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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Assessment of the hydromechanical higher-order MPM for the simulation of geotechnical problems

The Material Point Method (MPM) has been increasingly used to simulate large strain deformations. Linear interpolation functions are commonly used to perform the spatial integration. It is well-known that the discontinuities in the interpolation function derivatives induce shock-like artifacts known as ‘cell-crossing’ error. These errors compound with volumetric locking errors when used with hydromechanical formulations for porous media, where different velocity fields are used for each phase. The capabilities of higher-order MPM frameworks have not been explored for real-scale geotechnical problems. As such, this paper aims to assess, validate, and further discuss a higher-order B-spline MPM (BS-MPM) framework. First, the BS-MPM framework is verified against the large-strain oedometer consolidation problem. Second, the framework is validated against a real-scale slope failure experiment triggered by pore water pressure recharge. Landslide features that are captured using the higher-order framework are specifically highlighted, and results (e.g., pore water pressure and deformation) are validated with field measurements. A generally convergent numerical solution is observed when using cubic interpolation functions. Third, a footing penetration problem is simulated using the multi-patch BS-MPM. Trends are examined with respect to penetration velocity and variation in hydraulic conductivity. The BS-MPM framework ultimately presents a stabilized numerical solution that captures plausible hydromechanical interaction trends important in geotechnical engineering applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Kelvin

Kelvin is a multiphysics sintering simulation software that uses the material point method to simulate the thermomechanical behavior of metal parts.

Billings, JayJ↗
DOE OSTI2010

Development, sensitivity analysis, and uncertainty quantification of high-fidelity arctic sea ice models.

Arctic sea ice is an important component of the global climate system and due to feedback effects the Arctic ice cover is changing rapidly. Predictive mathematical models are of paramount importance for accurate estimates of the future ice trajectory. However, the sea ice components of Global Climate Models (GCMs) vary significantly in their prediction of the future state of Arctic sea ice and have generally underestimated the rate of decline in minimum sea ice extent seen over the past thirty years. One of the contributing factors to this variability is the sensitivity of the sea ice to model physical parameters. A new sea ice model that has the potential to improve sea ice predictions incorporates an anisotropic elastic-decohesive rheology and dynamics solved using the material-point method (MPM), which combines Lagrangian particles for advection with a background grid for gradient computations. We evaluate the variability of the Los Alamos National Laboratory CICE code and the MPM sea ice code for a single year simulation of the Arctic basin using consistent ocean and atmospheric forcing. Sensitivities of ice volume, ice area, ice extent, root mean square (RMS) ice speed, central Arctic ice thickness, and central Arctic ice speed with respect to ten different dynamic and thermodynamic parameters are evaluated both individually and in combination using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). We find similar responses for the two codes and some interesting seasonal variability in the strength of the parameters on the solution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Modeling detonation with CartaBlanca simulations

The accurate modeling of high explosive (HE) detonation and the con- sequent large solid deformation, failure, plastic flow, porosity growth, and shock wave propagation is important because simulations can capture spatial and temporal features that experimental diagnostics cannot capture. However, the simulation of the explosive event poses challenges to a computational scientist. These include the accurate modeling of ductile damage, crack formation, plastic deformation, as well as physical and nu- merical instabilities. The material response can be history-dependent and subject to large material deformation. Our research simulates the impact of a high explosive (Detasheet) onto a tantulum metal plate. We performed the simulations using CartaBlanca at different mesh resolutions. We decided the study would be impactful if we perform the simulations with the Material Point Method. Differences were observed at the different mesh resolutions in velocity and nodal stress magnitude, so increased mesh resolutions may be required. In addition, the Discontinuous Galerkin method would be needed to account for the large gas expansion.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2010

Arctic Sea ice model sensitivities.

Arctic sea ice is an important component of the global climate system and, due to feedback effects, the Arctic ice cover is changing rapidly. Predictive mathematical models are of paramount importance for accurate estimates of the future ice trajectory. However, the sea ice components of Global Climate Models (GCMs) vary significantly in their prediction of the future state of Arctic sea ice and have generally underestimated the rate of decline in minimum sea ice extent seen over the past thirty years. One of the contributing factors to this variability is the sensitivity of the sea ice state to internal model parameters. A new sea ice model that holds some promise for improving sea ice predictions incorporates an anisotropic elastic-decohesive rheology and dynamics solved using the material-point method (MPM), which combines Lagrangian particles for advection with a background grid for gradient computations. We evaluate the variability of this MPM sea ice code and compare it with the Los Alamos National Laboratory CICE code for a single year simulation of the Arctic basin using consistent ocean and atmospheric forcing. Sensitivities of ice volume, ice area, ice extent, root mean square (RMS) ice speed, central Arctic ice thickness,and central Arctic ice speed with respect to ten different dynamic and thermodynamic parameters are evaluated both individually and in combination using the Design Analysis Kit for Optimization and Terascale Applications (DAKOTA). We find similar responses for the two codes and some interesting seasonal variability in the strength of the parameters on the solution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Material point generation from an STL file

