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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

System and method for roll-to-roll film tensioning for reduced separation force during bottom-up stereolithography

The present disclosure relates to a tensioning system for use in a stereolithography manufacturing application. The system may have a build plate for supporting a three dimensional part being formed using a photo responsive resin, a base plate and a release element extending over the base plate. The release element is configured to receive a quantity of photo responsive resin for forming a new material layer of the three dimensional part. A pair of tensioning components are secured to opposite ends of the release element, and apply a controlled tension force to the release element during peeling of the release element to reduce a separation force required to separate the release element from the new material layer after the new material layer is cured.

Duoss, Eric B.↗
DOE OSTI2016

The Effect of Rolling As-Cast and Homogenized U-10Mo Samples on the Microstructure Development and Recovery Curves

Over the past several years Pacific Northwest National Laboratory (PNNL) has been actively involved in supporting the U.S. Department of Energy National Nuclear Security Administration Office of Material Management and Minimization (formerly Global Threat Reduction Initiative). The U.S. High- Power Research Reactor (USHPRR) project is developing alternatives to existing highly enriched uranium alloy fuel to reduce the proliferation threat. One option for a high-density metal fuel is uranium alloyed with 10 wt% molybdenum (U-10Mo). Forming the U-10Mo fuel plates/foils via rolling is an effective technique and is actively being pursued as part of the baseline manufacturing process. The processing of these fuel plates requires systematic investigation/understanding of the pre- and post-rolling microstructure, end-state mechanical properties, residual stresses, and defects, their effect on the mill during processing, and eventually, their in-reactor performance. In the work documented herein, studies were conducted to determine the effect of cold and hot rolling the as-cast and homogenized U-10Mo on its microstructure and hardness. The samples were homogenized at 900°C for 48 h, then later annealed for several durations and temperatures to investigate the effect on the material’s microstructure and hardness. The rolling of the as-cast plate, both hot and cold, was observed to form a molybdenum-rich and -lean banded structure. The cold rolling was ineffective, and in some cases exacerbated the as-cast defects. The grains elongated along the rolling direction and formed a pancake shape, while the carbides fractured perpendicularly to the rolling direction and left porosity between fractured particles of UC. The subsequent annealing of these samples at sub-eutectoid temperatures led to rapid precipitation of the ' lamellar phase, mainly in the molybdenum-lean regions. Annealing the samples above the eutectoid temperature did not refine the grain size or the banded microstructure. However, annealing the samples led to quick recovery in hardness as evidenced by a drop in Vickers hardness of 20%. Hot rolling was performed at 650 and 800°C. The hot-rolling mill loads (load separation force) were approximately 40 to 50% less than the cold-rolling for the same reduction and thickness. It was observed that hot rolling the samples with 50% or more reduction in thickness were responsible for dynamic recrystallization in the hot-rolled samples and led to grain refinement. Unlike the cold-rolled samples, the hot-rolled samples did not fracture the carbides and appeared to heal the casting defects. The recovery phenomenon was similar to the cold-rolled samples above the eutectoid temperatures, but owing to the refined grain size, the precipitation of the lamellar phase was far more rapid in these samples and the hardness increased more rapidly than in the cold rolled sample when heated below the eutectoid temperature. The data generated from these rolling efforts has been used to make the process modeling efforts more robust and applicable to all USHPRR partner rolling mills. The flow stress for cold rolling the samples was determined to be between 170-190 ksi, with frictional forces between 0.2 and 0.4 for the PNNL mill. The measured roll separation forces and those simulated using finite element methods for hot and cold rolling for the PNNL rolling mill were in good agreement.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

The Effect of Rolling As-Cast and Homogenized U-10Mo Samples on the Microstructure Development and Recovery Curves

