Feasibility Assessment for Pressure Casting of Ceramic-Aluminum Composites for NASA's Propulsion Applications

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

2005-01-01

Feasibility assessment of pressure casting of ceramic-aluminum composites for NASA% propulsion applications is summarized. A combination of several demonstration projects to produce three unique components for liquid hydrogen-oxygen rocket engine% flanges, valves and turbo-pump housing are conducted. These components are made from boron carbide, silicon carbide and alumina powders fabricated into complex net shaped parts using dry green powder compaction, slip casting or a novel 3D ink-jet printing process, followed by sintering to produce performs that can be pressure cast by infiltration with molten aluminum. I n addition, joining techniques are also explored to insure that these components can be assembled into a structure without degrading their highly tailored properties. The feasibility assessment was made to determine if these new materials could provide a significant weight savings, thereby reducing vehicle launch costs, while being durable materials to increase safety and performance for propulsion system.

Real-time on-line ultrasonic monitoring for bubbles in ceramic 'slip' in pottery pipelines.

PubMed

Yim, Geun Tae; Leighton, Timothy G

2010-01-01

When casting ceramic items in potteries, liquid 'slip' is passed from a settling tank, through overhead pipelines, before being pumped manually into the moulds. It is not uncommon for bubbles to be introduced into the slip as it passes through the complex piping network, and indeed the presence of bubbles is a major source of financial loss to the ceramics industry worldwide. This is because the bubbles almost always remain undetected until after the ceramic items have been fired in a kiln, during which process bubbles expand and create unwanted holes in the pottery. Since there it is usually an interval of several hours between the injection of the slip into the moulds, and the inspection of the items after firing, such bubble generation goes undetected on the production line during the manufacture of hundreds or even thousands of ceramic units. Not only does this mean hours of wasted staff time, power consumption and production line time: the raw material which makes up these faulty items cannot even be recycled, as fired ceramic cannot be converted back into slip. Currently, the state-of-the-art method for detecting bubbles in the opaque ceramic slip is slow and invasive, can only be used off-line, and requires expertise which is rarely available. This paper describes the invention, engineering and in-factory testing across Europe of an ultrasonic system for real-time monitoring for the presence of bubbles in casting slip. It interprets changes in the scattering statistics accompanying the presence of the bubbles, the latter being detected through perturbations in the received signal when a narrow-band ultrasonic probing wave is transmitted through the slip. The device can be bolted onto the outside of the pipeline, or used in-line. It is automated, and requires no special expertise. The acoustic problems which had to be solved were severe, and included making the system capable of monitoring the slip regardless of the material of pipe (plastic, steel, etc.) and nature of the slip (which can be very variable). It must also be capable of detecting bubbles amongst the myriad solid particles and other species present in the flowing slip. The completed prototype was tested around several factories in Europe, and proved not only to be more versatile, but also more sensitive, than the state-of-the-art method.

Slip casting and extruding shapes of rhenium with metal oxide additives. 1: Feasibility demonstration

NASA Technical Reports Server (NTRS)

Barr, F. A.; Page, R. J.

1986-01-01

The feasibility of fabricating small rhenium parts with metal oxide additives by means of slip casting and extrusion techniques is described. The metal oxides, ZrO2 and HfO2 were stabilized into the cubic phase with Y2O3. Additions of metal oxide to the rhenium of up to 15 weight percent were used. Tubes of 17 mm diameter with 0.5 mm walls were slip cast by adapting current ceramic oxide techniques. A complete cast double conical nozzle demonstrated the ability to meet shapes and tolerances. Extrusion of meter long tubing lengths of 3.9 mm o.d. x 2.3 mm i.d. final dimension is documented. Sintering schedules are presented to produce better than 95% of theoretical density parts. Finished machining was found possible were requried by electric discharge machining and diamond grinding.

Slip casting and nitridation of silicon powder

NASA Technical Reports Server (NTRS)

Seiko, Y.

1985-01-01

Powdered Silicon was slip-cast with a CaSO4 x 0.5H2O mold and nitrided in a N atm. containing 0 or 5 vol. % H at 1000 to 1420 deg. To remove the castings, the modeling faces were coated successively with an aq. salt soap and powdered cellulose containing Na alginate, and thus prevented the sticking problem.

Oxidation resistant coatings for ceramic matrix composite components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaubert, V.M.; Stinton, D.P.; Hirschfeld, D.A.

Corrosion resistant Ca{sub 0.6}Mg{sub 0.4}Zr{sub 4}(PO{sub 4}){sub 6} (CMZP) and Ca{sub 0.5}Sr{sub 0.5}Zr{sub 4}(PO{sub 4}){sub 6} (CS-50) coatings for fiber-reinforced SiC-matrix composite heat exchanger tubes have been developed. Aqueous slurries of both oxides were prepared with high solids loading. One coating process consisted of dipping the samples in a slip. A tape casting process has also been created that produced relatively thin and dense coatings covering a large area. A processing technique was developed, utilizing a pre-sintering step, which produced coatings with minimal cracking.

Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds.

PubMed

Rowthu, Sriharitha; Böhlen, Karl; Bowen, Paul; Hoffmann, Patrik

2015-11-11

Ceramic surface microstructuring is a rapidly growing field with a variety of applications in tribology, wetting, biology, and so on. However, there are limitations to large-area microstructuring and fabrication of three-dimensional (3D) micro free forms. Here, we present a route to obtain intricate surface structures through in situ slip casting using polydimethylsiloxane (PDMS) negative molds which are replicated from excimer laser ablated polycarbonate (PC) master molds. PC sheets are ablated with a nanosecond KrF (λ = 248 nm) excimer laser mask projection system to obtain micron-scale 3D surface features over a large area of up to 3 m(2). Complex surface structures that include 3D free forms such as 3D topography of Switzerland, shallow structures such as diffractive optical elements (60 nm step) and conical micropillars have been obtained. The samples are defect-free produced with thicknesses of up to 10 mm and 120 mm diameter. The drying process of the slip cast alumina slurry takes place as a one-dimensional process, through surface evaporation and water permeation through the PDMS membrane. This allows homogeneous one-dimensional shrinkage during the drying process, independent of the sample's lateral dimensions. A linear mass diffusion model has been proposed to predict and explain the drying process of these ceramic colloidal suspensions. The calculated drying time is linearly proportional to the height of the slurry and the thickness of the negatively structured PDMS and is validated by the experimental results. An experimentally observed optimum Sylgard PDMS thickness range of ∼400 μm to 1 mm has achieved the best quality microstructured green compacts. Further, the model predicts that the drying time is independent of the microstructured areas and was validated using experimental observations carried out with microstructured areas of 300 mm(2), 1200 mm(2), and 120 cm(2). Therefore, in principle, the structures can be further replicated in areas up to 3 m(2) with the same drying time for the same slurry height. The surface-structured ceramics display interesting wetting properties, for example, eicosane-coated mesoporous microstructured alumina shows superhydrophobic behavior. Additionally, ceramic bulk samples could be further used as second-generation very hard and low-wear molds for further microfabrication.

Encapsulation of ZnO particles by metal fluorides: Towards an application as transparent insulating coatings for windows

NASA Astrophysics Data System (ADS)

Trenque, Isabelle; Mornet, Stéphane; Duguet, Etienne; Majimel, Jérôme; Brüll, Annelise; Teinz, Katharina; Kemnitz, Erhard; Gaudon, Manuel

2013-01-01

Because ZnO is a promising candidate for getting efficient films or varnishes with thermal insulating abilities for windows applications, the effect of the encapsulation of ZnO particles in shells of low refractive index material on the improvement of the visible light transmission was investigated. ZnO-MgF2 core-shell particles were synthesized by deposition of fluoride sols on ZnO particles through a vacuum slip casting process like. The transmission behaviours were first indirectly studied by diffuse reflexion measurements on powder beds. Then, particle films were elaborated by a screen printing process which ensured direct transmission measurements. The encapsulation of ZnO particles with a coating shell of 1.3 wt.% of MgF2 improves the visible light transmission of 32%.

Non-rigid Reconstruction of Casting Process with Temperature Feature

NASA Astrophysics Data System (ADS)

Lin, Jinhua; Wang, Yanjie; Li, Xin; Wang, Ying; Wang, Lu

2017-09-01

Off-line reconstruction of rigid scene has made a great progress in the past decade. However, the on-line reconstruction of non-rigid scene is still a very challenging task. The casting process is a non-rigid reconstruction problem, it is a high-dynamic molding process lacking of geometric features. In order to reconstruct the casting process robustly, an on-line fusion strategy is proposed for dynamic reconstruction of casting process. Firstly, the geometric and flowing feature of casting are parameterized in manner of TSDF (truncated signed distance field) which is a volumetric block, parameterized casting guarantees real-time tracking and optimal deformation of casting process. Secondly, data structure of the volume grid is extended to have temperature value, the temperature interpolation function is build to generate the temperature of each voxel. This data structure allows for dynamic tracking of temperature of casting during deformation stages. Then, the sparse RGB features is extracted from casting scene to search correspondence between geometric representation and depth constraint. The extracted color data guarantees robust tracking of flowing motion of casting. Finally, the optimal deformation of the target space is transformed into a nonlinear regular variational optimization problem. This optimization step achieves smooth and optimal deformation of casting process. The experimental results show that the proposed method can reconstruct the casting process robustly and reduce drift in the process of non-rigid reconstruction of casting.

CASTING SLIPS FOR FABRICATION OF REFRACTORY METAL WARE

DOEpatents

Stoddard, S.D.; Nuckolls, D.E.; Cowan, R.E.

1962-09-01

A composition is given for slip casting tungsten metal. The composition consists essentially of tungsten metal with an average particle size of 0.9 micron, an organic vehicle such as methyl chloroform, o-xylene, n-butyl acetate, isobutyl acetate, and 1, 1, 2, 2-tetrachlorethane, and a suspending agent such as ethyl cellulose, with the approximate ratio of said vehicle to the tungsten metal being 12 cc of a solution containing from 5 to about 20 grams of said ethyl cellulose in 400 cc of said organic vehicle per 100 grams of metal. (AEC)

Method for making thick and/or thin film

DOEpatents

Pham, Ai Quoc; Glass, Robert S.

2004-11-02

A method to make thick or thin films a very low cost. The method is generally similar to the conventional tape casting techniques while being more flexible and versatile. The invention involves preparing a slip (solution) of desired material and including solvents such as ethanol and an appropriate dispersant to prevent agglomeration. The slip is then sprayed on a substrate to be coated using an atomizer which spreads the slip in a fine mist. Upon hitting the substrate, the solvent evaporates, leaving a green tape containing the powder and other additives, whereafter the tape may be punctured, cut, and heated for the desired application. The tape thickness can vary from about 1 .mu.m upward.

Process for Making Ceramic Mold

NASA Technical Reports Server (NTRS)

Buck, Gregory M. (Inventor); Vasquez, Peter (Inventor)

2001-01-01

An improved process for slip casting molds that can be more economically automated and that also exhibits greater dimensional stability is disclosed. The process involves subjecting an investment pattern, preferably made from wax, to successive cycles of wet-dipping in a slurry of colloidal, silica-based binder and dry powder-coating, or stuccoing with plaster of Paris or calcium sulfate mixtures to produce a multi-layer shell over the pattern. The invention as claimed entails applying a primary and a secondary coating to the investment pattern. At least two wet-dipping on in a primary slurry and dry-stuccoing cycles provide the primary coating, and an additional two wet-dippings and dry-stuccoing cycles provide the secondary, or back-up, coating. The primary and secondary coatings produce a multi-layered shell pattern. The multi-layered shell pattern is placed in a furnace first to cure and harden, and then to vaporize the investment pattern, leaving a detailed, high precision shell mold.

Netcast™ Shape Casting Technology: A Technological Breakthrough that Enhances the Cost Effectiveness of Aluminum Forgings

NASA Astrophysics Data System (ADS)

Anderson, Mark; Bruski, Richard; Groszkiewicz, Daniel; Wagstaff, Bob

A new Direct Chill (DC) casting process is introduced to semi-continuous casting where near net shaped ingots are solidified. This process is currently being used at Alcan Engineered Cast Products (ECP) facility in Jonquiere, Canada, sectioned, then forged at Alcoa Automotive, Kentucky Casting Center (KCC). Finished forgings are machined and assembled into the Ford D/EW98 platform as suspension components. A brief description of the process and the implications on the forging process are presented.

[Effects of three types of veneering porcelain on bending strength of KAVO(TM) Y-TZP/porcelain bilayered structure].

PubMed

Ma, Ting-ting; Yi, Yuan-fu; Shao, Long-quan; Tian, Jie-mo; Hou, Kang-lin; Zhang, Wei-wei; Wen, Ning; Deng, Bin

2010-10-01

To investigate the effect of three types of veneering porcelain on the bending strength of KAVO Y-TZP/porcelain layered structure. KAVO zirconia ceramics were used as the substructure. To form Y-TZP/porcelain bilayered structure, a leucite-based veneering porcelain was fired on the zirconia substructures by slip-casting technique with dentin washbake, and two nano-fluorapatite-based veneering porcelains were fired on the zirconia substructures by either slip-casting or pressed-on technique with or without liner coverage. The bending strength was tested according to ISO 6872 standard, and the veneered surfaces of the fracture samples were analyzed by scanning electron microscopy (SEM). For covering KAVO zirconia core material, the conventional veneering slurry-porcelain combined with liner or wash firing had significant higher bending strength than pressed-on porcelain. SEM showed that the main failure type at the interface was adhesive failure. Thin layer sintering using washbake program or liner on KAVO zirconia surface increases the surface wettability, and this procedure may be indispensable when veneering on the surface of dental zirconia.

Improving Metal Casting Process

NASA Technical Reports Server (NTRS)

1998-01-01

Don Sirois, an Auburn University research associate, and Bruce Strom, a mechanical engineering Co-Op Student, are evaluating the dimensional characteristics of an aluminum automobile engine casting. More accurate metal casting processes may reduce the weight of some cast metal products used in automobiles, such as engines. Research in low gravity has taken an important first step toward making metal products used in homes, automobiles, and aircraft less expensive, safer, and more durable. Auburn University and industry are partnering with NASA to develop one of the first accurate computer model predictions of molten metals and molding materials used in a manufacturing process called casting. Ford Motor Company's casting plant in Cleveland, Ohio is using NASA-sponsored computer modeling information to improve the casting process of automobile and light-truck engine blocks.

Numerical simulation and optimization of casting process for complex pump

NASA Astrophysics Data System (ADS)

Liu, Xueqin; Dong, Anping; Wang, Donghong; Lu, Yanling; Zhu, Guoliang

2017-09-01

The complex shape of the casting pump body has large complicated structure and uniform wall thickness, which easy give rise to casting defects. The numerical simulation software ProCAST is used to simulate the initial top gating process, after analysis of the material and structure characteristics of the high-pressure pump. The filling process was overall smooth, not there the water shortage phenomenon. But the circular shrinkage defects appear at the bottom of casting during solidification process. Then, the casting parameters were optimized and adding cold iron in the bottom. The shrinkage weight was reduced from 0.00167g to 0.0005g. The porosity volume was reduced from 1.39cm3 to 0.41cm3. The optimization scheme is simulated and actual experimented. The defect has been significantly improved.

High purity silica reflective heat shield development

NASA Technical Reports Server (NTRS)

Nachtscheim, P. R.; Blome, J. C.

1976-01-01

A hyperpure vitreous silica material is being developed for use as a reflective and ablative heat shield for planetary entry. Various purity grades and forms of raw materials were evaluated along with various processing methods. Slip casting of high purity grain was selected as the best processing method, resulting in a highly reflective material in the wavelength bands of interest (the visible and ultraviolet regions). The selected material was characterized with respect to optical, mechanical and physical properties using a limited number of specimens. The process has been scaled up to produce a one-half scale heat shield (18 in. dia.) (45.72 cm) for a Jupiter entry vehicle. This work is now being extended to improve the structural safety factor of the heat shield by making hyperpure silica material tougher through the addition of silica fibers.

Simulation of the Continuous Casting and Cooling Behavior of Metallic Glasses

PubMed Central

Pei, Zhipu; Ju, Dongying

2017-01-01

The development of melt spinning technique for preparation of metallic glasses was summarized. The limitations as well as restrictions of the melt spinning embodiments were also analyzed. As an improvement and variation of the melt spinning method, the vertical-type twin-roll casting (VTRC) process was discussed. As the thermal history experienced by the casting metals to a great extent determines the qualities of final products, cooling rate in the quenching process is believed to have a significant effect on glass formation. In order to estimate the ability to produce metallic glasses by VTRC method, temperature and flow phenomena of the melt in molten pool were computed, and cooling rates under different casting conditions were calculated with the simulation results. Considering the fluid character during casting process, the material derivative method based on continuum theory was adopted in the cooling rate calculation. Results show that the VTRC process has a good ability in continuous casting metallic glassy ribbons. PMID:28772779

Thin Gauge Twin-Roll Casting, Process Capabilities and Product Quality

NASA Astrophysics Data System (ADS)

Daaland, O.; Espedal, A. B.; Nedreberg, M. L.; Alvestad, I.

Traditionally industrial twin roll casters have been operated at gauges 6-10 mm, depending on the type of caster and the final product requirements. Over the past few years it has become apparent that a significant increase in productivity can be achieved when the casting gauge is reduced. Hydro Aluminium embarked on an extensive research and development, thin gauge casting programme, in the beginning of the 1990's and this paper presents some results from a five year lasting project (joint programme between Hydro Aluminium a.s. and Lauener Engineering). Based on more than 400 casting trials the major benefits and limitations of casting at reduced gauge and increased speed are outlined. Important aspects related to process development and product quality are discussed including: productivity and limitations, surface defects, microstructural characteristics, cooling rates and dendrite structure, segregation behaviour and mechanical properties after thermo-mechanical processing. Results for casting of several alloys are given. Additionally, numerical modelling results of the strip casting process are included.

Modelling the Cast Component Weight in Hot Chamber Die Casting using Combined Taguchi and Buckingham's π Approach

NASA Astrophysics Data System (ADS)

Singh, Rupinder

2018-02-01

Hot chamber (HC) die casting process is one of the most widely used commercial processes for the casting of low temperature metals and alloys. This process gives near-net shape product with high dimensional accuracy. However in actual field environment the best settings of input parameters is often conflicting as the shape and size of the casting changes and one have to trade off among various output parameters like hardness, dimensional accuracy, casting defects, microstructure etc. So for online inspection of the cast components properties (without affecting the production line) the weight measurement has been established as one of the cost effective method (as the difference in weight of sound and unsound casting reflects the possible casting defects) in field environment. In the present work at first stage the effect of three input process parameters (namely: pressure at 2nd phase in HC die casting; metal pouring temperature and die opening time) has been studied for optimizing the cast component weight `W' as output parameter in form of macro model based upon Taguchi L9 OA. After this Buckingham's π approach has been applied on Taguchi based macro model for the development of micro model. This study highlights the Taguchi-Buckingham based combined approach as a case study (for conversion of macro model into micro model) by identification of optimum levels of input parameters (based on Taguchi approach) and development of mathematical model (based on Buckingham's π approach). Finally developed mathematical model can be used for predicting W in HC die casting process with more flexibility. The results of study highlights second degree polynomial equation for predicting cast component weight in HC die casting and suggest that pressure at 2nd stage is one of the most contributing factors for controlling the casting defect/weight of casting.

Simulation of the Continuous Casting and Cooling Behavior of Metallic Glasses.

PubMed

Pei, Zhipu; Ju, Dongying

2017-04-17

The development of melt spinning technique for preparation of metallic glasses was summarized. The limitations as well as restrictions of the melt spinning embodiments were also analyzed. As an improvement and variation of the melt spinning method, the vertical-type twin-roll casting (VTRC) process was discussed. As the thermal history experienced by the casting metals to a great extent determines the qualities of final products, cooling rate in the quenching process is believed to have a significant effect on glass formation. In order to estimate the ability to produce metallic glasses by VTRC method, temperature and flow phenomena of the melt in molten pool were computed, and cooling rates under different casting conditions were calculated with the simulation results. Considering the fluid character during casting process, the material derivative method based on continuum theory was adopted in the cooling rate calculation. Results show that the VTRC process has a good ability in continuous casting metallic glassy ribbons.

Prediction of Shrinkage Porosity Defect in Sand Casting Process of LM25

NASA Astrophysics Data System (ADS)

Rathod, Hardik; Dhulia, Jay K.; Maniar, Nirav P.

2017-08-01

In the present worldwide and aggressive environment, foundry commercial enterprises need to perform productively with least number of rejections and create casting parts in shortest lead time. It has become extremely difficult for foundry industries to meet demands of defects free casting and meet strict delivery schedules. The process of casting solidification is complex in nature. Prediction of shrinkage defect in metal casting is one of the critical concern in foundries and is one of the potential research areas in casting. Due to increasing pressure to improve quality and to reduce cost, it is very essential to upgrade the level of current methodology used in foundries. In the present research work, prediction methodology of shrinkage porosity defect in sand casting process of LM25 using experimentation and ANSYS is proposed. The objectives successfully achieved are prediction of shrinkage porosity distribution in Al-Si casting and determining effectiveness of investigated function for predicting shrinkage porosity by correlating results of simulating studies to those obtained experimentally. The real-time application of the research reflects from the fact that experimentation is performed on 9 different Y junctions at foundry industry and practical data obtained from experimentation are used for simulation.

Fabrication of silk fibroin film using centrifugal casting technique for corneal tissue engineering.

PubMed

Lee, Min Chae; Kim, Dong-Kyu; Lee, Ok Joo; Kim, Jung-Ho; Ju, Hyung Woo; Lee, Jung Min; Moon, Bo Mi; Park, Hyun Jung; Kim, Dong Wook; Kim, Su Hyeon; Park, Chan Hum

2016-04-01

Films prepared from silk fibroin have shown potential as biomaterials in tissue engineering applications for the eye. Here, we present a novel process for fabrication of silk fibroin films for corneal application. In this work, fabrication of silk fibroin films was simply achieved by centrifugal force. In contrast to the conventional dry casting method, we carried out the new process in a centrifuge with a rotating speed of 4000 rpm, where centrifugal force was imposed on an aluminum tube containing silk fibroin solution. In the present study, we also compared the surface roughness, mechanical properties, transparency, and cell proliferation between centrifugal and dry casting method. In terms of surface morphology, films fabricated by the centrifugal casting have less surface roughness than those by the dry casting. For elasticity and transparency, silk fibroin films obtained from the centrifugal casting had favorable results compared with those prepared by dry casting. Furthermore, primary human corneal keratocytes grew better in films prepared by the centrifugal casting. Therefore, our results suggest that this new fabrication process for silk fibroin films offers important potential benefits for corneal tissue regeneration. © 2015 Wiley Periodicals, Inc.

Lightweight Concrete Produced Using a Two-Stage Casting Process.

PubMed

Yoon, Jin Young; Kim, Jae Hong; Hwang, Yoon Yi; Shin, Dong Kyu

2015-03-25

The type of lightweight aggregate and its volume fraction in a mix determine the density of lightweight concrete. Minimizing the density obviously requires a higher volume fraction, but this usually causes aggregates segregation in a conventional mixing process. This paper proposes a two-stage casting process to produce a lightweight concrete. This process involves placing lightweight aggregates in a frame and then filling in the remaining interstitial voids with cementitious grout. The casting process results in the lowest density of lightweight concrete, which consequently has low compressive strength. The irregularly shaped aggregates compensate for the weak point in terms of strength while the round-shape aggregates provide a strength of 20 MPa. Therefore, the proposed casting process can be applied for manufacturing non-structural elements and structural composites requiring a very low density and a strength of at most 20 MPa.

Development of the Electromagnetic Continuous Casting Technology for of Magnesium Alloys

NASA Astrophysics Data System (ADS)

Park, Joon-Pyo; Kim, Myoung-Gyun; Kim, Jong-Ho; Lee, Gyu-Chang

Currently, magnesium billets produced by ingot casting or direct chill casting process, result in low-quality surfaces and low productivity, Continuous casting technology to solve these problem has not only high-quality surface billets with fine-grained and homogeneous microstructure but also cost down. The latent heat of fusion per weight (J/g) of magnesium is similar to other metals, however, considering the heat emitted to the mold surface during continuous casting in meniscus region and converting it to the latent heat of fusion per volume, magnesium will be rapidly solidified in the mold during continuous casting, which induces subsequent surface defect formation. In this study, electromagnetic casting and stirring (EMC and EMS) techniques are proposed to control solidification process conveniently by compensating the low latent heat of solidification by volume and to fabricate magnesium billet with high-quality surface. This technique was extended to large scale billets up to 300 mm diameter and continuous casting was successfully conducted. Then magnesium billet was used for the fabrication of prototype automobile pulley.

Method to prevent/mitigate steam explosions in casting pits

DOEpatents

Taleyarkhan, Rusi P.

1996-01-01

Steam explosions can be prevented or mitigated during a metal casting process by the placement of a perforated flooring system in the casting pit. An upward flow of compressed gas through this perforated flooring system is introduced during the casting process to produce a buffer layer between any spilled molten metal and the cooling water in the reservoir. This buffer layer provides a hydrodynamic layer which acts to prevent or mitigate steam explosions resulting from hot, molten metal being spilled into or onto the cooling water.

Slip Casting and Green Body Evaluation of 6% Yttria, 2% Alumina Silicon Nitride

DTIC Science & Technology

1991-12-01

Slurries containing this lignosulphonate wood derivative did not exhibit uniform rheological behavior. Some of the slips with high solids...the Figure 3 axes for easier comparison. Reference 2 also notes a marked shear-sensitivity decrease in slurries containing a lignosulphonate dispersant...Any advantage to using lignosulphonate dispersants must be weighed against the difficulty of burning the additives out of the resultant green bodies

Development of an Optimization Methodology for the Aluminum Alloy Wheel Casting Process

NASA Astrophysics Data System (ADS)

Duan, Jianglan; Reilly, Carl; Maijer, Daan M.; Cockcroft, Steve L.; Phillion, Andre B.

2015-08-01

An optimization methodology has been developed for the aluminum alloy wheel casting process. The methodology is focused on improving the timing of cooling processes in a die to achieve improved casting quality. This methodology utilizes (1) a casting process model, which was developed within the commercial finite element package, ABAQUS™—ABAQUS is a trademark of Dassault Systèms; (2) a Python-based results extraction procedure; and (3) a numerical optimization module from the open-source Python library, Scipy. To achieve optimal casting quality, a set of constraints have been defined to ensure directional solidification, and an objective function, based on the solidification cooling rates, has been defined to either maximize, or target a specific, cooling rate. The methodology has been applied to a series of casting and die geometries with different cooling system configurations, including a 2-D axisymmetric wheel and die assembly generated from a full-scale prototype wheel. The results show that, with properly defined constraint and objective functions, solidification conditions can be improved and optimal cooling conditions can be achieved leading to process productivity and product quality improvements.

Experimental Studies of Heat-Transfer Behavior at a Casting/Water-Cooled-Mold Interface and Solution of the Heat-Transfer Coefficient

NASA Astrophysics Data System (ADS)

Zeng, Y. D.; Wang, F.

2018-02-01

In this paper, we propose an experimental model for forming an air gap at the casting/mold interface during the solidification process of the casting, with the size and formation time of the air gap able to be precisely and manually controlled. Based on this model, experiments of gravity casting were performed, and on the basis of the measured temperatures at different locations inside the casting and the mold, the inverse analysis method of heat transfer was applied to solve for the heat-transfer coefficient at the casting/mold interface during the solidification process. Furthermore, the impacts of the width and formation time of the air gap on the interface heat-transfer coefficient (IHTC) were analyzed. The results indicate that the experimental model succeeds in forming an air gap having a certain width at any moment during solidification of the casting, thus allowing us to conveniently and accurately study the impact of the air gap on IHTC using the model. In addition, the casting/mold IHTC is found to first rapidly decrease as the air gap forms and then slowly decrease as the solidification process continues. Moreover, as the width of the air gap and the formation time of the air gap increase, the IHTC decreases.

Lightweight Concrete Produced Using a Two-Stage Casting Process

PubMed Central

Yoon, Jin Young; Kim, Jae Hong; Hwang, Yoon Yi; Shin, Dong Kyu

2015-01-01

The type of lightweight aggregate and its volume fraction in a mix determine the density of lightweight concrete. Minimizing the density obviously requires a higher volume fraction, but this usually causes aggregates segregation in a conventional mixing process. This paper proposes a two-stage casting process to produce a lightweight concrete. This process involves placing lightweight aggregates in a frame and then filling in the remaining interstitial voids with cementitious grout. The casting process results in the lowest density of lightweight concrete, which consequently has low compressive strength. The irregularly shaped aggregates compensate for the weak point in terms of strength while the round-shape aggregates provide a strength of 20 MPa. Therefore, the proposed casting process can be applied for manufacturing non-structural elements and structural composites requiring a very low density and a strength of at most 20 MPa. PMID:28788007

Software Analytical Instrument for Assessment of the Process of Casting Slabs

NASA Astrophysics Data System (ADS)

Franěk, Zdeněk; Kavička, František; Štětina, Josef; Masarik, Miloš

2010-06-01

The paper describes the original proposal of ways of solution and function of the program equipment for assessment of the process of casting slabs. The program system LITIOS was developed and implemented in EVRAZ Vitkovice Steel Ostrava on the equipment of continuous casting of steel (further only ECC). This program system works on the data warehouse of technological parameters of casting and quality parameters of slabs. It enables an ECC technologist to analyze the course of casting melt and with using statistics methods to set the influence of single technological parameters on the duality of final slabs. The system also enables long term monitoring and optimization of the production.

Process for forming a long gas turbine engine blade having a main wall with a thin portion near a tip

DOEpatents

Campbell, Christian X; Thomaidis, Dimitrios

2014-05-13

A process is provided for forming an airfoil for a gas turbine engine involving: forming a casting of a gas turbine engine airfoil having a main wall and an interior cavity, the main wall having a wall thickness extending from an external surface of the outer wall to the interior cavity, an outer section of the main wall extending from a location between a base and a tip of the airfoil casting to the tip having a wall thickness greater than a final thickness. The process may further involve effecting movement, using a computer system, of a material removal apparatus and the casting relative to one another such that a layer of material is removed from the casting at one or more radial portions along the main wall of the casting.

Simulation of cracking cores when molding piston components

NASA Astrophysics Data System (ADS)

Petrenko, Alena; Soukup, Josef

2014-08-01

The article deals with pistons casting made from aluminum alloy. Pistons are casting at steel mold with steel core. The casting is provided by gravity casting machine. The each machine is equipped by two metal molds, which are preheated above temperature 160 °C before use. The steel core is also preheated by flame. The metal molds and cores are heated up within the casting process. The temperature of the metal mold raise up to 200 °C and temperature of core is higher. The surface of the core is treated by nitration. The mold and core are cooled down by water during casting process. The core is overheated and its top part is finally cracked despite its intensive water-cooling. The life time cycle of the core is decreased to approximately 5 to 15 thousands casting, which is only 15 % of life time cycle of core for production of other pistons. The article presents the temperature analysis of the core.

Effects of process variables on the properties of YBa2Cu3O(7-x) ceramics formed by investment casting

NASA Technical Reports Server (NTRS)

Hooker, M. W.; Taylor, T. D.; Leigh, H. D.; Wise, S. A.; Buckley, J. D.; Vasquez, P.; Buck, G. M.; Hicks, L. P.

1993-01-01

An investment casting process has been developed to produce net-shape, superconducting ceramics. In this work, a factorial experiment was performed to determine the critical process parameters for producing cast YBa2Cu3O7 ceramics with optimum properties. An analysis of variance procedure indicated that the key variables in casting superconductive ceramics are the particle size distribution and sintering temperature. Additionally, the interactions between the sintering temperature and the other process parameters (e.g., particle size distribution and the use of silver dopants) were also found to influence the density, porosity, and critical current density of the fired ceramics.

Method to prevent/mitigate steam explosions in casting pits

DOEpatents

Taleyarkhan, R.P.

1996-12-24

Steam explosions can be prevented or mitigated during a metal casting process by the placement of a perforated flooring system in the casting pit. An upward flow of compressed gas through this perforated flooring system is introduced during the casting process to produce a buffer layer between any spilled molten metal and the cooling water in the reservoir. This buffer layer provides a hydrodynamic layer which acts to prevent or mitigate steam explosions resulting from hot, molten metal being spilled into or onto the cooling water. 3 figs.

Systems and methods for monitoring a solid-liquid interface

DOEpatents

Stoddard, Nathan G; Lewis, Monte A.; Clark, Roger F

2013-06-11

Systems and methods are provided for monitoring a solid-liquid interface during a casting process. The systems and methods enable determination of the location of a solid-liquid interface during the casting process.

Method for fabricating laminated uranium composites

DOEpatents

Chapman, L.R.

1983-08-03

The present invention is directed to a process for fabricating laminated composites of uranium or uranium alloys and at least one other metal or alloy. The laminated composites are fabricated by forming a casting of the molten uranium with the other metal or alloy which is selectively positioned in the casting and then hot-rolling the casting into a laminated plate in or around which the casting components are metallurgically bonded to one another to form the composite. The process of the present invention provides strong metallurgical bonds between the laminate components primarily since the bond disrupting surface oxides on the uranium or uranium alloy float to the surface of the casting to effectively remove the oxides from the bonding surfaces of the components.

Energy Consumption of Die Casting Operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jerald Brevick; clark Mount-Campbell; Carroll Mobley

2004-03-15

Molten metal processing is inherently energy intensive and roughly 25% of the cost of die-cast products can be traced to some form of energy consumption [1]. The obvious major energy requirements are for melting and holding molten alloy in preparation for casting. The proper selection and maintenance of melting and holding equipment are clearly important factors in minimizing energy consumption in die-casting operations [2]. In addition to energy consumption, furnace selection also influences metal loss due to oxidation, metal quality, and maintenance requirements. Other important factors influencing energy consumption in a die-casting facility include geographic location, alloy(s) cast, starting formmore » of alloy (solid or liquid), overall process flow, casting yield, scrap rate, cycle times, number of shifts per day, days of operation per month, type and size of die-casting form of alloy (solid or liquid), overall process flow, casting yield, scrap rate, cycle times, number of shifts per day, days of operation per month, type and size of die-casting machine, related equipment (robots, trim presses), and downstream processing (machining, plating, assembly, etc.). Each of these factors also may influence the casting quality and productivity of a die-casting enterprise. In a die-casting enterprise, decisions regarding these issues are made frequently and are based on a large number of factors. Therefore, it is not surprising that energy consumption can vary significantly from one die-casting enterprise to the next, and within a single enterprise as function of time.« less

Development of an Innovative Laser-Assisted Coating Process for Extending Lifetime of Metal Casting Dies. Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madhav Rao Gonvindaraju

1999-10-18

Die casting dies used in the metal casting industry fail due to thermal fatigue cracking accompanied by the presence of residual tensile stresses, corrosion, erosion and wear of die surfaces. This phase 1 SBIR Final Report summarize Karta Technologies research involving the development of an innovative laser coating technology for metal casting dies. The process involves depositing complex protective coatings of nanocrystalline powders of TiC followed by a laser shot peening. The results indicate a significant improvement in corrosion and erosion resistance in molten aluminum for H13 die casting die steels. The laser-coated samples also showed improved surface finish, amore » homogeneous and uniform coating mircrostructure. The technology developed in this research can have a significant impact on the casting industry by saving the material costs involved in replacing dies, reducing downtime and improving the quality.« less

New Tubular Ceramic Membranes from Natural Moroccan Clay for Microfiltration Application

NASA Astrophysics Data System (ADS)

Ait Taleb, A.; El Baraka, N.; Saffaj, N.; Laknifli, A.; Mamouni, R.; Fatni, A.; El Hammadi, A.; El Qacimi, N.

2018-05-01

This paper is devoted the preparation of low cost microfiltration membranes using Moroccan clay powder. The preparation of membrane was composed with two steps: First a macroporous tubular support with a pore diameter 10 μm and porosity 43%. Secondly a microfiltration layer was performed by the slip casting method. A deflocculated slip was obtained by mixing mineral powder of ZrO2, PVA (polyvinyl alcohol) and water, after drying at room temperature for 24 h, the microfiltration layer was heated to 800°C for consolidation. Scanning electron microscopy observation showed homogeneous layers without cracks with an average pore diameter of 0.19 μm for the active layer. Water permeability obtained is about 841 L/h.m2.bar. The membranes have been tested to cleaning of colored wastewater.

Advances in multi-scale modeling of solidification and casting processes

NASA Astrophysics Data System (ADS)

Liu, Baicheng; Xu, Qingyan; Jing, Tao; Shen, Houfa; Han, Zhiqiang

2011-04-01

The development of the aviation, energy and automobile industries requires an advanced integrated product/process R&D systems which could optimize the product and the process design as well. Integrated computational materials engineering (ICME) is a promising approach to fulfill this requirement and make the product and process development efficient, economic, and environmentally friendly. Advances in multi-scale modeling of solidification and casting processes, including mathematical models as well as engineering applications are presented in the paper. Dendrite morphology of magnesium and aluminum alloy of solidification process by using phase field and cellular automaton methods, mathematical models of segregation of large steel ingot, and microstructure models of unidirectionally solidified turbine blade casting are studied and discussed. In addition, some engineering case studies, including microstructure simulation of aluminum casting for automobile industry, segregation of large steel ingot for energy industry, and microstructure simulation of unidirectionally solidified turbine blade castings for aviation industry are discussed.

Benefit from NASA

NASA Image and Video Library

1998-01-01

Don Sirois, an Auburn University research associate, and Bruce Strom, a mechanical engineering Co-Op Student, are evaluating the dimensional characteristics of an aluminum automobile engine casting. More accurate metal casting processes may reduce the weight of some cast metal products used in automobiles, such as engines. Research in low gravity has taken an important first step toward making metal products used in homes, automobiles, and aircraft less expensive, safer, and more durable. Auburn University and industry are partnering with NASA to develop one of the first accurate computer model predictions of molten metals and molding materials used in a manufacturing process called casting. Ford Motor Company's casting plant in Cleveland, Ohio is using NASA-sponsored computer modeling information to improve the casting process of automobile and light-truck engine blocks.

High-temperature ceramic heat exchanger element for a solar thermal receiver

NASA Technical Reports Server (NTRS)

Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

1982-01-01

A study has been completed on the development of a high-temperature ceramic heat exchanger element to be integrated into a solar reciver producing heated air. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The ceramic shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is fabricated by an innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. Fabrication of a one-half scale demonstrator ceramic receiver has been completed.

Thermodynamic Behavior Research Analysis of Twin-roll Casting Lead Alloy Strip Process

NASA Astrophysics Data System (ADS)

Jiang, Chengcan; Rui, Yannian

2017-03-01

The thermodynamic behavior of twin-roll casting (TRC) lead alloy strip process directly affects the forming of the lead strip, the quality of the lead strip and the production efficiency. However, there is little research on the thermodynamics of lead alloy strip at home and abroad. The TRC lead process is studied in four parameters: the pouring temperature of molten lead, the depth of molten pool, the roll casting speed, and the rolling thickness of continuous casting. Firstly, the thermodynamic model for TRC lead process is built. Secondly, the thermodynamic behavior of the TRC process is simulated with the use of Fluent. Through the thermodynamics research and analysis, the process parameters of cast rolling lead strip can be obtained: the pouring temperature of molten lead: 360-400 °C, the depth of molten pool: 250-300 mm, the roll casting speed: 2.5-3 m/min, the rolling thickness: 8-9 mm. Based on the above process parameters, the optimal parameters(the pouring temperature of molten lead: 375-390 °C, the depth of molten pool: 285-300 mm, the roll casting speed: 2.75-3 m/min, the rolling thickness: 8.5-9 mm) can be gained with the use of the orthogonal experiment. Finally, the engineering test of TRC lead alloy strip is carried out and the test proves the thermodynamic model is scientific, necessary and correct. In this paper, a detailed study on the thermodynamic behavior of lead alloy strip is carried out and the process parameters of lead strip forming are obtained through the research, which provide an effective theoretical guide for TRC lead alloy strip process.

Dimensional control of die castings

NASA Astrophysics Data System (ADS)

Karve, Aniruddha Ajit

The demand for net shape die castings, which require little or no machining, is steadily increasing. Stringent customer requirements are forcing die casters to deliver high quality castings in increasingly short lead times. Dimensional conformance to customer specifications is an inherent part of die casting quality. The dimensional attributes of a die casting are essentially dependent upon many factors--the quality of the die and the degree of control over the process variables being the two major sources of dimensional error in die castings. This study focused on investigating the nature and the causes of dimensional error in die castings. The two major components of dimensional error i.e., dimensional variability and die allowance were studied. The major effort of this study was to qualitatively and quantitatively study the effects of casting geometry and process variables on die casting dimensional variability and die allowance. This was accomplished by detailed dimensional data collection at production die casting sites. Robust feature characterization schemes were developed to describe complex casting geometry in quantitative terms. Empirical modeling was utilized to quantify the effects of the casting variables on dimensional variability and die allowance for die casting features. A number of casting geometry and process variables were found to affect dimensional variability in die castings. The dimensional variability was evaluated by comparisons with current published dimensional tolerance standards. The casting geometry was found to play a significant role in influencing the die allowance of the features measured. The predictive models developed for dimensional variability and die allowance were evaluated to test their effectiveness. Finally, the relative impact of all the components of dimensional error in die castings was put into perspective, and general guidelines for effective dimensional control in the die casting plant were laid out. The results of this study will contribute to enhancement of dimensional quality and lead time compression in the die casting industry, thus making it competitive with other net shape manufacturing processes.

Producing thin strips by twin-roll casting—part I: Process aspects and quality issues

NASA Astrophysics Data System (ADS)

Li, Ben Q.

1995-05-01

This two-part paper discusses recent advances in research and development for the direct production of coilable thin strips by twin-roll casting in both the aluminum and steel industries. While the former is empowering the casters to approach the theoretical productivity limit, the latter is striving to put pilot casters into commercial operation. These intensive R&D efforts are derived from the advantages, both economic and metallurgical, offered by the process. As twin-roll casting combines solidification and hot rolling into a single operation, the process requires low capital investment and low operational cost. Also, because of the high solidification rate attained in the process, the thin strips produced have a refined metallurgical structure, characterized by columnar and equiaxed zones with fine intermetallic particles. The enthusiasm about twin-roll casting is now being spread worldwide. This paper focuses on the process aspects and quality control of twin-roll casting. Part II, which will appear in the August issue, will review process modeling and pilot-plant development activities.

Slip casting nano-particle powders for making transparent ceramics

DOEpatents

Kuntz, Joshua D [Livermore, CA; Soules, Thomas F [Livermore, CA; Landingham, Richard Lee [Livermore, CA; Hollingsworth, Joel P [Oakland, CA

2011-04-12

A method of making a transparent ceramic including the steps of providing nano-ceramic powders in a processed or unprocessed form, mixing the powders with de-ionized water, the step of mixing the powders with de-ionized water producing a slurry, sonifing the slurry to completely wet the powder and suspend the powder in the de-ionized water, separating very fine particles from the slurry, molding the slurry, and curing the slurry to produce the transparent ceramic.

Progress in net shape fabrication of alpha SiC turbine components

NASA Technical Reports Server (NTRS)

Storm, R. S.; Naum, R. G.

1983-01-01

The development status of component technology in an automotive gas turbine Ceramic Applications in Turbine Engines program is discussed, with attention to such materials and processes having a low cost, net shape fabrication potential as sintered alpha-SiC that has been fashioned by means of injection molding, slip casting, and isostatic pressing. The gas turbine elements produced include a gasifier turbine rotor, a turbine wheel, a connecting duct, a combustor baffle, and a transition duct.

Effect of mold designs on molten metal behaviour in high-pressure die casting

NASA Astrophysics Data System (ADS)

Ibrahim, M. D.; Rahman, M. R. A.; Khan, A. A.; Mohamad, M. R.; Suffian, M. S. Z. M.; Yunos, Y. S.; Wong, L. K.; Mohtar, M. Z.

2017-04-01

This paper presents a research study conducted in a local automotive component manufacturer that produces aluminium alloy steering housing local and global markets. This study is to investigate the effect of design modification of mold in die casting as to improve the production rate. Design modification is carried out on the casting shot of the mold. Computer flow simulation was carried out to study the flow of molten metal in the mold with respect to the mold design modification. The design parameters of injection speed, die temperature and clamping force has been included in the study. The result of the simulation showed that modifications of casting shot give significant impact towards the molten flow behaviour in casting process. The capabilities and limitations of die casting process simulation to conduct defect analysis had been optimized. This research will enhance the efficiency of the mass production of the industry of die casting with the understanding of defect analysis, which lies on the modification of the mold design, a way early in its stages of production.

AMCC casting development. Volume 1: Executive Summary

NASA Technical Reports Server (NTRS)

1995-01-01

The Advanced Combustion Chamber Casting (AMCC) has been a technically challenging part due to its size, configuration, and alloy type. The height and weight of the wax pattern assembly necessitated the development of a hollow gating system to ensure structural integrity of the shell throughout the investment process. The complexity in the jacket area of the casting required the development of an innovative casting technology that PCC has termed 'TGC' or Thermal Gradient Control. This method, of setting up thermal gradients in the casting during solidification, represents a significant process improvement for PCC and has been successfully implemented on other programs. Metallurgical integrity of the final four castings was very good. Only the areas of the parts that utilized 'TGC Shape & Location System #2' showed any significant areas of microshrinkage when evaluated by non-destructive tests. Alumina oxides detected by FPI on the 'float' surfaces (top sid surfaces of the casting during solidification) of the part were almost entirely less than the acceptance criteria of .032 inches in diameter. Destructive chem mill of the castings was required to determine the effect of the process variables used during the processing of these last four parts (with the exception of the 'Shape & Location of TGC' variable).

Combined electrochemical, sunlight-induced oxidation and biological process for the treatment of chloride containing textile effluent.

PubMed

Santhanam, Manikandan; Selvaraj, Rajeswari; Annamalai, Sivasankar; Sundaram, Maruthamuthu

2017-11-01

This study presents a combined electrochemical, sunlight-induced oxidation and biological process for the treatment of textile effluent. In the first step, RuO 2 -TiO 2 /Ti and Titanium were used as the electrodes in EO process and color removal was achieved in 40 min at an applied current density of 20 mA cm -2 . The EO process generated about 250 mg L -1 of active chlorine which hampered the subsequent biological treatment process. Thus, in the second step, sun light-induced photolysis (SLIP) is explored to remove hypochlorite present in the EO treated effluent. In the third step, the SLIP treated effluent was fed to laccase positive bacterial consortium for biological process. To assess the effect of SLIP in the overall process, experiments were carried out with and without SLIP process. In experiments without SLIP, sodium thiosulfate was used to remove active chlorine. HPLC analysis showed that SLIP integrated experiments achieved an overall dye component degradation of 71%, where as only 22% degradation was achieved in the absence of SLIP process. The improvement in degradation with SLIP process is attributed to the presence of ClO radicals which detected by EPR analysis. The oxidation of organic molecules during process was confirmed by FT-IR and GC-MS analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nick Cannell; Dr. Mark Samonds; Adi Sholapurwalla

The investment casting process is an expendable mold process where wax patterns of the part and rigging are molded, assembled, shelled and melted to produce a ceramic mold matching the shape of the component to be cast. Investment casting is an important manufacturing method for critical parts because of the ability to maintain dimensional shape and tolerances. However, these tolerances can be easily exceeded if the molding components do not maintain their individual shapes well. In the investment casting process there are several opportunities for the final casting shape to not maintain the intended size and shape, such as shrinkagemore » of the wax in the injection tool, the modification of the shape during shell heating, and with the thermal shrink and distortion in the casting process. Studies have been completed to look at the casting and shell distortions through the process in earlier phases of this project. Dr. Adrian Sabau at Oak Ridge National Labs performed characterizations and validations of 17-4 PH stainless steel in primarily fused silica shell systems with good agreement between analysis results and experimental data. Further tasks provided material property measurements of wax and methodology for employing a viscoelastic definition of wax materials into software. The final set of tasks involved the implementation of the findings into the commercial casting analysis software ProCAST, owned and maintained by ESI Group. This included: o the transfer of the wax material property data from its raw form into separate temperature-dependent thermophysical and mechanical property datasets o adding this wax material property data into an easily viewable and modifiable user interface within the pre-processing application of the ProCAST suite, namely PreCAST o and validating the data and viscoelastic wax model with respect to experimental results« less

Selective Emitters for High Efficiency TPV Conversion: Materials Preparation and Characterisation

NASA Astrophysics Data System (ADS)

Diso, D.; Licciulli, A.; Bianco, A.; Leo, G.; Torsello, G.; Tundo, S.; De Risi, A.; Mazzer, M.

2003-01-01

Optimising the spectral emissivity of the IR radiation source in a TPV generator is one of the crucial steps towards high efficiency TPV conversion. In this paper we present different approaches to the preparation of selective emitters to be coupled to high efficiency photovoltaic cells. The emitters are designed to work at a temperature of about 1500K and they have been prepared to be used either as external coatings for the burner or as a structural material for the burner itself. Composite ceramics containing rare earth cations, prepared by slip-casting, with various concentration of rare earths were prepared by Slip Casting and Slurry Coating. Rare earth oxides have been incorporated into different oxide matrices, namely Silica, Alumina, Zirconia and their combination. The final aim was to find the material that exhibits the best performance in terms of both high selective power emission, good efficiency along with acceptable thermo-structural properties (high temperature thermal shock resistance, good strength, no creep). The power density emitted by samples as function of the temperature has been tested in the range 1000nm-5000nm. The high temperature emission measurements and the structural tests indicate that a good compromise between the functional and the thermo-structural properties may be reached. The results of the tests on the emitter coatings carried out in a TPV generator at the operating conditions are also presented in this paper.

Development of a New Ferrous Aluminosilicate Refractory Material for Investment Casting of Aluminum Alloys

NASA Astrophysics Data System (ADS)

Yuan, Chen; Jones, Sam; Blackburn, Stuart

2012-12-01

Investment casting is a time-consuming, labour intensive process, which produces complex, high value-added components for a variety of specialised industries. Current environmental and economic pressures have resulted in a need for the industry to improve current casting quality, reduce manufacturing costs and explore new markets for the process. Alumino-silicate based refractories are commonly used as both filler and stucco materials for ceramic shell production. A new ceramic material, norite, is now being produced based on ferrous aluminosilicate chemistry, having many potential advantages when used for the production of shell molds for casting aluminum alloy. This paper details the results of a direct comparison made between the properties of a ceramic shell system produced with norite refractories and a typical standard refractory shell system commonly used in casting industry. A range of mechanical and physical properties of the systems was measured, and a full-scale industrial casting trial was also carried out. The unique properties of the norite shell system make it a promising alternative for casting aluminum based alloys in the investment foundry.

Numerical simulation of the casting process of titanium tooth crowns and bridges.

PubMed

Wu, M; Augthun, M; Wagner, I; Sahm, P R; Spiekermann, H

2001-06-01

The objectives of this paper were to simulate the casting process of titanium tooth crowns and bridges; to predict and control porosity defect. A casting simulation software, MAGMASOFT, was used. The geometry of the crowns with fine details of the occlusal surface were digitized by means of laser measuring technique, then converted and read in the simulation software. Both mold filling and solidification were simulated, the shrinkage porosity was predicted by a "feeding criterion", and the gas pore sensitivity was studied based on the mold filling and solidification simulations. Two types of dental prostheses (a single-crown casting and a three-unit-bridge) with various sprue designs were numerically "poured", and only one optimal design for each prosthesis was recommended for real casting trial. With the numerically optimized design, real titanium dental prostheses (five replicas for each) were made on a centrifugal casting machine. All the castings endured radiographic examination, and no porosity was detected in the cast prostheses. It indicates that the numerical simulation is an efficient tool for dental casting design and porosity control. Copyright 2001 Kluwer Academic Publishers

AIS/DOE Technology Roadmap Program: Strip Casting: Anticipating New Routes To Steel Sheet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prof. Alan W. Camb; Prof. Anthony Rollett

2001-08-31

To determine the potential for strip casting in the steel industry and to develop the fundamental knowledge necessary to allow the role of strip casting in the modern steel industry to be understood. Based upon a study of carbon steel strip castings that were either produced for the program at British Steel or were received from a pre-commercial production machine, the following conclusions were made. Strip casting of carbon steels is technically feasible for sheet material from slightly less than 1 mm thick to 3 mm thick, and, assuming that it is economically viable, it will be first applied inmore » carbon steel markets that do not require stringent surface quality or extensive forming. The potential of strip casting as a casting process to be developed for steel castings is very high as the cast strip has some very novel characteristics. Direct cast carbon strip has better surface quality, shape and profile than any other casting process currently available. The more rapidly solidified structure of direct cast strip tends to be strong with low ductility; however, with adequate thermal treatment, it is possible to develop a variety of properties from the same grade. The process is more amenable at this time to production tonnages per year of the order of 500,000 tons and as such will first find niche type applications. This technology is an additional technology for steel production and will be in addition to, rather than a replacement for, current casting machines.« less

Novel technologies for the lost foam casting process

NASA Astrophysics Data System (ADS)

Jiang, Wenming; Fan, Zitian

2018-03-01

Lost foam casting (LFC) is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the Al and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting technology; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thinwall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the Al/Mg and Al/Al bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.

Development of a New Membrane Casting Apparatus for Studying Macrovoid Defects in Low-G

NASA Technical Reports Server (NTRS)

Lee, Hanyong; Hwang, Sun-Tak; Krantz, William B.; Greenberg, Alan R.; Khare, Vivek; Zartman, Jeremiah; Todd, Paul W.

2002-01-01

A new membrane-casting apparatus is developed for studying macrovoid defects in polymeric membranes made by the wet- and dry-casting process in low-gravity. Macrovoids are large (10-50 micron), open cavities interspersed among the smaller pores in the substructure under the gelled skin surface layer of the cast membrane. Although their occurrence is considered endemic to the wet- and dry-casting process since they can lead to compaction or skin rupture in the membrane process, recent studies suggest several useful applications such as transdermal and osmotic drug delivery systems, miniature bioreactors, etc. However, lack of knowledge about the macrovoid formation mechanism is an obstacle to further development of applications using them. An on-going debate is the role of the surface-tension-driven solutocapillary convection during macrovoid formation. The rapid growth of macrovoids within 1-5 seconds and the high polymer concentration in and near macrovoids make it difficult to explain the mechanism of macrovoid growth by diffusion alone, which is the widely accepted hypothesis proposed by Reuvers et al. The hypothesis advanced by our research group can explain this rapid growth via a mechanism that involves diffusion from the casting solution in the meta-stable region to the macrovoid enhanced by solutocapillary convection induced by the steep nonsolvent concentration gradient in the vicinity of the macrovoid. Since macrovoid growth is hypothesized to be the interplay of a solutocapillary-induced driving force counteracted by viscous drag and buoyancy, eliminate the latter provides a means for testing this hypothesis. Moreover, free convection mass transfer in the nonsolvent immersion bath used to cause phase-separation in membrane casting complicates developing a model for both the wet-casting process and macrovoid growth. The low-g environment minimizes gravitationally induced free convection thereby permitting a tractable solution to the ternary diffusion equations that characterize membrane formation. NASA's Parabolic Flight Research Aircraft provides a small window of low-g (approximately 25 s) that can be used to study macrovoid development in both wet- and dry-cast membranes if an appropriate casting apparatus is used. This casting apparatus should be able to cast the membrane in both low- and high-g in a manner so that essential one-dimensional mass transfer conditions are achieved to insure lateral uniformity in the membrane. The apparatus used in previous research on membrane casting in low-gravity was operated with the plunger driven mechanism. The spring-loaded plunger pushes the bottom block containing the polymer casting solution well directly under the absorbent chamber located in the upper stationary block. However, membranes made via this casting apparatus often displayed lateral nonuniformities that precluded obtaining quantitative information on the macrovoid growth process. Thus, it was necessary to determine the reason for these structural irregularities observed in the low-g casting apparatus. Both experimental as well as computer simulation studies of the low-g casting apparatus established that the impulsive action of the plunger caused the undesired structural nonuniformities. The simulation results showed that the width-to-depth aspect ratio of the shallow well that contains the casting solution in this apparatus was not an important factor in minimizing this problem. Even for a 40:1 (width : depth) aspect ratio, any convection induced by the horizontal motion of the interface of the casting solution will be damped out within 6.25x10(exp 4) seconds. However, the experimental studies revealed that the impulsive motion of the plunger caused a 'sloshing' of the casting solution that had to be eliminated. Therefore, the plungerdriven mechanism was changed to a cam-driven mechanism that did not cause any impulsive motion of the casting solution. Other refinements to this new membrane-casting apparatus include provision for removing the membranes from the casting wells in a less destructive manner. This was accomplished by using a slit geometry for the casting well that permitted disassembly for removal of the cast membrane. The materials used in the construction of this casting apparatus were chosen to insure wetting at the side walls and to maintain precise control of the thickness of the polymer solution in the casting well. An additional provision in this new casting apparatus is the ability to carry out both wet- as well as dry-casting. As such, this apparatus permitted the first studies of the wet-casting of polymeric membranes in low-g. Both wet- and dry-casting experiments on NASA's KC-135 research aircraft employing this new membrane-casting apparatus are scheduled in July 2002. The morphology of the resulting membranes will be characterized using an environmental scanning electron microscope (ESEM). The results of these low-g studies will be reported later.

A Recipe for Soft Fluidic Elastomer Robots.

PubMed

Marchese, Andrew D; Katzschmann, Robert K; Rus, Daniela

2015-03-01

This work provides approaches to designing and fabricating soft fluidic elastomer robots. That is, three viable actuator morphologies composed entirely from soft silicone rubber are explored, and these morphologies are differentiated by their internal channel structure, namely, ribbed, cylindrical, and pleated. Additionally, three distinct casting-based fabrication processes are explored: lamination-based casting, retractable-pin-based casting, and lost-wax-based casting. Furthermore, two ways of fabricating a multiple DOF robot are explored: casting the complete robot as a whole and casting single degree of freedom (DOF) segments with subsequent concatenation. We experimentally validate each soft actuator morphology and fabrication process by creating multiple physical soft robot prototypes.

Effect of flask vibration time on casting integrity, Surface Penetration and Coating Inclusion in lost foam casting of Al-Si Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karimian, Majid; Idris, M. H.; Ourdjini, A.

2011-01-17

The paper presents the result of an experimental investigation conducted on medium aluminum silicon alloy casting- LM6, using no-vacuum assisted lost foam casting process. The study is directed for establishing the relationship between the flask vibrations times developed for molded sample on the casting integrity, surface penetration and coating inclusion defects of the casting. Four different flask vibration times namely 180, 120, 90 and 60 sec. were investigated. The casting integrity was investigated in terms of fulfilling in all portions and edges. The surface penetration was measured using optical microscope whilst image analyzer was used to quantify the percentage ofmore » coating inclusion in the casting. The results show that vibration time has significant influence on the fulfilling as well as the internal integrity of the lost foam casting. It was found that the lower vibration time produced comparatively sound casing.« less

An Investigation of the Mold-Flux Performance for the Casting of Cr12MoV Steel Using a Mold Simulator Technique

NASA Astrophysics Data System (ADS)

Zhou, Lejun; Wang, Wanlin; Xu, Chao; Zhang, Chen

2017-08-01

Mold flux plays important roles in the process of continuous casting. In this article, the performance of mold flux for the casting of Cr12MoV steel was investigated by using a mold simulator. The results showed that the slag film formed in the gap between the initial shell and mold hot surface is thin and discontinuous during the casting process with the Flux BM, due to the absorption of chromic oxide inclusions into the liquid slag, while the slag film formed in the case of the optimized Flux NEW casting process is uniform. The main precipitated crystals in Flux BM slag film are cuspidine (Ca4Si2O7F2) and Cr3O4, but only Ca4Si2O7F2 precipitated in the Flux NEW case. Besides, both the responding temperature and heat flux in the case of Flux BM are relatively higher and fluctuate in a larger amplitude. The surface of the shell obtained in the case of the Flux BM experiment is quite uneven, and many severe depressions, cracks, and entrapped slags are observed in the surface due to the lack of lubrication. However, the obtained shell surface in the case of the Flux NEW shows good surface quality due to the addition of B2O3 and the adjustment of basicity, which can compensate for the negative effects of the mold-flux properties caused by the absorption of chromic oxide during the casting process.

Microstructural Evolution in Intensively Melt Sheared Direct Chill Cast Al-Alloys

NASA Astrophysics Data System (ADS)

Jones, S.; Rao, A. K. Prasada; Patel, J. B.; Scamans, G. M.; Fan, Z.

The work presented here introduces the novel melt conditioned direct chill casting (MC-DC) technology, where intensive melt shearing is applied to the conventional direct-chill casting process. MC-DC casting can successfully produce high quality Al-alloy billets. The results obtained from 80 mm diameter billets cast at speed of 200 mm/min show that MC-DC casting of Al-alloys, substantially refines the microstructure and reduces macro-segregation. In this paper, we present the preliminary results and discuss microstructural evolution during MC-DC casting of Al-alloys.

A comparison of forming technologies for ceramic gas-turbine engine components

NASA Technical Reports Server (NTRS)

Hengst, R. R.; Heichel, D. N.; Holowczak, J. E.; Taglialavore, A. P.; Mcentire, B. J.

1990-01-01

For over ten years, injection molding and slip casting have been actively developed as forming techniques for ceramic gas turbine components. Co-development of these two processes has continued within the U.S. DOE-sponsored Advanced Turbine Technology Application Project (ATTAP). Progress within ATTAP with respect to these two techniques is summarized. A critique and comparison of the two processes are given. Critical aspects of both processes with respect to size, dimensional control, material properties, quality, cost, and potential for manufacturing scale-up are discussed.

Biomimetic Structural Materials: Inspiration from Design and Assembly

NASA Astrophysics Data System (ADS)

Yaraghi, Nicholas A.; Kisailus, David

2018-04-01

Nature assembles weak organic and inorganic constituents into sophisticated hierarchical structures, forming structural composites that demonstrate impressive combinations of strength and toughness. Two such composites are the nacre structure forming the inner layer of many mollusk shells, whose brick-and-mortar architecture has been the gold standard for biomimetic composites, and the cuticle forming the arthropod exoskeleton, whose helicoidal fiber-reinforced architecture has only recently attracted interest for structural biomimetics. In this review, we detail recent biomimetic efforts for the fabrication of strong and tough composite materials possessing the brick-and-mortar and helicoidal architectures. Techniques discussed for the fabrication of nacre- and cuticle-mimetic structures include freeze casting, layer-by-layer deposition, spray deposition, magnetically assisted slip casting, fiber-reinforced composite processing, additive manufacturing, and cholesteric self-assembly. Advantages and limitations to these processes are discussed, as well as the future outlook on the biomimetic landscape for structural composite materials.

Biomimetic Structural Materials: Inspiration from Design and Assembly.

PubMed

Yaraghi, Nicholas A; Kisailus, David

2018-04-20

Nature assembles weak organic and inorganic constituents into sophisticated hierarchical structures, forming structural composites that demonstrate impressive combinations of strength and toughness. Two such composites are the nacre structure forming the inner layer of many mollusk shells, whose brick-and-mortar architecture has been the gold standard for biomimetic composites, and the cuticle forming the arthropod exoskeleton, whose helicoidal fiber-reinforced architecture has only recently attracted interest for structural biomimetics. In this review, we detail recent biomimetic efforts for the fabrication of strong and tough composite materials possessing the brick-and-mortar and helicoidal architectures. Techniques discussed for the fabrication of nacre- and cuticle-mimetic structures include freeze casting, layer-by-layer deposition, spray deposition, magnetically assisted slip casting, fiber-reinforced composite processing, additive manufacturing, and cholesteric self-assembly. Advantages and limitations to these processes are discussed, as well as the future outlook on the biomimetic landscape for structural composite materials.

Remelt Ingot Production Technology

NASA Astrophysics Data System (ADS)

Grandfield, J. F.

The technology related to the production of remelt ingots (small ingots, sows and T-Bar) is reviewed. Open mold conveyors, sow casting, wheel and belt casting and VDC and HDC casting are described and compared. Process economics, capacity, product quality and process problems are listed. Trends in casting machine technology such as longer open mold conveyor lines are highlighted. Safety issues related to the operation of these processes are discussed. The advantages and disadvantages of the various machine configurations and options e.g. such as dry filling with the mold out of water and wet filling with the mold in water for open mould conveyors are discussed. The effect of mold design on machine productivity, mold cracking and mold life is also examined.

Effects of Process Parameters on Solidification Structure of A390 Aluminum Alloy Hollow Billet

NASA Astrophysics Data System (ADS)

Zuo, Kesheng; Zhang, Haitao; Qin, Ke; Cui, Jianzhong; Chen, Qingzhang

2017-08-01

The effects of process parameters on the solidification structure of A390 aluminum alloy hollow billets prepared by direct-chill casting were investigated. The decrease of casting temperature deteriorated the homogeneity and increased the size of primary Si particles in the hollow billet. Although the average size of primary Si particles was not obviously affected by the increase of casting speed, the thickness of Si-depleted layer at the inner wall increased with the higher casting speed. The tensile strength of A390 alloy is a function of the percentage of coarse Si particles (larger than 35 μm) and the average size of primary Si particles. Higher and more stable tensile strength can be received in the hollow billet with the casting temperature of 1050 K (777 °C), because the fine and uniformly distributed primary Si particles were obtained in the hollow billet.

Fuzzy control strategy for secondary cooling of continuous steel casting

NASA Astrophysics Data System (ADS)

Tirian, G. O.; Gheorghiu, C. A.; Hepuţ, T.; Rob, R.

