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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Injection-Molded Long-Fiber Thermoplastic Composites: From Process Modeling to Prediction of Mechanical Properties

This article illustrates the predictive capabilities for long-fiber thermoplastic (LFT) composites that first simulate the injection molding of LFT structures by Autodesk® Simulation Moldflow® Insight (ASMI) to accurately predict fiber orientation and length distributions in these structures. After validating fiber orientation and length predictions against the experimental data, the predicted results are used by ASMI to compute distributions of elastic properties in the molded structures. In addition, local stress-strain responses and damage accumulation under tensile loading are predicted by an elastic-plastic damage model of EMTA-NLA, a nonlinear analysis tool implemented in ABAQUS® via user-subroutines using an incremental Eshelby-Mori-Tanaka approach. Predicted stress-strain responses up to failure and damage accumulations are compared to the experimental results to validate the model.

Injection molding, long fiber thermoplastic, proce↗
DOE OSTI2015

FIBER ORIENTATION IN INJECTION MOLDED LONG CARBON FIBER THERMOPLASTIC COMPOSITES

A set of edge-gated and center-gated plaques were injection molded with long carbon fiber-reinforced thermoplastic composites, and the fiber orientation was measured at different locations of the plaques. Autodesk Simulation Moldflow Insight (ASMI) software was used to simulate the injection molding of these plaques and to predict the fiber orientation, using the anisotropic rotary diffusion and the reduced strain closure models. The phenomenological parameters of the orientation models were carefully identified by fitting to the measured orientation data. The fiber orientation predictions show very good agreement with the experimental data.

carbon fiber↗
DOE OSTI2019

A Balanced Approach to Molded Case Circuit Breaker Maintenance

Abstract – NFPA 70E mandates that "overcurrent devices shall be maintained in accordance with the manufacturer's instructions or industry consensus standards". At our laboratory this mandate is law, because 10 CFR 851 requires adherence to NFPA 70 and 70E. This begs the question, exactly what are those manufacturer's instructions, and what do the industry consensus standards require? In particular with Molded Case Circuit Breakers (MCCB's), how does one meet these requirements and still apply a balanced approach in a maintenance program when the facilities range from brand new construction to over fifty years old, and where circuit breakers exist that have been made by virtually every major manufacturer? This paper examines the instructions given by the various manufacturers, and examines the standards that exist, along with major guides and white paper recommendations. Both the consistencies and the inconsistencies are examined, recommendations are compared, and a general consensus of recommendations emerges. The various maintenance particulars are examined, from cycling of breakers and thermography to inverse thermal and instantaneous primary injection trip testing. The results of an FMEA (Failure Modes and Effects Analysis) was conducted at our facility; the results of that FMEA and the recommendations of that FMEA for maintenance of MCCB’s are presented. In this paper, we have examined the recommendations of manufacturers, standards, and guides that provide the guidelines for maintenance of molded case circuit breakers. Although many conflicts exist, a consensus of nearly universal recommendations emerges. A balanced approach to maintenance that provides the maximum safety benefit within the bounds of economic feasibility can be developed. We provide a condensation of the existing literature with references, a visual summary of that literature and propose a recommended maintenance approach.

42 ENGINEERING↗
DOE OSTI2024

Boron‐polymer composites engineered for compression molding, foaming, and additive manufacturing

Abstract Boron (specifically 10 B) is the element of choice to shield thermal neutrons due to its large (n, α) cross‐section; however, very few polymer composites containing high boron concentrations are available. This study aimed to determine the maximum possible amount of boron that could be introduced into a polymer matrix. Diverse manufacturing techniques, ranging from additive manufacturing to compression molding, were employed to fabricate inks and filaments for 3D printing, foams, and flexible pads. Composites using siloxanes, poly(lactic acid), and acrylonitrile butadiene styrene containing up to 80 wt% boron were sucessufully fabricated. The addition of known plasticizers (polyethylene glycol) and reinforcing agents (carbon nanofibers and fumed silica) helped to overcome fabrication problems such as clogging of the printing nozzle or crumbling of compression molded parts. In addition, the thermal‐mechanical properties of these novel boron composites were determined and shown to vary according to boron concentration, presence of additives, and fabrication techniques utilized.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Hot-tearing of multicomponent Al-Cu alloys based on casting load measurements in a constrained permanent mold