Over the past several years Pacific Northwest National Laboratory (PNNL) has been actively involved in supporting the U.S. Department of Energy National Nuclear Security Administration Office of Material Management and Minimization (formerly Global Threat Reduction Initiative). The U.S. High-Power Research Reactor (USHPRR) project is developing alternatives to existing highly enriched uranium alloy fuel to reduce the proliferation threat. One option for a high-density metal fuel is uranium alloyed with 10 wt% molybdenum (U-10Mo). Forming the U-10Mo fuel plates/foils via rolling is an effective technique and is actively being pursued as part of the baseline manufacturing process. The processing of these fuel plates requires systematic investigation/understanding of the pre- and post-rolling microstructure, end-state mechanical properties, residual stresses, and defects, their effect on the mill during processing, and eventually, their in-reactor performance. In the work documented herein, studies were conducted to determine the effect of cold and hot rolling the as-cast and homogenized U-10Mo on its microstructure and hardness. The samples were homogenized at 900°C for 48 h, then later annealed for several durations and temperatures to investigate the effect on the material’s microstructure and hardness. The rolling of the as-cast plate, both hot and cold, was observed to form a molybdenum-rich and -lean banded structure. The cold rolling was ineffective, and in some cases exacerbated the as-cast defects. The grains elongated along the rolling direction and formed a pancake shape, while the carbides fractured perpendicularly to the rolling direction and left porosity between fractured particles of UC. The subsequent annealing of these samples at sub-eutectoid temperatures led to rapid precipitation of the α + γ ' lamellar phase, mainly in the molybdenum-lean regions. Annealing the samples above the eutectoid temperature did not refine the grain size or the banded microstructure. However, annealing the samples led to quick recovery in hardness as evidenced by a drop in Vickers hardness of 20%. Hot rolling was performed at 650 and 800°C. The hot-rolling mill loads (load separation force) were approximately 40 to 50% less than the cold-rolling for the same reduction and thickness. It was observed that hot rolling the samples with 50% or more reduction in thickness were responsible for dynamic recrystallization in the hot-rolled samples and led to grain refinement. Unlike the cold-rolled samples, the hot-rolled samples did not fracture the carbides and appeared to heal the casting defects. The recovery phenomenon was similar to the cold-rolled samples above the eutectoid temperatures, but owing to the refined grain size, the precipitation of the lamellar phase was far more rapid in these samples and the hardness increased more rapidly than in the cold rolled sample when heated below the eutectoid temperature. The data generated from these rolling efforts has been used to make the process modeling efforts more robust and applicable to all USHPRR partner rolling mills. The flow stress for cold rolling the samples was determined to be between 170-190 ksi, with frictional forces between 0.2 and 0.4 for the PNNL mill. The measured roll separation forces and those simulated using finite element methods for hot and cold rolling for the PNNL rolling mill were in good agreement.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Computational Modeling of Multi-Pass Rolling Parameters Effect on Resulting Fuel Foil Shape

A focus of the U.S. Department of Energy is to improve production yield and reduce the cost of Low Enriched Uranium (LEU)-molybdenum alloy (U-10Mo) monolithic fuel plates that will be replacing High Enriched Uranium (HEU) oxide dispersion fuels used currently in the United States High Performance Research Reactors (USHPRR). One area of improvement is lowering the high transverse waviness and longitudinal waviness currently present within rolled foils prior to cladding to produce fuel plates. Traditional rolling manufacturing techniques for other metal foils use winders to pull and straighten the foil as it is rolled back and forth to the final thickness. This approach cannot be used to roll thin U-10Mo foils (0.008-0.025” thick) because only small castings can be rolled due to nuclear criticality safety concerns. As a result, the fuel foils are too short (1 m in length) to use traditional winders. Therefore, it is crucial to identify other rolling parameters (i.e., roller friction, axial tension load, roller diameter, and roll pass reduction percent) that might reduce transverse waviness and longitudinal waviness in the rolled fuel foil and develop a high-yield, low-cost multi-pass rolling manufacturing process. This report documents a systematic finite element modeling study to investigate the effects of numerous rolling parameters to reduce resulting transverse waviness and longitudinal waviness in the fuel foil during multi-pass rolling of U-10Mo foils. The rolling of a U-10Mo plate with initial dimensions of 1”x1”x 0.048” is modeled using Abaqus CAE. This rolling is modeled to undergo eight 20% reduction roll passes to a final fuel foil thickness of 0.01”. The elastic-plastic constitutive model of the U-10Mo alloy was input to the fuel foil rolling model. The rollers were modeled as rigid bodies. A comparison of rolling friction coefficients of 0.3 and 0.7 over a wide range of applied axial tension loads were investigated in order to evaluate the effect of using a lubricant during rolling. The effect of roller diameter on the resulting transverse waviness and longitudinal waviness of the fuel foil over a wide range of axial tension loads were also investigated by modeling rollers 7/8” and 3.75” in diameter. The results of this systematic finite element method study will aid manufacturers in producing low transverse waviness and reduced longitudinal waviness in U-10Mo fuel foils.

