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In the wind turbine industry, mechanical components sometimes have to operate under starved lubrication. This occurs mainly after maintenance and/or repairing procedures, when the wind turbine is starting up again after a prolonged inactive period. In field observations have shown that oil starvation is more prominent in warmer climates and of course for longer durations where the mechanical components remained 'inactive'. To get a better insight on this issue, a validation test procedure was developed based on reciprocating sliding tests. This protocol was used to investigate the starvation behaviour of two commercially available oils on metallic components, which were exposed at different temperatures (ranging from −20° to 40°C) and durations (ranging from 5 to 21 days). Based on these tests the resistance to starvation (failure time) and the effect of critical waiting time and temperature to initiate starvation were assessed. [ABSTRACT FROM AUTHOR]

The tribological behaviour of hydraulic fluids is mainly evaluated by standardized Vickers vane pump tests, according to ASTM D7043, DIN 51389 or ISO 20763. These tests provide the closest possible representation of actual working conditions, but require many hours of testing and large quantities of hydraulic fluids per experiment, while the frictional behaviour of the tribosystem is not measured. Because of the long testing time, oil quantity and cost, it is impractical to perform multiple tests and this makes the method unsuitable for development purposes. In this work, a new methodology is proposed that allows for a fast and efficient pre-screening and ranking of hydraulic fluids that correlates well with the Vickers vane pump test. To validate the methodology, five different hydraulic fluids are tested and compared to ISO 20763 Vickers vane pump test results. The aim is to achieve similar wear mechanisms and ranking of the anti-wear properties of hydraulic fluids. The future goal is to propose a standardized method that will aid in the development of hydraulic fluids and will complement existing standardized tests. [ABSTRACT FROM AUTHOR]

ASTM Method D3233A uses a Pin&Vee Block tester to evaluate cutting fluids. However, the standard defines a steel-steel contact, uses a small volume of lubricant, and the test report is limited to the 'ultimate failure load'. With our approach, we bring testing closer to reality, using different metallurgies and testing the oils in aqueous emulsion-form. We monitor the frictional torque throughout increasing load, so that differences between products are revealed that are not visible in failure load alone. By modifying lubrication to recirculated or misted conditions, we simulate cutting of forming operations. Consequently, this provides an additional tool for cost efficient ranking of cutting fluids, based on an industry-accepted instrument. We demonstrate same ranking of cutting fluids as well established Tapping Torque Tests, with the advantage of using a simplified and lower cost configuration. Developing a standardized test protocol involves more work on reproducibility and correlation to real machining processes. [ABSTRACT FROM AUTHOR]

Abstract: Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions. [Copyright &y& Elsevier]

Abstract: A method for determining evaporation rates and thermodynamic properties of aqueous solution droplets is introduced. The method combines evaporation rate measurements using modified TDMA technique with data evaluation using an accurate evaporation model. The first set of data has been collected and evaluated for succinic acid aqueous solution droplets. Evaporation rates of succinic acid solution droplets have been measured using a TDMA system at controlled relative humidity (65%) and temperature (298K). A temperature-dependent expression for the saturation vapour pressure of pure liquid phase succinic acid at atmospheric temperatures has been derived by analysing the evaporation rate data with a numerical model. The obtained saturation vapour pressure of liquid phase succinic acid is ln(p)=118.41−16204.8/T −12.452ln(T). The vapour pressure is in unit of Pascal and the temperature in Kelvin. A linear expression for the enthalpy of vaporization for liquid state succinic acid is also presented. According to the results presented in the following, a literature expression for the vapour pressure of liquid phase succinic acid defined for temperatures higher than 461K [Yaws, C.L., 2003. Yaws'' Handbook of Thermodynamic and Physical Properties of Chemical Compounds, Knovel] can be extrapolated to atmospheric temperatures with very good accuracy. The results also suggest that at 298 Kthe mass accommodation coefficient of succinic acid is unity or very close to unity. [Copyright &y& Elsevier]

