Outdoor Test Site Research Articles

Predicting Galvanic Corrosion of Aluminum Using Accelerated Laboratory Electrochemical Experiments

Aluminum (Al) alloys are the most commonly used non-ferrous metals (approximately 25 million tons per year) for various technical applications and is the second most commonly used metal alloy after steel. Al alloys are also used in combination with other metals or materials to get specific desirable properties for applications such as transportation, construction, electrical appliances, and consumer goods. However, a system of dissimilar materials can lead to potential corrosion problems such as galvanic and crevice corrosion. In this work, atmospheric galvanic corrosion of Al alloy was predicted by combining electrochemical techniques and accelerated laboratory corrosion tests. Three different galvanic couples were analyzed where 6061-T6 Al alloy was coupled with a passivating metal (304 stainless steel), noble metal (copper), and a carbon fiber-reinforced polymer matrix composite (CFR PMC). The galvanic current flowing between the anode and cathode was measured using the zero-resistance ammeter (ZRA) technique in the humidity-chamber setup, cyclic corrosion test chamber following a modified GM9540P cycle, and an outdoor exposure test site. Electrolytes with varying amounts of chloride contents were used to simulate different atmospheric conditions. Four separate equations based on Faraday's law were developed to calculate the corrosion rate in grams per meter square per day (gmd) by relating the time of wetness (TOW) to the galvanic current measured from the accelerated laboratory experiments. The total exposure time was divided into wet periods (Twet) and dry periods (Tdry). The surface morphology of Al samples from the galvanic couples was studied using a scanning electron microscope (SEM), and elemental surface analysis was conducted using energy-dispersive X-ray Spectroscopy (EDXA). Figure 1

Soil compaction monitoring via photogrammetric settlement measurement – Feasibility study

This paper presents a new method of global compaction monitoring based on surface settlement measurements using the Structure from Motion (SfM) approach. The introduced approach was developed to enhance research on soil compaction. A layer of medium sand was compacted with a plate compactor during the experiment on an outdoor test site. The settlement of the soil surface was measured using close-range photogrammetry and optical level. Furthermore, relationships between settlement and changes in layer density and stiffness were studied. The analysis showed that the Structure from Motion approach allows for monitoring soil surface settlement with excellent resolution and accuracy. Moreover, the change of settlement and dynamic modulus during compaction showed a similar trend. This indicates that the proposed approach is a valuable tool for researchers studying the compaction process. Nevertheless, it implementing such technology in industrial projects still requires further development, especially in improving standardization and automation.

Mission-level Robustness with Rapidly-deployed, Autonomous Aerial Vehicles by Carnegie Mellon Team Tartan at MBZIRC 2020

For robotic systems to succeed in high risk, real-world situations, they have to be quickly deployable and robust to environmental changes, under-performing hardware, and mission subtask failures. These robots are often designed to consider a single sequence of mission events, with complex algorithms lowering individual subtask failure rates under some critical constraints. Our approach utilizes common techniques in vision and control, and encodes robustness into mission structure through outcome monitoring and recovery strategies. In addition, our system infrastructure enables rapid deployment and requires no central communication. This report also includes lessons in rapid field robotic development and testing. We developed and evaluated our systems through real-robot experiments at an outdoor test site in Pittsburgh, Pennsylvania, USA, as well as in the 2020 Mohamed Bin Zayed International Robotics Challenge. All competition trials were completed in fully autonomous mode without RTK-GPS. Our system placed fourth in Challenge 2 and seventh in the Grand Challenge, with notable achievements such as popping five balloons (Challenge 1), successfully picking and placing a block (Challenge 2), and dispensing the most water onto an outdoor, real fire with an autonomous UAV (Challenge 3).