U-10Mo, FEA, Rolling, Residual Stress, Fuel Foil↗
DOE OSTI2019

Microstructure, Texture, and Mechanical Properties of Continuously Extruded and Rolled AZ31 Magnesium Alloy Sheets

It is difficult to fabricate magnesium alloy sheets at room temperature due to their hexagonal close-packed structure. In this paper, we proposed a new process that can be used to fabricate AZ31 magnesium alloy sheets with fine-grained microstructure and good mechanical properties. AZ31 magnesium alloy sheets with dimensions of 160 mm × 8 mm were obtained successfully by a continuous extrusion technique. The extruded sheets were then rolled by two different rolling routes, Route 1: the extruded sheet was heated at 350 °C and then rolled without heating of rolls and Route 2: the sheet was rolled without any previous heating by heating rolls at 280 °C. The microstructure and texture evolution as well as mechanical properties of the continuously extruded and rolled sheets were examined experimentally. The magnesium alloy sheets with relatively fine grains of 4.5-8.3 µm were obtained by continuous extrusion followed by rolling processes. The tensile strength of continuously extruded AZ31 Mg alloy sheets can be effectively increased by rolling using heating rolls (Route 2), while the ductility was enhanced by rolling heated sheets (Route 1). The mixed microstructure, consisting of refined DRX grains and deformed grains, contributes to enhancement in tensile strength of the sheet samples rolled by Route 2 due to grain-boundary strengthening and work hardening. Lower temperature and larger rolling reduction are two main factors for improving the tensile strength of AZ31magnesium alloy sheets.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Hot rolling of ZK60 magnesium sheet with isotropic tensile properties from tubing made by Shear Assisted Processing and Extrusion (ShAPE)

In order to evaluate the viability of ShAPE processed Mg alloys as a feedstock for fabricating lightweight sheet material, tubes consisting of ShAPE-extruded Mg alloy ZK60 were flattened into plates and hot rolled at 450 °C to reductions of 37%, 68%, and 93%. The mechanical properties and microstructure of the rolled material were characterized through tensile testing and electron backscattered diffraction (EBSD). ZK60 specimens rolled to 68% reduction had tensile properties similar to published properties of rolled ZK60 sheets fabricated using conventional processes, and exhibited negligible tensile anisotropy referenced to the rolling direction. Additional rolling from 68% to 93% reduced the ultimate tensile stress in the rolling direction from 341.74±5.96 MPa to 260.76±22.4MPa. The yield stress and elongation to failure of the material also decreased from 292.16±1.11 MPa to 256.93±18.4 MPa and 6.95±1.94% to 3.38±0.51%, respectively, but negligible little anisotropy was observed with respect to loading direction. EBSD mapping indicated that the as-extruded ZK60 had texture rotated away from the basal direction which developed into a strong basal texture over numerous hot rolling steps. This evolution in texture has been observed after rolling for hot-rolled ZK60 fabricated through conventional extrusion processes. The initial grain structure was found to have experienced noticeable twinning from flattening the tube into plate. After hot rolling, the grain structure became more equiaxed, but the average grain diameter did not change appreciably from 5.15 ± 3.39 µm in the ShAPE extruded material, to 5.27 ± 12.44 µm in the 93% hot rolled sheet. This response to hot rolling is similar to the response of ZK60 fabricated using other methods such as Equal Channel Angular Processing (ECAP). Therefore, this work demonstrates ShAPE has the potential as an alternative method to producing feedstock for Mg alloy sheets. Modifications to the experimental procedure which could lead to improvements in observed properties are briefly discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Mechanical Properties and Strain-Induced Martensite Transformation in Cold Rolling of 304L Stainless Steel Plate

