Publications

Results 21001–21100 of 99,299

Search results

Jump to search filters

Material Property Determinations for Alluvium in Support of Source Physics Experiment

Broome, Scott T.; Barrow, Perry C.; Jaramillo, Johnny L.

Two blocks of alluvium were extensively tested at the Sandia National Laboratories Geomechanics laboratory. The alluvium blocks are intended to serve as surrogate material for mechanical property determinations to support the SPE DAG experimental series. From constant mean stress triaxial testing, strength failure envelopes were parameterized and are presented for each block. Modulus and stress relationships are given including bulk modulus versus mean stress, shear modulus versus shear stress, Young's modulus versus axial stress and Poisson's ratio versus axial stress. In addition, P-&S-wave velocities, and porosity, determined using helium porosimetry, were obtained on each block. Generally, both Young's modulus and Poisson's ratio increase with increasing axial stress, bulk modulus increases with increasing pressure, and increases more dramatically upon pore crush, shear modulus decreases with increasing shear stress and then appears to plateau. The Unconfined Compressive Strength for the BM is in the range of 0.5-0.6, and for SM in the range of 2.0-2.6 MPa. The confined compressive strength increases with increasing confining pressure, and the BM alluvium is significantly weaker compared to SM alluvium for mean stress levels above 8 MPa.

More Details
TYPE SAND Report YEAR 2019
DOIOSTI

Prediction and Inference of Multi-scale Electrical Properties of Geomaterials

Weiss, Chester J.; Beskardes, Gungor D.; Van Bloemen Waanders, Bart

Motivated by the need for improved forward modeling and inversion capabilities of geophysical response in geologic settings whose fine--scale features demand accountability, this project describes two novel approaches which advance the current state of the art. First is a hierarchical material properties representation for finite element analysis whereby material properties can be prescribed on volumetric elements, in addition to their facets and edges. Hence, thin or fine--scaled features can be economically represented by small numbers of connected edges or facets, rather than 10's of millions of very small volumetric elements. Examples of this approach are drawn from oilfield and near--surface geophysics where, for example, electrostatic response of metallic infastructure or fracture swarms is easily calculable on a laptop computer with an estimated reduction in resource allocation by 4 orders of magnitude over traditional methods. Second is a first-ever solution method for the space--fractional Helmholtz equation in geophysical electromagnetics, accompanied by newly--found magnetotelluric evidence supporting a fractional calculus representation of multi-scale geomaterials. Whereas these two achievements are significant in themselves, a clear understanding the intermediate length scale where these two endmember viewpoints must converge remains unresolved and is a natural direction for future research. Additionally, an explicit mapping from a known multi-scale geomaterial model to its equivalent fractional calculus representation proved beyond the scope of the present research and, similarly, remains fertile ground for future exploration.

More Details
TYPE SAND Report YEAR 2019
DOIOSTI

Data Architecture for Security Monitoring (Project Summary)

Kroeger, Thomas

The research has 2 thrusts: 1. new data architectures and tech-transfer-ready prototype tools that use write optimized data structures (WODS) to track real-world events, provide value to analysts, and support our cyber missions; and 2. algorithm research to address infinite streams of data, including expiration and sustainability.

More Details
TYPE SAND Report YEAR 2019
DOIOSTI

Sierra/SolidMechanics 4.54. Capabilities in Development

Veilleux, Michael G.; Beckwith, Frank; Belcourt, Kenneth; De Frias, Gabriel J.; Manktelow, Kevin; Merewether, Mark T.; Miller, Scott T.; Mosby, Matthew D.; Plews, Julia A.; Porter, Vicki L.; Shelton, Timothy R.; Thomas, Jesse D.; Tupek, Michael R.

This user’s guide documents capabilities in Sierra/SolidMechanics which remain “in-development” and thus are not tested and hardened to the standards of capabilities listed in Sierra/SM 4.54 User’s Guide. Capabilities documented herein are available in Sierra/SM for experimental use only until their official release. These capabilities include, but are not limited to, novel discretization approaches such as peridynamics and the reproducing kernel particle method (RKPM), numerical fracture and failure modeling aids such as the extended finite element method (XFEM) and /-integral, explicit time step control techniques, dynamic mesh rebalancing, as well as a variety of new material models and finite element formulations.

More Details
TYPE SAND Report YEAR 2019
DOIOSTI

Mechanical Testing Summary: Optimized Carbon Fiber Composites in Wind Turbine Blade Design

Miller, David A.; Samborsky, Daniel D.; Ennis, Brandon L.

The objective of the Optimized Carbon Fiber project is to assess the commercial viability to develop cost-competitive wind-specific carbon fiber composites to enable larger rotors for increased energy capture. Although glass fiber reinforcement is the primary structural material in wind blade manufacturing, utilization of carbon fiber has been identified as a key enabler for achieving larger rotors because of its higher specific stiffness (stiffness per unit mass), specific strength (strength per unit mass), and fatigue resistance in comparison to glass. This report contains the testing process and results from the mechanical characterization portion of the project. Low-cost textile carbon fiber materials are tested along with a baseline, commercial carbon fiber system common to the wind industry. Material comparisons are made across coupons of similar manufacturing and quality to assess the properties of the novel carbon fibers.

More Details
TYPE SAND Report YEAR 2019
DOIOSTI

Design Installation and Operation of the Vortex ART Platform

Gauntt, Nathan E.; Davis, Kevin; Repik, Jason J.; Brandt, James M.; Gentile, Ann C.; Hammond, Simon

ATS platforms are some of the largest, most complex, and most expensive computer systems installed in the United States at just a few major national laboratories. This milestone describes our recent efforts to procure, install, and test a machine called Vortex at Sandia National Laboratories that is compatible with the larger ATS platform Sierra at LLNL. In this milestone, we have 1) configured and procured a machine with similar hardware characteristics as Sierra ATS, 2) installed the machine, verified its physical hardware, and measured its baseline performance, and 3) demonstrated the machine's compatibility with Sierra ATS, and capacity for useful development and testing of Sandia computer codes (such as SPARC), including uses such as nightly regression testing workloads.

More Details
TYPE Other Report YEAR 2019
DOIOSTI

An Approach to Upscaling SPPARKS Generated Synthetic Microstructures of Additively Manufactured Metals

Mitchell, John A.

Additive manufacturing (AM) of metal parts can save time, energy, and produce parts that cannot otherwise be made with traditional machining methods. Near final part geometry is the goal for AM, but material microstructures are inherently different from those of wrought materials as they arise from a complex temperature history associated with the additive process. It is well known that strength and other properties of interest in engineering design follow from microstructure and temperature history. Because of complex microstructure morphologies and spatial heterogeneities, properties are heterogeneous and reflect underlying microstructure. This report describes a method for distributing properties across a finite element mesh so that effects of complex heterogeneous microstructures arising from additive manufacturing can be systematically incorporated into engineering scale calculations without the need for conducting a nearly impossible and time consuming effort of meshing material details. Furthermore, the method reflects the inherent variability in AM materials by making use of kinetic Monte Carlo calculations to model the AM process associated with a build.

More Details
TYPE SAND Report YEAR 2019
DOIOSTI
Results 21001–21100 of 99,299
Results 21001–21100 of 99,299