In this short note we describe a method for generating material points from a file in the stere olithography (STL) format commonly used in computer aided design (CAD), 3-D printing, and computer aided manufacturing applications. In this file format the surface of an object is described by triangles in three-dimensional space. The coordinates of the triangle vertexes are provided in the file. In this note we assume that the object of interest is inside of the enclosing set of triangles. Similar methods can also be used to generate material points outside of the enclosing triangles.

42 ENGINEERING↗
DOE OSTI2014

NSR&D FY14 Final Report: Friction/Impact Modeling

The LANL-developed CartaBlanca code uses advanced techniques, including the Dual Domain Material Point (DDMP) method, to calculate fluid, solid motions and fluid-structure interactions. In the last year we have implemented the ViscoSCRAM material model in CartaBlanca based on Clements’ Abaqus-Explicit Finite Element implementation. In this fiscal year, we study numerical properties of this implementation. To consider coupled mechanical, thermal and chemical effects, we have implemented Henson’s HE decomposition model to couple with the thermal and mechanical packages in CartaBlanca. We have also developed porous media flow modules to consider heat convection effects of the reaction product gas inside pores of HE. The next immediate step is to perform numerical simulations to study interactions among these different mechanisms. We have started such calculation and obtained interesting initial results at the end of this fiscal year.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

NSR&D FY15 Final Report. Modeling Mechanical, Thermal, and Chemical Effects of Impact

The main goal of this project is to develop a computer model that explains and predicts coupled mechanical, thermal and chemical responses of HE under impact and friction insults. The modeling effort is based on the LANL-developed CartaBlanca code, which is implemented with the dual domain material point (DDMP) method to calculate complex and coupled thermal, chemical and mechanical effects among fluids, solids and the transitions between the states. In FY 15, we have implemented the TEPLA material model for metal and performed preliminary can penetration simulation and begun to link with experiment. Currently, we are working on implementing a shock to detonation transition (SDT) model (SURF) and JWL equation of state.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Treatment of near-incompressibility in meshfree and immersed-particle methods

We propose here new projection methods for treating near-incompressibility in small and large deformation elasticity and plasticity within the framework of particle and meshfree methods. Using the $\bar{B}$ and $\bar{F}$ techniques as our point of departure, we develop projection methods for the conforming reproducing kernel method and the immersed-particle or material point-like methods. The methods are based on the projection of the dilatational part of the appropriate measure of deformation onto lower-dimensional approximation spaces, according to the traditional $\bar{B}$ and $\bar{F}$ approaches, but tailored to meshfree and particle methods. The presented numerical examples exhibit reduced stress oscillations and are free of volumetric locking and hourglassing phenomena.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

In-situ stress analysis with X-Ray diffraction for yield locus characterization of sheet metals

A main problem in the field of sheet metal characterization is the inhomogeneous plastic deformation in the gauge regions of specimens which causes the analytically calculated stresses to differ from the sought state of stress acting in the middle of the gauge region. To overcome this problem, application of X-Ray diffraction is analyzed. For that purpose a mobile X-ray diffractometer and an optical strain measurement system are mounted on a universal tensile testing machine. This enables the recording of the whole strain and stress history of a material point. The method is applied to uniaxial tension tests, plane strain tension tests and shear tests to characterize the interstitial free steel alloy DC06. The applicability of the concepts of stress factors is verified by uniaxial tension tests. The experimentally obtained values are compared with the theoretical values calculated with crystal elasticity models utilizing the orientation distribution functions (ODF). The relaxation problem is addressed which shows itself as drops in the stress values with the strain kept at a constant level. This drop is analyzed with elasto-viscoplastic material models to correct the measured stresses. Results show that the XRD is applicable to measure the stresses in sheet metals with preferred orientation. The obtained yield locus is expressed with the Yld2000–2D material model and an industry oriented workpiece is analyzed numerically. The comparison of the strain distribution on the workpiece verifies the identified material parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Detection of sub-500-μm cracks in multicrystalline silicon wafer using edge-illuminated dark-field imaging to enable thin solar cell manufacturing

