SEARCH · Search NASA

Results for “Material point method”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35

All sources NASA NTRS DOE OSTI

DOE OSTI2021

Elastic Wave Propagation in Curvilinear Coordinates with Mesh Refinement Interfaces by a Fourth Order Finite Difference Method

In this work, we develop a fourth order accurate finite difference method for the three dimensional elastic wave equation in isotropic media with the piecewise smooth material property. In our model, the material property can be discontinuous at curved interfaces. The governing equations are discretized in second order form on curvilinear meshes by using a fourth order finite difference operator satisfying a summation-by-parts property. The method is energy stable and high order accurate. The highlight is that mesh sizes can be chosen according to the velocity structure of the material so that computational efficiency is improved. At the mesh refinement interfaces with hanging nodes, physical interface conditions are imposed by using ghost points and interpolation. With a fourth order predictor-corrector time integrator, the fully discrete scheme is energy conserving. Numerical experiments are presented to verify the fourth order convergence rate and the energy conserving property.

58 GEOSCIENCES↗

DOE OSTI2015

Method to measure orientation of discontinuous fiber embedded in the polymer matrix from computerized tomography scan data

Usage of discontinuous glass fibers in injection and compression molded resin components is rapidly increasing to improve their mechanical properties. Since added fiber contributes to more strength along the fiber direction compared to transverse direction, the mechanical properties of such components strongly depend on the fiber orientation. Thus it is important to estimate the fiber orientation distribution in such materials. Here, we are presenting recently developed method to estimate fiber orientation from 3D image of fibers generated using micro CT scan. Typically the 3D images from CT scan are very large and it becomes difficult to separate each fiber and extract end point information. In this paper a novel method to address this challenge is presented. The micro-CT images were broken into finite volume, reducing data size, and then each fiber was reduced to its own center line, further reducing the data size, using Mimics Innovation Suite (Materialise NV). These 3D centerlines were then used to quantify the 2nd order orientation tensor. Our results from the proposed method are compared with the measurements using well established industry standard approach called method of ellipses for validation. The key challenges in estimating the fiber orientation are identified and future improvements are proposed.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Design Optimization for Printed Melt Wire Arrays Encapsulation

As part of the Nuclear Energy Enabling Technology (NEET) Advanced Sensor and Instrumentation (ASI) Program, Idaho National Laboratory (INL) has recently established in-house capabilities to fabricate and test new advanced-manufactured sensors for measuring peak irradiation temperature within a nuclear test reactor. Although methods of real-time temperature monitoring, such as thermocouples, may be used, the complexity of feedthroughs and attachments to collect real-time measurements greatly increases the cost of the experiment. Instead, passive monitoring techniques may be used for peak- temperature measurement that exploit the melting point of well-characterized materials (standard melt wires) to infer peak reactor temperatures. However, limited available space for instrumentation during experiments introduces an additional challenge. To accommodate this, INL has expanded its temperature- detection instrumentation capabilities to include advanced manufactured (AM) melt wires for peak irradiation temperature measurements. These melt wires can determine peak temperatures while also accommodate space limitations in irradiation experiments. In an effort to improve performance reliability of AM meltwire capabilities, a process was developed and tested to identify the significance of entrapping a high purity inert atmosphere within the packaging of printed melt wire arrays. The materials used in this study were aluminum, zinc, and tin encapsulated in high purity helium within a stainless steel (SS) 316 container. Tin, with a low melting point of approximately 230°C, Zn with a mid-melting point of approximately 420°C, and Al with a high melting point of approximately 660°C. This report describes the design, fabrication process, furnace testing and X-ray Computed Tomography (XCT) evaluation. Results show a successful outcome in creating an inert gas encapsulation and high-resolution evaluation methods.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2011

Line scanning thermography for rapid nondestructive inspection of large scale composites