Hot-tearing is a major casting defect that is often difficult to characterize, especially for multicomponent Al alloys used for cylinder head castings. The susceptibility of multicomponent Al-Cu alloys to hot-tearing during permanent mold casting was investigated using a constrained permanent mold in which the load and displacement was measured. The experimental results for hot tearing susceptibility are compared with those obtained from a hot-tearing criterion based temperature range evaluated at fraction solids of 0.87 and 0.94. The Cu composition was varied from approximately 5 to 8 pct. (weight). Casting experiments were conducted without grain refining. The measured load during casting can be used to indicate the severity of hot tearing. However, when small hot-tears are present, the load variation cannot be used to detect and assess hot-tearing susceptibility.

Sabau, Adrian S↗
DOE OSTI2019

Interfacial Reaction Between High-Al Steel and CaO-Al{sub 2}O{sub 3}-Based Mold Fluxes with Different CaO/Al{sub 2}O{sub 3} Ratios at 1773 K (1500 °C)

The reaction between high-Al steel and CaO-Al{sub 2}O{sub 3}-based mold fluxes with different CaO/Al{sub 2}O{sub 3} ratios was investigated at 1773 K (1500 °C). The increase of CaO/Al{sub 2}O{sub 3} ratio from 1 to 3 accelerated the accumulation of Al{sub 2}O{sub 3} in the flux and reduction of Na{sub 2}O, but had no significant effect on the reduction of SiO{sub 2} and B{sub 2}O{sub 3}. The microstructure of flux-steel interfaces showed that emulsification occurred in the reaction between steel and mold flux. The emulsification was affected by the precipitation of crystals in the flux after the change of flux composition due to the interfacial reaction.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Numerical and Physical Simulation of the Fluid Flow in a Beam Blank Mold Fed Through the Center of the Web

Fluid flow inside a beam blank mold fed through a three-port SEN (two lateral ports and one bottom port), positioned at the center of the mold, has been investigated. Literature survey shows that this kind of configuration is not frequently used. It had been shown that it is possible to get a symmetrical flow with this configuration. The downward inclination of the ports should influence the transient fluid flow. The greater the downward inclination, the greater is the instability of the jet and of the interface between the immiscible fluids that simulate the slag/metal behavior. The flow characterization was made by dye dispersion, PIV technique, measurement of the meniscus oscillation using ultrasonic sensors, and CFD simulations. The slag/metal behavior was simulated using water and oils with different physical properties. The results from PIV as well as from observations of the water–oil interface have been used to validate the CFD simulations. Oils with density close to water resulted in more instability at the interface with entrainment starting from fluid flow rate of 125 L/min (equivalent to casting speed of 1 m/min). Decreasing the viscosity of slag (oils) and increasing the casting velocity (water flow rate) result in reduction of the interfacial stability.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Oxidation and Ignition Behaviors of Molten Mg-Nd-Zr Alloy in Resin-Sand Mold

High-temperature oxidation behavior of molten Mg-Nd-Zr in the pyrolysis atmosphere of resin-bind sand mold was investigated. The results showed that pouring temperature higher than 1023 K would sharply increase the ignition risk of melt in mold. The oxide formed on Mg-Nd-Zr melt below 973 K consists of two layers: mainly MgO for outer layer; mixture of MgO and Nd{sub 2}O{sub 3} for inner layer. The inner oxide mixture layer played an essential role in the protection of Mg-Nd-Zr matrix. Based on the experimental results and thermodynamic analysis, the oxidation process containing three stages was proposed. Nd- and Zn-enriched zone was found at the subsurface of oxide scale, without the enrichment of Zr. DICTRA calculation results indicated that this phenomenon was caused by the depletion of Mg and up-hill diffusion of Zr. Thus, Zr showed limited protection to the melt in long-term oxidation.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Additively Manufactured Single-Use Molds and Reusable Patterns for Large Automotive and Hydroelectric Components