Atmospheric corrosion severity and the precision of salt deposition measurements made by the wet candle method

ABSTRACT The Wet Candle technique quantifies the dry deposition flux of atmospheric species onto a gauze wick. Salt deposition flux is used to rate the corrosion severity of outdoor test sites. It is important to quantify the precision of the Wet Candle method if the results are used to compare the atmospheric corrosivity of various sites. An analysis of Wet Candle precision is conducted in terms of repeatability and reproducibility. The percent deviation is 3.2% for chloride repeatability and 3.3% for chloride reproducibility. Interval testing is conducted to determine if weekly intervals added together yield a deposition flux similar to a month-long interval. Weekly results are assessed alongside meteorological data to correlate atmospheric conditions to dry deposition. Finally, the erroneous contribution of chloride from various types of gloves to deposition flux is quantified. Based on these findings, recommendations are made on how to avoid various sources of error.

Active neutron interrogation experiments and simulation verification using the SIngle-scintillator Neutron and Gamma-Ray spectrometer (SINGR) for geosciences

We present a new SIngle-scintillator Neutron and Gamma-Ray spectrometer (SINGR) instrument for use with both passive and active measurement techniques. Here we discuss, the application of SINGR for planetary exploration missions; however, hydrology, nuclear non-proliferation, and resource prospecting are all potential areas where the instrument could be applied. SINGR uses an elpasolite scintillator, Cs2YLiCl6:Ce (CLYC), that has been shown to have high neutron efficiency even at small volumes, with a gamma-ray energy resolution of approximately 4% full-width-at-half-maximum at 662 keV. Active gamma-ray and neutron (GRNS) measurements were performed with SINGR at the NASA Goddard Space Flight Center (GSFC) Goddard Geophysical and Astronomical Observatory (GGAO) outdoor test site using a pulsed neutron generator (PNG) to interrogate geologically relevant materials (basalt and granite monuments). These experimental results, combined with simulations, demonstrate that SINGR is capable of generating neutron die-away curves that can be used to reconstruct the bulk hydrogen abundance and the depth distribution of hydrogen within the monuments. We compare our experimental results with Monte Carlo N-Particle (MCNP) 6.1 transport simulations to constrain the uncertainties in depth and hydrogen abundance from the neutron die-away data generated by SINGR. For future planetary exploration missions, SINGR provides a single detector system for interrogating the shallow subsurface to characterize the presence and abundance of hydrated phases and to provide bulk elemental analysis.

Design and analysis of an 8‐element dipole array for passive coherent location systems

AbstractThis article deals with a design and analysis of an 8‐element dipole array for passive coherent location (PCL) systems. The array is composed of eight identical dipole elements that are arranged at a radius of 0.5λ0 from the center to the elements. To verify the performance for the PCL system, the array is fabricated and measured in an outdoor test site. Array performances such as the antenna gain, peak to side lobe ratio (PSLR), half‐power beam width (HPBW), null width, and null depth are then analyzed. The results demonstrate that the proposed array has beam pattern characteristics suitable for PCL systems.

Quantifying Thermal Characteristics of Stormwater through Low Impact Development Systems

Urbanization causes alteration of the thermal regime (surface, air, and water) of the environment. Heated stormwater runoff flows into lakes, streams, bays, and estuaries, which potentially increases the base temperature of the surface water. The amount of heat transferred, and the degree of thermal pollution is of great importance to the ecological integrity of receiving waters. This research reports on a controlled laboratory scale test to assess low impact development (LID) stormwater control measure impacts on the thermal characteristics of stormwater runoff. We hypothesize that LID stormwater control measures (SCMs) such as pervious surfaces and rain gardens/bioretention can be used to mitigate the ground level thermal loads from stormwater runoff. Laboratory methods in this study captured and infiltrated simulated stormwater runoff from four infrared heated substrate microcosms (pervious concrete, impervious concrete, permeable concrete pavers, and turf grass), and routed the stormwater through rain garden microcosms. A data logging system with thermistors located on, within, and at exits of the microcosms, recorded resulting stormwater temperature flux. Researchers compared steady state temperatures of the laboratory to previously collected field data and achieved between 30% to 60% higher steady state surface temperatures with indoor than outdoor test sites. This research helps establish baseline data to study heat removal effectiveness of pervious materials when used alone or in combination as a treatment train with other stormwater control measures such as rain gardens/bioretention.

