In this report, we investigate how manufacturing conditions result in the warpage of moderate density PMDI polyurethane foam (12-50 lb/ft3) when they are released from a mold. We have developed a multiphysics modeling framework to simulate the manufacturing process including resin injection, foaming and mold filling, gelation of the matrix, elevated cure, vitrification, cool down, and demolding. We have implemented this framework within the Sierra Mechanics Finite Element Code Suite. We couple Aria for flow, energy conservation, and foaming/curing kinetics with Adagio for the nonlinear viscoelastic solid response in a multi-staged simulation process flow. We calibrate a model for the PMDI-10S (10 lb/ft3 free rise foam) through a suite of characterization data presented here to calibrate the solid cure behavior of the foam. The model is then used and compared to a benchmark experiment, the manufacturing and warpage over 1 year of a 10 cm by 10 cm by 2.5 cm foam "staple". This component features both slender and thick regions that warp considerably differently over time. Qualitative agreement between the model and the experiment is achieved but quantitative accuracy is not.
Sandia National Laboratories has tested and evaluated a new digitizer, the Affinity, manufactured by Guralp Systems Ltd. These digitizers are used to record sensor output for seismic and infrasound monitoring applications. The purpose of the digitizer evaluation was to measure the performance characteristics in such areas as power consumption, input impedance, sensitivity, full scale, self-noise, dynamic range, system noise, response, passband, and timing. The Affinity digitizer is Guralp's latest release in their digitizer product line. The Affinity is available with either 4 or 8 channels at 24 bit resolution. In addition to the 24 bit channels, 16 multiplexed low resolution channels are provided. Other features include the means to accept multiple types of timing sources (e.g. GPS, NTP and PTP) and a web page interface for command and control of the unit.
Sandia National Laboratories has tested and evaluated a new digitizer, the Q330HR, manufactured by Quanterra. These digitizers are used to record sensor output for seismic and infrasound monitoring applications. The purpose of the digitizer evaluation was to measure the performance characteristics in such areas as power consumption, input impedance, sensitivity, full scale, self-noise, dynamic range, system noise, response, passband, and timing. The Q330HR is Quanterra’s improved Q330 datalogger with a 26 bits of resolution on channels 1-3 and a 24 bits of resolution on channels 4-6 (26 bit is optional). The Quanterra Q330HR is being evaluated for potential use U.S. Air Force seismic monitoring systems as part of their Next Generation Qualification effort.
Sandia National Laboratories has tested and evaluated a new digitizer, the Centaur, manufactured by Nanometrics. These digitizers are used to record sensor output for seismic and infrasound monitoring applications. The purpose of the digitizer evaluation was to measure the performance characteristics in such areas as power consumption, input impedance, sensitivity, full scale, self-noise, dynamic range, system noise, response, passband, and timing. The Centaur digitizer is Nanometrics’ replacement for their Taurus digitizer and marks Nanometrics first 6 channel, 24 bit resolution system. Other improvements include LED status indicators on the top of the unit, providing basic status of the core systems of a seismic station (e.g. timing, sensor SOH, storage, etc), an optional wifi system allowing password protected access to the unit and a web interface for monitoring and configuration of the unit. The Nanometrics Centaur is being evaluated for potential use U.S. Air Force seismic monitoring systems as part of their Next Generation Qualification effort.
The levelized cost of energy for an offshore wind plant consisting of floating vertical-axis wind turbines is studied in this report. A 5 MW Darrieus vertical-axis wind turbine rotor is used as the study turbine as this architecture was determined to have the greatest ability to reduce the system cost. The rotor structural design was used with blade manufacturing cost model studies to estimate its cost. A two-bladed, carbon fiber rotor was selected in this analysis since the lower topside mass resulted in a reduction of the platform costs which exceeded the increased rotor cost. A direct-drive, medium efficiency drivetrain was designed which represents 25% of the costs and 45% of the mass of the combined rotor/drivetrain system. A direct-drive, permanent magnet generator drivetrain was selected due to the improved reliability of this type of system, while the cost was not significantly higher than for geared drivetrains. A platform was designed by first identifying the optimal architecture for the vertical-axis wind turbine at a water depth of 150 m. A survey was performed of floating platform types, and six characteristic designs were analyzed which span the range of stability mechanisms available to floating systems. A multi-cellular tension-leg platform was identified as the lowest cost platform which additionally provided some interesting performance benefits. The small motions of the tension-leg platform benefit the system energy capture while limiting inertial loads placed on the rotor’s tower and blades. A final design was produced for the multi-cellular tension-leg platform considering operational fatigue, storm wind and wave conditions, and tow-out design cases. The driving design load was stability during tow-out while ballasting the platform. System levelized cost of energy was calculated, including operational expenses and balance of system costs estimated for the wind plant. Opportunities for reduction in the component costs are predicted and used to make projections of the system levelized cost of energy for future developments. The opportunities and challenges for floating vertical-axis wind turbines are identified by the system design and levelized cost of energy analysis.