As next generation structures are utilizing larger amounts of composite materials, a rigorous and reliable method is needed to inspect these structures in order to prevent catastrophic failure and extend service life. Current inspection methods, such as ultrasonic, generally require extended down time and man hours as they are typically carried out via point-by-point measurements. A novel Line Scanning Thermography (LST) System has been developed for the non-contact, large-scale field inspection of composite structures with faster scanning times than conventional thermography systems. LST is a patented dynamic thermography technique where the heat source and thermal camera move in tandem, which allows the continuous scan of long surfaces without the loss of resolution. The current system can inspect an area of 10 in{sup 2} per 1 second, and has a resolution of 0.05x0.03 in{sup 2}. Advanced data gathering protocols have been implemented for near-real time damage visualization and post-analysis algorithms for damage interpretation. The system has been used to successfully detect defects (delamination, dry areas) in fiber-reinforced composite sandwich panels for Navy applications, as well as impact damage in composite missile cases and armor ceramic panels.

42 ENGINEERING↗

DOE OSTI2016

Three-dimensional nanoscale characterisation of materials by atom probe tomography

The development of three-dimensional (3D), characterization techniques with high spatial and mass resolution is crucial for understanding and developing advanced materials for many engineering applications as well as for understanding natural materials. In recent decades, atom probe tomography (APT) which combines a point projection microscope and time-of-flight mass spectrometer has evolved to be an excellent characterization technique capable of providing 3D nanoscale characterization of materials with sub-nanometer scale spatial resolution, with equal sensitivity for all elements. This review discusses the current state as of beginning of the year 2016 of APT instrumentation, new developments in sample preparation methods, experimental procedures for different material classes, reconstruction of APT results, the current status of correlative microscopy, and application of APT for microstructural characterization in established scientific areas like structural materials as well as new applications in semiconducting nanowires, semiconductor devices, battery materials, catalyst materials, geological materials and biological materials. Finally, a brief perspective is given regarding the future of APT.

Atom Probe Tomography, characterization, microstru↗

DOE OSTI2019

Atomistic simulation of defect-dislocation interactions in concentrated solid-solution alloys

The interaction between point defects and dislocations plays a crucial role in governing material properties and microstructural evolutions under external stimuli, such as mechanical deformation and irradiation. Here, we present an atomistic study of the interactions between point defects and dislocations in concentrated solid-solution alloys (CSAs). Using molecular statics and kinetic Monte Carlo methods, we demonstrate that the strain energy and stress field distribution induced by a dislocation in CSAs are highly inhomogeneous along the dislocation line, which leads to heterogeneity of defect-dislocation interactions. Specifically, the interactions are spatially different and screened by the random arrangement of different elemental species. Furthermore, such localization of defect-dislocation interaction indicates that the “dislocation-bias” mechanism that is a driving force for radiation-induced void swelling can be suppressed in concentrated alloys.

36 MATERIALS SCIENCE↗

DOE OSTI2014

TU-C-BRE-10: A Streamlined Approach to EPID Transit Dosimetry

Purpose: To investigate the feasibility of a simple and efficient transit dosimetry method using the electronic portal imaging device (EPID) for dose delivery error detection and prevention. Methods: In the proposed method, 2D reference transit images are generated for comparison with online images acquired during treatment. Reference transit images are generated by convolving through-air EPID measurements of each field with pixel-specific kernels selected from a library of pre-calculated Monte Carlo pencil kernels of varying radiological thickness. The kernel used for each pixel is selected based on the calculated radiological thickness of the patient along a line joining the pixel and the virtual source. The accuracy of the technique was evaluated in flat homogeneous and heterogeneous plastic water phantoms, a heterogeneous cylindrical phantom, and an anthropomorphic head phantom. Gamma criteria of 3%/3 mm was used to quantify the accuracy of the technique for the various cases. Results: An average of 99.9% and 99.7% of the points in the comparison between the measured and predicted images passed a 3%/3mm gamma for the homogeneous and heterogeneous plastic water phantoms, respectively. 97.1% of the points passed for the analysis of the heterogeneous cylindrical phantom. For the anthropomorphic head phantom, an average of 97.8% of points passed the 3%/3mm gamma criteria for all field sizes. Failures were observed primarily in areas of drastic thickness or material changes and at the edges of the fields. Conclusion: The data suggest that the proposed transit dosimetry method is a feasible approach to in vivo dose monitoring. Future research efforts could include implementation for more complex fields and sensitivity testing of the method to setup errors and changes in anatomy. Oncology Data Systems provided partial funding support but did not participate in the collection or analysis of data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2015

