Lubricant evaluation of the alpha and beta joints, phase 2

A research study was conducted to evaluate dry film lubrication of long life space components such as the alpha and beta joints of the Space Station. The problem addressed in the report pertains to the longevity of sputtered MoS2 or ion plated lead films in a rolling contact environment. A special technique was devised for the experiments, which incorporated a coated ball cyclically loaded against a flat plate. At fixed intervals the surface of the coating was photographed at 100X magnification. By computer scanning the photographs, the rate of coating loss was determined. Experimental variables include load and surface finish of the plate. A theory was developed to analyze the state of stress between ball and flat. The stress condition in the ball apparatus was related to the state of stress under rolling contact conditions. Based on the experiments life appeared to decrease with increasing load and increasing surface roughness. An ion plated lead film gave better life than a sputtered MoS2 film. However, by keeping the interfacial shear stress at a low level, adequate coating life was achieved for either coating. For the lead film, the critical stress was about 0.19 GPa (28 ksi). The study dealt only with mechanical wear. Before a coating is selected for a critical space application, other factors such as reaction with atomic oxygen must also be considered

A lightweight, high output soil sampler

Sampler is useful on or under earth's surface or on sea bottom. Larger sample amount is obtained relative to sampler size and weight and limited particle size sample material is continuously delivered. Silicone rubber linear in transport tube nearly eliminates grinding or particulate processing during sampling, and reduces required torque

Study of high-speed angular-contact ball bearings under dynamic load

Research program studies behavior of specific high-speed, angular-contact ball bearings. Program is aimed at detailed investigation of ball-separator behavior and lubrication surface-finish effects in a specific gyro wheel

Evaluation of feasibility of measuring EHD film thickness associated with cryogenic fluids

The feasibility of measuring elastohydrodynamic (EHD) films as formed with a cryogenic (LN2) fluid is evaluated. Modifications were made to an existing twin disk EHD apparatus to allow for disk lubrication with liquid nitrogen. This disk apparatus is equipped with an X-ray system for measuring the thickness of any lubricant film that is formed between the disks. Several film thickness experiments were conducted with the apparatus which indicate that good lubrication films are filmed with LN2. In addition to the film thickness studies, failure analyses of three bearings were conducted. The HPOTP turbine end bearings had experienced axial loads of 36,000 to 44,000 N (8,000 to 10,000 lb). High continuous radial loads were also experienced, which were most likely caused by thermal growth of the inner race. The resulting high internal loads caused race spalling and ball wear to occur

Ecological effects of reservoir operations on Blue Mesa Reservoir

Includes bibliographical references.Annual progress report, May 1, 1997-April 30, 1998

Seasonal changes in a eutrophic lake, Wilgreen Lake, Madison County, Kentucky

WilgreenLake (Madison County, Kentucky) covers ~169 acres, formed in 1966 by damming Taylor Fork. The Wilgreen watershed drains residential developments, modified woodlands, cattle pasture, and some industrial/urban areas in the city ofRichmond. The lake is deemed “nutrient impaired” by the EPA. Our main objective is to document the seasonal changes in key lake parameters from summer stratification through fall overturn over 4 months of sampling, August through November, 2008. We collect temperature, oxygen, pH, and conductivity data from 19 stations at depth intervals of 1 meter using an YSI multi-probe. Concurrent with collecting these framework data, we take water samples, also at 1-meter intervals, and measure phosphate (PO4-), ammonium (NH4+), and nitrate (NO3-) concentration. Summer stratification exerts a large control on processes occurring within the lake, as does stream inflow. August and September surface temperatures range from 25 to 26.5 degrees Celsius, considerably cooler than in 2006 and 2007. The summer thermocline was located between 6 and 7 meters. Oxygen concentrations are highest in surface layer of the lake, become disoxic below 3 to 4 meters, and are anoxic only for the bottom several meters at our deepest stations. In 2008, a much smaller volume of the lake was anoxic. We attribute these annual differences to a much cooler and wetter early summer in 2008. Much higher nutrient concentrations occur near the largest stream inputs into the lake, either from watershed runoff or from anthropogenic sources near the lakeshore such as septic systems

COVARIANCE ANALYSIS WITH A COVARIATE INTERACTION: AN EXAMPLE OF A SIMPLE LINEAR REGRESSION COMPARISON TECHNIQUE

Many real data sets that would normally lend themselves to being analyzed by an analysis of covariance, have a covariate interaction present with one or more of the factors in the experiment. Because this violates the assumption of same-slope covariate effect across all treatments, an analysis of covariance should not be performed. The course normally taken when there is such an interaction is to derive regression equations for the dependent variable as a function of the covariate, at each level of the factor(s) being tested. A general linear model F-test can then be used to test whether there are any overall differences between the regression lines. A technique that uses two mathematical distance measures to detect regression line differences once a significant general linear model F-test is obtained is illustrated. Applying these distance measures enables us to perform modified multiple comparisons of the regressions without resorting to the use of multiple pairwise general linear model F-tests, which inflate the Type I error rate. with this method, we are able to incorporate both factor and covariate information into the analysis to overcome the covariate-factor interaction problem