2017-05-01

The purpose of this paper is to create an original fuzzy solution on the existing structure of the control system of continuous casting that eliminates fissures in the poured material from the secondary cooling of steel. For this purpose a system was conceived with three fuzzy database decision rules, which by analyzing a series of measurements taken from the process produces adjustments in the rate of flow of the cooling water and the speed of casting and determine the degree of risk of the wire. In the specialized literature on the national plan and the world, there is no intelligent correction in the rate of flow of the cooling water and the speed of casting in the secondary cooling of steel. The database of rules was made using information collected directly from the installation process of continuous casting of the Arcelor Mittal Hunedoara.

Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Lost Foam Thin Wall - Feasibility of Producing Lost Foam Castings in Aluminum and Magnesium Based Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fasoyinu, Yemi; Griffin, John A.

2014-03-31

With the increased emphasis on vehicle weight reduction, production of near-net shape components by lost foam casting will make significant inroad into the next-generation of engineering component designs. The lost foam casting process is a cost effective method for producing complex castings using an expandable polystyrene pattern and un-bonded sand. The use of un-bonded molding media in the lost foam process will impose less constraint on the solidifying casting, making hot tearing less prevalent. This is especially true in Al-Mg and Al-Cu alloy systems that are prone to hot tearing when poured in rigid molds partially due to their longmore » freezing range. Some of the unique advantages of using the lost foam casting process are closer dimensional tolerance, higher casting yield, and the elimination of sand cores and binders. Most of the aluminum alloys poured using the lost foam process are based on the Al-Si system. Very limited research work has been performed with Al-Mg and Al-Cu type alloys. With the increased emphasis on vehicle weight reduction, and given the high-strength-to-weight-ratio of magnesium, significant weight savings can be achieved by casting thin-wall (≤ 3 mm) engineering components from both aluminum- and magnesium-base alloys.« less

Modeling on Fluid Flow and Inclusion Motion in Centrifugal Continuous Casting Strands

NASA Astrophysics Data System (ADS)

Wang, Qiangqiang; Zhang, Lifeng; Sridhar, Seetharaman

2016-08-01

During the centrifugal continuous casting process, unreasonable casting parameters can cause violent level fluctuation, serious gas entrainment, and formation of frozen shell pieces at the meniscus. Thus, in the current study, a three-dimensional multiphase turbulent model was established to study the transport phenomena during centrifugal continuous casting process. The effects of nozzle position, casting and rotational speed on the flow pattern, centrifugal force acting on the molten steel, level fluctuation, gas entrainment, shear stress on mold wall, and motion of inclusions during centrifugal continuous casting process were investigated. Volume of Fluid model was used to simulate the molten steel-air two-phase. The level fluctuation and the gas entrainment during casting were calculated by user-developed subroutines. The trajectory of inclusions in the rotating system was calculated using the Lagrangian approach. The results show that during centrifugal continuous casting, a large amount of gas was entrained into the molten steel, and broken into bubbles of various sizes. The greater the distance to the mold wall, the smaller the centrifugal force. Rotation speed had the most important influence on the centrifugal force distribution at the side region. Angular moving angle of the nozzle with 8° and keeping the rotation speed with 60 revolutions per minute can somehow stabilize the level fluctuation. The increase of angular angle of nozzle from 8 to 18 deg and rotation speed from 40 to 80 revolutions per minute favored to decrease the total volume of entrained bubbles, while the increase of distance of nozzle moving left and casting speed had reverse effects. The trajectories of inclusions in the mold were irregular, and then rotated along the strand length. After penetrating a certain distance, the inclusions gradually moved to the center of billet and gathered there. More work, such as the heat transfer, the solidification, and the inclusions entrapment during centrifugal continuous casting, will be performed.

Novel Applications of Rapid Prototyping in Gamma-ray and X-ray Imaging

PubMed Central

Miller, Brian W.; Moore, Jared W.; Gehm, Michael E.; Furenlid, Lars R.; Barrett, Harrison H.

2010-01-01

Advances in 3D rapid-prototyping printers, 3D modeling software, and casting techniques allow for the fabrication of cost-effective, custom components in gamma-ray and x-ray imaging systems. Applications extend to new fabrication methods for custom collimators, pinholes, calibration and resolution phantoms, mounting and shielding components, and imaging apertures. Details of the fabrication process for these components are presented, specifically the 3D printing process, cold casting with a tungsten epoxy, and lost-wax casting in platinum. PMID:22984341

Spontaneous Imbibition Process in Micro-Nano Fractal Capillaries Considering Slip Flow

NASA Astrophysics Data System (ADS)

Shen, Yinghao; Li, Caoxiong; Ge, Hongkui; Guo, Xuejing; Wang, Shaojun

An imbibition process of water into a matrix is required to investigate the influences of large-volume fracturing fluids on gas production of unconventional formations. Slip flow has been recognized by recent studies as a major mechanism of fluid transport in nanotubes. For nanopores in shale, a slip boundary is nonnegligible in the imbibition process. In this study, we established an analytic equation of spontaneous imbibition considering slip effects in capillaries. A spontaneous imbibition model that couples the analytic equation considering the slip effect was constructed based on fractal theory. We then used a model for various conditions, such as slip boundary, pore structure, and fractal dimension of pore tortuosity, to capture the imbibition characteristics considering the slip effect. A dynamic contact angle was integrated into the modeling. Results of our study verify that the slip boundary influences water imbibition significantly. The imbibition speed is significantly improved when slip length reaches the equivalent diameter of a tube. Therefore, disregarding the slip effect will underestimate the imbibition speed in shale samples.

A Recipe for Soft Fluidic Elastomer Robots

PubMed Central

Marchese, Andrew D.; Katzschmann, Robert K.

2015-01-01

Abstract This work provides approaches to designing and fabricating soft fluidic elastomer robots. That is, three viable actuator morphologies composed entirely from soft silicone rubber are explored, and these morphologies are differentiated by their internal channel structure, namely, ribbed, cylindrical, and pleated. Additionally, three distinct casting-based fabrication processes are explored: lamination-based casting, retractable-pin-based casting, and lost-wax-based casting. Furthermore, two ways of fabricating a multiple DOF robot are explored: casting the complete robot as a whole and casting single degree of freedom (DOF) segments with subsequent concatenation. We experimentally validate each soft actuator morphology and fabrication process by creating multiple physical soft robot prototypes. PMID:27625913

Ultrasonic Substrate Vibration-Assisted Drop Casting (SVADC) for the Fabrication of Photovoltaic Solar Cell Arrays and Thin-Film Devices.

PubMed

Eslamian, Morteza; Zabihi, Fatemeh

2015-12-01

A simple, low-cost, versatile, and potentially scalable casting method is proposed for the fabrication of micro- and nano-thin films, herein termed as ultrasonic "substrate vibration-assisted drop casting" (SVADC). The impingement of a solution drop onto a substrate in a simple process called drop casting, usually results in spreading of the liquid solution and the formation of a non-uniform thin solid film after solvent evaporation. Our previous and current supporting results, as well as few similar reports by others, confirm that imposing ultrasonic vibration on the substrate can simply convert the uncontrollable drop casting method into a controllable coating technique. Therefore, the SVADC may be used to fabricate an array of emerging thin-film solar cells, such as polymer, perovskite, and quantum-dot solar cells, as well as other small thin-film devices, in a roll-to-roll and automated fabrication process. The preliminary results demonstrate a ten-fold increase in electrical conductivity of PSS made by SVADC compared with the film made by conventional drop casting. Also, simple planar perovskite solar cells made here using SVADC show promising performance with an efficiency of over 3 % for a simple structure without performing process optimization or using expensive materials and treatments.

AMCC casting development, volume 2

NASA Technical Reports Server (NTRS)

1995-01-01

PCC successfully cast and performed nondestructive testing, FPI and x-ray, on seventeen AMCC castings. Destructive testing, lab analysis and chemical milling, was performed on eleven of the castings and the remaining six castings were shipped to NASA or Aerojet. Two of the six castings shipped, lots 015 and 016, were fully processed per blueprint requirements. PCC has fully developed the gating and processing parameters of this part and feels the part could be implemented into production, after four more castings have been completed to ensure the repeatability of the process. The AMCC casting has been a technically challenging part due to its size, configuration, and alloy type. The height and weight of the wax pattern assembly necessitated the development of a hollow gating system to ensure structural integrity of the shell throughout the investment process. The complexity in the jacket area of the casting required the development of an innovative casting technology that PCC has termed 'TGC' or thermal gradient control. This method of setting up thermal gradients in the casting during solidification represents a significant process improvement for PCC and has been successfully implemented on other programs. The alloy, JBK75, is a relatively new alloy in the investment casting arena and required our engineering staff to learn the gating, processing, and dimensional characteristics of the material.

Control system of water flow and casting speed in continuous steel casting

NASA Astrophysics Data System (ADS)

Tirian, G. O.; Gheorghiu, C. A.; Hepuţ, T.; Chioncel, C.

2017-05-01

This paper presents the results of research based on real data taken from the installation process at Arcelor Mittal Hunedoara. Using Matlab Simulink an intelligent system is made that takes in data from the process and makes real time adjustments in the rate of flow of the cooling water and the speed of casting that eliminates fissures in the poured material from the secondary cooling of steel. Using Matlab Simulink simulation environment allowed for qualitative analysis for various real world situations. Thus, compared to the old method of approach for the problem of cracks forming in the crust of the steel in the continuous casting, this new method, proposed and developed, brings safety and precision in this complex process, thus removing any doubt on the existence or non-existence of cracks and takes the necessary steps to prevent and correct them.

Prediction model of austenite growth and the role of MnS inclusions in non-quenched and tempered steel

NASA Astrophysics Data System (ADS)

Jiang, Bo; Wu, Meng; Sun, He; Wang, Zhilin; Zhao, Zhigang; Liu, Yazheng

2018-01-01

The austenite growth behavior of non-quenched and tempered steels (casted by continuous casting and molding casting processes) was studied. The austenite grain size of steel B casted by continuous casting process is smaller than that of steel A casted by molding casting process at the same heating parameters. The abnormal austenite growth temperature of the steels A and B are 950 °C and 1000 °C, respectively. Based on the results, the models for the austenite grain growth below and above the abnormal austenite growth temperature of the investigated steels were established. The dispersedly distributed fine particles MnS in steel B is the key factor refining the austenite grain by pinning the migration of austenite grain boundary. The elongated inclusions MnS are ineffective in preventing the austenite grain growth at high heating temperature. For the non-quenched and tempered steel, the continuous casting process should be adopted and the inclusion MnS should be elliptical, smaller in size and distributed uniformly in order to refine the final microstructure and also improve the mechanical properties.

Enhancement of Efficiency and Reduction of Grid Thickness Variation on Casting Process with Lean Six Sigma Method

NASA Astrophysics Data System (ADS)

Witantyo; Setyawan, David

2018-03-01

In a lead acid battery industry, grid casting is a process that has high defect and thickness variation level. DMAIC (Define-Measure-Analyse-Improve-Control) method and its tools will be used to improve the casting process. In the Define stage, it is used project charter and SIPOC (Supplier Input Process Output Customer) method to map the existent problem. In the Measure stage, it is conducted a data retrieval related to the types of defect and the amount of it, also the grid thickness variation that happened. And then the retrieved data is processed and analyzed by using 5 Why’s and FMEA method. In the Analyze stage, it is conducted a grid observation that experience fragile and crack type of defect by using microscope showing the amount of oxide Pb inclusion in the grid. Analysis that is used in grid casting process shows the difference of temperature that is too high between the metal fluid and mold temperature, also the corking process that doesn’t have standard. The Improve stage is conducted a fixing process which generates the reduction of grid variation thickness level and defect/unit level from 9,184% to 0,492%. In Control stage, it is conducted a new working standard determination and already fixed control process.

A Statistics-Based Cracking Criterion of Resin-Bonded Silica Sand for Casting Process Simulation

NASA Astrophysics Data System (ADS)

Wang, Huimin; Lu, Yan; Ripplinger, Keith; Detwiler, Duane; Luo, Alan A.

2017-02-01

Cracking of sand molds/cores can result in many casting defects such as veining. A robust cracking criterion is needed in casting process simulation for predicting/controlling such defects. A cracking probability map, relating to fracture stress and effective volume, was proposed for resin-bonded silica sand based on Weibull statistics. Three-point bending test results of sand samples were used to generate the cracking map and set up a safety line for cracking criterion. Tensile test results confirmed the accuracy of the safety line for cracking prediction. A laboratory casting experiment was designed and carried out to predict cracking of a cup mold during aluminum casting. The stress-strain behavior and the effective volume of the cup molds were calculated using a finite element analysis code ProCAST®. Furthermore, an energy dispersive spectroscopy fractographic examination of the sand samples confirmed the binder cracking in resin-bonded silica sand.

An Investigation into the Effects of Sprue Attachment Design on Porosity and Castability

DTIC Science & Technology

1990-12-01

of a dental alloy: sprue design, mold temperature, fusing and casting temperature of the alloy, type of casting machine, casting force, burnout time... Student at: University of Texas, San Antonio AFIT/CI/CIA-90-119 AFIT/CI Wright-Patterson AFB OH 45433-6583 Approved for Public Release IAW AFR 190-1...Supervising Professor: E. Steven Duke, D.D.S., M.S.D. Many variables are involved in the process of fabricating a dense dental casting which accurately

Vacuum casting of thick polymeric films

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Moacanin, J.

1979-01-01

Bubble formation and layering, which often plague vacuum-evaporated films, are prevented by properly regulating process parameters. Vacuum casting may be applicable to forming thick films of other polymer/solvent solutions.

Method and apparatus for planar drag strip casting

DOEpatents

Powell, John C.; Campbell, Steven L.

1991-01-01

The present invention is directed to an improved process and apparatus for strip casting. The combination of a planar flow casting nozzle positioned back from the top dead center position with an attached nozzle extension, provides an increased level of casting control and quality. The nozzle extension provides a means of containing the molten pool above the rotating substrate to increase the control of molten metal at the edges of the strip and increase the range of coating thicknesses which may be produced. The level of molten metal in the containment means is regulated to be above the level of melt supplying the casting nozzle which produces a condition of planar drag flow with the casting substrate prior to solidification.

3D printing in X-ray and Gamma-Ray Imaging: A novel method for fabricating high-density imaging apertures☆

PubMed Central

Miller, Brian W.; Moore, Jared W.; Barrett, Harrison H.; Fryé, Teresa; Adler, Steven; Sery, Joe; Furenlid, Lars R.

2011-01-01

Advances in 3D rapid-prototyping printers, 3D modeling software, and casting techniques allow for cost-effective fabrication of custom components in gamma-ray and X-ray imaging systems. Applications extend to new fabrication methods for custom collimators, pinholes, calibration and resolution phantoms, mounting and shielding components, and imaging apertures. Details of the fabrication process for these components, specifically the 3D printing process, cold casting with a tungsten epoxy, and lost-wax casting in platinum are presented. PMID:22199414

Strain Rate Dependency of Bronze Metal Matrix Composite Mechanical Properties as a Function of Casting Technique

NASA Astrophysics Data System (ADS)

Brown, Lloyd; Joyce, Peter; Radice, Joshua; Gregorian, Dro; Gobble, Michael

2012-07-01

Strain rate dependency of mechanical properties of tungsten carbide (WC)-filled bronze castings fabricated by centrifugal and sedimentation-casting techniques are examined, in this study. Both casting techniques are an attempt to produce a functionally graded material with high wear resistance at a chosen surface. Potential applications of such materials include shaft bushings, electrical contact surfaces, and brake rotors. Knowledge of strain rate-dependent mechanical properties is recommended for predicting component response due to dynamic loading or impact events. A brief overview of the casting techniques for the materials considered in this study is followed by an explanation of the test matrix and testing techniques. Hardness testing, density measurement, and determination of the volume fraction of WC particles are performed throughout the castings using both image analysis and optical microscopy. The effects of particle filling on mechanical properties are first evaluated through a microhardness survey of the castings. The volume fraction of WC particles is validated using a thorough density survey and a rule-of-mixtures model. Split Hopkinson Pressure Bar (SHPB) testing of various volume fraction specimens is conducted to determine strain dependence of mechanical properties and to compare the process-property relationships between the two casting techniques. The baseline performances of C95400 bronze are provided for comparison. The results show that the addition of WC particles improves microhardness significantly for the centrifugally cast specimens, and, to a lesser extent, in the sedimentation-cast specimens, largely because the WC particles are more concentrated as a result of the centrifugal-casting process. Both metal matrix composites (MMCs) demonstrate strain rate dependency, with sedimentation casting having a greater, but variable, effects on material response. This difference is attributed to legacy effects from the casting process, namely, porosity and localized WC particle grouping.

Gas turbine blade with intra-span snubber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merrill, Gary B.; Mayer, Clinton

2014-07-29

A gas turbine blade (10) including a hollow mid-span snubber (16). The snubber is affixed to the airfoil portion (14) of the blade by a fastener (20) passing through an opening (24) cast into the surface (22) of the blade. The opening is defined during an investment casting process by a ceramic pedestal (38) which is positioned between a ceramic core (32) and a surrounding ceramic casting shell (48). The pedestal provides mechanical support for the ceramic core during both wax and molten metal injection steps of the investment casting process.

Fixture for forming evaporative pattern (EPC) process patterns

DOEpatents

Turner, Paul C.; Jordan, Ronald R.; Hansen, Jeffrey S.

1993-01-01

A method of casting metal using evaporative pattern casting process patterns in combination with a fixture for creating and maintaining a desired configuration in flexible patterns. A pattern is constructed and gently bent to the curvature of a suitable fixture. String or thin wire, which burns off during casting, is used to tie the pattern to the fixture. The fixture with pattern is dipped in a commercially available refractory wash to prevent metal adherence and sticking to the fixture. When the refractory wash is dry, the fixture and pattern are placed in a flask, and sand is added and compacted by vibration. The pattern remains in position, restrained by the fixture. Metal that is poured directly into the pattern replaces the pattern exactly but does not contact or weld to the fixture due to the protective refractory layer. When solid, the casting is easily separated from the fixture. The fixture can be cleaned for reuse in conventional casting cleaning equipment.

Production of permeable cellulose triacetate membranes

DOEpatents

Johnson, Bruce M.

1986-01-01

A phase inversion process for the preparation of cellulose triacetate (CTA) and regenerated cellulose membranes is disclosed. Such membranes are useful as supports for liquid membranes in facilitated transport processes, as microfiltration membranes, as dialysis or ultrafiltration membranes, and for the preparation of ion-selective electrodes. The process comprises the steps of preparing a casting solution of CTA in a solvent comprising a mixture of cyclohexanone and methylene chloride, casting a film from the casting solution, and immersing the cast film in a methanol bath. The resulting CTA membrane may then be hydrolyzed to regenerated cellulose using conventional techniques.

Casting for infantile scoliosis: the pitfall of increased peak inspiratory pressure.

PubMed

Dhawale, Arjun A; Shah, Suken A; Reichard, Samantha; Holmes, Laurens; Brislin, Robert; Rogers, Kenneth; Mackenzie, William G

2013-01-01

Serial cast correction is a popular treatment option for progressive infantile scoliosis. Body casting can lead to chest and abdominal expansion restriction and result in decreased chest wall compliance. There are no studies evaluating the effects of casting on ventilation in infantile scoliosis. This study examines changes in peak inspiratory pressure (PIP) during serial casting for infantile scoliosis. We retrospectively reviewed data obtained from 37 serial Cotrel elongation, derotation, and flexion cast corrections in patients with infantile scoliosis. Patient demographics, radiographic measurements, and anesthesia data were recorded. Anesthesia technique was standardized: children were intubated with rigid endotracheal tubes (ETTs); tidal volume was held constant at 8 to 10 cm(3)/kg using volume control ventilation; and PIP was recorded at baseline, after cast application before window cutout, and after window cutout before extubation. Any complications were documented. We assessed the PIP changes with a repeated measures analysis of variance (ANOVA). The mean age at first casting was 21.8 months (range, 12 to 42 mo) and mean follow-up since first casting was 22.4 months (range, 13 to 40 mo) with mean major Cobb angle of 53±15 degrees. The mean PIP was 15.5±4.9 cm H(2)O before casting, 31.9±7.9 cm H(2)O after cast application, and 20.4±5.6 cm H2O after making windows. There was a 106% increase after casting and 32% increase after window cutout from the baseline PIP levels. There was a significant difference in PIP on repeated measures ANOVA (P<0.0001). Intraoperatively, there was difficulty in maintaining ventilation during 2 procedures and 1 hypotensive episode. One patient developed hypoxemia after casting and another had delayed difficulty in breathing. Casting resulted in an increased PIP due to transient restrictive pulmonary process; after windows were cut out, the PIP reduced but not to baseline. In patients with underlying pulmonary disease, the casting process may induce respiratory complications, and a proper period of observation after casting is necessary. Case series, level 4.

Effect of surface modifications on the bond strength of zirconia ceramic with resin cement resin.

PubMed

Hallmann, Lubica; Ulmer, Peter; Lehmann, Frank; Wille, Sebastian; Polonskyi, Oleksander; Johannes, Martina; Köbel, Stefan; Trottenberg, Thomas; Bornholdt, Sven; Haase, Fabian; Kersten, Holger; Kern, Matthias

2016-05-01

Purpose of this in vitro study was to evaluate the effect of surface modifications on the tensile bond strength between zirconia ceramic and resin. Zirconia ceramic surfaces were treated with 150-μm abrasive alumina particles, 150-μm abrasive zirconia particles, argon-ion bombardment, gas plasma, and piranha solution (H2SO4:H2O2=3:1). In addition, slip casting surfaces were examined. Untreated surfaces were used as the control group. Tensile bond strengths (TBS) were measured after water storage for 3 days or 150 days with additional 37,500 thermal cycling for artificial aging. Statistical analyses were performed with 1-way and 3-way ANOVA, followed by comparison of means with the Tukey HSD test. After storage in distilled water for three days at 37 °C, the highest mean tensile bond strengths (TBS) were observed for zirconia ceramic surfaces abraded with 150-μm abrasive alumina particles (TBS(AAP)=37.3 MPa, TBS(CAAP)=40.4 MPa), and 150-μm abrasive zirconia particles (TBS(AZP)=34.8 MPa, TBS(CAZP)=35.8 MPa). Also a high TBS was observed for specimens treated with argon-ion bombardment (TBS(BAI)=37.8 MPa). After 150 days of storage, specimens abraded with 150-μm abrasive alumina particles and 150-μm abrasive zirconia particles revealed high TBS (TBS(AAP)=37.6 MPa, TBS(CAAP)=33.0 MPa, TBS(AZP)=22.1 MPa and TBS(CAZP)=22.8 MPa). A high TBS was observed also for specimens prepared with slip casting (TBS(SC)=30.0 MPa). A decrease of TBS was observed for control specimens (TBS(UNT)=12.5 MPa, TBS(CUNT)=9.0 MPa), specimens treated with argon-ion bombardment (TBS(BAI)=10.3 MPa) and gas plasma (TBS(GP)=11.0 MPa). A decrease of TBS was observed also for specimens treated with piranha solution (TBS(PS)=3.9 MPa, TBS(CPS)=4.1 MPa). A significant difference in TBS after three days storage was observed for specimens treated with different methods (p<0.001). Thermal cycling significantly reduced TBS for all groups (p<0.001) excluding groups: AAP(p>0.05), CAAP(p>0.05) and SC(p>0.05). However, the failure patterns of debonded specimens prepared with 150-μm abrasive zirconia particles were 96.7% cohesive. Treatment of zirconia ceramic surfaces with abrasive zirconia particles is a promising method to increase the tensile bond strength without significant damage of the ceramic surface itself. An alternative promising method is slip casting. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Method and apparatus for planar drag strip casting

DOEpatents

Powell, J.C.; Campbell, S.L.

1991-11-12

The present invention is directed to an improved process and apparatus for strip casting. The combination of a planar flow casting nozzle positioned back from the top dead center position with an attached nozzle extension, provides an increased level of casting control and quality. The nozzle extension provides a means of containing the molten pool above the rotating substrate to increase the control of molten metal at the edges of the strip and increase the range of coating thicknesses which may be produced. The level of molten metal in the containment means is regulated to be above the level of melt supplying the casting nozzle which produces a condition of planar drag flow with the casting substrate prior to solidification. 5 figures.

Workplace Basic Skills in the Metal Casting Industry for World Class Process and Technology.

ERIC Educational Resources Information Center

Rasmussen, Bonnie

A workplace basic skills project for the metal casting industry was established jointly by Central Alabama Community College and Robinson Foundry, Inc. Evaluation of the project was made through a commercial test of hourly workers' general literacy level gains, instructor-developed pre- and posttests of mastery of the industrial process and…

Aluminum-fly ash metal matrix composites for automotive parts. [Reports for October 1 to December 1998, and January 31 to March 31, 1999

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weiss, David; Purgert, Robert; Rhudy, Richard

1999-04-21

Some highlights are: (1) Material development, process development, and part validation are occurring simultaneously on a fast track schedule. (2) Prior project activity has resulted in a program emphasis on three components--manifolds, mounting brackets, and motor mounts; and three casting techniques--squeeze casting, pressure die casting, and sand casting. (3) With the project focus, it appears possible to offer manifolds and mounting brackets for automotive qualification testing on a schedule in line with the PNGV Year 2004 goal. (4) Through an iterative process of fly ash treatment, MMC ingot preparation, foundry process refinement, and parts production, both foundries (Eck Industries andmore » Thompson Aluminum Casting Company) are addressing the pre-competitive issues of: (a) Optimum castability with fly ash shapes and sizes; (b) Best mechanical properties derived from fly ash shapes and sizes; (c) Effective fly ash classification processes; (d) Mechanical properties resulting from various casting processes and fly ash formulations. Eck and TAC continued experiments with batch ingot provided by both Eck and the University of Wisconsin at Milwaukee. Castings were run that contained varying amounts of fly ash and different size fractions. Components were cast using cenosphere material to ascertain the effects of squeeze casting and to determine whether the pressure would break the cenospheres. Test parts are currently being machined into substandard test bars for mechanical testing. Also, the affect of heat treatments on ashalloy are being studied through comparison to two lots, one heat treated and one in the ''as cast'' condition.« less

Effects of Casting Conditions on End Product Defects in Direct Chill Casted Hot Rolling Ingots

NASA Astrophysics Data System (ADS)

Yorulmaz, Arda; Yüksel, Çağlar; Erzi, Eraz; Dispinar, Derya

Direct chill casting is a reliable casting process for almost any wrought aluminum alloy for subsequent deformation via hot rolling to supply vital industries such as aerospace, automotive, construction, packaging and maritime. While some defects occur during casting, like hot tearing, some others like surface defect causing blisters, appear after hot rolling process or annealing after final cold rolling steps. It was found that some of these defects are caused by melt impurities formed from entrained folded aluminum oxides or bifilms. A study in a hot rolling casting facility was carried out with different melt cleaning practices, launder and molten metal transferring designs. Bifilm index and reduced pressure test were used for determining melt cleanliness measurement. It was found that porous plug gas diffusons for degassing are more effective than lance type degassers and a design towards less turbulent molten metal flow from furnace to mould cavity are necessary for reducing defects caused by bifilms.

Production of permeable cellulose triacetate membranes

DOEpatents

Johnson, B.M.

1986-12-23

A phase inversion process for the preparation of cellulose triacetate (CTA) and regenerated cellulose membranes is disclosed. Such membranes are useful as supports for liquid membranes in facilitated transport processes, as microfiltration membranes, as dialysis or ultrafiltration membranes, and for the preparation of ion-selective electrodes. The process comprises the steps of preparing a casting solution of CTA in a solvent comprising a mixture of cyclohexanone and methylene chloride, casting a film from the casting solution, and immersing the cast film in a methanol bath. The resulting CTA membrane may then be hydrolyzed to regenerated cellulose using conventional techniques.

Preferential orientation of metal oxide superconducting materials by mechanical means

DOEpatents

Capone, D.W.

1990-11-27

A superconductor comprised of a polycrystalline metal oxide such as YBa[sub 2]Cu[sub 3]O[sub 7[minus]X] (where 0 < X < 0.5) is capable of accommodating very large current densities. By aligning the two-dimensional Cu-O layers which carry the current in the superconducting state in the a- and b-directions, i.e., within the basal plane, a high degree of crystalline axes alignment is provided between adjacent grains permitting the metal oxide material to accommodate high current densities. The orthorhombic crystalline particles have a tendency to lie down on one of the longer sides, i.e., on the a- or b-direction. Aligning the crystals in this orientation is accomplished by mechanical working of the material such as by extrusion, tape casting or slip casting, provided a single crystal powder is used as a starting material, to provide a highly oriented, e.g., approximately 90% of the crystal particles have a common orientation, superconducting matrix capable of supporting large current densities. 3 figs.

Preferential orientation of metal oxide superconducting materials by mechanical means

DOEpatents

Capone, Donald W.

1990-01-01

A superconductor comprised of a polycrystalline metal oxide such as YBa.sub.2 Cu.sub.3 O.sub.7-X (where 0<.times.<0.5) is capable of accommodating very large current densities. By aligning the two-dimensional Cu--O layers which carry the current in the superconducting state in the a- and b-directions, i.e., within the basal plane, a high degree of crystalline axes alignment is provided between adjacent grains permitting the metal oxide material to accommodate high current densities. The orthorhombic crystalline particles have a tendency to lie down on one of the longer sides, i.e., on the a- or b-direction. Aligning the crystals in this orientation is accomplished by mechanical working of the material such as by extrusion, tape casting or slip casting, provided a single crystal powder is used as a starting material, to provide a highly oriented, e.g., approximately 90% of the crystal particles have a common orientation, superconducting matrix capable of supporting large current densities.

40 CFR Table 1 to Subpart Wwww of... - Equations To Calculate Organic HAP Emissions Factors for Specific Open Molding and Centrifugal...

Code of Federal Regulations, 2010 CFR

2010-07-01

... Emissions Factors for Specific Open Molding and Centrifugal Casting Process Streams 1 Table 1 to Subpart... Standards for Hazardous Air Pollutants: Reinforced Plastic Composites Production Pt. 63, Subpt. WWWW, Table... Specific Open Molding and Centrifugal Casting Process Streams ER25AU05.020 ER25AU05.021 [70 FR 50129, Aug...

Transmutation Fuel Fabrication-Fiscal Year 2016

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fielding, Randall Sidney; Grover, Blair Kenneth

ABSTRACT Nearly all of the metallic fuel that has been irradiated and characterized by the Advanced Fuel Campaign, and its earlier predecessors, has been arc cast. Arc casting is a very flexible method of casting lab scale quantities of materials. Although the method offers flexibility, it is an operator dependent process. Small changes in parameter space or alloy composition may affect how the material is cast. This report provides a historical insight in how the casting process has been modified over the history of the advanced fuels campaign as well as the physical parameters of the fuels cast in fiscalmore » year 2016.« less

Experimental investigation on in-situ microwave casting of copper

NASA Astrophysics Data System (ADS)

Raman Mishra, Radha; Sharma, Apurbba Kumar

2018-04-01

The in-situ microwave casting of metallic materials is a recently developed casting process. The process works on the principles of hybrid microwave heating and is accomplished inside the applicator cavity. The process involves – melting of the charge, in-situ pouring and solidification of the melt. The electromagnetic and thermal properties of the charge affects microwave-material interaction and hence melting of the charge. On the other hand, cooling conditions inside the applicator controls solidification process. The present work reports on in-situ casting of copper developed inside a multimode cavity at 2.45 GHz using 1400 W. The molten metal was allowed to get poured in-situ inside a graphite mold and solidification was carried out in the same mold inside the applicator cavity. The interaction of microwave with the charge during exposure was studied and the role of oxide layer during meltingthe copper blocks has been presented. The developed in-situ cast was characterized to access the cast quality. Microstructural study revealed the homogeneous and dense structure of the cast. The X-ray diffraction pattern indicated presence of copper in different orientations with (1 1 1) as the dominant orientation. The average micro indentation hardness of the casts was found 93±20 HV.

Surface Structure Formation in Direct Chill (DC) Casting of Al Alloys

NASA Astrophysics Data System (ADS)

Bayat, Nazlin; Carlberg, Torbjörn

2014-05-01

The aim of this study is to increase the understanding of the surface zone formation during direct chill (DC) casting of aluminum billets produced by the air slip technology. The depth of the shell zone, with compositions deviating from the bulk, is of large importance for the subsequent extrusion productivity and quality of final products. The surface microstructures of 6060 and 6005 aluminum alloys in three different surface appearances—defect free, wavy surface, and spot defects—were studied. The surface microstructures and outer appearance, segregation depth, and phase formation were investigated for the mentioned cases. The results were discussed and explained based on the exudation of liquid metal through the mushy zone and the fact that the exudated liquid is contained within a surface oxide skin. Outward solidification in the surface layer was quantitatively analyzed, and the oxide skin movements explained meniscus line formation. Phases forming at different positions in the segregation zone were analyzed and coupled to a cellular solidification in the exudated layer.

Development of compact slip detection sensor using dielectric elastomer

NASA Astrophysics Data System (ADS)

Choi, Jae-young; Hwang, Do-Yeon; Kim, Baek-chul; Moon, Hyungpil; Choi, Hyouk Ryeol; Koo, Ja Choon

2015-04-01

In this paper, we developed a resistance tactile sensor that can detect a slip on the surface of sensor structure. The presented sensor device has fingerprint-like structures that are similar with the role of the humans finger print. The resistance slip sensor that the novel developed uses acrylo-nitrile butadiene rubber (NBR) as a dielectric substrate and graphene as an electrode material. We can measure the slip as the structure of sensor makes a deformation and it changes the resistance through forming a new conductive route. To manufacture our sensor, we developed a new imprint process. By using this process, we can produce sensor with micro unit structure. To verify effectiveness of the proposed slip detection, experiment using prototype of resistance slip sensor is conducted with an algorithm to detect slip and slip is successfully detected. We will discuss the slip detection properties.

Clean Metal Casting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makhlouf M. Makhlouf; Diran Apelian

The objective of this project is to develop a technology for clean metal processing that is capable of consistently providing a metal cleanliness level that is fit for a given application. The program has five tasks: Development of melt cleanliness assessment technology, development of melt contamination avoidance technology, development of high temperature phase separation technology, establishment of a correlation between the level of melt cleanliness and as cast mechanical properties, and transfer of technology to the industrial sector. Within the context of the first task, WPI has developed a standardized Reduced Pressure Test that has been endorsed by AFS asmore » a recommended practice. In addition, within the context of task1, WPI has developed a melt cleanliness sensor based on the principles of electromagnetic separation. An industrial partner is commercializing the sensor. Within the context of the second task, WPI has developed environmentally friendly fluxes that do not contain fluorine. Within the context of the third task, WPI modeled the process of rotary degassing and verified the model predictions with experimental data. This model may be used to optimize the performance of industrial rotary degassers. Within the context of the fourth task, WPI has correlated the level of melt cleanliness at various foundries, including a sand casting foundry, a permanent mold casting foundry, and a die casting foundry, to the casting process and the resultant mechanical properties. This is useful in tailoring the melt cleansing operations at foundries to the particular casting process and the desired properties of cast components.« less

Numerical simulation of the casting process of titanium removable partial denture frameworks.

PubMed

Wu, Menghuai; Wagner, Ingo; Sahm, Peter R; Augthun, Michael

2002-03-01

The objective of this work was to study the filling incompleteness and porosity defects in titanium removal partial denture frameworks by means of numerical simulation. Two frameworks, one for lower jaw and one for upper jaw, were chosen according to dentists' recommendation to be simulated. Geometry of the frameworks were laser-digitized and converted into a simulation software (MAGMASOFT). Both mold filling and solidification of the castings with different sprue designs (e.g. tree, ball, and runner-bar) were numerically calculated. The shrinkage porosity was quantitatively predicted by a feeding criterion, the potential filling defect and gas pore sensitivity were estimated based on the filling and solidification results. A satisfactory sprue design with process parameters was finally recommended for real casting trials (four replica for each frameworks). All the frameworks were successfully cast. Through X-ray radiographic inspections it was found that all the castings were acceptably sound except for only one case in which gas bubbles were detected in the grasp region of the frame. It is concluded that numerical simulation aids to achieve understanding of the casting process and defect formation in titanium frameworks, hence to minimize the risk of producing defect casting by improving the sprue design and process parameters.

Shrinkage Prediction for the Investment Casting of Stainless Steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabau, Adrian S

2007-01-01

In this study, the alloy shrinkage factors were obtained for the investment casting of 17-4PH stainless steel parts. For the investment casting process, unfilled wax and fused silica with a zircon prime coat were used for patterns and shell molds, respectively. Dimensions of the die tooling, wax pattern, and casting were measured using a Coordinate Measurement Machine in order to obtain the actual tooling allowances. The alloy dimensions were obtained from numerical simulation results of solidification, heat transfer, and deformation phenomena. The numerical simulation results for the shrinkage factors were compared with experimental results.

Single Crystal Casting with Fluidized Carbon Bed Cooling: A Process Innovation for Quality Improvement and Cost Reduction

NASA Astrophysics Data System (ADS)

Hofmeister, M.; Franke, M. M.; Koerner, C.; Singer, R. F.

2017-12-01

Superalloy gas turbine blades are being produced by investment casting and directional solidification. A new process, Fluidized Carbon Bed Cooling (FCBC), has been developed and is now being optimized in a prototype casting unit with 10 kg pouring weight. In early test runs with still rather simple mold cluster geometries, a reduction of the primary dendrite arm spacing of around 40 pct compared to the standard radiation cooling process (HRS) could be demonstrated. The improvement is mainly attributed to higher temperature gradients driving solidification, made possible by a functioning Dynamic Baffle. Compared to earlier development efforts in the literature, contamination of the melt and damage to the equipment are avoided using carbon-based fluidized bed materials and the so-called "counter pressure concept."

Low-cost single-crystal turbine blades, volume 1

NASA Technical Reports Server (NTRS)

Strangman, T. E.; Heath, B.; Fujii, M.

1983-01-01

The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be significantly improved with minor modifications to the process. Single crystal Mar-M 247 and two derivative SC alloys were developed. NASAIR 100 and SC Alloy 3 were fully characterized through mechanical property testing. SC Mar-M 247 shows no significant improvement in strength over directionally solidified (DS) Mar-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. The 1000 hr/238 MPa (20 ksi) stress rupture capability compared to DS Mar-M 247 was improved over 28 C. Firtree testing, holography, and strain gauge rig testing were used to evaluate the effects of the anisotropic characteristics of single crystal materials. In general, the single crystal material behaved similarly to DS Mar-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined.

Process for manufacturing a lithium alloy electrochemical cell

DOEpatents

Bennett, William R.

1992-10-13

A process for manufacturing a lithium alloy, metal sulfide cell tape casts slurried alloy powders in an organic solvent containing a dissolved thermoplastic organic binder onto casting surfaces. The organic solvent is then evaporated to produce a flexible tape removable adhering to the casting surface. The tape is densified to increase its green strength and then peeled from the casting surface. The tape is laminated with a separator containing a lithium salt electrolyte and a metal sulfide electrode to form a green cell. The binder is evaporated from the green cell at a temperature lower than the melting temperature of the lithium salt electrolyte. Lithium alloy, metal sulfide and separator powders may be tape cast.

Progress on high-performance rapid prototype aluminum mirrors

NASA Astrophysics Data System (ADS)

Woodard, Kenneth S.; Myrick, Bruce H.

2017-05-01

Near net shape parts can be produced using some very old processes (investment casting) and the relatively new direct metal laser sintering (DMLS) process. These processes have significant advantages for complex blank lightweighting and costs but are not inherently suited for producing high performance mirrors. The DMLS process can provide extremely complex lightweight structures but the high residual stresses left in the material results in unstable mirror figure retention. Although not to the extreme intricacy of DMLS, investment casting can also provide complex lightweight structures at considerably lower costs than DMLS and even conventional wrought mirror blanks but the less than 100% density for casting (and also DMLS) limits finishing quality. This paper will cover the progress that has been made to make both the DMLS and investment casting processes into viable near net shape blank options for high performance aluminum mirrors. Finish and figure results will be presented to show performance commensurate with existing conventional processes.

Scale Rules for Macrosegregation during Direct-Chill Casting of Aluminum Alloys

NASA Astrophysics Data System (ADS)

Eskin, Dmitry G.; Du, Qiang; Katgerman, Laurens

2008-05-01

An analysis of published experimental and numerical results shows that there is a scaling relationship between the magnitude and direction of centerline segregation in direct-chill (DC) cast billets from aluminum alloys and the process parameters, i.e., billet diameter and casting speed. It seems that there is always a range of these process parameters where the centerline segregation is positive, and there is a threshold when the centerline segregation vanishes. Numerical simulations of macrosegregation during DC casting of a binary Al-Cu alloy were performed at different ratios of casting speed and billet diameter. The macrosegregation model takes into account only two mechanisms of macrosegregation, i.e., thermosolutal convection and shrinkage-induced flow. The results of these computer simulations fit well to the dependence obtained using numerous reference data. The results are discussed in terms of the contribution of different mechanisms of macrosegregation and the shape of the billet sump.

Development of expert systems for modeling of technological process of pressure casting on the basis of artificial intelligence

NASA Astrophysics Data System (ADS)

Gavarieva, K. N.; Simonova, L. A.; Pankratov, D. L.; Gavariev, R. V.

2017-09-01

In article the main component of expert system of process of casting under pressure which consists of algorithms, united in logical models is considered. The characteristics of system showing data on a condition of an object of management are described. A number of logically interconnected steps allowing to increase quality of the received castings is developed

Fabrication process analysis and experimental verification for aluminum bipolar plates in fuel cells by vacuum die-casting

NASA Astrophysics Data System (ADS)

Jin, Chul Kyu; Kang, Chung Gil

2011-10-01

There are various methods for the fabrication of bipolar plates, but these are still limited to machining and stamping processes. High-pressure die casting (HPDC) is an ideal process for the manufacture of bipolar plates This study aims to investigate the formability of bipolar plates for polymer electrolyte membrane fuel cells (PEMFCs) fabricated by vacuum HPDC of an Al-Mg alloy (ALDC6). The cavity of the mold consisted of a thin-walled plate (200 mm × 200 mm × 0.8 mm) with a layer of serpentine channel (50 mm × 50 mm). The location and direction of the channel in the final mold design was determined by computational simulation (MAGMA soft). In addition, simulation results for different conditions of plunger stroke control were compared to those from actual die-casting experiments. Under a vacuum pressure of 35 kPa and for injection speeds of 0.3 and 2.5 m s-1 in the low and high speed regions, respectively, the samples had few casting defects. In addition, the hardness was higher and porosity in microstructure was less than those of the samples made under other injection speed conditions. In case of thin-walled plates, vacuum die casting is beneficial in terms of formability compared to conventional die casting.

A combined arc-melting and tilt-casting furnace for the manufacture of high-purity bulk metallic glass materials.

PubMed

Soinila, E; Pihlajamäki, T; Bossuyt, S; Hänninen, H

2011-07-01

An arc-melting furnace which includes a tilt-casting facility was designed and built, for the purpose of producing bulk metallic glass specimens. Tilt-casting was chosen because reportedly, in combination with high-purity processing, it produces the best fatigue endurance in Zr-based bulk metallic glasses. Incorporating the alloying and casting facilities in a single piece of equipment reduces the amount of laboratory space and capital investment needed. Eliminating the sample transfer step from the production process also saves time and reduces sample contamination. This is important because the glass forming ability in many alloy systems, such as Zr-based glass-forming alloys, deteriorates rapidly with increasing oxygen content of the specimen. The challenge was to create a versatile instrument, in which high purity conditions can be maintained throughout the process, even when melting alloys with high affinity for oxygen. Therefore, the design provides a high-vacuum chamber to be filled with a low-oxygen inert atmosphere, and takes special care to keep the system hermetically sealed throughout the process. In particular, movements of the arc-melting electrode and sample manipulator arm are accommodated by deformable metal bellows, rather than sliding O-ring seals, and the whole furnace is tilted for tilt-casting. This performance of the furnace is demonstrated by alloying and casting Zr(55)Cu(30)Al(10)Ni(5) directly into rods up to ø 10 mm which are verified to be amorphous by x-ray diffraction and differential scanning calorimetry, and to exhibit locally ductile fracture at liquid nitrogen temperature.

Elaboration and characterization of a free standing LiSICON membrane for aqueous lithium-air battery

NASA Astrophysics Data System (ADS)

Puech, Laurent; Cantau, Christophe; Vinatier, Philippe; Toussaint, Gwenaëlle; Stevens, Philippe

2012-09-01

In order to develop a LISICON separator for an aqueous lithium-air battery, a thin membrane was prepared by a tape-casting of a Li1.3Al0.3Ti1.7 (PO4)3-AlPO4 based slip followed by a sintering step. By optimizing the grain sizes, the slip composition and the sintering treatment, the mechanical properties were improved and the membrane was reduced to a thickness of down to 40 μm. As a result, the ionic resistance is relatively low, around 38 Ω for a 55 μm membrane of 1 cm2. One side of the membrane was coated with a lithium oxynitrured phosphorous (LiPON) thin film to prevent lithium metal attack. Lithium metal was electrochemically deposited on the LiPON surface from a saturated aqueous solution of LiOH. However, the ionic resistance of the LiPON film, around 67 Ω for a 1.2 μm film of 1 cm2, still causes an important ohmic loss contribution which limits the power performance of a lithium-air battery.

Metallic Fuel Casting Development and Parameter Optimization Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

R.S. Fielding; J. Crapps; C. Unal

One of the advantages of metallic fuel is the abilility to cast the fuel slugs to near net shape with little additional processing. However, the high aspect ratio of the fuel is not ideal for casting. EBR-II fuel was cast using counter gravity injection casting (CGIC) but, concerns have been raised concerning the feasibility of this process for americium bearing alloys. The Fuel Cycle Research and Development program has begun developing gravity casting techniques suitable for fuel production. Compared to CGIC gravity casting does not require a large heel that then is recycled, does not require application of a vacuummore » during melting, and is conducive to re-usable molds. Development has included fabrication of two separate benchscale, approximately 300 grams, systems. To shorten development time computer simulations have been used to ensure mold and crucible designs are feasible and to identify which fluid properties most affect casting behavior and therefore require more characterization.« less

Metal Matrix Composite LOX Turbopump Housing Via Novel Tool-Less Net-Shape Pressure Infiltration Casting Technology

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Lee, Jonathan; Bhat, Biliyar; Wells, Doug; Gregg, Wayne; Marsh, Matthew; Genge, Gary; Forbes, John; Salvi, Alex; Cornie, James A.;

Fabrication of a Bronze Age Sword using Ancient Techniques

NASA Astrophysics Data System (ADS)

Sapiro, David; Webler, Bryan

2016-12-01

A khopesh was cast and forged for the TMS 2016 Bladesmithing Symposium. The khopesh was the first sword style, originating during the Bronze Age in the Near East. The manufacturing process used in this study closely followed Bronze Age techniques to determine the plausibility of open mold casting coupled with cold work and annealing cycles. Forging and annealing cycles substantially increased blade strength and diminished intergranular δ-phase inclusions. While a functional blade was not completed due to casting defects, the process gives valuable insight into the effort required to fabricate a khopesh during the Bronze Age. Forging and annealing cycles following casting were necessary to produce the mechanical properties desired in a sword.

Implementation of Cyber-Physical Production Systems for Quality Prediction and Operation Control in Metal Casting

PubMed Central

Lee, JuneHyuck; Noh, Sang Do; Kim, Hyun-Jung; Kang, Yong-Shin

2018-01-01

The prediction of internal defects of metal casting immediately after the casting process saves unnecessary time and money by reducing the amount of inputs into the next stage, such as the machining process, and enables flexible scheduling. Cyber-physical production systems (CPPS) perfectly fulfill the aforementioned requirements. This study deals with the implementation of CPPS in a real factory to predict the quality of metal casting and operation control. First, a CPPS architecture framework for quality prediction and operation control in metal-casting production was designed. The framework describes collaboration among internet of things (IoT), artificial intelligence, simulations, manufacturing execution systems, and advanced planning and scheduling systems. Subsequently, the implementation of the CPPS in actual plants is described. Temperature is a major factor that affects casting quality, and thus, temperature sensors and IoT communication devices were attached to casting machines. The well-known NoSQL database, HBase and the high-speed processing/analysis tool, Spark, are used for IoT repository and data pre-processing, respectively. Many machine learning algorithms such as decision tree, random forest, artificial neural network, and support vector machine were used for quality prediction and compared with R software. Finally, the operation of the entire system is demonstrated through a CPPS dashboard. In an era in which most CPPS-related studies are conducted on high-level abstract models, this study describes more specific architectural frameworks, use cases, usable software, and analytical methodologies. In addition, this study verifies the usefulness of CPPS by estimating quantitative effects. This is expected to contribute to the proliferation of CPPS in the industry. PMID:29734699

Preslip and cascade processes initiating laboratory stick slip

USGS Publications Warehouse

McLaskey, Gregory C.; Lockner, David A.

2014-01-01

Recent modeling studies have explored whether earthquakes begin with a large aseismic nucleation process or initiate dynamically from the rapid growth of a smaller instability in a “cascade-up” process. To explore such a case in the laboratory, we study the initiation of dynamic rupture (stick slip) of a smooth saw-cut fault in a 76mm diameter cylindrical granite laboratory sample at 40–120MPa confining pressure. We use a high dynamic range recording system to directly compare the seismic waves radiated during the stick-slip event to those radiated from tiny (M _6) discrete seismic events, commonly known as acoustic emissions (AEs), that occur in the seconds prior to each large stick slip. The seismic moments, focal mechanisms, locations, and timing of the AEs all contribute to our understanding of their mechanics and provide us with information about the stick-slip nucleation process. In a sequence of 10 stick slips, the first few microseconds of the signals recorded from stick-slip instabilities are nearly indistinguishable from those of premonitory AEs. In this sense, it appears that each stick slip begins as an AE event that rapidly (~20 μs) grows about 2 orders of magnitude in linear dimension and ruptures the entire 150mm length of the simulated fault. We also measure accelerating fault slip in the final seconds before stick slip. We estimate that this slip is at least 98% aseismic and that it both weakens the fault and produces AEs that will eventually cascade-up to initiate the larger dynamic rupture.

Metal Matrix Composite LOX Turbopump Housing via Novel Tool-less Net-Shape Pressure Infiltration Casting Technology

NASA Technical Reports Server (NTRS)

Shah, Sandeep; Lee, Jonathan; Bhat, Biliyar; Wells, Doug; Gregg, Wayne; Marsh, Matthew; Genge, Gary; Forbes, John; Salvi, Alex; Cornie, James A.

2003-01-01

Metal matrix composites for propulsion components offer high performance and affordability, resulting in low weight and cost. The following sections in this viewgraph presentation describe the pressure infiltration casting of a metal matrix composite LOX turbopump housing: 1) Baseline Pump Design and Stress Analysis; 2) Tool-less Advanced Pressure Infiltration Casting Process; 3) Preform Splicing and Joining for Large Components such as Pump Housing; 4) Fullscale Pump Housing Redesign.

Application of TRIZ Theory in Patternless Casting Manufacturing Technique

NASA Astrophysics Data System (ADS)

Yang, Weidong; Gan, Dequan; Jiang, Ping; Tian, Yumei

The ultimate goal of Patternless Casting Manufacturing (referred to as PCM) is how to obtain the casts by casting the sand mold directly. In the previous PCM, the resin content of sand mold is much higher than that required by traditional resin sand, so the casts obtained are difficult to be sound and qualified products, which limits the application of this technique greatly. In this paper, the TRIZ algorithm is introduced to the innovation process in PCM systematically.

Combination Of Investment And Centrifugal Casting

NASA Technical Reports Server (NTRS)

Creeger, Gordon A.

1994-01-01

Modifications, including incorporation of centrifugal casting, made in investment-casting process reducing scrap rate. Used to make first- and second-stage high-pressure-fuel-turbopump nozzles, containing vanes with thin trailing edges and other thin sections. Investment mold spun for short time while being filled, and stopped before solidification occurs. Centrifugal force drives molten metal into thin trailing edges, ensuring they are filled. With improved filling, preheat and pour temperatures reduced and solidification hastened so less hot tearing.

The effect of casting conditions on the biaxial flexural strength of glass-ceramic materials.

PubMed

Johnson, A; Shareef, M Y; Walsh, J M; Hatton, P V; van Noort, R; Hill, R G

1998-11-01

To assess the effect of mould and glass casting temperatures on the biaxial flexural strength (BFS) of two different types of castable glass-ceramic, using existing laboratory equipment and techniques. Two castable glass-ceramic materials were evaluated. One glass (LG3) is based on SiO2-Al2O3-P2O5-CaO-CaF2, and is similar in composition to glasses used in the manufacture of glass-ionomer cements. The other glass (SG3) is based on SiO2-K2O-Na2O-CaO-CaF2, and is a canasite-based material. Both materials were used to produce discs of 12 mm diameter and 2 mm thickness using the same lost-wax casting process as used for metal castings. Mould temperatures of between 500 degrees C and 1000 degrees C and glass casting temperatures of between 1100 degrees C and 1450 degrees C were evaluated. The cast discs were cerammed and the biaxial flexural strength determined with a Lloyd 2000 R tester. A significant difference was found for the BFS in the range of mould temperatures evaluated, with the optimum investment mould temperature being 590 degrees C for LG3 and 610 degrees C for SG3 (p = 0.0002 and p = 0.019, respectively). No significant differences were seen between any of the glass casting temperatures evaluated. The mould temperature for castable glass-ceramic materials produced using the lost-wax casting process can have a significant effect on BFS. The optimum mould temperature may differ slightly depending on the type of material being used. The glass casting temperature of these materials does not appear to have a significant effect on BFS.

Limitation of Shrinkage Porosity in Aluminum Rotor Die Casting

NASA Astrophysics Data System (ADS)

Kim, Young-Chan; Choi, Se-Weon; Kim, Cheol-Woo; Cho, Jae-Ik; Lee, Sung-Ho; Kang, Chang-Seog

Aluminum rotor prone to have many casting defects especially large amount of air and shrinkage porosity, which caused eccentricity, loss and noise during motor operation. Many attempts have been made to develop methods of shrinkage porosity control, but still there are some problems to solve. In this research, the process of vacuum squeeze die casting is proposed for limitation of defects. The 6 pin point gated dies which were in capable of local squeeze at the end ring were used. Influences of filling patterns on HPDC were evaluated and the important process control parameters were high injection speed, squeeze length, venting and process conditions. By using local squeeze and vacuum during filling and solidification, air and shrinkage porosity were significantly reduced and the feeding efficiency at the upper end ring was improved 10%. As a result of controlling the defects, the dynamometer test showed improved motor efficiency by more than 4%.

Surface-Casting Synthesis of Mesoporous Zirconia with a CMK-5-Like Structure and High Surface Area.

PubMed

Gu, Dong; Schmidt, Wolfgang; Pichler, Christian M; Bongard, Hans-Josef; Spliethoff, Bernd; Asahina, Shunsuke; Cao, Zhengwen; Terasaki, Osamu; Schüth, Ferdi

2017-09-04

About 15 years ago, the Ryoo group described the synthesis of CMK-5, a material consisting of a hexagonal arrangement of carbon nanotubes. Extension of the surface casting synthesis to oxide compositions, however, was not possible so far, in spite of many attempts. Here it is demonstrated, that crystalline mesoporous hollow zirconia materials with very high surface areas up to 400 m 2  g -1 , and in selected cases in the form of CMK-5-like, are indeed accessible via such a surface casting process. The key for the successful synthesis is an increased interaction between the silica hard template surface and the zirconia precursor species by using silanol group-rich mesoporous silica as a hard template. The surface areas of the obtained zirconias exceed those of conventionally hard-templated ones by a factor of two to three. The surface casting process seems to be applicable also to other oxide materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of polymer nano composite patterns using fused deposition modeling for rapid investment casting process

NASA Astrophysics Data System (ADS)

Vivek, Tiwary; Arunkumar, P.; Deshpande, A. S.; Vinayak, Malik; Kulkarni, R. M.; Asif, Angadi

2018-04-01

Conventional investment casting is one of the oldest and most economical manufacturing techniques to produce intricate and complex part geometries. However, investment casting is considered economical only if the volume of production is large. Design iterations and design optimisations in this technique proves to be very costly due to time and tooling cost for making dies for producing wax patterns. However, with the advent of Additive manufacturing technology, plastic patterns promise a very good potential to replace the wax patterns. This approach can be very useful for low volume production & lab requirements, since the cost and time required to incorporate the changes in the design is very low. This research paper discusses the steps involved for developing polymer nanocomposite filaments and checking its suitability for investment castings. The process parameters of the 3D printer machine are also optimized using the DOE technique to obtain mechanically stronger plastic patterns. The study is done to develop a framework for rapid investment casting for lab as well as industrial requirements.

Riser Feeding Evaluation Method for Metal Castings Using Numerical Analysis

NASA Astrophysics Data System (ADS)

Ahmad, Nadiah

One of the design aspects that continues to create a challenge for casting designers is the optimum design of casting feeders (risers). As liquid metal solidifies, the metal shrinks and forms cavities inside the casting. In order to avoid shrinkage cavities, risers are added to the casting shape to supply additional molten metal when shrinkage occurs during solidification. The shrinkage cavities in the casting are compensated by controlling the cooling rate to promote directional solidification. This control can be achieved by designing the casting such that the cooling begins at the sections that are farthest away from the risers and ends at the risers. Therefore, the risers will solidify last and feed the casting with the molten metal. As a result, the shrinkage cavities formed during solidification are in the risers which are later removed from the casting. Since casting designers have to usually go through iterative processes of validating the casting designs which are very costly due to expensive simulation processes or manual trials and errors on actual casting processes, this study investigates more efficient methods that will help casting designers utilize their casting experiences systematically to develop good initial casting designs. The objective is to reduce the casting design method iterations; therefore, reducing the cost involved in that design processes. The aim of this research aims at finding a method that can help casting designers design effective risers used in sand casting process of aluminum-silicon alloys by utilizing the analysis of solidification simulation. The analysis focuses on studying the significance of pressure distribution of the liquid metal at the early stage of casting solidification, when heat transfer and convective fluid flow are taken into account in the solidification simulation. The mathematical model of casting solidification was solved using the finite volume method (FVM). This study focuses to improve our understanding of the feeding behavior in aluminum-silicon alloys and the effective feeding by considering the pressure gradient distribution of the molten metal at casting dendrite coherency point. For this study, we will identify the relationship between feeding efficiency, shrinkage behavior and how the change in riser size affects the pressure gradient in the casting. This understanding will be used to help in the design of effective risers.

Improvements in Fabrication of Sand/Binder Cores for Casting

NASA Technical Reports Server (NTRS)

Bakhitiyarov, Sayavur I.; Overfelt, Ruel A.; Adanur, Sabit

2005-01-01

Three improvements have been devised for the cold-box process, which is a special molding process used to make sand/binder cores for casting hollow metal parts. These improvements are: The use of fiber-reinforced composite binder materials (in contradistinction to the non-fiber-reinforced binders used heretofore), The substitution of a directed-vortex core-blowing subprocess for a prior core-blowing process that involved a movable gassing plate, and The use of filters made from filtration-grade fabrics to prevent clogging of vents. For reasons that exceed the scope of this article, most foundries have adopted the cold-box process for making cores for casting metals. However, this process is not widely known outside the metal-casting industry; therefore, a description of pertinent aspects of the cold-box process is prerequisite to a meaningful description of the aforementioned improvements. In the cold-box process as practiced heretofore, sand is first mixed with a phenolic resin (considered to be part 1 of a three-part binder) and an isocyanate resin (part 2 of the binder). Then by use of compressed air, the mixture is blown into a core box, which is a mold for forming the core. Next, an amine gas (part 3 of the binder) that acts as a catalyst for polymerization of parts 1 and 2 is blown through the core box. Alternatively, a liquid amine that vaporizes during polymerization can be incorporated into the sand/resin mixture. Once polymerization is complete, the amine gas is purged from the core box by use of compressed air. The finished core is then removed from the core box.

Implementation of Cyber-Physical Production Systems for Quality Prediction and Operation Control in Metal Casting.

PubMed

Lee, JuneHyuck; Noh, Sang Do; Kim, Hyun-Jung; Kang, Yong-Shin

2018-05-04

The prediction of internal defects of metal casting immediately after the casting process saves unnecessary time and money by reducing the amount of inputs into the next stage, such as the machining process, and enables flexible scheduling. Cyber-physical production systems (CPPS) perfectly fulfill the aforementioned requirements. This study deals with the implementation of CPPS in a real factory to predict the quality of metal casting and operation control. First, a CPPS architecture framework for quality prediction and operation control in metal-casting production was designed. The framework describes collaboration among internet of things (IoT), artificial intelligence, simulations, manufacturing execution systems, and advanced planning and scheduling systems. Subsequently, the implementation of the CPPS in actual plants is described. Temperature is a major factor that affects casting quality, and thus, temperature sensors and IoT communication devices were attached to casting machines. The well-known NoSQL database, HBase and the high-speed processing/analysis tool, Spark, are used for IoT repository and data pre-processing, respectively. Many machine learning algorithms such as decision tree, random forest, artificial neural network, and support vector machine were used for quality prediction and compared with R software. Finally, the operation of the entire system is demonstrated through a CPPS dashboard. In an era in which most CPPS-related studies are conducted on high-level abstract models, this study describes more specific architectural frameworks, use cases, usable software, and analytical methodologies. In addition, this study verifies the usefulness of CPPS by estimating quantitative effects. This is expected to contribute to the proliferation of CPPS in the industry.

Optimization of Casting Design Parameters on Fabrication of Reliable Semi-Solid Aluminum Suspension Control Arm

NASA Astrophysics Data System (ADS)

Ragab, Kh. A.; Bouaicha, A.; Bouazara, M.

2017-09-01

The semi-solid casting process has the advantage of providing reliable mechanical aluminum parts that work continuously in dynamic as control arm of the suspension system in automotive vehicles. The quality performance of dynamic control arm is related to casting mold and gating system designs that affect the fluidity of semi-solid metal during filling the mold. Therefore, this study focuses on improvement in mechanical performance, depending on material characterization, and casting design optimization, of suspension control arms made of A357 aluminum semi-solid alloys. Mechanical and design analyses, applied on the suspension arm, showed the occurrence of mechanical failures at unexpected weak points. Metallurgical analysis showed that the main reason lies in the difficult flow of semi-solid paste through the thin thicknesses of a complex geometry. A design modification procedure is applied to the geometry of the suspension arm to avoid this problem and to improve its quality performance. The design modification of parts was carried out by using SolidWorks design software, evaluation of constraints with ABAQUS, and simulation of flow with ProCast software. The proposed designs showed that the modified suspension arm, without ribs and with a central canvas designed as Z, is considered as a perfect casting design showing an increase in the structural strength of the component. In this case, maximum von Mises stress is 199 MPa that is below the yield strength of the material. The modified casting mold design shows a high uniformity and minim turbulence of molten metal flow during semi-solid casting process.

High-temperature ceramic heat exchanger element for a solar thermal receiver

NASA Technical Reports Server (NTRS)

Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

1982-01-01

A study was performed by AiResearch Manufacturing Company, a division of The Garrett Corporation, on the development a high-temperature ceramic heat exchanger element to be integrated into a solar receiver producing heated air. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is to be fabricated by an innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. The unit is sized to produce 2150 F ar at 2.7 atm pressure, with a pressure drop of about 2 percent of the inlet pressure. This size is compatible with a solar collector providing a receiver input of 85 kw(th). Fabrication of a one-half scale demonstrator ceramic receiver has been completed.

Hydroxyapatite scaffolds processed using a TBA-based freeze-gel casting/polymer sponge technique.

PubMed

Yang, Tae Young; Lee, Jung Min; Yoon, Seog Young; Park, Hong Chae

2010-05-01

A novel freeze-gel casting/polymer sponge technique has been introduced to fabricate porous hydroxyapatite scaffolds with controlled "designer" pore structures and improved compressive strength for bone tissue engineering applications. Tertiary-butyl alcohol (TBA) was used as a solvent in this work. The merits of each production process, freeze casting, gel casting, and polymer sponge route were characterized by the sintered microstructure and mechanical strength. A reticulated structure with large pore size of 180-360 microm, which formed on burn-out of polyurethane foam, consisted of the strut with highly interconnected, unidirectional, long pore channels (approximately 4.5 microm in dia.) by evaporation of frozen TBA produced in freeze casting together with the dense inner walls with a few, isolated fine pores (<2 microm) by gel casting. The sintered porosity and pore size generally behaved in an opposite manner to the solid loading, i.e., a high solid loading gave low porosity and small pore size, and a thickening of the strut cross section, thus leading to higher compressive strengths.

Influence of rotational speed of centrifugal casting process on appearance, microstructure, and sliding wear behaviour of Al-2Si cast alloy

NASA Astrophysics Data System (ADS)

Mukunda, P. G.; Shailesh, Rao A.; Rao, Shrikantha S.

2010-02-01

Although the manner in which the molten metal flows plays a major role in the formation of the uniform cylinder in centrifugal casting, not much information is available on this topic. The flow in the molten metal differs at various rotational speeds, which in turn affects the final casting. In this paper, the influence of the flow of molten metal of hyper eutectic Al-2Si alloys at various rotational speeds is discussed. At an optimum speed of 800 rpm, a uniform cylinder was formed. For the rotational speeds below and above these speeds, an irregular shaped casting was formed, which is mainly due to the influence of melt. Primary á-Al particles were formed in the tube periphery at low rotational speed, and their sizes and shapes were altered with changes in rotational speeds. The wear test for the inner surface of the casting showed better wear properties for the casting prepared at the optimum speed of rotation.