Influence of atmospheric particulates on initial corrosion behavior of printed circuit board in pollution environments

It is well-known that the climate has a strong impact on the corrosion behaviour of metals, especially when the influence of haze particles in the polluted air is also taken into account. In this study, four typical climatic environments in Xishuangbanna, Wuhan, Beijing and Turpan of China were selected as outdoor exposure test sites to study the corrosion mechanism of copper-clad Printed Circult Board (PCB-Cu), respectively. Based on the analysis of the corrosion morphology of PCB-Cu after exposure test and the composition of corrosion products, corrosion behavior of PCB-Cu under outdoor and simulated indoor environments was both revealed. Under low humidity conditions such as Beijing and Turpan, haze particles absorbed on PCB-Cu could act as a original inducement of corrosion in the initial stage, which triggered the occurrence of localized corrosion in the following stage. In contrast, local corrosion caused by haze particles was not significant under higher humidity conditions in Xishuangbanna and Wuhan, where uniform corrosion on the PCB-Cu was observed.

ROBUST AND ACCURATE IMAGE-BASED GEOREFERENCING EXPLOITING RELATIVE ORIENTATION CONSTRAINTS

Abstract. Urban environments with extended areas of poor GNSS coverage as well as indoor spaces that often rely on real-time SLAM algorithms for camera pose estimation require sophisticated georeferencing in order to fulfill our high requirements of a few centimeters for absolute 3D point measurement accuracies. Since we focus on image-based mobile mapping, we extended the structure-from-motion pipeline COLMAP with georeferencing capabilities by integrating exterior orientation parameters from direct sensor orientation or SLAM as well as ground control points into bundle adjustment. Furthermore, we exploit constraints for relative orientation parameters among all cameras in bundle adjustment, which leads to a significant robustness and accuracy increase especially by incorporating highly redundant multi-view image sequences. We evaluated our integrated georeferencing approach on two data sets, one captured outdoors by a vehicle-based multi-stereo mobile mapping system and the other captured indoors by a portable panoramic mobile mapping system. We obtained mean RMSE values for check point residuals between image-based georeferencing and tachymetry of 2 cm in an indoor area, and 3 cm in an urban environment where the measurement distances are a multiple compared to indoors. Moreover, in comparison to a solely image-based procedure, our integrated georeferencing approach showed a consistent accuracy increase by a factor of 2–3 at our outdoor test site. Due to pre-calibrated relative orientation parameters, images of all camera heads were oriented correctly in our challenging indoor environment. By performing self-calibration of relative orientation parameters among respective cameras of our vehicle-based mobile mapping system, remaining inaccuracies from suboptimal test field calibration were successfully compensated.

Non-Destructive Failure Detection and Visualization of Artificially and Naturally Aged PV Modules

Several series of six-cell photovoltaic test-modules—intact and with deliberately generated failures (micro-cracks, cell cracks, glass breakage and connection defects)—were artificially and naturally aged. They were exposed to various stress conditions (temperature, humidity and irradiation) in different climate chambers in order to identify (i) the stress-induced effects; (ii) the potential propagation of the failures and (iii) their influence on the performance. For comparison, one set of test-modules was also aged in an outdoor test site. All photovoltaic (PV) modules were thoroughly electrically characterized by electroluminescence and performance measurements before and after the accelerated ageing and the outdoor test. In addition, the formation of fluorescence effects in the encapsulation of the test modules in the course of the accelerated ageing tests was followed over time using UV-fluorescence imaging measurements. It was found that the performance of PV test modules with mechanical module failures was rather unaffected upon storage under various stress conditions. However, numerous micro-cracks led to a higher rate of degradation. The polymeric encapsulate of the PV modules showed the build-up of distinctive fluorescence effects with increasing lifetime as the encapsulant material degraded under the influence of climatic stress factors (mainly irradiation by sunlight and elevated temperature) by forming fluorophores. The induction period for the fluorescence effects of the polymeric encapsulant to be detectable was ~1 year of outdoor weathering (in middle Europe) and 300 h of artificial irradiation (with 1000 W/m2 artificial sunlight 300–2500 nm). In the presence of irradiation, oxygen—which permeated into the module through the polymeric backsheet—bleached the fluorescence of the encapsulant top layer between the cells, above cell cracks and micro-cracks. Thus, UV-F imaging is a perfect tool for on-site detection of module failures connected with a mechanical rupture of solar cells.