Additive manufacturing (AM) has the potential to reduce costs in the casting industry, particularly for large parts (i.e., components with any dimension > 12 in.). In this study, pilot-scale production case studies of hydroelectric and automotive parts were used to evaluate two AM-enabled casting methods: the direct printing of sand molds by binder jet and printing of reusable cope and drag patterns for sand casting. An additional benefit was found when additively manufactured patterns were used in combination with heat-treat free aluminum alloys, to produce castings of complex hydrodynamic surfaces. These parts previously required production via subtractive machining due to part distortion induced by the quench step of heat treatments. The machine types used for the three case studies are sand-binder jet, high-resolution polymer fused deposition modeling (FDM), and big area additive manufacturing (BAAM) FDM in combination with CNC machining. Each method demonstrated distinct advantages over traditional casting practices in particular use cases. Single-use molds show great reductions in start-up cost to produce one-off or legacy parts, and additively manufactured impression patterns show promise for innovating the tooling design process for complex geometry and large castings.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Substitution of virgin carbon fiber with low-cost recycled fiber in automotive grade injection molding polyamide 66 for equivalent composite mechanical performance with improved sustainability

Recycled carbon fiber has historically proven challenging to integrate into composite manufacturing due in no small part to the low-density, randomly oriented, discontinuous fiber format that results from typical recycling. Discontinuous fiber requires the use of alternative technologies than those traditionally applied to continuous fiber (e.g., hand lay-up, winding). Extrusion compounding is one such applicable technology, but material transfer into the system requires alternative feeding equipment or the use of an altered procedure as trialed in this research. In this study, an injection molding compound for automotive applications was prepared with recycled carbon fiber and compared against an existing commercial compound. Input fibers and molded compound were evaluated for mechanical performance, while relevant variables such as compounded fiber alignment and aspect ratio were compared to the existing baseline material to confirm a like-for-like composite material structure. Overall, analysis indicates that recycled fiber performs similarly to virgin fiber reinforcement, demonstrating that recycled fiber may be a viable drop-in replacement for short-fiber discontinuous applications.

42 ENGINEERING↗
DOE OSTI2018

Multiscale finite element modeling of sheet molding compound (SMC) composite structure based on stochastic mesostructure reconstruction

Predicting the mechanical behavior of the chopped carbon fiber Sheet Molding Compound (SMC) due to spatial variations in local material properties is critical for the structural performance analysis but is computationally challenging. Such spatial variations are induced by the material flow in the compression molding process. In this work, a new multiscale SMC modeling framework and the associated computational techniques are developed to provide accurate and efficient predictions of SMC mechanical performance. The proposed multiscale modeling framework contains three modules. First, a stochastic algorithm for 3D chip-packing reconstruction is developed to efficiently generate the SMC mesoscale Representative Volume Element (RVE) model for Finite Element Analysis (FEA). A new fiber orientation tensor recovery function is embedded in the reconstruction algorithm to match reconstructions with the target characteristics of fiber orientation distribution. Second, a metamodeling module is established to improve the computational efficiency by creating the surrogates of mesoscale analyses. Third, the macroscale behaviors are predicted by an efficient multiscale model, in which the spatially varying material properties are obtained based on the local fiber orientation tensors. Our approach is further validated through experiments at both meso- and macro-scales, such as tensile tests assisted by Digital Image Correlation (DIC) and mesostructure imaging.

36 MATERIALS SCIENCE↗
DOE OSTI2014

The mold integration method for the calculation of the crystal-fluid interfacial free energy from simulations

The interfacial free energy between a crystal and a fluid, γ{sub cf}, is a highly relevant parameter in phenomena such as wetting or crystal nucleation and growth. Due to the difficulty of measuring γ{sub cf} experimentally, computer simulations are often used to study the crystal-fluid interface. Here, we present a novel simulation methodology for the calculation of γ{sub cf}. The methodology consists in using a mold composed of potential energy wells to induce the formation of a crystal slab in the fluid at coexistence conditions. This induction is done along a reversible pathway along which the free energy difference between the initial and the final states is obtained by means of thermodynamic integration. The structure of the mold is given by that of the crystal lattice planes, which allows to easily obtain the free energy for different crystal orientations. The method is validated by calculating γ{sub cf} for previously studied systems, namely, the hard spheres and the Lennard-Jones systems. Our results for the latter show that the method is accurate enough to deal with the anisotropy of γ{sub cf} with respect to the crystal orientation. We also calculate γ{sub cf} for a recently proposed continuous version of the hard sphere potential and obtain the same γ{sub cf} as for the pure hard sphere system. The method can be implemented both in Monte Carlo and Molecular Dynamics. In fact, we show that it can be easily used in combination with the popular Molecular Dynamics package GROMACS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Structural behavior and dynamics of an anomalous fluid between attractive and repulsive walls: Templating, molding, and superdiffusion