Mathematical Model of Solidification During Electroslag Casting of Pilger Roll

NASA Astrophysics Data System (ADS)

Liu, Fubin; Li, Huabing; Jiang, Zhouhua; Dong, Yanwu; Chen, Xu; Geng, Xin; Zang, Ximin

A mathematical model for describing the interaction of multiple physical fields in slag bath and solidification process in ingot during pilger roll casting with variable cross-section which is produced by the electroslag casting (ESC) process was developed. The commercial software ANSYS was applied to calculate the electromagnetic field, magnetic driven fluid flow, buoyancy-driven flow and heat transfer. The transportation phenomenon in slag bath and solidification characteristic of ingots are analyzed for variable cross-section with variable input power under the conditions of 9Cr3NiMo steel and 70%CaF2 - 30%Al2O3 slag system. The calculated results show that characteristic of current density distribution, velocity patterns and temperature profiles in the slag bath and metal pool profiles in ingot have distinct difference at variable cross-sections due to difference of input power and cooling condition. The pool shape and the local solidification time (LST) during Pilger roll ESC process are analyzed.

Simulation for grinding balls production using sand mold-gravity casting

NASA Astrophysics Data System (ADS)

Nurjaman, F.; Shofi, A.; Herlina, U.; Prilitasari, N. M.; Triapriani, Y.

2018-01-01

In this present work, the grinding balls from high chromium white cast iron (ASTM A-532) were produced by using sand mold-gravity casting. The simulation casting process was conducted before making these grinding balls by using SOLIDCast™ version 8.2.0. The gating system design and the pouring temperature of hot metal were investigated clearly to obtain grinding balls with no-defect. The sound casting of grinding balls was resulted by using the proper gating system with the addition of vent air on the top of each grinding ball’s mold. The dimension of vent air was reduced by the increasing of pouring temperature, thus it resulted on the increasing of the yield production of grinding balls.

Rapid Prototyping Technology for Manufacturing GTE Turbine Blades

NASA Astrophysics Data System (ADS)

Balyakin, A. V.; Dobryshkina, E. M.; Vdovin, R. A.; Alekseev, V. P.

2018-03-01

The conventional approach to manufacturing turbine blades by investment casting is expensive and time-consuming, as it takes a lot of time to make geometrically precise and complex wax patterns. Turbine blade manufacturing in pilot production can be sped up by accelerating the casting process while keeping the geometric precision of the final product. This paper compares the rapid prototyping method (casting the wax pattern composition into elastic silicone molds) to the conventional technology. Analysis of the size precision of blade casts shows that silicon-mold casting features sufficient geometric precision. Thus, this method for making wax patterns can be a cost-efficient solution for small-batch or pilot production of turbine blades for gas-turbine units (GTU) and gas-turbine engines (GTE). The paper demonstrates how additive technology and thermographic analysis can speed up the cooling of wax patterns in silicone molds. This is possible at an optimal temperature and solidification time, which make the process more cost-efficient while keeping the geometric quality of the final product.

A high temperature ceramic heat exchanger element for a solar thermal receiver

NASA Technical Reports Server (NTRS)

Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

1982-01-01

The development of a high-temperature ceramic heat exchanger element to be integrated into a solar receiver producing heated air was studied. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is to be fabricated by a innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. The unit is sized to produce 2150 F air at 2.7 atm pressure, with a pressure drop of about 2 percent of the inlet pressure. This size is compatible with a solar collector providing a receiver input of 85 kw(th). Fabrication of a one-half scale demonstrator ceramic receiver was completed.

Melt Conditioning of Light Metals by Application of High Shear for Improved Microstructure and Defect Control

NASA Astrophysics Data System (ADS)

Patel, Jayesh B.; Yang, Xinliang; Mendis, Chamini L.; Fan, Zhongyun

2017-04-01

Casting is the first step toward the production of majority of metal products whether the final processing step is casting or other thermomechanical processes such as extrusion or forging. The high shear melt conditioning provides an easily adopted pathway to producing castings with a more uniform fine-grained microstructure along with a more uniform distribution of the chemical composition leading to fewer defects as a result of reduced shrinkage porosities and the presence of large oxide films through the microstructure. The effectiveness of high shear melt conditioning in improving the microstructure of processes used in industry illustrates the versatility of the high shear melt conditioning technology. The application of high shear process to direct chill and twin roll casting process is demonstrated with examples from magnesium melts.

Characterization and Evaluation of Incorporation the Casting Sand in Mortar

NASA Astrophysics Data System (ADS)

Zanelato, E. B.; Azevedo, A. R. G.; Alexandre, J.; Xavier, C. G.; Monteiro, S. N.; Mendonça, T. A. O.

The process of casting metals and alloys occurs through the fusion of this metal and its subsequent casting into a mold with the dimensions and geometry close to the final piece. Most foundries use sand casting molds for making you. This work aims to characterize and evaluate the foundry sand to allow its use in segments of Civil Engineering, creating a viable destination for a residue is that discarded. The following characterization tests were performer: particle size, chemical analysis, X-ray Diffraction and Density Real grain. For the execution of the test specimens was used to 1:3 cement and sand, and the incorporation of 10% and 20% of the total mass replacing the sand, and the trace reference. The results show that best results in compression and bending tests were obtained by replacing 10 % of common sand for sand casting.

High-Temperature Creep Behaviour and Positive Effect on Straightening Deformation of Q345c Continuous Casting Slab

NASA Astrophysics Data System (ADS)

Guo, Long; Zhang, Xingzhong

2018-03-01

Mechanical and creep properties of Q345c continuous casting slab subjected to uniaxial tensile tests at high temperature were considered in this paper. The minimum creep strain rate and creep rupture life equations whose parameters are calculated by inverse-estimation using the regression analysis were derived based on experimental data. The minimum creep strain rate under constant stress increases with the increase of the temperature from 1000 °C to 1200 °C. A new casting machine curve with the aim of fully using high-temperature creep behaviour is proposed in this paper. The basic arc segment is cancelled in the new curve so that length of the straightening area can be extended and time of creep behaviour can be increased significantly. For the new casting machine curve, the maximum straightening strain rate at the slab surface is less than the minimum creep strain rate. So slab straightening deformation based on the steel creep behaviour at high temperature can be carried out in the process of Q345c steel continuous casting. The effect of creep property at high temperature on slab straightening deformation is positive. It is helpful for the design of new casting machine and improvement of old casting machine.

Casting copper to tungsten for high-power arc lamp cathodes

NASA Technical Reports Server (NTRS)

Will, H. A.

1974-01-01

Voids forming at interface when copper is cast onto tungsten can be eliminated by adding wetting agent during casting process. Small amount of copper and nickel are cast onto thoriated tungsten insert, insert is recast with more copper to form electrode. Good thermal conductance results in long-lived cathode.

Processing of IN-718 Lattice Block Castings

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G.

2002-01-01

Recently a low cost casting method known as lattice block casting has been developed by JAM Corporation, Wilmington, Massachusetts for engineering materials such as aluminum and stainless steels that has shown to provide very high stiffness and strength with only a fraction of density of the alloy. NASA Glenn Research Center has initiated research to investigate lattice block castings of high temperature Ni-base superalloys such as the model system Inconel-718 (IN-718) for lightweight nozzle applications. Although difficulties were encountered throughout the manufacturing process , a successful investment casting procedure was eventually developed. Wax formulation and pattern assembly, shell mold processing, and counter gravity casting techniques were developed. Ten IN-718 lattice block castings (each measuring 15-cm wide by 30-cm long by 1.2-cm thick) have been successfully produced by Hitchiner Gas Turbine Division, Milford, New Hampshire, using their patented counter gravity casting techniques. Details of the processing and resulting microstructures are discussed in this paper. Post casting processing and evaluation of system specific mechanical properties of these specimens are in progress.

A Brief History of Physics in China,

DTIC Science & Technology

1982-07-29

not attracted by magnets. Chang Hua noticed that a static charge was produced in combing hair and in undressing with silk and wool garments. He...after the expiration of the greenish white gas. It is at this moment that casting can be performed’. For the process of smelting and casting, since there...orange, then yellow, and appears white at about 1000°C. In the process of heating pottery and metals, the ancient Chinese mastered the knowledge of

Evaluation of ceramics for stator application: Gas turbine engine report

NASA Technical Reports Server (NTRS)

Trela, W.; Havstad, P. H.

1978-01-01

Current ceramic materials, component fabrication processes, and reliability prediction capability for ceramic stators in an automotive gas turbine engine environment are assessed. Simulated engine duty cycle testing of stators conducted at temperatures up to 1093 C is discussed. Materials evaluated are SiC and Si3N4 fabricated from two near-net-shape processes: slip casting and injection molding. Stators for durability cycle evaluation and test specimens for material property characterization, and reliability prediction model prepared to predict stator performance in the simulated engine environment are considered. The status and description of the work performed for the reliability prediction modeling, stator fabrication, material property characterization, and ceramic stator evaluation efforts are reported.

Long-Term Resolution of Severe Ankle Contractures Using Botulinum Toxin, Serial Casting, Splinting, and Motor Retraining.

PubMed

Leung, Joan; Stroud, Katarina

2018-01-01

Purpose: Serial casting for ankle contractures is traditionally performed in prone, a position that patients may not easily tolerate. Also, although serial casting is effective in correcting contracture, its effect dissipates quickly. This case report describes a procedure for performing casting for ankle contractures in a supine or sitting position. It also describes a process that enables the effect of serial casting to be maintained long term. Client Description: The client was an adult who had suffered traumatic brain injury and severe bilateral ankle contractures. Intervention: He received botulinum toxin and serial casting for his bilateral ankle contractures, one ankle at 8 months and the other at 13 months after the injury. He then underwent a programme of splinting and motor training. Measures and Outcome: The client gained more than 40° dorsiflexion for both ankles after receiving botulinum toxin injections and serial casting. The improvement in ankle range enabled him to progress to walking practice. Ankle splinting was gradually reduced. On discharge at 25 months post-injury, the ankle joint range was maintained. Implications: The use of botulinum toxin and serial casting, followed by an intensive programme of splinting and motor training, may be an option to consider for effective long-term resolution of severe contractures after acquired brain injury.

Molding of strength testing samples using modern PDCPD material for purpose of automotive industry

NASA Astrophysics Data System (ADS)

Grabowski, L.; Baier, A.; Sobek, M.

2017-08-01

The casting of metal materials is widely known but the molding of composite polymer materials is not well-known method still. The initial choice of method for producing composite bodies was the method of casting of PDCPD material. For purpose of performing casting of polymer composite material, a special mold was made. Firstly, the 3D printed, using PLA material, mold was used. After several attempts of casting PDCPD many problems were encountered. The second step was to use mold milled from a firm and dense isocyanate foam. After several attempts research shown that this solution is more resistant to high-temperature peak, but this material is too fragile to use it several times. This solution also prevents mold from using external heating, which can be necessary for performing correct molding process. The last process was to use the aluminum mold, which is dedicated to PDCPD polymer composite, because of low adhesiveness. This solution leads to perform correct PDCPD polymer composite material injection. After performing casting operation every PDCPD testing samples were tested. These results were compared together. The result of performed work was to archive correct properties of injection of composite material. Research and results were described in detail in this paper.

TiC-Fe-Based Composite Coating Prepared by Self-Propagating High-Temperature Synthesis

NASA Astrophysics Data System (ADS)

He, Shen; Fan, Xi'an; Chang, Qingming; Xiao, Lixiang

2017-06-01

TiC-Fe-based composite coatings were prepared in situ by self-propagating high-temperature synthesis combined with vacuum expendable pattern casting process. The band-like TiC phase embedded in a continuous Fe binder. There were no obvious defects and impurities at the interface between coatings and matrices. Fe presented consecutively in the coating zones and substrate zones without interruption and the microhardness in the cross-sectional area of the coating-matrix reduces continuously from the coating to the matrix area, indicating a good metallurgical bonding between the coatings and matrices. The effect of casting temperature on the microstructure and hardness of TiC-Fe-based composite coating was investigated in detail. The TiC particles formed at low casting temperature were nearly spherical in shape, and the size of TiC particles increased with increasing casting temperature due to more agglomeration. The hardness of the coatings increased first and then decreased with increasing casting temperature, and reached the highest value of 68 HRC when the casting temperature was 1773 K (1500 °C), which was twice more than that of the matrix.

Fabrication of Ti-0.48Al Alloy by Centrifugal Casting.

PubMed

Park, Jong Bum; Lee, Jung-Il; Ryu, Jeong Ho

2018-09-01

Many of the unique properties of TiAl alloys that make are attractive for use in high-temperature structural applications also make it challenging to process them into useful products. Cast TiAl is rapidly nearing commercialization, particularly in the vehicle industry, owing to its low production cost. In this study, the centrifugal casting of a TiAl (Ti-48%Al, mole fraction) turbocharger was simulated and an experimental casting was created in vacuum using an induction melting furnace coupled to a ceramic composite mold. Numerical simulation results agreed with the experiment. The crystal structure, microstructure, and chemical composition of the TiAl prepared by centrifugal casting were studied by X-ray diffractometry, optical microscopy, field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). FE-SEM and EDS examinations of the TiAl casting revealed that the thickness of the oxide layer (α-case) was typically less than 35 μm.

Designing High Performance Steel Castings Today: Proceedings of the Steel Founders Society of America, Technical and Operating Conference December 7-10, 2016Chicago, IL

DTIC Science & Technology

2016-12-10

will be 2 x failure (critical) depth. G. INSPECTION REQUIREMENTS Either the No- Bake sand or Investment process is selected based on which... Bake sand and the Investment Casting Handbook by the Investment Casting Institute has the tolerance values for investment castings. Typically there

The Design and Construction Process of a Test Stand for Casting the Power Steering’S Housing with the Use of the Pdcpd Material

NASA Astrophysics Data System (ADS)

Sobek, M.; Baier, A.; Grabowski, Ł.

2018-01-01

The use of new technologies and materials in various industries is a natural process that is directly related to the very high rate of development of these technologies. Certain industries decide to much faster introduce new technologies and materials. One of such branches is the automotive industry, whose representatives are very energetically looking for both financial savings and savings resulting from the vehicles mass reduction. An economically justified approach to construction materials is leading the search for new solutions and materials. The use of a modern material such as the two-component PDCPD composite shows hitherto unknown possibilities of producing subassemblies of many different constructions. The possibility of using a modern composite material with parameters comparable to that of metals and significantly lighter, can be an excellent alternative in the selection of materials for many parts of motor vehicles. The potentiality of precise casting of tolerated surfaces will allow to reduce the operations related to machining process, which is an indispensable part of the production process of elements that are cast of metal. This article describes the process of designing and building a test stand for precise positioning of power steering gear components at the stage of casting their housing. The article presents the principle of operation of the test stand and the process of preparation for the casting and the cast itself will be rudely described. Due to the implementation of research as part of a research project with an industrial partner, the article will only describe some operations. This is related to the confidentiality of the project.

The influence of cooling parameters on the speed of continuous steel casting

NASA Astrophysics Data System (ADS)

Tirian, G. O.; Gheorghiu, C. A.; Hepuţ, T.; Chioncel, C. P.

2018-01-01

This paper analyzes the cooling parameters of the continuous casting speed. In the researches carried out we aimed to establish some correlation equations between the parameters characterizing the continuous casting process, the temperature of the steel at the entrance to the crystallizer, the superheating of the steel and the flow of the cooling water in the crystallizer and different zones of the secondary cooling. Parallel to these parameters were also the values for the casting speed. The research was made for the casting of round ϕ270mm semi-finished steel products. The steel was developed in an electric EBT furnace with a capacity of 100t, treated in L.F. (Ladle - Furnace) and VD (Vacuum-Degassing) and poured in a 5-wire continuous casting plant. The obtained data was processed in MATLAB using three types of correlation equations. The obtained results are presented both in the analytical and graphical form, each correlation being analyzed from the technological point of view, indicating the optimal values for the independent parameters monitored. In the analysis we present a comparison between the results obtained after the three types of equations for each correlation.

Coupled thermal-fluid-mechanics analysis of twin roll casting of A7075 aluminum alloy

NASA Astrophysics Data System (ADS)

Lee, Yun-Soo; Kim, Hyoung-Wook; Cho, Jae-Hyung; Chun, Se-Hwan

2017-09-01

Better understanding of temperature distribution and roll separation force during twin roll casting of aluminum alloys is critical to successfully fabricate good quality of aluminum strips. Therefore, the simulation techniques are widely applied to understand the twin roll casting process in a comprehensive way and to reduce the experimental time and cost of trial and error. However, most of the conventional approaches are considered thermally coupled flow, or thermally coupled mechanical behaviors. In this study, a fully coupled thermal-fluid-mechanical analysis of twin roll casting of A7075 aluminum strips was carried out using the finite element method. Temperature profile, liquid fraction and metal flow of aluminum strips with different thickness were predicted. Roll separation force and roll temperatures were experimentally obtained from a pilot-scale twin roll caster, and those results were compared with model predictions. Coupling the fluid of the liquid melt to the thermal and mechanical modeling reasonably predicted roll temperature distribution and roll separation force during twin roll casting.

Breaking into the Business: Experiences of Actors with Disabilities in the Entertainment Industry

ERIC Educational Resources Information Center

Raynor, Olivia; Hayward, Katharine

2009-01-01

The pursuit of an acting career is a difficult one for anybody. However, studies have yet to factor how disability affects casting opportunities. This study describes the employment of actors with disabilities, along with the unique barriers they encounter in the audition and casting process. Actors with disabilities from the Screen Actors Guild…

Direct metal laser sintering: a digitised metal casting technology.

PubMed

Venkatesh, K Vijay; Nandini, V Vidyashree

2013-12-01

Dental technology is undergoing advancements at a fast pace and technology is being imported from various other fields. One such imported technology is direct metal laser sintering technology for casting metal crowns. This article will discuss the process of laser sintering for making metal crowns and fixed partial dentures with a understanding of their pros and cons.

The Influence of Vanadium Microalloying on the Production of Thin Slab Casting and Direct Rolled Steel Strip

NASA Astrophysics Data System (ADS)

Li, Yu; Milbourn, David

Vanadium microalloying is highly effective in high strength strip steels produced by thin slab casting and direct rolled process. Because of the high solubility of V(C,N) in austenite, vanadium is likely to remain in solution during casting, equalisation and rolling. Vanadium microalloyed steels have better hot ductility and are less prone to transverse cracking than niobium containing steels. Despite a coarse as-cast austenite grain size before rolling, significant grain refinement can be achieved in vanadium microalloyed steels by repeated recrystallization during rolling, resulting in a fine uniform ferrite microstructure in final strip. Almost all vanadium present in microalloyed steels is available to precipitate in ferrite as very fine particles, contributing to precipitation strengthening. Vanadium microalloyed steels show less sensitivity to rolling process variables and exhibit excellent combination of strength and toughness.

Design and optimization of the micro-engine turbine rotor manufacturing using the rapid prototyping technology

NASA Astrophysics Data System (ADS)

Vdovin, R. A.; Smelov, V. G.

2017-02-01

This work describes the experience in manufacturing the turbine rotor for the micro-engine. It demonstrates the design principles for the complex investment casting process combining the use of the ProCast software and the rapid prototyping techniques. At the virtual modelling stage, in addition to optimized process parameters, the casting structure was improved to obtain the defect-free section. The real production stage allowed demonstrating the performance and fitness of rapid prototyping techniques for the manufacture of geometrically-complex engine-building parts.

Process research into metallic pipe wear of hot chamber die casting machines and methods ofincreasing wear resistance

NASA Astrophysics Data System (ADS)

Mukhametzyanova, G. F.; Kolesnikov, MS; Mukhametzyanov, I. R.; Astatshenko, V. I.

2017-09-01

The kinetics and reasons for metallic pipe wear of hot chamberzinc alloy die casting machines are established.Increasing metallic pipe wear components wear resistance is being achieved by means of die steelДИ - 22 with electroslag remelting modification and electron-beamremelting modification and after the processes of nitriding and boriding besides.

Triple Plate Mold Final Report: Optimization of the Mold Design and Casting Parameters for a Thin U-10mo Fuel Casting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aikin, Jr., Robert M.

This work describes the experiments and modeling that have been performed to improve and try to optimize the simultaneous casting of three plates of U-10wt%Mo in a single coil vacuum induction melting (VIM) furnace. The plates of interest are 280 mm wide by 203 mm tall by 5 mm thick (11" x 8" x 0.2"). The initial mold design and processing parameters were supplied by Y-12. The mold and casting cavity were instrumented with a number of thermocouples, and the casting performed to determine the thermal history of the mold and casting. The resulting cast plates were radiographed and numerousmore » defects identified. Metallography was performed to help identify the nature of the radiographically observed defects. This information was then used to validate a mold filling and solidification model of that casting. Based on the initial casting, good casting design practice, and process simulation of several design alternatives, a revised design was developed with the goal of minimizing casting defects such as porosity. The redesigned mold had a larger hot-top and had its long axis along the horizontal direction. These changes were to try to develop a strong thermal gradient conducive to good feeding and minimization of micro- and macroporosity in the cast plates. An instrumented casting was then performed with the revised mold design and a linear distributor. This design yielded cast plates with significantly less radiographically identified defects. Unfortunately, there was significant variation in plate weight and metal content in their hot-tops. Fluid flow simulations were then performed on this mold/distributor design. This helped identify the issue with this linear distributor design. Additional simulations were then performed on candidate distributor redesigns and a preferred distributor annular design was identified. This improved annular design was used to produce a third instrumented casting with favorable results. These refined designs and their radiographic characterization are compared to the initial design.« less

Finite Element Analysis of Laser Engineered Net Shape (LENS™) Tungsten Clad Squeeze Pins

NASA Astrophysics Data System (ADS)

Sakhuja, Amit; Brevick, Jerald R.

2004-06-01

In the aluminum high-pressure die-casting and indirect squeeze casting processes, local "squeeze" pins are often used to minimize internal solidification shrinkage in heavy casting sections. Squeeze pins frequently fail in service due to molten aluminum adhering to the H13 tool steel pins ("soldering"). A wide variety of coating materials and methods have been developed to minimize soldering on H13. However, these coatings are typically very thin, and experience has shown their performance on squeeze pins is highly variable. The LENS™ process was employed in this research to deposit a relatively thick tungsten cladding on squeeze pins. An advantage of this process was that the process parameters could be precisely controlled in order to produce a satisfactory cladding. Two fixtures were designed and constructed to enable the end and outer diameter (OD) of the squeeze pins to be clad. Analyses were performed on the clad pins to evaluate the microstructure and chemical composition of the tungsten cladding and the cladding-H13 substrate interface. A thermo-mechanical finite element analysis (FEA) was performed to assess the stress distribution as a function of cladding thickness on the pins during a typical casting thermal cycle. FEA results were validated via a physical test, where the clad squeeze pins were immersed into molten aluminum. Pins subjected to the test were evaluated for thermally induced cracking and resistance to soldering of the tungsten cladding.

Ceramic processing: Experimental design and optimization

NASA Technical Reports Server (NTRS)

Weiser, Martin W.; Lauben, David N.; Madrid, Philip

1992-01-01

The objectives of this paper are to: (1) gain insight into the processing of ceramics and how green processing can affect the properties of ceramics; (2) investigate the technique of slip casting; (3) learn how heat treatment and temperature contribute to density, strength, and effects of under and over firing to ceramic properties; (4) experience some of the problems inherent in testing brittle materials and learn about the statistical nature of the strength of ceramics; (5) investigate orthogonal arrays as tools to examine the effect of many experimental parameters using a minimum number of experiments; (6) recognize appropriate uses for clay based ceramics; and (7) measure several different properties important to ceramic use and optimize them for a given application.

Ceramic technology for solar thermal receivers

NASA Technical Reports Server (NTRS)

Kudirka, A. A.; Smoak, R. H.

1981-01-01

The high-temperature capability, resistance to corrosive environments and non-strategic nature of ceramics have prompted applications in the solar thermal field whose advantages over metallic devices of comparable performance may begin to be assessed. It is shown by a survey of point-focusing receiver designs employing a variety of ceramic compositions and fabrication methods that the state-of-the-art in structural ceramics is not sufficiently advanced to fully realize the promised benefits of higher temperature capabilities at lower cost than metallic alternatives. The ceramics considered include alumina, berylia, magnesia, stabilized zirconia, fused silica, silicon nitride, silicon carbide, mullite and cordierite, processed by such methods as isostatic pressing, dry pressing, slip casting, extrusion, calendaring and injection molding.

Method and apparatus for improved melt flow during continuous strip casting

DOEpatents

Follstaedt, Donald W.; King, Edward L.; Schneider, Ken C.

1991-11-12

The continuous casting of metal strip using the melt overflow process is improved by controlling the weir conditions in the nozzle to provide a more uniform flow of molten metal across the width of the nozzle and reducing the tendency for freezing of metal along the interface with refractory surfaces. A weir design having a sloped rear wall and tapered sidewalls and critical gap controls beneath the weir has resulted in the drastic reduction in edge tearing and a significant improvement in strip uniformity. The floor of the container vessel is preferably sloped and the gap between the nozzle and the rotating substrate is critically controlled. The resulting flow patterns observed with the improved casting process have reduced thermal gradients in the bath, contained surface slag and eliminated undesirable solidification near the discharge area by increasing the flow rates at those points.

Cavitation During Superplastic Forming

PubMed Central

Campbell, John

2011-01-01

Cavitation is the opening of pores during superplastic forming, typically at grain boundary triple points or on second phase grain boundary particles during slip of grain boundaries. Theories for the initiation of cavitation are reviewed. It seems that cavitation is unlikely to occur by processes intrinsic to metals such as dislocation mechanisms or point defect condensation. It is proposed that cavitation can only occur at non-bonded interfaces such as those introduced extrinsically (i.e., from the outside) during the original casting of the metal. These defects, known as oxide bifilms, are naturally introduced during pouring of the liquid metal, and are frozen into the solid, often pushed by dendritic growth into grain boundaries where they are difficult to detect because of their extreme thinness, often measured in nanometres. Their unbonded central interface acts as a crack and can initiate cavitation. Second phase precipitates probably do not nucleate and grow on grain boundaries but grow on bifilms in the boundaries, explaining the apparent association between boundaries, second phase particles and failure initiation. Improved melting and casting techniques can provide metal with reduced or zero bifilm population for which cavitation would not be possible, promising significant improvements in superplastic behaviour. PMID:28824142

Precision cast vs. wrought superalloys

NASA Technical Reports Server (NTRS)

Tien, J. K.; Borofka, J. C.; Casey, M. E.

1986-01-01

While cast polycrystalline superalloys recommend themselves in virtue of better 'buy-to-fly' ratios and higher strengthening gamma-prime volume fractions than those of wrought superalloys, the expansion of their use into such critical superalloy applications as gas turbine hot section components has been slowed by insufficient casting process opportunities for microstructural control. Attention is presently drawn, however, to casting process developments facilitating the production of defect-tolerant superalloy castings having improved fracture reliability. Integrally bladed turbine wheel and thin-walled turbine exhaust case near-net-shape castings have been produced by these means.

Energy Saving Melting and Revert Reduction Technology (Energy-SMARRT): Light Metals Permanent Mold Casting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fasoyinu, Yemi

2014-03-31

Current vehicles use mostly ferrous components for structural applications. It is possible to reduce the weight of the vehicle by substituting these parts with those made from light metals such as aluminum and magnesium. Many alloys and manufacturing processes can be used to produce these light metal components and casting is known to be most economical. One of the high integrity casting processes is permanent mold casting which is the focus of this research report. Many aluminum alloy castings used in automotive applications are produced by the sand casting process. Also, aluminum-silicon (Al-Si) alloys are the most widely used alloymore » systems for automotive applications. It is possible that by using high strength aluminum alloys based on an aluminum-copper (Al-Cu) system and permanent mold casting, the performance of these components can be enhanced significantly. This will also help to further reduce the weight. However, many technological obstacles need to be overcome before using these alloys in automotive applications in an economical way. There is very limited information in the open literature on gravity and low-pressure permanent mold casting of high strength aluminum alloys. This report summarizes the results and issues encountered during the casting trials of high strength aluminum alloy 206.0 (Al-Cu alloy) and moderate strength alloy 535.0 (Al-Mg alloy). Five engineering components were cast by gravity tilt-pour or low pressure permanent mold casting processes at CanmetMATERIALS (CMAT) and two production foundries. The results of the casting trials show that high integrity engineering components can be produced successfully from both alloys if specific processing parameters are used. It was shown that a combination of melt processing and mold temperature is necessary for the elimination of hot tears in both alloys.« less

Interlocking multi-material components made of structured steel sheets and high-pressure die cast aluminium

NASA Astrophysics Data System (ADS)

Senge, S.; Brachmann, J.; Hirt, G.; Bührig-Polaczek, A.

2017-10-01

Lightweight design is a major driving force of innovation, especially in the automotive industry. Using hybrid components made of two or more different materials is one approach to reduce the vehicles weight and decrease fuel consumption. As a possible way to increase the stiffness of multi-material components, this paper presents a process chain to produce such components made of steel sheets and high-pressure die cast aluminium. Prior to the casting sequence the steel sheets are structured in a modified rolling process which enables continuous interlocking with the aluminium. Two structures manufactured by this rolling process are tested. The first one is a channel like structure and the second one is a channel like structure with undercuts. These undercuts enable the formation of small anchors when the molten aluminium fills them. The correlation between thickness reduction during rolling and the shape of the resulting structure was evaluated for both structures. It can be stated that channels with a depth of up to 0.5 mm and a width of 1 mm could be created. Undercuts with different size depending on the thickness reduction could be realised. Subsequent aluminium high-pressure die casting experiments were performed to determine if the surface structure can be filled gap-free with molten aluminium during the casting sequence and if a gap-free connection can be achieved after contraction of the aluminium. The casting experiments showed that both structures could be filled during the high-pressure die casting. The channel like structure results in a gap between steel and aluminium after contraction of the cast metal whereas the structure with undercuts leads to a good interlocking resulting in a gap-free connection.

Preparation of Conductive Polymer Graphite (PG) Composites

NASA Astrophysics Data System (ADS)

Munirah Abdullah, Nur; Saddam Kamarudin, M.; Rus, Anika Zafiah M.; Abdullah, M. F. L.

2017-08-01

The preparation of conductive polymer graphite (PG) composites thin film is described. The thickness of the PG composites due to slip casting method was set approximately ~0.1 mm. The optical microscope (OM) and fourier transform infra-red spectroscopy (FTIR) has been operated to distinguish the structure-property relationships scheme of PG composites. It shows that the graphite is homogenously dispersed in polymer matrix composites. The electrical characteristics of the PG composite were measured at room temperature and the electrical conductivity (σ) was discovered with respect of its resistivity (Ω). By achieving conductivity of 103 S/m, it is proven that at certain graphite weight loading (PG20, PG25 and PG30) attributes to electron pathway in PG composites.

Cavitation During Superplastic Forming.

PubMed

Campbell, John

2011-07-08

Cavitation is the opening of pores during superplastic forming, typically at grain boundary triple points or on second phase grain boundary particles during slip of grain boundaries. Theories for the initiation of cavitation are reviewed. It seems that cavitation is unlikely to occur by processes intrinsic to metals such as dislocation mechanisms or point defect condensation. It is proposed that cavitation can only occur at non-bonded interfaces such as those introduced extrinsically (i.e., from the outside) during the original casting of the metal. These defects, known as oxide bifilms, are naturally introduced during pouring of the liquid metal, and are frozen into the solid, often pushed by dendritic growth into grain boundaries where they are difficult to detect because of their extreme thinness, often measured in nanometres. Their unbonded central interface acts as a crack and can initiate cavitation. Second phase precipitates probably do not nucleate and grow on grain boundaries but grow on bifilms in the boundaries, explaining the apparent association between boundaries, second phase particles and failure initiation. Improved melting and casting techniques can provide metal with reduced or zero bifilm population for which cavitation would not be possible, promising significant improvements in superplastic behaviour.

Stacked dielectric elastomer actuator (SDEA): casting process, modeling and active vibration isolation

NASA Astrophysics Data System (ADS)

Li, Zhuoyuan; Sheng, Meiping; Wang, Minqing; Dong, Pengfei; Li, Bo; Chen, Hualing

2018-07-01

In this paper, a novel fabrication process of stacked dielectric elastomer actuator (SDEA) is developed based on casting process and elastomeric electrode. The so-fabricated SDEA benefits the advantages of homogenous and reproducible properties as well as little performance degradation after one-year use. A coupling model of SDEA is established by taking into consideration of the elastomeric electrode and the calculated results agree with the experiments. Based on the model, we attain the method to optimize the SDEA’s parameters. Finally, the SDEA is used as an isolator in active vibration isolation system to verify the feasibility in dynamic application. And the experiment results show a great prospect for SDEA in such application.

Experimental Exploration of Metal Cable as Reinforcement in 3D Printed Concrete.

PubMed

Bos, Freek P; Ahmed, Zeeshan Y; Jutinov, Evgeniy R; Salet, Theo A M

2017-11-16

The Material Deposition Method (MDM) is enjoying increasing attention as an additive method to create concrete mortar structures characterised by a high degree of form-freedom, a lack of geometrical repetition, and automated construction. Several small-scale structures have been realised around the world, or are under preparation. However, the nature of this construction method is unsuitable for conventional reinforcement methods to achieve ductile failure behaviour. Sometimes, this is solved by combining printing with conventional casting and reinforcing techniques. This study, however, explores an alternative strategy, namely to directly entrain a metal cable in the concrete filament during printing to serve as reinforcement. A device is introduced to apply the reinforcement. Several options for online reinforcement media are compared for printability. Considerations specific to the manufacturing process are discussed. Subsequently, pull-out tests on cast and printed specimens provide an initial characterisation of bond behaviour. Bending tests furthermore show the potential of this reinforcement method. The bond stress of cables in printed concrete was comparable to values reported for smooth rebar but lower than that of the same cables in cast concrete. The scatter in experimental results was high. When sufficient bond length is available, ductile failure behaviour for tension parallel to the filament direction can be achieved, even though cable slip occurs. Further improvements to the process should pave the way to achieve better post-crack resistance, as the concept in itself is feasible.

Fabrication and Characterization of Porous MgAl2O4 Ceramics via a Novel Aqueous Gel-Casting Process

PubMed Central

Yuan, Lei; Liu, Zongquan; Liu, Zhenli; He, Xiao; Ma, Beiyue; Zhu, Qiang; Yu, Jingkun

2017-01-01

A novel and aqueous gel-casting process has been successfully developed to fabricate porous MgAl2O4 ceramics by using hydratable alumina and MgO powders as raw materials and deionized water as hydration agent. The effects of different amounts of deionized water on the hydration properties, apparent porosity, bulk density, microstructure, pore size distribution and compressive strength of the samples were investigated. The results indicated that the porosity and the microstructure of porous MgAl2O4 ceramics were governed by the amounts of deionized water added. The porous structure was formed by the liberation of physisorbed water and the decomposition of hydration products such as bayerite, brucite and boehmite. After determining the addition amounts of deionized water, the fabricated porous MgAl2O4 ceramics had a high apparent porosity (52.5–65.8%), a small average pore size structure (around 1–3 μm) and a relatively high compressive strength (12–28 MPa). The novel aqueous gel-casting process with easy access is expected to be a promising candidate for the preparation of Al2O3-based porous ceramics. PMID:29189734

Fabrication and Characterization of Porous MgAl₂O₄ Ceramics via a Novel Aqueous Gel-Casting Process.

PubMed

Yuan, Lei; Liu, Zongquan; Liu, Zhenli; He, Xiao; Ma, Beiyue; Zhu, Qiang; Yu, Jingkun

2017-11-30

A novel and aqueous gel-casting process has been successfully developed to fabricate porous MgAl₂O₄ ceramics by using hydratable alumina and MgO powders as raw materials and deionized water as hydration agent. The effects of different amounts of deionized water on the hydration properties, apparent porosity, bulk density, microstructure, pore size distribution and compressive strength of the samples were investigated. The results indicated that the porosity and the microstructure of porous MgAl₂O₄ ceramics were governed by the amounts of deionized water added. The porous structure was formed by the liberation of physisorbed water and the decomposition of hydration products such as bayerite, brucite and boehmite. After determining the addition amounts of deionized water, the fabricated porous MgAl₂O₄ ceramics had a high apparent porosity (52.5-65.8%), a small average pore size structure (around 1-3 μm) and a relatively high compressive strength (12-28 MPa). The novel aqueous gel-casting process with easy access is expected to be a promising candidate for the preparation of Al₂O₃-based porous ceramics.

Characterization of HEM silicon for solar cells. [Heat Exchanger Method

NASA Technical Reports Server (NTRS)

Dumas, K. A.; Khattak, C. P.; Schmid, F.

1981-01-01

The Heat Exchanger Method (HEM) is a promising low-cost ingot casting process for material used for solar cells. This is the only method that is capable of casting single crystal ingots with a square cross section using a directional solidification technique. This paper describes the chemical, mechanical and electrical properties of the HEM silicon material as a function of position within the ingot.

Casting copper to tungsten for high power arc lamp cathodes

NASA Technical Reports Server (NTRS)

Will, H. A.

1973-01-01

A method for making 400-kW arc lamp cathodes is described. The cathodes are made by casting a 1.75-in. diameter copper body onto a thoriated tungsten insert. The addition of 0.5-percent nickel to the copper prevents voids from forming at the copper-tungsten interface. Cathodes made by this process have withstood more than 110 hours of operation in a 400-kW arc lamp.

A study on atomic diffusion behaviours in an Al-Mg compound casting process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yongning; Chen, Yiqing; Yang, Chunhui, E-mail: r.yang@uws.edu.au

Al and Mg alloys are main lightweight alloys of research interest and they both have superb material properties, i.e., low density and high specific strength, etc. Being different from Al alloys, the corrosion of Mg alloys is much more difficult to control. Therefore to combine merits of these two lightweight alloys as a composite-like structure is an ideal solution through using Al alloys as a protective layer for Mg alloys. Compound casting is a realistic technique to manufacture such a bi-metal structure. In this study, a compound casting technique is employed to fabricate bi-layered samples using Al and Mg andmore » then the samples are analysed using electron probe micro-analyzer (EPMA) to determine diffusion behaviours between Al and Mg. The diffusion mechanism and behaviours between Al and Mg are studied numerically at atomic scale using molecular dynamics (MD) and parametric studies are conducted to find out influences of ambient temperature and pressure on the diffusion behaviours between Al and Mg. The results obtained clearly show the effectiveness of the compound casting process to increase the diffusion between Al and Mg and thus create the Al-base protection layer for Mg.« less

Near-Net-Shape Production of Hollow Titanium Alloy Components via Electrochemical Reduction of Metal Oxide Precursors in Molten Salts

NASA Astrophysics Data System (ADS)

Hu, Di; Xiao, Wei; Chen, George Z.

2013-04-01

Metal oxide precursors (ca. 90 wt pct Ti, 6 wt pct Al, and 4 wt pct V) were prepared with a hollow structure in various shapes such as a sphere, miniature golf club head, and cup using a one-step solid slip-casting process. The precursors were then electro-deoxidized in molten calcium chloride [3.2 V, 1173 K (900 °C)] against a graphite anode. After 24 hours of electrolysis, the near-net-shape Ti-6Al-4V product maintained its original shape with controlled shrinkage. Oxygen contents in the Ti-6Al-4V components were typically below 2000 ppm. The maximum compressive stress and modulus of electrolytic products obtained in this work were approximately 243 MPa and 14 GPa, respectively, matching with the requirement for medical implants. Further research directions are discussed for mechanical improvement of the products via densification during or after electrolysis. This simple, fast, and energy-efficient near-net-shape manufacturing method could allow titanium alloy components with desired geometries to be prepared directly from a mixture of metal oxides, promising an innovative technology for the low-cost production of titanium alloy components.

Natural clinoptilolite composite membranes on tubular stainless steel supports for water softening.

PubMed

Adamaref, Solmaz; An, Weizhu; Jarligo, Maria Ophelia; Kuznicki, Tetyana; Kuznicki, Steven M

2014-01-01

Disk membranes generated from high-purity natural clinoptilolite mineral rock have shown promising water desalination and de-oiling performance. In order to scale up production of these types of membranes for industrial wastewater treatment applications, a coating strategy was devised. A composite mixture of natural clinoptilolite from St. Cloud (Winston, NM, USA) and aluminum phosphate was deposited on the inner surface of porous stainless steel tubes by the slip casting technique. The commercial porous stainless steel tubes were pre-coated with a TiO2 layer of about 10 μm. Phase composition and morphology of the coating materials were investigated using X-ray diffraction and scanning electron microscopy. Water softening performance of the fabricated membranes was evaluated using Edmonton (Alberta, Canada) municipal tap water as feed source. Preliminary experimental results show a high water flux of 7.7 kg/(m(2) h) and 75% reduction of hardness and conductivity in a once-through membrane process at 95 °C and feed pressure of 780 kPa. These results show that natural zeolite coated, stainless steel tubular membranes have high potential for large-scale purification of oil sands steam-assisted gravity drainage water at high temperature and pressure requirements.

Detection and reconstruction of solidification cracks - Laser ultrasonic measurements during the continuous casting process of aluminum

NASA Astrophysics Data System (ADS)

Mitter, Thomas; Grün, Hubert; Roither, Jürgen; Betz, Andreas; Bozorgi, Salar; Reitinger, Bernhard; Burgholzer, Peter

2014-05-01

In the continuous casting process the avoidance and rapid detection of occurring solidification cracks in the slab is a crucial issue, in particular for the maintenance of a high quality level in further production processes. Due to the elevated temperatures of the slab surface a remote sensing non-destructive tool for quality inspection is required, which is also applicable for the harsh industrial environment. In this work the application of laser ultrasound (LUS) technique during the continuous casting process in industrial environment is shown. The proof of principle of the detection of the centered solidification cracks is shown by pulse-echo measurements with laser ultrasonic equipment for inline quality inspection. Preliminary examinations in the lab of different casted samples have shown the distinguishability of slabs with and without any solidification cracks. Furthermore the damping of the bulk wave has been used for the prediction of the dimension of the crack. With an adapted "synthetic aperture focusing technique" (SAFT) algorithm the image reconstruction of multiple measurements at different positions around the circumference has provided enough information for the estimation of the localization and extension of the centered solidification cracks. Subsequent first measurements using this laser ultrasonic setup during the continuous casting of aluminum were carried out and showed the proof of principle in an industrial environment with elevated temperatures, dust, cooling water and vibrations.

Alloy Shrinkage factors for the investment casting of 17-4PH stainless steel parts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabau, Adrian S; Porter, Wallace D

2008-01-01

In this study, the alloy shrinkage factors were obtained for the investment casting of 17-4PH stainless steel parts. For the investment casting process, unfilled wax and fused silica with a zircon prime coat were used for patterns and shell molds, respectively. Dimensions of the die tooling, wax pattern, and casting were measured using a Coordinate Measurement Machine. For all the properties, the experimental data available in the literature did not cover the entire temperature range necessary for process simulation. A comparison between the predicted material property data measured property data is made. It was found that most material properties weremore » accurately predicted over the most of the temperature range of the process. Several assumptions were made in order to obtain a complete set of mechanical property data at high temperatures. Thermal expansion measurements for the 17-4PH alloy were conducted at heating and cooling. As a function of temperature, the thermal expansion for both the alloy and shell mold materials showed different evolution at heating and cooling. Thus, one generic simulation were performed with thermal expansion obtained at heating and another one with thermal expansion obtained at cooling. The alloy dimensions were obtained from numerical simulation results of solidification, heat transfer, and deformation phenomena. As compared with experimental results, the numerical simulation results for the shrinkage factors were slightly over-predicted.« less

Alloy Shrinkage Factors for the Investment Casting of 17-4PH Stainless Steel Parts

NASA Astrophysics Data System (ADS)

Sabau, Adrian S.; Porter, Wallace D.

2008-04-01

In this study, alloy shrinkage factors were obtained for the investment casting of 17-4PH stainless steel parts. For the investment casting process, unfilled wax and fused silica with a zircon prime coat were used for patterns and shell molds, respectively. The dimensions of the die tooling, wax pattern, and casting were measured using a coordinate measurement machine (CMM). For all the properties, the experimental data available in the literature did not cover the entire temperature range necessary for process simulation. A comparison between the predicted material property data and measured property data is made. It was found that most material properties were accurately predicted over most of the temperature range of the process. Several assumptions were made, in order to obtain a complete set of mechanical property data at high temperatures. Thermal expansion measurements for the 17-4PH alloy were conducted during heating and cooling. As a function of temperature, the thermal expansion for both the alloy and shell mold materials showed a different evolution on heating and cooling. Thus, one generic simulation was performed with thermal expansion obtained on heating, and another one was performed with thermal expansion obtained on cooling. The alloy dimensions were obtained from the numerical simulation results of the solidification, heat transfer, and deformation phenomena. As compared with experimental results, the numerical simulation results for the shrinkage factors were slightly overpredicted.

The fuzzy algorithm in the die casting mould for the application of multi-channel temperature control

NASA Astrophysics Data System (ADS)

Sun, Jin-gen; Chen, Yi; Zhang, Jia-nan

2017-01-01

Mould manufacturing is one of the most basic elements in the production chain of China. The mould manufacturing technology has become an important symbol to measure the level of a country's manufacturing industry. The die-casting mould multichannel intelligent temperature control method is studied by cooling water circulation, which uses fuzzy control to realize, aiming at solving the shortcomings of slow speed and big energy consumption during the cooling process of current die-casting mould. At present, the traditional PID control method is used to control the temperature, but it is difficult to ensure the control precision. While , the fuzzy algorithm is used to realize precise control of mould temperature in cooling process. The design is simple, fast response, strong anti-interference ability and good robustness. Simulation results show that the control method is completely feasible, which has higher control precision.

Method and apparatus for improved melt flow during continuous strip casting

DOEpatents

Follstaedt, D.W.; King, E.L.; Schneider, K.C.

1991-11-12

The continuous casting of metal strip using the melt overflow process is improved by controlling the weir conditions in the nozzle to provide a more uniform flow of molten metal across the width of the nozzle and reducing the tendency for freezing of metal along the interface with refractory surfaces. A weir design having a sloped rear wall and tapered sidewalls and critical gap controls beneath the weir has resulted in the drastic reduction in edge tearing and a significant improvement in strip uniformity. The floor of the container vessel is preferably sloped and the gap between the nozzle and the rotating substrate is critically controlled. The resulting flow patterns observed with the improved casting process have reduced thermal gradients in the bath, contained surface slag and eliminated undesirable solidification near the discharge area by increasing the flow rates at those points. 8 figures.

High-Performance All-Solid-State Na-S Battery Enabled by Casting-Annealing Technology.

PubMed

Fan, Xiulin; Yue, Jie; Han, Fudong; Chen, Ji; Deng, Tao; Zhou, Xiuquan; Hou, Singyuk; Wang, Chunsheng

2018-04-24

Room-temperature all-solid-state Na-S batteries (ASNSBs) using sulfide solid electrolytes are a promising next-generation battery technology due to the high energy, enhanced safety, and earth abundant resources of both sodium and sulfur. Currently, the sulfide electrolyte ASNSBs are fabricated by a simple cold-pressing process leaving with high residential stress. Even worse, the large volume change of S/Na 2 S during charge/discharge cycles induces additional stress, seriously weakening the less-contacted interfaces among the solid electrolyte, active materials, and the electron conductive agent that are formed in the cold-pressing process. The high and continuous increase of the interface resistance hindered its practical application. Herein, we significantly reduce the interface resistance and eliminate the residential stress in Na 2 S cathodes by fabricating Na 2 S-Na 3 PS 4 -CMK-3 nanocomposites using melting-casting followed by stress-release annealing-precipitation process. The casting-annealing process guarantees the close contact between the Na 3 PS 4 solid electrolyte and the CMK-3 mesoporous carbon in mixed ionic/electronic conductive matrix, while the in situ precipitated Na 2 S active species from the solid electrolyte during the annealing process guarantees the interfacial contact among these three subcomponents without residential stress, which greatly reduces the interfacial resistance and enhances the electrochemical performance. The in situ synthesized Na 2 S-Na 3 PS 4 -CMK-3 composite cathode delivers a stable and highly reversible capacity of 810 mAh/g at 50 mA/g for 50 cycles at 60 °C. The present casting-annealing strategy should provide opportunities for the advancement of mechanically robust and high-performance next-generation ASNSBs.

Low-cost single-crystal turbine blades, volume 2

NASA Technical Reports Server (NTRS)

Strangman, T. E.; Dennis, R. E.; Heath, B. R.

1984-01-01

The overall objectives of Project 3 were to develop the exothermic casting process to produce uncooled single-crystal (SC) HP turbine blades in MAR-M 247 and higher strength derivative alloys and to validate the materials process and components through extensive mechanical property testing, rig testing, and 200 hours of endurance engine testing. These Program objectives were achieved. The exothermic casting process was successfully developed into a low-cost nonproperietary method for producing single-crystal castings. Single-crystal MAR-M 247 and two derivatives DS alloys developed during this project, NASAIR 100 and SC Alloy 3, were fully characterized through mechanical property testing. SC MAR-M 247 shows no significant improvement in strength over directionally solidified (DS) MAR-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. Firtree testing, holography, and strain-gauge rig testing were used to determine the effects of the anisotropic characteristics of single-crystal materials. No undesirable characteristics were found. In general, the single-crystal material behaved similarly to DS MAR-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined. These blades were successfully engine-tested.

Spontaneous imbibition in fractal tortuous micro-nano pores considering dynamic contact angle and slip effect: phase portrait analysis and analytical solutions.

PubMed

Li, Caoxiong; Shen, Yinghao; Ge, Hongkui; Zhang, Yanjun; Liu, Tao

2018-03-02

Shales have abundant micro-nano pores. Meanwhile, a considerable amount of fracturing liquid is imbibed spontaneously in the hydraulic fracturing process. The spontaneous imbibition in tortuous micro-nano pores is special to shale, and dynamic contact angle and slippage are two important characteristics. In this work, we mainly investigate spontaneous imbibition considering dynamic contact angle and slip effect in fractal tortuous capillaries. We introduce phase portrait analysis to analyse the dynamic state and stability of imbibition. Moreover, analytical solutions to the imbibition equation are derived under special situations, and the solutions are verified by published data. Finally, we discuss the influences of slip length, dynamic contact angle and gravity on spontaneous imbibition. The analysis shows that phase portrait is an ideal tool for analysing spontaneous imbibition because it can evaluate the process without solving the complex governing ordinary differential equations. Moreover, dynamic contact angle and slip effect play an important role in fluid imbibition in fractal tortuous capillaries. Neglecting slip effect in micro-nano pores apparently underestimates imbibition capability, and ignoring variations in contact angle causes inaccuracy in predicting imbibition speed at the initial stage of the process. Finally, gravity is one of the factors that control the stabilisation of the imbibition process.

40 CFR 63.1541 - Applicability.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., preliminary treatment, refining and casting operations, process fugitive sources, and fugitive dust sources... the blast furnace, electric smelting furnace with a converter or reverberatory furnace, and slag fuming furnace process units. The preliminary treatment process includes the drossing kettles and dross...

40 CFR 63.1541 - Applicability.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., preliminary treatment, refining and casting operations, process fugitive sources, and fugitive dust sources... the blast furnace, electric smelting furnace with a converter or reverberatory furnace, and slag fuming furnace process units. The preliminary treatment process includes the drossing kettles and dross...

40 CFR 63.1541 - Applicability.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., preliminary treatment, refining and casting operations, process fugitive sources, and fugitive dust sources... the blast furnace, electric smelting furnace with a converter or reverberatory furnace, and slag fuming furnace process units. The preliminary treatment process includes the drossing kettles and dross...

Computation material science of structural-phase transformation in casting aluminium alloys

NASA Astrophysics Data System (ADS)

Golod, V. M.; Dobosh, L. Yu

2017-04-01

Successive stages of computer simulation the formation of the casting microstructure under non-equilibrium conditions of crystallization of multicomponent aluminum alloys are presented. On the basis of computer thermodynamics and heat transfer during solidification of macroscale shaped castings are specified the boundary conditions of local heat exchange at mesoscale modeling of non-equilibrium formation the solid phase and of the component redistribution between phases during coalescence of secondary dendrite branches. Computer analysis of structural - phase transitions based on the principle of additive physico-chemical effect of the alloy components in the process of diffusional - capillary morphological evolution of the dendrite structure and the o of local dendrite heterogeneity which stochastic nature and extent are revealed under metallographic study and modeling by the Monte Carlo method. The integrated computational materials science tools at researches of alloys are focused and implemented on analysis the multiple-factor system of casting processes and prediction of casting microstructure.

Micro-structure and Air-tightness of Squeeze Casting Motor housing for New Energy Vehicle

NASA Astrophysics Data System (ADS)

Jiang, Y. F.; Kang, Z. Q.; Jiang, W. F.; Wang, K. W.; Sha, D. L.; Li, M. L.; Sun, J.

2018-05-01

In order to improve the performance of automobile parts, the influence of squeeze casting process parameters on casting defects, material structure and air-tightness of aluminum alloy motor housing for new energy vehicle was studied. The results show that the density of the castings increases with the increase in pressure and mold temperature. With increase in pouring temperature, it increases first and then decreases. Pressure has the greatest influence on the density of the castings. Under a certain pressure, with moderate increase in casting temperature and mold temperature, the grain growth begins to increase; the dendrites become less, the new α - Al grains are spherical and granular, the micro-structure is uniform. Also, with increase in pressure, this effect is more pronounced, the air-tightness of castings improve. In conclusion, when the pressure is 110MPa, pouring temperature is 680° C, mold temperature is 280° C, pressure holding for 30s, and punch speed of 0.1m/s, there is no clear shrinkage in the casting, the structure is uniform, the qualified rate of air-tightness of production reaches 86%, and the performance is excellent.

Viscosity Meaurement Technique for Metal Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ban, Heng; Kennedy, Rory

2015-02-09

Metallic fuels have exceptional transient behavior, excellent thermal conductivity, and a more straightforward reprocessing path, which does not separate out pure plutonium from the process stream. Fabrication of fuel containing minor actinides and rare earth (RE) elements for irradiation tests, for instance, U-20Pu-3Am-2Np-1.0RE-15Zr samples at the Idaho National Laboratory, is generally done by melt casting in an inert atmosphere. For the design of a casting system and further scale up development, computational modeling of the casting process is needed to provide information on melt flow and solidification for process optimization. Therefore, there is a need for melt viscosity data, themore » most important melt property that controls the melt flow. The goal of the project was to develop a measurement technique that uses fully sealed melt sample with no Americium vapor loss to determine the viscosity of metallic melts and at temperatures relevant to the casting process. The specific objectives of the project were to: develop mathematical models to establish the principle of the measurement method, design and build a viscosity measurement prototype system based on the established principle, and calibrate the system and quantify the uncertainty range. The result of the project indicates that the oscillation cup technique is applicable for melt viscosity measurement. Detailed mathematical models of innovative sample ampoule designs were developed to not only determine melt viscosity, but also melt density under certain designs. Measurement uncertainties were analyzed and quantified. The result of this project can be used as the initial step toward the eventual goal of establishing a viscosity measurement system for radioactive melts.« less

Sequencing of Dust Filter Production Process Using Design Structure Matrix (DSM)

NASA Astrophysics Data System (ADS)

Sari, R. M.; Matondang, A. R.; Syahputri, K.; Anizar; Siregar, I.; Rizkya, I.; Ursula, C.

2018-01-01

Metal casting company produces machinery spare part for manufactures. One of the product produced is dust filter. Most of palm oil mill used this product. Since it is used in most of palm oil mill, company often have problems to address this product. One of problem is the disordered of production process. It carried out by the job sequencing. The important job that should be solved first, least implement, while less important job and could be completed later, implemented first. Design Structure Matrix (DSM) used to analyse and determine priorities in the production process. DSM analysis is sort of production process through dependency sequencing. The result of dependency sequences shows the sequence process according to the inter-process linkage considering before and after activities. Finally, it demonstrates their activities to the coupled activities for metal smelting, refining, grinding, cutting container castings, metal expenditure of molds, metal casting, coating processes, and manufacture of molds of sand.

Slip in the 2015 Mw 7.9 Gorkha and Mw 7.3 Kodari, Nepal, earthquakes revealed by seismic and geodetic data: Delayed slip in the Gorkha and slip deficit between the two earthquakes

NASA Astrophysics Data System (ADS)

Zhang, G.; Hetland, E.; Shan, X.

2017-12-01

We investigate the rupture process of the April 25, 2015 Gorkha, Nepal Mw7.9 earthquake, and its biggest aftershock on May 12, 2015, based on joint inversion of teleseismic body waves, InSAR and GPS measurements. The Gorkha earthquake propagated unilaterally to the southeast along the MFT, with coseismic slip separating into patches up-dip and down-dip of the hypocenter. Slip in the up-dip patch initially surrounded a region on the fault that did not slip. About 15 seconds after being surrounded, this region of no slip then slipped, filling in the slip deficit. The delayed slip accounts for about 20% of the moment release in the Gorkha earthquake. The inferred coseismic slip in the Kodari earthquake is localized to one patch, extending to the south and southeast from the hypocenter, and 20-30 km to the northeast of the main slip patch in the Ghorka earthquake. The maximum coseismic slip in both the Gorkha and Kodari earthquakes is about 4.5 meters.

Study on the Preparation Process and Influential Factors of Large Area Environment-friendly Molten Carbonate Fuel Cell Matrix

NASA Astrophysics Data System (ADS)

Zhang, Ruiyun; Xu, Shisen; Cheng, Jian; Wang, Hongjian; Ren, Yongqiang

2017-07-01

Low-cost and high-performance matrix materials used in mass production of molten carbonate fuel cell (MCFC) were prepared by automatic casting machine with α-LiAlO2 powder material synthesized by gel-solid method, and distilled water as solvent. The single cell was assembled for generating test, and the good performance of the matrix was verified. The paper analyzed the factors affecting aqueous tape casting matrix preparation, such as solvent content, dispersant content, milling time, blade height and casting machine running speed, providing a solid basis for the mass production of large area environment-friendly matrix used in molten carbonate fuel cell.

Fracture Analysis of Cast Steel Sling

NASA Astrophysics Data System (ADS)

Li, Xinghui

2018-02-01

The fracture reasons of ZG270-500 cast steel sling are analyzed through such means as macroscopic morphology analysis, chemical composition analysis, and microscopic metallography analysis. Results: coarse Widmanstatten structure and casting defects occurring in casting and subsequent heat treatment process reduce the strength, plasticity and toughness of the steel, which is the main reason of brittle fracture of the sling during work, and corresponding improvement suggestions are proposed herein.

The Impact of Frictional Healing on Stick-Slip Recurrence Interval and Stress Drop: Implications for Earthquake Scaling

NASA Astrophysics Data System (ADS)

Im, Kyungjae; Elsworth, Derek; Marone, Chris; Leeman, John

2017-12-01

Interseismic frictional healing is an essential process in the seismic cycle. Observations of both natural and laboratory earthquakes demonstrate that the magnitude of stress drop scales with the logarithm of recurrence time, which is a cornerstone of the rate and state friction (RSF) laws. However, the origin of this log linear behavior and short time "cutoff" for small recurrence intervals remains poorly understood. Here we use RSF laws to demonstrate that the back-projected time of null-healing intrinsically scales with the initial frictional state θi. We explore this behavior and its implications for (1) the short-term cutoff time of frictional healing and (2) the connection between healing rates derived from stick-slip sliding versus slide-hold-slide tests. We use a novel, continuous solution of RSF for a one-dimensional spring-slider system with inertia. The numerical solution continuously traces frictional state evolution (and healing) and shows that stick-slip cutoff time also scales with frictional state at the conclusion of the dynamic slip process θi (=Dc/Vpeak). This numerical investigation on the origins of stick-slip response is verified by comparing laboratory data for a range of peak slip velocities. Slower slip motions yield lesser magnitude of friction drop at a given time due to higher frictional state at the end of each slip event. Our results provide insight on the origin of log linear stick-slip evolution and suggest an approach to estimating the critical slip distance on faults that exhibit gradual accelerations, such as for slow earthquakes.

Parallel volume ray-casting for unstructured-grid data on distributed-memory architectures

NASA Technical Reports Server (NTRS)

Ma, Kwan-Liu

1995-01-01

As computing technology continues to advance, computational modeling of scientific and engineering problems produces data of increasing complexity: large in size and unstructured in shape. Volume visualization of such data is a challenging problem. This paper proposes a distributed parallel solution that makes ray-casting volume rendering of unstructured-grid data practical. Both the data and the rendering process are distributed among processors. At each processor, ray-casting of local data is performed independent of the other processors. The global image composing processes, which require inter-processor communication, are overlapped with the local ray-casting processes to achieve maximum parallel efficiency. This algorithm differs from previous ones in four ways: it is completely distributed, less view-dependent, reasonably scalable, and flexible. Without using dynamic load balancing, test results on the Intel Paragon using from two to 128 processors show, on average, about 60% parallel efficiency.

On Macrosegregation

NASA Astrophysics Data System (ADS)

Ludwig, Andreas; Wu, Menghuai; Kharicha, Abdellah

2015-11-01

Macrosegregations, namely compositional inhomogeneities at a scale much larger than the microstructure, are typically classified according to their metallurgical appearance. In ingot castings, they are known as `A' and `V' segregation, negative cone segregation, and positive secondary pipe segregation. There exists `inverse' segregation at casting surfaces and `centerline' segregation in continuously cast slabs and blooms. Macrosegregation forms if a relative motion between the solute-enriched or -depleted melt and dendritic solid structures occurs. It is known that there are four basic mechanisms for the occurrence of macrosegregation. In the recent years, the numerical description of the combination of these mechanisms has become possible and so a tool has emerged which can be effectively used to get a deeper understanding into the process details which are responsible for the formation of the above-mentioned different macrosegregation appearances. Based on the most sophisticated numerical models, we consequently associate the four basic formation mechanisms with the physical phenomena happening during (i) DC-casting of copper-based alloys, (ii) DC-casting of aluminum-based alloys, (iii) continuous casting of steel, and (iv) ingot casting of steel.

The Simulation of Magnesium Wheel Low Pressure Die Casting Based on PAM-CAST™

NASA Astrophysics Data System (ADS)

Peng, Yinghong; Wang, Yingchun; Li, Dayong; Zeng, Xiaoqin

2004-06-01

Magnesium is the lightest metal commonly used in engineering, with various excellent characteristics such as high strength and electromagnetic interference shielding capability. Particularly, the usage of magnesium in automotive industry can meet better the need to reduce fuel consumption and CO2 emissions. Nowadays, most current magnesium components in automobiles are made by die casting. In this paper, commercial software for die casting, PAM-CAST™, was utilized to simulate the low pressure die casting process of magnesium wheel. Through calculating temperature field and velocity field during filling and solidification stages, the evolution of temperature distribution and liquid fraction was analyzed. Then, the potential defects including the gas entrapments in the middle of the spokes, shrinkages between the rim and the spokes were forecasted. The analytical results revealed that the mold geometry and die casting parameters should be improved in order to get the sound magnesium wheel. The reasons leading to these defects were also analyzed and the solutions to eliminate them were put forward. Furthermore, through reducing the pouring velocity, the air gas entrapments and partial shrinkages were eliminated effectively.