High capital expenditures associated with manufacturing thin silicon wafers make it difficult for the industry to scale up and prevent novel technologies from entering the market. Thin wafers fail largely due to breakage during solar cell processing and handling. One of the root causes for breakage is sub-mm edge cracks in the silicon wafer, and these cracks cannot be reliably detected by most commercially-available crack detection tools. In this work, we first investigate the correlation between wafer thickness and critical crack length, and explain the importance of detecting sub-500-μm edge cracks as the wafer thickness is reduced. Secondly, we extend our previous work of micro-crack detection to demonstrate an edge illumination technique using a near-infrared laser to image edge cracks less than 500 μm in length in multicrystalline silicon. Thirdly, we investigate two fundamental edge illumination mechanisms based on dark-field imaging; namely, direct and vicinal illumination. We will then compare these methods to a state-of-the-art rear illumination method. The advantages and disadvantages of both illumination methods are presented and provide an in-depth analysis of light-crack interaction. In particular, we find that the robustness of vicinal illumination is due to diffuse reflectance. The diffuse reflectance has less dependence on crack configurations, while direct illumination has more dependence on the crack configurations because it utilizes specular reflectance. Our results show that our proposed prototype can detect sub-mm edge cracks in multicrystalline silicon wafers, which is an important step in enabling thin silicon wafer manufacturing.

14 SOLAR ENERGY↗
DOE OSTI2021

Simulation of dynamic crystal plasticity with a Lagrangian discontinuous Galerkin hydrodynamic method

Here we present a new Lagrangian modal discontinuous Galerkin (DG) hydrodynamic method that supports a dynamic dislocation based crystal plasticity model for simulating the mechanical behavior of crystallographic materials, both single crystal and polycrystalline, under dynamic conditions. A modal DG approach is used to evolve fields relevant to conservation laws. These fields are approximated by Taylor series polynomials of varying degree. These polynomials describe macro-scale hydrodynamic behavior while their evolution is determined by evaluating the dynamic crystal plasticity model at material points within the element. The dynamic crystal plasticity model is sensitive to the time increment size, with too large of time increments leading to instability in the model. To mitigate this, the temporal evolution of the dynamic crystal plasticity model is achieved with the combination of a sub-incrementing scheme with Heun’s third-order time integration scheme, which is also used to temporally evolve the governing equations. The implementation of the dynamic crystal plasticity model within the DG framework is tested using a 2D approximation of the Taylor impact test with a single crystal material, using quadratic elements that have faces that can bend. In addition to the standard continuous material modeling, we propose a new simulation method that would represent the heterogeneous behavior of polycrystalline microstructures within an element by varying the position and material properties of the material points within the element. This method is demonstrated using random orientation distributions on materials points that are arranged in both structured and random configurations.

42 ENGINEERING↗
NASA NTRS2005

Laser And Nonlinear Optical Materials For Laser Remote Sensing

NASA remote sensing missions involving laser systems and their economic impact are outlined. Potential remote sensing missions include: green house gasses, tropospheric winds, ozone, water vapor, and ice cap thickness. Systems to perform these measurements use lanthanide series lasers and nonlinear devices including second harmonic generators and parametric oscillators. Demands these missions place on the laser and nonlinear optical materials are discussed from a materials point of view. Methods of designing new laser and nonlinear optical materials to meet these demands are presented.

Barnes, Norman P.↗
DOE OSTI2014

SU-E-T-603: Analysis of Optical Tracked Head Inter-Fraction Movements Within Masks to Access Intracranial Immobilization Techniques in Proton Therapy

Purpose: We present a quantitative methodology utilizing an optical tracking system for monitoring head inter-fraction movements within brain masks to assess the effectiveness of two intracranial immobilization techniques. Methods and Materials: A 3-point-tracking method was developed to measure the mask location for a treatment field at each fraction. Measured displacement of mask location to its location at first fraction is equivalent to the head movement within the mask. Head movements for each of treatment fields were measured over about 10 fractions at each patient for seven patients; five treated in supine and two treated in prone. The Q-fix Base-of-Skull head frame was used in supine while the CIVCO uni-frame baseplate was used in prone. Displacements of recoded couch position of each field post imaging at each fraction were extracted for those seven patients. Standard deviation (S.D.) of head movements and couch displacements was scored for statistical analysis. Results: The accuracy of 3PtTrack method was within 1.0 mm by phantom measurements. Patterns of head movement and couch displacement were similar for patients treated in either supine or prone. In superior-inferior direction, mean value of scored standard deviations over seven patients were 1.6 mm and 3.4 mm for the head movement and the couch displacement, respectively. The result indicated that the head movement combined with a loose fixation between the mask-to-head frame results large couch displacements for each patient, and also large variation between patients. However, the head movement is the main cause for the couch displacement with similar magnitude of around 1.0 mm in anterior-posterior and lateral directions. Conclusions: Optical-tracking methodology independently quantifying head movements could improve immobilization devices by correctly acting on causes for head motions within mask. A confidence in the quality of intracranial immobilization techniques could be more efficient by eliminating the need for frequent imaging.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Bright and durable field emission source derived from refractory taylor cones