A New Method of VHF Antenna Gain Measurement Based on the Two-ray Interference Loss

Antenna gain is an important index of wireless communication system, how to accurate measurement of antenna gain is a difficult problem. There are many factors affecting the VHF antenna gain test accuracy in the outdoor test site. Ground reflected wave is the most important source of error. A new method is proposed in this paper to measure the antenna gain by using a two-ray interference loss to modify, which improved the antenna gain accuracy.

111 sun concentrator photovoltaic module with wide acceptance angle that can efficiently operate using 30-min intermittent tracking system

In this study, we propose a new concentrator photovoltaic (CPV) system design with a large-acceptance-angle lens, which tracks the sun on the basis of a new 30-min intermittent tracking method that does not require a special high-precision CPV tracking system. This will reduce costs, because a large percentage of the cost of a typical CPV system comes from the expensive accurate tracking system. The present system had a concentration ratio of 111 and an acceptance angle of 4.5°. We conducted an experiment to evaluate the thermal and electrical performances of the system in an outdoor test site in Miyazaki, Japan. The experimental results were compared with optical, thermal, and electrical simulation results. The simulated results showed good agreement with the experimental ones.

Diffuse and direct light solar spectra modeling in PV module performance rating

To achieve higher accuracy in power rating of photovoltaic modules and systems we recently developed an advanced PV performance model that separately addresses the contribution of diffuse and direct solar irradiance. To further improve the accuracy, we upgraded the model in this study to include the influence of solar spectrum on PV module conversion efficiency. We measured solar spectrum in Ljubljana separately for diffuse and direct irradiances under different weather conditions and calculated spectral losses or gains compared to AM1.5 reference spectrum. For diffuse irradiance under clear sky conditions we detected spectral losses from 4.5% during morning hours and up to 23.9% at around noon. During cloudy conditions the average losses were 3.5% and the variation of losses during the day was hardly noticeable. For direct irradiance we detected spectral gains, ranging from 0.8% to 10.3% for air mass values from 1.1 to 5.0, respectively. We modeled obtained results of spectral influence on PV module performance by introducing spectral correction factor separately for direct irradiance with air mass as an input parameter and for diffuse irradiance with the share of diffuse irradiance as an input parameter. The spectral correction factors are applied to measured diffuse and direct irradiance which are then used as an input parameters of the developed PV performance model. We evaluated the increase of accuracy of the model with the spectral upgrade for one month and one year measurements of a silicon PV module at an outdoor monitoring test site in Ljubljana, Slovenia. For the month of June 2014 the normalized root-mean-square error of the spectrally upgraded model was 2.3% compared to 2.7% without spectral correction. For the eight snowless months period in 2014 the error of evaluated performance model improved from 3.7% to 3.3% when the spectral correction was applied.

The Utilization of Hydrophobic Coatings on Insulative Skirts to Galvanically Decouple Mechanically-Fastened Aluminum Alloy and Carbon-Fiber Reinforced Polymer-Matrix Composites