Materials for Advanced Ultrasupercritical Steam Turbines Task 4: Cast Superalloy Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thangirala, Mani

The Steam Turbine critical stationary structural components are high integrity Large Shell and Valve Casing heavy section Castings, containing high temperature steam under high pressures. Hence to support the development of advanced materials technology for use in an AUSC steam turbine capable of operating with steam conditions of 760°C (1400°F) and 35 Mpa (5000 psia), Casting alloy selection and evaluation of mechanical, metallurgical properties and castability with robust manufacturing methods are mandated. Alloy down select from Phase 1 based on producability criteria and creep rupture properties tested by NETL-Albany and ORNL directed the consortium to investigate cast properties of Haynesmore » 282 and Haynes 263. The goals of Task 4 in Phase 2 are to understand a broader range of mechanical properties, the impact of manufacturing variables on those properties. Scale up the size of heats to production levels to facilitate the understanding of the impact of heat and component weight, on metallurgical and mechanical behavior. GE Power & Water Materials and Processes Engineering for the Phase 2, Task 4.0 Castings work, systematically designed and executed casting material property evaluation, multiple test programs. Starting from 15 lbs. cylinder castings to world’s first 17,000 lbs. poured weight, heavy section large steam turbine partial valve Haynes 282 super alloy casting. This has demonstrated scalability of the material for steam Turbine applications. Activities under Task 4.0, Investigated and characterized various mechanical properties of Cast Haynes 282 and Cast Nimonic 263. The development stages involved were: 1) Small Cast Evaluation: 4 inch diam. Haynes 282 and Nimonic 263 Cylinders. This provided effects of liquidus super heat range and first baseline mechanical data on cast versions of conventional vacuum re-melted and forged Ni based super alloys. 2) Step block castings of 300 lbs. and 600 lbs. Haynes 282 from 2 foundry heats were evaluated which demonstrated the importance of proper heat treat cycles for Homogenization, and Solutionizing parameters selection and implementation. 3) Step blocks casting of Nimonic 263: Carried out casting solidification simulation analysis, NDT inspection methods evaluation, detailed test matrix for Chemical, Tensile, LCF, stress rupture, CVN impact, hardness and J1C Fracture toughness section sensitivity data and were reported. 4) Centrifugal Casting of Haynes 282, weighing 1400 lbs. with hybrid mold (half Graphite and half Chromite sand) mold assembly was cast using compressor casing production tooling. This test provided Mold cooling rates influence on centrifugally cast microstructure and mechanical properties. Graphite mold section out performs sand mold across all temperatures for 0.2% YS; %Elongation, %RA, UTS at 1400°F. Both Stress-LMP and conditional Fracture toughness plots data were in the scatter band of the wrought alloy. 5) Fundamental Studies on Cooling rates and SDAS test program. Evaluated the influence of 6 mold materials Silica, Chromite, Alumina, Silica with Indirect Chills, Zircon and Graphite on casting solidification cooling rates. Actual Casting cooling rates through Liquidus to Solidus phase transition were measured with 3 different locations based thermocouples placed in each mold. Compared with solidification simulation cooling rates and measurement of SDAS, microstructure features were reported. The test results provided engineered casting potential methods, applicable for heavy section Haynes 282 castings for optimal properties, with foundry process methods and tools. 6) Large casting of Haynes 282 Drawings and Engineering FEM models and supplemental requirements with applicable specifications were provided to suppliers for the steam turbine proto type feature valve casing casting. Molding, melting and casting pouring completed per approved Manufacturing Process Plan during 2014 Q4. The partial valve casing was successfully cast after casting methods were validated with solidification simulation analysis and the casting met NDT inspection and acceptance criteria. Heat treated and sectioned to extract trepan samples at different locations comparing with cast on coupons test data. Material properties requisite for design, such as tensile, creep/rupture, LCF, Fracture Toughness, Charpy V-notch chemical analysis testing were carried out. The test results will be presented in the final report. The typical Haynes 282 large size Steam Turbine production casting from Order to Delivery foundry schedule with the activity break up is shown in Figures 107 and 108. • From Purchase Order placement to Casting pouring ~ 26 weeks. 1. Sales and commercial review 3 2. Engineering Drawings/models review 4 3. Pattern and core box manufacturing 6 4. Casting process engineering review 4 5. FEM and solidification simulation analysis 4 6. Gating & Feeder Attachments, Ceramic tiling 2 7. Molding and coremaking production scheduling 6 8. Melting planning and schedule 3 9. Pouring, cooling and shake out 2 • From Pouring to casting Delivery ~ 29 weeks 10. Shot blast and riser cutting, gates removal 3 11. Homogenizing , solutionizing HT furnace prep 4 12. Grinding, Fettling 2 13. Aging HT Cycle, cooling 2 14. VT and LPT NDT inspections 2 15. Radiographic inspection 4 16. Mechanical testing, Chemical analysis test certs 4 17. Casting weld repair upgrades and Aging PWHT 4 18. NDT after weld repairs and casting upgrades 3 19. Casting Final Inspection and test certifications 3 20. Package and delivery 2 Hence the Total Lead time from P.O to Casting delivery is approximately 55 weeks. The Task 4.2 and Task 4.3 activities and reporting completed.« less

One-step Tape Casting of Composites via Slurry on Fiber

NASA Technical Reports Server (NTRS)

deGroh, Henry C., III

2001-01-01

A process by which metal matrix composites can be made was presented. The process involves putting a powder slurry on fibers to make a precursor green tape. These green tapes are cut, stacked and hot pressed to form the fully dense composite. A computer program was presented which enables complete quantification and control of the process. Once some easily obtained properties of the slurry and its behavior are determined (such as the shrinkage from the wet to green state, and the density of the green tape) modification of the fiber spacing and blade height give the maker precise control of fiber volume fraction, and fiber architecture in the composite. The process was shown to be accurate and flexible through the production of a wide variety of volume fraction fiber composites made from a wide variety of fibers and powders. The most time consuming step of the tape casting process (other than hot pressing) was winding the fiber on the drum. The tape casting techniques developed resulted in high quality metal matrix composites, with ultimate tensile strength in the range of 215 ksi (1477 MPa), a strain at failure of 1.15 percent, and in fatigue at room temperature 0 to 120 ksi, n = 0.3 Hz, a 4-ply Ti-24Al-11Nb/SCS-6, 32 vol% fiber tape cast composite lasted 202,205 cycles with a maximum strain on the 100th cycle of 0.43 percent.

Elaboration of Alumina-Zirconia Composites: Role of the Zirconia Content on the Microstructure and Mechanical Properties

PubMed Central

Naglieri, Valentina; Palmero, Paola; Montanaro, Laura; Chevalier, Jérôme

2013-01-01

Alumina-zirconia (AZ) composites are attractive structural materials, which combine the high hardness and Young’s modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In this study, AZ composites containing different amounts of zirconia (in the range 5–20 vol %) were prepared by a wet chemical method, consisting on the surface coating of alumina powders by mixing them with zirconium salt aqueous solutions. After spray-drying, powders were calcined at 600 °C for 1 h. Green bodies were then prepared by two methods: uniaxial pressing of spray-dried granules and slip casting of slurries, obtained by re-dispersing the spray dried granulates. After pressureless sintering at 1500 °C for 1 h, the slip cast samples gave rise to fully dense materials, characterized by a quite homogeneous distribution of ZrO2 grains in the alumina matrix. The microstructure, phase composition, tetragonal to monoclinic transformation behavior and mechanical properties were investigated and are here discussed as a function of the ZrO2 content. The material containing 10 vol % ZrO2 presented a relevant hardness and exhibited the maximum value of KI0, mainly imputable to the t → m transformation at the crack tip. PMID:28809262

The casting of semi-permeable membranes in a microgravity environment

NASA Technical Reports Server (NTRS)

Vera, I.

1986-01-01

The experiment is to study polymeric membranes. Presently, semipermeable membranes are being manufactured from several different kinds of polymers all over the world and specific applications have been identified in fluid separation processes such as reverse osmosis, ultrafiltration and electrodialysis. Although, the ultrastructure of asymmetric and composite membranes have been under intensive study, still there are many questions about the factors affecting this structure and their degree of correlation. Nevertheless, there is indication that the entire morphological structure of polymeric membranes could be affected by the difference in specific gravity between the cast solution and the coagulation liquid normally used in the membranes preparation process. The casting of semipermeable membranes in space might help to identify the effect of gravity upon the structure of these membranes. It is important to recognize that the casting process involves changes of state and that in a microgravity environment, there will be a reduction on buoyancy-driven natural convection and density gradients.

Predictive Capabilities of Multiphysics and Multiscale Models in Modeling Solidification of Steel Ingots and DC Casting of Aluminum

NASA Astrophysics Data System (ADS)

Combeau, Hervé; Založnik, Miha; Bedel, Marie

2016-08-01

Prediction of solidification defects, such as macrosegregation and inhomogeneous microstructures, constitutes a key issue for industry. The development of models of casting processes needs to account for several imbricated length scales and different physical phenomena. For example, the kinetics of the growth of microstructures needs to be coupled with the multiphase flow at the process scale. We introduce such a state-of-the-art model and outline its principles. We present the most recent applications of the model to casting of a heavy steel ingot and to direct chill casting of a large Al alloy sheet ingot. Their ability to help in the understanding of complex phenomena, such as the competition between nucleation and growth of grains in the presence of convection of the liquid and of grain motion is shown, and its predictive capabilities are discussed. Key issues for future developments and research are addressed.

Statically determined slip-line field solution for the axial forming force estimation in the radial-axial ring rolling process

NASA Astrophysics Data System (ADS)

Quagliato, Luca; Berti, Guido A.

2017-10-01

In this paper, a statically determined slip-line solution algorithm is proposed for the calculation of the axial forming force in the radial-axial ring rolling process of flat rings. The developed solution is implemented in an Excel spreadsheet for the construction of the slip-line field and the calculation of the pressure factor to be used in the force model. The comparison between analytical solution and authors' FE simulation allows stating that the developed model supersedes the previous literature ones and proves the reliability of the proposed approach.

Influence of movement regime of stick-slip process on the size distribution of accompanying acoustic emission characteristics

NASA Astrophysics Data System (ADS)

Matcharashvili, Teimuraz; Chelidze, Tamaz; Zhukova, Natalia; Mepharidze, Ekaterine; Sborshchikov, Alexander

2010-05-01

Many scientific works on dynamics of earthquake generation are devoted to qualitative and quantitative reproduction of behavior of seismic faults. Number of theoretical, numerical or physical models are already designed for this purpose. Main assumption of these works is that the correct model must be capable to reproduce power law type relation for event sizes with magnitudes greater than or equal to a some threshold value, similar to Gutenberg-Richter (GR) law for the size distribution of earthquakes. To model behavior of a seismic faults in laboratory conditions spring-block experimental systems are often used. They enable to generate stick-slip movement, intermittent behavior occurring when two solids in contact slide relative to each other driven at a constant velocity. Wide interest to such spring-block models is caused by the fact that stick-slip is recognized as a basic process underlying earthquakes generation along pre-existing faults. It is worth to mention, that in stick slip experiments reproduction of power law, in slip events size distribution, with b values close or equal to the one found for natural seismicity is possible. Stick-slip process observed in these experimental models is accompanied by a transient elastic waves propagation generated during the rapid release of stress energy in spring-block system. Oscillations of stress energy can be detected as a characteristic acoustic emission (AE). Accompanying stick slip AE is the subject of intense investigation, but many aspects of this process are still unclear. In the present research we aimed to investigate dynamics of stick slip AE in order to find whether its distributional properties obey power law. Experiments have been carried out on spring-block system consisting of fixed and sliding plates of roughly finished basalt samples. The sliding block was driven with a constant velocity. Experiments have been carried out for five different stiffness of pulling spring. Thus five different regimes of stick slip movement has been maintained. The AE accompanying the elementary slip events of stick-slip process were recorded on a PC sound card. The sensor for the AE was a lead circonate-titanate with a natural frequency of 100 KHz. In order to ensure standard conditions in each experiment, sliding surfaces were sanded up by sandpaper and cleaned of a dust. AE data analysis consisted of signal conditioning, filtering, and correct wave trains separation. Onset time of AE was determined at a minimun of Akaike Information Criterion. Afterwards time series of AE characteristics such as: recurrence times between consecutive AE bursts as well as time intervals between their maximums, duration of AE bursts, energy and power of AE, max by modulus of AE wave train amplitudes, etc. have been compiled. Cumulative probability distributions for all these data sets have been constructed and tested on the subject of GR type power law relation. It was found that characteristics of AE of stick slip process are strongly depending on the movement regime. Number of registered AE essentially increased for stiffer spring. At the same time recurrence times and emitted AE energy decreases. Power law type relation have not been observed for all AE characteristics and not for all considered regimes of movement. Power law relation, close to observed for real seismicity, was found for power of AE time series at stiffer springs. It is interesting that recurrence times between maximums of consecutive AE bursts and duration of AE bursts, reveal b in the range of 0.6-1.65. These results point that experimental conditions of stick slip process including movement regimes should be selected with care to ensure similarity between model and natural seismicity distributional characteristics.

Distribution of stress drop, stiffness, and fracture energy over earthquake rupture zones

USGS Publications Warehouse

Fletcher, Joe B.; McGarr, A.

2006-01-01

Using information provided by slip models and the methodology of McGarr and Fletcher (2002), we map static stress drop, stiffness (k = ????/u, where ???? is static stress drop and u is slip), and fracture energy over the slip surface to investigate the earthquake rupture process and energy budget. For the 1994 M6.7 Northridge, 1992 M7.3 Landers, and 1995 M6.9 Kobe earthquakes, the distributions of static stress drop show strong heterogeneity, emphasizing the importance of asperities in the rupture process. Average values of static stress drop are 17, 11, and 4 Mpa for Northridge, Landers, and Kobe, respectively. These values are substantially higher than estimates based on simple crack models, suggesting that the failure process involves the rupture of asperities within the larger fault zone. Stress drop as a function of depth for the Northridge and Landers earthquakes suggests that stress drops are limited by crustal strength. For these two earthquakes, regions of high slip are surrounded by high values of stiffness. Particularly for the Northridge earthquake, the prominent patch of high slip in the central part of the fault is bordered by a ring of high stiffness and is consistent with expectations based on the failure of an asperity loaded at its edge due to exterior slip. Stiffness within an asperity is inversely related to its dimensions. Estimates of fracture energy, based on static stress drop, slip, and rupture speed, were used to investigate the nature of slip weakening at four locations near the hypocenter of the Kobe earthquake for comparison with independent results based on a dynamic model of this earthquake. One subfault updip and to the NE of the hypocenter has a fracture energy of 1.1 MJ/m2 and a slip-weakening distance, Dc, of 0.66 m. Right triangles, whose base and height are Dc and the dynamic stress drop, respectively, approximately overlie the slip-dependent stress given by Ide and Takeo (1997) for the same locations near the hypocenter. The total fracture energy for the Kobe earthquake, 3.7 ?? 1014 J, is about the same as the seismic energy (Ea = 3.2 ?? 1014 J.

Energy Saving Melting and Revert Reduction Technology: Innovative Semi-Solid Metal (SSM) Processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diran Apelian

2012-08-15

Semi-solid metal (SSM) processing has emerged as an attractive method for near-net-shape manufacturing due to the distinct advantages it holds over conventional near-net-shape forming technologies. These advantages include lower cycle time, increased die life, reduced porosity, reduced solidification shrinkage, improved mechanical properties, etc. SSM processing techniques can not only produce the complex dimensional details (e.g. thin-walled sections) associated with conventional high-pressure die castings, but also can produce high integrity castings currently attainable only with squeeze and low-pressure permanent mold casting processes. There are two primary semi-solid processing routes, (a) thixocasting and (b) rheocasting. In the thixocasting route, one starts frommore » a non-dendritic solid precursor material that is specially prepared by a primary aluminum manufacturer, using continuous casting methods. Upon reheating this material into the mushy (a.k.a. "two-phase") zone, a thixotropic slurry is formed, which becomes the feed for the casting operation. In the rheocasting route (a.k.a. "slurry-on-demand" or "SoD"), one starts from the liquid state, and the thixotropic slurry is formed directly from the melt via careful thermal management of the system; the slurry is subsequently fed into the die cavity. Of these two routes, rheocasting is favored in that there is no premium added to the billet cost, and the scrap recycling issues are alleviated. The CRP (Trade Marked) is a process where the molten metal flows through a reactor prior to casting. The role of the reactor is to ensure that copious nucleation takes place and that the nuclei are well distributed throughout the system prior to entering the casting cavity. The CRP (Trade Marked) has been successfully applied in hyper-eutectic Al-Si alloys (i.e., 390 alloy) where two liquids of equal or different compositions and temperatures are mixed in the reactor and creating a SSM slurry. The process has been mostly used for hypo-eutectic Al-Si alloys (i.e., 356, 357, etc.) where a single melt passes through the reactor. In addition, the CRP (Trade Marked) was designed to be flexible for thixocasting or rheocasting applications as well as batch or continuous casting. Variable heat extraction rates can be obtained by controlling either the superheat of the melt, the temperature of the channel system, or the temperature of the reactor. This program had four main objectives all of which were focused on a mechanistic understanding of the process in order to be able to scale it up, to develop it into a robust process,and for SSM processing to be commercially used.« less

Microstructure, Tensile and Creep Properties of Ta20Nb20Hf20Zr20Ti20 High Entropy Alloy

PubMed Central

Larianovsky, Natalya; Katz-Demyanetz, Alexander; Eshed, Eyal; Regev, Michael

2017-01-01

This paper examines the microstructure and mechanical properties of Ta20Nb20Hf20Zr20Ti20. Two casting processes, namely, gravity casting and suction-assisted casting, were applied, both followed by Hot Isostatic Pressing (HIP). The aim of the current study was to investigate the creep and tensile properties of the material, since the literature review revealed no data whatsoever regarding these properties. The main findings are that the HIP process is responsible for the appearance of a Hexagonal Close Packed (HCP) phase that is dispersed differently in these two castings. The HIP process also led to a considerable increase in the mechanical properties of both materials under compression, with values found to be higher than those reported in the literature. Contrary to the compression properties, both materials were found to be highly brittle under tension, either during room temperature tension tests or creep tests conducted at 282 °C. Fractography yielded brittle fracture without any evidence of plastic deformation prior to fracture. PMID:28773245

Modified Surface Having Low Adhesion Properties to Mitigate Insect Residue Adhesion

NASA Technical Reports Server (NTRS)

Wohl, Christopher J., Jr. (Inventor); Smith, Joseph G., Jr. (Inventor); Siochi, Emilie J. (Inventor); Penner, Ronald K. (Inventor)

2016-01-01

A process to modify a surface to provide reduced adhesion surface properties to mitigate insect residue adhesion. The surface may include the surface of an article including an aircraft, an automobile, a marine vessel, all-terrain vehicle, wind turbine, helmet, etc. The process includes topographically and chemically modifying the surface by applying a coating comprising a particulate matter, or by applying a coating and also topographically modifying the surface by various methods, including but not limited to, lithographic patterning, laser ablation and chemical etching, physical vapor phase deposition, chemical vapor phase deposition, crystal growth, electrochemical deposition, spin casting, and film casting.

Argon Bubble Transport and Capture in Continuous Casting with an External Magnetic Field Using GPU-Based Large Eddy Simulations

NASA Astrophysics Data System (ADS)

Jin, Kai

Continuous casting produces over 95% of steel in the world today, hence even small improvements to this important industrial process can have large economic impact. In the continuous casting of steel process, argon gas is usually injected at the slide gate or stopper rod to prevent clogging, but entrapped bubbles may cause defects in the final product. Many defects in this process are related to the transient fluid flow in the mold region of the caster. Electromagnetic braking (EMBr) device is often used at high casting speed to modify the mold flow, reduce the surface velocity and fluctuation. This work studies the physics in continuous casting process including effects of EMBr on the motion of fluid flow in the mold region, and transport and capture of bubbles in the solidification processes. A computational effective Reynolds-averaged Navier-Stokes (RANS) model and a high fidelity Large Eddy Simulation (LES) model are used to understand the motion of the molten steel flow. A general purpose multi-GPU Navier-Stokes solver, CUFLOW, is developed. A Coherent-Structure Smagorinsky LES model is implemented to model the turbulent flow. A two-way coupled Lagrangian particle tracking model is added to track the motion of argon bubbles. A particle/bubble capture model based on force balance at dendrite tips is validated and used to study the capture of argon bubbles by the solidifying steel shell. To investigate the effects of EMBr on the turbulent molten steel flow and bubble transport, an electrical potential method is implemented to solve the magnetohydrodynamics equations. Volume of Fluid (VOF) simulations are carried out to understand the additional resistance force on moving argon bubbles caused by adding transverse magnetic field. A modified drag coefficient is extrapolated from the results and used in the two-way coupled Eulerian-Lagrangian model to predict the argon bubble transport in a caster with EMBr. A hook capture model is developed to understand the effects of hooks on argon bubble capture.

Creep and slip: Seismic precursors to the Nuugaatsiaq landslide (Greenland)

NASA Astrophysics Data System (ADS)

Poli, Piero

2017-09-01

Precursory signals to material's failure are predicted by numerical models and observed in laboratory experiments or using field data. These precursory signals are a marker of slip acceleration on weak regions, such as crustal faults. Observation of these precursory signals of catastrophic natural events, such as earthquakes and landslides, is necessary for improving our knowledge about the physics of the nucleation process. Furthermore, observing such precursory signals may help to forecast these catastrophic events or reduce their hazard. I report here the observation of seismic precursors to the Nuugaatsiaq landslide in Greenland. Time evolution of the detected precursors implies that an aseismic slip event is taking place for hours before the landslide, with an exponential increase of slip velocity. Furthermore, time evolution of the precursory signals' amplitude sheds light on the evolution of the fault physics during the nucleation process.

HFIR Fuel Casting Support

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imhoff, Seth D.; Gibbs, Paul Jacob; Solis, Eunice Martinez

Process exploration for fuel production for the High Flux Isotope Reactor (HFIR) using cast LEU-10wt.%Mo as an initial processing step has just begun. This project represents the first trials concerned with casting design and quality. The studies carried out over the course of this year and information contained in this report address the initial mold development to be used as a starting point for future operations. In broad terms, the final billet design is that of a solid rolling blank with an irregular octagonal cross section. The work covered here is a comprehensive view of the initial attempts to producemore » a sound casting. This report covers the efforts to simulate, predict, cast, inspect, and revise the initial mold design.« less

Investigation on the Effect of Mold Constraints and Cooling Rate on Residual Stress During the Sand-Casting Process of 1086 Steel by Employing a Thermomechanical Model

NASA Astrophysics Data System (ADS)

Baghani, Amir; Davami, Parviz; Varahram, Naser; Shabani, Mohsen Ostad

2014-06-01

In this study, the effects of mold constraints and cooling rate on residual stress were analyzed during the shaped casting process. For this purpose, an H-shaped sample was designed in which the contraction of its middle portion is highly restricted by the mold during the cooling process. The effects of an increasing cooling rate combined with mold constraints were analyzed by reducing the thickness of the middle portion in the second sample. A three-dimensional coupled temperature-displacement analysis was performed in finite-element code ABAQUS to simulate residual stress distribution, and then numerical results were verified by the hole-drilling strain-gauge method. It was concluded that the mold constraints have a greater effect on the values of residual stress than the cooling rate (thin section) in steel sand casting. Increasing the cooling rate would increase the amount of residual stress, only in the presence of mold constraints. It is also suggested that employing the elastic-plastic stress model for the sand mold will satisfy the experimental results and avoid exaggerated values of residual stress in simulation.

Integrally cored ceramic investment casting mold fabricated by ceramic stereolithography

NASA Astrophysics Data System (ADS)

Bae, Chang-Jun

Superalloy airfoils are produced by investment casting (IC), which uses ceramic cores and wax patterns with ceramic shell molds. Hollow cored superalloy airfoils in a gas turbine engine are an example of complex IC parts. The complex internal hollow cavities of the airfoil are designed to conduct cooling air through one or more passageways. These complex internal passageways have been fabricated by a lost wax process requiring several processing steps; core preparation, injection molding for wax pattern, and dipping process for ceramic shell molds. Several steps generate problems such as high cost and decreased accuracy of the ceramic mold. For example, costly tooling and production delay are required to produce mold dies for complex cores and wax patterns used in injection molding, resulting in a big obstacle for prototypes and smaller production runs. Rather than using separate cores, patterns, and shell molds, it would be advantageous to directly produce a mold that has the casting cavity and the ceramic core by one process. Ceramic stereolithography (CerSLA) can be used to directly fabricate the integrally cored ceramic casting mold (ICCM). CerSLA builds ceramic green objects from CAD files from many thin liquid layers of powder in monomer, which are solidified by polymerization with a UV laser, thereby "writing" the design for each slice. This dissertation addresses the integrally cored casting ceramic mold (ICCM), the ceramic core with a ceramic mold shell in a single patternless construction, fabricated by ceramic stereolithography (CerSLA). CerSLA is considered as an alternative method to replace lost wax processes, for small production runs or designs too complex for conventional cores and patterns. The main topic is the development of methods to successfully fabricate an ICCM by CerSLA from refractory silica, as well as related issues. The related issues are the segregation of coarse fused silica powders in a layer, the degree of segregation parameter to prevent segregation, and sintering and cristobalite transformation in fused silica compacts.

The Hills are Alive: Dynamic Ridges and Valleys in a Strike-Slip Environment

NASA Astrophysics Data System (ADS)

Duvall, A. R.; Tucker, G. E.

2014-12-01

Strike-slip fault zones have long been known for characteristic landforms such as offset and deflected rivers, linear strike-parallel valleys, and shutter ridges. Despite their common presence, questions remain about the mechanics of how these landforms arise or how their form varies as a function of slip rate, geomorphic process, or material properties. We know even less about what happens far from the fault, in drainage basin headwaters, as a result of strike-slip motion. Here we explore the effects of horizontal fault slip rate, bedrock erodibility, and hillslope diffusivity on river catchments that drain across an active strike-slip fault using the CHILD landscape evolution model. Model calculations demonstrate that lateral fault motion induces a permanent state of landscape disequilibrium brought about by fault offset-generated river lengthening alternating with abrupt shortening due to stream capture. This cycle of shifting drainage patterns and base level change continues until fault motion ceases thus creating a perpetual state of transience unique to strike-slip systems. Our models also make the surprising prediction that, in some cases, hillslope ridges oriented perpendicular to the fault migrate laterally in conjunction with fault motion. Ridge migration happens when slip rate is slow enough and/or diffusion and river incision are fast enough that the hillslopes can respond to the disequilibrium brought about by strike-slip motion. In models with faster slip rates, stronger rocks or less-diffusive hillslopes, ridge mobility is limited or arrested despite the fact that the process of river lengthening and capture continues. Fast-slip cases also develop prominent steep fault-facing hillslope facets proximal to the fault valley and along-strike topographic profiles with reduced local relief between ridges and valleys. Our results demonstrate the dynamic nature of strike-slip landscapes that vary systematically with a ratio of bedrock erodibility (K) and hillslope diffusivity (D) to the rate of horizontal advection of topography (v). These results also reveal a potential set of recognizable geomorphic signatures within strike-slip systems that should be looked to as indicators of fault activity and/or material properties.

Method and apparatus for casting conductive and semiconductive materials

DOEpatents

Ciszek, Theodore F.

1986-01-01

A method and apparatus is disclosed for casting conductive and semiconduce materials. The apparatus includes a plurality of conductive members arranged to define a container-like area having a desired cross-sectional shape. A portion or all of the conductive or semiconductive material which is to be cast is introduced into the container-like area. A means is provided for inducing the flow of an electrical current in each of the conductive members, which currents act collectively to induce a current flow in the material. The induced current flow through the conductive members is in a direction substantially opposite to the induced current flow in the material so that the material is repelled from the conductive members during the casting process.

Designing a combined casting mold for manufacture of a gasoline centrifugal pump body using CAD/CAM-systems

NASA Astrophysics Data System (ADS)

Galin, N. E.; Ogol, I. I.; Chervach, Yu B.; Dammer, V. Kh; Ru, Jia Hong

2017-02-01

The present paper examines designing of a combined casting mold for manufacture of a gasoline centrifugal pump body. The paper offers technological solutions for obtaining high quality castings at the testing stage of the finished mold. The paper is intended for practical use and prepared by order of JSC ‘Tomsk Electrical Engineering Plant’ using software and equipment of the department ‘Technologies of Computer-Aided Machinery Manufacturing’ of the Tomsk Polytechnic University (TPU) under the economic contract within state import substitution program. In preparing the paper, CAD/CAM-systems KOMPAS-3D and PowerMILL were used. In 2015, the designed casting mold was introduced into the production process at JSC ‘Tomsk Electrical Engineering Plant’.

Development of a CFD code for casting simulation

NASA Technical Reports Server (NTRS)

Murph, Jesse E.

1993-01-01

Because of high rejection rates for large structural castings (e.g., the Space Shuttle Main Engine Alternate Turbopump Design Program), a reliable casting simulation computer code is very desirable. This code would reduce both the development time and life cycle costs by allowing accurate modeling of the entire casting process. While this code could be used for other types of castings, the most significant reductions of time and cost would probably be realized in complex investment castings, where any reduction in the number of development castings would be of significant benefit. The casting process is conveniently divided into three distinct phases: (1) mold filling, where the melt is poured or forced into the mold cavity; (2) solidification, where the melt undergoes a phase change to the solid state; and (3) cool down, where the solidified part continues to cool to ambient conditions. While these phases may appear to be separate and distinct, temporal overlaps do exist between phases (e.g., local solidification occurring during mold filling), and some phenomenological events are affected by others (e.g., residual stresses depend on solidification and cooling rates). Therefore, a reliable code must accurately model all three phases and the interactions between each. While many codes have been developed (to various stages of complexity) to model the solidification and cool down phases, only a few codes have been developed to model mold filling.

Development of an expert system for the simulation model for casting metal substructure of a metal-ceramic crown design.

PubMed

Matin, Ivan; Hadzistevic, Miodrag; Vukelic, Djordje; Potran, Michal; Brajlih, Tomaz

2017-07-01

Nowadays, the integrated CAD/CAE systems are favored solutions for the design of simulation models for casting metal substructures of metal-ceramic crowns. The worldwide authors have used different approaches to solve the problems using an expert system. Despite substantial research progress in the design of experts systems for the simulation model design and manufacturing have insufficiently considered the specifics of casting in dentistry, especially the need for further CAD, RE, CAE for the estimation of casting parameters and the control of the casting machine. The novel expert system performs the following: CAD modeling of the simulation model for casting, fast modeling of gate design, CAD eligibility and cast ability check of the model, estimation and running of the program code for the casting machine, as well as manufacturing time reduction of the metal substructure. The authors propose an integration method using common data model approach, blackboard architecture, rule-based reasoning and iterative redesign method. Arithmetic mean roughness values was determinated with constant Gauss low-pass filter (cut-off length of 2.5mm) according to ISO 4287 using Mahr MARSURF PS1. Dimensional deviation between the designed model and manufactured cast was determined using the coordinate measuring machine Zeiss Contura G2 and GOM Inspect software. The ES allows for obtaining the castings derived roughness grade number N7. The dimensional deviation between the simulation model of the metal substructure and the manufactured cast is 0.018mm. The arithmetic mean roughness values measured on the casting substructure are from 1.935µm to 2.778µm. The realized developed expert system with the integrated database is fully applicable for the observed hardware and software. Values of the arithmetic mean roughness and dimensional deviation indicate that casting substructures are surface quality, which is more than enough and useful for direct porcelain veneering. The manufacture of the substructure shows that the proposed ES allows the improvement of the design process while reducing the manufacturing time. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimental Exploration of Metal Cable as Reinforcement in 3D Printed Concrete

PubMed Central

Ahmed, Zeeshan Y.; Jutinov, Evgeniy R.; Salet, Theo A. M.

2017-01-01

The Material Deposition Method (MDM) is enjoying increasing attention as an additive method to create concrete mortar structures characterised by a high degree of form-freedom, a lack of geometrical repetition, and automated construction. Several small-scale structures have been realised around the world, or are under preparation. However, the nature of this construction method is unsuitable for conventional reinforcement methods to achieve ductile failure behaviour. Sometimes, this is solved by combining printing with conventional casting and reinforcing techniques. This study, however, explores an alternative strategy, namely to directly entrain a metal cable in the concrete filament during printing to serve as reinforcement. A device is introduced to apply the reinforcement. Several options for online reinforcement media are compared for printability. Considerations specific to the manufacturing process are discussed. Subsequently, pull-out tests on cast and printed specimens provide an initial characterisation of bond behaviour. Bending tests furthermore show the potential of this reinforcement method. The bond stress of cables in printed concrete was comparable to values reported for smooth rebar but lower than that of the same cables in cast concrete. The scatter in experimental results was high. When sufficient bond length is available, ductile failure behaviour for tension parallel to the filament direction can be achieved, even though cable slip occurs. Further improvements to the process should pave the way to achieve better post-crack resistance, as the concept in itself is feasible. PMID:29144426

Effects of isotropic and anisotropic slip on droplet impingement on a superhydrophobic surface

NASA Astrophysics Data System (ADS)

Clavijo, Cristian E.; Crockett, Julie; Maynes, Daniel

2015-12-01

The dynamics of single droplet impingement on micro-textured superhydrophobic surfaces with isotropic and anisotropic slip are investigated. While several analytical models exist to predict droplet impact on superhydrophobic surfaces, no previous model has rigorously considered the effect of the shear-free region above the gas cavities resulting in an apparent slip that is inherent for many of these surfaces. This paper presents a model that accounts for slip during spreading and recoiling. A broad range of Weber numbers and slip length values were investigated at low Ohnesorge numbers. The results show that surface slip exerts negligible influence throughout the impingement process for low Weber numbers but can exert significant influence for high Weber numbers (on the order of 102). When anisotropic slip prevails, the droplet exhibits an elliptical shape at the point of maximum spread, with greater eccentricity for increasing slip and increasing Weber number. Experiments were performed on isotropic and anisotropic micro-structured superhydrophobic surfaces and the agreement between the experimental results and the model is very good.

Modeling the surface contamination of dental titanium investment castings.

PubMed

Atwood, R C; Lee, P D; Curtis, R V

2005-02-01

The objective of this study was to develop a computational tool for assisting the design of titanium dental castings with minimal defects and to compare computational simulations with casting experiments. Modeling. An in-house cellular-automata solidification and finite-difference diffusion program was coupled with a commercial casting program and applied to (a) simple geometric wedge models and (b) a 3D-laser scan of a molar crown casting. Experimental. Wedges and molar crowns were hand-waxed and investment cast in commercial purity grade 1 (CP-1) titanium by a commercial dental laboratory. The castings were sectioned and analyzed using light and scanning electron microscopy, X-ray microanalysis, and microhardness testing. In the wedge sample, contamination with impurities (Al, Si), including intermetallic precipitates, was found to extend to a depth ranging from 30 to 120 microm depending on the section thickness and hence the local cooling rate. Microstructural and mechanical (hardness) effects were found to a depth ranging from 80 to 250 microm. The coupled micro/macro model predictions showed reasonable agreement for the pattern of contamination. Dental and medical applications demand close dimensional tolerance and freedom from surface impurities and structural flaws in castings having unique shapes. The ability to predict the structural, mechanical, and chemical changes resulting from the casting process will help to design the casting and post-casting processes to minimize these problems.

Energy Saving Melting and Revert Reduction Technology (Energy SMARRT): Manufacturing Advanced Engineered Components Using Lost Foam Casting Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Littleton, Harry; Griffin, John

2011-07-31

This project was a subtask of Energy Saving Melting and Revert Reduction Technology (Energy SMARRT) Program. Through this project, technologies, such as computer modeling, pattern quality control, casting quality control and marketing tools, were developed to advance the Lost Foam Casting process application and provide greater energy savings. These technologies have improved (1) production efficiency, (2) mechanical properties, and (3) marketability of lost foam castings. All three reduce energy consumption in the metals casting industry. This report summarizes the work done on all tasks in the period of January 1, 2004 through June 30, 2011. Current (2011) annual energy savingmore » estimates based on commercial introduction in 2011 and a market penetration of 97% by 2020 is 5.02 trillion BTU's/year and 6.46 trillion BTU's/year with 100% market penetration by 2023. Along with these energy savings, reduction of scrap and improvement in casting yield will result in a reduction of the environmental emissions associated with the melting and pouring of the metal which will be saved as a result of this technology. The average annual estimate of CO2 reduction per year through 2020 is 0.03 Million Metric Tons of Carbon Equivalent (MM TCE).« less

Compositional redistribution during casting of Hg sub 0.8 Cd sub 0.2 Te alloys

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Perry, G. L. E.; Szofran, F. R.; Lehoczky, S. L.

1986-01-01

A series of Hg(0.8)Cd(0.2)Te ingots was cast both vertically and horizontally under well-defined thermal conditions by using a two-zone furnace with isothermal heat-pipe liners. The main objective of the experiments was to establish correlations between casting parameters and compositional redistribution and to develop ground-based data for a proposed flight experiment of casting of Hg(1-x)Cd(x)Te alloys under reduced gravity conditions. The compositional variations along the axial and radial directions were determined by precision density measurements, infrared transmission spectra, and X-ray energy dispersion spectrometry. Comparison between the experimental results and a numerical simulation of the solidification process of Hg(0.8)Cd(0.2)Te is described.

Two-dimensional nonlinear finite element analysis of well damage due to reservoir compaction, well-to-well interactions, and localization on weak layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hilbert, L.B. Jr.; Fredrich, J.T.; Bruno, M.S.

1996-05-01

In this paper the authors present the results of a coupled nonlinear finite element geomechanics model for reservoir compaction and well-to-well interactions for the high-porosity, low strength diatomite reservoirs of the Belridge field near Bakersfield, California. They show that well damage and failures can occur under the action of two distinct mechanisms: shear deformations induced by pore compaction, and subsidence, and shear deformations due to well-to-well interactions during production or water injection. They show such casting damage or failure can be localized to weak layers that slide or slip under shear due to subsidence. The magnitude of shear displacements andmore » surface subsidence agree with field observations.« less

Dynamic Mechanical Properties of Bio-Polymer Graphite Thin Films

NASA Astrophysics Data System (ADS)

Saddam Kamarudin, M.; Rus, Anika Zafiah M.; Munirah Abdullah, Nur; Abdullah, M. F. L.

2017-08-01

Waste cooking oil is used as the main substances in producing graphite biopolymer thin films. Biopolymer is produce from the reaction of bio-monomer and cross linker with the ratio of 2:1 and addition of graphite with an increment of 2% through a slip casting method. The morphological surface properties of the samples are observed by using Scanning Electron Microscope (SEM). It is shown that the graphite particle is well mixed and homogenously dispersed in biopolymer matrix. Meanwhile, the mechanical response of materials by monitoring the change in the material properties in terms of frequency and temperature of the samples were determined using Dynamic Mechanical Analysis (DMA). The calculated cross-linked density of biopolymer composites revealed the increment of graphite particle loading at 8% gives highest results with 260.012 x 103 M/m3.

Method and apparatus for casting conductive and semi-conductive materials

DOEpatents

Ciszek, T.F.

1984-08-13

A method and apparatus is disclosed for casting conductive and semi-conductive materials. The apparatus includes a plurality of conductive members arranged to define a container-like area having a desired cross-sectional shape. A portion or all of the conductive or semi-conductive material which is to be cast is introduced into the container-like area. A means is provided for inducing the flow of an electrical current in each of the conductive members, which currents act collectively to induce a current flow in the material. The induced current flow through the conductive members is in a direction substantially opposite to the induced current flow in the material so that the material is repelled from the conductive members during the casting process.

SSME Main Combustion Chamber (MCC) hot oil dewaxing

NASA Technical Reports Server (NTRS)

Akpati, Anthony U.

1995-01-01

In an attempt to comply with the changing environmental regulations, a process was developed for the replacement of perchloroethylene in the dewaxing of the Space Shuttle Main Engine (SSME) Main Combustion Chamber (MCC) and other associated hardware filled with the Rigidax (R) casting compound. Rigidax (R) is a hard blue-dyed, calcium carbonate filled thermoplastic casting compound (melting point 77 C) that is melted and poured into hardware cavities to prevent contamination during material removal processes, i.e. machining, grinding, drilling, and deburring. Additionally, it serves as a maskant for designated areas during electroforming processes. Laboratory testing was conducted to evaluate seven alternate fluids for the replacement of perchloroethylene in the dewaxing process. Based upon successful laboratory results, a mineral oil was selected for testing on actual hardware. The final process developed involves simultaneous immersion and flushing of the MCC channels using a distinct eight stage process. A nonvolatile hydrocarbon analysis of a solvent flush sample is performed to determine the hardware cleanliness for comparison to the previous perchloroethylene dewaxing process.

Direct Cast U-6Nb – 2017 Progress on Cylindrical Castings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aikin, Jr., Robert M.

2017-10-04

This report describes work to further develop a sound technical basis and best practices for mold design and process parameters for the Direct Casting of U-6wt%Nb components. One major challenge to the production of U-6Nb components is the propensity for niobium segregation during casting and solidification. This is especially true for cylindrical castings where the vertical side walls allow flotation of Nb resulting in severe inverse macrosegregation. In this work, a small (120 mm diameter by 180 mm tall) and large cylinder (250 mm diameter by 310 mm tall) are examined with a focus on reducing, or eliminating, niobium segregation.more » It is demonstrated that counter gravity casting (top-to-bottom solidification) can be used to minimize segregation in the small cylinder. Attempts to counter gravity cast the large cylinder were unsuccessful, in large part due to size limitations of the current furnace. A path forward for casting of the large cylinders is discussed.« less

Freeze-Casting of Porous Biomaterials: Structure, Properties and Opportunities

PubMed Central

Deville, Sylvain

2010-01-01

The freeze-casting of porous materials has received a great deal of attention during the past few years. This simple process, where a material suspension is simply frozen and then sublimated, provides materials with unique porous architectures, where the porosity is almost a direct replica of the frozen solvent crystals. This review focuses on the recent results on the process and the derived porous structures with regards to the biomaterials applications. Of particular interest is the architecture of the materials and the versatility of the process, which can be readily controlled and applied to biomaterials applications. A careful control of the starting formulation and processing conditions is required to control the integrity of the structure and resulting properties. Further in vitro and in vivo investigations are required to validate the potential of this new class of porous materials.

The analysis of composite properties reinforced with particles from palm oil industry waste produced by casting methods

NASA Astrophysics Data System (ADS)

Tugiman; Ariani, F.; Taher, F.; Hasibuan, M. S.; Suprianto

2017-12-01

Palm oil processing industries are very attractive because they offer plenty products with high economic value. The CPO factory processes not only produces crude palm oil but also generates fly ash (FA) particles waste in its final process. The purpose of this investigation to analyze and increase the benefits of particles as reinforcement materials for fabricating aluminum matrix composites (AMC’s) by different casting route. Stirring, centrifugal and squeeze casting method was conducted in this study. Further, the chemical composition of FA particles, densities and mechanical properties have been analyzed. The characteristics of composite material were investigated using an Optical microscope, scanning electron microscope (SEM), hardness (Brinell), impact strength (Charpy). The pin on disc method was used to measure the wear rate. The results show that SiO2, Fe2O3, and Al2O3 are the main compounds of fly ash particles. These particles enhanced the hardness and reduce wear resistance of aluminum matrix composites. The squeeze method gives better results than stir and centrifugal casting.

Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Use of Laser Engineered Net Shaping for Rapid Manufacturing of Dies with Protective Coatings and Improved Thermal Management

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brevick, Jerald R.

2014-06-13

In the high pressure die casting process, molten metal is introduced into a die cavity at high pressure and velocity, enabling castings of thin wall section and complex geometry to be obtained. Traditional die materials have been hot work die steels, commonly H13. Manufacture of the dies involves machining the desired geometry from monolithic blocks of annealed tool steel, heat treating to desired hardness and toughness, and final machining, grinding and polishing. The die is fabricated with internal water cooling passages created by drilling. These materials and fabrication methods have been used for many years, however, there are limitations. Toolmore » steels have relatively low thermal conductivity, and as a result, it takes time to remove the heat from the tool steel via the drilled internal water cooling passages. Furthermore, the low thermal conductivity generates large thermal gradients at the die cavity surfaces, which ultimately leads to thermal fatigue cracking on the surfaces of the die steel. The high die surface temperatures also promote the metallurgical bonding of the aluminum casting alloy to the surface of the die steel (soldering). In terms of process efficiency, these tooling limitations reduce the number of die castings that can be made per unit time by increasing cycle time required for cooling, and increasing downtime and cost to replace tooling which has failed either by soldering or by thermal fatigue cracking (heat checking). The objective of this research was to evaluate the feasibility of designing, fabricating, and testing high pressure die casting tooling having properties equivalent to H13 on the surface in contact with molten casting alloy - for high temperature and high velocity molten metal erosion resistance – but with the ability to conduct heat rapidly to interior water cooling passages. A layered bimetallic tool design was selected, and the design evaluated for thermal and mechanical performance via finite element analysis. H13 was retained as the exterior layer of the tooling, while commercially pure copper was chosen for the interior structure of the tooling. The tooling was fabricated by traditional machining of the copper substrate, and H13 powder was deposited on the copper via the Laser Engineered Net Shape (LENSTM) process. The H13 deposition layer was then final machined by traditional methods. Two tooling components were designed and fabricated; a thermal fatigue test specimen, and a core for a commercial aluminum high pressure die casting tool. The bimetallic thermal fatigue specimen demonstrated promising performance during testing, and the test results were used to improve the design and LENS TM deposition methods for subsequent manufacture of the commercial core. Results of the thermal finite element analysis for the thermal fatigue test specimen indicate that it has the ability to lose heat to the internal water cooling passages, and to external spray cooling, significantly faster than a monolithic H13 thermal fatigue sample. The commercial core is currently in the final stages of fabrication, and will be evaluated in an actual production environment at Shiloh Die casting. In this research, the feasibility of designing and fabricating copper/H13 bimetallic die casting tooling via LENS TM processing, for the purpose of improving die casting process efficiency, is demonstrated.« less

Thermal analysis on Al7075/Al2O3 metal matrix composites fabricated by stir casting process

NASA Astrophysics Data System (ADS)

Jacob, S.; Shajin, S.; Gnanavel, C.

2017-03-01

Metal matrix Composites (MMC’s) have evoked a keen interest in recent times for various applications in aerospace, renewable energy and automotive industries due to their superior strength, low cost, easy availability and high temperature resistance [1]. The crack and propagation occurs in conventional materials without any appreciable indication in a short span. Hence composite materials are preferred nowadays to overcome this problem [2]. The process of metal matrix composites (MMC’s) is to unite the enviable attributes of metals and ceramics. The Stir casting method is used for producing aluminium metal matrix composites (AMC’s). A key challenge of the process is to spread the ceramic particles to achieve a defect free microstructure [2]. By carefully selecting stir casting processing specification, such as stirring time, temperature of the melt and blade angle, the desired microstructure can be obtained. The focus of this work is to develop a high strength particulate strengthen aluminium metal matrix composites, and Al7075 was selected which can offer high strength without much disturbing ductility of metal matrix [4]. The composites will be examined using standard metallurgical and mechanical tests. The cast composites are analysed to Laser flash analysis (LFA) to determine Thermal conductivity [5]. Also changes in microstructure are determined by using SEM analysis.

Thermal Stress and Heat Transfer Coefficient for Ceramics Stalk Having Protuberance Dipping into Molten Metal

NASA Astrophysics Data System (ADS)

Noda, Nao-Aki; Hendra; Li, Wenbin; Takase, Yasushi; Ogura, Hiroki; Higashi, Yusuke

Low pressure die casting is defined as a net shape casting technology in which the molten metal is injected at high speeds and pressure into a metallic die. The low pressure die casting process plays an increasingly important role in the foundry industry as a low-cost and high-efficiency precision forming technique. In the low pressure die casting process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal, by means of a pressurized gas, to rise into a ceramic tube having protuberance, which connects the die to the furnace. The ceramics tube, called stalk, has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the stalk having protuberance is dipped into the molten aluminum. It is important to reduce the risk of fracture that may happen due to the thermal stresses. In this paper, thermo-fluid analysis is performed to calculate surface heat transfer coefficient. The finite element method is applied to calculate the thermal stresses when the stalk having protuberance is dipped into the crucible with varying dipping speeds. It is found that the stalk with or without protuberance should be dipped into the crucible slowly to reduce the thermal stress.

Plastic dynamics of the Al0.5CoCrCuFeNi high entropy alloy at cryogenic temperatures: Jerky flow, stair-like fluctuation, scaling behavior, and non-chaotic state

NASA Astrophysics Data System (ADS)

Guo, Xiaoxiang; Xie, Xie; Ren, Jingli; Laktionova, Marina; Tabachnikova, Elena; Yu, Liping; Cheung, Wing-Sum; Dahmen, Karin A.; Liaw, Peter K.

2017-12-01

This study investigates the plastic behavior of the Al0.5CoCrCuFeNi high-entropy alloy at cryogenic temperatures. The samples are uniaxially compressed at 4.2 K, 7.5 K, and 9 K. A jerky evolution of stress and stair-like fluctuation of strain are observed during plastic deformation. A scaling relationship is detected between the released elastic energy and strain-jump sizes. Furthermore, the dynamical evolution of serrations is characterized by the largest Lyapunov exponent. The largest Lyapunov exponents of the serrations at the three temperatures are all negative, which indicates that the dynamical regime is non-chaotic. This trend reflects an ordered slip process, and this ordered slip process exhibits a more disordered slip process, as the temperature decreases from 9 K to 4.2 K or 7.5 K.

Development of Integrated Die Casting Process for Large Thin-Wall Magnesium Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carter, Jon T.; Wang, Gerry; Luo, Alan

The purpose of this project was to develop a process and product which would utilize magnesium die casting and result in energy savings when compared to the baseline steel product. The specific product chosen was a side door inner panel for a mid-size car. The scope of the project included: re-design of major structural parts of the door, design and build of the tooling required to make the parts, making of parts, assembly of doors, and testing (both physical and simulation) of doors. Additional work was done on alloy development, vacuum die casting, and overcasting, all in order to improvemore » the performance of the doors and reduce cost. The project achieved the following objectives: 1. Demonstrated ability to design a large thin-wall magnesium die casting. 2. Demonstrated ability to manufacture a large thin-wall magnesium die casting in AM60 alloy. 3. Tested via simulations and/or physical tests the mechanical behavior and corrosion behavior of magnesium die castings and/or lightweight experimental automotive side doors which incorporate a large, thin-wall, powder coated, magnesium die casting. Under some load cases, the results revealed cracking of the casting, which can be addressed with re-design and better material models for CAE analysis. No corrosion of the magnesium panel was observed. 4. Using life cycle analysis models, compared the energy consumption and global warming potential of the lightweight door with those of a conventional steel door, both during manufacture and in service. Compared to a steel door, the lightweight door requires more energy to manufacture but less energy during operation (i.e., fuel consumption when driving vehicle). Similarly, compared to a steel door, the lightweight door has higher global warming potential (GWP) during manufacture, but lower GWP during operation. 5. Compared the conventional magnesium die casting process with the “super-vacuum” die casting process. Results achieved with cast tensile bars suggest some improvement in tensile properties with vacuum casting. Plant trials with large castings revealed cavity fill issues attributed to cooling and partial solidification of metal in the shot sleeve while waiting for vacuum to be established in the die cavity. 6. Developed age-hardenable Mg-based alloys as potential alternatives to the AM60 and AZ91 alloys typically used in automotive applications. Mg-7%Al-based alloys having Sn or Sn+Si additions exhibited significant age hardening, but more work is needed to demonstrate significant improvement in tensile properties. Corrosion behavior of these alloys is between those of AM60 and AZ91 alloys. 7. Evaluated the die casting of magnesium directly onto either steel or aluminum tubes as a potential process to make large lightweight subassemblies. Samples were free of gross defects, but additional work is needed to increase the interfacial shear strength. Overall, the project demonstrated that an automotive door-in-white design incorporating a die cast magnesium inner panel and a stamped aluminum outer panel can achieve approximately 50% mass reduction compared to the stamped steel baseline door-in-white. This leads to reduced energy consumption when driving the vehicle, which should more than offset the increased embedded energy of manufacture associated with the lighter metals. However, additional design work would be needed in order to meet the mechanical performance required of a door. Development of high-strength, high-ductility magnesium alloy castings would help make this technology more attractive for potential use in the side doors on automobiles. Also, increased use of recycled magnesium and aluminum would reduce the embedded energy and greenhouse gas emissions associated with the manufacture of this type of lightweight door. Commercialization planning of the type of lightweight door technology addressed in this project would be contingent upon the doors meeting all technical performance requirements of the car maker. The specific lightweight door developed in this project didn’t meet some of those requirements, but a preliminary business case study was conducted anyhow. This study considered the ratio of cost increase to mass decrease when the lightweight door is compared to a baseline steel door. The ratio was found to be in an acceptable range for some vehicle programs, especially if the number of such vehicles to be produced is equal to or slightly less than the estimated 250,000-shot life of the die set. This would allow for the investment in the dies to be spread across many parts and thereby help minimize the cost increase.« less

Rapidly solidified titanium alloys by melt overflow

NASA Technical Reports Server (NTRS)

Gaspar, Thomas A.; Bruce, Thomas J., Jr.; Hackman, Lloyd E.; Brasmer, Susan E.; Dantzig, Jonathan A.; Baeslack, William A., III

1989-01-01

A pilot plant scale furnace was designed and constructed for casting titanium alloy strips. The furnace combines plasma arc skull melting techniques with melt overflow rapid solidification technology. A mathematical model of the melting and casting process was developed. The furnace cast strip of a suitable length and width for use with honeycomb structures. Titanium alloys Ti-6Al-4V and Ti-14Al-21 Nb were successfully cast into strips. The strips were evaluated by optical metallography, microhardness measurements, chemical analysis, and cold rolling.

A new magnesium alloy system: TEXAS

NASA Astrophysics Data System (ADS)

Wiese, Björn; Mendis, Chamini; Blawert, Carsten; Nyberg, Eric; Kainer, Karl Ulrich; Hort, Norbert

A new TEXAS alloy system (Mg-Sn-Nd-Ca-Al-Si) is presented in order to extend the range of applications for magnesium alloys. The alloy has been produced by permanent mould direct chill casting, a process that provides a homogenous distribution of alloying elements throughout the entire casting. This work presents microstructural features and a new Mg-Sn-Ca phase with the morphology of hexagonal platelets. Additionally mechanical properties and the corrosion behaviour of TEXAS alloys are presented in as cast and heat treated conditions.

System and process for the abatement of casting pollution, reclaiming resin bonded sand, and/or recovering a low BTU fuel from castings

DOEpatents

Scheffer, Karl D.

1984-07-03

Air is caused to flow through the resin bonded mold to aid combustion of the resin binder to form a low BTU gas fuel. Casting heat is recovered for use in a waste heat boiler or other heat abstraction equipment. Foundry air pollution is reduced, the burned portion of the molding sand is recovered for immediate reuse and savings in fuel and other energy is achieved.

Porous ceramic scaffolds with complex architectures

NASA Astrophysics Data System (ADS)

Munch, E.; Franco, J.; Deville, S.; Hunger, P.; Saiz, E.; Tomsia, A. P.

2008-06-01

This work compares two novel techniques for the fabrication of ceramic scaffolds for bone tissue engineering with complex porosity: robocasting and freeze casting. Both techniques are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.

SSME Main Combustion Chamber (MCC) 'Hot Oil' Dewaxing

NASA Technical Reports Server (NTRS)

Akpati, Anthony U.

1994-01-01

In an attempt to comply with the changing environmental regulations, a process was developed for the replacement of perchloroethylene in the dewaxing of the Space Shuttle Main Engine (SSME) Main Combustion Chamber (MCC) and other associated hardware filled with the Rigidax(registered mark) casting compound. Rigidax(registered mark) is a hard blue-dyed, calcium carbonate filled thermoplastic casting compound (melting point 77 C) that is melted and poured into hardware cavities to prevent contamination during material removal processes, i.e. machining, grinding, drilling, and deburring. Additionally, it serves as a maskant for designated areas during electroforming processes. Laboratory testing was conducted to evaluate seven alternate fluids for the replacement of perchloroethylene in the dewaxing process. Based upon successful laboratory results, a mineral oil was selected for testing on actual hardware. The final process developed involves simultaneous immersion and flushing of the MCC channels using a distinct eight stage process. A nonvolatile hydrocarbon analysis of a solvent flush sample is performed to determine the hardware cleanliness for comparison to the previous perchloroethylene dewaxing process.

Silica coatings formed on noble dental casting alloy by the sol-gel dipping process.

PubMed

Yoshida, K; Tanagawa, M; Kamada, K; Hatada, R; Baba, K; Inoi, T; Atsuta, M

1999-08-01

The sol-gel dipping process, in which liquid silicon alkoxide is transformed into the solid silicon-oxygen network, can produce a thin film coating of silica (SiO2). The features of this method are high homogeneity and purity of the thin SiO2 film and a low sinter temperature, which are important in preparation of coating films that can protect from metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface characteristics of the dental casting silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy coated with a thin SiO2 film by the sol-gel dipping process. The SiO2 film bonded strongly (over 40 MPa) to Ti-implanted Ag-Pd-Cu-Au alloy substrate as demonstrated by a pull test. Hydrophobilization of Ti-implanted/SiO2-coated surfaces resulted in a significant increase of the contact angle of water (80.5 degrees) compared with that of the noncoated alloy specimens (59.3 degrees). Ti-implanted/SiO2-coated specimens showed the release of many fewer metallic ions (192 ppb/cm2) from the substrate than did noncoated specimens (2,089 ppb/cm2). The formation of a thin SiO2 film by the sol-gel dipping process on the surface of Ti-implanted Ag-Pd-Cu-Au alloy after casting clinically may be useful for minimizing the possibilities of the accumulation of dental plaque and metal allergies caused by intraoral metal restorations.

Novel casting processes for single-crystal turbine blades of superalloys

NASA Astrophysics Data System (ADS)

Ma, Dexin

2018-03-01

This paper presents a brief review of the current casting techniques for single-crystal (SC) blades, as well as an analysis of the solidification process in complex turbine blades. A series of novel casting methods based on the Bridgman process were presented to illustrate the development in the production of SC blades from superalloys. The grain continuator and the heat conductor techniques were developed to remove geometry-related grain defects. In these techniques, the heat barrier that hinders lateral SC growth from the blade airfoil into the extremities of the platform is minimized. The parallel heating and cooling system was developed to achieve symmetric thermal conditions for SC solidification in blade clusters, thus considerably decreasing the negative shadow effect and its related defects in the current Bridgman process. The dipping and heaving technique, in which thinshell molds are utilized, was developed to enable the establishment of a high temperature gradient for SC growth and the freckle-free solidification of superalloy castings. Moreover, by applying the targeted cooling and heating technique, a novel concept for the three-dimensional and precise control of SC growth, a proper thermal arrangement may be dynamically established for the microscopic control of SC growth in the critical areas of large industrial gas turbine blades.

Obtaining of High Cr Content Cast Iron Materials

NASA Astrophysics Data System (ADS)

Florea, C.; Bejinariu, C.; Carcea, I.; Cimpoesu, N.; Chicet, D. L.; Savin, C.

2017-06-01

We have obtained, through the classic casting process, 3 highly chromium-based experimental alloys proposed for replacing the FC 250 classical cast iron in braking applications. Casting was carried out in an induction furnace and cast into moulds made of KALHARTZ 8500 resin casting mixture and HARTER hardener at SC RanCon SRL Iasi. It is known that the microstructure of the cast iron is a combination of martensite with a small amount of residual austenite after the heat treatment of the ingot. In the case of high-alloy chromium alloys, the performance of the material is due to the presence of M7C3 carbides distributed in the iron matrix Resistance to machining and deformation is based on alloy composition and microstructure, while abrasion resistance will depend on properties and wear conditions.

System and process for the abatement of casting pollution, reclaiming resin bonded sand, and/or recovering a low Btu fuel from castings

DOEpatents

Scheffer, K.D.

1984-07-03

Air is caused to flow through the resin bonded mold to aid combustion of the resin binder to form a low Btu gas fuel. Casting heat is recovered for use in a waste heat boiler or other heat abstraction equipment. Foundry air pollutis reduced, the burned portion of the molding sand is recovered for immediate reuse and savings in fuel and other energy is achieved. 5 figs.

A process chain for integrating piezoelectric transducers into aluminum die castings to generate smart lightweight structures

NASA Astrophysics Data System (ADS)

Stein, Stefan; Wedler, Jonathan; Rhein, Sebastian; Schmidt, Michael; Körner, Carolin; Michaelis, Alexander; Gebhardt, Sylvia

The application of piezoelectric transducers to structural body parts of machines or vehicles enables the combination of passive mechanical components with sensor and actuator functions in one single structure. According to Herold et al. [1] and Staeves [2] this approach indicates significant potential regarding smart lightweight construction. To obtain the highest yield, the piezoelectric transducers need to be integrated into the flux of forces (load path) of load bearing structures. Application in a downstream process reduces yield and process efficiency during manufacturing and operation, due to the necessity of a subsequent process step of sensor/actuator application. The die casting process offers the possibility for integration of piezoelectric transducers into metal structures. Aluminum castings are particularly favorable due to their high quality and feasibility for high unit production at low cost (Brunhuber [3], Nogowizin [4]). Such molded aluminum parts with integrated piezoelectric transducers enable functions like active vibration damping, structural health monitoring or energy harvesting resulting in significant possibilities of weight reduction, which is an increasingly important driving force of automotive and aerospace industry (Klein [5], Siebenpfeiffer [6]) due to increasingly stringent environmental protection laws. In the scope of those developments, this paper focuses on the entire process chain enabling the generation of lightweight metal structures with sensor and actuator function, starting from the manufacturing of piezoelectric modules over electrical and mechanical bonding to the integration of such modules into aluminum (Al) matrices by die casting. To achieve this challenging goal, piezoceramic sensors/actuator modules, so-called LTCC/PZT modules (LPM) were developed, since ceramic based piezoelectric modules are more likely to withstand the thermal stress of about 700 °C introduced by the casting process (Flössel et al., [7]). The modules are made of low temperature cofired ceramic (LTCC) tapes with an embedded lead zirconate titanate (PZT) plate and are manufactured in multilayer technique. For joining conducting copper (Cu) wires with the electrode structure of the LPM, a novel laser drop on demand wire bonding method (LDB) is applied, which is based on the melting of a spherical CuSn12 braze preform with a liquidus temperature Tliquid of 989.9 °C (Deutsches Kupfer-Institut Düsseldorf, [8]) providing sufficient thermal stability for a subsequent casting process.

Slip reactivation during the 2011 Tohoku earthquake: Dynamic rupture and ground motion simulations

NASA Astrophysics Data System (ADS)

Galvez, P.; Dalguer, L. A.

2013-12-01

The 2011 Mw9 Tohoku earthquake generated such as vast geophysical data that allows studying with an unprecedented resolution the spatial-temporal evolution of the rupture process of a mega thrust event. Joint source inversion of teleseismic, near-source strong motion and coseismic geodetic data , e.g [Lee et. al, 2011], reveal an evidence of slip reactivation process at areas of very large slip. The slip of snapshots of this source model shows that after about 40 seconds the big patch above to the hypocenter experienced an additional push of the slip (reactivation) towards the trench. These two possible repeating slip exhibited by source inversions can create two waveform envelops well distinguished in the ground motion pattern. In fact seismograms of the KiK-Net Japanese network contained this pattern. For instance a seismic station around Miyagi (MYGH10) has two main wavefronts separated between them by 40 seconds. A possible physical mechanism to explain the slip reactivation could be a thermal pressurization process occurring in the fault zone. In fact, Kanamori & Heaton, (2000) proposed that for large earthquakes frictional melting and fluid pressurization can play a key role of the rupture dynamics of giant earthquakes. If fluid exists in a fault zone, an increase of temperature can rise up the pore pressure enough to significantly reduce the frictional strength. Therefore, during a large earthquake the areas of big slip persuading strong thermal pressurization may result in a second drop of the frictional strength after reaching a certain value of slip. Following this principle, we adopt for slip weakening friction law and prescribe a certain maximum slip after which the friction coefficient linearly drops down again. The implementation of this friction law has been done in the latest unstructured spectral element code SPECFEM3D, Peter et. al. (2012). The non-planar subduction interface has been taken into account and place on it a big asperity patch inside areas of big slip (>50m) close to the trench. Within the first 2km bellow the trench a negative stress drop has been imposed in order to represent the energy absorption zone that attenuates a high frequency radiation at the shallow part of the suduction zone. At down dip, where high frequency radiation burst has been detected from back projection techniques, e.g. [Meng et. al, 2011; Ishi , 2011], small asperities has been considered in our dynamic rupture model. Finally, a comparison of static geodetic free surface displacement and synthetics has been made to obtain our best model. We additionally compare seismograms with the aim to represent the main features of the strong ground motion recorded from this earthquake. Moreover, the spatial-temporal rupture evolution detected by back projection at down dip is in a good agreement with the rupture evolution of our dynamic model.

Enhancing Manufacturing Process Education via Computer Simulation and Visualization

ERIC Educational Resources Information Center

Manohar, Priyadarshan A.; Acharya, Sushil; Wu, Peter

2014-01-01

Industrially significant metal manufacturing processes such as melting, casting, rolling, forging, machining, and forming are multi-stage, complex processes that are labor, time, and capital intensive. Academic research develops mathematical modeling of these processes that provide a theoretical framework for understanding the process variables…

Integrated modeling and heat treatment simulation of austempered ductile iron

NASA Astrophysics Data System (ADS)

Hepp, E.; Hurevich, V.; Schäfer, W.

2012-07-01

The integrated modeling and simulation of the casting and heat treatment processes for producing austempered ductile iron (ADI) castings is presented. The focus is on describing different models to simulate the austenitization, quenching and austempering steps during ADI heat treatment. The starting point for the heat treatment simulation is the simulated microstructure after solidification and cooling. The austenitization model considers the transformation of the initial ferrite-pearlite matrix into austenite as well as the dissolution of graphite in austenite to attain a uniform carbon distribution. The quenching model is based on measured CCT diagrams. Measurements have been carried out to obtain these diagrams for different alloys with varying Cu, Ni and Mo contents. The austempering model includes nucleation and growth kinetics of the ADI matrix. The model of ADI nucleation is based on experimental measurements made for varied Cu, Ni, Mo contents and austempering temperatures. The ADI kinetic model uses a diffusion controlled approach to model the growth. The models have been integrated in a tool for casting process simulation. Results are shown for the optimization of the heat treatment process of a planetary carrier casting.

Tuning the properties of polyhydroxybutyrate films using acetic acid via solvent casting

PubMed Central

Anbukarasu, Preetam; Sauvageau, Dominic; Elias, Anastasia

2015-01-01

Biodegradable polyhydroxybutyrate (PHB) films were fabricated using acetic acid as an alternative to common solvents such as chloroform. The PHB films were prepared using a solvent casting process at temperatures ranging from 80 °C to 160 °C. The crystallinity, mechanical properties and surface morphology of the films cast at different temperatures were characterized and compared to PHB films cast using chloroform as a solvent. Results revealed that the properties of the PHB film varied considerably with solvent casting temperature. In general, samples processed with acetic acid at low temperatures had comparable mechanical properties to PHB cast using chloroform. This acetic acid based method is environmentally friendly, cost efficient and allows more flexible processing conditions and broader ranges of polymer properties than traditional methods. PMID:26640089

Tuning the properties of polyhydroxybutyrate films using acetic acid via solvent casting

NASA Astrophysics Data System (ADS)

Anbukarasu, Preetam; Sauvageau, Dominic; Elias, Anastasia

2015-12-01

Biodegradable polyhydroxybutyrate (PHB) films were fabricated using acetic acid as an alternative to common solvents such as chloroform. The PHB films were prepared using a solvent casting process at temperatures ranging from 80 °C to 160 °C. The crystallinity, mechanical properties and surface morphology of the films cast at different temperatures were characterized and compared to PHB films cast using chloroform as a solvent. Results revealed that the properties of the PHB film varied considerably with solvent casting temperature. In general, samples processed with acetic acid at low temperatures had comparable mechanical properties to PHB cast using chloroform. This acetic acid based method is environmentally friendly, cost efficient and allows more flexible processing conditions and broader ranges of polymer properties than traditional methods.