In this work, cold rolling behavior of stainless steel 304L is investigated and the effects of different process parameters on the occurrence of strain-induced martensite and mechanical properties are studied. The rolling experiments are conducted under different rolling speeds and reductions in which a set of samples is deformed at room temperature and the other set is first cooled to the temperature of − 10 °C and then rolled. Afterward, the developed microstructures and mechanical properties of the rolled steel are evaluated employing different testing techniques. In order to justify the results, mathematical modeling of cold rolling operation is also performed using Abaqus/Explicit to estimate the distribution of equivalent plastic strain and temperature rise during rolling. The results show that strain-induced martensite may occur during cold rolling and it efficiently alters microstructure and mechanical performance of the rolled plate. The amount of reduction, initial temperature, rolling layout, and, to a lesser extent, rolling speed can affect the kinetics of martensite transformation as well as microstructure and mechanical properties of the rolled steel.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of Sn microalloying on cold rolling and recrystallization textures and microstructure of a ferritic stainless steel

Highlights: • Sn microalloying contributes to the enhancement in cold rolling texture intensity and the acceleration in cold rolling texture transformation. • Sn microalloying promotes the recrystallization process, and recrystallization occurs preferentially in steel with Sn compared with Sn-free steel. • Sn microalloying inhibits the growth of recrystallized grains, and the finer grains are obtained in steel with Sn. - Abstract: We investigated the effects of Sn microalloying on cold rolling and recrystallization textures and microstructure of a ferritic stainless steel. The as-received hot rolled sheets were cold rolled at 10%–90% reductions; the sheets cold rolled up to an 80% reduction were annealed at 740–880 °C for 5 min. For comparison, the cold rolling and recrystallization textures of the steel sheets with and without Sn were determined with the conventional X-ray diffraction method. The cold rolling and recrystallization metallographic microstructures were measured by scanning electron microscope and optical microscope, and the crystal orientation maps of the cold rolled and annealed samples were observed by electron backscattered diffraction. The micro-hardness was determined using a digital micro-hardness tester. Our results show that Sn microalloying in a medium chromium ferritic stainless steel plays multiple roles in the cold rolling and recrystallization processes. Sn micrcoalloying contributes to the enhancement in cold rolling texture intensity and the acceleration in cold rolling texture transformation. Sn microalloying is beneficial in promoting the recrystallization process. Recrystallization occurs preferentially in the ferritic stainless steel with Sn. Sn microalloying plays an important role in inhibiting the growth of recrystallized grains. The finer grains are obtained in ferritic stainless steel with Sn when annealing at high temperatures.

36 MATERIALS SCIENCE↗
NASA NTRS1976

An experimental study for determining human discomfort response to roll vibration

An experimental study using a passenger ride quality apparatus (PRQA) was conducted to determine the subjective reactions of passengers to roll vibrations. The data obtained illustrate the effect upon human comfort of several roll-vibration parameters: namely, roll acceleration level, roll frequency, and seat location (i.e., distance from axis of rotation). Results of an analysis of variance indicated that seat location had no effect on discomfort ratings of roll vibrations. The effect of roll acceleration level was significant, and discomfort ratings increased markedly with increasing roll acceleration level at all roll frequencies investigated. Of particular interest, is the fact that the relationship between discomfort ratings and roll acceleration level was linear in nature. The effect of roll frequency also was significant as was the interaction between roll acceleration level and roll frequency.

Leatherwood, J. D.↗
DOE OSTI2019

Analysis of Hot- and Cold-Rolled Loads in Medium-Mn TRIP Steels

The purpose of this work is to investigate the hot- and cold-rolling requirements to produce third-generation advanced high-strength steels (AHSS). Therefore, five medium-Mn (10 to 14 wt pct Mn) alloys that exhibit transformation-induced plasticity (TRIP) were compared to a commercially produced grade of AISI 1018 using hot- and cold-rolling experiments. Experimental data collected from a STANAT instrumented rolling mill was utilized to measure force and torque during hot- and cold-rolling. Experimental data were processed by a 1D analytical model, based on Orowan model, to determine rolling pressure. It was determined that pressures required to hot-roll TRIP alloys are 1.4 to 1.8 times greater than pressures for rolling AISI 1018 steel. Cold rolling of the medium-Mn TRIP steels was found to be 1.5 to 2.8 times greater than the AISI 1018 steel. Mechanical and microstructural characterization was also performed and the variation in rolling pressure was related to the starting microstructural constituents, and alloys containing greater starting quantities of ε-martensite in the microstructure had higher flow stresses at equivalent rolling strains during cold rolling.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of rolling processes on ridging generation of ferritic stainless steel

