deformation, Failure, and Fracture Behavior of Titanium Alloy Gusset Plates Containing Bolt Holes

In this article, the influence of bolt holes, specifically their number and layout on strength, deformation, and final fracture behavior of titanium alloy gusset plates under the influence of an external load is presented and discussed. Several plates having differences in both the number and layout of the bolt holes were precision machined and then deformed under quasi-static loading. The specific influence of number of bolt holes and their layout on maximum load-carrying capability and even fracture load was determined. The conjoint influence of bolt number, bolt layout pattern, nature of loading, contribution from local stress concentration, and intrinsic microstructural effects in governing the macroscopic fracture mode and intrinsic microscopic mechanisms is presented and discussed.

Quasi‐Static, Fatigue and Fracture Behavior of Aluminum Alloy Composite Used in Brake Drums

In this paper the results of a study aimed at investigating and understanding the quasi-static, cyclic fatigue properties and final fracture behavior of an aluminum alloy reinforced with particulates of ceramic, a viable candidate for use in brake drums of emerging automobiles, is highlighted. The processing treatment used to engineer the aluminum alloy composite is detailed. Specimens of both the aluminum composite and the preform that was used to engineer the composite were deformed in both tension and cyclic fatigue over a range of maximum stress in the room temperature, laboratory air environment and the number of cycles-to-failure was recorded. The stress-fatigue life response of the aluminum alloy composite is compared with the preform. Both the quasi-static and cyclic fatigue fracture surfaces of the deformed and failed samples were comprehensively examined in a scanning electron microscope to reveal the macroscopic fracture mode and to concurrently characterize the intrinsic features on the fracture surfaces.

The Stress Controlled Cyclic Fatigue and Fracture Behavior of Alloy Steel 300M

In this manuscript the results of a study aimed at understanding the extrinsic influence of test specimen orientation, with respect to wrought alloy steel plate, on high cycle fatigue properties and fracture behavior is highlighted. The alloy steel chosen was 300 M. Samples of this alloy steel prepared from both the longitudinal and transverse orientation were cyclically deformed over a range of maximum stress and the corresponding number of cycles to failure (NF) was recorded. The influence of test specimen orientation and intrinsic microstructural effects on cyclic fatigue life is presented. At the chosen test temperature, the macroscopic fracture mode was essentially identical regardless of the orientation of the test specimen with respect to the wrought plate. The microscopic mechanisms governing cyclic deformation, fatigue life and final fracture behavior is presented in light of the mutually interactive influences of magnitude of applied stress, intrinsic microstructural effects, orientation of test specimen, and deformation characteristics of the constituents in the microstructure of this alloy steel.

Investigating and Understanding the Bending Fatigue Response and Fracture Behavior of Two High Strength Steels

In this paper, the results of a recent study aimed at understanding the bending fatigue response of two carbon steels is presented and discussed. The two carbon steels chosen are the ones preferred and used for a spectrum of industrial applications. Bend test specimens of the two carbon steels were prepared and conformed to specifications used in several earlier studies. The machined test specimens were deformed in bending fatigue over a range of maximum load, at a positive load ratio of 0.1, and the number of cycles to failure was recorded. The specific influence of chemical composition on bending fatigue life of the carbon steels is presented. The fracture surfaces of the deformed and failed specimens were examined in a scanning electron microscope to establish the macroscopic mode of fracture and to concurrently characterize the intrinsic features and establish the microscopic mechanisms governing fracture. The influence of nature of loading and maximum load on bending fatigue life is discussed in light of chemical composition and intrinsic microstructural features of the chosen carbon steel.

The High Cycle Fatigue and Final Fracture Behavior of Alloy Steel 9310 for Use in Performance-Sensitive Applications

In this technical paper the results of a recent study aimed at understanding the high cycle fatigue properties and fracture behavior of an alloy steel, a viable candidate for use in performance-critical applications, is presented and briefly discussed. The alloy steel investigated was 9310. The material was evaluated in the as-forged (wrought) and normalized condition. Test specimens of this alloy steel were precision machined and conformed to specifications delineated in the ASTM E8. The as-machined and subsequently polished test samples were cyclically deformed over a range of maximum stress, in the room temperature (T = 25 C), laboratory air environment (Relative Humidity 55 pct), at the load ratios of 0.1 and -1.0. The number of cycles-to-failure was recorded. The specific significance of load ratio on cyclic fatigue life of alloy steel 9310 is presented and differences discussed based on a synergism of the nature of loading, intrinsic microstructural effects, and macroscopic fracture behavior. The fatigue fracture surfaces were examined in a scanning electron microscope to determine the macroscopic fracture mode and to concurrently characterize the intrinsic features on the fatigue fracture surfaces and thus establish the microscopic mechanisms governing failure. The conjoint influence of microstructure, maximum stress and load ratio on cyclic fatigue life and fracture behavior is highlighted.