Multiscale Computational Design Optimization of Copper-Strengthened Steel for High Cycle Fatigue

DTIC Science & Technology

2010-03-19

strain energy) and (3) modeling of a slip band (of PSB ladder underlying structure) and attendant crack initiation process. 15. SUBJECT TERMS 16...energy). (C) A modeling of a slip band (of PSB ladder underlying structure) and attendant crack initiation process. Major results obtained are...differentiate the morphology from others, e.g., vein and planar structures of dislocations. Results and Discussion for (C) (C-1) Modeling PSB For modeling

The effect of investment type on the fit of cast titanium crowns.

PubMed

Mori, T; Jean-Louis, M; Yabugami, M; Togaya, T

1994-12-01

In order to determine the best laboratory procedure for titanium crown casting, a set of thermal expansion measurements and casting experiments were carried out using a casting machine (argon arc, pressure difference type) and three different investments, two conventional SiO2 based investments and a new Al2O3/MgO based investment. The thermal expansion measurements involved a cycle of heating and cooling. The relatively low mould temperatures recommended (200 degrees C) or chosen (350 degrees C) for the conventional investments provided zero or negative mould expansion for the compensation of metal shrinkage. Crowns made from these investments exhibited heavy reaction with the mould, and the common cleaning method of sand blasting appeared to be essential. This cleaning process, however, was not adequate for the assessment of casting accuracy as the short sand blasting time (15 s) rapidly altered the fit of the crowns. The metal reacted little with the new investment and the best compensation (0.15 mm discrepancy) for the metal shrinkage, as assessed 'as cast', was achieved when the investment was heated to 950 degrees C and then cooled to the recommended mould temperature (600 degrees C).

Spatiotemporal evolution of premonitory fault slip prior to stick-slip instability: New insight into the earthquake preparation

NASA Astrophysics Data System (ADS)

Zhuo, Y. Q.; Liu, P.; Guo, Y.; Ji, Y.; Ma, J.

2017-12-01

Premonitory fault slip, which begins with quasistatic propagation followed by quasidynamic propagation, may be a key clue bridging the "stick" state and "slip" state of a fault. More attentions have been paid for a long time to the temporal resolution of measurement than the spatial resolution, leading to the incomplete interpretation for the spatial evolution of premonitory slip, particularly during the quasistatic phase. In the present study, measurement of the quasistatic propagation of premonitory slip is achieved at an ultrahigh spatial resolution via a digital image correlation method. Multiple premonitory slip zones are observed and found to be controlled spatially by the fault contact heterogeneity, particularly the strong contact patches that prevent the propagation of premonitory slip and accumulate strain. As a result, premonitory slip is accelerated within constrained week contact spaces and consequently triggers the breakout of quasidynamic propagation. The results provide new insights into the quasistatic propagation of premonitory slip and may offer new interpretations for the earthquake nucleation process. This work is fund by the National Natural Science Foundation of China (Grant No. 41572181), the Basic Scientific Funding of Chinese National Nonprofit Institutes (Grant No. IGCEA1415, IGCEA1525), and the Early-Stage Work of Key Breakthrough Plan in Seismology from China Earthquake Administration.

Rapid Model Fabrication and Testing for Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Buck, Gregory M.

2000-01-01

Advanced methods for rapid fabrication and instrumentation of hypersonic wind tunnel models are being developed and evaluated at NASA Langley Research Center. Rapid aeroheating model fabrication and measurement techniques using investment casting of ceramic test models and thermographic phosphors are reviewed. More accurate model casting techniques for fabrication of benchmark metal and ceramic test models are being developed using a combination of rapid prototype patterns and investment casting. White light optical scanning is used for coordinate measurements to evaluate the fabrication process and verify model accuracy to +/- 0.002 inches. Higher-temperature (<210C) luminescent coatings are also being developed for simultaneous pressure and temperature mapping, providing global pressure as well as global aeroheating measurements. Together these techniques will provide a more rapid and complete experimental aerodynamic and aerothermodynamic database for future aerospace vehicles.

Permeability Evolution of Slowly Slipping Faults in Shale Reservoirs

NASA Astrophysics Data System (ADS)

Wu, Wei; Reece, Julia S.; Gensterblum, Yves; Zoback, Mark D.

2017-11-01

Slow slip on preexisting faults during hydraulic fracturing is a process that significantly influences shale gas production in extremely low permeability "shale" (unconventional) reservoirs. We experimentally examined the impacts of mineralogy, surface roughness, and effective stress on permeability evolution of slowly slipping faults in Eagle Ford shale samples. Our results show that fault permeability decreases with slip at higher effective stress but increases with slip at lower effective stress. The permeabilities of saw cut faults fully recover after cycling effective stress from 2.5 to 17.5 to 2.5 MPa and increase with slip at constant effective stress due to asperity damage and dilation associated with slip. However, the permeabilities of natural faults only partially recover after cycling effective stress returns to 2.5 MPa and decrease with slip due to produced gouge blocking fluid flow pathways. Our results suggest that slowly slipping faults have the potential to enhance reservoir stimulation in extremely low permeability reservoirs.

Modeling and simulation of clutch pressure plate casting using alternate materials

NASA Astrophysics Data System (ADS)

Madhuraj, H. N.; Bharath, M. R.

2018-04-01

Clutch Pressure Plate is a stress bearing component in the clutch assembly. Cast iron alloys like FG300, G2500 are commonly used for clutch pressure plate castings. These materials have high compressive strength, low tensile strength & no ductility but these cost high for the manufacturers. There is a need for alternate material so as to reduce cost, defects in castings without losing the life and effectiveness of the clutch plate. The work carried out here is modeling the clutch pressure plate using CAD tool. And then the casting process is simulated by casting simulation for fluid flow and solidification analysis by trying alternate material. Here the castability of the alternate material En-Gjs-400-15 and the commonly used material FG300 for the clutch pressure plate component is analyzed by designing and optimizing a proper gating system.

Development of Casting Process for Pressings of Pistons of Car Augmented Engines

NASA Astrophysics Data System (ADS)

Korostelev, V. F.; Denisov, M. S.

2017-01-01

Results of a study aimed at formation of a single-phase fine-grained structure in pistons during their production process involving isostatic pressing of liquid metal prior to the start of crystallization, pressing of the crystallizing metal, and holding under pressure in the process of cooling to the shop temperature are presented.

Evolution of Microroughness with Increasing Slip Magnitude on Pseudotachylyte-Bearing Fault Surfaces

NASA Astrophysics Data System (ADS)

Bessey, S.; Resor, P. G.; Di Toro, G.

2013-12-01

High velocity rock friction experiments reproducing seismic slip deformation conditions have shown that there is an initial shear strengthening prior to a significant weakening with slip. This change in shear resistance is inferred to occur due to the development of melt patches, which initially strengthen the fault, and is associated with the evolution of microroughness of the melt-wall rock interface (Hirose and Shimamoto, 2003). Additional melting leads to a continuous layer of melt, allowing easier sliding and weakening. Once there is a balance between formation and extrusion of melt, a steady state shear resistance (and associated effective friction coefficient) is reached (Nielsen et al. 2008). In natural fault zones, the process of frictional melting, slip weakening, and steady state is both recorded and influenced by the microroughness of the fault surface. Our study explores natural faults over a range of slip magnitudes from mm to m of slip, the magnitudes over which this process is most likely to occur during earthquakes. The Gole Larghe fault zone (Italy) is an exhumed strike-slip fault zone in tonalite of the Adamello batholith. The fault zone is characterized by multiple fault strands containing pseudotachylyte or pseudotachylyte overprinting cataclasite. We have sampled several individual faults segments from within the fault zone, with slips ranging from 23 mm to 1.9 m. The smaller scale samples are from pseudotachylyte-only fault strands and therefore probably record single-slip events. The two largest slip faults have pseudotachylyte and cataclasite, indicating that they may have more complicated slip histories. Individual samples consist of cores (2-3.5 cm diameter, 2-6 cm length) drilled parallel to the fault surface and ~perpendicular to the slip. Samples were scanned with an Xradia MicroCT scanner to image the 3D geometry of the fault and wall rocks. Fault surfaces (contact between the pseudotachylyte-bearing slipping zone and the wall rock) were extracted from the CT volume using an edge detection algorithm and their roughness was quantified using Fourier spectral and spatial analysis methods. At very small slip (<30 mm), roughness analysis showed anisotropy in the form of striations with smoothing in the direction of slip coupled with a lack of visible pseudotachylyte (i.e., the volume of pseudotachylyte produced was below the resolution of the MicroCT method), suggesting that the frictional work did not exchange sufficient heat to significantly melt the host rock along the fault surface. With increasing slip (~35mm-310mm), a trend of decreasing anisotropy is in evidence, as is a strong increase in local topography associated with recessed biotite grains. We infer that samples in this range of slip magnitude experienced significant wear due to melting. Microroughness shows a clear, albeit somewhat complicated, relationship with slip and may be used to infer the evolution of shear resistance with seismic slip.

3D Freeze-Casting of Cellular Graphene Films for Ultrahigh-Power-Density Supercapacitors.

PubMed

Shao, Yuanlong; El-Kady, Maher F; Lin, Cheng-Wei; Zhu, Guanzhou; Marsh, Kristofer L; Hwang, Jee Youn; Zhang, Qinghong; Li, Yaogang; Wang, Hongzhi; Kaner, Richard B

2016-08-01

3D cellular graphene films with open porosity, high electrical conductivity, and good tensile strength, can be synthesized by a method combining freeze-casting and filtration. The resulting supercapacitors based on 3D porous reduced graphene oxide (RGO) film exhibit extremely high specific power densities and high energy densities. The fabrication process provides an effective means for controlling the pore size, electronic conductivity, and loading mass of the electrode materials, toward devices with high energy-storage performance. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tempering Behavior of TiC-Reinforced SKD11 Steel Matrix Composite

NASA Astrophysics Data System (ADS)

Hwang, Ji-In; Kim, Seong Hoon; Heo, Yoon-Uk; Kim, Dae Ha; Hwang, Keum-Cheol; Suh, Dong-Woo

2018-03-01

TiC-reinforced SKD11 steel matrix composite, fabricated by a pressure infiltration casting, undergoes monotonic decrease in hardness as tempering temperature increases. Element mappings by TEM-EDS and thermodynamic calculation indicate that remarkable redistribution of V between the reinforcement and the steel matrix occurs by partial dissolution and re-precipitation of MC carbides upon casting process. The absence of secondary hardening is led by the enrichment of V in the reinforcement that reduces the V content in the steel matrix; this reduction in V content makes the precipitation of fine VC sluggish during the tempering.

Processing and properties of ceramic matrix-polymer composites for dental applications

NASA Astrophysics Data System (ADS)

Huang, Hsuan Yao

The basic composite structure of natural hard tissue was used to guide the design and processing of dental restorative materials. The design incorporates the methodology of using inorganic minerals as the main structural phase reinforced with a more ductile but tougher organic phase. Ceramic-polymer composites were prepared by slip casting a porous ceramic structure, heating and chemical treating the porous preform, infiltrating with monomer and then curing. The three factors that determined the mechanical properties of alumina-polymer composites were the type of polymer used, the method of silane treatments, and the type of bond between particles in the porous preforms. Without the use of silane coupling agents, the composites were measured to have a lower strength. The composite with a more "flexible" porous alumina network had a greater ability to plastically dissipate the energy of propagating cracks. However, the aggressive nature of the alumina particles on opposing enamel requires that these alumina-polymer composites have a wear compatible coating for practical application. A route to dense bioactive apatite wollastonite glass ceramics (AWGC)-polymer composites was developed. The problems associated with glass dissolution into the aqueous medium for slip casting were overcome with the use of silane. The role of heating rate and development of ceramic compact microstructure on composite properties was explored. In general, if isothermal heating was not applied, decreasing heating rate increased glass crystallinity and particle-particle fusion, but decreased pore volume. Also composite strength and fracture toughness decreased while modulus and hardness increased with decreasing heating rate. If isothermal heating was applied, glass crystallinity, pore content, and composite mechanical properties showed relatively little change regardless of the initial heating rate. The potential of AWGC-polymer composites for dental and implant applications was explored. Strengths and toughnesses were not severely degraded by immersion in simulated body fluids up to 30 days. The composite elastic modulus approached that of hard tissues and its wear behavior with opposing tooth was excellent. Growth of apatite over the entire composite surface was achieved in SBF. Growth of apatite in human whole saliva was achieved on the bioactive glass surface, but not on the composite surface.

Slip effects on MHD flow and heat transfer of ferrofluids over a moving flat plate

NASA Astrophysics Data System (ADS)

Ramli, Norshafira; Ahmad, Syakila; Pop, Ioan

2017-08-01

In this study, the problem of MHD flow and heat transfer of ferrofluids over a moving flat plate with slip effect and uniform heat flux is considered. The governing ordinary differential equations are solved via shooting method. The effect of slip parameter on the dimensionless velocity, temperature, skin friction and Nusselt numbers are numerically studied for the three selected ferroparticles; magnetite (Fe3O4), cobalt ferrite (CoFe2O4) and Mn-Zn ferrite (Mn-ZnFe2O4) with water-based fluid. The results indicate that dual solutions exist for a plate moving towards the origin. It is found that the slip process delays the boundary layer separation. Moreover, the velocity and thermal boundary-layer thicknesses decrease in the first solution while increase with the increase of the value of slip parameters in second solution.

Rupture preparation process controlled by surface roughness on meter-scale laboratory fault

NASA Astrophysics Data System (ADS)

Yamashita, Futoshi; Fukuyama, Eiichi; Xu, Shiqing; Mizoguchi, Kazuo; Kawakata, Hironori; Takizawa, Shigeru

2018-05-01

We investigate the effect of fault surface roughness on rupture preparation characteristics using meter-scale metagabbro specimens. We repeatedly conducted the experiments with the same pair of rock specimens to make the fault surface rough. We obtained three experimental results under the same experimental conditions (6.7 MPa of normal stress and 0.01 mm/s of loading rate) but at different roughness conditions (smooth, moderately roughened, and heavily roughened). During each experiment, we observed many stick-slip events preceded by precursory slow slip. We investigated when and where slow slip initiated by using the strain gauge data processed by the Kalman filter algorithm. The observed rupture preparation processes on the smooth fault (i.e. the first experiment among the three) showed high repeatability of the spatiotemporal distributions of slow slip initiation. Local stress measurements revealed that slow slip initiated around the region where the ratio of shear to normal stress (τ/σ) was the highest as expected from finite element method (FEM) modeling. However, the exact location of slow slip initiation was where τ/σ became locally minimum, probably due to the frictional heterogeneity. In the experiment on the moderately roughened fault, some irregular events were observed, though the basic characteristics of other regular events were similar to those on the smooth fault. Local stress data revealed that the spatiotemporal characteristics of slow slip initiation and the resulting τ/σ drop for irregular events were different from those for regular ones even under similar stress conditions. On the heavily roughened fault, the location of slow slip initiation was not consistent with τ/σ anymore because of the highly heterogeneous static friction on the fault, which also decreased the repeatability of spatiotemporal distributions of slow slip initiation. These results suggest that fault surface roughness strongly controls the rupture preparation process, and generally increases its complexity with the degree of roughness.

Investigation of Air-Liquid Interface Rings in Buffer Preparation Vessels: the Role of Slip Agents.

PubMed

Shi, Ting; Ding, Wei; Kessler, Donald W; De Mas, Nuria; Weaver, Douglas G; Pathirana, Charles; Martin, Russell D; Mackin, Nancy A; Casati, Michael; Miller, Scott A; Pla, Itzcoatl A

2016-01-01

Air-liquid interface rings were observed on the side walls of stainless steel buffer vessels after certain downstream buffer preparations. Those rings were resistant to regular cleaning-in-place procedures but could be removed by manual means. To investigate the root cause of this issue, multiple analytical techniques, including liquid chromatography with tandem mass spectrometry detection (LC-MS/MS), high-resolution accurate mass liquid chromatography with mass spectrometry, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy have been employed to characterize the chemical composition of air-liquid interface rings. The main component of air-liquid interface rings was determined to be slip agents, and the origin of the slip agents can be traced back to their presence on raw material packaging liners. Slip agents are commonly used in plastic industry as additives to reduce the coefficient of friction during the manufacturing process of thin films. To mitigate this air-liquid interface ring issue, an alternate liner with low slip agent was identified and implemented with minimal additional cost. We have also proactively tested the packaging liners of other raw materials currently used in our downstream buffer preparation to ensure slip agent levels are appropriate. Air-liquid interface rings were observed on the side walls of stainless steel buffer vessels after certain downstream buffer preparations. To investigate the root cause of this issue, multiple analytical techniques have been employed to characterize the chemical composition of air-liquid interface rings. The main components of air-liquid interface rings were determined to be slip agents, which are common additives used in the manufacturing process of thin films. The origin of the slip agents can be traced back to their presence on certain raw material packaging liners. To mitigate this air-liquid interface ring issue, an alternate liner with low slip agent was identified and implemented. © PDA, Inc. 2016.

Determining casting defects in near-net shape casting aluminum parts by computed tomography

NASA Astrophysics Data System (ADS)

Li, Jiehua; Oberdorfer, Bernd; Habe, Daniel; Schumacher, Peter

2018-03-01

Three types of near-net shape casting aluminum parts were investigated by computed tomography to determine casting defects and evaluate quality. The first, second, and third parts were produced by low-pressure die casting (Al-12Si-0.8Cu-0.5Fe-0.9Mg-0.7Ni-0.2Zn alloy), die casting (A356, Al-7Si-0.3Mg), and semi-solid casting (A356, Al-7Si-0.3Mg), respectively. Unlike die casting (second part), low-pressure die casting (first part) significantly reduced the formation of casting defects (i.e., porosity) due to its smooth filling and solidification under pressure. No significant casting defect was observed in the third part, and this absence of defects indicates that semi-solid casting could produce high-quality near-net shape casting aluminum parts. Moreover, casting defects were mostly distributed along the eutectic grain boundaries. This finding reveals that refinement of eutectic grains is necessary to optimize the distribution of casting defects and reduce their size. This investigation demonstrated that computed tomography is an efficient method to determine casting defects in near-net shape casting aluminum parts.

Investment casting using multi-jet modelling patterns: the thermogravimetric analysis of visijet® SR200 UV curable acrylate plastic

NASA Astrophysics Data System (ADS)

Hafsa, M. N.; Ibrahim, M.; Sharif, S.

2013-12-01

Rapid Prototyping (RP) technology is actively studied to be implemented in Investment Casting (IC) process. Nowadays RP techniques are studied for their feasibility as IC master patterns, in terms of pattern collapsibility and drainage during burnout. The purpose of the study is to determine the characteristic of Visijet® SR200 acrylate material during burnout process. Traditional IC patterns made from wax have properties that limit their application in precision casting, especially for parts with thin geometries that readily break or deform when handled or dipped in the refractory slurry. Furthermore, it is not economical when producing a small number of parts. Non wax patterns fabricated for IC process, revealed ceramic shell cracking due to excessive thermal expansions, incomplete collapsibility of pattern during burnout, residual ash and poor surface finish. Thermogravimetric analysis (TGA) was used to measured the weight loss of acrylate material as the temperature was increased. TGA measured the change of material's mass as it is heated. It represents the decomposition temperature after being subjected to varying temperatures, as well as the amount of residual ash. In this experiment, the temperature range was from 20°C to 700°C with 5°C increment. Experiment results show the values of material's optimum reaction temperature and decomposing temperature of Visijet® SR200 acrylate. The percentages of remaining materials were also monitored throughout the process to obtain the amount of residual ash. All of the temperature values obtained is a resemblance for the actual burnout process and can be used as references.

Is the co-seismic slip distribution fractal?

NASA Astrophysics Data System (ADS)

Milliner, Christopher; Sammis, Charles; Allam, Amir; Dolan, James

2015-04-01

Co-seismic along-strike slip heterogeneity is widely observed for many surface-rupturing earthquakes as revealed by field and high-resolution geodetic methods. However, this co-seismic slip variability is currently a poorly understood phenomenon. Key unanswered questions include: What are the characteristics and underlying causes of along-strike slip variability? Do the properties of slip variability change from fault-to-fault, along-strike or at different scales? We cross-correlate optical, pre- and post-event air photos using the program COSI-Corr to measure the near-field, surface deformation pattern of the 1992 Mw 7.3 Landers and 1999 Mw 7.1 Hector Mine earthquakes in high-resolution. We produce the co-seismic slip profiles of both events from over 1,000 displacement measurements and observe consistent along-strike slip variability. Although the observed slip heterogeneity seems apparently complex and disordered, a spectral analysis reveals that the slip distributions are indeed self-affine fractal i.e., slip exhibits a consistent degree of irregularity at all observable length scales, with a 'short-memory' and is not random. We find a fractal dimension of 1.58 and 1.75 for the Landers and Hector Mine earthquakes, respectively, indicating that slip is more heterogeneous for the Hector Mine event. Fractal slip is consistent with both dynamic and quasi-static numerical simulations that use non-planar faults, which in turn causes heterogeneous along-strike stress, and we attribute the observed fractal slip to fault surfaces of fractal roughness. As fault surfaces are known to smooth over geologic time due to abrasional wear and fracturing, we also test whether the fractal properties of slip distributions alters between earthquakes from immature to mature fault systems. We will present results that test this hypothesis by using the optical image correlation technique to measure historic, co-seismic slip distributions of earthquakes from structurally mature, large cumulative displacement faults and compare these slip distributions to those from immature fault systems. Our results have fundamental implications for an understanding of slip heterogeneity and the behavior of the rupture process.

Finite-Element Analysis of Melt Flow in Horizontal Twin-Roll Casting of Magnesium Alloy AZ31

NASA Astrophysics Data System (ADS)

Park, Jong-Jin

Twin-roll casting has been useful in production of thin strips of metals. Especially, the process of horizontal twin-roll casting is often used for magnesium and aluminum alloys, which are lighter in weight and smaller in specific heat as well as latent heat in comparison to steel. In the present investigation, where magnesium alloy AZ31 was targeted, asymmetric behavior of the melt flow due to the gravity was examined in terms of contact length and pressure, and the nozzle for melt ejection was modified for its shape and location. Variations of the melt flow including vortexes were investigated in consideration of heterogeneous nucleation and uniform microstructure. The melt flow was further examined in the perspective of possible randomness of the grain orientation through thickness under differential speeds of rolls.

Direct measurement of wall slip and slip layer thickness of non-Brownian hard-sphere suspensions in rectangular channel flows

NASA Astrophysics Data System (ADS)

Jesinghausen, Steffen; Weiffen, Rene; Schmid, Hans-Joachim

2016-09-01

Wall slip is a long-known phenomenon in the field of rheology. Nevertheless, the origin and the evolution are not completely clear yet. Regarding suspensions, the effect becomes even more complicated, because different mechanisms like pure slip or slip due to particle migration have to be taken into account. Furthermore, suspensions themselves show many flow anomalies and the isolation of slip is complicated. In order to develop working physical models, further insight is necessary. In this work, we measured experimentally the wall slip velocities of different highly filled suspensions in a rectangular slit die directly with respect to the particle concentration and the particle size. The slip velocities were obtained using a particle image velocimetry (PIV) system. The suspensions consisting of a castor oil-cinnamon oil blend and PMMA particles were matched in terms of refractive indexes to appear transparent. Hereby, possible optical path lengths larger than 15 mm were achieved. The slip velocities were found to be in a quadratic relation to the wall shear stress. Furthermore, the overall flow rate as well as the particle concentration has a direct influence on the slip. Concerning the shear stress, there seem to be two regions of slip with different physical characteristics. Furthermore, we estimated the slip layer thickness directly from the velocity profiles and propose a new interpretation. The PIV technique is used to investigate the viscosity and implicit the concentration profile in the slit die. It is shown that the particle migration process is quite fast.

Tempering Behavior of TiC-Reinforced SKD11 Steel Matrix Composite

NASA Astrophysics Data System (ADS)

Hwang, Ji-In; Kim, Seong Hoon; Heo, Yoon-Uk; Kim, Dae Ha; Hwang, Keum-Cheol; Suh, Dong-Woo

2018-05-01

TiC-reinforced SKD11 steel matrix composite, fabricated by a pressure infiltration casting, undergoes monotonic decrease in hardness as tempering temperature increases. Element mappings by TEM-EDS and thermodynamic calculation indicate that remarkable redistribution of V between the reinforcement and the steel matrix occurs by partial dissolution and re-precipitation of MC carbides upon casting process. The absence of secondary hardening is led by the enrichment of V in the reinforcement that reduces the V content in the steel matrix; this reduction in V content makes the precipitation of fine VC sluggish during the tempering.

Improved Sand-Compaction Method for Lost-Foam Metal Casting

NASA Technical Reports Server (NTRS)

Bakhtiyarov, Sayavur I.; Overfelt, Ruel A.

2008-01-01

An improved method of filling a molding flask with sand and compacting the sand around a refractory-coated foam mold pattern has been developed for incorporation into the lost-foam metal-casting process. In comparison with the conventional method of sand filling and compaction, this method affords more nearly complete filling of the space around the refractory-coated foam mold pattern and more thorough compaction of the sand. In so doing, this method enables the sand to better support the refractory coat under metallostatic pressure during filling of the mold with molten metal.

Manufacturing technology methodology for propulsion system parts

NASA Astrophysics Data System (ADS)

McRae, M. M.

1992-07-01

A development history and a current status evaluation are presented for lost-wax casting of such gas turbine engine components as turbine vanes and blades. The most advanced such systems employ computer-integrated manufacturing methods for high process repeatability, reprogramming versatility, and feedback monitoring. Stereolithography-based plastic model 3D prototyping has also been incorporated for the wax part of the investment casting; it may ultimately be possible to produce the 3D prototype in wax directly, or even to create a ceramic mold directly. Nonintrusive inspections are conducted by X-radiography and neutron radiography.

Non-graphite crucible for high temperature applications

DOEpatents

Holcombe, C.E.; Pfeiler, W.A.

1996-01-09

A multi-piece crucible for high temperature applications comprises a tubular side wall member having a lip on the inside surface and a bottom member or members forming a container for containing a melt of a material during a high temperature melt-casting operations. The multi-piece design prevents cracking of the crucible or leakage of the melt from the crucible during the melt-casting operation. The lip of the tubular member supports the bottom member. The contacting surfaces where the lip of the tubular side wall member contacts the bottom member of the multi-piece crucible contains a ceramic sealing material. The ceramic sealing material forms a seal sufficient to prevent the melt of the material from leaking out of the multi-piece crucible during the melt-casting process. The multi-piece crucible is made of a material which is chemically inert to the melt and has structural integrity at the melting point temperature of the melt, or of a material coated with such a material. The multi-piece crucible is contained in a thermal can assembly of a high temperature induction furnace during a high temperature melt-casting operation. One embodiment of the multi-piece crucible comprises a tubular member having a vertical slot filled with a ceramic sealing material to provide expansion of the tubular member without cracking during the high temperature melt-casting operation. 9 figs.

Ohno continuous casting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soda, H.; McLean, A.; Motoyasu, G.

1995-04-01

Production of net-shape products directly from the liquid is an attractive manufacturing route for alloys that are difficult to process or that cannot be rolled, drawn, or extruded. Developed at the Chiba Institute of Technology in Japan, the Ohno Continuous Casting (OCC) approach not only provides significant cost savings, but also has the potential to create new products. OCC process equipment includes a melting furnace, crucible, mold level-control block, cooling device, and pinch rolls. OCC is currently used to produce copper rods and wires for audio and video cables, and aluminum alloy welding rods for hard-surfacing applications. For example, Mitsuimore » Engineering and Ship Building Co. has used OCC to produce copper tubing products with internal fins and partitions for applications such as heat exchanger tubes and induction coils.« less

Repeated drainage from megathrusts during episodic slow slip

NASA Astrophysics Data System (ADS)

Nakajima, Junichi; Uchida, Naoki

2018-05-01

Pore-fluid pressure levels are considered to regulate the frictional strength and slip behaviour at megathrusts, where the largest earthquakes on Earth occur. Some analyses have suggested that the breaking of permeability seals during megathrust earthquakes causes subsequent drainage from the megathrust. However, it is poorly understood whether drainage follows frequent occurrences of episodic slow slip events. Here we analyse seismic waveform data beneath Kanto, Japan, for the period from 2004 to 2015 and show that seismicity rates and seismic attenuation above the megathrust of the Philippine Sea slab change cyclically in response to accelerated slow slip. These observations are interpreted to represent intensive drainage during slow slip events that repeat at intervals of approximately one year and subsequent migration of fluids into the permeable overlying plate. Our observations suggest that if slow slip events occur under an impermeable overlying plate, fluids draining due to slow slip events could be forced to channel within the megathrust, potentially enhancing pore-fluid pressure at an up-dip, locked seismogenic megathrust. This process might increase the potential to trigger large earthquakes near slow slip areas. Although stress transfer is recognized as an important factor for triggering megathrust failure, fluid transfer accompanied by episodic slow slip events will thus play an additional and crucial part in megathrust weakening.

Evaluating the Tensile Properties of Aluminum Foundry Alloys through Reference Castings—A Review

PubMed Central

Anilchandra, A.R.; Arnberg, Lars; Bonollo, Franco; Fiorese, Elena

2017-01-01

The tensile properties of an alloy can be exploited if detrimental defects and imperfections of the casting are minimized and the microstructural characteristics are optimized through several strategies that involve die design, process management and metal treatments. This paper presents an analysis and comparison of the salient characteristics of the reference dies proposed in the literature, both in the field of pressure and gravity die-casting. The specimens produced with these reference dies, called separately poured specimens, are effective tools for the evaluation and comparison of the tensile and physical behaviors of Al-Si casting alloys. Some of the findings of the present paper have been recently developed in the frame of the European StaCast project whose results are complemented here with some more recent outcomes and a comprehensive analysis and discussion. PMID:28867796

Pseudotachylyte increases the post-slip strength of faults

USGS Publications Warehouse

Proctor, Brooks; Lockner, David A.

2016-01-01

Solidified frictional melts, or pseudotachylytes, are observed in exhumed faults from across the seismogenic zone. These unique fault rocks, and many experimental studies, suggest that frictional melting can be an important process during earthquakes. However, it remains unknown how melting affects the post-slip strength of the fault and why many exhumed faults do not contain pseudotachylyte. Analyses of triaxial stick-slip events on Westerly Granite (Rhode Island, USA) sawcuts at confining pressures from 50 to 400 MPa show evidence for frictional heating, including some events energetic enough to generate surface melt. Total and partial stress drops were observed with slip as high as 6.5 mm. We find that in dry samples following melt-producing stick slip, the shear failure strength increased as much as 50 MPa, while wet samples had <10 MPa strengthening. Microstructural analysis indicates that the strengthening is caused by welding of the slip surface during melt quenching, suggesting that natural pseudotachylytes may also strengthen faults after earthquakes. These results predict that natural pseudotachylyte will inhibit slip reactivation and possibly generate stress heterogeneities along faults. Wet samples do not exhibit melt welding, possibly because of thermal pressurization of water reducing frictional heating during slip.

Evaluating the Tensile Properties of Aluminum Foundry Alloys through Reference Castings-A Review.

PubMed

Anilchandra, A R; Arnberg, Lars; Bonollo, Franco; Fiorese, Elena; Timelli, Giulio

2017-08-30

The tensile properties of an alloy can be exploited if detrimental defects and imperfections of the casting are minimized and the microstructural characteristics are optimized through several strategies that involve die design, process management and metal treatments. This paper presents an analysis and comparison of the salient characteristics of the reference dies proposed in the literature, both in the field of pressure and gravity die-casting. The specimens produced with these reference dies, called separately poured specimens, are effective tools for the evaluation and comparison of the tensile and physical behaviors of Al-Si casting alloys. Some of the findings of the present paper have been recently developed in the frame of the European StaCast project whose results are complemented here with some more recent outcomes and a comprehensive analysis and discussion.

Food equipment manufacturer takes a slice out of its scrap rate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernard, D.; Hannahs, J.; Carter, M.

1996-09-01

The PMI Food Equipment Group began manufacturing circular slicer knives for its commercial Hobart line of slicers in the early 1930s. The company manufacturers the only cast knife in the food industry. The cast knives offer superior edge retention and overall corrosion resistance. The slicer knives are cast in PMI`s foundry. The casting process sometimes produces shrinkage voids or gas bubbles in the knife blank. Surface discontinuities often do not appear until rough cutting or final machining, i.e., after several hours of value-added manufacturing. Knife blanks with these discontinuities were scrapped and sent back to the foundry for remelting. Tomore » scrap the knives at that point meant the cost for casting plus the value-added machining added up to a considerable amount. Weld repair allows the recovery of casting and machining expenses equal to a significant percentage of the total manufacturing cost of slicer knives. Repair costs include welding, grinding, shipping, surface finishing and material handling. Other good applications for this GMAW-P process include repair of jet engine components, rotating process industry equipment, and hardfacing of cutting tools and dies. In addition, dissimilar metals and any material that is heat treated to develop its properties such as precision investment castings are excellent applications. The low resultant distortion, elimination of postweld heat treatment and non-line-of-site welding capability solves thin wall, limited access and precision machined component repair challenges.« less

Slow slip events and seismic tremor at circum-Pacific subduction zones

NASA Astrophysics Data System (ADS)

Schwartz, Susan Y.; Rokosky, Juliana M.

2007-09-01

It has been known for a long time that slip accompanying earthquakes accounts for only a fraction of plate tectonic displacements. However, only recently has a fuller spectrum of strain release processes, including normal, slow, and silent earthquakes (or slow slip events) and continuous and episodic slip, been observed and generated by numerical simulations of the earthquake cycle. Despite a profusion of observations and modeling studies the physical mechanism of slow slip events remains elusive. The concurrence of seismic tremor with slow slip episodes in Cascadia and southwestern Japan provides insight into the process of slow slip. A perceived similarity between subduction zone and volcanic tremor has led to suggestions that slow slip involves fluid migration on or near the plate interface. Alternatively, evidence is accumulating to support the notion that tremor results from shear failure during slow slip. Global observations of the location, spatial extent, magnitude, duration, slip rate, and periodicity of these aseismic slip transients indicate significant variation that may be exploited to better understand their generation. Most slow slip events occur just downdip of the seismogenic zone, consistent with rate- and state-dependent frictional modeling that requires unstable to stable transitional properties for slow slip generation. At a few convergent margins the occurrence of slow slip events within the seismogenic zone makes it highly likely that transitions in frictional properties exist there and are the loci of slow slip nucleation. Slow slip events perturb the surrounding stress field and may either increase or relieve stress on a fault, bringing it closer to or farther from earthquake failure, respectively. This paper presents a review of slow slip events and related seismic tremor observed at plate boundaries worldwide, with a focus on circum-Pacific subduction zones. Trends in global observations of slow slip events suggest that (1) slow slip is a common phenomena observed at almost all subduction zones with instrumentation capable of recording it, (2) different frictional properties likely control fast versus slow slip, (3) the depth range of slow slip may be related to the thermal properties of the plate interface, and (4) the equivalent seismic moment of slow slip events is proportional to their duration (Moατ), different from the Moατ3 scaling observed for earthquakes.

Microstructural and mechanical evolutions during the forging step of the COBAPRESS, a casting/forging process

NASA Astrophysics Data System (ADS)

Perrier, Frédéric; Desrayaud, Christophe; Bouvier, Véronique

Aluminum casting/forging processes are used to produce parts for the automotive industry. In this study, we examined the influence of the forging step on the microstructure and the mechanical properties of an A356 aluminum alloy modified with strontium. Firstly, a design of samples which allows us to test mechanically the alloy before and after forging was created. A finite element analysis with the ABAQUS software predicts a maximum of strain in the core of the specimens. Observations with the EBSD technique confirm a more intense sub-structuration of the dendrite cells in this zone. Yield strength, ultimate tensile strength, elongation and fatigue lives were then improved for the casting/forging samples compared to the only cast specimens. The closure of the porosities and the improvement of the surface quality during the forging step enhance also the fatigue resistance of the samples.

The influence of flushing time on the bonding quality of liquid white cast iron on the solid surface of similar material

NASA Astrophysics Data System (ADS)

Bandanadjaja, Beny; Purwadi, Wiwik; Idamayanti, Dewi; Lilansa, Noval; Hanaldi, Kus; Nurzaenal, Friya Kurnia

2018-05-01

Hard metal castings are widely used in the coal mill pulverizer as construction material for coal crushers. During its operation crushers and mills experience degradation caused by abrasion load. This research dealed with the surface overlaying of similiar material on the surface of white cast iron by mean of gravity casting. The die blank casting was preheated prior to the casting process of outer layer made of Ni-Hard white cast iron to guarantee bonding processes and avoid any crack. The preheating temperature of die blankin ther range of 500C up to 850C was set up to reach the interface temperature in the range of 887°C -1198°C and the flushing time was varied between 10-20 seconds. Studies carried on the microstructure of sample material revealed a formation of metallurgical bonding at the preheating temperature above 625 °C by pouring temperature ranging from 1438 °C to 1468 °C. Metallographical and chemical composition by mean of EDS examination were performed to observed the resut. This research concludes that the casting of Ni-Hard 1 overlay by applying gravity casting method can be done by preheating the surface of casting to 625 °C, interface temperature of 1150 °C, flushing time of 7 seconds and pouring temperature of 1430 °C. Excellent metallurgical bonding at the contact area between dieblank and overlay material has been achieved in which there is no parting line at the interface area to be observed.

Comparison of marginal accuracy of castings fabricated by conventional casting technique and accelerated casting technique: an in vitro study.

PubMed

Reddy, S Srikanth; Revathi, Kakkirala; Reddy, S Kranthikumar

2013-01-01

Conventional casting technique is time consuming when compared to accelerated casting technique. In this study, marginal accuracy of castings fabricated using accelerated and conventional casting technique was compared. 20 wax patterns were fabricated and the marginal discrepancy between the die and patterns were measured using Optical stereomicroscope. Ten wax patterns were used for Conventional casting and the rest for Accelerated casting. A Nickel-Chromium alloy was used for the casting. The castings were measured for marginal discrepancies and compared. Castings fabricated using Conventional casting technique showed less vertical marginal discrepancy than the castings fabricated by Accelerated casting technique. The values were statistically highly significant. Conventional casting technique produced better marginal accuracy when compared to Accelerated casting. The vertical marginal discrepancy produced by the Accelerated casting technique was well within the maximum clinical tolerance limits. Accelerated casting technique can be used to save lab time to fabricate clinical crowns with acceptable vertical marginal discrepancy.

The evolving interaction of low-frequency earthquakes during transient slip.

PubMed

Frank, William B; Shapiro, Nikolaï M; Husker, Allen L; Kostoglodov, Vladimir; Gusev, Alexander A; Campillo, Michel

2016-04-01

Observed along the roots of seismogenic faults where the locked interface transitions to a stably sliding one, low-frequency earthquakes (LFEs) primarily occur as event bursts during slow slip. Using an event catalog from Guerrero, Mexico, we employ a statistical analysis to consider the sequence of LFEs at a single asperity as a point process, and deduce the level of time clustering from the shape of its autocorrelation function. We show that while the plate interface remains locked, LFEs behave as a simple Poisson process, whereas they become strongly clustered in time during even the smallest slow slip, consistent with interaction between different LFE sources. Our results demonstrate that bursts of LFEs can result from the collective behavior of asperities whose interaction depends on the state of the fault interface.

Investigation on Bond-Slip Behavior of Z-Pin Interfaces in X-Cor® Sandwich Structures Using Z-Pin Pull-Out Test

NASA Astrophysics Data System (ADS)

Shan, Hangying; Xiao, Jun; Chu, Qiyi

2018-05-01

The Z-Pin interfacial bond properties play an important role in the structural performance of X-Cor® sandwich structures. This paper presents an experimental investigation on bond-slip behavior of Z-Pin interfaces using Z-Pin pull-out test. Based on the experimental data the whole Z-Pin pull-out process consists of three stages: initial bonding, debonding and frictional sliding. Comparative experimental study on the influence of design parameters on bond-slip behavior of Z-Pin interfaces has also been performed. Numerical analyses were conducted with the ABAQUS finite element (FE) program to simulate the Z-Pins bond-slip response of the pull-out test. The Z-Pins interfacial bond-slip behavior was implemented using nonlinear spring elements characterized with the constitutive relation from experimental results. Numerical results were validated by comparison with experimental data, and reasonably good agreement was achieved between experimental and analytical pull-out force-slip curves.

Non-graphite crucible for high temperature applications

DOEpatents

Holcombe, Cressie E.; Pfeiler, William A.

1996-01-01

A multi-piece crucible for high temperature applications comprises a tubular side wall member having a lip on the inside surface and a bottom member or members forming a container for containing a melt of a material during a high temperature melt-casting operations. The multi-piece design prevents cracking of the crucible or leakage of the melt from the crucible during the melt-casting operation. The lip of the tubular member supports the bottom member. The contacting surfaces where the lip of the tubular side wall member contacts the bottom member of the multi-piece crucible contains a ceramic sealing material. The ceramic sealing material forms a seal sufficient to prevent the melt of the material from leaking out of the multi-piece crucible during the melt-casting process. The multi-piece crucible is made of a material which is chemically inert to the melt and has structural integrity at the melting point temperature of the melt, or of a material coated with such a material. The multi-piece crucible is contained in a thermal can assembly of a high temperature induction furnace during a high temperature melt-casting operation. One embodiment of the multi-piece crucible comprises a tubular member having a vertical slot filled with a ceramic sealing material to provide expansion of the tubular member without cracking during the high temperature melt-casting operation.

Reverse freeze casting: a new method for fabricating highly porous titanium scaffolds with aligned large pores.

PubMed

Yook, Se-Won; Jung, Hyun-Do; Park, Chang-Hoon; Shin, Kwan-Ha; Koh, Young-Hag; Estrin, Yuri; Kim, Hyoun-Ee

2012-07-01

Highly porous titanium with aligned large pores up to 500 μm in size, which is suitable for scaffold applications, was successfully fabricated using the reverse freeze casting method. In this process we have newly developed, the Ti powders migrated spontaneously along the pre-aligned camphene boundaries at a temperature of 45.5°C and formed a titanium-camphene mixture with an aligned structure; this was followed by freeze drying and sintering. As the casting time increased from 24 to 48 h, the initial columnar structures turned into lamellar structures, with the porosity decreasing from 69 to 51%. This reduction in porosity caused the compressive yield strength to increase from 121 to 302 MPa, with an elastic modulus of the samples being in the range of 2-5 GPa. In addition, it was demonstrated that reverse freeze casting can also be successfully applied to various other raw powders, suggesting that the method developed in this work opens up new avenues for the production of a range of porous metallic and ceramic scaffolds with highly aligned pores. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Modeling of Dendritic Evolution of Continuously Cast Steel Billet with Cellular Automaton

NASA Astrophysics Data System (ADS)

Wang, Weiling; Ji, Cheng; Luo, Sen; Zhu, Miaoyong

2018-02-01

In order to predict the dendritic evolution during the continuous steel casting process, a simple mechanism to connect the heat transfer at the macroscopic scale and the dendritic growth at the microscopic scale was proposed in the present work. As the core of the across-scale simulation, a two-dimensional cell automaton (CA) model with a decentered square algorithm was developed and parallelized. Apart from nucleation undercooling and probability, a temperature gradient was introduced to deal with the columnar-to-equiaxed transition (CET) by considering its variation during continuous casting. Based on the thermal history, the dendritic evolution in a 4 mm × 40 mm region near the centerline of a SWRH82B steel billet was predicted. The influences of the secondary cooling intensity, superheat, and casting speed on the dendritic structure of the billet were investigated in detail. The results show that the predicted equiaxed dendritic solidification of Fe-5.3Si alloy and columnar dendritic solidification of Fe-0.45C alloy are consistent with in situ experimental results [Yasuda et al. Int J Cast Metals Res 22:15-21 (2009); Yasuda et al. ISIJ Int 51:402-408 (2011)]. Moreover, the predicted dendritic arm spacing and CET location agree well with the actual results in the billet. The primary dendrite arm spacing of columnar dendrites decreases with increasing secondary cooling intensity, or decreasing superheat and casting speed. Meanwhile, the CET is promoted as the secondary cooling intensity and superheat decrease. However, the CET is not influenced by the casting speed, owing to the adjusting of the flow rate of secondary spray water. Compared with the superheat and casting speed, the secondary cooling intensity can influence the cooling rate and temperature gradient in deeper locations, and accordingly exerts a more significant influence on the equiaxed dendritic structure.

FEA and microstructure characterization of a one-piece Y-TZP abutment.

PubMed

da Silva, Lucas Hian; Ribeiro, Sebastião; Borges, Alexandre Luís Souto; Cesar, Paulo Francisco; Tango, Rubens Nisie

2014-11-01

The most important drawback of dental implant/abutment assemblies is the need for a fixing screw. This study aimed to develop an esthetic one-piece Y-TZP abutment to suppress the use of the screw. Material characterization was performed using a bar-shaped specimen obtained by slip-casting to validate the method prior to prototype abutment fabrication by the same process. The mechanical behavior of the prototype abutment was verified and compared with a conventional abutment by finite element analysis (FEA). The abutment was evaluated by micro-CT analysis and its density was measured. FEA showed stress concentration at the first thread pitch during installation and in the cervical region during oblique loading for both abutments. However, stress concentration was observed at the base of the screw head and stem in the conventional abutment. The relative density for the fabricated abutment was 95.68%. Micro-CT analysis revealed the presence of elongated cracks with sharp edges over the surface and porosity in the central region. In the light of these findings, the behavior of a one-piece abutment is expected to be better than that of the conventional model. New studies should be conducted to clarify the performance and longevity of this one-piece Y-TZP abutment. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Electronic gap sensor and method

DOEpatents

Williams, Robert S.; King, Edward L.; Campbell, Steven L.

1991-01-01

An apparatus and method for regulating the gap between a casting nozzle and a casting wheel in which the gap between the casting nozzle and the casting wheel is monitored by means of at least one sensing element protruding from the face of the casting nozzle. The sensing element is preferably connected to a voltage source and the casting wheel grounded. When the sensing element contacts the casting wheel, an electric circuit is completed. The completion of the circuit can be registered by an indicator, and the presence or absence of a completed circuit indicates the relative position of the casting nozzle to the casting wheel. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces.

Phosphorus Segregation in Meta-Rapidly Solidified Carbon Steels

NASA Astrophysics Data System (ADS)

Li, Na; Qiao, Jun; Zhang, Junwei; Sha, Minghong; Li, Shengli

2017-09-01

Twin-roll strip casters for near-net-shape manufacture of steels have received increased attention in the steel industry. Although negative segregation of phosphorus occurred in twin-roll strip casting (TRSC) steels in our prior work, its mechanism is still unclear. In this work, V-shaped molds were designed and used to simulate a meta-rapid solidification process without roll separating force during twin roll casting of carbon steels. Experimental results show that no obvious phosphorus segregation exist in the V-shaped mold casting (VMC) steels. By comparing TRSC and the VMC, it is proposed that the negative phosphorus segregation during TRSC results from phosphorus redistribution driven by recirculating and vortex flow in the molten pool. Meanwhile, solute atoms near the advancing interface are overtaken and incorporated into the solid because of the high solidification speed. The high rolling force could promote the negative segregation of alloying elements in TRSC.

Reproducibility of ZrO2-based freeze casting for biomaterials.

PubMed

Naleway, Steven E; Fickas, Kate C; Maker, Yajur N; Meyers, Marc A; McKittrick, Joanna

2016-04-01

The processing technique of freeze casting has been intensely researched for its potential to create porous scaffold and infiltrated composite materials for biomedical implants and structural materials. However, in order for this technique to be employed medically or commercially, it must be able to reliably produce materials in great quantities with similar microstructures and properties. Here we investigate the reproducibility of the freeze casting process by independently fabricating three sets of eight ZrO2-epoxy composite scaffolds with the same processing conditions but varying solid loading (10, 15 and 20 vol.%). Statistical analyses (One-way ANOVA and Tukey's HSD tests) run upon measurements of the microstructural dimensions of these composite scaffold sets show that, while the majority of microstructures are similar, in all cases the composite scaffolds display statistically significant variability. In addition, composite scaffolds where mechanically compressed and statistically analyzed. Similar to the microstructures, almost all of their resultant properties displayed significant variability though most composite scaffolds were similar. These results suggest that additional research to improve control of the freeze casting technique is required before scaffolds and composite scaffolds can reliably be reproduced for commercial or medical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Slip Distribution of the 2011 Tohoku-oki Earthquake obtained by Geodetic and Tsunami Data and with a 3-D Finite Element Model

NASA Astrophysics Data System (ADS)

Romano, F.; Trasatti, E.; Lorito, S.; Ito, Y.; Piatanesi, A.; Lanucara, P.; Hirata, K.; D'Agostino, N.; Cocco, M.

2012-12-01

The rupture process of the Great 2011 Tohoku-oki earthquake has been particularly well studied by using an unprecedented collection of geophysical data. There is a general agreement among the different source models obtained by modeling seismological, geodetic and tsunami data. A slip patch of nearly 40÷50 meters has been imaged and located around and up-dip from the hypocenter by most of published models, while some differences exist in the slip pattern retrieved at shallow depths near the trench, likely due to the different resolving power of distinct data sets and to the adopted fault geometry. It is well known that the modeling of great subduction earthquakes requires the use of 3-D structural models in order to properly account for the effects of topography, bathymetry and the geometrical variations of the plate interface as well as for the effects of elastic contrasts between the subducting plate and the continental lithosphere. In this study we build a 3-D Finite Element (FE) model of the Tohoku-oki area in order to infer the slip distribution of the 2011 earthquake by performing a joint inversion of geodetic (GPS and seafloor observations) and tsunami (ocean bottom pressure sensors, DART and GPS buoys) data. The FE model is used to compute the geodetic and tsunami Green's functions. In order to understand how geometrical and elastic heterogeneities control the inferred slip distribution of the Tohoku-oki earthquake, we compare the slip patterns obtained using both homogeneous and heterogeneous structural models. The goal of this study is to better constrain the slip distribution and the maximum slip amplitudes. In particular, we aim to focus on the rupture process in the shallower part of the fault plane and near the trench, which is crucial to model the tsunami data and to assess the tsunamigenic potential of earthquakes in this region.

Tape casting and partial melting of Bi-2212 thick films

NASA Technical Reports Server (NTRS)

Buhl, D.; Lang, TH.; Heeb, B.; Gauckler, L. J.

1995-01-01

To produce Bi-2212 thick films with high critical current densities tape casting and partial melting is a promising fabrication method. Bi-2212 powder and organic additives were mixed into a slurry and tape casted onto glass by the doctor blade tape casting process. The films were cut from the green tape and partially molten on Ag foils during heat treatment. We obtained almost single-phase and well-textured films over the whole thickness of 20 microns. The orientation of the (a,b)-plane of the grains was parallel to the substrate with a misalignment of less than 6 deg. At 77 K/0T a critical current density of 15, 000 A/sq cm was reached in films of the dimension 1 cm x 2 cm x 20 microns (1 micron V/cm criterion, resistively measured). At 4 K/0T the highest value was 350,000 A/sq cm (1 nV/cm criterion, magnetically measured).

Curaua and eucalyptus nanofibers films by continuous casting: Mechanical and thermal properties.

PubMed

Claro, Pedro Ivo Cunha; Corrêa, Ana Carolina; de Campos, Adriana; Rodrigues, Vanessa Bolzan; Luchesi, Bruno Ribeiro; Silva, Luiz Eduardo; Mattoso, Luiz Henrique Capparelli; Marconcini, José Manoel

2018-02-01

A wide variety of new green materials such as curaua leaf fibers (CLFs) has potential applications in nanotechnology. This study aims to investigate the thermomechanical properties and morphological structure of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) films obtained by continuous casting. The CNCs were obtained by acid hydrolysis and CNFs by mechanical shearing from bleached CLFs and eucalyptus pulp. The morphology after continuous casting resulted in oriented nanofibers, and as a consequence there was mechanical anisotropy. CNCs films showed the greatest values of tensile strength (36±4MPa) and the more effective fibrillation provided better mechanical strength of eucalyptus CNFs films than curaua CNFs films. Sulfur groups and mechanical shear degradation affected the stability of CNCs and CNFs films, respectively. Thus, the type of nanostructure, the way they interact to each other, the cellulose source and the process interfere significantly on the properties of the films. Copyright © 2017 Elsevier Ltd. All rights reserved.

Systematic Observations of the Slip-pulse Properties of Large Earthquake Ruptures

NASA Astrophysics Data System (ADS)

Melgar, D.; Hayes, G. P.

2017-12-01

In earthquake dynamics there are two end member models of rupture: propagating cracks and self-healing pulses. These arise due to different properties of ruptures and have implications for seismic hazard; rupture mode controls near-field strong ground motions. Past studies favor the pulse-like mode of rupture, however, due to a variety of limitations, it has proven difficult to systematically establish their kinematic properties. Here we synthesize observations from a database of >150 rupture models of earthquakes spanning M7-M9 processed in a uniform manner and show the magnitude scaling properties (rise time, pulse width, and peak slip rate) of these slip pulses indicates self-similarity. Self similarity suggests a weak form of rupture determinism, where early on in the source process broader, higher amplitude slip pulses will distinguish between events of icnreasing magnitude. Indeed, we find by analyzing the moment rate functions that large and very large events are statistically distinguishable relatively early (at 15 seconds) in the rupture process. This suggests that with dense regional geophysical networks strong ground motions from a large rupture can be identified before their onset across the source region.

Method For Removing Volatile Components From A Gel-Cast Ceramic Article

DOEpatents

Klug, Frederic Joseph; DeCarr, Sylvia Marie

2004-09-07

A method of removing substantially all of the volatile component in a green, volatile-containing ceramic article is disclosed. The method comprises freezing the ceramic article; and then subjecting the frozen article to a vacuum for a sufficient time to freeze-dry the article. Frequently, the article is heated while being freeze-dried. Use of this method efficiently reduces the propensity for any warpage of the article. The article is often formed from a ceramic slurry in a gel-casting process. A method for fabricating a ceramic core used in investment casting is also described.

Analytical Solution of Displacements Around Circular Openings in Generalized Hoek-Brown Rocks

NASA Astrophysics Data System (ADS)

Huang, Houxu; Li, Jie; Wei, Jiuqi

2017-09-01

The rock in plastic region is divided into numbers of elements by the slip lines, resulted from shear localization. During the deformation process, the elements will slip along the slip lines and the displacement field is discontinuous. Slip lines around circular opening in isotropic rock, subjected to hydrostatic stress are described by the logarithmic spirals. Deformation of the plastic region is mainly attributed to the slippage. Relationship between the shear stresses and slippage on slip lines is presented, based on the study of Revuzhenko and Shemyakin. Relations between slippage and rock failure are described, based on the elastic-brittle-plastic model. An analytical solution is presented for the plane strain analysis of displacements around circular openings in the Generalized Hoek-Brown rock. With properly choosing of slippage parameters, results obtained by using the proposed solution agree well with those presented in published sources.

Numerical Simulation and Optimization of Directional Solidification Process of Single Crystal Superalloy Casting

PubMed Central

Zhang, Hang; Xu, Qingyan; Liu, Baicheng

2014-01-01

The rapid development of numerical modeling techniques has led to more accurate results in modeling metal solidification processes. In this study, the cellular automaton-finite difference (CA-FD) method was used to simulate the directional solidification (DS) process of single crystal (SX) superalloy blade samples. Experiments were carried out to validate the simulation results. Meanwhile, an intelligent model based on fuzzy control theory was built to optimize the complicate DS process. Several key parameters, such as mushy zone width and temperature difference at the cast-mold interface, were recognized as the input variables. The input variables were functioned with the multivariable fuzzy rule to get the output adjustment of withdrawal rate (v) (a key technological parameter). The multivariable fuzzy rule was built, based on the structure feature of casting, such as the relationship between section area, and the delay time of the temperature change response by changing v, and the professional experience of the operator as well. Then, the fuzzy controlling model coupled with CA-FD method could be used to optimize v in real-time during the manufacturing process. The optimized process was proven to be more flexible and adaptive for a steady and stray-grain free DS process. PMID:28788535

Casting Technology.

ERIC Educational Resources Information Center

Wright, Michael D.; And Others

1992-01-01

Three articles discuss (1) casting technology as it relates to industry, with comparisons of shell casting, shell molding, and die casting; (2) evaporative pattern casting for metals; and (3) high technological casting with silicone rubber. (JOW)

Additive manufacturing of biologically-inspired materials.

PubMed

Studart, André R

2016-01-21

Additive manufacturing (AM) technologies offer an attractive pathway towards the fabrication of functional materials featuring complex heterogeneous architectures inspired by biological systems. In this paper, recent research on the use of AM approaches to program the local chemical composition, structure and properties of biologically-inspired materials is reviewed. A variety of structural motifs found in biological composites have been successfully emulated in synthetic systems using inkjet-based, direct-writing, stereolithography and slip casting technologies. The replication in synthetic systems of design principles underlying such structural motifs has enabled the fabrication of lightweight cellular materials, strong and tough composites, soft robots and autonomously shaping structures with unprecedented properties and functionalities. Pushing the current limits of AM technologies in future research should bring us closer to the manufacturing capabilities of living organisms, opening the way for the digital fabrication of advanced materials with superior performance, lower environmental impact and new functionalities.

Energy requirement for the production of silicon solar arrays

NASA Technical Reports Server (NTRS)

Lindmayer, J.; Wihl, M.; Scheinine, A.; Morrison, A.

1977-01-01

An assessment of potential changes and alternative technologies which could impact the photovoltaic manufacturing process is presented. Topics discussed include: a multiple wire saw, ribbon growth techniques, silicon casting, and a computer model for a large-scale solar power plant. Emphasis is placed on reducing the energy demands of the manufacturing process.

Development of automated system based on neural network algorithm for detecting defects on molds installed on casting machines

NASA Astrophysics Data System (ADS)

Bazhin, V. Yu; Danilov, I. V.; Petrov, P. A.

2018-05-01

During the casting of light alloys and ligatures based on aluminum and magnesium, problems of the qualitative distribution of the metal and its crystallization in the mold arise. To monitor the defects of molds on the casting conveyor, a camera with a resolution of 780 x 580 pixels and a shooting rate of 75 frames per second was selected. Images of molds from casting machines were used as input data for neural network algorithm. On the preparation of a digital database and its analytical evaluation stage, the architecture of the convolutional neural network was chosen for the algorithm. The information flow from the local controller is transferred to the OPC server and then to the SCADA system of foundry. After the training, accuracy of neural network defect recognition was about 95.1% on a validation split. After the training, weight coefficients of the neural network were used on testing split and algorithm had identical accuracy with validation images. The proposed technical solutions make it possible to increase the efficiency of the automated process control system in the foundry by expanding the digital database.

Relating stick-slip friction experiments to earthquake source parameters

USGS Publications Warehouse

McGarr, Arthur F.

2012-01-01

Analytical results for parameters, such as static stress drop, for stick-slip friction experiments, with arbitrary input parameters, can be determined by solving an energy-balance equation. These results can then be related to a given earthquake based on its seismic moment and the maximum slip within its rupture zone, assuming that the rupture process entails the same physics as stick-slip friction. This analysis yields overshoots and ratios of apparent stress to static stress drop of about 0.25. The inferred earthquake source parameters static stress drop, apparent stress, slip rate, and radiated energy are robust inasmuch as they are largely independent of the experimental parameters used in their estimation. Instead, these earthquake parameters depend on C, the ratio of maximum slip to the cube root of the seismic moment. C is controlled by the normal stress applied to the rupture plane and the difference between the static and dynamic coefficients of friction. Estimating yield stress and seismic efficiency using the same procedure is only possible when the actual static and dynamic coefficients of friction are known within the earthquake rupture zone.

Joint Inversion of Borehole Strainmeter and GPS Time Series for Slip and Stress Distribution during Cascadian ETS

NASA Astrophysics Data System (ADS)

Benz, N.; Bartlow, N. M.

2017-12-01

The addition of borehole strainmeter (BSM) to cGPS time series inversions can yield more precise slip distributions at the subduction interface during episodic tremor and slip (ETS) events in the Cascadia subduction zone. Traditionally very noisy BSM data has not been easy to incorporate until recently, but developments in processing noise, re-orientation of strain components, removal of tidal, hydrologic, and atmospheric signals have made this additional source of data viable (Roeloffs, 2010). The major advantage with BSMs is their sensitivity to spatial derivatives in slip, which is valuable for investigating the ETS nucleation process and stress changes on the plate interface due to ETS. Taking advantage of this, we simultaneously invert PBO GPS and cleaned BSM time series with the Network Inversion Filter (Segall and Matthews, 1997) for slip distribution and slip rate during selected Cascadia ETS events. Stress distributions are also calculated for the plate interface using these inversion results to estimate the amount of stress change during an ETS event. These calculations are performed with and without the utilization of BSM time series, highlighting the role of BSM data in constraining slip and stress.

Development of Thixomolded{reg_sign} magnesium products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, D.; Fan, R.; Kang, K.

1995-10-01

Thixomolding{reg_sign} is a racial new process which merges the technologies of die-casting and plastic injection molding for the net shape molding of magnesium based alloys. Properties of Thixomolded{reg_sign} magnesium alloys are discussed and compared with those of traditional die casting. Magnesium alloys are of great interest to automobile manufacturers because of the potential weight savings and corresponding energy savings due to increased fuel economy. For this reason, one of the first target markets for Thixomolded{reg_sign} products is the automotive industry. The use of Thixomolding{reg_sign} in the production of an automobile part is examined.

Numerical simulation on semi-solid die-casting of magnesium matrix composite based on orthogonal experiment

NASA Astrophysics Data System (ADS)

Liu, Huihui; He, Xiongwei; Guo, Peng

2017-04-01

Three factors (pouring temperature, injection speed and mold temperature) were selected to do three levels L9 (33)orthogonal experiment, then simulate processing of semi-solid die-casting of magnesium matrix composite by Flow-3D software. The stress distribution, temperature field and defect distribution of filling process were analyzed to find the optimized processing parameter with the help of orthogonal experiment. The results showed that semi-solid has some advantages of well-proportioned stress and temperature field, less defect concentrated in the surface. The results of simulation were the same as the experimental results.

Method for removing volatile components from a ceramic article, and related processes

DOEpatents

Klug, Frederic Joseph; DeCarr, Sylvia Marie

2002-01-01

A method of removing substantially all of the volatile component in a green, volatile-containing ceramic article is disclosed. The method comprises freezing the ceramic article; and then subjecting the frozen article to a vacuum for a sufficient time to freeze-dry the article. Frequently, the article is heated while being freeze-dried. Use of this method efficiently reduces the propensity for any warpage of the article. The article is often formed from a ceramic slurry in a gel-casting process. A method for fabricating a ceramic core used in investment casting is also described.

Modelling of the rotational moulding process for the manufacture of plastic products

NASA Astrophysics Data System (ADS)

Khoon, Lim Kok

The present research is mainly focused on two-dimensional non-linear thermal modelling, numerical procedures and software development for the rotational moulding process. The RotoFEM program is developed for the rotational moulding process using finite element procedures. The program is written in the MATLAB environment. The research includes the development of new slip flow models, phase change study, warpage study and process analyses. A new slip flow methodology is derived for the heat transfer problem inside the enclosed rotating mould during the heating stage of the tumbling powder. The methodology enables the discontinuous powder to be modelled by the continuous-based finite element method. The Galerkin Finite Element Method is incorporated with the lumped-parameter system and the coincident node technique in finding the multi-interacting heat transfer solutions inside the mould. Two slip flow models arise from the slip flow methodology; they are SDM (single-layered deposition method) and MDM (multi-layered deposition method). These two models have differences in their thermal description for the internal air energy balance and the computational procedure for the deposition of the molten polymer. The SDM model assumes the macroscopic deposition of the molten polymer bed exists only between the bed and the inner mould surface. On the other hand, the MDM model allows the layer-by-layer deposition of the molten polymer bed macroscopically. In addition, the latter has a more detailed heat transfer description for the internal air inside the mould during the powder heating cycle. In slip flow models, the semi-implicit approach has been introduced to solve the final quasi-equilibrium internal air temperature during the heating cycle. A notable feature of this slip flow methodology is that the slip flow models are capable of producing good results for the internal air at the heating powder stage, without the consideration of the powder movement and changeable powder mass. This makes the modelling of the rotational moulding process much simpler. In the simulation of the cooling stage in rotational moulding, the thermal aspects of the inherent warpage problem and external-internal cooling method have been explored. The predicted internal air temperature profiles have shown that the less apparent crystallization plateau in the experimental internal air in practice could be related to warpage. Various phase change algorithms have been reviewed and compared, and thus the most convenient and considerable effective algorithm is proposed. The dimensional analysis method, expressed by means of dimensionless combinations of physical, boundary, and time variables, is utilized to study the dependence of the key thermal parameters on the processing times of rotational moulding. Lastly, the predicted results have been compared with the experimental results from two different external resources. The predicted temperature profiles of the internal air, oven times and other process conditions are consistent with the available data.

Simultaneous Luminescence Pressure and Temperature Measurement System for Hypersonic Wind Tunnels

NASA Technical Reports Server (NTRS)

Buck, Gregory M.

1995-01-01

Surface pressures and temperatures are determined from visible emission brightness and green-to-red color ratioing of induced luminescence from a ceramic surface with an organic dye coating. A ceramic-dye matrix of porous silica ceramic with an adsorbed dye is developed for high-temperature pressure sensitivity and stability (up to 150 C). Induced luminescence may be excited using a broad range of incident radiation from visible blue light (488-nm wavelength) to the near ultraviolet (365 nm). Ceramic research models and test samples are fabricated using net-form slip-casting and sintering techniques. Methods of preparation and effects of adsorption film thickness on measurement sensitivity are discussed. With the present 8-bit imaging system a 10% pressure measurement uncertainty from 50 to 760 torr is estimated, with an improvement to 5% from 3 to 1500 torr with a 12-bit imaging system.