The moisture absorption behavior of two fiber reinforced composite materials was evaluated in a unidirectional manner The flat materials were exposed to varying humidity and temperature conditions inside of an environmental chamber in order to determine their effective moisture equilibrium (M m ) and moisture absorption rate (D z ). Two-ply (thin) and four-ply (thick) materials were utilized to obtain M,,, and Dz, respectively. The results obtained from laboratory work were then compared to modeling data to better understand the material properties. Predictions capabilities were built to forecast the maximum moisture content, time required for saturation, and the moisture content at any given humidity and temperature. A case study was included to demonstrate this capability. Also of interest were cubed samples to investigate directionality preferences in water immersion studies. Several coatings were evaluated for their water permeation properties. Further dissemination authorized to the Department of Energy and DOE contractors only; other requests shall be approved by the originating facility or higher DOE programmatic authority.
This report compares ATLOG modeling results for the response of a finite-length dissipative buried conductor interacting with a conducting ground to a measurement taken November 2016 at the High-Energy Radiation Megavolt Electron Source (HERMES) facility. We use the ATLOG frequency-domain method based on transmission line theory. Estimates of the impedance per unit length and admittance per unit length for a cable laying in a PVC pipe embedded in a concrete block are reported. Current wave shapes from both a single conductor and composite differential mode and antenna mode arrangements are close to those observed in the experiments.
Narratives about water resources have evolved, transitioning from a sole focus on physical and biological dimensions to incorporate social dynamics Recently, the importance of understanding the visibility of water resources through media coverage has gained attention. This study leverages recent advancements in natural language processing (NLP) methods to characterize and understand patterns in water narratives, specifically in 4 local newspapers in Utah and Georgia. Analysis of the corpus identified coherent topics on a variety of water resources issues, including weather and pollution. Closer inspection of the topics revealed temporal and spatial variations in coverage, with a topic on hurricanes exhibiting cyclical patterns whereas a topic on tribal issues showed coverage predominantly in the western newspapers. We also analyzed the dataset for sentiments, identifying similar categories of words on trust and fear emerging in the narratives across newspaper sources. An analysis of novelty, transience, and resonance using Kullback-Leibler Divergence techniques revealed that topics with high novelty generally contained high transience and marginally high resonance over time. Although additional analysis needs to be conducted, the methods explored in this analysis demonstrate the potential of NLP methods to characterize water narratives in media coverage.
Bieberdorf, Nathan; Towner, Zachary; Hubbard, Neal B.; Gerstle, Walter
In this work, various material models were studied for their ability to simulate puncture in a thin aluminum 7075-T651 plate due to low-velocity probe impact. Material models were generated by mixing and matching various work hardening laws with different failure criteria, and several hybrid material models were investigated. Finite element simulations of aluminum impact-response, based on each material model, were employed to predict the energy required for puncture and final plate tear-out geometry. Probes of different size and shape were used to impose various loading regimes, and numerical predictions were compared to experimental results from a previous study. It was found that no single combination of hardening and failure laws yielded universally accurate data, but that several material models could be used more reliably than others. Further, the importance of obtaining unique parameter-sets for work-hardening and failure criteria was illustrated.
CSP Dish systems are parabolic mirror structures that track the sun in two axes, focusing the Direct Normal insolation (DNI) to a point or spot on a boom or tripod mounted to the tracking dish structure. This focused light is typically utilized in-situ to operate a heat engine, such as a Stirling cycle, Brayton cycle, or Rankine cycle engine to make electricity. Other dish systems have been used to generate steam for a centralized engine fed by multiple dishes, or to operate thermochemical processes for industrial use, storage, or creation of fuels. Because the dish is always pointing at the sun, a well-designed dish system has a very high concentration ratio, allowing the generation of high temperatures, leading to high thermodynamic efficiencies.
Schedule Management Optimization (SMO) is a tool for automatically generating a schedule of project tasks. Project scheduling is traditionally achieved with the use of commercial project management software or case-specific optimization formulations. Commercial software packages are useful tools for managing and visualizing copious amounts of project task data. However, their ability to automatically generate optimized schedules is limited. Furthermore, there are many real-world constraints and decision variables that commercial packages ignore. Case-specific optimization formulations effectively identify schedules that optimize one or more objectives for a specific problem, but they are unable to handle a diverse selection of scheduling problems. SMO enables practitioners to generate optimal project schedules automatically while considering a broad range of real-world problem characteristics. SMO has been designed to handle some of the most difficult scheduling problems – those with resource constraints, multiple objectives, multiple inventories, and diverse ways of performing tasks. This report contains descriptions of the SMO modeling concepts and explains how they map to real-world scheduling considerations.
The atmospheric dispersion of contaminants in the wake of a large urban structure is a challenging fluid mechanics problem of interest to the scientific and engineering communities. Magnetic Resonance Velocimetry (MRV) is a relatively new technique that leverages diagnostic equipment used primarily by the medical field to make 3D engineering measurements of flow and contaminant dispersal. SIERRA/Fuego, a computational fluid dynamics (CFD) code at Sandia National Labs is employed to make detailed comparisons to the dataset to evaluate the quantitative and qualitative accuracy of the model. The comparison exercise shows good comparison between model and experimental results, with the wake region downstream of the tall building presenting the most significant challenge to the quantitative accuracy of the model. Model uncertainties are assessed through parametric variations. Some observations are made in relation to the future utility of MDV and CFD, and some productive follow-on activities are suggested that can help mature the science of flow modeling and experimental testing.
Scott, Ethan A.; Hattar, Khalid M.; Foulk, James W.; Gaskins, John T.; Bai, Tingyu; Wang, Steven Y.; Gansky, Claire; Goorsky, Mark; Hopkins, Patrick E.