Highlights: • The effects of microstructural refinement and texture on ridging are analysed. • Optimal reduction during cold rolling benefits the enhancement of ridging resistance. • A Steckel-mill rolling method is proposed to improve ridging resistance of FSS 430. • 30% of ridging height reduction can be achieved with proposed rolling method. - Abstract: In order to reduce the ridging generation of ferritic stainless steel (FSS) during forming process, the crystallographic texture of the FSS was modified by optimisation of both rolling and annealing processes. A systematic study was carried out to improve the ridging resistance of the FSS by investigating the sequential changes in microstructure and texture during different rolling and annealing processes. The results show that the surface roughness of the final sheet strained by 20% along the rolling direction is decreased by 20% to 30% using Steckel-mill rolling compared to traditional tandem rolling. A direct correlation is found between the ridging resistance of the FSS and the rolling routines. It has been observed that an optimal reduction value during cold rolling process is critical to the microstructural refinement and surface quality improvement of the FSS. Reduction of the fraction of {001} <110> component by optimisation of the rolling processes is found to be effective in reducing the ridging height of the FSS during the formation process.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of strain on the formation of cold-rolling and grain growth textures of an equiatomic HfZrTiTaNb refractory high entropy alloy

Highlights: • Effect of strain on Texture formation is reported in HfZrTiTaNb for the first time. • Cold-rolled microstructure shows high density of deformation heterogeneities. • Weak texture compared to other BCC phases in HEAs • Imposed strain does not affect texture significantly unlike other BCC materials. - Abstract: The effect of cold-rolling strain on the evolution of deformation and grain growth textures in an equiatomic HfZrTiTaNb refractory high entropy alloy (RHEA) was investigated. For this purpose, the development of microstructure and texture was compared in 50% and 90% cold-rolled materials. The development of deformation microstructure was accompanied by the formation of extensive deformation heterogeneities. The 90% cold-rolled material showed ultrafine lamellar regions as well as regions severely fragmented by the fine scale deformation heterogeneities. The 50% cold-rolled material showed dominant ND-fiber (ND//), while the 90% cold-rolled material showed presence of both RD (RD//) and ND-fiber components. Profuse deformation heterogeneities presumably weakened the deformation texture considerably. The annealing texture of the 50% and 90% cold-rolled material showed stronger {111} component. Comparison of the annealing texture of the 50% and 90% cold-rolled materials with other BCC HEA phases indicated much weaker texture. The annealing texture of the RHEA was not significantly strengthened by increasing cold-rolling strain, presumably due to the high density of deformation heterogeneities in the cold-rolled microstructure. Thus, deformation heterogeneities significantly influenced the formation of cold-rolling and annealing textures of the equiatomic HfZrTiTaNb RHEA.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Computer-aided analysis and design of the shape rolling process for producing turbine engine airfoils

Mild steel (AISI 1018) was selected as model cold-rolling material and Ti-6Al-4V and INCONEL 718 were selected as typical hot-rolling and cold-rolling alloys, respectively. The flow stress and workability of these alloys were characterized and friction factor at the roll/workpiece interface was determined at their respective working conditions by conducting ring tests. Computer-aided mathematical models for predicting metal flow and stresses, and for simulating the shape-rolling process were developed. These models utilize the upper-bound and the slab methods of analysis, and are capable of predicting the lateral spread, roll-separating force, roll torque and local stresses, strains and strain rates. This computer-aided design (CAD) system is also capable of simulating the actual rolling process and thereby designing roll-pass schedule in rolling of an airfoil or similar shape. The predictions from the CAD system were verified with respect to cold rolling of mild steel plates. The system is being applied to cold and hot isothermal rolling of an airfoil shape, and will be verified with respect to laboratory experiments under controlled conditions.