Maxwell boundary condition and velocity dependent accommodation coefficient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Struchtrup, Henning, E-mail: struchtr@uvic.ca

2013-11-15

A modification of Maxwell's boundary condition for the Boltzmann equation is developed that allows to incorporate velocity dependent accommodation coefficients into the microscopic description. As a first example, it is suggested to consider the wall-particle interaction as a thermally activated process with three parameters. A simplified averaging procedure leads to jump and slip boundary conditions for hydrodynamics. Coefficients for velocity slip, temperature jump, and thermal transpiration flow are identified and compared with those resulting from the original Maxwell model and the Cercignani-Lampis model. An extension of the model leads to temperature dependent slip and jump coefficients.

Investigation of Heat Transfer at the Mold/Metal Interface in Permanent Mold Casting of Light Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert D. Pehlke; John T. Berry

2005-12-16

Accurate modeling of the metal casting process prior to creating a mold design demands reliable knowledge of the interfacial heat transfer coefficient at the mold metal interface as a function of both time and location. The phenomena concerned with the gap forming between the mold and the solidifying metal are complex but need to be understood before any modeling is attempted. The presence of mold coatings further complicates the situation. A commercial casting was chosen and studied in a gravity permanent mold casting process. The metal/mold interfacial heat transfer coefficient (IHTC) was the focus of the research. A simple, directmore » method has been used to evaluate the IHTC. Both the simulation and experiments have shown that a reasonably good estimate of the heat transfer coefficient could be made in the case studied. It has been found that there is a good agreement between experiments and simulations in the temperature profiles during the solidification process, given that the primary mechanism of heat transfer across the gap in permanent mold casting of light alloys is by conduction across the gap. The procedure utilized to determine the interfacial heat transfer coefficient can be applied to other casting processes. A recently completed project involving The University of Michigan and Mississippi State University, together with several industrial partners, which was supported by the USDOE through the Cast Metals Coalition, examined a number of cases of thermal contact. In an investigation which gave special consideration to the techniques of measurement, several mold coatings were employed and results presented as a function of time. Realistic conditions of coating thickness and type together with an appropriate combination of mold preheat and metal pouring temperature were strictly maintained throughout the investigation. Temperature sensors, in particular thermocouples, play an important part in validating the predictions of solidification models. Cooling curve information, as well as temperature gradient history both in the solidifying metal and within the mold are invariably required to be validated. This validation depends upon the response of the sensor concerned, but also on its own effect upon the thermal environment. A joint university/industry team has completed an investigation of the invasive effects of thermocouples upon temperature history in permanent molds determining the degree of uncertainty associated with placement and indicating how the time-temperature history may be recovered. In addition to its relevance to the all important study of thermal contact of the casting with metallic molds, the observations also impact the determination of heat flux and interfacial heat transfer coefficients. In these respects the study represents the first of its kind that has tackled the problem in depth for permanent mold castings. An important ramification of this investigation has been the errors likely to be encountered in mold temperature measurement with thin section aluminum castings, especially with respect to the plans for thermocouple placement. A comparison between the degree of uncertainty experienced in sand molds compared with that found in permanent molds reveals that the associated problems have a lesser impact. These conclusions and the related recommendations have been disseminated to industry and the technical community through project reports and publications.« less

Fabrication, characterization and fracture study of a machinable hydroxyapatite ceramic.

PubMed

Shareef, M Y; Messer, P F; van Noort, R

1993-01-01

In this study the preparation of a machinable hydroxyapatite from mixtures of a fine, submicrometer powder and either a coarse powder composed of porous aggregates up to 50 microns or a medium powder composed of dense particles of 3 microns median size is described. These were characterized using X-ray diffraction, transmission and scanning electron microscopy and infra-red spectroscopy. Test-pieces were formed by powder pressing and slip casting mixtures of various combinations of the fine, medium and coarse powders. The fired test-pieces were subjected to measurements of firing shrinkage, porosity, bulk density, tensile strength and fracture toughness. The microstructure and composition were examined using scanning electron microscopy and X-ray diffraction. For both processing methods, a uniform interconnected microporous structure was produced of a high-purity hydroxyapatite. The maximum tensile strength and fracture toughness that could be attained while retaining machinability were 37 MPa and 0.8 MPa m1/2 respectively.

Radiated energy and the rupture process of the Denali fault earthquake sequence of 2002 from broadband teleseismic body waves

USGS Publications Warehouse

Choy, G.L.; Boatwright, J.

2004-01-01

Displacement, velocity, and velocity-squared records of P and SH body waves recorded at teleseismic distances are analyzed to determine the rupture characteristics of the Denali fault, Alaska, earthquake of 3 November 2002 (MW 7.9, Me 8.1). Three episodes of rupture can be identified from broadband (???0.1-5.0 Hz) waveforms. The Denali fault earthquake started as a MW 7.3 thrust event. Subsequent right-lateral strike-slip rupture events with centroid depths of 9 km occurred about 22 and 49 sec later. The teleseismic P waves are dominated by energy at intermediate frequencies (0.1-1 Hz) radiated by the thrust event, while the SH waves are dominated by energy at lower frequencies (0.05-0.2 Hz) radiated by the strike-slip events. The strike-slip events exhibit strong directivity in the teleseismic SH waves. Correcting the recorded P-wave acceleration spectra for the effect of the free surface yields an estimate of 2.8 ?? 1015 N m for the energy radiated by the thrust event. Correcting the recorded SH-wave acceleration spectra similarly yields an estimate of 3.3 ?? 10 16 N m for the energy radiated by the two strike-slip events. The average rupture velocity for the strike-slip rupture process is 1.1??-1.2??. The strike-slip events were located 90 and 188 km east of the epicenter. The rupture length over which significant or resolvable energy is radiated is, thus, far shorter than the 340-km fault length over which surface displacements were observed. However, the seismic moment released by these three events, 4 ?? 1020 N m, was approximately half the seismic moment determined from very low-frequency analyses of the earthquake. The difference in seismic moment can be reasonably attributed to slip on fault segments that did not radiate significant or coherent seismic energy. These results suggest that very large and great strike-slip earthquakes can generate stress pulses that rapidly produce substantial slip with negligible stress drop and little discernible radiated energy on fault segments distant from the initial point of nucleation. The existence of this energy-deficient rupture mode has important implications for the evaluation of the seismic hazard of very large strike-slip earthquakes.

Electronic gap sensor and method

DOEpatents

Williams, R.S.; King, E.L.; Campbell, S.L.

1991-08-06

Disclosed are an apparatus and method for regulating the gap between a casting nozzle and a casting wheel in which the gap between the casting nozzle and the casting wheel is monitored by means of at least one sensing element protruding from the face of the casting nozzle. The sensing element is preferably connected to a voltage source and the casting wheel grounded. When the sensing element contacts the casting wheel, an electric circuit is completed. The completion of the circuit can be registered by an indicator, and the presence or absence of a completed circuit indicates the relative position of the casting nozzle to the casting wheel. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces. 5 figures.

Investigation of Parametric Influence on the Properties of Al6061-SiCp Composite

NASA Astrophysics Data System (ADS)

Adebisi, A. A.; Maleque, M. A.; Bello, K. A.

2017-03-01

The influence of process parameter in stir casting play a major role on the development of aluminium reinforced silicon carbide particle (Al-SiCp) composite. This study aims to investigate the influence of process parameters on wear and density properties of Al-SiCp composite using stir casting technique. Experimental data are generated based on a four-factors-five-level central composite design of response surface methodology. Analysis of variance is utilized to confirm the adequacy and validity of developed models considering the significant model terms. Optimization of the process parameters adequately predicts the Al-SiCp composite properties with stirring speed as the most influencing factor. The aim of optimization process is to minimize wear and maximum density. The multiple objective optimization (MOO) achieved an optimal value of 14 wt% reinforcement fraction (RF), 460 rpm stirring speed (SS), 820 °C processing temperature (PTemp) and 150 secs processing time (PT). Considering the optimum parametric combination, wear mass loss achieved a minimum of 1 x 10-3 g and maximum density value of 2.780g/mm3 with a confidence and desirability level of 95.5%.

Micro-Scale Thermoacoustics

NASA Astrophysics Data System (ADS)

Offner, Avshalom; Ramon, Guy Z.

2016-11-01

Thermoacoustic phenomena - conversion of heat to acoustic oscillations - may be harnessed for construction of reliable, practically maintenance-free engines and heat pumps. Specifically, miniaturization of thermoacoustic devices holds great promise for cooling of micro-electronic components. However, as devices size is pushed down to micro-meter scale it is expected that non-negligible slip effects will exist at the solid-fluid interface. Accordingly, new theoretical models for thermoacoustic engines and heat pumps were derived, accounting for a slip boundary condition. These models are essential for the design process of micro-scale thermoacoustic devices that will operate under ultrasonic frequencies. Stability curves for engines - representing the onset of self-sustained oscillations - were calculated with both no-slip and slip boundary conditions, revealing improvement in the performance of engines with slip at the resonance frequency range applicable for micro-scale devices. Maximum achievable temperature differences curves for thermoacoustic heat pumps were calculated, revealing the negative effect of slip on the ability to pump heat up a temperature gradient. The authors acknowledge the support from the Nancy and Stephen Grand Technion Energy Program (GTEP).

Solute softening and defect generation during prismatic slip in magnesium alloys

NASA Astrophysics Data System (ADS)

Yi, Peng; Cammarata, Robert C.; Falk, Michael L.

2017-12-01

Temperature and solute effects on prismatic slip of 〈a〉 dislocations in Mg are studied using molecular dynamics simulation. Prismatic slip is controlled by the low mobility screw dislocation. The screw dislocation glides on the prismatic plane through alternating cross-slip between the basal plane and the prismatic plane. In doing so, it exhibits a locking-unlocking mechanism at low temperatures and a more continuous wavy propagation at high temperatures. The dislocation dissociates into partials on the basal plane and the constriction formation of the partials is identified to be the rate-limiting process for unlocking. In addition, the diffusion of partials on the basal plane enables the formation of jogs and superjogs for prismatic slip, which lead to the generation of vacancies and dislocation loops. Solute softening in Mg alloys was observed in the presence of both Al and Y solute. The softening in prismatic slip is found to be due to solute pinning on the basal plane, instead of the relative energy change of the screw dislocation on the basal and prismatic planes, as has been hypothesized.

Constraining earthquake source inversions with GPS data: 2. A two-step approach to combine seismic and geodetic data sets

USGS Publications Warehouse

Custodio, S.; Page, M.T.; Archuleta, R.J.

2009-01-01

We present a new method to combine static and wavefield data to image earthquake ruptures. Our combined inversion is a two-step procedure, following the work of Hernandez et al. (1999), and takes into account the differences between the resolutions of the two data sets. The first step consists of an inversion of the static field, which yields a map of slip amplitude. This inversion exploits a special irregular grid that takes into account the resolution of the static data. The second step is an inversion of the radiated wavefield; it results in the determination of the time evolution of slip on the fault. In the second step, the slip amplitude is constrained to resemble the static slip amplitude map inferred from the GPS inversion. Using this combined inversion, we study the source process of the 2004 M6 Parkfield, California, earthquake. We conclude that slip occurred in two main regions of the fault, each of which displayed distinct rupture behaviors. Slip initiated at the hypocenter with a very strong bilateral burst of energy. Here, slip was localized in a narrow area approximately 10 km long, the rupture velocity was very fast (???3.5 km/s), and slip only lasted a short period of time (<1 s). Then the rupture proceeded to a wider region 12-20 km northwest of the hypocenter. Here, the earthquake developed in a more moderated way: the rupture velocity slowed to ???3.0 km/s and slip lasted longer (1-2 s). The maximum slip amplitude was 0.45 m. Copyright 2009 by the American Geophysical Union.

The study of flow pattern and phase-change problem in die casting process

NASA Technical Reports Server (NTRS)

Wang, T. S.; Wei, H.; Chen, Y. S.; Shang, H. M.

1996-01-01

The flow pattern and solidification phenomena in die casting process have been investigated in the first phase study. The flow pattern in filling process is predicted by using a VOF (volume of fluid) method. A good agreement with experimental observation is obtained for filling the water into a die cavity with different gate geometry and with an obstacle in the cavity. An enthalpy method has been applied to solve the solidification problem. By treating the latent heat implicitly into the enthalpy instead of explicitly into the source term, the CPU time can be reduced at least 20 times. The effect of material properties on solidification fronts is tested. It concludes that the dependence of properties on temperature is significant. The influence of the natural convection over the diffusion has also been studied. The result shows that the liquid metal solidification phenomena is diffusion dominant, and the natural convection can affect the shape of the interface. In the second phase study, the filling and solidification processes will be considered simultaneously.

Function-based design process for an intelligent ground vehicle vision system

NASA Astrophysics Data System (ADS)

Nagel, Robert L.; Perry, Kenneth L.; Stone, Robert B.; McAdams, Daniel A.

2010-10-01

An engineering design framework for an autonomous ground vehicle vision system is discussed. We present both the conceptual and physical design by following the design process, development and testing of an intelligent ground vehicle vision system constructed for the 2008 Intelligent Ground Vehicle Competition. During conceptual design, the requirements for the vision system are explored via functional and process analysis considering the flows into the vehicle and the transformations of those flows. The conceptual design phase concludes with a vision system design that is modular in both hardware and software and is based on a laser range finder and camera for visual perception. During physical design, prototypes are developed and tested independently, following the modular interfaces identified during conceptual design. Prototype models, once functional, are implemented into the final design. The final vision system design uses a ray-casting algorithm to process camera and laser range finder data and identify potential paths. The ray-casting algorithm is a single thread of the robot's multithreaded application. Other threads control motion, provide feedback, and process sensory data. Once integrated, both hardware and software testing are performed on the robot. We discuss the robot's performance and the lessons learned.

Growth of Fault-Cored Anticlines by Flexural Slip Folding: Analysis by Boundary Element Modeling

NASA Astrophysics Data System (ADS)

Johnson, Kaj M.

2018-03-01

Fault-related folds develop due to a combination of slip on the associated fault and distributed deformation off the fault. Under conditions that are sufficient for sedimentary layering to act as a stack of mechanical layers with contact slip, buckling can dramatically amplify the folding process. We develop boundary element models of fault-related folding of viscoelastic layers embedded with a reverse fault to examine the influence of such layering on fold growth. The strength of bedding contacts, the thickness and stiffness of layering, and fault geometry all contribute significantly to the resulting fold form. Frictional contact strength between layers controls the degree of localization of slip within fold limbs; high contact friction in relatively thin bedding tends to localize bedding slip within narrow kink bands on fold limbs, and low contact friction tends to produce widespread bedding slip and concentric fold form. Straight ramp faults tend to produce symmetric folds, whereas listric faults tend to produce asymmetric folds with short forelimbs and longer backlimbs. Fault-related buckle folds grow exponentially with time under steady loading rates. At early stages of folding, fold growth is largely attributed to slip on the fault, but as the fold increases amplitude, a larger portion of the fold growth is attributed to distributed slip across bedding contacts on the limbs of the fold. An important implication for geologic and earthquake studies is that not all surface deformation associated with blind reverse faults may be attributed to slip on the fault during earthquakes.

Demonstration of improved seismic source inversion method of tele-seismic body wave

NASA Astrophysics Data System (ADS)

Yagi, Y.; Okuwaki, R.

2017-12-01

Seismic rupture inversion of tele-seismic body wave has been widely applied to studies of large earthquakes. In general, tele-seismic body wave contains information of overall rupture process of large earthquake, while the tele-seismic body wave is inappropriate for analyzing a detailed rupture process of M6 7 class earthquake. Recently, the quality and quantity of tele-seismic data and the inversion method has been greatly improved. Improved data and method enable us to study a detailed rupture process of M6 7 class earthquake even if we use only tele-seismic body wave. In this study, we demonstrate the ability of the improved data and method through analyses of the 2016 Rieti, Italy earthquake (Mw 6.2) and the 2016 Kumamoto, Japan earthquake (Mw 7.0) that have been well investigated by using the InSAR data set and the field observations. We assumed the rupture occurring on a single fault plane model inferred from the moment tensor solutions and the aftershock distribution. We constructed spatiotemporal discretized slip-rate functions with patches arranged as closely as possible. We performed inversions using several fault models and found that the spatiotemporal location of large slip-rate area was robust. In the 2016 Kumamoto, Japan earthquake, the slip-rate distribution shows that the rupture propagated to southwest during the first 5 s. At 5 s after the origin time, the main rupture started to propagate toward northeast. First episode and second episode correspond to rupture propagation along the Hinagu fault and the Futagawa fault, respectively. In the 2016 Rieti, Italy earthquake, the slip-rate distribution shows that the rupture propagated to up-dip direction during the first 2 s, and then rupture propagated toward northwest. From both analyses, we propose that the spatiotemporal slip-rate distribution estimated by improved inversion method of tele-seismic body wave has enough information to study a detailed rupture process of M6 7 class earthquake.

Source process and tectonic implication of the January 20, 2007 Odaesan earthquake, South Korea

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Ali K.; Kim, K. Y.; Fnais, M. S.; Al-Amri, A. M.

2014-04-01

The source process for the 20th of January 2007, Mw 4.5 Odaesan earthquake in South Korea is investigated in the low- and high-frequency bands, using velocity and acceleration waveform data recorded by the Korea Meteorological Administration Seismographic Network at distances less than 70 km from the epicenter. Synthetic Green functions are adopted for the low-frequency band of 0.1-0.3 Hz by using the wave-number integration technique and the one dimensional velocity model beneath the epicentral area. An iterative technique was performed by a grid search across the strike, dip, rake, and focal depth of rupture nucleation parameters to find the best-fit double-couple mechanism. To resolve the nodal plane ambiguity, the spatiotemporal slip distribution on the fault surface was recovered using a non-negative least-square algorithm for each set of the grid-searched parameters. The focal depth of 10 km was determined through the grid search for depths in the range of 6-14 km. The best-fit double-couple mechanism obtained from the finite-source model indicates a vertical strike-slip faulting mechanism. The NW faulting plane gives comparatively smaller root-mean-squares (RMS) error than its auxiliary plane. Slip pattern event provides simple source process due to the effect of Low-frequency that acted as a point source model. Three empirical Green functions are adopted to investigate the source process in the high-frequency band. A set of slip models was recovered on both nodal planes of the focal mechanism with various rupture velocities in the range of 2.0-4.0 km/s. Although there is a small difference between the RMS errors produced by the two orthogonal nodal planes, the SW dipping plane gives a smaller RMS error than its auxiliary plane. The slip distribution is relatively assessable by the oblique pattern recovered around the hypocenter in the high-frequency analysis; indicating a complex rupture scenario for such moderate-sized earthquake, similar to those reported for large earthquakes.

Triggered surface slips in the Salton Trough associated with the 1999 Hector Mine, California, earthquake

USGS Publications Warehouse

Rymer, M.J.; Boatwright, J.; Seekins, L.C.; Yule, J.D.; Liu, J.

2002-01-01

Surface fracturing occurred along the southern San Andreas, Superstition Hills, and Imperial faults in association with the 16 October 1999 (Mw 7.1) Hector Mine earthquake, making this at least the eighth time in the past 31 years that a regional earthquake has triggered slip along faults in the Salton Trough. Fractures associated with the event formed discontinuous breaks over a 39-km-long stretch of the San Andreas fault, from the Mecca Hills southeastward to Salt Creek and Durmid Hill, a distance from the epicenter of 107 to 139 km. Sense of slip was right lateral; only locally was there a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 13 mm. Maximum slip values in 1999 and earlier triggered slips are most common in the central Mecca Hills. Field evidence indicates a transient opening as the Hector Mine seismic waves passed the southern San Andreas fault. Comparison of nearby strong-motion records indicates several periods of relative opening with passage of the Hector Mine seismic wave-a similar process may have contributed to the field evidence of a transient opening. Slip on the Superstition Hills fault extended at least 9 km, at a distance from the Hector Mine epicenter of about 188 to 196 km. This length of slip is a minimum value, because we saw fresh surface breakage extending farther northwest than our measurement sites. Sense of slip was right lateral; locally there was a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 18 mm, with the largest amounts found distributed (or skewed) away from the Hector Mine earthquake source. Slip triggered on the Superstition Hills fault commonly is skewed away from the earthquake source, most notably in 1968, 1979, and 1999. Surface slip on the Imperial fault and within the Imperial Valley extended about 22 km, representing a distance from the Hector Mine epicenter of about 204 to 226 km. Sense of slip dominantly was right lateral; the right-lateral component of slip ranged from 1 to 19 mm. Locally there was a minor (~1-2 mm) vertical component of slip; larger proportions of vertical slip (up to 10 mm) occurred in Mesquite basin, where scarps indicate long-term oblique-slip motion for this part of the Imperial fault. Slip triggered on the Imperial fault appears randomly distributed relative to location along the fault and source direction. Multiple surface slips, both primary and triggered slip, indicate that slip repeatedly is small at locations of structural complexity.

Relaxation of the single-slip condition in strain-gradient plasticity

PubMed Central

Anguige, Keith; Dondl, Patrick W.

2014-01-01

We consider the variational formulation of both geometrically linear and geometrically nonlinear elasto-plasticity subject to a class of hard single-slip conditions. Such side conditions typically render the associated boundary-value problems non-convex. We show that, for a large class of non-smooth plastic distortions, a given single-slip condition (specification of Burgers vectors) can be relaxed by introducing a microstructure through a two-stage process of mollification and lamination. The relaxed model can be thought of as an aid to simulating macroscopic plastic behaviour without the need to resolve arbitrarily fine spatial scales. PMID:25197243

Relaxation of the single-slip condition in strain-gradient plasticity.

PubMed

Anguige, Keith; Dondl, Patrick W

2014-09-08

We consider the variational formulation of both geometrically linear and geometrically nonlinear elasto-plasticity subject to a class of hard single-slip conditions. Such side conditions typically render the associated boundary-value problems non-convex. We show that, for a large class of non-smooth plastic distortions, a given single-slip condition (specification of Burgers vectors) can be relaxed by introducing a microstructure through a two-stage process of mollification and lamination. The relaxed model can be thought of as an aid to simulating macroscopic plastic behaviour without the need to resolve arbitrarily fine spatial scales.

PROCESS OF PRODUCING SHAPED PLUTONIUM

DOEpatents

Anicetti, R.J.

1959-08-11

A process is presented for producing and casting high purity plutonium metal in one step from plutonium tetrafluoride. The process comprises heating a mixture of the plutonium tetrafluoride with calcium while the mixture is in contact with and defined as to shape by a material obtained by firing a mixture consisting of calcium oxide and from 2 to 10% by its weight of calcium fluoride at from 1260 to 1370 deg C.

Characteristics of ADC12/nano Al2O3composites with Addition of Ti Produced By Stir Casting Method

NASA Astrophysics Data System (ADS)

Zulfia, A.; Krisiphala; Ferdian, D.; Utomo, B. W.; Dhaneswara, D.

2018-03-01

The mechanical properties and microstructure of ADC12/nano Al2O3 matrix composites have been studied in this work. The composites were produced by stir casting method. ADC 12 as matrix composites was combined by Mg and Ti. The addition of Ti was varied from 0.02 to 0.08 wt-% as grain refinement wetting to improve mechanical properties such as tensile strength, hardness and wear resistance, while Mg addition was to promote wetting between ADC 12 and nano Al2O3. The optimum tensile strength was found at 0.04 wt-% addition of Ti with value of 132.5 MPa, further adding more Ti cause a poisoning mechanism that will hindered the grain refining process and reduce the tensile strength. The hardness and wear resistance of composites would also increase because of the refinement process. and the added Magnesium in the material that will form Mg2Si primary phases who have a high hardness value.

Nano-indentation used to study pyramidal slip in GaN single crystals

NASA Astrophysics Data System (ADS)

Krimsky, E.; Jones, K. A.; Tompkins, R. P.; Rotella, P.; Ligda, J.; Schuster, B. E.

2018-02-01

The nucleation and structure of dislocations created by the nano-indentation of GaN samples with dislocation densities ≈103, 106 or 109 ⊥/cm2 were studied in the interest of learning how dislocations can be created to relieve the mismatch strain in ternary nitride films grown on (0001) oriented binary nitride substrates. Using transmission electron microscopy and stress analyses to assist in interpreting the nano-indentation data, we determined that the pop-ins in the indenter load vs. penetration depth curves are created by an avalanche process at stresses well above the typical yield stress. The process begins by the homogeneous formation of a basal plane screw dislocation that triggers the formation of pyramidal and other basal plane dislocations that relieve the excess stored elastic energy. It appears that pyramidal slip can occur on either the {1122} or {0111} planes, as there is little resistance to the cross slip of screw dislocations.

Tectonic escape in the evolution of the continental crust

NASA Technical Reports Server (NTRS)

Burke, K.; Sengor, C.

1986-01-01

The continental crust originated by processes similar to those operating today and continents consist of material most of which originated long ago in arc-systems that have later been modified, especially at Andean margins and in continental collisions where crustal thickening is common. Collision-related strike-slip motion is a general process in continental evolution. Because buoyant continental (or arc) material generally moves during collision toward a nearby oceanic margin where less buoyant lithosphere crops out, the process of major strike-slip dominated motion toward a 'free-face' is called 'tectonic escape'. Tectonic escape is and has been an element in continental evolution throughout recorded earth-history. It promotes: (1) rifting and the formation of rift-basins with thinning of thickened crust; (2) pervasive strike-slip faulting late in orogenic history which breaks up mountain belts across strike and may juxtapose unrelated sectors in cross-section; (3) localized compressional mountains and related foreland-trough basins.

Accelerated nucleation of the 2014 Iquique, Chile Mw 8.2 Earthquake

NASA Astrophysics Data System (ADS)

Kato, Aitaro; Fukuda, Jun'Ichi; Kumazawa, Takao; Nakagawa, Shigeki

2016-04-01

The earthquake nucleation process has been vigorously investigated based on geophysical observations, laboratory experiments, and theoretical studies; however, a general consensus has yet to be achieved. Here, we studied nucleation process for the 2014 Iquique, Chile Mw 8.2 megathrust earthquake located within the current North Chile seismic gap, by analyzing a long-term earthquake catalog constructed from a cross-correlation detector using continuous seismic data. Accelerations in seismicity, the amount of aseismic slip inferred from repeating earthquakes, and the background seismicity, accompanied by an increasing frequency of earthquake migrations, started around 270 days before the mainshock at locations up-dip of the largest coseismic slip patch. These signals indicate that repetitive sequences of fast and slow slip took place on the plate interface at a transition zone between fully locked and creeping portions. We interpret that these different sliding modes interacted with each other and promoted accelerated unlocking of the plate interface during the nucleation phase.

Accelerated nucleation of the 2014 Iquique, Chile Mw 8.2 Earthquake.

PubMed

Kato, Aitaro; Fukuda, Jun'ichi; Kumazawa, Takao; Nakagawa, Shigeki

2016-04-25

The earthquake nucleation process has been vigorously investigated based on geophysical observations, laboratory experiments, and theoretical studies; however, a general consensus has yet to be achieved. Here, we studied nucleation process for the 2014 Iquique, Chile Mw 8.2 megathrust earthquake located within the current North Chile seismic gap, by analyzing a long-term earthquake catalog constructed from a cross-correlation detector using continuous seismic data. Accelerations in seismicity, the amount of aseismic slip inferred from repeating earthquakes, and the background seismicity, accompanied by an increasing frequency of earthquake migrations, started around 270 days before the mainshock at locations up-dip of the largest coseismic slip patch. These signals indicate that repetitive sequences of fast and slow slip took place on the plate interface at a transition zone between fully locked and creeping portions. We interpret that these different sliding modes interacted with each other and promoted accelerated unlocking of the plate interface during the nucleation phase.

Process for the production of ultrahigh purity silane with recycle from separation columns

DOEpatents

Coleman, Larry M.

1982-07-20

Tri- and dichlorosilanes formed by hydrogenation in the course of the reaction of metallurgical silicon, hydrogen and recycle silicon tetrachloride are employed as feed into a separation column arrangement of sequential separation columns and redistribution reactors which processes the feed into ultrahigh purity silane and recycle silicon tetrachloride. A slip stream is removed from the bottom of two sequential columns and added to the recycle silicon tetrachloride process stream causing impurities in the slip streams to be subjected to reactions in the hydrogenation step whereby waste materials can be formed and readily separated.

[Manufacture and clinical application of 215 IPS-Empress casting ceramic restorations].

PubMed

Zhao, Na; Zhou, Jian

2008-08-01

To explore the manufacture and clinical application of IPS-Empress casting ceramic restorations. The problems in manufacture and clinical operation of 215 casting ceramic restorations were analyzed. In 215 casting ceramic restorations, 12 (5.58%) casting ceramic restorations were affected by clinical design or application, 15 (6.98%) casting ceramic restorations were affected by some manufacture problems, and 14 (6.51%) casting ceramic restorations were affected by clinical try-in. Through 2-3 years' follow-up, the achievement ratio of 215 IPS-Empress casting ceramic restorations was 94.88%, and 11 casting ceramic restorations were affected by some problems. Beauty and simultaneous enamel wear are the characteristics of casting ceramic restorations. But because of its brittle, the indications should be strictly selected.

Preliminary soil-slip susceptibility maps, southwestern California

USGS Publications Warehouse

Morton, Douglas M.; Alvarez, Rachel M.; Campbell, Russell H.; Digital preparation by Bovard, Kelly R.; Brown, D.T.; Corriea, K.M.; Lesser, J.N.

2003-01-01

This group of maps shows relative susceptibility of hill slopes to the initiation sites of rainfall-triggered soil slip-debris flows in southwestern California. As such, the maps offer a partial answer to one part of the three parts necessary to predict the soil-slip/debris-flow process. A complete prediction of the process would include assessments of “where”, “when”, and “how big”. These maps empirically show part of the “where” of prediction (i.e., relative susceptibility to sites of initiation of the soil slips) but do not attempt to show the extent of run out of the resultant debris flows. Some information pertinent to “when” the process might begin is developed. “When” is determined mostly by dynamic factors such as rainfall rate and duration, for which local variations are not amenable to long-term prediction. “When” information is not provided on the maps but is described later in this narrative. The prediction of “how big” is addressed indirectly by restricting the maps to a single type of landslide process—soil slip-debris flows. The susceptibility maps were created through an iterative process from two kinds of information. First, locations of sites of past soil slips were obtained from inventory maps of past events. Aerial photographs, taken during six rainy seasons that produced abundant soil slips, were used as the basis for soil slip-debris flow inventory. Second, digital elevation models (DEM) of the areas that were inventoried were used to analyze the spatial characteristics of soil slip locations. These data were supplemented by observations made on the ground. Certain physical attributes of the locations of the soil-slip debris flows were found to be important and others were not. The most important attribute was the mapped bedrock formation at the site of initiation of the soil slip. However, because the soil slips occur in surficial materials overlying the bedrocks units, the bedrock formation can only serve as a surrogate for the susceptibility of the overlying surficial materials. The maps of susceptibility were created from those physical attributes learned to be important from the inventories. The multiple inventories allow a model to be created from one set of inventory data and evaluated with others. The resultant maps of relative susceptibility represent the best estimate generated from available inventory and DEM data. Slope and aspect values used in the susceptibility analysis were 10-meter DEM cells at a scale of 1:24,000. For most of the area 10-meter DEMs were available; for those quadrangles that have only 30-meter DEMs, the 30-meter DEMS were resampled to 10-meters to maintain resolution of 10-meter cells. Geologic unit values used in the susceptibility analysis were five-meter cells. For convenience, the soil slip susceptibility values are assembled on 1:100,000-scale bases. Any area of the 1:100,000-scale maps can be transferred to 1:24,000-scale base without any loss of accuracy. Figure 32 is an example of part of a 1:100,000-scale susceptibility map transferred back to a 1:24,000-scale quadrangle.

Kinematic rupture process of the 2014 Chile Mw 8.1 earthquake constrained by strong-motion, GPS static offsets and teleseismic data

NASA Astrophysics Data System (ADS)

Liu, Chengli; Zheng, Yong; Wang, Rongjiang; Xiong, Xiong

2015-08-01

On 2014 April 1, a magnitude Mw 8.1 interplate thrust earthquake ruptured a densely instrumented region of Iquique seismic gap in northern Chile. The abundant data sets near and around the rupture zone provide a unique opportunity to study the detailed source process of this megathrust earthquake. We retrieved the spatial and temporal distributions of slip during the main shock and one strong aftershock through a joint inversion of teleseismic records, GPS offsets and strong motion data. The main shock rupture initiated at a focal depth of about 25 km and propagated around the hypocentre. The peak slip amplitude in the model is ˜6.5 m, located in the southeast of the hypocentre. The major slip patch is located around the hypocentre, spanning ˜150 km along dip and ˜160 km along strike. The associated static stress drop is ˜3 MPa. Most of the seismic moment was released within 150 s. The total seismic moment of our preferred model is 1.72 × 1021 N m, equivalent to Mw 8.1. For the strong aftershock on 2014 April 3, the slip mainly occurred in a relatively compact area, and the major slip area surrounded the hypocentre with the peak amplitude of ˜2.5 m. There is a secondary slip patch located downdip from the hypocentre with the peak slip of ˜2.1 m. The total seismic moment is about 3.9 × 1020 N m, equivalent to Mw 7.7. Between the rupture areas of the main shock and the 2007 November 14 Mw 7.7 Antofagasta, Chile earthquake, there is an earthquake vacant zone with a total length of about 150 km. Historically, if there is no big earthquake or obvious aseismic creep occurring in this area, it has a great potential of generating strong earthquakes with magnitude larger than Mw 7.0 in the future.

Identification of the meta-instability stage via synergy of fault displacement: An experimental study based on the digital image correlation method

NASA Astrophysics Data System (ADS)

Zhuo, Yan-Qun; Ma, Jin; Guo, Yan-Shuang; Ji, Yun-Tao

In stick-slip experiments modeling the occurrence of earthquakes, the meta-instability stage (MIS) is the process that occurs between the peak differential stress and the onset of sudden stress drop. The MIS is the final stage before a fault becomes unstable. Thus, identification of the MIS can help to assess the proximity of the fault to the earthquake critical time. A series of stick-slip experiments on a simulated strike-slip fault were conducted using a biaxial servo-controlled press machine. Digital images of the sample surface were obtained via a high speed camera and processed using a digital image correlation method for analysis of the fault displacement field. Two parameters, A and S, are defined based on fault displacement. A, the normalized length of local pre-slip areas identified by the strike-slip component of fault displacement, is the ratio of the total length of the local pre-slip areas to the length of the fault within the observed areas and quantifies the growth of local unstable areas along the fault. S, the normalized entropy of fault displacement directions, is derived from Shannon entropy and quantifies the disorder of fault displacement directions along the fault. Based on the fault displacement field of three stick-slip events under different loading rates, the experimental results show the following: (1) Both A and S can be expressed as power functions of the normalized time during the non-linearity stage and the MIS. The peak curvatures of A and S represent the onsets of the distinct increase of A and the distinct reduction of S, respectively. (2) During each stick-slip event, the fault evolves into the MIS soon after the curvatures of both A and S reach their peak values, which indicates that the MIS is a synergetic process from independent to cooperative behavior among various parts of a fault and can be approximately identified via the peak curvatures of A and S. A possible application of these experimental results to field conditions is provided. However, further validation is required via additional experiments and exercises.

Interim Report on Mixing During the Casting of LEU-10Mo Plates in the Triple Plate Molds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aikin, Jr., Robert M.

LEU-10%Mo castings are commonly produced by down blending unalloyed HEU with a DU-12.7%Mo master-alloy. This work uses process modeling to provide insight into the mixing of the unalloyed uranium and U-Mo master alloy during melting and mold filling of a triple plate casting. Two different sets of situations are considered: (1) mixing during mold filling from a compositionally stratified crucible and (2) convective mixing of a compositionally stratified crucible during mold heating. The mold filling simulations are performed on the original Y-12 triple plate mold and the horizontal triple plate mold.

Silicon material development for terrestrial solar cells. Phase of exploration

NASA Astrophysics Data System (ADS)

Sirtl, E.

1983-03-01

A material project based on a multicrystalline silicon is reported. It consists of refining the metallurgical grade silicon via hydro and pyrometallurgical processes, preparation of square shaped ingots by (inert) gas protected or open hearth casting methods, and high speed slicing, using a multiple blade slurry saw. Second generation pilot equipment was constructed. Aluminothermic reduction of quartz sand into silicon and the foil casting process were tested. It is concluded that the production of silicon thru the gaseous phase depends upon the marketing of very cheap basic material (SG-Si 10 dollar/Kg) and that the purification of metallurgical grade silicon by refining is the most promising method.

Mechanical properties of aluminium fused SiO2 particulate composites cast using metallic and non-metallic chills

NASA Astrophysics Data System (ADS)

Harshith, H. S.; Hemanth, Joel

2018-04-01

This research work aims at developing and mechanical characterization of aluminium (LM13) based metal matrix composite reinforced with varying percentage of fused SiO2 (3%,6%,9%,12%). The mechanical properties are completely dependent on the microstructural parameters of the system. Also the microstructure further depends on the cooling rates during solidification process. Various Chills like Silicon carbide, Mild steel, Copper were used during the casting process to increase the rate of solidification, which enhances the mechanical properties of the composite. The chill casted specimens were subjected to tensile and hardness tests followed by microstructure studies. A casting produced using mild steel chill exhibited higher young's modulus and was found to be maximum at 9% reinforcement. Finer microstructure and better UTS were seen for specimen's casted using copper chills, whereas silicon carbide and mild steel chills gave rise to very coarse structure with reduced UTS values compared to copper chills.

On the membrane approximation in isothermal film casting

NASA Astrophysics Data System (ADS)

Hagen, Thomas

2014-08-01

In this work, a one-dimensional model for isothermal film casting is studied. Film casting is an important engineering process to manufacture thin films and sheets from a highly viscous polymer melt. The model equations account for variations in film width and film thickness, and arise from thinness and kinematic assumptions for the free liquid film. The first aspect of our study is a rigorous discussion of the existence and uniqueness of stationary solutions. This objective is approached via the argument principle, exploiting the homotopy invariance of a family of analytic functions. As our second objective, we analyze the linearization of the governing equations about stationary solutions. It is shown that solutions for the associated boundary-initial value problem are given by a strongly continuous semigroup of bounded linear operators. To reach this result, we cast the relevant Cauchy problem in a more accessible form. These transformed equations allow us insight into the regularity of the semigroup, thus yielding the validity of the spectral mapping theorem for the semigroup and the spectrally determined growth property.

Snowball gouge-aggregates formed in experimental fault gouges at seismic slip rates

NASA Astrophysics Data System (ADS)

Kim, J. H.; Ree, J. H.; Hirose, T.; Yang, K.; Kim, J. W.

2015-12-01

Clay-clast aggregates (CCA) have commonly been reported from experimental and natural fault gouges, but their formation process and mechanical meaning are not so clear. We call CCA snowball gouge aggregate (SGA) since its formation process is similar to that of snowball (see below) and CCA-like structure has been reported also from pure quartz and pure calcite gouges. Here, we discuss the formation process of SGA and its implication for faulting from experimental results of simulated gouges. We conducted high-velocity rotary shear experiments on Ca-bentonite gouges at a normal stress of 1 MPa, slip rate of 1.31 m/s, room temperature and room humidity conditions. Ca-bentonite gouge consists of montmorillonite (>95%) and other minor minerals including quartz and plagioclase. Upon displacement, the friction abruptly increases to the 1st peak (friction coefficient μ≈ 0.7) followed by slip weakening to reach a steady state (μ≈ 0.25~0.3). The simulated fault zone can be divided into slip-localization zone (SLZ) and low-slip-rate zone (LSZ) based on grain size. Spherical SGAs with their size ranging from 1 to 100 μm occur only in LSZ, and their proportion is more than 90%. Two types of SGA occur; SGA with and without a central clast. Both types of SGA show a concentric layering defined by the alternation of pore-rich (1-1.5 μm thick) and pore-poor layers (1.5-2 μm thick). Clay minerals locally exhibit a preferred orientation with their basal plane parallel to the layer boundary. We interpret that the pore-poor layers are clay-accumulated layers formed by rolling of SGA nuclei, and pore-rich layers correspond to the boundary between accumulated clay layers. Water produced from dehydration of clays due to frictional heating presumably acts as an adhesion agent of clay minerals during rolling of SGA. Since the number of layers within each SGA represents the number of rolling, the minimum displacement estimated from the number of layers and layer thickness of the largest SGA (with a diameter of 100 μm) is about 2.7 mm (slip rate≈ 170 μm/s) which is much less than the total displacement of 20 m, suggesting that most of the displacement occurred along the SLZ. Our results imply that SGA can be formed only in subseismic slip-rate zones and that minimum displacement and slip rate can be estimated from SGA.

Process for the production of ultrahigh purity silane with recycle from separation columns

NASA Technical Reports Server (NTRS)

Coleman, Larry M. (Inventor)

1982-01-01

Tri- and dichlorosilanes formed by hydrogenation in the course of the reaction of metallurgical silicon, hydrogen and recycle silicon tetrachloride are employed as feed into a separation column arrangement of sequential separation columns and redistribution reactors which processes the feed into ultrahigh purity silane and recycle silicon tetrachloride. A slip stream is removed from the bottom of two sequential columns and added to the recycle silicon tetrachloride process stream causing impurities in the slip streams to be subjected to reactions in the hydrogenation step whereby waste materials can be formed and readily separated.

"Virtual shear box" experiments of stress and slip cycling within a subduction interface mélange

NASA Astrophysics Data System (ADS)

Webber, Sam; Ellis, Susan; Fagereng, Åke

2018-04-01

What role does the progressive geometric evolution of subduction-related mélange shear zones play in the development of strain transients? We use a "virtual shear box" experiment, based on outcrop-scale observations from an ancient exhumed subduction interface - the Chrystalls Beach Complex (CBC), New Zealand - to constrain numerical models of slip processes within a meters-thick shear zone. The CBC is dominated by large, competent clasts surrounded by interconnected weak matrix. Under constant slip velocity boundary conditions, models of the CBC produce stress cycling behavior, accompanied by mixed brittle-viscous deformation. This occurs as a consequence of the reorganization of competent clasts, and the progressive development and breakdown of stress bridges as clasts mutually obstruct one another. Under constant shear stress boundary conditions, the models show periods of relative inactivity punctuated by aseismic episodic slip at rapid rates (meters per year). Such a process may contribute to the development of strain transients such as slow slip.

Source complexity of the 1987 Whittier Narrows, California, earthquake from the inversion of strong motion records

USGS Publications Warehouse

Hartzell, S.; Iida, M.

1990-01-01

Strong motion records for the Whittier Narrows earthquake are inverted to obtain the history of slip. Both constant rupture velocity models and variable rupture velocity models are considered. The results show a complex rupture process within a relatively small source volume, with at least four separate concentrations of slip. Two sources are associated with the hypocenter, the larger having a slip of 55-90 cm, depending on the rupture model. These sources have a radius of approximately 2-3 km and are ringed by a region of reduced slip. The aftershocks fall within this low slip annulus. Other sources with slips from 40 to 70 cm each ring the central source region and the aftershock pattern. All the sources are predominantly thrust, although some minor right-lateral strike-slip motion is seen. The overall dimensions of the Whittier earthquake from the strong motion inversions is 10 km long (along the strike) and 6 km wide (down the dip). The preferred dip is 30?? and the preferred average rupture velocity is 2.5 km/s. Moment estimates range from 7.4 to 10.0 ?? 1024 dyn cm, depending on the rupture model. -Authors

Centrifugal casting of ZA8 zinc alloy and composite A356/silicon carbide: Study and modeling of phases' and particles' segregation

NASA Astrophysics Data System (ADS)

Balout, Bahaa

Centrifugation is a casting technology that allows the production of cylindrical and graduated parts with different mechanical properties through the section. The need for materials with good quality and specific mechanical properties has been driven this technology in order to produce different types of materials such as zinc alloys and graduated metal matrix composites reinforced by hard and wear resistant particles. The goal of this research project is to study and model the eutectic macrosegregation, the solidification speed, and the speeds of solidification fronts during centrifugal casting of ZA8 zinc-aluminum alloy in order to improve the part quality and increase its strength and field reliability. Moreover, the segregation of the particles during centrifugal casting of an aluminum matrix composite reinforced by silicon carbide particles (A356/SiC) is also studied to improve and control the graduation of the parts. The cooling rate, the speed, acceleration/deceleration, displacement, and segregation of the particles across the section will be modeled by discretization of Stokes' law in time in order to take into consideration the change in the centrifugal radius and melt viscosity during cooling process. This study will allow the control of the graduation degree of particles across the section in order to improve the properties and wear resistance of the composite. This composite can be used in systems where friction is critical and load is high (reinforcements of parts for the cylinders of pneumatic systems). The results show that the maximum macrosegregation zone of the eutectic across the casting section corresponds to the last point of solidification. The eutectic macrosegregation produced during centrifugal casting of thin walled part is a normal segregation which varies depending on the solidification speed and the ratio between the speeds of solidification fronts. On the other hand, it was found that the position and volume fraction of the particles on the outer/inner casting surface and across the section varies whether the viscosity of the liquid metal used and the centrifugal radius are considered constant or variable during the modeling. Modeling the particles' segregation while discretizing, in time, the particles' velocities gives more consistent results compared to those obtained experimentally. Key-words: centrifugal casting, composite, macrosegregation, solidification.

40 CFR 464.20 - Applicability; description of the copper casting subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... copper casting subcategory. 464.20 Section 464.20 Protection of Environment ENVIRONMENTAL PROTECTION... Copper Casting Subcategory § 464.20 Applicability; description of the copper casting subcategory. The... introduction of pollutants into publicly owned treatment works resulting from copper casting operations as...

Basic Casting from A to Z. Student's Instruction Booklet.

ERIC Educational Resources Information Center

Zebco, Tulsa, OK.

A profusely illustrated student instruction booklet contains step-by-step directions and diagrams for learning four basic casting techniques. Separate sections cover basic spin-casting, spinning, bait-casting, and fly-casting. Each section details recommended equipment (reel, rod, line, plug, tackle, lures, leaders, flies), describes specific…

Cellularized Cellular Solids via Freeze-Casting.

PubMed

Christoph, Sarah; Kwiatoszynski, Julien; Coradin, Thibaud; Fernandes, Francisco M

2016-02-01

The elaboration of metabolically active cell-containing materials is a decisive step toward the successful application of cell based technologies. The present work unveils a new process allowing to simultaneously encapsulate living cells and shaping cell-containing materials into solid-state macroporous foams with precisely controlled morphology. Our strategy is based on freeze casting, an ice templating materials processing technique that has recently emerged for the structuration of colloids into macroporous materials. Our results indicate that it is possible to combine the precise structuration of the materials with cellular metabolic activity for the model organism Saccharomyces cerevisiae. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Silicon-based Porous Ceramics via Freeze Casting of Preceramic Polymers

NASA Astrophysics Data System (ADS)

Naviroj, Maninpat

Freeze casting is a technique for processing porous materials that has drawn significant attention for its effectiveness in producing a variety of tailorable pore structures for ceramics, metals, and polymers. With freeze casting, pores are generated based on a solidification process where ice crystals act as a sacrificial template which can eventually be sublimated to create pores. While the majority of freeze-casting studies have been performed using conventional ceramic suspensions, this work explores an alternative processing route by freeze casting with preceramic polymer solutions. Significant differences exist between freeze casting of a particulate suspension and a polymeric solution. These changes affect the processing method, solidification behavior, and pore structure, thereby introducing new challenges and possibilities for the freeze-casting technique. The first part of this study explored the processing requirements involved with freeze casting of preceramic polymers, along with methods to control the resulting pore structure. Solvent choice, freezing front velocity, and polymer concentration were used as processing variables to manipulate the pore structures. A total of seven organic solvents were freeze cast with a polymethylsiloxane preceramic polymer to produce ceramics with isotropic, dendritic, prismatic, and lamellar pore morphologies. Changes in freezing front velocity and polymer concentration were shown to influence pore size, shape, and connectivity. Differences between suspension- and solution-based samples freeze cast under equivalent conditions were also investigated. Certain solidification microstructures were strongly affected by the presence of suspended particles, creating differences between pore structures generated from the same solvents. Additionally, processing of solution-based samples were found to be the more facile technique. Compressive strength and water permeability of dendritic and lamellar structures were analyzed to determine functional differences between the pore structures. Results show that dendritic structures were up to 30 times stronger, while lamellar structures provided higher permeability constants. A change in freezing front velocity was shown to significantly affect permeability but not compressive strength. Finally, improved pore alignment along the freezing direction was achieved by controlling the nucleation and growth of solvent crystals through the use of a grain-selection template. Dendritic samples freeze cast with a template showed substantial increase in pore alignment, as determined by image analysis and permeability tests, with the permeability constant increasing by up to 6-fold when compared to a control sample.

Comparison of different soft grippers for lunch box packaging.

PubMed

Wang, Zhongkui; Zhu, Mingzhu; Kawamura, Sadao; Hirai, Shinichi

2017-01-01

Automating the lunch box packaging is a challenging task due to the high deformability and large individual differences in shape and physical property of food materials. Soft robotic grippers showed potentials to perform such tasks. In this paper, we presented four pneumatic soft actuators made of different materials and different fabrication methods and compared their performances through a series of tests. We found that the actuators fabricated by 3D printing showed better linearity and less individual differences, but showed low durability compared to actuators fabricated by traditional casting process. Robotic grippers were assembled using the soft actuators, and grasping tests were performed on soft paper containers filled with food materials. Results suggested that grippers with softer actuators required lower air pressure to lift up the same weight and generated less deformation on the soft container. The actuator made of casting process with Dragon Skin 10 material lifted the most weight among different actuators.

Comparison of implant-abutment interface misfits after casting and soldering procedures.

PubMed

Neves, Flávio Domingues das; Elias, Gisele Araújo; da Silva-Neto, João Paulo; de Medeiros Dantas, Lucas Costa; da Mota, Adérito Soares; Neto, Alfredo Júlio Fernandes

2014-04-01

The aim of this study was to compare vertical and horizontal adjustments of castable abutments after conducting casting and soldering procedures. Twelve external hexagonal implants (3.75 × 10 mm) and their UCLA abutments were divided according their manufacturer and abutment type: PUN (plastic UCLA, Neodent), PUC (plastic UCLA, Conexão), PU3i (plastic UCLA, Biomet 3i), and PUTN (plastic UCLA with Tilite milled base, Neodent). Three infrastructures of a fixed partial implant-supported bridge with 3 elements were produced for each group. The measurements of vertical (VM) and horizontal (HM) misfits were obtained via scanning electron microscopy after completion of casting and soldering. The corresponding values were determined to be biomechanically acceptable to the system, and the results were rated as a percentage. Statistical analysis establishes differences between groups by chi-square after procedures, and McNeman's test was applied to analyze the influence of soldering over casting (α ≤ .05). For the values of VM and HM, respectively, when the casting process was complete, it was observed that 83.25% and 100% (PUTN), 33.3% and 27.75% (PUN), 33.3% and 88.8% (PUC), 33.3% and 94.35% (PU3i) represented acceptable values. After completing the requisite soldering, acceptable values were 50% and 94.35% (PUTN), 16.6% and 77.7% (PUN), 38.55% and 77.7% (PUC), and 27.75% and 94.35% (PU3i). Within the limitations of this study, it can be concluded that the premachined abutments presented more acceptable VM values. The HM values were within acceptable limits before and after the soldering procedure for most groups. Further, the soldering procedure resulted in an increase of VM in all groups.

Optimization of permeability for quality improvement by using factorial design

NASA Astrophysics Data System (ADS)

Said, Rahaini Mohd; Miswan, Nor Hamizah; Juan, Ng Shu; Hussin, Nor Hafizah; Ahmad, Aminah; Kamal, Mohamad Ridzuan Mohamad

2017-05-01

Sand castings are used worldwide by the manufacturing process in Metal Casting Industry, whereby the green sand are the commonly used sand mould type in the industry of sand casting. The defects on the surface of casting product is one of the problems in the industry of sand casting. The problems that relates to the defect composition of green sand are such as blowholes, pinholes shrinkage and porosity. Our objective is to optimize the best composition of green sand in order to minimize the occurrence of defects. Sand specimen of difference parameters (Bentonite, Green Sand, Cold dust and water) were design and prepared to undergo permeability test. The 24 factorial design experiment with four factors at difference composition were runs, and the total of 16 runs experiment were conducted. The developed models based on the experimental design necessary models were obtained. The model with a high coefficient of determination (R2=0.9841) and model for predicted and actual fitted well with the experimental data. Using the Analysis of Design Expert software, we identified that bentonite and water are the main interaction effect in the experiments. The optimal settings for green sand composition are 100g silica sand, 21g bentonite, 6.5 g water and 6g coal dust. This composition gives an effect of permeability number 598.3GP.

Fatigue behavior in rheocast aluminum 357 suspension arms using the SEED process

NASA Astrophysics Data System (ADS)

Samuel, Ehab; Zheng, Chang-Qing; Bouaicha, Amine; Bouazara, Mohamed

Extensive studies have been devoted to the use of aluminum alloys in the automotive industry, by virtue of the favourable mechanical properties that can be attained. Moreover, the aluminum casting method employed has also been the subject of scrutiny, given the multitude of casting options available. The present work serves to illustrate the advancements made in the area of rheocasting, using the SEED method, as carried out at the National Research Council Canada — Aluminum Technology Centre. The SEED (Swirled Enthalpy Equilibration Device) process, which relies on heat extraction of the liquid aluminum alloy via mechanical agitation in a confined cylinder to form the semi-solid billet, has already proven successful in producing sound aluminum castings having an excellent combination of strength and ductility. Moreover, fatigue testing on the cast alloy parts has shown enormous potential for this emerging technology.

Microstructure of As-cast Co-Cr-Mo Alloy Prepared by Investment Casting

NASA Astrophysics Data System (ADS)

Park, Jong Bum; Jung, Kyung-Hwan; Kim, Kang Min; Son, Yong; Lee, Jung-Il; Ryu, Jeong Ho

2018-04-01

The microstructure of a cobalt-base alloy (Co-Cr-Mo) obtained by an investment casting process was studied. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants owing to its high strength, good corrosion resistance, and excellent biocompatibility. This work focuses on the resulting microstructures arising from normal industrial environmental conditions. The characterization of the samples was carried out using optical microscopy, field emission scanning electron microscopy and energy-dispersive spectroscopy. In this study, the as-cast microstructure is an γ-Co (face-centered cubic) dendritic matrix with the presence of a secondary phase, such as M23C6 carbides precipitated at grain boundaries and interdendritic zones. These precipitates are the main strengthening mechanism in this type of alloy. Other minority phases, such as the σ phase, were also detected, and their presence could be linked to the manufacturing process and environment.

Characteristics of copper-clad aluminum rods prepared by horizontal continuous casting

NASA Astrophysics Data System (ADS)

Zhang, Yubo; Fu, Ying; Jie, Jinchuan; Wu, Li; Svynarenko, Kateryna; Guo, Qingtao; Li, Tingju; Wang, Tongmin

2017-11-01

An innovative horizontal continuous casting method was developed and successfully used to prepare copper-clad aluminum (CCA) rods with a diameter of 85 mm and a sheath thickness of 16 mm. The solidification structure and element distribution near the interface of the CCA ingots were investigated by means of a scanning electron microscope, an energy dispersive spectrometer, and an electron probe X-ray microanalyzer. The results showed that the proposed process can lead to a good metallurgical bond between Cu and Al. The interface between Cu and Al was a multilayered structure with a thickness of 200 μm, consisting of Cu9Al4, CuAl2, α-Al/CuAl2 eutectic, and α-Al + α-Al/CuAl2 eutectic layers from the Cu side to the Al side. The mean tensile-shear strength of the CCA sample was 45 MPa, which fulfills the requirements for the further extrusion process. The bonding and diffusion mechanisms are also discussed in this paper.

Persistent rupture terminations at a restraining bend from slip rates on the eastern Altyn Tagh fault

NASA Astrophysics Data System (ADS)

Elliott, A. J.; Oskin, M. E.; Liu-zeng, J.; Shao, Y.-X.

2018-05-01

Restraining double-bends along strike-slip faults inhibit or permit throughgoing ruptures depending on bend angle, length, and prior rupture history. Modeling predicts that for mature strike-slip faults in a regional stress regime characterized by simple shear, a restraining bend of >18° and >4 km length impedes propagating rupture. Indeed, natural evidence shows that the most recent rupture(s) of the Xorkoli section (90°-93°E) of the eastern Altyn Tagh fault (ATF) ended at large restraining bends. However, when multiple seismic cycles are considered in numerical dynamic rupture modeling, heterogeneous residual stresses enable some ruptures to propagate further, modulating whether the bends persistently serve as barriers. These models remain to be tested using observations of the cumulative effects of multiple earthquake ruptures. Here we investigate whether a large restraining double-bend on the ATF serves consistently as a barrier to rupture by measuring long-term slip rates around the terminus of its most recent surface rupture at the Aksay bend. Our results show a W-E decline in slip as the SATF enters the bend, as would be predicted from repeated rupture terminations there. Prior work demonstrated no Holocene slip on the central, most misoriented portion of the bend, while 19-79 m offsets suggest that multiple ruptures have occurred on the west side of the bend during the Holocene. Thus we conclude the gradient in the SATF's slip rate results from the repeated termination of earthquake ruptures there. However, a finite slip rate east of the bend represents the transmission of some slip, suggesting that a small fraction of ruptures may fully traverse or jump the double-bend. This agreement between natural observations of slip accumulation and multi-cycle models of fault rupture enables us to translate observed slip rates into insight about the dynamic rupture process of individual earthquakes as they encounter geometric complexities along faults.

Energy Saving Melting and Revert Reduction Technology: Improved Die Casting Process to Preserve the Life of the Inserts

DOE Office of Scientific and Technical Information (OSTI.GOV)

David Schwam, PI; Xuejun Zhu, Sr. Research Associate

2012-09-30

The goal of this project was to study the combined effects of die design, proper internal cooling and efficient die lubricants on die life. The project targeted improvements in die casting insert life by: Optomized Die Design for Reduced Surface Temperature: The life of die casting dies is significantly shorter when the die is exposed to elevated temperature for significant periods of time. Any die operated under conditions leading to surface temperature in excess of 1050oF undergoes structural changes that reduce its strength. Optimized die design can improve die life significantly. This improvement can be accomplished by means of coolingmore » lines, baffles and bubblers in the die. A key objective of the project was to establish criteria for the minimal distance of the cooling lines from the surface. This effort was supported with alloys and machining by BohlerUddeholm, Dunn Steel, HH Stark and Rex Buckeye. In plant testing and evaluation was conducted as in-kind cost share at St. Clair Die Casting. The Uddeholm Dievar steel evaluated in this program showed superior resistance to thermal fatigue resistance. Based on the experimental evidence, cooling lines could be placed as close as 0.5" from the surface. Die Life Extension by Optimized Die Lubrication: The life of die casting dies is affected by additions made to its surface with the proper lubricants. These lubricants will protect the surface from the considerable temperature peaks that occur when the molten melt enters the die. Dies will reach a significantly higher temperature without this lubricant being applied. The amount and type of the lubricant are critical variables in the die casting process. However, these lubricants must not corrode the die surface. This effort was supported with alloys and machining by BohlerUddeholm, Dunn Steel, HH Stark and Rex Buckeye. In plant testing and evaluation was conducted as in-kind cost share at St. Clair Die Casting. Chem- Trend participated in the program with die lubricants and technical support. Experiments conducted with these lubricants demonstrated good protection of the substrate steel. Graphite and boron nitride used as benchmarks are capable of completely eliminating soldering and washout. However, because of cost and environmental considerations these materials are not widely used in industry. The best water-based die lubricants evaluated in this program were capable of providing similar protection from soldering and washout. In addition to improved part quality and higher production rates, improving die casting processes to preserve the life of the inserts will result in energy savings and a reduction in environmental wastes. Improving die life by means of optimized cooling line placement, baffles and bubblers in the die will allow for reduced die temperatures during processing, saving energy associated with production. The utilization of optimized die lubricants will also reduce heat requirements in addition to reducing waste associated with soldering and washout. This new technology was predicted to result in an average energy savings of 1.1 trillion BTU's/year over a 10 year period. Current (2012) annual energy saving estimates, based on commercial introduction in 2010, a market penetration of 70% by 2020 is 1.26 trillion BTU's/year. Along with these energy savings, reduction of scrap and improvement in casting yield will result in a reduction of the environmental emissions associated with the melting and pouring of the metal which will be saved as a result of this technology. The average annual estimate of CO2 reduction per year through 2020 is 0.025 Million Metric Tons of Carbon Equivalent (MM TCE).« less

Non-graphite crucible for high temperature applications

DOEpatents

Holcombe, C.E.; Pfeiler, W.A.

1994-08-02

A multi-piece crucible for high temperature applications comprises a tubular side wall member having a lip on the inside surface and a bottom member or members forming a container for containing a melt of a material during a high temperature melt-casting operations. The multi-piece design prevents cracking of the crucible or leakage of the melt from the crucible during the melt-casting operation. The lip of the tubular member supports the bottom member. The contacting surfaces where the lip of the tubular side wall member contacts the bottom member of the multi-piece crucible contains a ceramic sealing material. The ceramic sealing material forms a seal sufficient to prevent the melt of the material from leaking out of the multi-piece crucible during the melt-casting process. The multi-piece crucible is made of a material which is chemically inert to the melt and has structural integrity at the melting point temperature of the melt, or of a material coated with such a material. 6 figs.

Non-graphite crucible for high temperature applications

DOEpatents

Holcombe, Cressie E.; Pfeiler, William A.

1994-01-01

A multi-piece crucible for high temperature applications comprises a tubular side wall member having a lip on the inside surface and a bottom member or members forming a container for containing a melt of a material during a high temperature melt-casting operations. The multi-piece design prevents cracking of the crucible or leakage of the melt from the crucible during the melt-casting operation. The lip of the tubular member supports the bottom member. The contacting surfaces where the lip of the tubular side wall member contacts the bottom member of the multi-piece crucible contains a ceramic sealing material. The ceramic sealing material forms a seal sufficient to prevent the melt of the material from leaking out of the multi-piece crucible during the melt-casting process. The multi-piece crucible is made of a material which is chemically inert to the melt and has structural integrity at the melting point temperature of the melt, or of a material coated with such a material.

Kinematic Source Rupture Process of the 2008 Iwate-Miyagi Nairiku Earthquake, a MW6.9 thrust earthquake in northeast Japan, using Strong Motion Data

NASA Astrophysics Data System (ADS)

Asano, K.; Iwata, T.

2008-12-01

The 2008 Iwate-Miyagi Nairiku earthquake (MJMA7.2) on June 14, 2008, is a thrust type inland crustal earthquake, which occurred in northeastern Honshu, Japan. In order to see strong motion generation process of this event, the source rupture process is estimated by the kinematic waveform inversion using strong motion data. Strong motion data of the K-NET and KiK-net stations and Aratozawa Dam are used. These stations are located 3-94 km from the epicenter. Original acceleration time histories are integrated into velocity and band- pass filtered between 0.05 and 1 Hz. For obtaining the detailed source rupture process, appropriate velocity structure model for Green's functions should be used. We estimated one dimensional velocity structure model for each strong motion station by waveform modeling of aftershock records. The elastic wave velocity, density, and Q-values for four sedimentary layers are assumed following previous studies. The thickness of each sedimentary layer depends on the station, which is estimated to fit the observed aftershock's waveforms by the optimization using the genetic algorithm. A uniform layered structure model is assumed for crust and upper mantle below the seismic bedrock. We succeeded to get a reasonable velocity structure model for each station to give a good fit of the main S-wave part in the observation of aftershocks. The source rupture process of the mainshock is estimated by the linear kinematic waveform inversion using multiple time windows (Hartzell and Heaton, 1983). A fault plane model is assumed following the moment tensor solution by F-net, NIED. The strike and dip angle is 209° and 51°, respectively. The rupture starting point is fixed at the hypocenter located by the JMA. The obtained source model shows a large slip area in the shallow portion of the fault plane approximately 6 km southwest of the hypocenter. The rupture of the asperity finishes within about 9 s. This large slip area corresponds to the area with surface break reported by the field survey group (e.g., AIST/GSJ, 2008), which supports the existence of the large slip close to the ground surface. But, most of surface offset found by the field survey are less than 0.5 m whereas the slip amount of the shallow asperity of the source inversion result is 3-4 m. In north of the hypocenter, the estimated slip amount is small. Slip direction is almost pure dip-slip for the entire fault (Northwest side goes up against southeast side). Total seismic moment is 2.6× 1019 Nm (MW 6.9). Acknowledgments: Strong motion data of K-NET and KiK-net operated by the National Research Institute for Earth Science and Disaster Prevention are used. Strong motion data of Aratozawa Dam obtained by Miyagi prefecture government is also used in the study.