Confinement can modify the dynamics, the thermodynamics, and the structural properties of liquid water, the prototypical anomalous liquid. By considering a generic model for anomalous liquids, suitable for describing solutions of globular proteins, colloids, or liquid metals, we study by molecular dynamics simulations the effect that an attractive wall with structure and a repulsive wall without structure have on the phases, the crystal nucleation, and the dynamics of the fluid. We find that at low temperatures the large density of the attractive wall induces a high-density, high-energy structure in the first layer (“templating” effect). In turn, the first layer induces a “molding” effect on the second layer determining a structure with reduced energy and density, closer to the average density of the system. This low-density, low-energy structure propagates further through the layers by templating effect and can involve all the existing layers at the lowest temperatures investigated. Therefore, although the high-density, high-energy structure does not self-reproduce further than the first layer, the structured wall can have a long-range influence thanks to a sequence of templating, molding, and templating effects through the layers. We find that the walls also have an influence on the dynamics of the liquid, with a stronger effect near the attractive wall. In particular, we observe that the dynamics is largely heterogeneous (i) among the layers, as a consequence of the sequence of structures caused by the walls presence, and (ii) within the same layer, due to superdiffusive liquid veins within a frozen matrix of particles near the walls at low temperature and high density. Hence, the partial freezing of the first layer does not correspond necessarily to an effective reduction of the channel's section in terms of transport properties, as suggested by other authors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Injection molding of high precision optics for LED applications made of liquid silicone rubber

Light Emitting Diodes (LED) conquer the growing global market of lighting technologies. Due to their advantages, they are increasingly used in consumer products, in lighting applications in the home and in the mobility sector as well as in industrial applications. Particularly, with regard to the increasing use of high-power LED (HP-LED) the materials in the surrounding area of the light emitting semiconductor chip are of utmost importance. While the materials behind the semiconductor chip are optimized for maximum heat dissipation, the materials currently used for the encapsulation of the semiconductor chip (primary optics) and the secondary optics encounter their limits due to the high temperatures. In addition certain amounts of blue UV radiation degrade the currently used materials such as epoxy resins or polyurethanes for primary optics. In the context of an ongoing joint research project with various partners from the industry, an innovative manufacturing method for high precision optics for LED applications made of liquid silicone rubber (LSR) is analyzed at the Institut of Plastics Processing (IKV), Aachen. The aim of this project is to utilize the material-specific advantages of high transparent LSR, especially the excellent high temperature resistance and the great freedom in design. Therefore, a high integrated injection molding process is developed. For the production of combined LED primary and secondary optics a LED board is placed in an injection mold and overmolded with LSR. Due to the integrated process and the reduction of subcomponents like the secondary optics the economics of the production process can be improved significantly. Furthermore combined LED optics offer an improved effectiveness, because there are no losses of the light power at the transition of the primary and secondary optics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Numerical simulation of fiber interaction in short-fiber injection-molded composite using different cavity geometries

The theoretical fiber-interaction model for calculating the fiber orientation in the injection molded short fiber/thermoplastic composite parts was proposed. The proposed model included the fiber dynamics simulation in order to obtain an equation of the global interaction coefficient and accurate estimate of the fiber interacts at all orientation states. The steps to derive the equation for this coefficient in short fiber suspension as a function of the fiber aspect ratio, volume fraction and general shear rate are delineated. Simultaneously, the high-resolution 3D X-ray computed tomography system XVA-160α was used to observe fiber distribution of short-glass-fiber-reinforced polyamide specimens using different cavity geometries. The fiber orientation tensor components are then calculated. Experimental orientation measurements of short-glass-fiber-reinforced polyamide is used to check the ability of present theory for predicting orientation. The experiments and predictions show a quantitative agreement and confirm the basic understanding of fiber orientation in injection-molded composites.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Remarkable thermoelectric performance in BaPdS 2 via pudding-mold band structure, band convergence, and ultralow lattice thermal conductivity