A method of producing field emitters having improved brightness and durability relying on the creation of a liquid Taylor cone from electrically conductive materials having high melting points. The method calls for melting the end of a wire substrate with a focused laser beam, while imposing a high positive potential on the material. The resulting molten Taylor cone is subsequently rapidly quenched by cessation of the laser power. Rapid quenching is facilitated in large part by radiative cooling, resulting in structures having characteristics closely matching that of the original liquid Taylor cone. Frozen Taylor cones thus obtained yield desirable tip end forms for field emission sources in electron beam applications. Regeneration of the frozen Taylor cones in-situ is readily accomplished by repeating the initial formation procedures. The high temperature liquid Taylor cones can also be employed as bright ion sources with chemical elements previously considered impractical to implement.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Structure, growth and properties of a novel polar material, KSr{sub 4}B{sub 3}O{sub 9}

A novel polar material, KSr{sub 4}B{sub 3}O{sub 9}, has been obtained by the high temperature solution method for the first time. It crystallizes in the polar space group Ama2. The material exhibits a three-dimensional structure consisting of interconnecting KO{sub 10} groups, SrO{sub x} (x=8, 9) units and isolated BO{sub 3} triangles. DSC/TG curve shows that KSr{sub 4}B{sub 3}O{sub 9} melts incongruently. The calculated band structures and the density of states of KSr{sub 4}B{sub 3}O{sub 9} suggest that its direct gap is 3.897 eV. The absorption spectrum indicates the absorption edge of KSr{sub 4}B{sub 3}O{sub 9} is about 302 nm. It produces SHG intensity about as large as that of KH{sub 2}PO{sub 4} (KDP) and is phase matchable. - Graphical abstract: Viewed along the c-axis, B(2)O{sub 3} triangles and B(3)O{sub 3} triangles are parallel with the (0 1 0) face and opposite to each other. However, all the B(1)O{sub 3} triangles have the same direction along the c-axis. So the main SHG efficiency of the compound comes from B(1)O{sub 3} triangles according to the anion group theory. Highlights: Black-Right-Pointing-Pointer A polar material, KSr{sub 4}B{sub 3}O{sub 9}, has been obtained by high temperature solution method. Black-Right-Pointing-Pointer The material consists of KO{sub 10} units, SrO{sub x}(x=8, 9) units and isolated BO{sub 3} units. Black-Right-Pointing-Pointer KSr{sub 4}B{sub 3}O{sub 9} produces SHG intensity as large as that of KDP and is phase matchable. Black-Right-Pointing-Pointer The absorption edge of KSr{sub 4}B{sub 3}O{sub 9} is about 302 nm.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Fabrication of functional nanomaterials using flame assisted spray pyrolysis

Flame assisted spray pyrolysis (FASP) is a class of synthesis method for nanomaterials fabrication. The ability to control nanomaterials characteristics and easy to be-scaled up are the main features of FASP. The crystallinity and particles size of the prepared nanomaterials can be easily controlled by variation of fuel flow rate. The precursor concentration, carrier gas flow rate, and carrier gas can be also used to control the prepared nanomaterials. Energy related nanomaterials preparation uses as the example case in FASP application. These material are yttrium aluminum garnet (YAG:Ce) and tungsten oxide (WO{sub 3}). It needs strategies to produce these materials into nano-sized order. YAG:Ce nanoparticles only can be synthesized by FASP using the urea addition. The decomposition of urea under high temperature of flame promotes the breakage of YAG:Ce particles into nanoparticles. In the preparation of WO{sub 3}, the high temperature flame can be used to gasify WO{sub 3} solid material. As a result, WO{sub 3} nanoparticles can be prepared easily. Generally, to produce nanoparticles via FASP method, the boiling point of the material is important to determine the strategy which will be used.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