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Bounding the moment deficit rate on crustal faults using geodetic data: Methods

Journal of Geophysical Research: Solid Earth

Maurer, Jeremy; Segall, Paul; Bradley, Andrew M.

The geodetically derived interseismic moment deficit rate (MDR) provides a first-order constraint on earthquake potential and can play an important role in seismic hazard assessment, but quantifying uncertainty in MDR is a challenging problem that has not been fully addressed. We establish criteria for reliable MDR estimators, evaluate existing methods for determining the probability density of MDR, and propose and evaluate new methods. Geodetic measurements moderately far from the fault provide tighter constraints on MDR than those nearby. Previously used methods can fail catastrophically under predictable circumstances. The bootstrap method works well with strong data constraints on MDR, but can be strongly biased when network geometry is poor. We propose two new methods: the Constrained Optimization Bounding Estimator (COBE) assumes uniform priors on slip rate (from geologic information) and MDR, and can be shown through synthetic tests to be a useful, albeit conservative estimator; the Constrained Optimization Bounding Linear Estimator (COBLE) is the corresponding linear estimator with Gaussian priors rather than point-wise bounds on slip rates. COBE matches COBLE with strong data constraints on MDR. We compare results from COBE and COBLE to previously published results for the interseismic MDR at Parkfield, on the San Andreas Fault, and find similar results; thus, the apparent discrepancy between MDR and the total moment release (seismic and afterslip) in the 2004 Parkfield earthquake remains.

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TYPE Journal Article YEAR 2017
DOIOSTIScopus

Adjoint-based optimization of mechanical performance in polycrystalline materials and structures through texture control

Gu, Grace; Brown, Judith A.; Bishop, Joseph E.

The texture of a polycrystalline material refers to the preferred orientation of the grains within the material. In metallic materials, texture can significantly affect the mechanical properties such as elastic moduli, yield stress, strain hardening, and fracture toughness. Recent advances in additive manufacturing of metallic materials offer the possibility in the not too distant future of controlling the spatial variation of texture. In this work, we investigate the advantages, in terms of mechanical performance, of allowing the texture to vary spatially. We use an adjoint-based gradient optimization algorithm within a finite element solver (COMSOL) to optimize several engineering quantities of interest in a simple structure (hole in a plate) and loading (uniaxial tension) condition. As a first step to general texture optimization, we consider the idealized case of a pure fiber texture in which the homogenized properties are transversely isotropic. In this special case, the only spatially varying design variables are the three Euler angles that prescribe the orientation of the homogenized material at each point within the structure. This work paves a new way to design metallic materials for tunable mechanical properties at the microstructure level.

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TYPE Other Report YEAR 2017
DOIOSTI

Integration of the SSPM and STAGE with the MPACT Virtual Facility Distributed Test Bed

Cipiti, Benjamin B.

The Material Protection Accounting and Control Technologies (MPACT) program within DOE NE is working toward a 2020 milestone to demonstrate a Virtual Facility Distributed Test Bed. The goal of the Virtual Test Bed is to link all MPACT modeling tools, technology development, and experimental work to create a Safeguards and Security by Design capability for fuel cycle facilities. The Separation and Safeguards Performance Model (SSPM) forms the core safeguards analysis tool, and the Scenario Toolkit and Generation Environment (STAGE) code forms the core physical security tool. These models are used to design and analyze safeguards and security systems and generate performance metrics. Work over the past year has focused on how these models will integrate with the other capabilities in the MPACT program and specific model changes to enable more streamlined integration in the future. This report describes the model changes and plans for how the models will be used more collaboratively. The Virtual Facility is not designed to integrate all capabilities into one master code, but rather to maintain stand-alone capabilities that communicate results between codes more effectively.

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TYPE SAND Report YEAR 2017
DOIOSTI

LAMMPS Project Report for the Trinity KNL Open Science Period

Moore, Stan G.; Thompson, Aidan P.; Wood, Mitchell

LAMMPS is a classical molecular dynamics code (lammps.sandia.gov) used to model materials science problems at Sandia National Laboratories and around the world. LAMMPS was one of three Sandia codes selected to participate in the Trinity KNL (TR2) Open Science period. During this period, three different problems of interest were investigated using LAMMPS. The first was benchmarking KNL performance using different force field models. The second was simulating void collapse in shocked HNS energetic material using an all-atom model. The third was simulating shock propagation through poly-crystalline RDX energetic material using a coarse-grain model, the results of which were used in an ACM Gordon Bell Prize submission. This report describes the results of these simulations, lessons learned, and some hardware issues found on Trinity KNL as part of this work.