Lahoti, G. D.↗
NASA NTRS1985

Wind-tunnel investigation at supersonic speeds of a remote-controlled canard missile with a free-rolling-tail brake torque system

Wind tunnel tests were conducted at Mach numbers 1.70, 2.16, and 2.86 to determine the static aerodynamic characteristics of a cruciform canard-controlled missile with fixed or free rolling tailfin afterbodies. Mechanical coupling effects of the free-rolling-tail afterbody were investigated by using an electronic electromagnetic brake system providing arbitrary tail-fin brake torques with continuous measurements of tail-to-mainframe torque and tail roll rate. Remote-controlled canards were deflected to provide pitch, yaw, and roll control. Results indicate that the induced rolling moment coefficients due to canard yaw control are reduced and linearized for the free-rolling-tail (free-tail) configuration. The canards of the latter provide conventional roll control for the entire angle-of-attack test range. For the free-tail configuration, the induced rolling moment coefficient due to canard yaw control increased and the canard roll control decreased with increases in brake torque, which simulated bearing friction torque. It appears that a compromise in regard to bearing friction, for example, low-cost bearings with some friction, may allow satisfactory free-tail aerodynamic characteristics that include reductions in adverse rolling-moment coefficients and lower tail roll rates.

Blair, A. B., Jr.↗
NASA NTRS2008

GRCop-84 Rolling Parameter Study

This report is a section of the final report on the GRCop-84 task of the Constellation Program and incorporates the results obtained between October 2000 and September 2005, when the program ended. NASA Glenn Research Center (GRC) has developed a new copper alloy, GRCop-84 (Cu-8 at.% Cr-4 at.% Nb), for rocket engine main combustion chamber components that will improve rocket engine life and performance. This work examines the sensitivity of GRCop-84 mechanical properties to rolling parameters as a means to better define rolling parameters for commercial warm rolling. Experiment variables studied were total reduction, rolling temperature, rolling speed, and post rolling annealing heat treatment. The responses were tensile properties measured at 23 and 500 C, hardness, and creep at three stress-temperature combinations. Understanding these relationships will better define boundaries for a robust commercial warm rolling process. The four processing parameters were varied within limits consistent with typical commercial production processes. Testing revealed that the rolling-related variables selected have a minimal influence on tensile, hardness, and creep properties over the range of values tested. Annealing had the expected result of lowering room temperature hardness and strength while increasing room temperature elongations with 600 C (1112 F) having the most effect. These results indicate that the process conditions to warm roll plate and sheet for these variables can range over wide levels without negatively impacting mechanical properties. Incorporating broader process ranges in future rolling campaigns should lower commercial rolling costs through increased productivity.