Nuclear heating measurements by in-pile calorimetry: prospective works for a microsensor design

Since 2009 works have been performed in the framework of joint research programs between CEA and Aix-Marseille University. The main aim of these programs is to design and develop in-pile instrumentations, advanced calibration procedure and accurate measurement methods in particular for the new Material Testing Reactor (MTR) under construction in the South of France: Jules Horowitz Reactor (JHR). One major sensor is a specific radiometric calorimeter, which was studied out-of-pile from a thermal point of view and in-pile during irradiation campaigns. This sensor type is dedicated to measurements of nuclear heating (energy deposition rate per mass unit induced by interactions between nuclear rays and matter) inside experimental channels of MTRs. This kind of in-pile calorimeter corresponds to heat flux calorimeter exchanging with the external cooling fluid. This thermal running mode allows the establishment of steady thermal conditions inside the sensor to carry out online continuous measurements inside the reactor (core or reflector). Two main types of calorimeters exist. The first type consists of a single cell calorimeter. It is divided into a sample of material to be tested and a jacket instrumented with two thermocouples or a single thermocouple (Gamma Thermometer). The second, called a differential calorimeter, is composed of two superposed twin cells (a measurement cell containing a sample of material, and a reference cell to remove the heating of the cell body) instrumented with four thermocouples and two electrical heaters. Contrary to a single-cell calorimeter, a differential calorimeter allows the compensation of the parasite nuclear heating of the sensor body or jacket. Moreover, it possesses interesting advantages: thanks to the heaters embedded in the cells, three different measurement methods can be applied during irradiations to quantify nuclear heating. The first one is based on the use of out-of-pile calibration curves obtained by generating a heat source by the Joule Effect inside each calorimetric cell. The second one is a zero method consisting in cancelling the difference in cell responses with an additional energy into the reference cell. The last measurement method is based on current additions in the two calorimetric cells. However, one drawback of the existing differential calorimeter is the size of the sensor: a great length equal to 220 mm and a diameter equal to 18 mm. This current size leads to measurement limitations. This paper will begin with a presentation of these measurement limitations from a bibliographic state. Each limitation will be detailed and in particular in the case of a high nuclear heating level expected, for instance, inside the JHR's core at its highest nominal power. The second part of the paper will develop the scientific skills of each partner in heat sciences, micro technology and nuclear physics necessary to design a new calorimetric micro-system: the advantages of studied microelements such as micro-thermocouples, micro- fluxmeters and micro-heaters will be presented. The last part will discuss preliminary designs. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2013

Retrospective Cohort Study of Bronchial Doses and Radiation-Induced Atelectasis After Stereotactic Body Radiation Therapy of Lung Tumors Located Close to the Bronchial Tree

Purpose: To evaluate the dose–response relationship between radiation-induced atelectasis after stereotactic body radiation therapy (SBRT) and bronchial dose. Methods and Materials: Seventy-four patients treated with SBRT for tumors close to main, lobar, or segmental bronchi were selected. The association between incidence of atelectasis and bronchial dose parameters (maximum point-dose and minimum dose to the high-dose bronchial volume [ranging from 0.1 cm{sup 3} up to 2.0 cm{sup 3}]) was statistically evaluated with survival analysis models. Results: Prescribed doses varied between 4 and 20 Gy per fraction in 2-5 fractions. Eighteen patients (24.3%) developed atelectasis considered to be radiation-induced. Statistical analysis showed a significant correlation between the incidence of radiation-induced atelectasis and minimum dose to the high-dose bronchial volumes, of which 0.1 cm{sup 3} (D{sub 0.1cm3}) was used for further analysis. The median value of D{sub 0.1cm3} (α/β = 3 Gy) was EQD{sub 2,LQ} = 147 Gy{sub 3} (range, 20-293 Gy{sub 3}). For patients who developed atelectasis the median value was EQD{sub 2,LQ} = 210 Gy{sub 3}, and for patients who did not develop atelectasis, EQD{sub 2,LQ} = 105 Gy{sub 3}. Median time from treatment to development of atelectasis was 8.0 months (range, 1.1-30.1 months). Conclusion: In this retrospective study a significant dose–response relationship between the incidence of atelectasis and the dose to the high-dose volume of the bronchi is shown.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2014