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TYPE Other Report YEAR 2017
DOIOSTI

Nonlinear to Linear Elastic Code Coupling in 2-D Axisymmetric Media

Preston, Leiph

Explosions within the earth nonlinearly deform the local media, but at typical seismological observation distances, the seismic waves can be considered linear. Although nonlinear algorithms can simulate explosions in the very near field well, these codes are computationally expensive and inaccurate at propagating these signals to great distances. A linearized wave propagation code, coupled to a nonlinear code, provides an efficient mechanism to both accurately simulate the explosion itself and to propagate these signals to distant receivers. To this end we have coupled Sandia's nonlinear simulation algorithm CTH to a linearized elastic wave propagation code for 2-D axisymmetric media (axiElasti) by passing information from the nonlinear to the linear code via time-varying boundary conditions. In this report, we first develop the 2-D axisymmetric elastic wave equations in cylindrical coordinates. Next we show how we design the time-varying boundary conditions passing information from CTH to axiElasti, and finally we demonstrate the coupling code via a simple study of the elastic radius.

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TYPE SAND Report YEAR 2017
DOIOSTI

Effect of Microstructure Constraints on the Homogenized Elastic Constants of Elastomeric Sylgard/GMB Syntactic Foam

Brown, Judith A.; Steck, Daniel; Long, Kevin N.

Previous numerical studies of Sylgard filled with glass microballoons (GMB) have relied on various microstructure idealizations to achieve a large range of volume fractions with high mesh quality. This study investigates how different microstructure idealizations and constraints affect the apparent homogenized elastic constants in the virgin state of the material, in which all GMBs are intact and perfectly bonded to the Sylgard matrix, and in the fully damaged state of the material in which all GMBs are destroyed. In the latter state, the material behaves as an elastomeric foam. Four microstructure idealizations are considered relating to how GMBs are packed into a representative volume element (RVE): (1) no boundary penetration nor GMB-GMB overlap, (2) GMB-GMB overlap, (3) boundary penetration, and (4) boundary penetration and GMB-GMB overlap. First order computational homogenization with kinematically uniform displacement boundary conditions (KUBCs) was employed to determine the homogenized (apparent) bulk and shear moduli for the four microstructure idealizations in the intact and fully broken GMB material states. It was found that boundary penetration has a significant effect on the shear modulus for microstructures with intact GMBs, but that neither boundary penetration nor GMB overlap have a significant effect on homogenized properties for microstructures with fully broken GMBs. The primary conclusion of the study is that future investigations into Sylgard/GMB micromechanics should either force GMBs to stay within the RVE fully and/or use periodic BCs (PBCs) to eliminate the boundary penetration issues. The implementation of PBCs requires the improvement of existing tools in Sandia’s Sierra/SM code.

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TYPE Other Report YEAR 2017
DOIOSTI

Water Network Tool for Resilience (WNTR) User Manual

Klise, Katherine A.; Hart, David; Moriarty, Dylan M.; Bynum, Michael L.; Murray, Regan; Burkhardt, Jonathan; Haxton, Terra

Drinking water systems face multiple challenges, including aging infrastructure, water quality concerns, uncertainty in supply and demand, natural disasters, environmental emergencies, and cyber and terrorist attacks. All of these have the potential to disrupt a large portion of a water system causing damage to infrastructure and outages to customers. Increasing resilience to these types of hazards is essential to improving water security. As one of the United States (US) sixteen critical infrastructure sectors, drinking water is a national priority. The National Infrastructure Advisory Council defined infrastructure resilience as “the ability to reduce the magnitude and/or duration of disruptive events. The effectiveness of a resilient infrastructure or enterprise depends upon its ability to anticipate, absorb, adapt to, and/or rapidly recover from a potentially disruptive event”. Being able to predict how drinking water systems will perform during disruptive incidents and understanding how to best absorb, recover from, and more successfully adapt to such incidents can help enhance resilience.

