The effect of angle on dovetail fretting experiments in Ti-6Al-4V

The objective of this work was to compare the fretting fatigue performance of Ti‐6Al‐4V dovetail specimens on Ti‐6Al‐4V pads having various contact angles typical of engine hardware; 35°, 45° and 55° dovetail angles were considered. The dovetail fixtures were instrumented with strain gages so that the local normal and shear contact forces could be calculated. The contact force hysteresis loops were recorded showing the stick‐slip history. At R= 0.1, gross slip was observed for several thousand cycles followed by partial slip after the average coefficient of friction increased. At R= 0.5, gross slip was present only during the first half cycle. During partial slip, the slope of the shear versus normal force was a function of the dovetail angle. The local contact loads, therefore, differed for the same remotely applied force. Despite this, the fretting fatigue life depended primarily on the remotely applied load not dovetail angle.     

CASE-BASED REASONING IN ENVIRONMENTAL MONITORING APPLICATIONS

Environmental monitoring is usually based on large volumes of data, while in general, environmental decision making is a complex problem, has a high degree of uncertainty, and involves diverse areas of expertise. Environmental decision-support systems are therefore good candidates for application of artificial intelligence (AI) techniques. In this paper it is argued that a suitable approach for building these systems is the use of case-based reasoning or analogical reasoning techniques, which offer more adaptability and better explanation facilities than other AI paradigms. As an example, the development stages, the architecture, and the operational characteristics of the expert system Air Quality Predictor (AIRQUAP), developed to predict air pollution levels in Athens, Greece, are described. AIRQUAP helps users retrieve historical data intelligently and can predict air pollution levels, useful for management of air pollution episodes. The performance of the system is also compared with other techniques used in this class of applications.     

Large-Deflection Solution of the Coaxial-Ring-Circular-Glass-Plate Flexure Problem

Nonlinear deflections and radial surface stresses in thin elastic circular plates laterally deformed into symmetrical concave shapes are analyzed. The deformations are induced by loading each plate with a small center ring while the plate is resting on a ring of nearly the same diameter as the plate. The rings and plate are coaxial, i.e. concentric. Center deflections up to 3 and 4.5 times the plate thickness were predicted for ring-diameter ratios of 0.5 and 0.2, respectively. The predicted deflection profiles at various loads agreed quite well with those which were determined experimentally on a chemically strengthened glass plate. This analysis provides a new criterion for using the coaxial-ring loading method for flexural strength testing of brittle materials.     

Optimized HREM imaging of objects supported by amorphous substrates using spherical aberration adjustment

High Resolution Electron Microscopy (HREM) is often used to characterize objects supported by amorphous substrates, usually amorphous carbon. HREM is currently undergoing step change in performance due to aberration correctors. This paper examines the aberration corrected imaging of objects supported by amorphous substrates. In particular, we show that a substantial increase in the ratio of the object contrast to the substrate contrast can be achieved by utilizing the strong variation of phase contrast with height, which is present when the spherical aberration has been adjusted to a small value. This variation is examined using the familiar Weak Phase Object Approximation model from which it is determined that the contrast ratio achieves a maximum at a small nonzero value of the spherical aberration. This result is confirmed by multislice modelling which allows for deviations from the Weak Phase Object Approximation and delocalization effects. One important practical result of this study is the need to place the object of interest on the correct side of the amorphous carbon substrate.     

REGIME APPROACHES TO OBSCENITY POLICY: 1960s to 1980s

ABSTRACT: During the 1970s, the governing regimes of both Chicago and Seattle were confronted by sharp increases in the number of adult movie theaters, particularly in their central business districts. Since the traditional means of suppressing such businesses had been declared unconstitutional, these regimes were forced to derive new obscenity policies. The central concern of the Chicago regime was to construct policies that would prevent any further economic deterioration of the downtown Loop. Toward this end, the Chicago regime utilized legal harassment, changes in land use ordinances, and property development to force adult theaters from the Loop. The Seattle regime was less concerned about downtown development than with mollifying its traditional constituency in the residential neighborhoods. Thus, the Seattle regime created a policy that concentrated adult establishments downtown. Ultimately, both regimes were successful in achieving their separate policy goals.     

Raman Spectroscopy of Higher Titanate Phases in the BaTiO3-TiO2 System

Polytitanates in the BaO-TiO₂ system with Ba: Ti ratios ranging from 1:2 to 1:5 were prepared employing the liquid mix technique. The samples were heated at 600° to 1300°C in oxygen, and Raman spectroscopy was used to investigate the phase relations in the system. The powders of various compounds were amorphous at temperatures less than 600°C. They crystallized into a single phase or a mixture of phases at 700°C. These mixtures underwent further phase transformation at higher temperatures to form single-phase compounds. Details of the procedure for sample preparation and characterization of the products are described. The results from the present study are compared with previously published data.