In a quest to reduce weight and improve performance, aluminum (Al) alloys have been used in conjunction with lightweight materials such as carbon-fiber reinforced (CFR) polymer-matrix composites (PMCs). The mechanical contact of CFR PMCs (which serves as cathode) with Al alloys (which serves as anode) can result in galvanic corrosion of the Al alloys in a corrosive environment. The major objective of this research was on devising corrosion control strategies for couples of 6061-T6 Al that were mechanically fastened to CFR PMCs using Ti-6Al-4V bolts. A typical method used to mitigate galvanic corrosion when bolting Al to CFR PMCs is to insert an insulating layer (G-10 fiberglass or E-glass–reinforced PMC) between the members. Although the direct contact between the aluminum and CFR PMC is eliminated, the aluminum and the CFR PMC are still galvanically coupled through the Ti fastener, and galvanic corrosion on Al will occur if the electrolyte bridges over the insulating layer. Galvanic corrosion can be mitigated by increasing the IR loss across the skirt, which can be achieved by lengthening the skirt or breaking up the continuity of the salt bridge that forms on the skirt. The continuity of the salt bridge can be disrupted by applying hydrophobic coatings on the insulative skirt. In this study, galvanic corrosion rates were monitored for 6061-T6 Al—CFR PMC couples (with insulating skirts) subjected to the following conditions: 1) Insulting skirts having coatings (silane-based coating, epoxy, polyurethane, or latex) of various levels of hydrophobicity 2) Salt solutions of various concentrations (0, 10, 100, 1000, 10000, and 20000 ppm of chlorides) 3) Various insulating skirt lengths (0.25 inch or 0.5 inch), 4) Various exposure conditions (controlled humidity laboratory exposure, outdoor exposure with sheltered and unsheltered conditions). The effect on galvanic corrosion by the different coatings was studied as a function of hydrophobicity, as determined by the contact angle for wetting. The contact angle was measured on the coating surface before and after exposure to the outdoor test sites to study the effects of environmental degradation on hydrophobicity. The degradation of the coatings was also studied using other techniques such as Raman spectroscopy. The ingress of environmental constituents (i.e., chlorides, sodium ions, etc.,) towards the anode and cathode surfaces was analyzed using scanning electron microscopy (SEM) and energy dispersive-X-ray analysis (EDXA).

CMGユニットを用いたロープ型宇宙エレベーター実験用クライマーの昇降安定化制御

By using a tether (cable) to link the ground station and the space station at 36,000[km] altitude, a space elevator is envisioned where transportation is achieved by a climber that ascends and descends the tether. In anticipation of industrial applicability near the ground, a climber for a rope-type tether (rope-type climber) was developed in this study. Compared with a climber for a belt-type tether, the rope-type climber has a small contact area between the tether and the roller, leading to problems with slippage and roller deterioration. Accordingly, here the contact area between the rope and roller was increased by using four drive wheels, and synchronized velocity control was accomplished with two drive motors for two drive wheels. Also the rope-type climber has more difficulty maintaining its orientation and is easily rotated around the tether by wind and other factors, so a control moment gyro (CMG) unit was developed that can be applied to the climber. An optimal servo system using a disturbance observer was applied to a rope-type climber with the developed CMG unit to achieve lift stabilization control. Then the effectiveness of the developed system was verified in lift experiments at the 25[m] outdoor test site of Kanagawa University and in a 1.2[km] lift experiment at the Space Elevator Challenge.

Parameters affecting laterally loaded piles in frozen soils by an efficient sensitivity analysis method

In cold regions, accurately simulating the nonlinear responses of frozen soil–structure interaction (SSI) systems is of significant importance for the seismic safety assessment. This paper presents a finite element (FE) simulation of nonlinear lateral responses of a real reinforced-concrete filled steel pipe pile embedded in frozen ground at an outdoor test site in Fairbanks, Alaska. A pressure-independent multi-yield surface J2 plasticity model is used to simulate the frozen soil behavior, while frame element with fiber section and nonlinear steel/concrete model are used for the pile. The FE analysis results agree well with the experiment results. Furthermore, the response sensitivities to various material parameters are computed by using an efficient and accurate gradient computation method, i.e., direct differentiation method (DDM), with limited additional computational cost. Based on DDM, the relative importance of material parameters on system responses is studied when the system is subjected to varying lateral deflections, respectively (corresponding to different levels of lateral loads such as earthquakes). Stiffness-related parameters are dominant when the system is subject to small deflections, while strength-related or post-yield parameters become dominant for large deflections. In addition, global responses are slightly more sensitive to material parameters of pile than the parameters of frozen soil. The response sensitivity to the unfrozen soil below the frozen ground crust is almost negligible. Finally, the response sensitivities to the soil parameters are observed to decrease when the distance of the soil from the pile increases. The sensitivity analysis methodology presented in this paper can be adapted to other frozen soil–pile interaction cases and the study results provide valuable insight for engineering practice.