Loewenthal, William S.↗
DOE OSTI2018

Roll Compaction of Powdered Radioactive Wastes - 18251

Most of low- and intermediate-level radioactive wastes must be solidified by a proper binding matrix and disposed at the centralized disposal site. So it is desirable to achieve a high loading of radwastes in a drum to reduce the disposal fee while meeting both the national regulations and the waste acceptance criteria of the disposal site. In general, the radioactive wastes (liquid, dried powder and sludge) were solidified by mixing with a proper binding matrix (cement, polymer, asphalt, etc.), but their solidified volume inevitably increases due to the limitation of incorporating of radwaste into a binding matrix. To solve this problem, some Korean NPPs operate both a CTS (Concentrate Treatment System, evaporation and granulation) and a polymer solidification system. The size distribution of granulated wastes produced by CTS is so broad (diameter; several μm ∼ several cm) that a polymer cannot impregnate the void space between particles due to their small size. However, if the powdered radwaste can be compacted into high density pellets, and the pellets can be loaded in a drum with maximum waste loading, then the binding matrix can fill the void between pellets, it might be more desirable to keep the size distribution of pellets constant to reduce the solidified waste volume. This compaction methodology can greatly reduce the disposal fee due to the reduction of the solidified waste volume, and can facilitate polymer solidification due to the constant size of the radwaste pellets. This methodology is also applicable to solidify powdered wastes such a depleted uranium used as a catalyst, ash and sludge. Loading radwaste compacted with bentonite pellets versus particles into a container serves, as an engineered or natural barrier in a deep geologic disposal system. Roll compaction is a typical agglomeration process for dry powders and depends on the device parameters and the material properties. This study, firstly, was focused on the design of roll compactor (briquetting machine), the shape and size of pellet, and secondly the loading method of pellets into a drum, their solidification in polymer, and evaluating the overall volume reduction. We used bentonite (particle size; 85 ∼ 100 μm) as a material to be compacted instead of radwaste powders (concentrates and depleted uranium wastes) without the addition of agglomeration agents. In the design of roll, we considered the diameter (200 mm) and width (41 mm) of roll, two types of pocket shapes (< 9 mm, 0.275 ml), and the surface of the pocket. Fig. 2 shows two pellet shapes, tetragonal and circular. The pressure of roll compactor, one of the main process variables, is > 320 kg f/cm{sup 2}, and the roll gap is 0.5 mm. The powders are compacted in a compaction zone between two counter-rotating rolls according to the complicated mechanisms. As a result of the state and the apparent density of the pellets obtained by changing the pressure from 0 to 286 kg f/cm{sup 2}, the pellets were unstable at pressure=0, but above 148 kg f/cm{sup 2} the pellets were more stable, and the apparent density of the pellets was 2.63 g/cm{sup 3} at 148 kg f/cm{sup 3}, and 2.68 g/cm{sup 3} at 286 kg f/cm{sup 2}. The roller speed (rpm) can determine the capacity (kg/h) of a compactor, and depends on both the compaction pressure and the feeding rate. By increasing the roll speed from 2 to 4 rpm, the apparent density of pellets was decreased gradually from 2.74 g/cm{sup 3} to 1.45 g/cm{sup 3}. We designed the special feeding system in order to feed powders uniformly to the roll gripping zone and to supply powders into the narrowest part of the roll gap. At a constant roll speed (3 rpm) and a constant compaction pressure (286 kg f/cm{sup 2}), the apparent density of the pellets was linearly proportional to the feeding rate from 2.18 to 2.74 g/cm{sup 3} by changing the feeding rate of powders from 8 to 12 rpm. In the polymer solidification of the obtained pellets, we used epoxy resin as a solidification agent, and showed their solidified waste forms in Fig. 5. The incorporation ratio (wt.%) of powders/polymer was about 71.7/28.3 in tetragonal pellets, 71.9/28.1 in circular pellets. We calculated the volume reduction in an aspect of powders itself and the solidified waste form. In powder case, through the comparison of the apparent density of the obtained pellets (2.74 g/cm{sup 3}) and raw powders (0.93 g/cm{sup 3}), the volume reduction was calculated as about 2.74/0.93 = 2.95 times. This means that powders can be compacted to 1/2.95 times. And in waste form case, the weight ratio of powder/polymer in a mixing method (workable) and a compaction method is about 0.42, 2.56, individually. Therefore the volume reduction was calculated as about 2.56/0.42 = 6.01 times. We found a compaction methodology for the volume reduction of powdered radioactive wastes, and their polymer solidification will be more effective to reduce the volume of radwastes to be disposed. After a characterization of the solidified waste form incorporated pellets (including sintered pellets), this methodology will be applied to treat depleted uranium wastes used as catalyst, and to solve the problem of NPPs' polymer solidification system, as mentioned above. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1993

Kinematics and aerodynamics of the velocity vector roll

The velocity vector roll is an angular rotation of an aircraft about its instantaneous velocity vector, constrained to be performed at constant angle-of-attack (AOA), no sideslip, and constant velocity. Consideration of the aerodynamic force equations leads to requirements for body-axis yawing and pitching rotations that satisfy these constraints. Here, the body axis rotations, and the constraints, are used in the moment equations to determine the aerodynamic moments required to perform the velocity vector roll. For representative tactical aircraft, the conditions for maximum pitching moment are a function of orientation, occurring at about 90 deg of bank in a level trajectory. Maximum required pitching moment occurs at peak roll rate, and is achieved at AOA above 45 deg. The conditions for maximum rolling moment depend on the value of the roll mode time constant. For a small time constant (fast response) the maximum rolling moment occurs at maximum roll acceleration and zero AOA, largely independent of aircraft orientation; for a large time constant, maximum required rolling moment occurs at maximum roll rate, at maximum AOA, and at 180 deg of bank in level flight. Maximum yawing moment occurs at maximum roll acceleration, maximum AOA, and is largely independent of airplane orientation.

Durham, Wayne C.↗