Efficient thermoelectric materials require a rare and contraindicated combination of materials properties: large electrical conductivity, large Seebeck coefficient, and low thermal conductivity. One strategy to achieve the first two properties is via low-energy electronic bands containing both flat and dispersive parts in different regions of crystal momentum space, known as a pudding-mold band structure. Here, we illustrate that BaPdS 2 successfully achieves the pudding-mold band structure for the valence band, contributing to a large p-type thermoelectric power factor, due to its anisotropic crystal structure containing zigzag chains of edge-sharing square planar PdS 4 units; large power factor is achieved for n-type doping as well due to band convergence. In addition, BaPdS 2 exhibits ultralow lattice thermal conductivity, and thus also achieves the third property, due to extremely soft and anharmonic interactions in its transverse acoustic phonon branch. We predict a remarkably large thermoelectric figure of merit, with peak values between 2 and 3 for two of the three crystallographic directions, suggesting BaPdS 2 warrants experimental investigation.

36 MATERIALS SCIENCE↗
DOE OSTI2015

SU-E-T-232: Custom High-Dose-Rate Brachytherapy Surface Mold Applicators: The Importance Source to Skin Distance

Purpose: Surface mold applicators can be customized to fit irregular skin surfaces that are difficult to treat with other radiation therapy techniques. Optimal design of customized HDR skin brachytherapy is not well-established. We evaluated the impact of applicator thickness (source to skin distance) on target dosimetry. Methods: 27 patients had 34 treated sites: scalp 4, face 13, extremity 13, and torso 4. Custom applicators were constructed from 5–15 mm thick thermoplastic bolus molded over the skin lesion. A planar array of plastic brachytherapy catheters spaced 5–10 mm apart was affixed to the bolus. CT simulation was used to contour the target volume and to determine the prescription depth. Inverse planning simulated annealing followed by graphical optimization was used to plan and deliver 40–56 Gy in 8–16 fractions. Target coverage parameters (D90, Dmean, and V100) and dose uniformity (V110–200, D0.1cc, D1cc, and D2cc) were studied according to target depth (<5mm vs. ≥5mm) and applicator thickness (5–10mm vs. ≥10mm). Results: The average prescription depth was 4.2±1.5mm. The average bolus thickness was 9.2±2.4mm. The median CTV volume was 10.0 cc (0.2–212.4 cc). Similar target coverage was achieved with prescription depths of <5mm and ≥5mm (Dmean = 113.8% vs. 112.4% and D90 = 100.2% vs. 98.3%). The <5mm prescription depth plans were more uniform (D0.1cc = 131.8% vs. 151.8%). Bolus thickness <10mm vs. ≥10mm plans also had similar target coverage (Dmean = 118.2% vs. 110.7% and D90 = 100.1% vs. 99.0%). Applicators ≥10mm thick, however, provide more uniform target dosimetry (D0.1cc = 146.9% vs. 139.5%). Conclusion: Prescription depth is based upon the thickness of the lesion and upon the clinical needs of the patient. Applicators ≥10mm thick provide more dose uniformity than 5–10mm thick applicators. Applicator thickness is an important variable that should be considered during treatment planning to achieve optimal dose uniformity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

3D Flow and Temperature Analysis of Filling a Plutonium Mold (Revision 1) [Poster]

The plutonium foundry at Los Alamos National Laboratory casts products for various special nuclear applications. However, plutonium’s radioactivity, material properties, and security constraints complicate the ability to perform experimental analysis of mold behavior. The Manufacturing Engineering and Technologies (MET-2) group previously developed a graphite mold to vacuum cast small plutonium disks to be used by the Department of Homeland Security as point sources for radiation sensor testing. A two-stage pouring basin consisting of a funnel and an angled cavity directs the liquid into a vertical runner. A stack of ten disk castings connect to the runner by horizontal gates. Volumetric flow rates were implemented to limit overflow into the funnel and minimize foundry returns. Models using Flow-3D computational fluid dynamics software are employed here to determine liquid Pu flow paths, optimal pour regimes, temperature changes, and pressure variations.

36 MATERIALS SCIENCE↗