Influence of Ni Interlayer on Microstructure and Mechanical Properties of Mg/Al Bimetallic Castings

NASA Astrophysics Data System (ADS)

Liu, Ning; Liu, Canchun; Liang, Chunyong; Zhang, Yongguang

2018-05-01

Dissimilar joining of magnesium and aluminum using a compound casting process was investigated in the present work. For the first time, a Ni interlayer prepared by plasma spraying was inserted between the two base metals to improve the interfacial characteristics. Examination of the interfacial regions using scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis, and X-ray diffraction revealed the formation of a three-layered interface between Mg and Al without the interlayer. The thickness of the interface was approximately 600 μm when the casting was performed at 700 °C and increased with increasing casting temperature. However, with the addition of the Ni interlayer, the Al-Mg reaction was successfully prevented, and metallurgical bonding between the Ni interlayer and two base metals was achieved at a casting temperature of 700 °C. Upon increasing this temperature, Mg-Ni and Al-Ni intermetallics were generated at the separate interfaces. The shear strength of the Mg/Al bimetallic castings with the Ni interlayer was substantially improved compared with that of the direct Mg/Al joint, with a maximum value of 25.4 MPa achieved at 700 °C. Fracture occurred mainly along the Mg/Ni interface for the Mg/Ni/Al multilayer structure castings.

Fold and thrust partitioning in a contracting fold belt: Insights from the 1931 Mach earthquake in Baluchistan

NASA Astrophysics Data System (ADS)

Szeliga, Walter; Bilham, Roger; Schelling, Daniel; Kakar, Din Mohamed; Lodi, Sarosh

2009-10-01

Surface deformation associated with the 27 August 1931 earthquake near Mach in Baluchistan is quantified from spirit-leveling data and from detailed structural sections of the region interpreted from seismic reflection data constrained by numerous well logs. Mean slip on the west dipping Dezghat/Bannh fault system amounted to 1.2 m on a 42 km × 72 km thrust plane with slip locally attaining 3.2 m up dip of an inferred locking line at ˜9 km depth. Slip also occurred at depths below the interseismic locking line. In contrast, negligible slip occurred in the 4 km near the interseismic locking line. The absence of slip here in the 4 years following the earthquake suggests that elastic energy there must either dissipate slowly in the interseismic cycle, or that a slip deficit remains, pending its release in a large future earthquake. Elastic models of the earthquake cycle in this fold and thrust belt suggest that slip on the frontal thrust fault is reduced by a factor of 2 to 8 compared to that anticipated from convergence of the hinterland, a partitioning process that is presumably responsible for thickening of the fold and thrust belt at the expense of slip on the frontal thrust. Near the latitude of Quetta, GPS measurements indicate that convergence is ˜5 mm/yr. Hence the minimum renewal time between earthquakes with 1.2-m mean displacement should be as little as 240 years. However, when the partitioning of fold belt convergence to frontal thrust slip is taken into account the minimum renewal time may exceed 2000 years.

Effect of Slip Time in Forming Neo-Esophageal Stenosis After Replacement of a Thoracic Esophagus With Nitinol Artificial Esophagus.

PubMed

Liang, Xian-Liang; Liang, Jian-Hui

2015-07-01

Attempts have been made to investigate the effect of slip time of nitinol artificial esophagus for forming neo-esophageal stenosis after replacement of a thoracic esophagus with nitinol artificial esophagus in 20 experimental pigs. The pigs whose slip time was less than 90 days postoperatively had severe dysphagia (Bown's III) immediately after they were fed, and the dysphagia aggravated gradually later on (Bown's III-IV). The pigs whose slip time was more than 90 days postoperatively had mild/moderate dysphagia (Bown's I-II) immediately after they were fed, and the dysphagia relieved gradually later on (Bown's II-I-0). The ratios between the diameter of neo-esophagus in different slip time and normal esophagus were 25% (at 2 months postoperatively), 58% (at 4 months postoperatively), and 93% (at 6 months postoperatively), respectively. The relationship between nitinol artificial esophagus slip time and neo-esophageal stenosis showed a positive correlation. After replacement of a thoracic esophagus with nitinol artificial esophagus, the artificial esophageal slip time not only affected the original diameter of the neo-esophagus immediately, but also affected the neo-esophageal scar stricture forming process later on. The narrowing of neo-esophagus is caused by overgrowth of scar tissue. But there is the positive correlation between artificial esophagus slip time and neo-esophageal stenosis, so this can be a way of overcoming neo-esophageal stenosis by delaying slip time of artificial esophagus. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Tape casting and partial melting of Bi-2212 thick films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buhl, D.; Lang, T.; Heeb, B.

1994-12-31

To produce Bi-2212 thick films with high critical current densities tape casting and partial melting is a promising fabrication method. Bi-2212 powder and organic additives were mixed into a slurry and tape casted onto glass by the doctor blade tape casting process. The films were cut from the green tape and partially molten on Ag foils during heat treatment. We obtained almost single-phase and well-textured films over the whole thickness of 20 {mu}m. The orientation of the (a,b)-plane of the grains were parallel to the substrate with a misalignment of less than 6{degrees}. At 77K/OT a critical current density ofmore » 15`000 A/cm{sup 2} was reached in films of the dimension 1cm x 2cm x 20{mu}m (1{mu}V/cm criterion, resistively measured). At 4K/OT the highest value was 350`000 A/cm{sup 2} (1nV/cm criterion, magnetically measured).« less

Analysis of surface scale on the Ni-based superalloy CMSX-10N and proposed mechanism of formation

NASA Astrophysics Data System (ADS)

Simmonds, S.; D'Souza, N.; Ryder, K. S.; Dong, H.

2012-01-01

There is a continuing demand to raise the operating temperature of jet engine turbine blades to meet the need for higher turbine entry temperatures (TET) in order to increase thermal efficiency and thrust. Modern, high-pressure turbine blades are made from Ni-based superalloys in single-crystal form via the investment casting process. One important post-cast surface defect, known as 'surface scale', has been investigated on the alloy CMSX-10N. This is an area of distinct discolouration of the aerofoil seen after casting. Auger electron and X-ray photoelectron spectroscopy analysis were carried out on both scaled and un-scaled areas. In the scaled region, a thin layer (~800nm) of Ni oxide is evident. In the un-scaled regions there is a thicker Al2O3 layer. It is shown that, as the blade cools during casting, differential thermal contraction of mould and alloy causes the solid blade to 'detach' from the mould in these scaled areas. The formation of Ni Oxides is facilitated by this separation.

40 CFR 464.30 - Applicability; description of the ferrous casting subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... ferrous casting subcategory. 464.30 Section 464.30 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS METAL MOLDING AND CASTING POINT SOURCE CATEGORY Ferrous Casting Subcategory § 464.30 Applicability; description of the ferrous casting subcategory. The...

Numerical Simulation of Cast Distortion in Gas Turbine Engine Components

NASA Astrophysics Data System (ADS)

Inozemtsev, A. A.; Dubrovskaya, A. S.; Dongauser, K. A.; Trufanov, N. A.

2015-06-01

In this paper the process of multiple airfoilvanes manufacturing through investment casting is considered. The mathematical model of the full contact problem is built to determine stress strain state in a cast during the process of solidification. Studies are carried out in viscoelastoplastic statement. Numerical simulation of the explored process is implemented with ProCASTsoftware package. The results of simulation are compared with the real production process. By means of computer analysis the optimization of technical process parameters is done in order to eliminate the defect of cast walls thickness variation.

Preparation and Characterization of Anode-Supported YSZ Thin Film Electrolyte by Co-Tape Casting and Co-Sintering Process

NASA Astrophysics Data System (ADS)

Liu, Q. L.; Fu, C. J.; Chan, S. H.; Pasciak, G.

2011-06-01

In this study, a co-tape casting and co-sintering process has been developed to prepare yttria-stabilized zirconia (YSZ) electrolyte films supported on Ni-YSZ anode substrates in order to substantially reduce the fabrication cost of solid oxide fuel cells (SOFC). Through proper control of the process, the anode/electrolyte bilayer structures with a size of 7.8cm × 7.8cm were achieved with good flatness. Scanning electron microscopy (SEM) observation indicated that the YSZ electrolyte film was about 16 μm in thickness, highly dense, crack free and well-bonded to the anode support. The electrochemical properties of the prepared anode-supported electrolyte film was evaluated in a button cell mode incorporating a (LaSr)MnO3-YSZ composite cathode. With humidified hydrogen as the fuel and stationary air as the oxidant, the cell demonstrated an open-circuit voltage of 1.081 V and a maximum power density of 1.01 W/cm2 at 800°C. The obtained results represent the important progress in the development of anode-supported intermediate temperature SOFC with reduced fabrication cost.

The effect of energy accumulation and boundary slip on laminar flow between rotating plates

NASA Astrophysics Data System (ADS)

Wu, Zhenpeng; Zeng, Liangcai; Chen, Keying; Jin, Xiaohong; Wu, Shiqian

2018-02-01

The poor operating conditions of fluid lubrication equipment during the start-up process are due to the resistance of the high-viscosity lubricating liquid. Moreover, the excessive reduction in fluid viscosity due to the elevated temperature resulting from power consumption during prolonged operation is not conducive to the generation of dynamic pressure. In this study, we examine the effect of energy accumulation and boundary slip on the laminar flow of a liquid between a pair of rotating plates. The experiments are conducted using a rotary rheometer, with polymethyl methacrylate (PMMA) as the thermal insulation material and polytetrafluoroethylene (PTFE) as the slip drag reduction material, and a three-dimensional simulation model is established. This model is derived by combining the energy equation including the slip length and the heat conduction equation. Thus, the temperature changes over time are predicted by this model, and the model accuracy is verified by experiments. The results reveal the following points: 1) boundary slips function as a drag reduction mechanism for short-time continuous operation; 2) under prolonged operation, the slip reduces the extent of the oil viscosity decrease and clear control of the elevated temperature by the boundary slip is observed.

Continuous Fiber Ceramic Composite (CFCC) Program: Gaseous Nitridation

DOE Office of Scientific and Technical Information (OSTI.GOV)

R. Suplinskas G. DiBona; W. Grant

2001-10-29

Textron has developed a mature process for the fabrication of continuous fiber ceramic composite (CFCC) tubes for application in the aluminum processing and casting industry. The major milestones in this project are System Composition; Matrix Formulation; Preform Fabrication; Nitridation; Material Characterization; Component Evaluation

Human mismatch repair protein hMutLα is required to repair short slipped-DNAs of trinucleotide repeats.

PubMed

Panigrahi, Gagan B; Slean, Meghan M; Simard, Jodie P; Pearson, Christopher E

2012-12-07

Mismatch repair (MMR) is required for proper maintenance of the genome by protecting against mutations. The mismatch repair system has also been implicated as a driver of certain mutations, including disease-associated trinucleotide repeat instability. We recently revealed a requirement of hMutSβ in the repair of short slip-outs containing a single CTG repeat unit (1). The involvement of other MMR proteins in short trinucleotide repeat slip-out repair is unknown. Here we show that hMutLα is required for the highly efficient in vitro repair of single CTG repeat slip-outs, to the same degree as hMutSβ. HEK293T cell extracts, deficient in hMLH1, are unable to process single-repeat slip-outs, but are functional when complemented with hMutLα. The MMR-deficient hMLH1 mutant, T117M, which has a point mutation proximal to the ATP-binding domain, is defective in slip-out repair, further supporting a requirement for hMLH1 in the processing of short slip-outs and possibly the involvement of hMHL1 ATPase activity. Extracts of hPMS2-deficient HEC-1-A cells, which express hMLH1, hMLH3, and hPMS1, are only functional when complemented with hMutLα, indicating that neither hMutLβ nor hMutLγ is sufficient to repair short slip-outs. The resolution of clustered short slip-outs, which are poorly repaired, was partially dependent upon a functional hMutLα. The joint involvement of hMutSβ and hMutLα suggests that repeat instability may be the result of aberrant outcomes of repair attempts.

Constraints on the source parameters of low-frequency earthquakes on the San Andreas Fault

USGS Publications Warehouse

Thomas, Amanda M.; Beroza, Gregory C.; Shelly, David R.

2016-01-01

Low-frequency earthquakes (LFEs) are small repeating earthquakes that occur in conjunction with deep slow slip. Like typical earthquakes, LFEs are thought to represent shear slip on crustal faults, but when compared to earthquakes of the same magnitude, LFEs are depleted in high-frequency content and have lower corner frequencies, implying longer duration. Here we exploit this difference to estimate the duration of LFEs on the deep San Andreas Fault (SAF). We find that the M ~ 1 LFEs have typical durations of ~0.2 s. Using the annual slip rate of the deep SAF and the average number of LFEs per year, we estimate average LFE slip rates of ~0.24 mm/s. When combined with the LFE magnitude, this number implies a stress drop of ~104 Pa, 2 to 3 orders of magnitude lower than ordinary earthquakes, and a rupture velocity of 0.7 km/s, 20% of the shear wave speed. Typical earthquakes are thought to have rupture velocities of ~80–90% of the shear wave speed. Together, the slow rupture velocity, low stress drops, and slow slip velocity explain why LFEs are depleted in high-frequency content relative to ordinary earthquakes and suggest that LFE sources represent areas capable of relatively higher slip speed in deep fault zones. Additionally, changes in rheology may not be required to explain both LFEs and slow slip; the same process that governs the slip speed during slow earthquakes may also limit the rupture velocity of LFEs.

Geodetically resolved slip distribution of the 27 August 2012 Mw=7.3 El Salvador earthquake

NASA Astrophysics Data System (ADS)

Geirsson, H.; La Femina, P. C.; DeMets, C.; Hernandez, D. A.; Mattioli, G. S.; Rogers, R.; Rodriguez, M.

2013-12-01

On 27 August 2012 a Mw=7.3 earthquake occurred offshore of Central America causing a small tsunami in El Salvador and Nicaragua but little damage otherwise. This is the largest magnitude earthquake in this area since 2001. We use co-seismic displacements estimated from episodic and continuous GPS station time series to model the magnitude and spatial variability of slip for this event. The estimated surface displacements are small (<2 cm) due to the distance and low magnitude of the earthquake. We use TDEFNODE to model the displacements using two different modeling approaches. In the first model, we solve for homogeneous slip on free rectangular fault(s), and in the second model we solve for distributed slip on the main thrust, realized using different slab models. The results indicate that we can match the seismic moment release, with models indicating rupture of a large area, with a low magnitude of slip. The slip is at shallow-to-intermediate depths on the main thrust off the coast of El Salvador. Additionally, we observe a deeper region of slip to the east, that reaches towards the Gulf of Fonseca between El Salvador and Nicaragua. The observed tsunami additionally indicates near-trench rupture off the coast of El Salvador. The duration of the rupturing is estimated from seismic data to be 70 s, which indicates a slow rupture process. Since the geodetic moment we obtain agrees with the seismic moment, this indicates that the earthquake was not associated with aseismic slip.

40 CFR 464.20 - Applicability; description of the copper casting subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... copper casting subcategory. 464.20 Section 464.20 Protection of Environment ENVIRONMENTAL PROTECTION... Copper Casting Subcategory § 464.20 Applicability; description of the copper casting subcategory. The... introduction of pollutants into publicly owned treatment works resulting from copper casting operations as...

40 CFR 464.10 - Applicability; description of the aluminum casting subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... aluminum casting subcategory. 464.10 Section 464.10 Protection of Environment ENVIRONMENTAL PROTECTION... Aluminum Casting Subcategory § 464.10 Applicability; description of the aluminum casting subcategory. The... introduction of pollutants into publicly owned treatment works resulting from aluminum casting operations as...

Powder processing of hybrid titanium neural electrodes

NASA Astrophysics Data System (ADS)

Lopez, Jose Luis, Jr.

A preliminary investigation into the powder production of a novel hybrid titanium neural electrode for EEG is presented. The rheological behavior of titanium powder suspensions using sodium alginate as a dispersant are examined for optimal slip casting conditions. Electrodes were slip cast and sintered at 950°C for 1 hr, 1000°C for 1, 3, and 6 hrs, and 1050°C for 1 hr. Residual porosities from sintering are characterized using Archimedes' technique and image analysis. The pore network is gel impregnated by submerging the electrodes in electrically conductive gel and placing them in a chamber under vacuum. Gel evaporation of the impregnated electrodes is examined. Electrodes are characterized in the dry and gelled states using impedance spectrometry and compared to a standard silver- silver chloride electrode. Power spectral densities for the sensors in the dry and gelled state are also compared. Residual porosities for the sintered specimens were between 50.59% and 44.81%. Gel evaporation tests show most of the impregnated gel evaporating within 20 min of exposure to atmospheric conditions with prolonged evaporation times for electrodes with higher impregnated gel mass. Impedance measurements of the produced electrodes indicate the low impedance of the hybrid electrodes are due to the increased contact area of the porous electrode. Power spectral densities of the titanium electrode behave similar to a standard silver-silver chloride electrode. Tests suggest the powder processed hybrid titanium electrode's performance is better than current dry contact electrodes and comparable to standard gelled silver-silver chloride electrodes.

Three-dimensional microstructure simulation of Ni-based superalloy investment castings

NASA Astrophysics Data System (ADS)

Pan, Dong; Xu, Qingyan; Liu, Baicheng

2011-05-01

An integrated macro and micro multi-scale model for the three-dimensional microstructure simulation of Ni-based superalloy investment castings was developed, and applied to industrial castings to investigate grain evolution during solidification. A ray tracing method was used to deal with the complex heat radiation transfer. The microstructure evolution was simulated based on the Modified Cellular Automaton method, which was coupled with three-dimensional nested macro and micro grids. Experiments for Ni-based superalloy turbine wheel investment casting were carried out, which showed a good correspondence with the simulated results. It is indicated that the proposed model is able to predict the microstructure of the casting precisely, which provides a tool for the optimizing process.

Dynamically triggered slip leading to sustained fault gouge weakening under laboratory shear conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Paul Allan

We investigate dynamic wave-triggered slip under laboratory shear conditions. The experiment is composed of a three-block system containing two gouge layers composed of glass beads and held in place by a fixed load in a biaxial configuration. When the system is sheared under steady state conditions at a normal load of 4 MPa, we find that shear failure may be instantaneously triggered by a dynamic wave, corresponding to material weakening and softening if the system is in a critical shear stress state (near failure). Following triggering, the gouge material remains in a perturbed state over multiple slip cycles as evidencedmore » by the recovery of the material strength, shear modulus, and slip recurrence time. This work suggests that faults must be critically stressed to trigger under dynamic conditions and that the recovery process following a dynamically triggered event differs from the recovery following a spontaneous event.« less

Method of casting articles of a bulk-solidifying amorphous alloy

DOEpatents

Lin, X.; Johnson, W.L.; Peker, A.

1998-08-25

A casting charge of a bulk-solidifying amorphous alloy is cast into a mold from a temperature greater than its crystallized melting temperature, and permitted to solidify to form an article. The oxygen content of the casting charge is limited to an operable level, as excessively high oxygen contents produce premature crystallization during the casting operation. During melting, the casting charge is preferably heated to a temperature above a threshold temperature to eliminate heterogeneous crystallization nucleation sites within the casting charge. The casting charge may be cast from above the threshold temperature, or it may be cooled to the casting temperature of more than the crystallized melting point but not more than the threshold temperature, optionally held at this temperature for a period of time, and thereafter cast. 8 figs.

Method of casting articles of a bulk-solidifying amorphous alloy

DOEpatents

Lin, Xianghong; Johnson, William L.; Peker, Atakan

1998-01-01

A casting charge of a bulk-solidifying amorphous alloy is cast into a mold from a temperature greater than its crystallized melting temperature, and permitted to solidify to form an article. The oxygen content of the casting charge is limited to an operable level, as excessively high oxygen contents produce premature crystallization during the casting operation. During melting, the casting charge is preferably heated to a temperature above a threshold temperature to eliminate heterogeneous crystallization nucleation sites within the casting charge. The casting charge may be cast from above the threshold temperature, or it may be cooled to the casting temperature of more than the crystallized melting point but not more than the threshold temperature, optionally held at this temperature for a period of time, and thereafter cast.

Analysis of Mold Friction in a Continuous Casting Using Wavelet Transform

NASA Astrophysics Data System (ADS)

Ma, Yong; Fang, Bohan; Ding, Qiqi; Wang, Fangyin

2018-04-01

Mold friction (MDF) is an important parameter reflecting the lubrication condition between the initial shell and the mold during continuous casting. In this article, based on practical MDF from the slab continuous casting driven by a mechanical vibration device, the characteristics of friction were analyzed by continuous wavelet transform (CWT) and discrete wavelet transform (DWT) in different casting conditions, such as normal casting, level fluctuation, and alarming of the temperature measurement system. The results show that the CWT of friction accurately captures the subtle changes in friction force, such as the periodic characteristic of MDF during normal casting and the disordered feature of MDF during level fluctuation. Most important, the results capture the occurrence of abnormal casting and display the friction frequency characteristics at this abnormal time. In addition, in this article, there are some abnormal casting conditions, and the friction signal is stable until there is a sudden large change when abnormal casting, such as split breakout and submerged entry nozzle breakage, occurs. The DWT has a good ability to capture the friction characteristics for such abnormal situations. In particular, the potential abnormal features of MDF were presented in advance, which provides strong support for identifying abnormal casting and even preventing abnormal casting.

Mathematical Modeling of the Effect of Roll Diameter on the Thermo-Mechanical Behavior of Twin Roll Cast AZ31 Magnesium Alloy Strips

NASA Astrophysics Data System (ADS)

Hadadzadeh, Amir; Wells, Mary

Although the Twin Roll Casting (TRC) process has been used in the aluminum sheet production industry for more than 60 years, the usage of this process to fabricate magnesium sheets is still at its early stages. Similar to other manufacturing processes, the development of the TRC process for magnesium alloys has followed a typical route of preliminary studies using a laboratory-scale facility, followed by pilot-scale testing and most recently attempting to use an industrial-scale twin roll caster. A powerful tool to understand and quantify the trends of the processing conditions and effects of scaling up from a laboratory size TRC machine to an industrial scale one is develop a mathematical model of the process. This can elucidate the coupled fluid-thermo-mechanical behavior of the cast strip during the solidification and then deformation stages of the process. In the present study a Thermal-Fluid-Stress model has been developed for TRC of AZ31 magnesium alloy for three roll diameters by employing the FEM commercial package ALSIM. The roll diameters were chosen as 355mm, 600mm and 1150mm. The effect of casting speed for each diameter was studied in terms of fluid flow, thermal history and stress-strain evolution in the cast strip in the roll bite region.

Analysis of four dental alloys following torch/centrifugal and induction/ vacuum-pressure casting procedures.

PubMed

Thompson, Geoffrey A; Luo, Qing; Hefti, Arthur

2013-12-01

Previous studies have shown casting methodology to influence the as-cast properties of dental casting alloys. It is important to consider clinically important mechanical properties so that the influence of casting can be clarified. The purpose of this study was to evaluate how torch/centrifugal and inductively cast and vacuum-pressure casting machines may affect the castability, microhardness, chemical composition, and microstructure of 2 high noble, 1 noble, and 1 base metal dental casting alloys. Two commonly used methods for casting were selected for comparison: torch/centrifugal casting and inductively heated/ vacuum-pressure casting. One hundred and twenty castability patterns were fabricated and divided into 8 groups. Four groups were torch/centrifugally cast in Olympia (O), Jelenko O (JO), Genesis II (G), and Liberty (L) alloys. Similarly, 4 groups were cast in O, JO, G, and L by an inductively induction/vacuum-pressure casting machine. Each specimen was evaluated for casting completeness to determine a castability value, while porosity was determined by standard x-ray techniques. Each group was metallographically prepared for further evaluation that included chemical composition, Vickers microhardness, and grain analysis of microstructure. Two-way ANOVA was used to determine significant differences among the main effects. Statistically significant effects were examined further with the Tukey HSD procedure for multiple comparisons. Data obtained from the castability experiments were non-normal and the variances were unequal. They were analyzed statistically with the Kruskal-Wallis rank sum test. Significant results were further investigated statistically with the Steel-Dwass method for multiple comparisons (α=.05). The alloy type had a significant effect on surface microhardness (P<.001). In contrast, the technique used for casting did not affect the microhardness of the test specimen (P=.465). Similarly, the interaction between the alloy and casting technique was not significant (P=.119). A high level of castability (98.5% on average) was achieved overall. The frequency of casting failures as a function of alloy type and casting method was determined. Failure was defined as a castability index score of <100%. Three of 28 possible comparisons between alloy and casting combinations were statistically significant. The results suggested that casting technique affects the castability index of alloys. Radiographic analysis detected large porosities in regions near the edge of the castability pattern and infrequently adjacent to noncast segments. All castings acquired traces of elements found in the casting crucibles. The grain size for each dental casting alloy was generally finer for specimens produced by the induction/vacuum-pressure method. The difference was substantial for JO and L. This study demonstrated a relation between casting techniques and some physical properties of metal ceramic casting alloys. Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

The Effect on Rudder Control of Slip Stream Body, and Ground Interference

NASA Technical Reports Server (NTRS)

Hood, H I; Bacon, D L

1922-01-01

This investigation was undertaken to determine the relative effects of those factors which may interfere with the rudder control of an airplane, with especial reference to the process of landing. It shows that ground interference is negligible, but that the effects of a large rounded body and of the slip stream may combine to interfere seriously with rudder control at low flying speeds and when taxiing.

Application of a Pore Fraction Hot Tearing Model to Directionally Solidified and Direct Chill Cast Aluminum Alloys

NASA Astrophysics Data System (ADS)

Dou, Ruifeng; Phillion, A. B.

2016-08-01

Hot tearing susceptibility is commonly assessed using a pressure drop equation in the mushy zone that includes the effects of both tensile deformation perpendicular to the thermal gradient as well as shrinkage feeding. In this study, a Pore Fraction hot tearing model, recently developed by Monroe and Beckermann (JOM 66:1439-1445, 2014), is extended to additionally include the effect of strain rate parallel to the thermal gradient. The deformation and shrinkage pore fractions are obtained on the basis of the dimensionless Niyama criterion and a scaling variable method. First, the model is applied to the binary Al-Cu system under conditions of directional solidification. It is shown that for the same Niyama criterion, a decrease in the cooling rate increases both the deformation and shrinkage pore fractions because of an increase in the time spent in the brittle temperature region. Second, the model is applied to the industrial aluminum alloy AA5182 as part of a finite element simulation of the Direct Chill (DC) casting process. It is shown that an increase in the casting speed during DC casting increases the deformation and shrinkage pore fractions, causing the maximum point of pore fraction to move towards the base of the casting. These results demonstrate that including the strain rate parallel to the thermal gradient significantly improves the predictive quality of hot tearing criteria based on the pressure drop equation.

Spray Deposition: A Fundamental Study of Droplet Impingement, Spreading and Consolidation

DTIC Science & Technology

1989-12-01

low alloy (HSLA) steel. Preforms of HSLA-100, a low carbon bainitic, copper precipitation strengthened HSLA steel...manufacturing process. Specifically, HSLA-100, a copper precipitation strengthened high-strength, low - alloy steel was spray cast via the Osprey’ m process...by spray casting. Preforms of HSLA-100, a low carbon bainitic, copper precipitation strengthened steel, were spray cast under differing conditions

Manufacturing and operational issues with lead-acid batteries

NASA Astrophysics Data System (ADS)

Rand, D. A. J.; Boden, D. P.; Lakshmi, C. S.; Nelson, R. F.; Prengaman, R. D.

An expert panel replies to questions on lead-acid technology and performance asked by delegates to the Ninth Asian Battery Conference. The subjects are as follows. Grid alloys: effects of calcium and tin levels on microstructure, corrosion, mechanical and electrochemical properties; effect of alloy-fabrication process on mechanical strength and corrosion resistance; low dross-make during casting of lead-calcium-tin alloys; future of book-mould casting; effect of increasing levels of silver; stability of continuously processed grids at high temperature. Negative-plate expanders: function of lignosulfonates and barium sulfate; benefits of pre-blended expanders; optimum expander formulations. Valve-regulated batteries: effect of oxygen cycle; optimum methods for float charging; charging and deep-cycle lifetimes; reliability testing.

On the origin of why static or breakloose friction is larger than kinetic friction, and how to reduce it: the role of aging, elasticity and sequential interfacial slip.

PubMed

Lorenz, B; Persson, B N J

2012-06-06

We discuss the origin of static friction and show how it can be reduced towards kinetic friction by the appropriate design of the sliding system. The basic idea is to use elastically soft solids and apply the external forces in such a way that different parts of the contacting interface start to slip at different times during the (tangential) loading process. In addition, the local slip must be large enough in order to result in a strong drop in the static friction force. We illustrate the theoretical predictions with the results of a simple model experiment.

Pneumatic gap sensor and method

DOEpatents

Bagdal, K.T.; King, E.L.; Follstaedt, D.W.

1992-03-03

An apparatus and method for monitoring and maintaining a predetermined width in the gap between a casting nozzle and a casting wheel, wherein the gap is monitored by means of at least one pneumatic gap sensor. The pneumatic gap sensor is mounted on the casting nozzle in proximity to the casting surface and is connected by means of a tube to a regulator and a transducer. The regulator provides a flow of gas through a restictor to the pneumatic gap sensor, and the transducer translates the changes in the gas pressure caused by the proximity of the casting wheel to the pneumatic gap sensor outlet into a signal intelligible to a control device. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces. The apparatus and method enables accurate monitoring of the actual casting gap in a simple and reliable manner resistant to the extreme temperatures and otherwise hostile casting environment. 6 figs.

Adhesion Casting In Low Gravity

NASA Technical Reports Server (NTRS)

Noever, David A.; Cronise, Raymond J.

1996-01-01

Adhesion casting in low gravity proposed as technique for making new and improved materials. Advantages of low-gravity adhesion casting, in comparison with adhesion casting in normal Earth gravity, comes from better control over, and greater uniformity of, thicknesses of liquid films that form on and adhere to solid surfaces during casting.

Thermal Stress Analysis for Ceramics Stalk in the Low Pressure Die Casting Machine

NASA Astrophysics Data System (ADS)

Noda, Nao-Aki; Hendra, Nao-Aki; Takase, Yasushi; Li, Wenbin

Low pressure die casting (LPDC) is defined as a net shape casting technology in which the molten metal is injected at high speeds and pressure into a metallic die. The LPDC process is playing an increasingly important role in the foundry industry as a low-cost and high-efficiency precision forming technique. The LPDC process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal by means of a pressurized gas in order to rise into a ceramic tube, which connects the die to the furnace. The ceramics tube called stalk has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the stalk is dipped into the molten aluminum. It is important to develop the design of the stalk to reduce the risk of fracture because of low fracture toughness of ceramics. In this paper, therefore, the finite element method is applied to calculate the thermal stresses when the stalk is dipped into the crucible by varying the dipping speeds and dipping directions. It is found that the thermal stress can be reduced by dipping slowly if the stalk is dipped into the crucible vertically, while the thermal stress can be reduced by dipping fast if it is dipped horizontally.

Joint Inversion of 1-Hz GPS Data and Strong Motion Records for the Rupture Process of the 2008 Iwate-Miyagi Nairiku Earthquake: Objectively Determining Relative Weighting

NASA Astrophysics Data System (ADS)

Wang, Z.; Kato, T.; Wang, Y.

2015-12-01

The spatiotemporal fault slip history of the 2008 Iwate-Miyagi Nairiku earthquake, Japan, is obtained by the joint inversion of 1-Hz GPS waveforms and near-field strong motion records. 1-Hz GPS data from GEONET is processed by GAMIT/GLOBK and then a low-pass filter of 0.05 Hz is applied. The ground surface strong motion records from stations of K-NET and Kik-Net are band-pass filtered for the range of 0.05 ~ 0.3 Hz and integrated once to obtain velocity. The joint inversion exploits a broader frequency band for near-field ground motions, which provides excellent constraints for both the detailed slip history and slip distribution. A fully Bayesian inversion method is performed to simultaneously and objectively determine the rupture model, the unknown relative weighting of multiple data sets and the unknown smoothing hyperparameters. The preferred rupture model is stable for different choices of velocity structure model and station distribution, with maximum slip of ~ 8.0 m and seismic moment of 2.9 × 1019 Nm (Mw 6.9). By comparison with the single inversion of strong motion records, the cumulative slip distribution of joint inversion shows sparser slip distribution with two slip asperities. One common slip asperity extends from the hypocenter southeastward to the ground surface of breakage; another slip asperity, which is unique for joint inversion contributed by 1-Hz GPS waveforms, appears in the deep part of fault where very few aftershocks are occurring. The differential moment rate function of joint and single inversions obviously indicates that rich high frequency waves are radiated in the first three seconds but few low frequency waves.

A novel highly porous ceramic foam with efficient thermal insulation and high temperature resistance properties fabricated by gel-casting process

NASA Astrophysics Data System (ADS)

Yu, Jiahong; Wang, Guixiang; Tang, Di; Qiu, Ya; Sun, Nali; Liu, Wenqiao

2018-01-01

The design of super thermal insulation and high-temperature resistant materials for high temperature furnaces is crucial due to the energy crisis and the huge wasting. Although it is told that numerous studies have been reported about various of thermal insulation materials prepared by different methods, the applications of yttria-stabilized zirconia (YSZ) ceramic foams fabricated through tert-butyl alcohol (TBA)-based gel-casting process in bulk thermal isolators were barely to seen. In this paper, highly porous yttria-stabilized zirconia (YSZ) ceramic foams were fabricated by a novel gel-casting method using tert-butyl alcohol (TBA) as solvent and pore-forming agent. Different raw material ratio, sintering temperature and soaking time were all investigated to achieve optimal thermal insulation and mechanical properties. We can conclude that porosity drops gradually while compressive strength increases significantly with the rising temperature from 1000-1500°C. With prolonged soaking time, there is no obvious change in porosity but compressive strength increases gradually. All specimens have uniformly distributed pores with average size of 0.5-2μm and show good structural stability at high temperature. The final obtained ceramic foams displayed an outstanding ultra-low thermal conductivity property with only 200.6 °C in cold surface while the hot side was 1000 °C (hold 60 min to keep thermal balance before testing) at the thickness of 10 mm.

Marginal adaptation and CAD-CAM technology: A systematic review of restorative material and fabrication techniques.

PubMed

Papadiochou, Sofia; Pissiotis, Argirios L

2018-04-01

The comparative assessment of computer-aided design and computer-aided manufacturing (CAD-CAM) technology and other fabrication techniques pertaining to marginal adaptation should be documented. Limited evidence exists on the effect of restorative material on the performance of a CAD-CAM system relative to marginal adaptation. The purpose of this systematic review was to investigate whether the marginal adaptation of CAD-CAM single crowns, fixed dental prostheses, and implant-retained fixed dental prostheses or their infrastructures differs from that obtained by other fabrication techniques using a similar restorative material and whether it depends on the type of restorative material. An electronic search of English-language literature published between January 1, 2000, and June 30, 2016, was conducted of the Medline/PubMed database. Of the 55 included comparative studies, 28 compared CAD-CAM technology with conventional fabrication techniques, 12 contrasted CAD-CAM technology and copy milling, 4 compared CAD-CAM milling with direct metal laser sintering (DMLS), and 22 investigated the performance of a CAD-CAM system regarding marginal adaptation in restorations/infrastructures produced with different restorative materials. Most of the CAD-CAM restorations/infrastructures were within the clinically acceptable marginal discrepancy (MD) range. The performance of a CAD-CAM system relative to marginal adaptation is influenced by the restorative material. Compared with CAD-CAM, most of the heat-pressed lithium disilicate crowns displayed equal or smaller MD values. Slip-casting crowns exhibited similar or better marginal accuracy than those fabricated with CAD-CAM. Cobalt-chromium and titanium implant infrastructures produced using a CAD-CAM system elicited smaller MD values than zirconia. The majority of cobalt-chromium restorations/infrastructures produced by DMLS displayed better marginal accuracy than those fabricated with the casting technique. Compared with copy milling, the majority of zirconia restorations/infrastructures produced by CAD-CAM milling exhibited better marginal adaptation. No clear conclusions can be drawn about the superiority of CAD-CAM milling over the casting technique and DMLS regarding marginal adaptation. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Structural control on the Tohoku earthquake rupture process investigated by 3D FEM, tsunami and geodetic data.

PubMed

Romano, F; Trasatti, E; Lorito, S; Piromallo, C; Piatanesi, A; Ito, Y; Zhao, D; Hirata, K; Lanucara, P; Cocco, M

2014-07-09

The 2011 Tohoku earthquake (Mw = 9.1) highlighted previously unobserved features for megathrust events, such as the large slip in a relatively limited area and the shallow rupture propagation. We use a Finite Element Model (FEM), taking into account the 3D geometrical and structural complexities up to the trench zone, and perform a joint inversion of tsunami and geodetic data to retrieve the earthquake slip distribution. We obtain a close spatial correlation between the main deep slip patch and the local seismic velocity anomalies, and large shallow slip extending also to the North coherently with a seismically observed low-frequency radiation. These observations suggest that the friction controlled the rupture, initially confining the deeper rupture and then driving its propagation up to the trench, where it spreads laterally. These findings are relevant to earthquake and tsunami hazard assessment because they may help to detect regions likely prone to rupture along the megathrust, and to constrain the probability of high slip near the trench. Our estimate of ~40 m slip value around the JFAST (Japan Trench Fast Drilling Project) drilling zone contributes to constrain the dynamic shear stress and friction coefficient of the fault obtained by temperature measurements to ~0.68 MPa and ~0.10, respectively.

Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Final Summary Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Thornton C

2014-03-31

Energy-Saving Melting and Revert Reduction Technology (E-SMARRT) is a balanced portfolio of R&D tasks that address energy-saving opportunities in the metalcasting industry. E-SMARRT was created to: • Improve important capabilities of castings • Reduce carbon footprint of the foundry industry • Develop new job opportunities in manufacturing • Significantly reduce metalcasting process energy consumption and includes R&D in the areas of: • Improvements in Melting Efficiency • Innovative Casting Processes for Yield Improvement/Revert Reduction • Instrumentation and Control Improvement • Material properties for Casting or Tooling Design Improvement The energy savings and process improvements developed under E-SMARRT have been mademore » possible through the unique collaborative structure of the E-SMARRT partnership. The E-SMARRT team consisted of DOE’s Office of Industrial Technology, the three leading metalcasting technical associations in the U.S: the American Foundry Society; the North American Die Casting Association; and the Steel Founders’ Society of America; and SCRA Applied R&D, doing business as the Advanced Technology Institute (ATI), a recognized leader in distributed technology management. This team provided collaborative leadership to a complex industry composed of approximately 2,000 companies, 80% of which employ less than 100 people, and only 4% of which employ more than 250 people. Without collaboration, these new processes and technologies that enable energy efficiencies and environment-friendly improvements would have been slow to develop and had trouble obtaining a broad application. The E-SMARRT R&D tasks featured low-threshold energy efficiency improvements that are attractive to the domestic industry because they do not require major capital investment. The results of this portfolio of projects are significantly reducing metalcasting process energy consumption while improving the important capabilities of metalcastings. Through June 2014, the E-SMARRT program predicts an average annual estimated savings of 59 Trillion BTUs per year over a 10 year period through Advanced Melting Efficiencies and Innovative Casting Processes. Along with these energy savings, an estimated average annual estimate of CO2 reduction per year over a ten year period is 3.56 Million Metric Tons of Carbon Equivalent (MM TCE).« less

Casting fine grained, fully dense, strong inorganic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Sam W.; Spencer, Larry S.; Phillips, Michael R.

2015-11-24

Methods and apparatuses for casting inorganic materials are provided. The inorganic materials include metals, metal alloys, metal hydrides and other materials. Thermal control zones may be established to control the propagation of a freeze front through the casting. Agitation from a mechanical blade or ultrasonic energy may be used to reduce porosity and shrinkage in the casting. After solidification of the casting, the casting apparatus may be used to anneal the cast part.

Dynamically triggered slip leading to sustained fault gouge weakening under laboratory shear conditions

DOE PAGES

Johnson, Paul Allan

2016-02-28

We investigate dynamic wave-triggered slip under laboratory shear conditions. The experiment is composed of a three-block system containing two gouge layers composed of glass beads and held in place by a fixed load in a biaxial configuration. When the system is sheared under steady state conditions at a normal load of 4 MPa, we find that shear failure may be instantaneously triggered by a dynamic wave, corresponding to material weakening and softening if the system is in a critical shear stress state (near failure). Following triggering, the gouge material remains in a perturbed state over multiple slip cycles as evidencedmore » by the recovery of the material strength, shear modulus, and slip recurrence time. This work suggests that faults must be critically stressed to trigger under dynamic conditions and that the recovery process following a dynamically triggered event differs from the recovery following a spontaneous event.« less

Accelerated nucleation of the 2014 Iquique, Chile Mw 8.2 Earthquake

PubMed Central

Kato, Aitaro; Fukuda, Jun’ichi; Kumazawa, Takao; Nakagawa, Shigeki

2016-01-01

The earthquake nucleation process has been vigorously investigated based on geophysical observations, laboratory experiments, and theoretical studies; however, a general consensus has yet to be achieved. Here, we studied nucleation process for the 2014 Iquique, Chile Mw 8.2 megathrust earthquake located within the current North Chile seismic gap, by analyzing a long-term earthquake catalog constructed from a cross-correlation detector using continuous seismic data. Accelerations in seismicity, the amount of aseismic slip inferred from repeating earthquakes, and the background seismicity, accompanied by an increasing frequency of earthquake migrations, started around 270 days before the mainshock at locations up-dip of the largest coseismic slip patch. These signals indicate that repetitive sequences of fast and slow slip took place on the plate interface at a transition zone between fully locked and creeping portions. We interpret that these different sliding modes interacted with each other and promoted accelerated unlocking of the plate interface during the nucleation phase. PMID:27109362

Rupture complexity of the Mw 8.3 sea of okhotsk earthquake: Rapid triggering of complementary earthquakes?

USGS Publications Warehouse

Wei, Shengji; Helmberger, Don; Zhan, Zhongwen; Graves, Robert

2013-01-01

We derive a finite slip model for the 2013 Mw 8.3 Sea of Okhotsk Earthquake (Z = 610 km) by inverting calibrated teleseismic P waveforms. The inversion shows that the earthquake ruptured on a 10° dipping rectangular fault zone (140 km × 50 km) and evolved into a sequence of four large sub-events (E1–E4) with an average rupture speed of 4.0 km/s. The rupture process can be divided into two main stages. The first propagated south, rupturing sub-events E1, E2, and E4. The second stage (E3) originated near E2 with a delay of 12 s and ruptured northward, filling the slip gap between E1 and E2. This kinematic process produces an overall slip pattern similar to that observed in shallow swarms, except it occurs over a compressed time span of about 30 s and without many aftershocks, suggesting that sub-event triggering for deep events is significantly more efficient than for shallow events.

Revealing transient strain in geodetic data with Gaussian process regression

NASA Astrophysics Data System (ADS)

Hines, T. T.; Hetland, E. A.

2018-03-01

Transient strain derived from global navigation satellite system (GNSS) data can be used to detect and understand geophysical processes such as slow slip events and post-seismic deformation. Here we propose using Gaussian process regression (GPR) as a tool for estimating transient strain from GNSS data. GPR is a non-parametric, Bayesian method for interpolating scattered data. In our approach, we assume a stochastic prior model for transient displacements. The prior describes how much we expect transient displacements to covary spatially and temporally. A posterior estimate of transient strain is obtained by differentiating the posterior transient displacements, which are formed by conditioning the prior with the GNSS data. As a demonstration, we use GPR to detect transient strain resulting from slow slip events in the Pacific Northwest. Maximum likelihood methods are used to constrain a prior model for transient displacements in this region. The temporal covariance of our prior model is described by a compact Wendland covariance function, which significantly reduces the computational burden that can be associated with GPR. Our results reveal the spatial and temporal evolution of strain from slow slip events. We verify that the transient strain estimated with GPR is in fact geophysical signal by comparing it to the seismic tremor that is associated with Pacific Northwest slow slip events.

A Bayesian analysis of the 2016 Pedernales (Ecuador) earthquake rupture process

NASA Astrophysics Data System (ADS)

Gombert, B.; Duputel, Z.; Jolivet, R.; Rivera, L. A.; Simons, M.; Jiang, J.; Liang, C.; Fielding, E. J.

2017-12-01

The 2016 Mw = 7.8 Pedernales earthquake is the largest event to strike Ecuador since 1979. Long period W-phase and Global CMT solutions suggest that slip is not perpendicular to the trench axis, in agreement with the convergence obliquity of the Ecuadorian subduction. In this study, we propose a new co-seismic kinematic slip model obtained from the joint inversion of multiple observations in an unregularized and fully Bayesian framework. We use a comprehensive static dataset composed of several InSAR scenes, GPS static offsets, and tsunami waveforms from two nearby DART stations. The kinematic component of the rupture process is constrained by an extensive network of High-Rate GPS and accelerometers. Our solution includes the ensemble of all plausible models that are consistent with our prior information and fit the available observations within data and prediction uncertainties. We analyse the source process in light of the historical seismicity, in particular the Mw = 7.8 1942 earthquake for which the rupture extent overlaps with the 2016 event. In addition, we conduct a probabilistic comparison of co-seismic slip with a stochastic interseismic coupling model obtained from GPS data, putting a light on the processes at play within the Ecuadorian subduction margin.

On-Line Control of Metal Processing. Report of the Committee on On-Line Control of Metal Processing

DTIC Science & Technology

1989-02-01

Materials Engineering. His work has concentrated on the electroprocessing of metals in molten salts . He is a member of TMS, AIME, ES, Canadian Institute...continuous ingot casting process with three 32 discrete control loops Figure 4-2 Controller incorporating process model 36 Figure 4-3 Real-time molten ...and others while providing a controlled macrostructure and solidification substructure. In this process, molten metal continuously flows from a

Method of casting pitch based foam

DOEpatents

Klett, James W.

2002-01-01

A process for producing molded pitch based foam is disclosed which minimizes cracking. The process includes forming a viscous pitch foam in a container, and then transferring the viscous pitch foam from the container into a mold. The viscous pitch foam in the mold is hardened to provide a carbon foam having a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts.

Very High Cycle Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy DZ4

PubMed Central

Nie, Baohua; Zhao, Zihua; Liu, Shu; Chen, Dongchu; Ouyang, Yongzhong; Hu, Zhudong; Fan, Touwen; Sun, Haibo

2018-01-01

The effect of casting pores on the very high cycle fatigue (VHCF) behavior of a directionally solidified (DS) Ni-base superalloy DZ4 is investigated. Casting and hot isostatic pressing (HIP) specimens were subjected to very high cycle fatigue loading in an ambient atmosphere. The results demonstrated that the continuously descending S-N curves were exhibited for both the casting and HIP specimens. Due to the elimination of the casting pores, the HIP samples had better fatigue properties than the casting samples. The subsurface crack initiated from the casting pore in the casting specimens at low stress amplitudes, whereas fatigue crack initiated from crystallographic facet decohesion for the HIP specimens. When considering the casting pores as initial cracks, there exists a critical stress intensity threshold ranged from 1.1 to 1.3 MPam, below which fatigue cracks may not initiate from the casting pores. Furthermore, the effect of the casting pores on the fatigue limit is estimated based on a modified El Haddad model, which is in good agreement with the experimental results. Fatigue life for both the casting and HIP specimens is well predicted using the Fatigue Indicator Parameter (FIP) model. PMID:29320429

Rapid prototype fabrication processes for high-performance thrust cells

NASA Technical Reports Server (NTRS)

Hunt, K.; Chwiedor, T.; Diab, J.; Williams, R.

1994-01-01

The Thrust Cell Technologies Program (Air Force Phillips Laboratory Contract No. F04611-92-C-0050) is currently being performed by Rocketdyne to demonstrate advanced materials and fabrication technologies which can be utilized to produce low-cost, high-performance thrust cells for launch and space transportation rocket engines. Under Phase 2 of the Thrust Cell Technologies Program (TCTP), rapid prototyping and investment casting techniques are being employed to fabricate a 12,000-lbf thrust class combustion chamber for delivery and hot-fire testing at Phillips Lab. The integrated process of investment casting directly from rapid prototype patterns dramatically reduces design-to-delivery cycle time, and greatly enhances design flexibility over conventionally processed cast or machined parts.

Investigation on Simultaneous Effects of Shot Peen and Austenitizing Time and Temperature on Grain Size and Microstructure of Austenitic Manganese Steel (Hadfield)

NASA Astrophysics Data System (ADS)

Beheshti, M.; Zabihiazadboni, M.; Ismail, M. C.; Kakooei, S.; Shahrestani, S.

2018-03-01

Optimal conditions to increase life time of casting parts have been investigated by applying various cycles of heat treatment and shot peening on Hadfield steel surface. Metallographic and SEM microstructure examinations were used to determine the effects of shot peen, austenitizing time and temperature simultaneously. The results showed that with increasing austenitizing time and temperature of casting sample, carbides resolved in austenite phase and by further increase of austenitizing temperature and time, the austenite grain size becomes larger. Metallographic images illustrated that shot peening on Hadfield steel surface; Austenite - Martensite transformation has not occurred, but its matrix hardened through twining formation process.

Processing and Characterization of Functionally Graded Aluminum (A319)—SiCp Metallic Composites by Centrifugal Casting Technique

NASA Astrophysics Data System (ADS)

Jayakumar, E.; Jacob, Jibin C.; Rajan, T. P. D.; Joseph, M. A.; Pai, B. C.

2016-08-01

Functionally graded materials (FGM) are successfully adopted for the design and fabrication of engineering components with location-specific properties. The present study describes the processing and characterization of A319 Aluminum functionally graded metal matrix composites (FGMMC) with 10 and 15 wt pct SiCp reinforcements. The liquid stir casting method is used for composite melt preparation followed by FGMMC formation by vertical centrifugal casting method. The process parameters used are the mold preheating temperature of 523 K (250 °C), melt pouring temperature of 1013 K (740 °C), and mold rotation speed of 1300 rpm. The study analyzes the distribution and concentration of reinforcement particles in the radial direction of the FGMMC disk along with the effects of gradation on density, hardness, mechanical strength, the variation in coefficient of thermal expansion and the wear resistance properties at different zones. Microstructures of FGMMC reveal an outward radial gradient distribution of reinforcements forming different zones. Namely, matrix-rich inner, transition, particles-rich outer, and chill zone of a few millimeters thick at the outer most periphery of the casting are formed. From 10-FGM, a radial shift in the position of SiCp maxima is observed in 15-FGM casting. The mechanical characterization depicts enhanced properties for the particle-rich zone. The hardness shows a graded nature in correlation with particle concentration and a maximum of 94.4 HRB has been obtained at the particle-rich region of 15-FGM. In the particle-rich zone, the lowest CTE value of 20.1 µm/mK is also observed with a compressive strength of 650 MPa and an ultimate tensile strength of 279 MPa. The wear resistance is higher at the particle-rich zone of the FGMMC.

Experimental and Numerical Modeling of Fluid Flow Processes in Continuous Casting: Results from the LIMMCAST-Project

NASA Astrophysics Data System (ADS)

Timmel, K.; Kratzsch, C.; Asad, A.; Schurmann, D.; Schwarze, R.; Eckert, S.

2017-07-01

The present paper reports about numerical simulations and model experiments concerned with the fluid flow in the continuous casting process of steel. This work was carried out in the LIMMCAST project in the framework of the Helmholtz alliance LIMTECH. A brief description of the LIMMCAST facilities used for the experimental modeling at HZDR is given here. Ultrasonic and inductive techniques and the X-ray radioscopy were employed for flow measurements or visualizations of two-phase flow regimes occurring in the submerged entry nozzle and the mold. Corresponding numerical simulations were performed at TUBAF taking into account the dimensions and properties of the model experiments. Numerical models were successfully validated using the experimental data base. The reasonable and in many cases excellent agreement of numerical with experimental data allows to extrapolate the models to real casting configurations. Exemplary results will be presented here showing the effect of electromagnetic brakes or electromagnetic stirrers on the flow in the mold or illustrating the properties of two-phase flows resulting from an Ar injection through the stopper rod.

CONTROLLING ODOROUS EMISSIONS FROM IRON FOUNDRIES

EPA Science Inventory

The report discusses the control of odorous emissions from iron foundries. he main process sources of odors in iron foundries are mold and core making, casting, and sand shakeout. he odors are usually caused by chemicals, which may be present as binders and other additives to the...

Fabricating CAD/CAM Implant-Retained Mandibular Bar Overdentures: A Clinical and Technical Overview.

PubMed

Goo, Chui Ling; Tan, Keson Beng Choon

2017-01-01

This report describes the clinical and technical aspects in the oral rehabilitation of an edentulous patient with knife-edge ridge at the mandibular anterior edentulous region, using implant-retained overdentures. The application of computer-aided design and computer-aided manufacturing (CAD/CAM) in the fabrication of the overdenture framework simplifies the laboratory process of the implant prostheses. The Nobel Procera CAD/CAM System was utilised to produce a lightweight titanium overdenture bar with locator attachments. It is proposed that the digital workflow of CAD/CAM milled implant overdenture bar allows us to avoid numerous technical steps and possibility of casting errors involved in the conventional casting of such bars.

Scale-Dependent Friction and Damage Interface law: implications for effective earthquake rupture dynamics and radiation

NASA Astrophysics Data System (ADS)

Festa, Gaetano; Vilotte, Jean-Pierre; Raous, Michel; Henninger, Carole

2010-05-01

Propagation and radiation of an earthquake rupture is commonly considered as a friction dominated process on fault surfaces. Friction laws, such as the slip weakening and the rate-and-state laws are widely used in the modeling of the earthquake rupture process. These laws prescribe the traction evolution versus slip, slip rate and potentially other internal variables. They introduce a finite cohesive length scale over which the fracture energy is released. However faults are finite-width interfaces with complex internal structures, characterized by highly damaged zones embedding a very thin principal slip interface where most of the dynamic slip localizes. Even though the rupture process is generally investigated at wavelengths larger than the fault zone thickness, which should justify a formulation based upon surface energy, a consistent homogeneization, a very challenging problem, is still missing. Such homogeneization is however be required to derive the consistent form of an effective interface law, as well as the appropriate physical variables and length scales, to correctly describe the coarse-grained dissipation resulting from surface and volumetric contributions at the scale of the fault zone. In this study, we investigate a scale-dependent law, introduced by Raous et al. (1999) in the context of adhesive material interfaces, that takes into account the transition between a damage dominated and a friction dominated state. Such a phase-field formalism describes this transition through an order parameter. We first compare this law to standard slip weakening friction law in terms of the rupture nucleation. The problem is analyzed through the representation of the solution of the quasi-static elastic problem onto the Chebyshev polynomial basis, generalizing the Uenishi-Rice solution. The nucleation solutions, at the onset of instability, are then introduced as initial conditions for the study of the dynamic rupture propagation, in the case of in-plane rupture, using high-order Spectral Element Methods and non-smooth contact mechanics. In particular, we investigate the implications of this new interface law in terms of the rupture propagation and arrest. Special attention is focused on radiation and supershear transition. Comparison with the classical slip weakening friction law is provided. Finally, first results toward a dynamic consistent homogeneization of damaged fault zones will be discussed. Raous, M., Cangémi, L. and Cocou, M. (1999). A consistent model coupling adhesion, friction and unilateral contact', Computer Methods in Applied Mechanics and Engineering, Vol. 177, pp.383-399.

Rupture process of the 2016 Mw 7.8 Ecuador earthquake from joint inversion of InSAR data and teleseismic P waveforms

NASA Astrophysics Data System (ADS)

Yi, Lei; Xu, Caijun; Wen, Yangmao; Zhang, Xu; Jiang, Guoyan

2018-01-01

The 2016 Ecuador earthquake ruptured the Ecuador-Colombia subduction interface where several historic megathrust earthquakes had occurred. In order to determine a detailed rupture model, Interferometric Synthetic Aperture Radar (InSAR) images and teleseismic data sets were objectively weighted by using a modified Akaika's Bayesian Information Criterion (ABIC) method to jointly invert for the rupture process of the earthquake. In modeling the rupture process, a constrained waveform length method, unlike the traditional subjective selected waveform length method, was used since the lengths of inverted waveforms were strictly constrained by the rupture velocity and rise time (the slip duration time). The optimal rupture velocity and rise time of the earthquake were estimated from grid search, which were determined to be 2.0 km/s and 20 s, respectively. The inverted model shows that the event is dominated by thrust movement and the released moment is 5.75 × 1020 Nm (Mw 7.77). The slip distribution extends southward along the Ecuador coast line in an elongated stripe at a depth between 10 and 25 km. The slip model is composed of two asperities and slipped over 4 m. The source time function is approximate 80 s that separated into two segments corresponding to the two asperities. The small magnitude of the slip occurred in the updip section of the fault plane resulted in small tsunami waves that were verified by observations near the coast. We suggest a possible situation that the rupture zone of the 2016 earthquake is likely not overlapped with that of the 1942 earthquake.

Pneumatic gap sensor and method

DOEpatents

Bagdal, Karl T.; King, Edward L.; Follstaedt, Donald W.

1992-01-01

An apparatus and method for monitoring and maintaining a predetermined width in the gap between a casting nozzle and a casting wheel, wherein the gap is monitored by means of at least one pneumatic gap sensor. The pneumatic gap sensor is mounted on the casting nozzle in proximity to the casting surface and is connected by means of a tube to a regulator and a transducer. The regulator provides a flow of gas through a restictor to the pneumatic gap sensor, and the transducer translates the changes in the gas pressure caused by the proximity of the casting wheel to the pneumatic gap sensor outlet into a signal intelligible to a control device. The relative positions of the casting nozzle and casting wheel can thereby be selectively adjusted to continually maintain a predetermined distance between their adjacent surfaces. The apparatus and method enables accurate monitoring of the actual casting gap in a simple and reliable manner resistant to the extreme temperatures and otherwise hostile casting environment.

Laboratory constraints on models of earthquake recurrence

NASA Astrophysics Data System (ADS)

Beeler, N. M.; Tullis, Terry; Junger, Jenni; Kilgore, Brian; Goldsby, David

2014-12-01

In this study, rock friction "stick-slip" experiments are used to develop constraints on models of earthquake recurrence. Constant rate loading of bare rock surfaces in high-quality experiments produces stick-slip recurrence that is periodic at least to second order. When the loading rate is varied, recurrence is approximately inversely proportional to loading rate. These laboratory events initiate due to a slip-rate-dependent process that also determines the size of the stress drop and, as a consequence, stress drop varies weakly but systematically with loading rate. This is especially evident in experiments where the loading rate is changed by orders of magnitude, as is thought to be the loading condition of naturally occurring, small repeating earthquakes driven by afterslip, or low-frequency earthquakes loaded by episodic slip. The experimentally observed stress drops are well described by a logarithmic dependence on recurrence interval that can be cast as a nonlinear slip predictable model. The fault's rate dependence of strength is the key physical parameter. Additionally, even at constant loading rate the most reproducible laboratory recurrence is not exactly periodic, unlike existing friction recurrence models. We present example laboratory catalogs that document the variance and show that in large catalogs, even at constant loading rate, stress drop and recurrence covary systematically. The origin of this covariance is largely consistent with variability of the dependence of fault strength on slip rate. Laboratory catalogs show aspects of both slip and time predictability, and successive stress drops are strongly correlated indicating a "memory" of prior slip history that extends over at least one recurrence cycle.

Characterization of Ni-Cr alloys using different casting techniques and molds.

PubMed

Chen, Wen-Cheng; Teng, Fu-Yuan; Hung, Chun-Cheng

2014-02-01

This study differentiated the mechanical properties of nickel-chromium (Ni-Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni-Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, "casting mold," significantly influenced all mechanical properties. The graphite mold casting of the Ni-Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni-Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties. Copyright © 2013 Elsevier B.V. All rights reserved.

Passive bookshelf faulting driven by gravitational spreading as the cause of the tiger-stripe-fracture formation and development in the South Polar Terrain of Enceladus

NASA Astrophysics Data System (ADS)

Yin, A.; Pappalardo, R. T.

2013-12-01

Detailed photogeologic mapping of the tiger-stripe fractures in the South Polar Terrain (SPT) of Enceladus indicates that these structures are left-slip faults and terminate at hook-shaped fold-thrust zones and/or Y-shaped horsetail splay-fault zones. The semi-square-shaped tectonic domain that hosts the tiger-stripe faults is bounded by right-slip and left-slip faults on the north and south edges and fold-thrust and extensional zones on the western and eastern edges. We explain the above observations by a passive bookshelf-faulting model in which individual tiger-stripe faults are bounded by deformable wall rocks accommodating distributed deformation. Based on topographic data, we suggest that gravitational spreading had caused the SPT to spread unevenly from west to east. This process was accommodated by right-slip and left-slip faulting on the north and south sides and thrusting and extension along the eastern and southern margins of the tiger-stripe tectonic domain. The uneven spreading, expressed by a gradual northward increase in the number of extensional faults and thrusts/folds along the western and eastern margins, was accommodated by distributed right-slip simple shear across the whole tiger-stripe tectonic domain. This mode of deformation in turn resulted in the development of a passive bookshelf-fault system characterized by left-slip faulting on individual tiger-stripe fractures.

Combined Mechanical and Electrical Study of Polymers of Biological Origin

NASA Astrophysics Data System (ADS)

Zsoldos, G.; Szoda, K.; Marossy, K.

2017-02-01

Thermally Simulated Depolarization Current measurement is an excellent but not widely used method for identifying relaxation processes in polymers. The DMA method is used here to analyze the mechanical changes depend on temperature in biopolymers. The two techniques take advantage of the energy changes involved in the various phase transitions of certain polymer molecules. This allows for several properties of the material to be ascertained; melting points, enthalpies of melting, crystallization temperatures, glass transition temperatures and degradation temperatures. The examined biopolymer films are made from biological materials such as proteins and polysaccharides. These materials have gained wide usage in pharmaceutical, medical and food areas. The uses of biopolymer films depend on their structure and mechanical properties. This work is based on pectin and gelatin films. The films were prepared by casting. The casting technique used aqueous solutions in each case of sample preparation. The manufacturing process of the pectin and gelatin films was a single stage solving process.

Tribological and Wear Performance of Nanocomposite PVD Hard Coatings Deposited on Aluminum Die Casting Tool.

PubMed

Paiva, Jose Mario; Fox-Rabinovich, German; Locks Junior, Edinei; Stolf, Pietro; Seid Ahmed, Yassmin; Matos Martins, Marcelo; Bork, Carlos; Veldhuis, Stephen

2018-02-28

In the aluminum die casting process, erosion, corrosion, soldering, and die sticking have a significant influence on tool life and product quality. A number of coatings such as TiN, CrN, and (Cr,Al)N deposited by physical vapor deposition (PVD) have been employed to act as protective coatings due to their high hardness and chemical stability. In this study, the wear performance of two nanocomposite AlTiN and AlCrN coatings with different structures were evaluated. These coatings were deposited on aluminum die casting mold tool substrates (AISI H13 hot work steel) by PVD using pulsed cathodic arc evaporation, equipped with three lateral arc-rotating cathodes (LARC) and one central rotating cathode (CERC). The research was performed in two stages: in the first stage, the outlined coatings were characterized regarding their chemical composition, morphology, and structure using glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. Surface morphology and mechanical properties were evaluated by atomic force microscopy (AFM) and nanoindentation. The coating adhesion was studied using Mersedes test and scratch testing. During the second stage, industrial tests were carried out for coated die casting molds. In parallel, tribological tests were also performed in order to determine if a correlation between laboratory and industrial tests can be drawn. All of the results were compared with a benchmark monolayer AlCrN coating. The data obtained show that the best performance was achieved for the AlCrN/Si₃N₄ nanocomposite coating that displays an optimum combination of hardness, adhesion, soldering behavior, oxidation resistance, and stress state. These characteristics are essential for improving the die mold service life. Therefore, this coating emerges as a novelty to be used to protect aluminum die casting molds.

Tribological and Wear Performance of Nanocomposite PVD Hard Coatings Deposited on Aluminum Die Casting Tool

PubMed Central

Fox-Rabinovich, German; Locks Junior, Edinei; Stolf, Pietro; Matos Martins, Marcelo

2018-01-01

In the aluminum die casting process, erosion, corrosion, soldering, and die sticking have a significant influence on tool life and product quality. A number of coatings such as TiN, CrN, and (Cr,Al)N deposited by physical vapor deposition (PVD) have been employed to act as protective coatings due to their high hardness and chemical stability. In this study, the wear performance of two nanocomposite AlTiN and AlCrN coatings with different structures were evaluated. These coatings were deposited on aluminum die casting mold tool substrates (AISI H13 hot work steel) by PVD using pulsed cathodic arc evaporation, equipped with three lateral arc-rotating cathodes (LARC) and one central rotating cathode (CERC). The research was performed in two stages: in the first stage, the outlined coatings were characterized regarding their chemical composition, morphology, and structure using glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. Surface morphology and mechanical properties were evaluated by atomic force microscopy (AFM) and nanoindentation. The coating adhesion was studied using Mersedes test and scratch testing. During the second stage, industrial tests were carried out for coated die casting molds. In parallel, tribological tests were also performed in order to determine if a correlation between laboratory and industrial tests can be drawn. All of the results were compared with a benchmark monolayer AlCrN coating. The data obtained show that the best performance was achieved for the AlCrN/Si3N4 nanocomposite coating that displays an optimum combination of hardness, adhesion, soldering behavior, oxidation resistance, and stress state. These characteristics are essential for improving the die mold service life. Therefore, this coating emerges as a novelty to be used to protect aluminum die casting molds. PMID:29495620

High-velocity frictional properties of chert in the Jurassic accretionary complex, central Japan

NASA Astrophysics Data System (ADS)

Motohashi, G.; Oohashi, K.; Ujiie, K.