With the increased attention to resources, sustainablity and reduction of carbon footprint on the life cycle of products, one of the challenging tribological issues is the prediction of long term wear. Indeed, in many industrial and technological components, materials operate under dry or lubricated conditions for thousands of hours. However, contrary to the determination of a coefficient of friction, which can typically reach 'steady state conditions' in a few hours, the determination of wear under realistic conditions is by definition a long term test. It is not easy to accelerate a wear mechanism without fundamentally changing it. In addition, friction tests are more repeatable than wear tests and for this reason it is always necessary to run multiple repeat tests and obtain a reliable statistical result. Commonly, to characterise a single material couple under one set of test conditions, requires at least three repeats at one duration and ideally this is to be repeated for more than one test duration to plot also the evolution of wear. It is clear that with a single-station test machine and tests that take weeks to perform, it is economically and practically impossible to generate enough measurements for data with high confidence levels. Therefore, in this work an approach is presented to measure the wear of materials is an efficient way and under realistic contact conditions. Such a method can be potentially used to more easily map wear evolution and performance of different materials. • New test method for evaluating wear evolution in an efficient way. • Statistical analysis of wear data to evaluate fluctuation of wear. • Relative ranking of wear of polymer-based materials with high confidence levels. • Effect of countermaterial on the wear evolution of fiberglass. [ABSTRACT FROM AUTHOR]

This work focuses on presenting a new methodology, based on approach-retraction curves, to objectively and accurately measure adhesion and tackiness of industrial greases. The definitions of pull-off force and tackiness are redefined, explained and measured, whereas the effect of testing parameters such as retraction speed, grease film thickness, applied load and temperature is discussed. This work aims to point out that the adhesion and tackiness of greases are not just a single value, but that they strongly depend on the experimental conditions. Based on this proposed method, a mapping of the tackiness of greases with respect to the experimental or working conditions can be performed. [ABSTRACT FROM AUTHOR]

This work focuses on transport and properties of ash from the Icelandic volcano Grímsvötn that erupted in spring 2011. Atmospheric transport of volcanic ash from the eruption was simulated using the Danish Emergency Response Model of the Atmosphere (DERMA). The arrivals of volcanic particles were detected on-line at Mace Head at the West coast of Ireland during volcanic plume advection identified by high resolution time of flight aerosol mass spectrometry (HR-ToF AMS). Based on DERMA information aerosol particles were collected in Copenhagen, Denmark, before predicted arrival of the ash plume and during a period where ash was present in the air. Analysis of the meteorological conditions shows that the particles collected before arrival of the volcanic ash may serve as a good reference sample allowing identification of significant changes in ambient aerosol properties during the volcanic ash event over Copenhagen. Using single particle analysis in scanning electron microscopy (SEM), data on structure, chemical composition, size and morphology of individual volcanic ash particles from the Grímsvötn eruption after atmospheric transport to Scandinavia are provided. Particles were sliced with Focused Ion Beam (FIB). Element mappings from cross-sections through collected volcanic ash particles reveal inhomogeneous distributions of the elements K, Mg, Fe and Ti. [ABSTRACT FROM AUTHOR]

Abstract: We studied the evaporation of submicrometer-sized, aqueous solution aerosol particles containing different mixing ratios of succinic acid, sodium chloride, and water. A modified tandem differential mobility analyzer (TDMA) including a laminar flow-tube was deployed to measure the evaporation rates of the particles at ambient atmospheric pressure and temperature, and at different relative humidities. A phase equilibrium model (extended aerosol inorganic model, ) was applied to predict the concentration, activity coefficients, and partitioning of the evaporating species. We also investigated the particles evaporation by combining an evaporation model with the phase equilibrium model. The observed evaporation could be predicted with reasonable accuracy at large relative amounts of succinic acid. At low relative amounts, the overpredicted evaporation suggests that inorganic salts might enhance the particle phase partitioning of organic acids more than expected based on present aerosol thermodynamic models. [Copyright &y& Elsevier]

Abstract: Vapor pressures of five methyl-substituted dicarboxylic acids are inferred from measurements of evaporation rates of sub-micron particles using the TDMA technique at ambient temperatures. Vapor pressures obtained are: , , , , , , . These vapor pressures are compared with available literature data and with vapor pressures of the un-substituted acids. Our results demonstrate that molecular structure is important for solid state vapor pressures of secondary organic aerosol components at ambient conditions. [Copyright &y& Elsevier]