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TYPE Other Report YEAR 2017
DOIOSTI

Microstructural Modeling of Brittle Materials for Enhanced Performance and Reliability

Teague, Melissa C.; Rodgers, Theron M.; Grutzik, Scott J.; Meserole, Stephen

Brittle failure is often influenced by difficult to measure and variable microstructure-scale stresses. Recent advances in photoluminescence spectroscopy (PLS), including improved confocal laser measurement and rapid spectroscopic data collection have established the potential to map stresses with microscale spatial resolution (%3C2 microns). Advanced PLS was successfully used to investigate both residual and externally applied stresses in polycrystalline alumina at the microstructure scale. The measured average stresses matched those estimated from beam theory to within one standard deviation, validating the technique. Modeling the residual stresses within the microstructure produced general agreement in comparison with the experimentally measured results. Microstructure scale modeling is primed to take advantage of advanced PLS to enable its refinement and validation, eventually enabling microstructure modeling to become a predictive tool for brittle materials.

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TYPE SAND Report YEAR 2017
DOIOSTI

Sandia National Laboratories, Tonopah Test Range Assembly Building 9B (Building 09-54): Photographs and Written Historical and Descriptive Data

Ullrich, Rebecca A.

Assembly Building 9B (Building 09-54) is a contributing element to the Sandia National Laboratories (SNL) Tonopah Test Range (TTR) Historic District. The SNL TTR Historic District played a significant role in U.S. Cold War history in the areas of stockpile surveillance and non-nuclear field testing of nuclear weapons designs. The district covers approximately 179,200 acres and illustrates Cold War development testing of nuclear weapons components and systems. This report includes historical information, architectural information, sources of information, project information, maps, blueprints, and photographs.

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TYPE Other Report YEAR 2017
DOIOSTI

Sandia National Laboratories, Tonopah Test Range Fire Control Bunker (Building 09-51): Photographs and Written Historical and Descriptive Data

Ullrich, Rebecca A.

The Fire Control Bunker (Building 09-51) is a contributing element to the Sandia National Laboratories (SNL) Tonopah Test Range (TTR) Historic District. The SNL TTR Historic District played a significant role in U.S. Cold War history in the areas of stockpile surveillance and non-nuclear field testing of nuclear weapons design. The district covers approximately 179,200 acres and illustrates Cold War development testing of nuclear weapons components and systems. This report includes historical information, architectural information, sources of information, project information, maps, blueprints, and photographs.

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TYPE Other Report YEAR 2017
DOIOSTI

Sandia National Laboratories, Tonopah Test Range Askania Tower (Building 02-00): Photographs and Written Historical and Descriptive Data

Ullrich, Rebecca A.

The Askania Tower (Building 02-00) was built in 1956 as part of the first wave of construction at the newly established Tonopah Test Range (TTR). Located at Station 2, near the primary target area at the range, the tower was one of the first four built to house Askania phototheodolites used in tracking test units dropped from aircraft. This report includes historical information, architectural information, sources of information, project information, maps, blueprints, and photographs.

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TYPE Other Report YEAR 2017
DOIOSTI

Stress Mapping in Glass-to-Metal Seals using Indentation Crack Lengths

Strong, Kevin T.; Buchheit, Thomas; Diebold, Thomas W.; Newton, Clay S.; Bencoe, Denise N.; Stavig, Mark E.; Jamison, Ryan D.

Predicting the residual stress which develops during fabrication of a glass-to-metal compression seal requires material models that can accurately predict the effects of processing on the sealing glass. Validation of the predictions requires measurements on representative test geometries to accurately capture the interaction between the seal materials during a processing cycle required to form the seal, which consists of a temperature excursion through the glass transition temperature of the sealing glass. To this end, a concentric seal test geometry, referred to as a short cylinder seal, consisting of a stainless steel shell enveloping a commercial sealing glass disk has been designed, fabricated, and characterized as a model validation test geometry. To obtain data to test/validate finite element (FE) stress model predictions of this geometry, spatially-resolved residual stress was calculated from the measured lengths of the cracks emanating from radially positioned Vickers indents in the glass disk portion of the seal. The indentation crack length method is described, and the spatially-resolved residual stress determined experimentally are compared to FE stress predictions made using a nonlinear viscoelastic material model adapted to inorganic sealing glasses and an updated rate dependent material model for 304L stainless steel. The measurement method is a first to achieve a degree of success for measuring spatially resolved residual stress in a glass-bearing geometry and a favorable comparison between measurements and simulation was observed.

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TYPE SAND Report YEAR 2017
DOIOSTI
Results 36001–36200 of 101,000
Results 36001–36200 of 101,000
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