2017-12-01

Chert is one of the main components in accretionary complexes. Previous friction experiments on quartz-rich rocks at slip rates of 0.1-100 mm/s revealed that fault weakening was caused by a thixotropic behavior of silica gel [Goldsby and Tullis, 2002; Di Toro et al., 2004; Hayashi and Tsutsumi, 2010]. We conducted high-velocity friction experiments on chert at a slip rate of 1.3 m/s and normal stresses of 5-13 MPa under room humidity conditions and examined the resultant microstructures. During experiments, temperatures were measured using a high-resolution infrared thermal-imaging camera, and the process of shearing was monitored by a digital video camera. The samples for experiments were collected from the host rock (gray chert) of the thrust fault in the Jurassic accretionary complex, central Japan. Experimental data indicated that slip strengthening occurred after first slip weakening. This was followed by second slip weakening toward a steady-state friction, with maximum temperature being less than 1200 °C. The melt patches developed during slip strengthening, while the growth of melt layer was recognized during and after second slip weakening. The melt patches included little chert fragments, and the color of the chert surrounding melt patches was changed to dark, possibly representing thermal alteration of quartz grains. After second slip weakening, the volume fraction of chert fragments in the melt layer increased, and the chert fragments and the wall rocks adjacent to the melt layer were intensely cracked. These features indicated that the growth of melt layer was accompanied by the incorporation of cracked wall rocks, suggesting that off-fault damage may be linked to the slip behavior during and after second slip weakening. Goldsby, D. L., T. E. Tullis (2002), Geophys. Res. Lett., 29(17), 1844. Di Toro, G., D. L. Goldsby, T. E. Tullis (2004), Nature, 427, 436-439. Hayashi, N., A. Tsutsumi (2010), Geophys. Res. Lett., 37, L12305.

Structural control on the Tohoku earthquake rupture process investigated by 3D FEM, tsunami and geodetic data

PubMed Central

Romano, F.; Trasatti, E.; Lorito, S.; Piromallo, C.; Piatanesi, A.; Ito, Y.; Zhao, D.; Hirata, K.; Lanucara, P.; Cocco, M.

2014-01-01

The 2011 Tohoku earthquake (Mw = 9.1) highlighted previously unobserved features for megathrust events, such as the large slip in a relatively limited area and the shallow rupture propagation. We use a Finite Element Model (FEM), taking into account the 3D geometrical and structural complexities up to the trench zone, and perform a joint inversion of tsunami and geodetic data to retrieve the earthquake slip distribution. We obtain a close spatial correlation between the main deep slip patch and the local seismic velocity anomalies, and large shallow slip extending also to the North coherently with a seismically observed low-frequency radiation. These observations suggest that the friction controlled the rupture, initially confining the deeper rupture and then driving its propagation up to the trench, where it spreads laterally. These findings are relevant to earthquake and tsunami hazard assessment because they may help to detect regions likely prone to rupture along the megathrust, and to constrain the probability of high slip near the trench. Our estimate of ~40 m slip value around the JFAST (Japan Trench Fast Drilling Project) drilling zone contributes to constrain the dynamic shear stress and friction coefficient of the fault obtained by temperature measurements to ~0.68 MPa and ~0.10, respectively. PMID:25005351

Large and primarily updip afterslip following the 2012 Mw 7.6 Nicoya, Costa Rica, earthquake

NASA Astrophysics Data System (ADS)

Hobbs, T. E.; Kyriakopoulos, C.; Newman, A. V.; Protti, M.; Yao, D.

2017-07-01

We present detailed surface measurements of the first 3.5 years of postseismic deformation following the 5 September 2012 moment magnitude (Mw) 7.6 Nicoya, Costa Rica, earthquake. The dominant signal in the first 2.5 years is uniform horizontal trenchward motion totaling 7-26 cm across 40 stations. Trenchward velocity is strongly diminished by mid-2014 and appears by 2016 to have begun reversing. We invert the first 2.5 years to determine the corresponding afterslip on a detailed 3-D interface. Results show significant afterslip both updip and downdip of the main coseismic rupture zone, with as much as 1.7 m of offset in two patches at 15-20 km depth and immediately updip of the maximum coseismic slip. This updip slip represents an important mechanism to address unrelieved interseismic locking, although sufficient strain energy remains to generate up to a Mw 7.1 event near the coastline. The afterslip patches are anticorrelated with strongly clustered aftershocks at the same depth, which is indicative of varying frictional behavior along strike. An additional patch of slip is colocated with reoccurring slow-slip events beneath the Gulf of Nicoya. The magnitude of the observed slip, however, cannot be sufficiently explained by the known slow-slip events. Ongoing measurements will be crucial to understanding the relocking process in Nicoya.

Grain Refinement and Improvement of Solidification Defects in Direct-Chill Cast Billets of A4032 Alloy by Melt Conditioning

NASA Astrophysics Data System (ADS)

Li, Hu-Tian; Zhao, Pizhi; Yang, Rongdong; Patel, Jayesh B.; Chen, Xiangfu; Fan, Zhongyun

2017-10-01

Melt-conditioned, direct-chill (MC-DC) casting is an emerging technology to manipulate the solidification process by melt conditioning via intensive shearing in the sump during DC casting to tailor the solidification microstructure and defect formation. When using MC-DC casting technology in an industrial scale DC cast billet of an A4032 aluminum alloy, significant grain refinement and uniform microstructure can be achieved in the primary α-Al phase with fine secondary dendritic arm spacing (SDAS). Improved macrosegregation is quantitatively characterized and correlated with the suppression of channel segregation. The mechanisms for the prevention of channel segregation are attributed to the increased local cooling rate in the liquid-solid phase region in the sump and the formation of fine equiaxed dendritic grains under intensive melt shearing during MC-DC casting. A critical cooling rate has been identified to be around 0.5 to 1 K/s (°C/s) for the channel segregation to happen in the investigated alloy based on quantitative metallographic results of SDAS. Reduction and refinement of microporosity is attributed to the improved permeability in the liquid-solid phase region estimated by the Kozeny-Carman relationship. The potential improvement in the mechanical properties achievable in MC-DC cast billets is indicated by the finer and more uniform forging streamline in the forgings of MC-DC cast billet.

Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys.

PubMed

Hong, Jianping; Ma, Dexin; Wang, Jun; Wang, Fu; Sun, Baode; Dong, Anping; Li, Fei; Bührig-Polaczek, Andreas

2016-11-16

Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS) and single crystal (SX) hollow turbine blades. In order to investigate the location of freckle occurrence in superalloys, superalloy CM247 LC was directionally solidified in an industrial-sized Bridgman furnace. Instead of ceramic cores, Alumina tubes were used inside of the casting specimens. It was found that freckles occur not only on the casting external surfaces, but also appear near the internal interfaces between the ceramic core and superalloys. Meanwhile, the size, initial position, and area of freckle were investigated in various diameters of the specimens. The initial position of the freckle chain reduces when the diameter of the rods increase. Freckle area follows a linear relationship in various diameters and the average freckle fraction is 1.1% of cross sectional area of casting specimens. The flow of liquid metal near the interfaces was stronger than that in the interdendritic region in the mushy zone, and explained why freckle tends to occur on the outer or inner surfaces of castings. This new phenomenon suggests that freckles are more likely to occur on the outer or inner surfaces of the hollow turbine blades.

Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys

PubMed Central

Hong, Jianping; Ma, Dexin; Wang, Jun; Wang, Fu; Sun, Baode; Dong, Anping; Li, Fei; Bührig-Polaczek, Andreas

2016-01-01

Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS) and single crystal (SX) hollow turbine blades. In order to investigate the location of freckle occurrence in superalloys, superalloy CM247 LC was directionally solidified in an industrial-sized Bridgman furnace. Instead of ceramic cores, Alumina tubes were used inside of the casting specimens. It was found that freckles occur not only on the casting external surfaces, but also appear near the internal interfaces between the ceramic core and superalloys. Meanwhile, the size, initial position, and area of freckle were investigated in various diameters of the specimens. The initial position of the freckle chain reduces when the diameter of the rods increase. Freckle area follows a linear relationship in various diameters and the average freckle fraction is 1.1% of cross sectional area of casting specimens. The flow of liquid metal near the interfaces was stronger than that in the interdendritic region in the mushy zone, and explained why freckle tends to occur on the outer or inner surfaces of castings. This new phenomenon suggests that freckles are more likely to occur on the outer or inner surfaces of the hollow turbine blades. PMID:28774050

Laser welding of removable partial denture frameworks.

PubMed

Brudvik, James S; Lee, Seungbum; Croshaw, Steve N; Reimers, Donald L; Reimers, Dave L

2008-01-01

To identify and measure distortions inherent in the casting process of a Class III mandibular cobalt-chromium (Co-Cr) framework to illustrate the problems faced by the laboratory technician and the clinician and to measure the changes that occur during the correction of the fit discrepancy using laser welding. Five identical castings of a Co-Cr alloy partial denture casting were made and measured between 3 widely separated points using the x, y, and z adjustments of a Nikon Measurescope. The same measurements were made after each of the following clinical and laboratory procedures: sprue removal, sectioning of the casting into 3 parts through the posterior meshwork, fitting the segments to the master cast, picking up the segments using resin, and laser welding of the 3 segments. Measurements of all 5 castings showed a cross-arch decrease after sprue removal, an increase after fitting the segments to the master cast, and a slight decrease after resin pickup and laser welding. Within the limitations of this study, the findings suggest that precise tooth-frame relations can be established by resin pickup and laser welding of segments of Co-Cr removable partial denture frameworks.

Influence of anode thickness on the power output of solid oxide fuel cells with (La,Sr)(Co,Fe)-type cathode

NASA Astrophysics Data System (ADS)

Menzler, Norbert H.; Haanappel, Vincent A. C.

The influence of the thickness of the anode (functional layer) on the power output of anode-supported solid oxide fuel cells with a lanthanum-strontium-cobalt-ferrite cathode was investigated. The anode was applied by vacuum slip casting and the thickness varied between 1 and 22 μm. All other material and microstructural parameters were kept constant. Single cells with dimensions of 50 mm × 50 mm and with an active cathode area of 40 mm × 40 mm were manufactured and tested in an alumina housing with air as oxidant and hydrogen with 3% water vapour as the fuel gas. Results have shown that SOFCs with anodes between 1 and 13 μm have slightly better performance than those with thicker anodes (∼1.7 A cm -2 versus 1.5 A cm -2 at 800 °C and 0.7 V). The current densities were discussed with respect to cell area specific resistance, helium leak rate of the half-cell, and microstructure.

Formation of Hot Tear Under Controlled Solidification Conditions

NASA Astrophysics Data System (ADS)

Subroto, Tungky; Miroux, Alexis; Bouffier, Lionel; Josserond, Charles; Salvo, Luc; Suéry, Michel; Eskin, Dmitry G.; Katgerman, Laurens

2014-06-01

Aluminum alloy 7050 is known for its superior mechanical properties, and thus finds its application in aerospace industry. Vertical direct-chill (DC) casting process is typically employed for producing such an alloy. Despite its advantages, AA7050 is considered as a "hard-to-cast" alloy because of its propensity to cold cracking. This type of cracks occurs catastrophically and is difficult to predict. Previous research suggested that such a crack could be initiated by undeveloped hot tears (microscopic hot tear) formed during the DC casting process if they reach a certain critical size. However, validation of such a hypothesis has not been done yet. Therefore, a method to produce a hot tear with a controlled size is needed as part of the verification studies. In the current study, we demonstrate a method that has a potential to control the size of the created hot tear in a small-scale solidification process. We found that by changing two variables, cooling rate and displacement compensation rate, the size of the hot tear during solidification can be modified in a controlled way. An X-ray microtomography characterization technique is utilized to quantify the created hot tear. We suggest that feeding and strain rate during DC casting are more important compared with the exerted force on the sample for the formation of a hot tear. In addition, we show that there are four different domains of hot-tear development in the explored experimental window—compression, microscopic hot tear, macroscopic hot tear, and failure. The samples produced in the current study will be used for subsequent experiments that simulate cold-cracking conditions to confirm the earlier proposed model.

Numerical simulation of the solidification microstructure of a 17-4PH stainless steel investment casting and its experimental verification

NASA Astrophysics Data System (ADS)

Li, You Yun; Tsai, DeChang; Hwang, Weng Sing

2008-06-01

The purpose of this study is to develop a technique of numerically simulating the microstructure of 17-4PH (precipitation hardening) stainless steel during investment casting. A cellular automation (CA) algorithm was adopted to simulate the nucleation and grain growth. First a calibration casting was made, and then by comparing the microstructures of the calibration casting with those simulated using different kinetic growth coefficients (a2, a3) in CA, the most appropriate set of values for a2 and a3 would be obtained. Then, this set of values was applied to the microstructure simulation of a separate casting, where the casting was actually made. Through this approach, this study has arrived at a set of growth kinetic coefficients from the calibration casting: a2 is 2.9 × 10-5, a3 is 1.49 × 10-7, which is then used to predict the microstructure of the other test casting. Consequently, a good correlation has been found between the microstructure of actual 17-4PH casting and the simulation result.

Unified law of evolution of experimental gouge-filled fault for fast and slow slip events at slider frictional experiments

NASA Astrophysics Data System (ADS)

Ostapchuk, Alexey; Saltykov, Nikolay

2017-04-01

Excessive tectonic stresses accumulated in the area of rock discontinuity are released while a process of slip along preexisting faults. Spectrum of slip modes includes not only creeps and regular earthquakes but also some transitional regimes - slow-slip events, low-frequency and very low-frequency earthquakes. However, there is still no agreement in Geophysics community if such fast and slow events have mutual nature [Peng, Gomberg, 2010] or they present different physical phenomena [Ide et al., 2007]. Models of nucleation and evolution of fault slip events could be evolved by laboratory experiments in which regularities of shear deformation of gouge-filled fault are investigated. In the course of the work we studied deformation regularities of experimental fault by slider frictional experiments for development of unified law of evolution of fault and revelation of its parameters responsible for deformation mode realization. The experiments were conducted as a classic slider-model experiment, in which block under normal and shear stresses moves along interface. The volume between two rough surfaces was filled by thin layer of granular matter. Shear force was applied by a spring which deformed with a constant rate. In such experiments elastic energy was accumulated in the spring, and regularities of its releases were determined by regularities of frictional behaviour of experimental fault. A full spectrum of slip modes was simulated in laboratory experiments. Slight change of gouge characteristics (granule shape, content of clay), viscosity of interstitial fluid and level of normal stress make it possible to obtained gradual transformation of the slip modes from steady sliding and slow slip to regular stick-slip, with various amplitude of 'coseismic' displacement. Using method of asymptotic analogies we have shown that different slip modes can be specified in term of single formalism and preparation of different slip modes have uniform evolution law. It is shown that shear stiffness of experimental fault is the parameter, which control realization of certain slip modes. It is worth to be mentioned that different serious of transformation is characterized by functional dependences, which have general view and differ only in normalization factors. Findings authenticate that slow and fast slip events have mutual nature. Determination of fault stiffness and testing of fault gouge allow to estimate intensity of seismic events. The reported study was funded by RFBR according to the research project № 16-05-00694.

A transparent model of the human scala tympani cavity.

PubMed

Rebscher, S J; Talbot, N; Bruszewski, W; Heilmann, M; Brasell, J; Merzenich, M M

1996-01-01

A dimensionally accurate clear model of the human scala tympani has been produced to evaluate the insertion and position of clinically applied intracochlear electrodes for electrical stimulation. Replicates of the human scala tympani were made from low melting point metal alloy (LMA) and from polymethylmeth-acrylate (PMMA) resin. The LMA metal casts were embedded in blocks of epoxy and in clear silicone rubber. After removal of the metal alloy, a cavity was produced that accurately models the human scala tympani. Investment casting molds were made from the PMMA scala tympani casts to enable production of multiple LMA casts from which identical models were fabricated. Total dimensional distortion of the LMA casting process was less than 1% in length and 2% in diameter. The models have been successfully integrated into the design process for the iterative development of advanced intracochlear electrode arrays at UCSF. These fabrication techniques are applicable to a wide range of biomedical design problems that require modelling of visually obscured cavities.

Influence of Cobalt on the Properties of Load-Sensitive Magnesium Alloys

PubMed Central

Klose, Christian; Demminger, Christian; Mroz, Gregor; Reimche, Wilfried; Bach, Friedrich-Wilhelm; Maier, Hans Jürgen; Kerber, Kai

2013-01-01

In this study, magnesium is alloyed with varying amounts of the ferromagnetic alloying element cobalt in order to obtain lightweight load-sensitive materials with sensory properties which allow an online-monitoring of mechanical forces applied to components made from Mg-Co alloys. An optimized casting process with the use of extruded Mg-Co powder rods is utilized which enables the production of magnetic magnesium alloys with a reproducible Co concentration. The efficiency of the casting process is confirmed by SEM analyses. Microstructures and Co-rich precipitations of various Mg-Co alloys are investigated by means of EDS and XRD analyses. The Mg-Co alloys' mechanical strengths are determined by tensile tests. Magnetic properties of the Mg-Co sensor alloys depending on the cobalt content and the acting mechanical load are measured utilizing the harmonic analysis of eddy-current signals. Within the scope of this work, the influence of the element cobalt on magnesium is investigated in detail and an optimal cobalt concentration is defined based on the performed examinations. PMID:23344376

Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications

PubMed Central

Jung, Hyun-Do; Lee, Hyun; Kim, Hyoun-Ee; Koh, Young-Hag; Song, Juha

2015-01-01

Biometal systems have been widely used for biomedical applications, in particular, as load-bearing materials. However, major challenges are high stiffness and low bioactivity of metals. In this study, we have developed a new method towards fabricating a new type of bioactive and mechanically reliable porous metal scaffolds-densified porous Ti scaffolds. The method consists of two fabrication processes, 1) the fabrication of porous Ti scaffolds by dynamic freeze casting, and 2) coating and densification of the porous scaffolds. The dynamic freeze casting method to fabricate porous Ti scaffolds allowed the densification of porous scaffolds by minimizing the chemical contamination and structural defects. The densification process is distinctive for three reasons. First, the densification process is simple, because it requires a control of only one parameter (degree of densification). Second, it is effective, as it achieves mechanical enhancement and sustainable release of biomolecules from porous scaffolds. Third, it has broad applications, as it is also applicable to the fabrication of functionally graded porous scaffolds by spatially varied strain during densification. PMID:26709604

40 CFR 464.16 - Pretreatment standards for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... GUIDELINES AND STANDARDS METAL MOLDING AND CASTING POINT SOURCE CATEGORY Aluminum Casting Subcategory § 464... CFR part 403 and achieve the following pretreatment standards for new sources. (a) Casting Cleaning...) 0.114 0.0431 (b) Casting Quench Operations. PSNS Pollutant or pollutant property Maximum for any 1...

Mechanical joining of materials with limited ductility: Analysis of process-induced defects

NASA Astrophysics Data System (ADS)

Jäckel, M.; Coppieters, S.; Hofmann, M.; Vandermeiren, N.; Landgrebe, D.; Debruyne, D.; Wallmersberger, T.; Faes, K.

2017-10-01

The paper shows experimental and numerical analyses of the clinching process of 6xxx series aluminum sheets in T6 condition and the self-pierce riveting process of an aluminum die casting. In the experimental investigations the damage behavior of the materials when using different tool parameters is analyzed. The focus of the numerical investigations is the damage prediction by a comparison of different damage criteria. Moreover, strength-and fatigue tests were carried out to investigate the influence of the joining process-induced damages on the strength properties of the joints.

Thermomechanical properties and fracture of resin-bonded-sand cores - Experimental study and application in aluminium foundry

NASA Astrophysics Data System (ADS)

Menet, Claire; Reynaud, Pascal; Fantozzi, Gilbert; Thibault, Delphine; Laforêt, Adrien

2017-06-01

Sand cores are used to produce internal cavities of metallic cast parts with complex shapes like automotive cylinder heads. Foundry cores are granular materials made of sand grains aggregated with binder bridges. In the cold box coring process, the binder is a polyurethane resin. It is noteworthy that during the casting of the liquid metal, the polymer binder is seriously damaged. This kind of materials has been poorly investigated so far. This study aims for a better understanding of the mechanical behaviour and fracture of cores subjected to various loads and thermal ageing. Particularly, the focus is on the decoring step, which consists in removing the sand by hammering and vibration of the metallic part after casting. This major project, generated from the collaboration of the aluminum casting company Montupet, and two laboratories Centre des Matériaux (CdM) and MATEIS, includes both experimental and numerical activities in order to model the decoring step of cylinder heads based on empiric data. Here, the experimental part of the work is presented.

Directing 101.

ERIC Educational Resources Information Center

Pintoff, Ernest

Providing an introduction to anyone considering directing as a field of study or career, this book takes a broad look at the process of directing and encourages students and professionals alike to look outside of the movie industry for inspiration. Chapters in the book discuss selecting and acquiring material; budgeting and financing; casting and…

Advanced separators based on aromatic polymer for high energy density lithium batteries

DOEpatents

Zhang, Zhengcheng; Woo, Jung-Je; Amine, Khalil

2017-03-21

A process includes casting a solution including poly(phenylene oxide), inorganic nanoparticles, a solvent, and a non-solvent on a substrate; and removing the solvent to form a porous film; wherein: the porous film is configured for use as a porous separator for a lithium ion battery.

Process for Forming a High Temperature Single Crystal Canted Spring

NASA Technical Reports Server (NTRS)

DeMange, Jeffrey J (Inventor); Ritzert, Frank J (Inventor); Nathal, Michael V (Inventor); Dunlap, Patrick H (Inventor); Steinetz, Bruce M (Inventor)

2017-01-01

A process for forming a high temperature single crystal canted spring is provided. In one embodiment, the process includes fabricating configurations of a rapid prototype spring to fabricate a sacrificial mold pattern to create a ceramic mold and casting a canted coiled spring to form at least one canted coil spring configuration based on the ceramic mold. The high temperature single crystal canted spring is formed from a nickel-based alloy containing rhenium using the at least one coil spring configuration.

Complex rupture process of the Mw 7.8, 2016, Kaikoura earthquake, New Zealand, and its aftershock sequence

NASA Astrophysics Data System (ADS)

Cesca, S.; Zhang, Y.; Mouslopoulou, V.; Wang, R.; Saul, J.; Savage, M.; Heimann, S.; Kufner, S.-K.; Oncken, O.; Dahm, T.

2017-11-01

The M7.8 Kaikoura Earthquake that struck the northeastern South Island, New Zealand, on November 14, 2016 (local time), is one of the largest ever instrumentally recorded earthquakes in New Zealand. It occurred at the southern termination of the Hikurangi subduction margin, where the subducting Pacific Plate transitions into the dextral Alpine transform fault. The earthquake produced significant distributed uplift along the north-eastern part of the South Island, reaching a peak amplitude of ∼8 m, which was accompanied by large (≥10 m) horizontal coseismic displacements at the ground surface along discrete active faults. The seismic waveforms' expression of the main shock indicate a complex rupture process. Early automated centroid moment tensor solutions indicated a strong non-double-couple term, which supports a complex rupture involving multiple faults. The hypocentral distribution of aftershocks, which appears diffuse over a broad region, clusters spatially along lineaments with different orientations. A key question of global interest is to shed light on the mechanism with which such a complex rupture occurred, and whether the underlying plate-interface was involved in the rupture. The consequences for seismic hazard of such a distributed, shallow faulting is important to be assessed. We perform a broad seismological analysis, combining regional and teleseismic seismograms, GPS and InSAR, to determine the rupture process of the main shock and moment tensors of 118 aftershocks down to Mw 4.2. The joint interpretation of the main rupture and aftershock sequence allow reconstruction of the geometry, and suggests sequential activation and slip distribution on at least three major active fault domains. We find that the rupture nucleated as a weak strike-slip event along the Humps Fault, which progressively propagated northward onto a shallow reverse fault, where most of the seismic moment was released, before it triggered slip on a second set of strike-slip faults at the northern end of the rupture. The northern and southern strike-slip fault domains have the same orientation but are spatially separated by >15 km. In our model, the low angle splay thrust fault is located above the slab and connects the strike-slip faults kinematically. During the aftershock phase, the entire fault system remained active.

High-purity silica reflecting heat shield development

NASA Technical Reports Server (NTRS)

Congdon, W. M.

1974-01-01

A high-purity, fused-silica reflecting heat shield for the thermal protection of outer-planet probes was developed. Factors that strongly influence the performance of a silica heat shield were studied. Silica-bonded silica configurations, each prepared by a different technique, were investigated and rated according to its relative merits. Slip-casting was selected as the preferred fabrication method because it produced good reflectivity and good strength, and is relatively easy to scale up for a full-size outer-planet probe. The slips were cast using a variety of different particle sizes: continuous particle-size slips; monodisperse particle-size slips; and blends of monodisperse particle-size slips were studied. In general, smaller particles gave the highest reflectance. The monodisperse slips as well as the blend slips gave a higher reflectance than the continuous particle-size slips. An upgraded and fused natural quartz was used to study the effects of microstructure on reflectance and as the baseline to ascertain the increase in reflectance obtained from using a higher-purity synthetic material.

Cast aluminium single crystals cross the threshold from bulk to size-dependent stochastic plasticity

NASA Astrophysics Data System (ADS)

Krebs, J.; Rao, S. I.; Verheyden, S.; Miko, C.; Goodall, R.; Curtin, W. A.; Mortensen, A.

2017-07-01

Metals are known to exhibit mechanical behaviour at the nanoscale different to bulk samples. This transition typically initiates at the micrometre scale, yet existing techniques to produce micrometre-sized samples often introduce artefacts that can influence deformation mechanisms. Here, we demonstrate the casting of micrometre-scale aluminium single-crystal wires by infiltration of a salt mould. Samples have millimetre lengths, smooth surfaces, a range of crystallographic orientations, and a diameter D as small as 6 μm. The wires deform in bursts, at a stress that increases with decreasing D. Bursts greater than 200 nm account for roughly 50% of wire deformation and have exponentially distributed intensities. Dislocation dynamics simulations show that single-arm sources that produce large displacement bursts halted by stochastic cross-slip and lock formation explain microcast wire behaviour. This microcasting technique may be extended to several other metals or alloys and offers the possibility of exploring mechanical behaviour spanning the micrometre scale.

The Microstructure and Physical Properties of Incinerated Paper-Cullet-Clay Ceramics

NASA Astrophysics Data System (ADS)

Sahar, M. R.; Hamzah, K.; Rohani, M. S.; Samah, K. A.; Razi, M. M.

A series of ceramic based on (x) incinerated recycle paper - (80-x) cullet - 20 Kaolin clay (where 10×45 wt%) has successfully been made by slip casting technique followed by sintering at 1000 °C. The actual composition of ceramic is analyzed using Energy Dispersive of X-Ray (EDAX) while the phase existence is determined using X-Ray Diffraction (XRD) technique. Their microstructural morphology is observed under Scanning Electron Microscope (SEM) and the physical properties are measured in term of their thermal shrinkage and hardness. It is found that the ceramic contain mostly of Silica and the phase is dominated by the existence of Quartz (SiO2), Wollastonite (CaSiO3) and Anorthite (Ca(Al2SiO8)). The SEM micrograph shows that the morphology is dominated by the existence of granular structure, and then become smoother as the cullet level is further increased. It is also found out that the thermal shrinkage is in the range 18% - 6.5% while the hardness is in the range of 152MPa- 1.463 GPa depending on composition.

Geologic continuous casting below continental and deep-sea detachment faults and at the striated extrusion of Sacsayhuaman, Peru

USGS Publications Warehouse

Spencer, J.E.

1999-01-01

In the common type of industrial continuous casting, partially molten metal is extruded from a vessel through a shaped orifice called a mold in which the metal assumes the cross-sectional form of the mold as it cools and solidifies. Continuous casting can be sustained as long as molten metal is supplied and thermal conditions are maintained. I propose that a similar process produced parallel sets of grooves in three geologic settings, as follows: (1) corrugated metamorphic core complexes where mylonized mid-crustal rocks were exhumed by movement along low-angle normal faults known as detachment faults; (2) corrugated submarine surfaces where ultramafic and mafic rocks were exhumed by normal faulting within oceanic spreading centers; and (3) striated magma extrusions exemplified by the famous grooved outcrops at the Inca fortress of Sacsayhuaman in Peru. In each case, rocks inferred to have overlain the corrugated surface during corrugation genesis molded and shaped a plastic to partially molten rock mass as it was extruded from a moderate- to high-temperature reservoir.

Development of High-Performance Cast Crankshafts. Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Mark E

The objective of this project was to develop technologies that would enable the production of cast crankshafts that can replace high performance forged steel crankshafts. To achieve this, the Ultimate Tensile Strength (UTS) of the new material needs to be 850 MPa with a desired minimum Yield Strength (YS; 0.2% offset) of 615 MPa and at least 10% elongation. Perhaps more challenging, the cast material needs to be able to achieve sufficient local fatigue properties to satisfy the durability requirements in today’s high performance gasoline and diesel engine applications. The project team focused on the development of cast steel alloysmore » for application in crankshafts to take advantage of the higher stiffness over other potential material choices. The material and process developed should be able to produce high-performance crankshafts at no more than 110% of the cost of current production cast units, perhaps the most difficult objective to achieve. To minimize costs, the primary alloy design strategy was to design compositions that can achieve the required properties with minimal alloying and post-casting heat treatments. An Integrated Computational Materials Engineering (ICME) based approach was utilized, rather than relying only on traditional trial-and-error methods, which has been proven to accelerate alloy development time. Prototype melt chemistries designed using ICME were cast as test specimens and characterized iteratively to develop an alloy design within a stage-gate process. Standard characterization and material testing was done to validate the alloy performance against design targets and provide feedback to material design and manufacturing process models. Finally, the project called for Caterpillar and General Motors (GM) to develop optimized crankshaft designs using the final material and manufacturing processing path developed. A multi-disciplinary effort was to integrate finite element analyses by engine designers and geometry-specific casting simulations with existing materials models to optimize crankshaft cost and performance. Prototype crankshafts of the final design were to be produced and validated using laboratory bench testing and on-engine durability testing. ICME process simulation tools were used to investigate a broad range of processing concepts. These concepts included casting orientation, various mold and core materials, and various filling and feeding strategies. Each crankshaft was first simulated without gating and risers, which is termed natural solidification. The natural solidification results were used as a baseline for strategy development of each concept. Casting process simulations and ICME tools were proven to be reasonable predictors of real world results. Potential alloys were developed that could meet the project material property goals with appropriate normalization and temper treatments. For the alloys considered, post-normalization temper treatments proved to be necessary to achieve the desired yield strengths and elongations and appropriate heat treatments were designed using ICME tools. The experimental data of all the alloys were analyzed in combination with ICME tools to establish chemistry-process-structure relations. Several GM small gas engine (SGE) crankshafts were successfully cast in sand molds using two different sprue, runner, gate, riser, chill designs. These crankshafts were cast in two different steel alloys developed during the project, but casting finishing (e.g. riser removal) remains a cost challenge. A long list of future work was left unfinished when this project was unexpectedly terminated.« less

40 CFR 721.10667 - Slimes and sludges, aluminum and iron casting, wastewater treatment, solid waste.

Code of Federal Regulations, 2014 CFR

2014-07-01

... casting, wastewater treatment, solid waste. 721.10667 Section 721.10667 Protection of Environment... iron casting, wastewater treatment, solid waste. (a) Chemical substance and significant new uses... and iron casting, wastewater treatment, solid waste (PMN P-12-560; CAS No. 1391739-82-4; chemical...

Potential Technology Transfer to the DoD Unmanned Ground Vehicle Program.

DTIC Science & Technology

1996-10-01

Germany. This process combines x-ray lithography, galvanic casting, and micromolding technology and can be used to produce a variety of sensors and...whether circulation is being obstructed by atherosclerosis . Finally, work is being done at the University of Minnesota on a microrobotic device

46 CFR 56.70-1 - General.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., Assembly and Erection § 56.70-1 General. (a) The following generally applies to all types of welding, such as stud welding, casting repair welding and all processes of fabrication welding. Where the detailed requirements are not appropriate to a particular process, alternatives must be approved by the Marine Safety...

Marginal accuracy of nickel chromium copings fabricated by conventional and accelerated casting procedures, produced with ringless and metal ring investment procedures: A comparative in vitro study.

PubMed

Alex, Deepa; Shetty, Y Bharath; Miranda, Glynis Anita; Prabhu, M Bharath; Karkera, Reshma

2015-01-01

Conventional investing and casting techniques are time-consuming and usually requires 2-4 h for completion. Accelerated nonstandard, casting techniques have been reported to achieve similar quality results in significantly less time, namely, in 30-40 min. During casting, it is essential to achieve compensation for the shrinkage of solidifying alloy by investment expansion. The metal casting ring restricts the thermal expansion of investment because the thermal expansion of the ring is lesser than that of the investment. The use of casting ring was challenged with the introduction of the ringless technique. A total of 40 test samples of nickel chromium (Ni-Cr) cast copings were obtained from the patterns fabricated using inlay casting wax. The 20 wax patterns were invested using metal ring and 20 wax patterns were invested using the ringless investment system. Of both the groups, 10 samples underwent conventional casting, and the other 10 underwent accelerated casting. The patterns were casted using the induction casting technique. All the test samples of cast copings were evaluated for vertical marginal gaps at four points on the die employing a stereo optical microscope. The vertical marginal discrepancy data obtained were tabulated. Mean and standard deviations were obtained. Vertical discrepancies were analyzed using analysis of variance and Tukey honestly significantly different. The data obtained were found to be very highly significant (P < 0.001). Mean vertical gap was the maximum for Group II (53.64 μm) followed by Group IV (47.62 μm), Group I (44.83 μm) and Group III (35.35 μm). The Ni-Cr cast copings fabricated with the conventional casting using ringless investment system showed significantly better marginal fit than that of cast copings fabricated from conventional and accelerated casting with metal ring investment and accelerated casting using ringless investment since those copings had shown the least vertical marginal discrepancies among the four methods evaluated in this study.

Steady, modest slip over multiple earthquake cycles on the Owens Valley and Little Lake fault zones

NASA Astrophysics Data System (ADS)

Amos, C. B.; Haddon, E. K.; Burgmann, R.; Zielke, O.; Jayko, A. S.

2015-12-01

A comprehensive picture of current plate-boundary deformation requires integration of short-term geodetic records with longer-term geologic strain. Comparing rates of deformation across these time intervals highlights potential time-dependencies in both geodetic and geologic records and yields critical insight into the earthquake deformation process. The southern Walker Lane Belt in eastern California represents one location where short-term strain recorded by geodesy apparently outpaces longer-term geologic fault slip measured from displaced rocks and landforms. This discrepancy persists both for individual structures and across the width of the deforming zone, where ~1 cm/yr of current dextral shear exceeds Quaternary slip rates summed across individual faults. The Owens Valley and Little Lake fault systems form the western boundary of the southern Walker Lane and host a range of published slip rate estimates from ~1 - 7 mm/yr over varying time intervals based on both geodetic and geologic measurements. New analysis of offset geomorphic piercing lines from airborne lidar and field measurements along the Owens Valley fault provides a snapshot of deformation during individual earthquakes and over many seismic cycles. Viewed in context of previously reported ages from pluvial and other landforms in Owens Valley, these offsets suggest slip rates of ~0.6 - 1.6 mm/yr over the past 103 - 105 years. Such rates agree with similar estimates immediately to the south on the Little Lake fault, where lidar measurements indicate dextral slip averaging ~0.6 - 1.3 mm/yr over comparable time intervals. Taken together, these results suggest steady, modest slip in the absence of significant variations over the Mid-to-Late Quaternary for a ~200 km span of the southwestern Walker Lane. Our findings argue against the presence of long-range fault interactions and slip-rate variations for this portion of the larger, regional fault network. This result also suggests that faster slip-rate estimates from geodetic measurements reflect transients over much shorter time scales. Additionally, the persistence of relatively faster geodetic shear in comparison with time-averaged fault slip leaves open the possibility of significant off-fault deformation or slip on subsidiary structures across the Owens Valley.

Worm melt fracture and fast die build-up at high shear rates in extrusion blow molding of large drums

NASA Astrophysics Data System (ADS)

Inn, Yong Woo; Sukhadia, Ashish M.

2017-05-01

In the extrusion blow molding process of high density polyethylene (HDPE) for making of large size drums, string-like defects, which are referred to as worm melt fracture in the industry, are often observed on the extrudate surface. Such string-like defects in various shapes and sizes are observed in capillary extrusion at very high shear rates after the slip-stick transition. The HDPE resin with broader molecular weight distribution (MWD) exhibits a greater degree of worm melt fracture while the narrow MWD PE resin, which has higher slip velocity and a uniform slip layer, shows a lesser degree of worm melt fracture. It is hypothesized that the worm melt fracture is related to fast die build-up and cohesive slip layer, a failure within the polymer melts at an internal surface. If the cohesive slip layer at an internal surface emerges out from the die, it can be attached on the surface of extrudate as string-like defects, the worm melt fracture. The resin having more small chains and lower plateau modulus can be easier to have such an internal failure and consequently exhibit more "worm" defects.

A Numerical Simulation of Transport Phenomena During the Horizontal Single Belt Casting Process Using an Inclined Feeding System

NASA Astrophysics Data System (ADS)

Xu, Mianguang; Isac, Mihaiela; Guthrie, Roderick I. L.

2018-06-01

Horizontal single belt casting (HSBC) has great potential to replace current conventional continuous casting (CCC) processes for sheet metal production, by directly casting 3 to 1 mm sheet for the automobile industry. In the present paper, two-dimensional mathematical models were developed to study transport phenomena, for the case of an inclined wall feeding system for a liquid aluminum wrought alloy (AA6111). Based on the commercial software ANSYS FLUENT 14.5 and user-defined functions, a two-layer turbulence model was used to examine the fluid flow emanating from a slot nozzle set above a water-cooled, high-speed, steel belt. The Volume of Fluid (VOF) method was used to predict the shape of the melt-air interface. A transformed coordinate system ( x', y') was established in order to analyze the fluid flow on the inclined wall of the feeding system. The total pressure gauge gradient ( ∂p total/ ∂x) was used to describe the behavior of the melt film inside the slot nozzle of the head box. The modeling results show that during the melt film falling process, the total gauge pressure varies within the slot nozzle, which can decrease the stability of the falling film. The first impingement between the falling film and the inclined refractory wall of the feeding system gives rise to a local oscillation, and this influences the stability of the melt film moving downwards. At the rear meniscus position between the inclined wall and the moving belt, there is a clear vibration of the air-melt interface, together with a recirculation zone. The weak vibration of the air-melt interface could be induced by the periodic variation of the melt-air interface. Moreover, the formation of tiny air pockets is predicted. Finally, on the inclined wall of the feeding system, a suitable length of the transition area is needed to avoid over-acceleration of the melt film due to the force of gravity.

Drug-printing by flexographic printing technology--a new manufacturing process for orodispersible films.

PubMed

Janssen, Eva Maria; Schliephacke, Ralf; Breitenbach, Armin; Breitkreutz, Jörg

2013-01-30

Orodispersible films (ODFs) are intended to disintegrate within seconds when placed onto the tongue. The common way of manufacturing is the solvent casting method. Flexographic printing on drug-free ODFs is introduced as a highly flexible and cost-effective alternative manufacturing method in this study. Rasagiline mesylate and tadalafil were used as model drugs. Printing of rasagiline solutions and tadalafil suspensions was feasible. Up to four printing cycles were performed. The possibility to employ several printing cycles enables a continuous, highly flexible manufacturing process, for example for individualised medicine. The obtained ODFs were characterised regarding their mechanical properties, their disintegration time, API crystallinity and homogeneity. Rasagiline mesylate did not recrystallise after the printing process. Relevant film properties were not affected by printing. Results were comparable to the results of ODFs manufactured with the common solvent casting technique, but the APIs are less stressed through mixing, solvent evaporation and heat. Further, loss of material due to cutting jumbo and daughter rolls can be reduced. Therefore, a versatile new manufacturing technology particularly for processing high-potent low-dose or heat sensitive drugs is introduced in this study. Copyright © 2012 Elsevier B.V. All rights reserved.

Energy efficient engine high-pressure turbine single crystal vane and blade fabrication technology report

NASA Technical Reports Server (NTRS)

Giamei, A. F.; Salkeld, R. W.; Hayes, C. W.

1981-01-01

The objective of the High-Pressure Turbine Fabrication Program was to demonstrate the application and feasibility of Pratt & Whitney Aircraft-developed two-piece, single crystal casting and bonding technology on the turbine blade and vane configurations required for the high-pressure turbine in the Energy Efficient Engine. During the first phase of the program, casting feasibility was demonstrated. Several blade and vane halves were made for the bonding trials, plus solid blades and vanes were successfully cast for materials evaluation tests. Specimens exhibited the required microstructure and chemical composition. Bonding feasibility was demonstrated in the second phase of the effort. Bonding yields of 75 percent for the vane and 30 percent for the blade were achieved, and methods for improving these yield percentages were identified. A bond process was established for PWA 1480 single crystal material which incorporated a transient liquid phase interlayer. Bond properties were substantiated and sensitivities determined. Tooling die materials were identified, and an advanced differential thermal expansion tooling concept was incorporated into the bond process.

Bioinspired Diatomite Membrane with Selective Superwettability for Oil/Water Separation.

PubMed

Lo, Yu-Hsiang; Yang, Ching-Yu; Chang, Haw-Kai; Hung, Wei-Chen; Chen, Po-Yu

2017-05-03

Membranes with selective superwettability for oil/water separation have received significant attention during the past decades. Hierarchical structures and surface roughness are believed to improve the oil repellency and the stability of Cassie-Baxter state. Diatoms, unicellular photosynthetic algae, possess sophisticated skeletal shells (called frustules) which are made of hydrated silica. Motivated by the hierarchical micro- and nanoscale features of diatom, we fabricate a hierarchical diatomite membrane which consists of aligned micro-sized channels by the freeze casting process. The fine nano-porous structures of frustules are well preserved after the post sintering process. The bioinspired diatomite membrane performs both underwater superoleophobicity and superhydrophobicity under various oils. Additionally, we demonstrate the highly efficient oil/water separation capabililty of the membranes in various harsh environments. The water flux can be further adjusted by tuning the cooling rates. The eco-friendly and robust bioinspired membranes produced by the simple, cost-effective freeze casting method can be potentially applied for large scale and efficient oil/water separation.

A Numerical Simulation of Transport Phenomena During the Horizontal Single Belt Casting Process Using an Inclined Feeding System

NASA Astrophysics Data System (ADS)

Xu, Mianguang; Isac, Mihaiela; Guthrie, Roderick I. L.

2018-03-01

Horizontal single belt casting (HSBC) has great potential to replace current conventional continuous casting (CCC) processes for sheet metal production, by directly casting 3 to 1 mm sheet for the automobile industry. In the present paper, two-dimensional mathematical models were developed to study transport phenomena, for the case of an inclined wall feeding system for a liquid aluminum wrought alloy (AA6111). Based on the commercial software ANSYS FLUENT 14.5 and user-defined functions, a two-layer turbulence model was used to examine the fluid flow emanating from a slot nozzle set above a water-cooled, high-speed, steel belt. The Volume of Fluid (VOF) method was used to predict the shape of the melt-air interface. A transformed coordinate system (x', y') was established in order to analyze the fluid flow on the inclined wall of the feeding system. The total pressure gauge gradient (∂p total/∂x) was used to describe the behavior of the melt film inside the slot nozzle of the head box. The modeling results show that during the melt film falling process, the total gauge pressure varies within the slot nozzle, which can decrease the stability of the falling film. The first impingement between the falling film and the inclined refractory wall of the feeding system gives rise to a local oscillation, and this influences the stability of the melt film moving downwards. At the rear meniscus position between the inclined wall and the moving belt, there is a clear vibration of the air-melt interface, together with a recirculation zone. The weak vibration of the air-melt interface could be induced by the periodic variation of the melt-air interface. Moreover, the formation of tiny air pockets is predicted. Finally, on the inclined wall of the feeding system, a suitable length of the transition area is needed to avoid over-acceleration of the melt film due to the force of gravity.

Novel Approach for Modeling of Nonuniform Slag Layers and Air Gap in Continuous Casting Mold

NASA Astrophysics Data System (ADS)

Wang, Xudong; Kong, Lingwei; Yao, Man; Zhang, Xiaobing

2017-02-01

Various kinds of surface defects on the continuous casting slab usually originate from nonuniform heat transfer and mechanical behavior, especially during the initial solidification inside the mold. In this article, a model-coupled inverse heat transfer problem incorporating the effect of slag layers and air gap is developed to study the nonuniform distribution of liquid slag, solid slag, and air gap layers. The model considers not only the formation and evolution of slag layers and air gap but also the temperatures in the mold copper as measured by thermocouples. The simulation results from the model and the measured temperatures from experiments are shown to be in good agreement with each other. At the casting speed of 0.65 m/min, the liquid slag film disappears and transforms into solid slag entirely at about 400 mm away from meniscus, and an air gap begins to form. Until the mold exit, the maximum thickness of the solid slag layer and air gap gradually increases to 1.34 and 0.056 mm, respectively. The results illustrate that the magnitude and nonuniform distribution of the slag layers and air gap along the cross direction, correlating with heat flux between the shell and mold, eventually determine the temperature profiles of the mold hot face and slab surface. The proposed model may provide a convenient approach for analyzing nonuniform heat transfer and mechanical behaviors between the mold and slab in the real casting process.

Slow Unlocking Processes Preceding the 2015 Mw 8.4 Illapel, Chile, Earthquake

NASA Astrophysics Data System (ADS)

Huang, Hui; Meng, Lingsen

2018-05-01

On 16 September 2015, the Mw 8.4 Illapel earthquake occurred in central Chile with no intense foreshock sequences documented in the regional earthquake catalog. Here we employ the matched-filter technique based on an enhanced template data set of previously catalogued events. We perform a continuous search over an 4-year period before the Illapel mainshock to recover the uncatalogued small events and repeating earthquakes. Repeating earthquakes are found both to the north and south of the mainshock rupture zone. To the south of the rupture zone, the seismicity and repeater-inferred aseismic slip progressively accelerate around the Illapel epicenter starting from 140 days before the mainshock. This may indicate an unlocking process involving the interplay of seismic and aseismic slip. The acceleration culminates in a M 5.3 event of low-angle thrust mechanism, which occurred 36 days before the Mw 8.4 mainshock. It is then followed by a relative quiescence in seismicity until the mainshock occurred. This quiescence might correspond to an intermediate period of stable slip before rupture initiation. In addition, to the north of the mainshock rupture area, the last aseismic-slip episode occurs within 175-95 days before the mainshock and accumulates the largest amount of slip in the observation period. The simultaneous occurrence of aseismic-slip transients over a large area is consistent with large-scale slow unlocking processes preceding the Illapel mainshock.

40 CFR 464.15 - Pretreatment standards for existing sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) EFFLUENT GUIDELINES AND STANDARDS METAL MOLDING AND CASTING POINT SOURCE CATEGORY Aluminum Casting... existing sources. (a) Casting Cleaning Operations. PSES Pollutant or pollutant property Maximum for any 1....0771 0.0421 Lead (T) 0.0791 0.039 Zinc (T) 0.114 0.0431 (b) Casting Quench Operation. PSES Pollutant or...

40 CFR 464.25 - Pretreatment standards for existing sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) EFFLUENT GUIDELINES AND STANDARDS METAL MOLDING AND CASTING POINT SOURCE CATEGORY Copper Casting... existing sources. (a) Casting Quench Operations. PSES Pollutant or pollutant property Maximum for any 1 day... monitoring) 1.2 0.399 (b) Direct Chill Casting Operations. PSES Pollutant or pollutant property Maximum for...

Interface Effects of the Properties and Processing of Graded Composite Aluminum Alloys

DTIC Science & Technology

2015-08-31

diffuse interface. Produced by the Alcoa sequential casting process, the material has a gradient in composition from a stronger, precipitation...strengthened alloy (7055) to a softer, strain-hardenable alloy (5456) [1], [2]. Alcoa donated material, 30x30x2 cm3 in volume. The material was cast, rolled

40 CFR 467.02 - General definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... subcategory, but when present is an integral part of the aluminum forming process. (c) Contact cooling water.... (d) Continuous casting is the production of sheet, rod, or other long shapes by solidifying the metal... pulling metal through a die or succession of dies to reduce the metal's diameter or alter its shape. There...

Evidence for a scale-limited low-frequency earthquake source process

NASA Astrophysics Data System (ADS)

Chestler, S. R.; Creager, K. C.

2017-04-01

We calculate the seismic moments for 34,264 low-frequency earthquakes (LFEs) beneath the Olympic Peninsula, Washington. LFE moments range from 1.4 × 1010 to 1.9 × 1012 N m (Mw = 0.7-2.1). While regular earthquakes follow a power law moment-frequency distribution with a b value near 1 (the number of events increases by a factor of 10 for each unit increase in Mw), we find that while for large LFEs the b value is 6, for small LFEs it is <1. The magnitude-frequency distribution for all LFEs is best fit by an exponential distribution with a mean seismic moment (characteristic moment) of 2.0 × 1011 N m. The moment-frequency distributions for each of the 43 LFE families, or spots on the plate interface where LFEs repeat, can also be fit by exponential distributions. An exponential moment-frequency distribution implies a scale-limited source process. We consider two end-member models where LFE moment is limited by (1) the amount of slip or (2) slip area. We favor the area-limited model. Based on the observed exponential distribution of LFE moment and geodetically observed total slip, we estimate that the total area that slips within an LFE family has a diameter of 300 m. Assuming an area-limited model, we estimate the slips, subpatch diameters, stress drops, and slip rates for LFEs during episodic tremor and slip events. We allow for LFEs to rupture smaller subpatches within the LFE family patch. Models with 1-10 subpatches produce slips of 0.1-1 mm, subpatch diameters of 80-275 m, and stress drops of 30-1000 kPa. While one subpatch is often assumed, we believe 3-10 subpatches are more likely.

The effect of high energy concentration source irradiation on structure and properties of Fe-based bulk metallic glass

NASA Astrophysics Data System (ADS)

Pilarczyk, Wirginia

2016-06-01

Metallic glasses exhibit metastable structure and maintain this relatively stable amorphous state within certain temperature range. High intensity laser beam was used for the surface irradiation of Fe-Co-B-Si-Nb bulk metallic glasses. The variable parameter was laser beam pulse energy. For the analysis of structure and properties of bulk metallic glasses and their surface after laser remelting the X-ray analysis, microscopic observation and test of mechanical properties were carried out. Examination of the nanostructure of amorphous materials obtained by high pressure copper mold casting method and the irradiated with the use of TITAN 80-300 HRTEM was carried out. Nanohardness and reduced Young's modulus of particular amorphous and amorphous-crystalline material zone of the laser beam were examined with the use of Hysitron TI950 Triboindenter nanoindenter and with the use of Berkovich's indenter. The XRD and microscopic analysis showed that the test material is amorphous in its structure before irradiation. Microstructure observation with electron transmission microscopy gave information about alloy crystallization in the irradiated process. Identification of given crystal phases allows to determine the kind of crystal phases created in the first place and also further changes of phase composition of alloy. The main value of the nanohardness of the surface prepared by laser beam has the order of magnitude similar to bulk metallic glasses formed by casting process irrespective of the laser beam energy used. Research results analysis showed that the area between parent material and fusion zone is characterized by extraordinarily interesting structure which is and will be the subject of further analysis in the scope of bulk metallic glasses amorphous structure and high energy concentration source. The main goal of this work is the results' presentation of structure and chosen properties of the selected bulk metallic glasses after casting process and after irradiation process employing the high energy concentration sources.

How does damage affect rupture propagation across a fault stepover?

NASA Astrophysics Data System (ADS)

Cooke, M. L.; Savage, H. M.

2011-12-01

We investigate the potential for fault damage to influence earthquake rupture at fault step-overs using a mechanical numerical model that explicitly includes the generation of cracks around faults. We compare the off-fault fracture patterns and slip profiles generated along faults with a variety of frictional slip-weakening distances and step-over geometry. Models with greater damage facilitate the transfer of slip to the second fault. Increasing separation and decreasing the overlap distance reduces the transfer of slip across the step over. This is consistent with observations of rupture stopping at step-over separation greater than 4 km (Wesnousky, 2006). In cases of slip transfer, rupture is often passed to the second fault before the damage zone cracks of the first fault reach the second fault. This implies that stresses from the damage fracture tips are transmitted elastically to the second fault to trigger the onset of slip along the second fault. Consequently, the growth of damage facilitates transfer of rupture from one fault to another across the step-over. In addition, the rupture propagates along the damage-producing fault faster than along the rougher fault that does not produce damage. While this result seems counter to our understanding that damage slows rupture propagation, which is documented in our models with pre-existing damage, these model results are suggesting an additional process. The slip along the newly created damage may unclamp portions of the fault ahead of the rupture and promote faster rupture. We simulate the M7.1 Hector Mine Earthquake and compare the generated fracture patterns to maps of surface damage. Because along with the detailed damage pattern, we also know the stress drop during the earthquake, we may begin to constrain parameters like the slip-weakening distance along portions of the faults that ruptured in the Hector Mine earthquake.

A Comparative Study of Hot Deformation Behaviors for Sand Casting and Centrifugal Casting Q235B Flange Blanks

NASA Astrophysics Data System (ADS)

Qin, Fangcheng; Li, Yongtang; Ju, Li

2017-03-01

Hot compression tests of sand casting and centrifugal casting Q235B flange blanks were performed at strain rate range of 0.01-5 s-1 and temperature range of 850-1,150 °C. The evolutions of microstructure and texture were revealed. The constitutive models based on Arrhenius constitutive modeling were proposed by considering the effects of strain on material constants. The results show that recrystallization in centrifugal casting Q235B is more apparent than that in sand casting, resulting in the finer grains and lower flow stress for centrifugal casting Q235B. The intensities of textures slightly weaken with the increase of temperature. At 1,050 °C and 5 s-1, the textures of sand casting are characterized by strong {001}<100> and {001}<110>, which are related with severe deformation, while the textures of centrifugal casting are composed of {110}<110> and {111}<112>, which are related with dynamic recovery and shear deformation. A good agreement between the predicted and experimental flow stress is achieved and demonstrates that the proposed constitutive models are reliable.

Fabrication of hierarchically structured superhydrophobic PDMS surfaces by Cu and CuO casting

NASA Astrophysics Data System (ADS)

Migliaccio, Christopher P.; Lazarus, Nathan

2015-10-01

Poly(dimethylsiloxane) (PDMS) films decorated with hierarchically structured pillars are cast from large area copper and copper oxide negative molds. The molds are fabricated using a single patterning step and electroplating. The process of casting structured PDMS films is simpler and cheaper than alternatives based on deep reactive ion etching or laser roughening of bulk silicone. Texture imparted to the pillars from the mold walls renders the PDMS films superhydrophobic, with the contact angle/hysteresis of the most non-wetting surfaces measuring 164°/9° and 158°/10° for surfaces with and without application of a low surface energy coating. The usefulness of patterned PDMS films as a "self-cleaning" solar cell module covering is demonstrated and other applications are discussed.

Application of Rapid Prototyping to the Investment Casting of Test Hardware (MSFC Center Director's Discretionary Fund Final Report, Project No. 98-08)

NASA Technical Reports Server (NTRS)

Cooper, K. G.; Wells, D.

2000-01-01

Investment casting masters of a selected propulsion hardware component, a fuel pump housing, were rapid prototyped on the several processes in-house, along with the new Z-Corp process acquired through this project. Also, tensile samples were prototyped and cast using the same significant parameters. The models were then shelled in-house using a commercial grade zircon-based slurry and stucco technique. Next, the shelled models were fired and cast by our in-house foundry contractor (IITRI), with NASA-23, a commonly used test hardware metal. The cast models are compared by their surface finish and overall appearance (i.e., the occurrence of pitting, warping, etc.), as well as dimensional accuracy.

40 CFR 464.40 - Applicability; description of the zinc casting subcategory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Applicability; description of the zinc... (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS METAL MOLDING AND CASTING POINT SOURCE CATEGORY Zinc Casting Subcategory § 464.40 Applicability; description of the zinc casting subcategory. The provisions of this...

40 CFR 464.26 - Pretreatment standards for new sources.

Code of Federal Regulations, 2010 CFR

2010-07-01

... GUIDELINES AND STANDARDS METAL MOLDING AND CASTING POINT SOURCE CATEGORY Copper Casting Subcategory § 464.26... and achieve the following pretreatment standards for new sources. (a) Casting Quench Operations. PSNS... 0.0335 0.0109 Oil and grease (for alternate monitoring) 1.2 0.399 (b) Direct Chill Casting...

Liquid Metal Infiltration Processing of Metallic Composites: A Critical Review

NASA Astrophysics Data System (ADS)

Sree Manu, K. M.; Ajay Raag, L.; Rajan, T. P. D.; Gupta, Manoj; Pai, B. C.

2016-10-01

Metal matrix composites (MMC) are one of the advanced materials widely used for aerospace, automotive, defense, and general engineering applications. MMC can be tailored to have superior properties such as enhanced high-temperature performance, high specific strength and stiffness, increased wear resistance, better thermal and mechanical fatigue, and creep resistance than those of unreinforced alloys. To fabricate such composites with ideal properties, the processing technique has to ensure high volume fraction of reinforcement incorporation, uniform distribution of the reinforcement, and acceptable adhesion between the matrix and the reinforcing phase without unwanted interfacial reactions which degrades the mechanical properties. A number of processing techniques such as stir casting/vortex method, powder metallurgy, infiltration, casting etc. have been developed to synthesize MMC employing a variety of alloy and the reinforcement's combinations. Among these, infiltration process is widely used for making MMC with high volume fraction of reinforcements and offers many more advantages compared to other conventional manufacturing processes. The present paper critically reviews the various infiltration techniques used for making the MMC, their process parameters, characteristics, and selected studies carried out worldwide and by authors on the development of metal ceramic composites by squeeze infiltration process.

Active faulting, earthquakes, and restraining bend development near Kerman city in southeastern Iran

NASA Astrophysics Data System (ADS)

Walker, Richard Thomas; Talebian, Morteza; Saiffori, Sohei; Sloan, Robert Alastair; Rasheedi, Ali; MacBean, Natasha; Ghassemi, Abbas

2010-08-01

We provide descriptions of strike-slip and reverse faulting, active within the late Quaternary, in the vicinity of Kerman city in southeastern Iran. The faults accommodate north-south, right-lateral, shear between central Iran and the Dasht-e-Lut depression. The regions that we describe have been subject to numerous earthquakes in the historical and instrumental periods, and many of the faults that are documented in this paper constitute hazards for local populations, including the city of Kerman itself (population ˜200,000). Faults to the north and east of Kerman are associated with the transfer of slip from the Gowk to the Kuh Banan right-lateral faults across a 40 km-wide restraining bend. Faults south and west of the city are associated with oblique slip on the Mahan and Jorjafk systems. The patterns of faulting observed along the Mahan-Jorjafk system, the Gowk-Kuh Banan system, and also the Rafsanjan-Rayen system further to the south, appear to preserve different stages in the development of these oblique-slip fault systems. We suggest that the faulting evolves through time. Topography is initially generated on oblique slip faults (as is seen on the Jorjafk fault). The shortening component then migrates to reverse faults situated away from the high topography whereas strike-slip continues to be accommodated in the high, mountainous, regions (as is seen, for example, on the Rafsanjan fault). The reverse faults may then link together and eventually evolve into new, through-going, strike-slip faults in a process that appears to be occurring, at present, in the bend between the Gowk and Kuh Banan faults.

Deformation modeling and constitutive modeling for anisotropic superalloys

NASA Technical Reports Server (NTRS)

Milligan, Walter W.; Antolovich, Stephen D.

1989-01-01

A study of deformation mechanisms in the single crystal superalloy PWA 1480 was conducted. Monotonic and cyclic tests were conducted from 20 to 1093 C. Both (001) and near-(123) crystals were tested, at strain rates of 0.5 and 50 percent/minute. The deformation behavior could be grouped into two temperature regimes: low temperatures, below 760 C; and high temperatures, above 820 to 950 C depending on the strain rate. At low temperatures, the mechanical behavior was very anisotropic. An orientation dependent CRSS, a tension-compression asymmetry, and anisotropic strain hardening were all observed. The material was deformed by planar octahedral slip. The anisotropic properties were correlated with the ease of cube cross-slip, as well as the number of active slip systems. At high temperatures, the material was isotropic, and deformed by homogeneous gamma by-pass. It was found that the temperature dependence of the formation of superlattice-intrinsic stacking faults was responsible for the local minimum in the CRSS of this alloy at 400 C. It was proposed that the cube cross-slip process must be reversible. This was used to explain the reversible tension-compression asymmetry, and was used to study models of cross-slip. As a result, the cross-slip model proposed by Paidar, Pope and Vitek was found to be consistent with the proposed slip reversibility. The results were related to anisotropic viscoplastic constitutive models. The model proposed by Walter and Jordan was found to be capable of modeling all aspects of the material anisotropy. Temperature and strain rate boundaries for the model were proposed, and guidelines for numerical experiments were proposed.

R-HPDC Process with Forced Convection Mixing Device for Automotive Part of A380 Aluminum Alloy

PubMed Central

Zhou, Bing; Kang, Yonglin; Qi, Mingfan; Zhang, Huanhuan; Zhu, Guoming

2014-01-01

The continuing quest for cost-effective and complex shaped aluminum castings with fewer defects for applications in the automotive industries has aroused the interest in rheological high pressure die casting (R-HPDC). A new machine, forced convection mixing (FCM) device, based on the mechanical stirring and convection mixing theory for the preparation of semisolid slurry in convenience and functionality was proposed to produce the automotive shock absorber part by R-HPDC process. The effect of barrel temperature and rotational speed of the device on the grain size and morphology of semi-solid slurry were extensively studied. In addition, flow behavior and temperature field of the melt in the FCM process was investigated combining computational fluid dynamics simulation. The results indicate that the microstructure and pore defects at different locations of R-HPDC casting have been greatly improved. The vigorous fluid convection in FCM process has changed the temperature field and composition distribution of conventional solidification. Appropriately increasing the rotational speed can lead to a uniform temperature filed sooner. The lower barrel temperature leads to a larger uniform degree of supercooling of the melt that benefits the promotion of nucleation rate. Both of them contribute to the decrease of the grain size and the roundness of grain morphology. PMID:28788608

High resolution shallow co-seismic and post-seismic slip from the 2016 central Italy earthquake sequence captured using terrestrial laser scanning, structure from motion and low-cost near-field GNSS

NASA Astrophysics Data System (ADS)

Wedmore, L. N. J.; Gregory, L. C.; McCaffrey, K. J. W.; Wilkinson, M.; Walters, R. J.

2017-12-01

Coseismic fault slip in the shallow crust is poorly constrained by many of the conventional tools used to record deformation during earthquakes. GNSS stations are often distributed too far from faults and radar images tend to decorrelate across earthquake surface ruptures. As a result, our understanding of near-field fault slip, shallow slip deficits, and off-fault deformation is limited. We present evidence from the 2016 central Italy earthquake sequence, during which we captured shallow coseismic and post-seismic slip using a combination of terrestrial laser scanning (TLS), structure-from-motion (SfM), and near-field low-cost GNSS recording at 1Hz. Three Mw>6 earthquakes on the 24th August, 26th and 30th October all involved slip on the Mt Vettore-Mt Bove fault system. We collected TLS and SfM point clouds across three separate segments of this system. Each segment experienced a different record of slip during the earthquake sequence; all three ruptured in the largest event (Mw 6.6. on October 30th) but two segments also ruptured during either the 24th August or the 26th October earthquakes. Following the Mw 6.6 earthquake, the faults were repeatedly surveyed using TLS, with the first scan collected c. 5 hours following the earthquake. This represents the first known instance where shallow co-seismic slip has been recorded by pre- and post-event terrestrial laser scanning. Displacement continuously measured across GNSS pairs at 1 Hz demonstrates that permanent near field displacement developed across the fault in the immediate seconds following the initiation of the rupture. However, a discrepancy between on-fault field measurements of surface displacement and the GNSS recorded displacement over 1km long baselines hints at a more complex rupture processes and the possibility of high slip gradients in the shallow subsurface. Displacement measured by differential TLS confirms the presence of these shallow slip deficits but suggests that shallow slip gradient may be controlled by the pattern and timing of slip in the preceding earthquakes. Postseismic afterslip captured by repeated TLS surveys hints at more complicated temporal evolution of nearfield afterslip than is currently predicted by logarithmic models for this process.

Precision Casting via Advanced Simulation and Manufacturing

NASA Technical Reports Server (NTRS)

1997-01-01

A two-year program was conducted to develop and commercially implement selected casting manufacturing technologies to enable significant reductions in the costs of castings, increase the complexity and dimensional accuracy of castings, and reduce the development times for delivery of high quality castings. The industry-led R&D project was cost shared with NASA's Aerospace Industry Technology Program (AITP). The Rocketdyne Division of Boeing North American, Inc. served as the team lead with participation from Lockheed Martin, Ford Motor Company, Howmet Corporation, PCC Airfoils, General Electric, UES, Inc., University of Alabama, Auburn University, Robinson, Inc., Aracor, and NASA-LeRC. The technical effort was organized into four distinct tasks. The accomplishments reported herein. Task 1.0 developed advanced simulation technology for core molding. Ford headed up this task. On this program, a specialized core machine was designed and built. Task 2.0 focused on intelligent process control for precision core molding. Howmet led this effort. The primary focus of these experimental efforts was to characterize the process parameters that have a strong impact on dimensional control issues of injection molded cores during their fabrication. Task 3.0 developed and applied rapid prototyping to produce near net shape castings. Rocketdyne was responsible for this task. CAD files were generated using reverse engineering, rapid prototype patterns were fabricated using SLS and SLA, and castings produced and evaluated. Task 4.0 was aimed at developing technology transfer. Rocketdyne coordinated this task. Casting related technology, explored and evaluated in the first three tasks of this program, was implemented into manufacturing processes.

40 CFR 467.02 - General definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... subcategory, but when present is an integral part of the aluminum forming process. (c) Contact cooling water.... (d) Continuous casting is the production of sheet, rod, or other long shapes by solidifying the metal... pulling metal through a die or succession of dies to reduce the metal's diameter or alter its shape. There...