Residual Tumor After Neoadjuvant Chemoradiation Outside the Radiation Therapy Target Volume: A New Prognostic Factor for Survival in Esophageal Cancer

Purpose/Objective(s): The aim of this study was to analyze the accuracy of gross tumor volume (GTV) delineation and clinical target volume (CTV) margins for neoadjuvant chemoradiation therapy (neo-CRT) in esophageal carcinoma at pathologic examination and to determine the impact on survival. Methods and Materials: The study population consisted of 63 esophageal cancer patients treated with neo-CRT. GTV and CTV borders were demarcated in situ during surgery on the esophagus, using anatomical reference points to provide accurate information regarding tumor location at pathologic evaluation. To identify prognostic factors for disease-free survival (DFS) and overall survival (OS), a Cox regression analysis was performed. Results: After resection, macroscopic residual tumor was found outside the GTV in 7 patients (11%). Microscopic residual tumor was located outside the CTV in 9 patients (14%). The median follow-up was 15.6 months. With multivariate analysis, only microscopic tumor outside the CTV (hazard ratio [HR], 4.96; 95% confidence interval [CI], 1.03-15.36), and perineural growth (HR, 5.77; 95% CI, 1.27-26.13) were identified as independent prognostic factors for OS. The 1-year OS was 20% for patients with tumor outside the CTV and 86% for those without (P<.01). For DFS, microscopic tumor outside the CTV (HR, 5.92; 95% CI, 1.89-18.54) and ypN+ (HR, 3.36; 95% CI, 1.33-8.48) were identified as independent adverse prognostic factors. The 1-year DFS was 23% versus 77% for patients with or without tumor outside the CTV (P<.01). Conclusions: Microscopic tumor outside the CTV is associated with markedly worse OS after neo-CRT. This may either stress the importance of accurate tumor delineation or reflect aggressive tumor behavior requiring new adjuvant treatment modalities.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2013

Ionothermal synthesis of uranyl compounds that incorporate imidazole derivatives

Ionothermal reactions of uranyl nitrate with various salts in methylimidazolium-based ionic liquids have produced single crystals of three uranyl compounds that incorporate imidazole derivatives as charge-balancing cations. (C{sub 4}H{sub 7}N{sub 2})[(UO{sub 2})(PO{sub 3}F)(F)] (1) crystallizes in space group C2, a=17.952(1) A, b=6.9646(6) A, c=8.5062(7) A, {beta}=112.301(1) Degree-Sign , (C{sub 6}H{sub 11}N{sub 2}){sub 2}[(UO{sub 2})(SO{sub 4}){sub 2}] (2) crystallizes in space group C2/c, a=31.90(1) A, b=9.383(5) A, c=13.770(7) A, {beta}=93.999(7) Degree-Sign and (C{sub 6}H{sub 11}N{sub 2})[(UO{sub 2}){sub 2}(PO{sub 4})(HPO{sub 4}) (3) crystallizes in space group P2{sub 1}/n, a=9.307(2), b=18.067(4), c=9.765(2), {beta}=93.171(2). The U{sup 6+} cations are present as (UO{sub 2}){sup 2+} uranyl ions coordinated by three O atoms and two F atoms in 1 and five O atoms in 2 and 3 to give pentagonal bipyramids. The structural unit in 1 is composed of F-sharing dimers of uranyl pentagonal bipyramids linked into sheets through corner-sharing fluorophosphate tetrahedra. The structural unit in 2 is composed of uranyl pentagonal bipyramids with one chelating sulfate tetrahedron linked into chains by three other corner-sharing sulfate tetrahedra. In 3, the structural unit is composed of chains of uranyl pentagonal bipyramids linked into sheets through edge- and corner-sharing phosphate and hydrogen phosphate tetrahedra. N-methylimidazolium cations occupy the interstitial space between the uranyl fluorophosphate sheets in 1, whereas 1-ethyl-3-methylimidazolium cations link the uranyl sulfate and phosphate units in 2 and 3 into extended structures. - Graphical abstract: The synthesis of uranyl compounds by ionothermal treatment is explored, and provides three novel compounds and insights concerning the role of water in controlling the structural units. Highlights: Black-Right-Pointing-Pointer Ionothermal syntheses have produced three new uranyl compounds. Black-Right-Pointing-Pointer Imidazole derivatives are incorporated as charge-balancing agents. Black-Right-Pointing-Pointer X-ray and spectroscopic analyses reveal variability between imidazole derivatives. Black-Right-Pointing-Pointer This method offers synthetic insight in the absence of water at low temperatures.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Joining Dissimilar Materials Using Friction Stir Scribe Technique