Wood facade materials ageing analysis by FTIR spectroscopy

Attenuated total reflection Fourier transform infrared spectroscopy is used in this study to quantify wood degradation. Nine different types of wood materials were studied. All types of wood were exposed in an Atlas solar simulator against artificial climate conditions. Additionally, natural climate exposure was performed for all types of wood at an outdoor test site in Trondheim, Norway, for 4 years. Surface treatment enhanced the durability of the wood and their performance against weathering. Rough surfaces might reduce the resistance against degradation in comparison with planed surfaces. The degradation during climate exposure created loss of lignin and accumulation of cellulose at the surface.

Long front time switching impulse tests of long air gap in UHV projects at altitude of 2100 m

The past and recent investigations show that front time of switching overvoltage waveforms in Ultra High Voltage (UHV) system of long distance transmission are mostly in long wave front time exceeding 1000μs. The long front time of switching impulse voltage has been deviated from the critical front time. This paper is involved with breakdown characteristics and external insulation design under long front switching impulse voltage in UHV system. All the Tests were performed on an outdoor UHV test site at altitude of 2100 m, China Southern Power Grid Co. Ltd. (CSG). Breakdown characteristics of rod-plane and actual size tower-conductor in /spl l.chemo/800 kV UHV DC transmission line are obtained under wide front time switching impulse voltages from 100 to 2350 μs. From the comprehensive studies of such tests, it is proposed that U50 of front time exceeding 1000 μs increases 20% compared with the results of standard switching impulse (250/2500 μs) tests and standard deviations of U50 is 6% in UHV transmission system. Finally, an air gap insulation design procedure in conductor-tower of UHV transmission line at altitude of 0-2000 m is presented. Long front time switching impulse strength of conductor-tower gap is proposed into selection by reference in UHV transmission line insulation design.

Determination of Threshold Electric Field of Practical Earthing Systems by FEM and Experimental Work

In this paper, the results of an experimental study and finite-element method (FEM) of the impulse characteristics of simply built practical earthing systems consisting of 2, 3, and 4 rods are reported. These electrodes are installed at three outdoor test sites having nonuniform soil and different soil profiles to provide variation in the result analysis. The tests on these electrodes were intended to determine the nonlinear characteristics of earthing systems which can be seen from their voltage and current traces and reduction of their impulse resistance values. Two-rod electrodes in the highest soil resistivity profile showed the largest reductions in impulse resistance due to soil ionization compared with other earth electrodes. Computer simulations of all the nine earthing systems using the FEM are also conducted, which showed good agreement with the measured results. It was also found from FEM that threshold electric field Ec is dependent on the earthing systems configurations, soil profile, and impulse resistances.

Prediction of electrical performance of medium voltage epoxy insulated equipment

The paper presents a theoretical model based on the 2-parameter Weibull Distribution to predict the performance of cycloaliphatic based medium voltage (< 100 kV) insulation equipment. The model combines two prominent modes of degradation, namely surface damage (tracking and erosion) and flashover. New samples and samples that were aged in service and in outdoor test sites were evaluated. The flashover model is based on evaluating surface resistance under wet conditions. The degradation model is based on evaluating the tracking and erosion resistance in the Inclined Plane (ASTM D2303) test. The predictions of the model are shown to be in good agreement with experimental results. A total of 20 insulators and instrument transformers (new and field-aged) were evaluated.