Development of a robust and cost-effective method of joining dissimilar materials could provide a critical pathway to enable widespread use of multi-material designs and components in mainstream industrial applications. The use of multi-material components such as steel-aluminum and aluminum-polymer would allow design engineers to optimize material utilization based on service requirements and could often lead to weight and cost reductions. However, producing an effective joint between materials with vastly different thermal, microstructural, and deformation responses is highly problematic using conventional joining and/or fastening methods. This is especially challenging in cost sensitive, high volume markets that largely rely on low cost joining solutions. Friction stir scribe technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like magnesium and aluminum to high temperature materials like steel and titanium. Viable joints between polymer composites and metal can also be made using this method. This paper will present the state of the art, progress made, and challenges associated with this innovative derivative of friction stir welding in reference to joining dissimilar metals and polymer/metal combinations.

Upadhyay, Piyush↗

DOE OSTI2023

High efficiency, high-current laser-driven electron injector (CRADA Final Report)

Owing to ultra-high fields sustainable in a plasma, laser-plasma accelerator technology enables compact, high-brightness, sources of electron beams. This work investigates novel electron injection methods. Key to this research is to understand laser energy and pointing stability and to develop methods and techniques to control fluctuations. This project benefits other areas of scientific inquiry by developing a high-repetition rate, high-brightness electron source for probing materials and ultra-fast processes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2023

High efficiency, high-current laser-driven electron injector (CRADA Final Report)

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1975

Chemical equilibrium of ablation materials including condensed species

Equilibrium is determined by finding chemical composition with minimum free energy. Method of steepest descent is applied to quadratic representation of free-energy surface. Solution is initiated by selecting arbitrary set of mole fractions, from which point on free-energy surface is computed.

Stroud, C. W.↗

NASA NTRS2001

Structures for the 3rd Generation Reusable Concept Vehicle

A major goal of NASA is to create an advance space transportation system that provides a safe, affordable highway through the air and into space. The long-term plans are to reduce the risk of crew loss to 1 in 1,000,000 missions and reduce the cost of Low-Earth Orbit by a factor of 100 from today's costs. A third generation reusable concept vehicle (RCV) was developed to assess technologies required to meet NASA's space access goals. The vehicle will launch from Cape Kennedy carrying a 25,000 lb. payload to the International Space Station (ISS). The system is an air breathing launch vehicle (ABLV) hypersonic lifting body with rockets and uses triple point hydrogen and liquid oxygen propellant. The focus of this paper is on the structural concepts and analysis methods used in developing the third generation reusable launch vehicle (RLV). Member sizes, concepts and material selections will be discussed as well as analysis methods used in optimizing the structure. Analysis based on the HyperSizer structural sizing software will be discussed. Design trades required to optimize structural weight will be presented.

Hrinda, Glenn A.↗

NASA NTRS2012

Evaluation of Delamination Growth Characterization Methods Under Mode I Fatigue Loading

Reliable delamination characterization data for laminated composites are needed for input to analytical models of structures to predict delamination. The double-cantilevered beam (DCB) specimen is used with laminated composites to measure fracture toughness, G(sub Ic), delamination onset strain energy release rate, and growth rate data under cyclic loading. In the current study, DCB specimens of IM7/8552 graphite/epoxy supplied by two different manufacturers were tested in static and fatigue to compare the measured characterization data from the two sources, and to evaluate a proposed ASTM standard for generating Paris Law equations. Static results were used to generate compliance calibration constants for the fatigue data, and a delamination resistance curve, G(sub IR), which was used to determine the effects of fiber-bridging on delamination growth. Specimens were tested in fatigue at a cyclic G(sub Imax) level equal to 50, 40 or 30% of G(sub Ic), to determine a delamination onset curve and delamination growth rate. The delamination onset curve equations had similar exponents and the same trends. Delamination growth rate was calculated by fitting a Paris Law to the da/dN versus G(sub Imax) data. Both a 2-point and a 7-point data reduction method were used and the Paris Law equations were compared. To determine the effects of fiber-bridging, growth rate results were normalized by the delamination resistance curve for each material and compared to the non-normalized results. Paris Law exponents were found to decrease by 31% to 37% due to normalizing the growth data. Normalizing the data also greatly reduced the amount of scatter between the different specimens. Visual data records from the fatigue testing were used to calculate individual compliance calibration constants from the fatigue data for some of the specimens. The resulting da/dN versus G(sub Imax) plots showed much improved repeatability between specimens. Gretchen

Murri, Gretchen B.↗

DOE OSTI2015

Design and performance testing of a novel far field Gamma system to assay radioactive waste in 400 and 200 litre drums - 15339

A Far Field Gamma ray Measurement system has been developed for measuring and assaying both 400 and 200 litre waste drums with a wide range of activity at nuclear power stations. These include radioactive waste drums with surface dose-rates of less than 2 mSv/h (200 mrem/h) and, at the higher range of activity, 400 litre drums with surface dose-rates of up to 50 mSv/h (5 rem/h). The assay system incorporates an electro-mechanically cooled high purity Germanium profile detector and advanced digital spectroscopic analysis electronics. A novel optimised conical-trapezoidal collimator has been incorporated to reduce the effect of the radioactive background in addition to the conventional detector lead shield with tin and copper graded lining to reduce the effect of lead X-rays. Two features have been incorporated to reduce detector dead time and maintain detector resolution when measuring high activity drums. The first is the inclusion of two automated tungsten filters of different thickness as an integral part of the detector collimator. The filters are used in conjunction with an automated rail system on which the detector platform is mounted. The detector can be positioned at different distances from the drum surface in order to reduce detector dead time. The deployment of the filters and the adjustment of the drum - detector position are automatically controlled based on a user defined dose-rate limit table. The data is provided by two Geiger-Muller dose-rate detectors, which are used to measure the drum surface dose-rate. This data is subsequently used to adjust the detector position and in cases of higher dose-rate deploy one or other of the tungsten filters. The drum rotation platform incorporates a load cell to determine drum weight and hence the drum density. This information is used to calculate an attenuation correction based on the assumption of uniform drum density and uniform distribution of activity within the drum. Where the waste drums have a more complicated and known regular internal structure, such as a small radioactive region surrounded by an annulus of shielding material, the analysis algorithms incorporated into the far field geometry and attenuation correction spectroscopic data analysis code are able to make a more accurate determination of drum activity than would be possible assuming a completely uniform drum. The detector energy and efficiency calibration is achieved using a point source with multiple gamma ray energy peaks. The response of the high purity Germanium detector is also modelled using the Monte Carlo Neutron Photon code and the model is benchmarked using the measured point source calibration data. The performance of the instrument has been determined for a range of uniform density matrix drums containing a set of Eu-152 line or rod sources located in re-entrant tubes positioned on an equal volume basis. When rotated, the test drums with volume distributed line sources simulate waste drums of different density each with a uniformly distributed radioactive source. The measurements have been validated using Monte Carlo simulations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